JP7679638B2 - Variable magnification optical system, interchangeable lens, and imaging device - Google Patents

Description

The present invention relates to a variable magnification optical system, an interchangeable lens, and an imaging device.

In variable magnification optical systems, a focusing method is already known in which multiple focusing lens groups are moved independently in the optical axis direction to perform focusing from an object at infinity to an object at a close distance.

For example, Patent Document 1 describes a zoom lens that has multiple lens groups and an aperture stop, and changes the spacing between the multiple lens groups to change the magnification from the wide-angle end state to the telephoto end state. The zoom lens has, in order from the object side, a first lens group with positive refractive power, a second lens group with negative refractive power, and a third lens group. The second lens group and at least one lens group located closer to the image than the second lens group are focusing lens groups, and at least one of the focusing lens groups is moved depending on the focal length state from the wide-angle end state to the telephoto end state to focus from a distant object to a close object.

JP 2007-93974 A

However, in the prior art including Patent Document 1, there is room for improvement in the arrangement of the multiple focusing lens groups within the optical system and the distribution of refractive powers of the multiple focusing lens groups.

The present invention has been made in consideration of the above points, and aims to provide a variable power optical system, an interchangeable lens, and an imaging device that realizes good optical performance by appropriately arranging multiple focusing lens groups within the optical system and distributing their refractive powers.

In a first aspect , the variable magnification optical system of this embodiment is composed of, in order from the object side, an object-side lens group, an aperture stop, and an image-side lens group. The object-side lens group has, in order from the object side, an object-side first lens group and an object-side second lens group. The image-side lens group is composed, in order from the object side, of an image-side first lens group having positive refractive power, an image-side intermediate lens group, and an image-side final lens group. When varying magnification from the short focal length end to the long focal length end, the interval between adjacent lens groups changes, and at least one of the object-side second lens group is changed. the portion has an object-side focusing lens group that moves in the optical axis direction when focusing from infinity to a close distance, at least a part of the image-side intermediate lens group has an image-side focusing lens group that moves in the optical axis direction when focusing from infinity to a close distance, the object-side focusing lens group and the image-side focusing lens group move in the optical axis direction along different trajectories when focusing from infinity to a close distance, and when the object-side focusing lens group is the first focusing lens group and the image-side focusing lens group is the second focusing lens group, the following conditional expressions (1) and (2) are satisfied .
(1) 1.170≦｜f1/f2｜<10
(2) 3.0<|p2T/p1T|<20
however,
f1: focal length of the first focusing lens group,
f2: focal length of the second focusing lens group,
p1T: focus sensitivity of the first focusing lens group when focusing on infinity at the long focal length end,
p2T: focus sensitivity of the second focusing lens group when focusing on infinity at the long focal length end,
p1T=(1-m1T^2)×m1RT^2
p2T=(1-m2T^2)×m2RT^2
m1T: paraxial lateral magnification of the first focusing lens group when focusing on infinity at the long focal length end,
m1RT: paraxial lateral magnification of the optical system on the image side of the first focusing lens group when focusing on infinity at the long focal length end,
m2T: paraxial lateral magnification of the second focusing lens group when focusing on infinity at the long focal length end,
m2RT: the paraxial lateral magnification of the optical system on the image side of the second focusing lens group when focusing on infinity at the long focal length end.
In the second aspect, the variable magnification optical system of this embodiment is composed of, in order from the object side, an object-side lens group, an aperture stop, and an image-side lens group. The object-side lens group has, in order from the object side, an object-side first lens group and an object-side second lens group. The image-side lens group is composed, in order from the object side, of an image-side first lens group having positive refractive power, an image-side intermediate lens group, and an image-side final lens group. When varying magnification from the short focal length end to the long focal length end, the interval between adjacent lens groups changes, and at least a part of the object-side second lens group changes. has an object-side focusing lens group that moves in the optical axis direction when focusing from infinity to a close distance, at least a part of the image-side intermediate lens group has an image-side focusing lens group that moves in the optical axis direction when focusing from infinity to a close distance, the object-side focusing lens group and the image-side focusing lens group move in the optical axis direction along different loci from each other when focusing from infinity to a close distance, and when the object-side focusing lens group is the first focusing lens group and the image-side focusing lens group is the second focusing lens group, the following conditional expressions (1') and (2') are satisfied.
(1') 1.0<|f1/f2|<10
(2') 0.03<|p2T/p1T|≦0.250
however,
f1: focal length of the first focusing lens group,
f2: focal length of the second focusing lens group,
p1T: focus sensitivity of the first focusing lens group when focusing on infinity at the long focal length end,
p2T: focus sensitivity of the second focusing lens group when focusing on infinity at the long focal length end,
p1T=(1-m1T^2)×m1RT^2
p2T=(1-m2T^2)×m2RT^2
m1T: paraxial lateral magnification of the first focusing lens group when focusing on infinity at the long focal length end,
m1RT: paraxial lateral magnification of the optical system on the image side of the first focusing lens group when focusing on infinity at the long focal length end,
m2T: paraxial lateral magnification of the second focusing lens group when focusing on infinity at the long focal length end,
m2RT: the paraxial lateral magnification of the optical system on the image side of the second focusing lens group when focusing on infinity at the long focal length end.
In the third aspect, the variable magnification optical system of this embodiment is composed of, in order from the object side, an object-side lens group, an aperture stop, and an image-side lens group. The object-side lens group has, in order from the object side, an object-side first lens group and an object-side second lens group. The image-side lens group is composed, in order from the object side, of an image-side first lens group having positive refractive power, an image-side intermediate lens group, and an image-side final lens group. When varying magnification from the short focal length end to the long focal length end, the spacing between adjacent lens groups changes, and at least a portion of the object-side second lens group changes when focusing from infinity to a close distance. the object-side focusing lens group has an object-side focusing lens group that moves in the optical axis direction when focusing from infinity to a close distance, at least a part of the image-side intermediate lens group has an image-side focusing lens group that moves in the optical axis direction when focusing from infinity to a close distance, the object-side focusing lens group and the image-side focusing lens group move in the optical axis direction along different loci from each other when focusing from infinity to a close distance, and when, of the object-side focusing lens group and the image-side focusing lens group, the one having the greater absolute value of refractive power is designated as a first focusing lens group and the one having the smaller absolute value of refractive power is designated as a second focusing lens group, the following conditional expressions (1A) and (2A) are satisfied.
(1A) 0.618≦｜f1/f2｜<1
(2A) 4.072≦｜p2T/p1T｜<30
however,
f1: focal length of the first focusing lens group,
f2: focal length of the second focusing lens group,
p1T: focus sensitivity of the first focusing lens group when focusing on infinity at the long focal length end,
p2T: focus sensitivity of the second focusing lens group when focusing on infinity at the long focal length end,
p1T=(1-m1T^2)×m1RT^2
p2T=(1-m2T^2)×m2RT^2
m1T: paraxial lateral magnification of the first focusing lens group when focusing on infinity at the long focal length end,
m1RT: paraxial lateral magnification of the optical system on the image side of the first focusing lens group when focusing on infinity at the long focal length end,
m2T: paraxial lateral magnification of the second focusing lens group when focusing on infinity at the long focal length end,
m2RT: the paraxial lateral magnification of the optical system on the image side of the second focusing lens group when focusing on infinity at the long focal length end.

The present invention provides a variable power optical system, an interchangeable lens, and an imaging device that achieve good optical performance by appropriately arranging multiple focusing lens groups within the optical system and distributing their refractive powers.

FIG. 2 is a diagram showing a schematic image of a lens configuration of a variable magnification optical system according to the present embodiment. 1 is a diagram showing a schematic image of off-axis light passing through a variable magnification optical system according to the present embodiment. 11 is a diagram showing a magnification change movement locus of the variable magnification optical system of Numerical Example 1. FIG. 13 is a diagram showing a magnification change movement locus of a variable magnification optical system according to Numerical Example 2. FIG. 13 is a diagram showing a magnification change movement locus of a variable magnification optical system according to Numerical Example 3. FIG. 13 is a diagram showing a magnification change movement locus of a variable magnification optical system according to Numerical Example 4. FIG. 13 is a diagram showing a magnification change movement locus of a variable magnification optical system according to Numerical Example 5. FIG. 13 is a diagram showing a magnification change movement locus of a variable magnification optical system according to Numerical Example 6. FIG. 13 is a diagram showing a magnification change movement locus of a variable magnification optical system of Comparative Example 7. FIG . 13 is a diagram showing a magnification change movement locus of a variable magnification optical system of Comparative Example 8. FIG . 13 is a diagram showing a magnification change movement locus of a variable magnification optical system according to Numerical Example 9. FIG. 13 is a diagram showing a magnification change movement locus of the variable magnification optical system of Numerical Example 10. FIG. 13 is a diagram showing a magnification change movement locus of a variable magnification optical system in Numerical Example 11. FIG. 1 is a diagram showing a lens configuration of a variable magnification optical system of Numerical Example 1 at the short focal length extremity when focusing on infinity. 1 is a diagram showing a lens configuration of a variable magnification optical system of Numerical Example 1 at the long focal length extremity when focusing on infinity. FIG. 11A to 11C are longitudinal aberration diagrams of the variable magnification optical system of Numerical Example 1 at the short focal length extremity when focused on an object at infinity. 6A to 6C are lateral aberration diagrams of the variable magnification optical system of Numerical Example 1 at the short focal length extremity when focused on an object at infinity. 11A to 11C are longitudinal aberration diagrams of the variable magnification optical system of Numerical Example 1 at the long focal length extremity when focused on an object at infinity. 6A to 6C are diagrams illustrating lateral aberrations at the long focal length extremity of the variable magnification optical system of Numerical Example 1 when focused on an object at infinity. 11A to 11C are longitudinal aberration diagrams of the variable magnification optical system of Numerical Example 1 at the short focal length extremity when focusing on a close distance. 6A to 6C are diagrams illustrating lateral aberrations at the short focal length extremity of the variable magnification optical system of Numerical Example 1 when focusing on a close distance. 11A and 11B are longitudinal aberration diagrams of the variable magnification optical system of Numerical Example 1 at the long focal length extremity when focusing on a close distance. 6A to 6C are diagrams illustrating lateral aberrations at the long focal length extremity of the variable magnification optical system of Numerical Example 1 when focusing on a close distance. 13 is a diagram showing a lens configuration of a variable magnification optical system of Numerical Example 2 at the short focal length extremity when focusing on infinity. FIG. FIG. 13 is a diagram showing a lens configuration of a variable magnification optical system of Numerical Example 2 at the long focal length extremity when focusing on infinity. 11A to 11C are longitudinal aberration diagrams of the variable magnification optical system of Numerical Example 2 at the short focal length extremity when focused on an object at infinity. 11A to 11C are lateral aberration diagrams of the variable magnification optical system of Numerical Example 2 at the short focal length extremity when focused on an object at infinity. 13A to 13C are longitudinal aberration diagrams of the variable magnification optical system of Numerical Example 2 at the long focal length extremity when focused on an object at infinity. 11A to 11C are lateral aberration diagrams of the variable magnification optical system of Numerical Example 2 at the long focal length extremity when focused on an object at infinity. 13A to 13C are longitudinal aberration diagrams of the variable magnification optical system of Numerical Example 2 at the short focal length extremity when focusing on a close distance. 13A to 13C are diagrams illustrating lateral aberrations at the short focal length extremity of the variable magnification optical system of Numerical Example 2 when focusing on a close distance. 13A to 13C are longitudinal aberration diagrams of the variable magnification optical system of Numerical Example 2 at the long focal length extremity when focusing on a close distance. 13A to 13C are diagrams illustrating lateral aberrations at the long focal length extremity of the variable magnification optical system of Numerical Example 2 when focusing on a close distance. FIG. 13 is a diagram showing a lens configuration of a variable magnification optical system of Numerical Example 3 at the short focal length extremity when focusing on infinity. FIG. 13 is a diagram showing a lens configuration of a variable magnification optical system according to Numerical Example 3 at the long focal length extremity when focusing on infinity. 13A to 13C are longitudinal aberration diagrams of the variable magnification optical system of Numerical Example 3 when focused on an object at infinity at the short focal length extremity. 13A to 13C are lateral aberration diagrams of the variable magnification optical system of Numerical Example 3 when focused on infinity at the short focal length extremity. 13A to 13C are longitudinal aberration diagrams of the variable magnification optical system of Numerical Example 3 at the long focal length extremity when focused on an object at infinity. 13A to 13C are lateral aberration diagrams of the variable magnification optical system of Numerical Example 3 when focused on infinity at the long focal length extremity. 13A to 13C are longitudinal aberration diagrams of the variable magnification optical system of Numerical Example 3 at the short focal length extremity when focusing on a close distance. 13A to 13C are lateral aberration diagrams of the variable magnification optical system of Numerical Example 3 at the short focal length extremity when focusing on a close distance. 13A to 13C are longitudinal aberration diagrams of the variable magnification optical system of Numerical Example 3 at the long focal length extremity when focusing on a close object. 13A to 13C are diagrams illustrating lateral aberrations at the long focal length extremity of the variable magnification optical system of Numerical Example 3 when focusing on a close distance. FIG. 13 is a diagram showing a lens configuration of a variable magnification optical system of Numerical Example 4 at the short focal length extremity when focusing on infinity. FIG. 13 is a diagram showing a lens configuration of a variable magnification optical system according to Numerical Example 4 at the long focal length end when focusing on infinity. 13A to 13C are longitudinal aberration diagrams of the variable magnification optical system of Numerical Example 4 when focused on infinity at the short focal length extremity. 13A to 13C are lateral aberration diagrams of the variable magnification optical system of Numerical Example 4 when focused on infinity at the short focal length extremity. 13A to 13C are longitudinal aberration diagrams of the variable magnification optical system of Numerical Example 4 at the long focal length extremity when focused on an object at infinity. 13A to 13C are lateral aberration diagrams of the variable magnification optical system of Numerical Example 4 at the long focal length extremity when focused on an object at infinity. 13A to 13C are longitudinal aberration diagrams of the variable magnification optical system of Numerical Example 4 at the short focal length extremity when focusing on a close distance. 13A to 13C are diagrams illustrating lateral aberrations at the short focal length extremity of the variable magnification optical system of Numerical Example 4 when focusing on a close distance. 13A to 13C are longitudinal aberration diagrams of the variable magnification optical system of Numerical Example 4 at the long focal length extremity when focusing on a close object. 13A to 13C are diagrams illustrating lateral aberrations at the long focal length extremity of the variable magnification optical system of Numerical Example 4 when focusing on a close distance. FIG. 13 is a diagram showing a lens configuration of a variable magnification optical system of Numerical Example 5 at the short focal length extremity when focusing on infinity. FIG. 13 is a diagram showing a lens configuration of a variable magnification optical system of Numerical Example 5 at the long focal length extremity when focusing on infinity. 13A to 13C are longitudinal aberration diagrams of the variable magnification optical system of Numerical Example 5 when focused on infinity at the short focal length extremity. 13A to 13C are lateral aberration diagrams of the variable magnification optical system of Numerical Example 5 when focused on infinity at the short focal length extremity. 13A to 13C are longitudinal aberration diagrams of the variable magnification optical system of Numerical Example 5 at the long focal length extremity when focused on an object at infinity. 13A to 13C are lateral aberration diagrams of the variable magnification optical system of Numerical Example 5 when focused on infinity at the long focal length extremity. 13A to 13C are longitudinal aberration diagrams of the variable magnification optical system of Numerical Example 5 at the short focal length extremity when focusing on a close object. 13A to 13C are diagrams illustrating lateral aberrations at the short focal length extremity of the variable magnification optical system of Numerical Example 5 when focusing on a close distance. 13A to 13C are longitudinal aberration diagrams of the variable magnification optical system of Numerical Example 5 at the long focal length extremity when focusing on a close object. 13A to 13C are diagrams illustrating lateral aberrations at the long focal length extremity of the variable magnification optical system of Numerical Example 5 when focusing on a close distance. FIG. 13 is a diagram showing a lens configuration of a variable magnification optical system of Numerical Example 6 at the short focal length extremity when focusing on infinity. FIG. 13 is a diagram showing a lens configuration of a variable magnification optical system of Numerical Example 6 at the long focal length extremity when focusing on infinity. 13A to 13C are longitudinal aberration diagrams of the variable magnification optical system of Numerical Example 6 when focused on infinity at the short focal length extremity. 13A to 13C are lateral aberration diagrams of the variable magnification optical system of Numerical Example 6 when focused on infinity at the short focal length extremity. 13A to 13C are longitudinal aberration diagrams of the variable magnification optical system of Numerical Example 6 when focused on infinity at the long focal length extremity. 13A to 13C are lateral aberration diagrams of the variable magnification optical system of Numerical Example 6 when focused on infinity at the long focal length extremity. 13A to 13C are longitudinal aberration diagrams of the variable magnification optical system of Numerical Example 6 at the short focal length extremity when focusing on a close distance. 13A to 13C are diagrams illustrating lateral aberrations at the short focal length extremity of the variable magnification optical system of Numerical Example 6 when focusing on a close distance. 13A to 13C are longitudinal aberration diagrams of the variable magnification optical system of Numerical Example 6 at the long focal length extremity when focusing on a close distance. 13A to 13C are diagrams illustrating lateral aberrations at the long focal length extremity of the variable magnification optical system of Numerical Example 6 when focusing on a close distance. FIG. 13 is a diagram showing the lens configuration of a variable magnification optical system of Comparative Example 7 when focused on infinity at the short focal length extremity. FIG. 13 is a diagram showing the lens configuration of a variable magnification optical system of Comparative Example 7 at the long focal length end when focused on infinity. 13 is a longitudinal aberration diagram of the variable magnification optical system of Comparative Example 7 when focused on infinity at the short focal length extremity. FIG. 13 is a lateral aberration diagram of the variable magnification optical system of Comparative Example 7 when focused on infinity at the short focal length extremity. FIG. 13 is a longitudinal aberration diagram of the variable magnification optical system of Comparative Example 7 at the long focal length extremity when focused on an object at infinity. FIG. 13 is a lateral aberration diagram of the variable magnification optical system of Comparative Example 7 at the long focal length extremity when focused on an object at infinity. FIG. 13 is a longitudinal aberration diagram of the variable magnification optical system of Comparative Example 7 at the short focal length extremity when focusing on a close object. FIG. 13 is a lateral aberration diagram of the variable magnification optical system of Comparative Example 7 at the short focal length extremity when focusing on a close object. FIG. 13 is a longitudinal aberration diagram of the variable magnification optical system of Comparative Example 7 at the long focal length extremity when focusing on a close object. FIG. 13 is a lateral aberration diagram of the variable magnification optical system of Comparative Example 7 at the long focal length extremity when focusing on a close object. FIG. FIG. 13 is a diagram showing the lens configuration of a variable magnification optical system of Comparative Example 8 when focused on infinity at the short focal length extremity. FIG. 13 is a diagram showing the lens configuration of a variable magnification optical system of Comparative Example 8 at the long focal length end when focusing on infinity. 13 is a longitudinal aberration diagram of the variable magnification optical system of Comparative Example 8 when focused on infinity at the short focal length extremity. FIG. 13 is a lateral aberration diagram of the variable magnification optical system of Comparative Example 8 when focused on infinity at the short focal length extremity. FIG. 13 is a longitudinal aberration diagram of the variable magnification optical system of Comparative Example 8 at the long focal length extremity when focused on an object at infinity. FIG. 13 is a lateral aberration diagram of the variable magnification optical system of Comparative Example 8 at the long focal length extremity when focused on an object at infinity. FIG. 13 is a longitudinal aberration diagram of the variable magnification optical system of Comparative Example 8 at the short focal length extremity when focusing on a close object. FIG. 13 is a lateral aberration diagram of the variable magnification optical system of Comparative Example 8 at the short focal length extremity when focusing on a close object. FIG. 13 is a longitudinal aberration diagram of the variable magnification optical system of Comparative Example 8 at the long focal length extremity when focusing on a close object. FIG. 13 is a lateral aberration diagram of the variable magnification optical system of Comparative Example 8 at the long focal length extremity when focusing on a close object. FIG. FIG. 13 is a diagram showing a lens configuration of a variable magnification optical system of Numerical Example 9 at the short focal length extremity when focusing on infinity. FIG. 13 is a diagram showing a lens configuration of a variable magnification optical system of Numerical Example 9 at the long focal length extremity when focusing on infinity. 13A to 13C are longitudinal aberration diagrams of the variable magnification optical system of Numerical Example 9 when focused on infinity at the short focal length extremity. 13A to 13C are lateral aberration diagrams of the variable magnification optical system of Numerical Example 9 when focused on infinity at the short focal length extremity. 13A to 13C are longitudinal aberration diagrams of the variable magnification optical system of Numerical Example 9 at the long focal length extremity when focused on an object at infinity. 13A to 13C are lateral aberration diagrams of the variable magnification optical system of Numerical Example 9 at the long focal length extremity when focused on an object at infinity. 13A to 13C are longitudinal aberration diagrams of the variable magnification optical system of Numerical Example 9 at the short focal length extremity when focusing on a close distance. 13A to 13C are lateral aberration diagrams of the variable magnification optical system of Numerical Example 9 at the short focal length extremity when focusing on a close object. 13A to 13C are longitudinal aberration diagrams of the variable magnification optical system of Numerical Example 9 at the long focal length extremity when focusing on a close object. 13A to 13C are lateral aberration diagrams of the variable magnification optical system of Numerical Example 9 at the long focal length extremity when focusing on a close distance. FIG. 23 is a diagram showing the lens configuration of the variable magnification optical system of Numerical Example 10 at the short focal length extremity when focusing on infinity. FIG. 13 is a diagram showing a lens configuration of a variable magnification optical system of Numerical Example 10 at the long focal length end when focusing on infinity. 13A to 13C are longitudinal aberration diagrams of the variable magnification optical system of Numerical Example 10 at the short focal length extremity when focused on an object at infinity. 13A to 13C are lateral aberration diagrams of the variable magnification optical system of Numerical Example 10 at the short focal length extremity when focused on an object at infinity. 13A to 13C are longitudinal aberration diagrams of the variable magnification optical system of Numerical Example 10 at the long focal length extremity when focused on an object at infinity. 13A to 13C are lateral aberration diagrams of the variable magnification optical system of Numerical Example 10 at the long focal length extremity when focused on an object at infinity. 13A to 13C are longitudinal aberration diagrams of the variable magnification optical system of Numerical Example 10 at the short focal length extremity when focusing on a close object. 13A to 13C are diagrams illustrating lateral aberrations of the variable magnification optical system of Numerical Example 10 at the short focal length extremity when focusing on a close distance. 13A to 13C are longitudinal aberration diagrams of the variable magnification optical system of Numerical Example 10 at the long focal length extremity when focusing on a close object. 13A to 13C are diagrams illustrating lateral aberrations at the long focal length extremity of the variable magnification optical system of Numerical Example 10 when focusing on a close distance. FIG. 13 is a diagram showing the lens configuration of the variable magnification optical system of Numerical Example 11 at the short focal length extremity when focusing on infinity. FIG. 13 is a diagram showing the lens configuration of the variable magnification optical system of Numerical Example 11 at the long focal length extremity when focusing on infinity. 13A to 13C are longitudinal aberration diagrams of the variable magnification optical system of Numerical Example 11 at the short focal length extremity when focused on an object at infinity. 13A to 13C are lateral aberration diagrams of the variable magnification optical system of Numerical Example 11 at the short focal length extremity when focused on an object at infinity. 13A to 13C are longitudinal aberration diagrams of the variable magnification optical system of Numerical Example 11 at the long focal length extremity when focused on an object at infinity. 13A to 13C are lateral aberration diagrams of the variable magnification optical system of Numerical Example 11 at the long focal length extremity when focused on an object at infinity. 13A to 13C are longitudinal aberration diagrams of the variable magnification optical system of Numerical Example 11 at the short focal length extremity when focusing on a close object. 13A to 13C are lateral aberration diagrams of the variable magnification optical system of Numerical Example 11 at the short focal length extremity when focusing on a close distance. 13A to 13C are longitudinal aberration diagrams of the variable magnification optical system of Numerical Example 11 at the long focal length extremity when focusing on a close object. 13A to 13C are diagrams illustrating lateral aberrations at the long focal length extremity of the variable magnification optical system of Numerical Example 11 when focusing on a close distance. 1 is a first diagram showing an example of an imaging apparatus equipped with a variable magnification optical system according to an embodiment of the present invention. FIG. 2 is a second diagram showing an example of an imaging apparatus equipped with the variable magnification optical system of the present embodiment. FIG. 1 is an external perspective view showing an example of an interchangeable lens of the present embodiment.

The variable magnification optical system of this embodiment is suitable as an interchangeable lens for use in an interchangeable lens imaging device such as a digital single-lens reflex camera or digital single-lens camera.

Figure 1 shows an overview of the lens configuration of the variable magnification optical system of this embodiment.

As shown in Fig. 1, the variable magnification optical system of this embodiment is composed of, in order from the object side, an object side lens group G _ob , an aperture stop AST, and an image side lens group G _im . The object side lens group G _ob has, in order from the object side, an object side first lens group G _ob1 having a positive or negative refractive power, and an object side second lens group G _ob2 having a positive or negative refractive power. The image side lens group G _im is composed, in order from the object side, of an image side first lens group G _im1 having a positive refractive power, an image side intermediate lens group G _im2 , and an image side final lens group G _L.

When changing magnification from the short focal length end to the long focal length end, the distance between the object side first lens group G _ob1 and the object side second lens group G _ob2 , the distance between the object side second lens group G _ob2 and the aperture stop AST, the distance between the image side first lens group G _im1 and the image side intermediate lens group G _im2 , and the distance between the image side intermediate lens group G _im2 and the image side final lens group G _L change. The white arrows in Fig. 1 indicate that the air spacing changes during magnification.

At least a part of the object side lens group G _ob , particularly the object side second lens group G _ob2 , has an object side focusing lens group FL _ob that moves in the optical axis direction when focusing from infinity to a close distance. At least a part of the image side lens group G _im , particularly the image side intermediate lens group G _im2 , has an image side focusing lens group FL _im that moves in the optical axis direction when focusing from infinity to a close distance. The object side focusing lens group FL _ob and the image side focusing lens group FL _im move in the optical axis direction on different trajectories when focusing from infinity to a close distance. The black arrow in FIG. 1 indicates the movement in the optical axis direction when focusing from infinity to a close distance.

Figure 2 shows a schematic image of off-axis light passing through the variable magnification optical system of this embodiment.

2 shows an outline of the optical path of an off-axis chief ray Rp incident on a variable magnification optical system. The off-axis chief ray Rp passes through the object-side first lens group G _ob1 and the object-side second lens group G _ob2 of the object-side lens group G _ob , the aperture stop AST, and the image-side first lens group G _im1 , the image-side intermediate lens group G _{im2 ,} and the image-side final lens group G _L of the image-side lens group G im to be guided to an image surface IM, where an object image is formed.

3 to 13 are diagrams showing the movement loci of the variable magnification optical systems of Numerical Examples 1 to 6, 9 to 11 and Comparative Examples (Reference Examples) 7 and 8. In Fig. 3 to 13, the arrows of thin solid lines are the movement loci of each lens group when the magnification is changed from the short focal length end to the long focal length end when focusing at infinity, and the arrows of thin dashed lines are the movement loci of each lens group when the magnification is changed from the short focal length end to the long focal length end when focusing at a close distance. In addition, the arrows of thick solid lines are the movement loci of the object side focusing lens group FL _ob and the image side focusing lens group FL _im when focusing from infinity to a close distance at the short focal length end, and the arrows of thick dashed lines are the movement loci of the object side focusing lens group FL _ob and the image side focusing lens group FL _im when focusing from infinity to a close distance at the long focal length end. AST is an aperture stop. IM is the image plane where the silver halide film or the image sensor is placed. CG is various optical elements such as an infrared cut filter and a cover glass that have practically no refractive power, and can be added or removed as desired in the configuration of the device. The sign of the refractive power of the lens group is expressed as (+) if it is positive and (-) if it is negative.

As shown in Figures 3 to 8, the variable magnification optical systems of Numerical Examples 1 to 6 are composed of, in order from the object side, a first lens group G1 with positive refractive power, a second lens group G2 with negative refractive power, a third lens group G3 with negative refractive power, an aperture stop AST, a fourth lens group G4 with positive refractive power, a fifth lens group G5 with negative refractive power, and a sixth lens group G6 with positive refractive power. A cover glass CG is disposed between the sixth lens group G6 and the image surface IM.

The first lens group G1, the second lens group G2, and the third lens group G3 constitute an object-side lens group G _ob . The first lens group G1 constitutes an object-side first lens group G _ob1 , and the second lens group G2 and the third lens group G3 constitute an object-side second lens group G _ob2 .

The fourth lens group G4, the fifth lens group G5, and the sixth lens group G6 constitute an image side lens group G _im . The fourth lens group G4 constitutes an image side first lens group G _im1 having a positive refractive power, the fifth lens group G5 constitutes an image side intermediate lens group G _im2 , and the sixth lens group G6 constitutes an image side final lens group G _L.

The third lens group G3, which is at least a part of the object-side second lens group G _ob2 , constitutes an object-side focusing lens group FL _ob that moves in the optical axis direction when focusing from infinity to a close distance. The fifth lens group G5, which is at least a part of the image-side intermediate lens group G _im2 , constitutes an image-side focusing lens group FL _im that moves in the optical axis direction when focusing from infinity to a close distance.

When changing magnification from the short focal length end to the long focal length end, the distance between adjacent lens groups changes. Specifically, when changing magnification from the short focal length end to the long focal length end, the air distance between the first lens group G1 and the second lens group G2 increases, the air distance between the second lens group G2 and the third lens group G3 changes, the air distance between the third lens group G3 and the fourth lens group G4 decreases, the air distance between the fourth lens group G4 and the fifth lens group G5 increases, the air distance between the fifth lens group G5 and the sixth lens group G6 decreases, and the air distance between the sixth lens group G6 and the image plane IM increases. The aperture stop AST is placed between the third lens group G3 and the fourth lens group G4, and can be moved on the same trajectory as the fourth lens group G4 during magnification. Alternatively, the aperture stop AST can be moved on a trajectory separate from that of the fourth lens group G4 during magnification.

When focusing from infinity to a close distance, the movement loci of the third lens group G3 (object side focusing lens group FL _ob ) and the fifth lens group G5 (image side focusing lens group FL _im ) are different from each other. When focusing from infinity to a close distance, the third lens group G3 (object side focusing lens group FL _ob ) moves in the optical axis direction, preferably toward the object side. When focusing from infinity to a close distance, the fifth lens group G5 (image side focusing lens group FL _im ) moves in the optical axis direction. When focusing from infinity to a close distance, it is preferable that at the short focal length end, the fifth lens group G5 (image side focusing lens group FL _im ) moves toward the object side or image side, and at the long focal length end, the fifth lens group G5 (image side focusing lens group FL _im ) moves toward the object side.

The second lens group G2 and the third lens group G3, i.e., the entire object-side second lens group G _ob2, may be the object-side focusing lens group FL _ob . In that case, when focusing from infinity to a close distance, the air distance between the second lens group G2 and the third lens group G3 may be constant, or the air distance between the second lens group G2 and the third lens group G3 may be changed depending on the object distance.

As shown in Fig. 9, the variable power optical system of the comparative example (reference example) 7 is composed of, in order from the object side, a first lens group G1 with positive refractive power, a second lens group G2 with negative refractive power, a third lens group G3 with positive refractive power, a fourth lens group G4 with negative refractive power, and a fifth lens group G5 with positive refractive power. The third lens group G3 is composed of, in order from the object side, a third A lens group G3A with positive refractive power, an aperture stop AST, and a third B lens group G3B with positive refractive power. A cover glass CG is disposed between the fifth lens group G5 and the image surface IM.

The first lens group G1, the second lens group G2, and the third lens group G3A constitute an object-side lens group G _ob . The first lens group G1 constitutes an object-side first lens group G _ob1 , and the second lens group G2 constitutes an object-side second lens group G _ob2 .

The 3B lens group G3B, the 4th lens group G4, and the 5th lens group G5 constitute an image side lens group G _im . The 3B lens group G3B constitutes an image side first lens group G _im1 having a positive refractive power, the 4th lens group G4 constitutes an image side intermediate lens group G _im2 , and the 5th lens group G5 constitutes an image side final lens group G _L.

The second lens group G2, which is at least a part of the object-side second lens group G _ob2 , constitutes an object-side focusing lens group FL _ob that moves in the optical axis direction when focusing from infinity to a close distance. The fourth lens group G4, which is at least a part of the image-side intermediate lens group G _im2 , constitutes an image-side focusing lens group FL _im that moves in the optical axis direction when focusing from infinity to a close distance.

When changing magnification from the short focal length end to the long focal length end, the distance between adjacent lens groups changes. Specifically, when changing magnification from the short focal length end to the long focal length end, the air distance between the first lens group G1 and the second lens group G2 increases, the air distance between the second lens group G2 and the third lens group G3 decreases, the air distance between the third lens group G3 and the fourth lens group G4 increases, the air distance between the fourth lens group G4 and the fifth lens group G5 decreases, and the air distance between the fifth lens group G5 and the image plane IM changes. One or both of the first lens group G1 and the fifth lens group G5 may be fixed with respect to the image plane IM when changing magnification from the short focal length end to the long focal length end.

When focusing from infinity to a close distance, the movement loci of the second lens group G2 (object side focusing lens group FL _ob ) and the fourth lens group G4 (image side focusing lens group FL _im ) are different from each other. When focusing from infinity to a close distance, the second lens group G2 (object side focusing lens group FL _ob ) moves in the optical axis direction. When focusing from infinity to a close distance, it is preferable that at the short focal length end, the second lens group G2 (object side focusing lens group FL _ob ) moves to the object side or image side, and at the long focal length end, the second lens group G2 (object side focusing lens group FL _ob ) moves to the object side. In addition, the movement direction of the second lens group G2 (object side focusing lens group FL _ob ) at the short focal length end may be changed depending on the object distance. When focusing from infinity to a close distance, the fourth lens group G4 (image side focusing lens group FL _im ) moves in the optical axis direction. When focusing from infinity to a close distance, it is preferable that at the short focal length extremity, the fourth lens group G4 (image side focusing lens group FL _im ) moves to the object side or image side, and at the long focal length extremity, the fourth lens group G4 (image side focusing lens group FL _im ) moves to the object side. Furthermore, the movement direction of the fourth lens group G4 (image side focusing lens group FL _im ) at the short focal length extremity may be changed depending on the object distance.

As shown in Fig. 10, the variable power optical system of the comparative example (reference example) 8 is composed of, in order from the object side, a first lens group G1 with negative refractive power, a second lens group G2 with negative refractive power, a third lens group G3 with positive refractive power, a fourth lens group G4 with negative refractive power, and a fifth lens group G5 with positive refractive power. The third lens group G3 is composed of, in order from the object side, a third A lens group G3A with positive refractive power, an aperture stop AST, and a third B lens group G3B with positive refractive power. A cover glass CG is disposed between the fifth lens group G5 and the image surface IM.

The first lens group G1, the second lens group G2, and the third lens group G3A constitute an object-side lens group G _ob . The first lens group G1 constitutes an object-side first lens group G _ob1 , and the second lens group G2 constitutes an object-side second lens group G _ob2 .

The 3B lens group G3B, the 4th lens group G4, and the 5th lens group G5 constitute an image side lens group G _im . The 3B lens group G3B constitutes an image side first lens group G _im1 having a positive refractive power, the 4th lens group G4 constitutes an image side intermediate lens group G _im2 , and the 5th lens group G5 constitutes an image side final lens group G _L.

The second lens group G2, which is at least a part of the object-side second lens group G _ob2 , constitutes an object-side focusing lens group FL _ob that moves in the optical axis direction when focusing from infinity to a close distance. The fourth lens group G4, which is at least a part of the image-side intermediate lens group G _im2 , constitutes an image-side focusing lens group FL _im that moves in the optical axis direction when focusing from infinity to a close distance.

When changing magnification from the short focal length end to the long focal length end, the spacing between adjacent lens groups changes. Specifically, when changing magnification from the short focal length end to the long focal length end, the air spacing between the first lens group G1 and the second lens group G2 decreases, the air spacing between the second lens group G2 and the third lens group G3 decreases, the air spacing between the third lens group G3 and the fourth lens group G4 increases, the air spacing between the fourth lens group G4 and the fifth lens group G5 increases, and the air spacing between the fifth lens group G5 and the image plane IM changes. The fifth lens group G5 may be fixed with respect to the image plane IM when changing magnification from the short focal length end to the long focal length end.

When focusing from infinity to a close distance, the movement loci of the second lens group G2 (object side focusing lens group FL _ob ) and the fourth lens group G4 (image side focusing lens group FL _im ) are different from each other. When focusing from infinity to a close distance, the second lens group G2 (object side focusing lens group FL _ob ) moves in the optical axis direction, preferably toward the object side. When focusing from infinity to a close distance, the fourth lens group G4 (image side focusing lens group FL _im ) moves in the optical axis direction. When focusing from infinity to a close distance, it is preferable that at the short focal length end, the fourth lens group G4 (image side focusing lens group FL _im ) moves toward the object side or image side, and at the long focal length end, the fourth lens group G4 (image side focusing lens group FL _im ) moves toward the object side or image side. Furthermore, the movement direction of the fourth lens group G4 (image-side focusing lens group FL _im ) may be changed depending on the object distance.

As shown in FIG. 11, the variable magnification optical system of Numerical Example 9 is composed of, in order from the object side, a first lens group G1 with positive refractive power, a second lens group G2 with negative refractive power, an aperture stop AST, a third lens group G3 with positive refractive power, a fourth lens group G4 with negative refractive power, a fifth lens group G5 with positive refractive power, and a sixth lens group G6 with negative refractive power. A cover glass CG is disposed between the sixth lens group G6 and the image surface IM.

The first lens group G1 and the second lens group G2 constitute an object-side lens group G _ob 1 , and the second lens group G2 constitutes an object-side second lens group G _{ob 2} .

The third lens group G3, the fourth lens group G4, the fifth lens group G5, and the sixth lens group G6 constitute an image side lens group G _im . The third lens group G3 constitutes an image side first lens group G _im1 having a positive refractive power, the fourth lens group G4 constitutes an image side intermediate lens group G _im2 , and the fifth lens group G5 and the sixth lens group G6 constitute an image side final lens group G _L.

The second lens group G2, which is at least a part of the object-side second lens group G _ob2 , constitutes an object-side focusing lens group FL _ob that moves in the optical axis direction when focusing from infinity to a close distance. The fourth lens group G4, which is at least a part of the image-side intermediate lens group G _im2 , constitutes an image-side focusing lens group FL _im that moves in the optical axis direction when focusing from infinity to a close distance.

When the magnification is changed from the short focal length end to the long focal length end, the distance between the adjacent lens groups changes. Specifically, when the magnification is changed from the short focal length end to the long focal length end, the air distance between the first lens group G1 and the second lens group G2 increases, the air distance between the second lens group G2 and the third lens group G3 decreases, the air distance between the third lens group G3 and the fourth lens group G4 increases, the air distance between the fourth lens group G4 and the fifth lens group G5 decreases, the air distance between the fifth lens group G5 and the sixth lens group G6 changes, and the air distance between the sixth lens group G6 and the image plane IM changes. One or both of the second lens group G2 and the fourth lens group G4 may be fixed with respect to the image plane IM when the magnification is changed from the short focal length end to the long focal length end. The aperture stop AST is placed between the second lens group G2 and the third lens group G3, and can be moved along the same trajectory as the third lens group G3 during the magnification change. Alternatively, the aperture stop AST can be moved on a separate trajectory from the third lens group G3 when changing magnification.

When focusing from infinity to a close distance, the movement trajectories of the second lens group G2 (object side focusing lens group FL _ob ) and the fourth lens group G4 (image side focusing lens group FL _im ) are different from each other. When focusing from infinity to a close distance, the second lens group G2 (object side focusing lens group FL _ob ) moves in the optical axis direction, preferably toward the object side. When focusing from infinity to a close distance, the fourth lens group G4 (image side focusing lens group FL _im ) moves in the optical axis direction. When focusing from infinity to a close distance, it is preferable that at the short focal length end, the fourth lens group G4 (image side focusing lens group FL _im ) moves toward the object side or image side, and at the long focal length end, the fourth lens group G4 (image side focusing lens group FL _im ) moves toward the object side. Furthermore, the movement direction of the fourth lens group G4 (image-side focusing lens group FL _im ) at the short focal length extremity may be changed depending on the object distance.

Alternatively, the lens elements constituting the second lens group G2 may be divided into a second-a lens group G2a having a negative refractive power and a second-b lens group G2b having a negative refractive power, and one of these may be used as the object-side focusing lens group FL _ob .

As shown in FIG. 12, the variable magnification optical system of Numerical Example 10 is composed of, in order from the object side, a first lens group G1 with positive refractive power, a second lens group G2 with negative refractive power, a third lens group G3 with negative refractive power, an aperture stop AST, a fourth lens group G4 with positive refractive power, a fifth lens group G5 with positive refractive power, a sixth lens group G6 with negative refractive power, and a seventh lens group G7 with negative refractive power. A cover glass CG is disposed between the seventh lens group G7 and the image surface IM.

The first lens group G1, the second lens group G2, and the third lens group G3 constitute an object-side lens group G _ob . The first lens group G1 constitutes an object-side first lens group G _ob1 , and the second lens group G2 and the third lens group G3 constitute an object-side second lens group G _ob2 .

The fourth lens group G4, the fifth lens group G5, the sixth lens group G6, and the seventh lens group G7 constitute an image side lens group G _im . The fourth lens group G4 constitutes an image side first lens group G _im1 having a positive refractive power, the fifth lens group G5 constitutes an image side intermediate lens group G _im2 , and the sixth lens group G6 and the seventh lens group G7 constitute an image side final lens group G _L.

The third lens group G3, which is at least a part of the object-side second lens group G _ob2 , constitutes an object-side focusing lens group FL _ob that moves in the optical axis direction when focusing from infinity to a close distance. The fifth lens group G5, which is at least a part of the image-side intermediate lens group G _im2 , constitutes an image-side focusing lens group FL _im that moves in the optical axis direction when focusing from infinity to a close distance.

When changing magnification from the short focal length end to the long focal length end, the spacing between adjacent lens groups changes. Specifically, when changing magnification from the short focal length end to the long focal length end, the air spacing between the first lens group G1 and the second lens group G2 increases, the air spacing between the second lens group G2 and the third lens group G3 changes, the air spacing between the third lens group G3 and the fourth lens group G4 decreases, the air spacing between the fourth lens group G4 and the fifth lens group G5 changes, the air spacing between the fifth lens group G5 and the sixth lens group G6 changes, the air spacing between the sixth lens group G6 and the seventh lens group G7 changes, and the air spacing between the seventh lens group G7 and the image plane IM changes. One or both of the first lens group G1 and the fourth lens group G4 may be fixed with respect to the image plane IM when changing magnification from the short focal length end to the long focal length end. The aperture stop AST is located between the third lens group G3 and the fourth lens group G4, and can be moved along the same trajectory as the fourth lens group G4 when changing magnification. Alternatively, the aperture stop AST can be moved along a trajectory separate from the fourth lens group G4 when changing magnification.

When focusing from infinity to a close distance, the movement trajectories of the third lens group G3 (object-side focusing lens group FL _ob ) and the fifth lens group G5 (image-side focusing lens group FL _im ) are different from each other. When focusing from infinity to a close distance, the third lens group G3 (object-side focusing lens group FL _ob ) moves toward the object side or image side in the optical axis direction. In addition, the movement direction of the third lens group G3 (object-side focusing lens group FL _ob ) may be changed depending on the object distance. When focusing from infinity to a close distance, the fifth lens group G5 (image-side focusing lens group FL _im ) moves in the optical axis direction, preferably toward the object side.

The second lens group G2 and the third lens group G3, i.e., the entire object-side second lens group G _ob2, may be the object-side focusing lens group FL _ob . In that case, when focusing from infinity to a close distance, the air distance between the second lens group G2 and the third lens group G3 may be constant, or the air distance between the second lens group G2 and the third lens group G3 may be changed depending on the object distance.

As shown in FIG. 13, the variable magnification optical system of Numerical Example 11 is composed of, in order from the object side, a first lens group G1 with negative refractive power, a second lens group G2 with positive refractive power, a third lens group G3 with negative refractive power, an aperture stop AST, a fourth lens group G4 with negative refractive power, a fifth lens group G5 with positive refractive power, a sixth lens group G6 with negative refractive power, and a seventh lens group G7 with positive refractive power.

The first lens group G1, the second lens group G2, and the third lens group G3 constitute an object-side lens group G _ob . The first lens group G1 constitutes an object-side first lens group G _ob1 , and the second lens group G2 and the third lens group G3 constitute an object-side second lens group G _ob2 .

The fourth lens group G4, the fifth lens group G5, the sixth lens group G6, and the seventh lens group G7 constitute an image side lens group G _im . The fourth lens group G4 and the fifth lens group G5 constitute an image side first lens group G _im1 having a positive refractive power, the sixth lens group G6 constitutes an image side intermediate lens group G _im2 , and the seventh lens group G7 constitutes an image side final lens group G _L.

The third lens group G3, which is at least a part of the object-side second lens group G _ob2 , constitutes an object-side focusing lens group FL _ob that moves in the optical axis direction when focusing from infinity to a close distance. The sixth lens group G6, which is at least a part of the image-side intermediate lens group G _im2 , constitutes an image-side focusing lens group FL _im that moves in the optical axis direction when focusing from infinity to a close distance.

When changing magnification from the short focal length end to the long focal length end, the spacing between adjacent lens groups changes. Specifically, when changing magnification from the short focal length end to the long focal length end, the air spacing between the first lens group G1 and the second lens group G2 decreases, the air spacing between the second lens group G2 and the third lens group G3 increases, the air spacing between the third lens group G3 and the fourth lens group G4 decreases, the air spacing between the fourth lens group G4 and the fifth lens group G5 decreases, the air spacing between the fifth lens group G5 and the sixth lens group G6 changes, the air spacing between the sixth lens group G6 and the seventh lens group G7 increases, and the air spacing between the seventh lens group G7 and the image plane IM increases. The seventh lens group G7 may be fixed with respect to the image plane IM when changing magnification from the short focal length end to the long focal length end. The aperture stop AST is located between the third lens group G3 and the fourth lens group G4, and can be moved along the same trajectory as the fourth lens group G4 when changing magnification. Alternatively, the aperture stop AST can be moved along a trajectory separate from the fourth lens group G4 when changing magnification.

When focusing from infinity to a close distance, the movement loci of the third lens group G3 (object-side focusing lens group FL _ob ) and the sixth lens group G6 (image-side focusing lens group FL _im ) are different from each other. When focusing from infinity to a close distance, the third lens group G3 (object-side focusing lens group FL _ob ) moves in the optical axis direction, preferably toward the object side. When focusing from infinity to a close distance, the sixth lens group G6 (image-side focusing lens group FL _im ) moves in the optical axis direction, preferably toward the image side.

In the variable magnification optical system of this embodiment, multiple focusing lens groups are provided, and a floating focus method is adopted in which the multiple focusing lens groups are moved in the optical axis direction during focusing, thereby making it possible to suppress aberration changes from infinity to close distances.

The focusing lens groups are arranged such that the aperture stop is sandwiched between the object side and the image side of the focusing lens group. In this case, the object side focusing lens group and the image side focusing lens group are located on the object side and the image side of the aperture stop, respectively, so the heights from the optical axis of the off-axis chief rays passing through each focusing lens group have opposite signs. This increases the independence of aberration correction for the upper and lower light beams of off-axis light, allowing for good correction of off-axis aberrations such as coma and field curvature.

In addition, since the object-side focusing lens group is the lens group located on the image side of the lens group closest to the object (in front of the aperture stop), the height from the optical axis of off-axis rays incident on the object-side focusing lens group is relatively small. Therefore, the effective diameter of the object-side focusing lens group is smaller than the effective diameter of the first object-side lens group. This makes it possible to make the object-side focusing lens group lightweight.

In addition, on the object side of the image-side focusing lens group, there is an aperture stop and a lens group with positive refractive power. Because the image-side first lens group has positive refractive power, its converging action makes the height from the optical axis of the axial ray that enters the image-side focusing lens group relatively small. This reduces the effective diameter of the lens, allowing the image-side focusing lens group to be made lighter.

Furthermore, by arranging one or more lens groups on the image side of the image-side focusing lens group, off-axis aberrations such as field curvature and lateral chromatic aberration can be effectively corrected, and the image-side focusing lens group can be made into a relatively simple configuration.

Furthermore, the variable magnification optical system of this embodiment has multiple lens groups (focusing lens groups) used for focusing, and also specifies the magnitude relationship between the refractive powers and focus sensitivities of the multiple focusing lens groups.

Specifically, the refractive power and focus sensitivity of the two focusing lens groups, the object side focusing lens group FL _ob and the image side focusing lens group FL _im, are optimally set by a conditional formula. In the variable magnification optical system of this embodiment, the air gap between each lens group of the object side lens group G _ob including the object side focusing lens group FL _ob is changed to generate the main variable _{magnification} effect. In addition, the image side intermediate lens group G _im2 including the image side focusing lens group FL im corrects aberrations such as field curvature that occur with variable magnification and focusing. Therefore, by optimally setting the refractive power and focus sensitivity of each of the object side focusing lens group FL _ob and the image side focusing lens group FL _im , good aberration correction can be performed.

In the following, the conditional expressions that the variable magnification optical system should satisfy will be described in detail, separately for cases where the positional relationship between the object-side focusing lens group FL _ob and the image-side focusing lens group FL _im is distinguished and where it is not.

<<When Distinguishing the Positional Relationship Between the Object-Side Focusing Lens Group FL _ob and the Image-Side Focusing Lens Group FL _im >>
The object-side focusing lens group FL _ob is defined as the first focusing lens group, and the image-side focusing lens group FL _im is defined as the second focusing lens group, and the ranges of the conditional expressions related to |f1/f2| (the ratio of the focal lengths of the first and second focusing lens groups) and |p2T/p1T| (the ratio of the focus sensitivities of the first and second focusing lens groups) are appropriately set.

Here, the focus sensitivity is an inherent value of the optical system that indicates the change in position of the paraxial image plane when the focusing lens group moves a unit amount in the optical axis direction, and is defined as follows:
p=(1-mF^2)×mR^2
mF: paraxial lateral magnification of the focusing lens group,
mR: paraxial lateral magnification of the optical system on the image side of the focusing lens group,
It is.

<Aspect 1>
It is preferable that the variable magnification optical system of this embodiment satisfies the following conditional expressions (1) and (2).
(1) 0.1<|f1/f2|<10
(2) 3.0<|p2T/p1T|<30
however,
f1: focal length of the first focusing lens group,
f2: focal length of the second focusing lens group,
p1T: focus sensitivity of the first focusing lens group when focusing on infinity at the long focal length end,
p2T: focus sensitivity of the second focusing lens group when focusing on infinity at the long focal length end,
p1T=(1-m1T^2)×m1RT^2
p2T=(1-m2T^2)×m2RT^2
m1T: paraxial lateral magnification of the first focusing lens group when focusing on infinity at the long focal length end,
m1RT: paraxial lateral magnification of the optical system on the image side of the first focusing lens group when focusing on infinity at the long focal length end,
m2T: paraxial lateral magnification of the second focusing lens group when focusing on infinity at the long focal length end,
m2RT: paraxial lateral magnification of the optical system on the image side of the second focusing lens group when focusing on infinity at the long focal length end,
It is.

Conditional expression (1) defines the ratio of the refractive powers of the first and second focusing lens groups for achieving good aberration correction. By satisfying conditional expression (1), it is possible to suppress aberration fluctuations during zooming from the short focal length end to the long focal length end and during focusing from infinity to a close object, thereby obtaining good performance.
If the upper limit of conditional expression (1) is exceeded, the refractive power of the first focusing lens group becomes too small, the amount of movement of the first focusing lens group accompanying the magnification change increases, and the fluctuation of off-axis aberrations such as curvature of field and coma aberration becomes large, which is undesirable. Furthermore, the absolute value of the refractive power of the second focusing lens group becomes too large, which is undesirable because large off-axis aberrations occur. More preferably, the upper limit of conditional expression (1) should be set to 9.0, further 8.0, further 7.0, further 6.0, or even 5.0.
If the lower limit of conditional expression (1) is exceeded, the refractive power of the first focusing lens group becomes too large, which is undesirable because it increases the fluctuations in spherical aberration and coma aberration associated with magnification change. Furthermore, the refractive power of the second focusing lens group becomes too small, which makes it impossible to appropriately correct aberrations such as field curvature. It is more preferable to set the lower limit of conditional expression (1) to 0.2.

Condition (2) defines the ratio of the focusing sensitivities of the first and second focusing lens groups when focusing on an object at infinity at the long focal length extremity. By satisfying condition (2), it is possible to suppress aberration fluctuations when focusing from infinity to a close object, and to obtain good performance.
The amount of movement of the focusing lens group required to correct the focal position depends on the focus sensitivity. Increasing the focus sensitivity reduces the amount of movement of the focusing lens group, and it is possible to suppress aberration fluctuations caused by changes in the position of the focusing lens group. However, if the focus sensitivity is too high, high precision is required for the mechanism for moving the focusing lens group. On the other hand, if the focus sensitivity is too low, the amount of movement of the focusing lens group increases in order to correct the focal position, resulting in large aberration fluctuations.
If the upper limit of conditional expression (2) is exceeded, the focus sensitivity of the second focusing lens group becomes too high, and the precision required for the mechanism for moving the second focusing lens group becomes high, leading to increased costs. Also, in order to correct the focus change caused by the movement of the second focusing lens group, the movement amount of the first focusing lens group increases, which is undesirable because it increases the fluctuation of coma aberration and the like. More preferably, the upper limit of conditional expression (2) is set to 20.
If the lower limit of the conditional expression (2) is exceeded, the focus sensitivity of the first focusing lens group becomes too high, and the precision required for the mechanism that moves the first focusing lens group becomes high, leading to an increase in costs. Also, in order to correct the focus change caused by the movement of the first focusing lens group, the movement amount of the second focusing lens group increases, which is undesirable because it increases the fluctuation of the field curvature, etc.

It is preferable that conditional expressions (1) and (2) are satisfied simultaneously, but it is also possible to satisfy only one of conditional expressions (1) and (2).

It is preferable that the variable magnification optical system of this embodiment satisfies the following conditional expression (3).
(3) 0.10<|p2W/p2T|<10
however,
p2W: focus sensitivity of the second focusing lens group when focusing on infinity at the short focal length end,
p2T: focus sensitivity of the second focusing lens group when focusing on infinity at the long focal length end,
p2W=(1-m2W^2)×m2RW^2
p2T=(1-m2T^2)×m2RT^2
m2W: paraxial lateral magnification of the second focusing lens group when focusing on infinity at the short focal length end,
m2RW: paraxial lateral magnification of the optical system on the image side of the second focusing lens group when focusing on infinity at the short focal length end,
m2T: paraxial lateral magnification of the second focusing lens group when focusing on infinity at the long focal length end,
m2RT: paraxial lateral magnification of the optical system on the image side of the second focusing lens group when focusing on infinity at the long focal length end,
It is.

It is preferable that the variable magnification optical system of this embodiment satisfies the following conditional expression (4).
(4) 0.05<|p1W/p1T|<5.0
however,
p1W: focus sensitivity of the first focusing lens group when focusing on infinity at the short focal length end,
p1T: focus sensitivity of the first focusing lens group when focusing on infinity at the long focal length end,
p1W=(1-m1W^2)×m1RW^2
p1T=(1-m1T^2)×m1RT^2
m1W: paraxial lateral magnification of the first focusing lens group when focusing on infinity at the short focal length extremity,
m1RW: paraxial lateral magnification of the optical system on the image side of the first focusing lens group when focusing on infinity at the short focal length end,
m1T: paraxial lateral magnification of the first focusing lens group when focusing on infinity at the long focal length end,
m1RT: paraxial lateral magnification of the optical system on the image side of the first focusing lens group when focusing on infinity at the long focal length end,
It is.

In general, the amount of movement of the focusing lens group when focusing on an arbitrary object distance depends on the focal length of the entire system and the focus sensitivity of the focusing lens group at that focal length. In this embodiment, the focus sensitivity of the focusing lens group is appropriately set at the short focal length end and the long focal length end to suppress aberration fluctuations when focusing on an object at a finite distance.

Condition (3) defines the ratio of the focus sensitivities of the second focusing lens group when focusing on an object at infinity at the short focal length extremity and the long focal length extremity in order to perform favorable aberration correction.
If the upper limit value of conditional expression (3) is exceeded, the focus sensitivity of the second focusing lens group at the long focal length extremity becomes too small, the amount of movement of the second focusing lens group accompanying focusing increases, and fluctuations in the curvature of field, etc., become large, which is undesirable. It is more preferable to set the upper limit value of conditional expression (3) to 9.0, further preferably 8.0, and further preferably 7.0.
If the lower limit of conditional expression (3) is not reached, the focus sensitivity of the second focusing lens group at the long focal length extremity becomes excessively high, and the precision required for the mechanism that moves the second focusing lens group increases, leading to increased costs. It is more preferable to set the lower limit of conditional expression (3) to 0.2.

Condition (4) defines the ratio of the focus sensitivities of the first focusing lens group when focusing on an object at infinity at the short focal length extremity and the long focal length extremity in order to perform favorable aberration correction.
If the upper limit of conditional expression (4) is exceeded, the focus sensitivity of the first focusing lens group at the long focal length extremity becomes too small, the amount of movement of the first focusing lens group associated with focusing increases, and fluctuations in coma aberration and the like become large, which is undesirable. It is more preferable to set the upper limit of conditional expression (4) to 4.0.
If the lower limit of conditional expression (4) is not reached, the focus sensitivity of the first focusing lens group at the long focal length extremity becomes excessively high, and the precision required for the mechanism that moves the first focusing lens group increases, leading to increased costs. It is more preferable to set the lower limit of conditional expression (4) to 0.2, or even 0.3.

It is preferable that the variable magnification optical system of this embodiment satisfies the following conditional expression (5).
(5) 1.5<|p2W/p1W|<15
however,
p1W: focus sensitivity of the first focusing lens group when focusing on infinity at the short focal length end,
p2W: focus sensitivity of the second focusing lens group when focusing on infinity at the short focal length end,
p1W=(1-m1W^2)×m1RW^2
p2W=(1-m2W^2)×m2RW^2
m1W: paraxial lateral magnification of the first focusing lens group when focusing on infinity at the short focal length extremity,
m1RW: paraxial lateral magnification of the optical system on the image side of the first focusing lens group when focusing on infinity at the short focal length end,
m2W: paraxial lateral magnification of the second focusing lens group when focusing on infinity at the short focal length end,
m2RW: paraxial lateral magnification of the optical system on the image side of the second focusing lens group when focusing on infinity at the short focal length end,
It is.

Conditional expression (5) defines the ratio of the focusing sensitivities of the first and second focusing lens groups when focusing on an object at infinity at the short focal length extremity. By satisfying conditional expression (5), it is possible to suppress aberration fluctuations when focusing from infinity to a close object at the short focal length extremity, and to obtain good performance.
If the upper limit of the conditional expression (5) is exceeded, the focus sensitivity of the second focusing lens group becomes too high, and the precision required for the mechanism that moves the second focusing lens group becomes high, leading to an increase in costs. Also, in order to correct the focus change caused by the movement of the second focusing lens group, the movement amount of the first focusing lens group increases, which is undesirable because it increases the fluctuation of coma aberration and the like.
If the lower limit of conditional expression (5) is exceeded, the focus sensitivity of the first focusing lens group becomes too high, and the precision required for the mechanism that moves the first focusing lens group becomes high, leading to increased costs. Also, in order to correct the focus change caused by the movement of the first focusing lens group, the movement amount of the second focusing lens group increases, which is undesirable because it increases the fluctuation of the field curvature and the like.

It is preferable that the variable magnification optical system of this embodiment satisfies the following conditional expressions (6) and (7).
(6) 1.3<d1W/d2W<2.0
(7) 0.015<d1T/d2T<0.15
however,
d1W: the length from the aperture stop to the optical surface of the first focusing lens group closest to the aperture stop at the short focal length end,
d2W: the length from the aperture stop to the optical surface of the second focusing lens group closest to the aperture stop at the short focal length end,
d1T: the length from the aperture stop to the optical surface of the first focusing lens group closest to the aperture stop at the long focal length end,
d2T: the length from the aperture stop to the optical surface of the second focusing lens group closest to the aperture stop at the long focal length end,
It is.

Condition (6) defines the arrangement of the first and second focusing lens groups so that the correction of off-axis aberrations is appropriately shared between the first and second focusing lens groups.
As described above, in this embodiment, the heights from the optical axis of the off-axis chief rays that pass through the first and second focusing lens groups have opposite signs to each other. In particular, at the short focal length end, it is desirable to pass the off-axis light beams so that the absolute values of the off-axis chief rays are close to each other, that is, in a nearly symmetrical relationship with respect to the first and second focusing lens groups.
By satisfying conditional expression (6), the distances from the aperture stop to the first and second focusing lens groups become nearly equal, enabling off-axis aberrations at the short focal length extremity to be corrected satisfactorily.
If the upper limit of conditional expression (6) is exceeded, the height of the off-axis ray passing through the second focusing lens group becomes too low, making it difficult to sufficiently correct off-axis aberrations such as field curvature, and also increasing the effective diameter of the first focusing lens group relatively, which increases the weight of the first focusing lens group, leading to increased costs.
If the lower limit of conditional expression (6) is exceeded, the height of the off-axis light passing through the first focusing lens group becomes relatively too low, making it difficult to sufficiently correct coma aberration, etc. Also, the effective diameter of the second focusing lens group increases, and the weight of the second focusing lens group increases, leading to increased costs.

Condition (7) defines the position of the first focusing lens group at the long focal length extremity. By satisfying condition (7), the mechanical arrangement of the optical system at the long focal length extremity can be appropriately performed.
At the long focal length extremity, the axial marginal ray becomes a divergent ray due to the object-side second lens group including the first focusing lens group, and enters the aperture stop.
If the upper limit value of conditional expression (7) is exceeded, the distance between the first focusing lens group and the aperture stop becomes too large, and the height of the axial ray diverging from the object-side second lens group and the first focusing lens group becomes large at the aperture stop position, which leads to an increase in the mechanical size of the aperture stop.
If the lower limit of conditional expression (7) is exceeded, the distance between the first focusing lens group and the aperture stop becomes relatively close, making it difficult to avoid physical interference between the mechanism that holds the focusing lens group and the aperture stop, which is not preferable.

<Aspect 2>
It is preferable that the variable magnification optical system of this embodiment satisfies the following conditional expressions (1') and (2').
(1') 1.0<|f1/f2|<10
(2') 0.03<|p2T/p1T|<0.3
however,
f1: focal length of the first focusing lens group,
f2: focal length of the second focusing lens group,
p1T: focus sensitivity of the first focusing lens group when focusing on infinity at the long focal length end,
p2T: focus sensitivity of the second focusing lens group when focusing on infinity at the long focal length end,
p1T=(1-m1T^2)×m1RT^2
p2T=(1-m2T^2)×m2RT^2
m1T: paraxial lateral magnification of the first focusing lens group when focusing on infinity at the long focal length end,
m1RT: paraxial lateral magnification of the optical system on the image side of the first focusing lens group when focusing on infinity at the long focal length end,
m2T: paraxial lateral magnification of the second focusing lens group when focusing on infinity at the long focal length end,
m2RT: the paraxial lateral magnification of the optical system on the image side of the second focusing lens group when focusing on infinity at the long focal length end.

Conditional expression (1') defines the ratio of the refractive powers of the first and second focusing lens groups for achieving good aberration correction. By satisfying conditional expression (1'), it is possible to suppress aberration fluctuations during zooming from the short focal length extremity to the long focal length extremity and during focusing from infinity to a close object, thereby obtaining good performance.
If the upper limit of conditional expression (1') is exceeded, the refractive power of the first focusing lens group becomes too small, the amount of movement of the first focusing lens group accompanying the magnification change increases, and the fluctuation of off-axis aberrations such as curvature of field and coma aberration becomes large, which is undesirable. Furthermore, the absolute value of the refractive power of the second focusing lens group becomes too large, which is undesirable because large off-axis aberrations occur. More preferably, the upper limit of conditional expression (1') should be set to 9.0, further 8.0, further 7.0, further 6.0, or even 5.0.
If the lower limit of conditional expression (1') is not reached, the refractive power of the first focusing lens group becomes too large, which is undesirable since it increases the fluctuations of spherical aberration and coma aberration accompanying zooming, and the refractive power of the second focusing lens group becomes too small, which makes it impossible to appropriately correct aberrations such as field curvature.

Condition (2') defines the ratio of the focusing sensitivities of the first and second focusing lens groups when focusing on an object at infinity at the long focal length extremity. By satisfying condition (2'), it is possible to suppress aberration fluctuations when focusing from infinity to a close object, and to obtain good performance.
If the upper limit of the conditional expression (2') is exceeded, the focus sensitivity of the second focusing lens group becomes too high, and the precision required for the mechanism for moving the second focusing lens group becomes high, leading to an increase in costs. Also, in order to correct the focus change caused by the movement of the second focusing lens group, the movement amount of the first focusing lens group increases, which is undesirable because it increases the fluctuation of coma aberration and the like.
If the lower limit of the conditional formula (2') is exceeded, the focus sensitivity of the first focusing lens group becomes too high, and the precision required for the mechanism that moves the first focusing lens group becomes high, leading to an increase in costs. Also, in order to correct the focus change caused by the movement of the first focusing lens group, the movement amount of the second focusing lens group increases, which is undesirable because it increases the fluctuation of the field curvature, etc.

It is preferable that conditional formula (1') and conditional formula (2') are satisfied simultaneously, but it is also possible to satisfy only one of conditional formula (1') and conditional formula (2').

It is preferable that the variable magnification optical system of this embodiment satisfies the following conditional expression (3').
(3') 1.0<|p2W/p2T|<10
however,
p2W: focus sensitivity of the second focusing lens group when focusing on infinity at the short focal length end,
p2T: focus sensitivity of the second focusing lens group when focusing on infinity at the long focal length end,
p2W=(1-m2W^2)×m2RW^2
p2T=(1-m2T^2)×m2RT^2
m2W: paraxial lateral magnification of the second focusing lens group when focusing on infinity at the short focal length end,
m2RW: paraxial lateral magnification of the optical system on the image side of the second focusing lens group when focusing on infinity at the short focal length end,
m2T: paraxial lateral magnification of the second focusing lens group when focusing on infinity at the long focal length end,
m2RT: paraxial lateral magnification of the optical system on the image side of the second focusing lens group when focusing on infinity at the long focal length end,
It is.

It is preferable that the variable magnification optical system of this embodiment satisfies the following conditional expression (4').
(4') 0.0015<|p1W/p1T|<0.15
however,
p1W: focus sensitivity of the first focusing lens group when focusing on infinity at the short focal length end,
p1T: focus sensitivity of the first focusing lens group when focusing on infinity at the long focal length end,
p1W=(1-m1W^2)×m1RW^2
p1T=(1-m1T^2)×m1RT^2
m1W: paraxial lateral magnification of the first focusing lens group when focusing on infinity at the short focal length extremity,
m1RW: paraxial lateral magnification of the optical system on the image side of the first focusing lens group when focusing on infinity at the short focal length end,
m1T: paraxial lateral magnification of the first focusing lens group when focusing on infinity at the long focal length end,
m1RT: paraxial lateral magnification of the optical system on the image side of the first focusing lens group when focusing on infinity at the long focal length end,
It is.

Condition (3') defines the ratio of the focusing sensitivities of the second focusing lens group when focusing on infinity at the short focal length extremity and the long focal length extremity in order to perform favorable aberration correction.
If the upper limit value of conditional expression (3') is exceeded, the focus sensitivity of the second focusing lens group at the long focal length extremity becomes too small, the amount of movement of the second focusing lens group accompanying focusing increases, and fluctuations in the curvature of field, etc., become large, which is undesirable. It is more preferable to set the upper limit value of conditional expression (3') to 9.0, further preferably 8.0, and further preferably 7.0.
If the lower limit of condition (3') is exceeded, the focus sensitivity of the second focusing lens group at the long focal length extremity becomes excessive, and the precision required for the mechanism that moves the second focusing lens group increases, leading to increased costs.

Condition (4') defines the ratio of the focusing sensitivities of the first focusing lens group when focusing on infinity at the short focal length extremity and the long focal length extremity in order to perform favorable aberration correction.
If the upper limit value of conditional expression (4') is exceeded, the focus sensitivity of the first focusing lens group at the long focal length extremity becomes too small, the amount of movement of the first focusing lens group associated with focusing increases, and fluctuations in coma aberration and the like become large, which is undesirable.
If the lower limit of conditional expression (4') is not reached, the focus sensitivity of the first focusing lens group at the long focal length extremity becomes excessively high, and the precision required for the mechanism that moves the first focusing lens group increases, leading to increased costs. It is more preferable to set the lower limit of conditional expression (4') to 0.015.

It is preferable that the variable magnification optical system of this embodiment satisfies the following conditional expression (5').
(5')1.5<|p2W/p1W|<15
however,
p1W: focus sensitivity of the first focusing lens group when focusing on infinity at the short focal length end,
p2W: focus sensitivity of the second focusing lens group when focusing on infinity at the short focal length end,
p1W=(1-m1W^2)×m1RW^2
p2W=(1-m2W^2)×m2RW^2
m1W: paraxial lateral magnification of the first focusing lens group when focusing on infinity at the short focal length extremity,
m1RW: paraxial lateral magnification of the optical system on the image side of the first focusing lens group when focusing on infinity at the short focal length end,
m2W: paraxial lateral magnification of the second focusing lens group when focusing on infinity at the short focal length end,
m2RW: paraxial lateral magnification of the optical system on the image side of the second focusing lens group when focusing on infinity at the short focal length end,
It is.

Condition (5') defines the ratio of the focusing sensitivities of the first and second focusing lens groups when focusing on an object at infinity at the short focal length extremity. By satisfying condition (5'), it is possible to suppress aberration fluctuations when focusing from infinity to a close object at the short focal length extremity, and to obtain good performance.
If the upper limit of conditional formula (5') is exceeded, the focus sensitivity of the second focusing lens group becomes excessive, and the precision required for the mechanism that moves the second focusing lens group becomes high, leading to increased costs. Also, in order to correct the focus change caused by the movement of the second focusing lens group, the movement amount of the first focusing lens group increases, which is undesirable because it increases the fluctuation of coma aberration and the like. More preferably, the upper limit of conditional formula (5') should be set to 10.
If the lower limit of conditional expression (5') is exceeded, the focus sensitivity of the first focusing lens group becomes excessive, and the precision required for the mechanism that moves the first focusing lens group becomes high, leading to increased costs. Also, in order to correct the focus change caused by the movement of the first focusing lens group, the movement amount of the second focusing lens group increases, which is undesirable because it increases the fluctuation of the field curvature, etc.

It is preferable that the variable magnification optical system of this embodiment satisfies the following conditional expressions (6') and (7').
(6') 1.3<d1W/d2W<2.0
(7') 0.015<d1T/d2T<0.15
however,
d1W: the length from the aperture stop to the optical surface of the first focusing lens group closest to the aperture stop at the short focal length end,
d2W: the length from the aperture stop to the optical surface of the second focusing lens group closest to the aperture stop at the short focal length end,
d1T: the length from the aperture stop to the optical surface of the first focusing lens group closest to the aperture stop at the long focal length end,
d2T: the length from the aperture stop to the optical surface of the second focusing lens group closest to the aperture stop at the long focal length end,
It is.

Conditional expressions (6') and (7') in <Aspect 2> are the same as conditional expressions (6) and (7) in <Aspect 1>, so redundant explanations will be omitted.

<<When the positional relationship between the object-side focusing lens group FL _ob and the image-side focusing lens group FL _im is not distinguished>>
One of the object-side focusing lens group FL _ob and the image-side focusing lens group FL _im is defined as the first focusing lens group, and the other of the object-side focusing lens group FL _ob and the image-side focusing lens group FL _im is defined as the second focusing lens group, and the range of the conditional expression is appropriately set. The first and second focusing lens groups are defined by |f1/f2| (the ratio of the focal lengths of the first and second focusing lens groups), and |p2T/p1T| (the ratio of the focus sensitivities of the first and second focusing lens groups) in that case is appropriately set.

In conventional technology, the focusing lens group with the largest absolute value of refractive power has the main focusing function (the role of correcting the position of the image point due to changes in object distance), and the other focusing lens group has the role of correcting various aberrations that occur due to the movement of the main focusing lens group.

In this embodiment, in order to obtain even better performance, the focus sensitivity is set relatively high for the focusing lens group with a relatively low refractive power, thereby reducing the aberration fluctuations that occur due to the movement of the focusing lens group with a high focus sensitivity.

<Aspect 3>
It is preferable that the variable magnification optical system of this embodiment satisfies the following conditional expressions (1A) and (2A).
(1A) | f1/f2 | <1
(2A) 3.0<|p2T/p1T|<30
however,
f1: focal length of the first focusing lens group,
f2: focal length of the second focusing lens group,
p1T: focus sensitivity of the first focusing lens group when focusing on infinity at the long focal length end,
p2T: focus sensitivity of the second focusing lens group when focusing on infinity at the long focal length end,
p1T=(1-m1T^2)×m1RT^2
p2T=(1-m2T^2)×m2RT^2
m1T: paraxial lateral magnification of the first focusing lens group when focusing on infinity at the long focal length end,
m1RT: paraxial lateral magnification of the optical system on the image side of the first focusing lens group when focusing on infinity at the long focal length end,
m2T: paraxial lateral magnification of the second focusing lens group when focusing on infinity at the long focal length end,
m2RT: paraxial lateral magnification of the optical system on the image side of the second focusing lens group when focusing on infinity at the long focal length end,
It is.

Conditional expressions (1A) and (2A) stipulate the ratio of focus sensitivity at the long focal length end of the first and second focusing lens groups in order to perform appropriate aberration correction when the object-side focusing lens group and the image-side focusing lens group, whichever has the greater absolute value of refractive power, are designated as the first focusing lens group, and the one with the smaller absolute value of refractive power is designated as the second focusing lens group. Note that it is desirable to simultaneously satisfy conditional expressions (1A) and (2A), but it is also possible to satisfy only one of conditional expressions (1A) and (2A).

By satisfying conditional expression (1A), the refractive power of the second focusing lens group becomes relatively small, and it is possible to suppress aberration fluctuations caused by the movement of the second focusing lens group.
If the upper limit value of conditional formula (1A) is exceeded, the refractive power of the second focusing lens group becomes large, and the aberration fluctuation caused by the movement of the second focusing lens group becomes large, which is undesirable. More preferably, the upper limit value of conditional formula (1A) should be set to 0.95, and even more preferably 0.85. Moreover, in order to prevent the refractive power of the second focusing lens group from becoming too small, it is more preferable to set the lower limit value of conditional formula (1A) to 0.1.

Condition (2A) defines the ratio of the focusing sensitivities of the first and second focusing lens groups when focusing on an object at infinity at the long focal length extremity. By satisfying condition (2A), it is possible to suppress aberration fluctuations when focusing from infinity to a close object, and to obtain good performance.
If the upper limit of the conditional expression (2A) is exceeded, the focus sensitivity of the second focusing lens group becomes too high, and the precision required for the mechanism for moving the second focusing lens group becomes high, leading to an increase in costs. Also, in order to correct the focus change caused by the movement of the second focusing lens group, the movement amount of the first focusing lens group, which has a low focus sensitivity, increases, which is undesirable because it increases the aberration fluctuation.
If the lower limit of condition (2A) is not satisfied, the focusing sensitivity of the first focusing lens group having a large refractive power becomes too high, which undesirably increases the fluctuation in aberration. Also, the amount of movement of the second focusing lens group increases, which increases the overall length of the optical system and leads to increased costs.

It is preferable that the variable magnification optical system of this embodiment satisfies the following conditional expression (3A).
(3A) 0.02<|p2W/p2T|<2.0
however,
p2W: focus sensitivity of the second focusing lens group when focusing on infinity at the short focal length end,
p2T: focus sensitivity of the second focusing lens group when focusing on infinity at the long focal length end,
p2W=(1-m2W^2)×m2RW^2
p2T=(1-m2T^2)×m2RT^2
m2W: paraxial lateral magnification of the second focusing lens group when focusing on infinity at the short focal length end,
m2RW: paraxial lateral magnification of the optical system on the image side of the second focusing lens group when focusing on infinity at the short focal length end,
m2T: paraxial lateral magnification of the second focusing lens group when focusing on infinity at the long focal length end,
m2RT: paraxial lateral magnification of the optical system on the image side of the second focusing lens group when focusing on infinity at the long focal length end,
It is.

It is preferable that the variable magnification optical system of this embodiment satisfies the following conditional expression (4A).
(4A) 0.7<|p1W/p1T|<7.0
however,
p1W: focus sensitivity of the first focusing lens group when focusing on infinity at the short focal length end,
p1T: focus sensitivity of the first focusing lens group when focusing on infinity at the long focal length end,
p1W=(1-m1W^2)×m1RW^2
p1T=(1-m1T^2)×m1RT^2
m1W: paraxial lateral magnification of the first focusing lens group when focusing on infinity at the short focal length end,
m1RW: paraxial lateral magnification of the optical system on the image side of the first focusing lens group when focusing on infinity at the short focal length end,
m1T: paraxial lateral magnification of the first focusing lens group when focusing on infinity at the long focal length end,
m1RT: paraxial lateral magnification of the optical system on the image side of the first focusing lens group when focusing on infinity at the long focal length end,
It is.

Condition (3A) defines the ratio of the focus sensitivities of the second focusing lens group at the short focal length extremity and the long focal length extremity in order to achieve good aberration correction.
If the upper limit of condition (3A) is exceeded, the focus sensitivity of the second focusing lens group at the long focal length extremity becomes too small, the amount of movement of the second focusing lens group associated with focusing increases, and aberration fluctuations become large, which is undesirable.
If the lower limit of condition (3A) is exceeded, the focus sensitivity of the second focusing lens group at the long focal length extremity becomes excessive, and the precision required for the mechanism that moves the second focusing lens group increases, leading to increased costs.

Condition (4A) defines the ratio of the focus sensitivities of the first focusing lens group at the short focal length extremity and the long focal length extremity in order to achieve good aberration correction.
If the upper limit of condition (4A) is exceeded, the focus sensitivity of the first focusing lens group at the long focal length extremity becomes too small, the amount of movement of the first focusing lens group associated with focusing increases, and aberration fluctuations become large, which is undesirable.
If the lower limit of condition (4A) is exceeded, the focus sensitivity of the first focusing lens group at the long focal length extremity becomes excessive, and the precision required for the mechanism that moves the first focusing lens group increases, leading to increased costs.

It is preferable that the variable magnification optical system of this embodiment satisfies the following condition (5A).
(5A) 0.1<|p2W/p1W|<10
however,
p1W: focus sensitivity of the first focusing lens group when focusing on infinity at the short focal length end,
p2W: focus sensitivity of the second focusing lens group when focusing on infinity at the short focal length end,
p1W=(1-m1W^2)×m1RW^2
p2W=(1-m2W^2)×m2RW^2
m1W: paraxial lateral magnification of the first focusing lens group when focusing on infinity at the short focal length extremity,
m1RW: paraxial lateral magnification of the optical system on the image side of the first focusing lens group when focusing on infinity at the short focal length end,
m2W: paraxial lateral magnification of the second focusing lens group when focusing on infinity at the short focal length end,
m2RW: paraxial lateral magnification of the optical system on the image side of the second focusing lens group when focusing on infinity at the short focal length end,
It is.

Condition (5A) defines the ratio of the focusing sensitivities of the first and second focusing lens groups when focusing on an object at infinity at the short focal length extremity. By satisfying condition (5A), it is possible to suppress aberration fluctuations when focusing from infinity to a close object at the short focal length extremity, and to obtain good performance.
If the upper limit of conditional formula (5A) is exceeded, the focus sensitivity of the second focusing lens group becomes too high, and the precision required for the mechanism that moves the second focusing lens group becomes high, leading to increased costs. Also, in order to correct the focus change caused by the movement of the second focusing lens group, the movement amount of the first focusing lens group increases, which is undesirable because it increases the aberration fluctuation. More preferably, the upper limit of conditional formula (5A) should be set to 9.0, further 8.0, further 7.0, further 6.0, or even 5.0.
If the lower limit of conditional expression (5A) is exceeded, the focus sensitivity of the first focusing lens group becomes too high, and the precision required for the mechanism that moves the first focusing lens group becomes high, leading to increased costs. Also, in order to correct the focus change caused by the movement of the first focusing lens group, the movement amount of the second focusing lens group increases, which is undesirable because it increases the aberration fluctuation.

It is preferable that the variable magnification optical system of this embodiment satisfies the following conditional expressions (6A) and (7A).
(6A) 0.6<d1W/d2W<1.0
(7A) 3.0<d1T/d2T<30
however,
d1W: the length from the aperture stop to the optical surface of the first focusing lens group closest to the aperture stop at the short focal length end,
d2W: the length from the aperture stop to the optical surface of the second focusing lens group closest to the aperture stop at the short focal length end,
d1T: the length from the aperture stop to the optical surface of the first focusing lens group closest to the aperture stop at the long focal length end,
d2T: the length from the aperture stop to the optical surface of the second focusing lens group closest to the aperture stop at the long focal length end,
It is.

Similar to (6) and (7) described in <Aspect 1>, by satisfying conditional expressions (6A) and (7A), the off-axis aberration correction is appropriately shared between the first and second focusing lens groups, and the distances from the aperture stop of the first and second focusing lens groups are made evenly close, so that off-axis aberrations at the short focal length end can be effectively corrected and the mechanical arrangement of the optical system at the long focal length end can be appropriately performed. It is more preferable to set the upper limit of conditional expression (7A) to 20. It is also more preferable to set the lower limit of conditional expression (7A) to 4.0, further 5.0, and further 6.0.

<Aspect 4>
It is preferable that the variable magnification optical system of this embodiment satisfies the following conditional expressions (1B) and (2B).
(1B) 0.85<|f1/f2|<1
(2B) 0.03<|p2T/p1T|<30
however,
f1: focal length of the first focusing lens group,
f2: focal length of the second focusing lens group,
p1T: focus sensitivity of the first focusing lens group when focusing on infinity at the long focal length end,
p2T: focus sensitivity of the second focusing lens group when focusing on infinity at the long focal length end,
p1T=(1-m1T^2)×m1RT^2
p2T=(1-m2T^2)×m2RT^2
m1T: paraxial lateral magnification of the first focusing lens group when focusing on infinity at the long focal length end,
m1RT: paraxial lateral magnification of the optical system on the image side of the first focusing lens group when focusing on infinity at the long focal length end,
m2T: paraxial lateral magnification of the second focusing lens group when focusing on infinity at the long focal length end,
m2RT: paraxial lateral magnification of the optical system on the image side of the second focusing lens group when focusing on infinity at the long focal length end,
It is.

Conditional expressions (1B) and (2B) stipulate the ratio of focus sensitivity at the long focal length end of the first and second focusing lens groups in order to perform appropriate aberration correction when the object-side focusing lens group and the image-side focusing lens group, whichever has the greater absolute value of refractive power, are designated as the first focusing lens group, and the one with the smaller absolute value of refractive power is designated as the second focusing lens group. Note that it is desirable to simultaneously satisfy conditional expressions (1B) and (2B), but it is also possible to satisfy only one of conditional expressions (1B) and (2B).

In addition to conditional formula (1A), conditional formula (1B) stipulates that the absolute values of the refractive power of the first and second focusing lens groups are close to each other. By making the absolute values of the refractive power of the first and second focusing lens groups close to each other and preventing abrupt refraction of light rays by either of the focusing lens groups, the occurrence of aberration can be suppressed. This increases the degree of freedom of focus sensitivity at the long focal length ends of the first and second focusing lens groups. Note that when the lower limit of conditional formula (1B) is exceeded, conditional formulas (1A) and (2A) are satisfied, that is, the setting range of focus sensitivity is limited, allowing good aberration correction.

It is preferable that the variable magnification optical system of this embodiment satisfies the following conditional expression (3B).
(3B) 0.02<|p2W/p2T|<2.0
however,
p2W: focus sensitivity of the second focusing lens group when focusing on infinity at the short focal length end,
p2T: focus sensitivity of the second focusing lens group when focusing on infinity at the long focal length end,
p2W=(1-m2W^2)×m2RW^2
p2T=(1-m2T^2)×m2RT^2
m2W: paraxial lateral magnification of the second focusing lens group when focusing on infinity at the short focal length end,
m2RW: paraxial lateral magnification of the optical system on the image side of the second focusing lens group when focusing on infinity at the short focal length end,
m2T: paraxial lateral magnification of the second focusing lens group when focusing on infinity at the long focal length end,
m2RT: paraxial lateral magnification of the optical system on the image side of the second focusing lens group when focusing on infinity at the long focal length end,
It is.

It is preferable that the variable magnification optical system of this embodiment satisfies the following conditional expression (4B).
(4B) 0.7<|p1W/p1T|<7.0
however,
p1W: focus sensitivity of the first focusing lens group when focusing on infinity at the short focal length end,
p1T: focus sensitivity of the first focusing lens group when focusing on infinity at the long focal length end,
p1W=(1-m1W^2)×m1RW^2
p1T=(1-m1T^2)×m1RT^2
m1W: paraxial lateral magnification of the first focusing lens group when focusing on infinity at the short focal length extremity,
m1RW: paraxial lateral magnification of the optical system on the image side of the first focusing lens group when focusing on infinity at the short focal length end,
m1T: paraxial lateral magnification of the first focusing lens group when focusing on infinity at the long focal length end,
m1RT: paraxial lateral magnification of the optical system on the image side of the first focusing lens group when focusing on infinity at the long focal length end,
It is.

Condition (3B) defines the ratio of the focus sensitivities of the second focusing lens group at the short focal length extremity and the long focal length extremity in order to achieve good aberration correction.
If the upper limit of condition (3B) is exceeded, the focus sensitivity of the second focusing lens group at the long focal length extremity becomes too small, the amount of movement of the second focusing lens group associated with focusing increases, and aberration fluctuations become large, which is undesirable.
If the lower limit of condition (3B) is exceeded, the focus sensitivity of the second focusing lens group at the long focal length extremity becomes excessive, and the precision required for the mechanism that moves the second focusing lens group increases, leading to increased costs.

Condition (4B) defines the ratio of the focus sensitivities of the first focusing lens group at the short focal length extremity and the long focal length extremity in order to achieve good aberration correction.
If the upper limit of condition (4B) is exceeded, the focus sensitivity of the first focusing lens group at the long focal length extremity becomes too small, the amount of movement of the first focusing lens group associated with focusing increases, and aberration fluctuations become large, which is undesirable.
If the lower limit of condition (4B) is exceeded, the focus sensitivity of the first focusing lens group at the long focal length extremity becomes excessive, and the precision required for the mechanism that moves the first focusing lens group increases, leading to increased costs.

It is preferable that the variable magnification optical system of this embodiment satisfies the following conditional expression (5B).
(5B) 0.1<|p2W/p1W|<10
however,
p1W: focus sensitivity of the first focusing lens group when focusing on infinity at the short focal length end,
p2W: focus sensitivity of the second focusing lens group when focusing on infinity at the short focal length end,
p1W=(1-m1W^2)×m1RW^2
p2W=(1-m2W^2)×m2RW^2
m1W: paraxial lateral magnification of the first focusing lens group when focusing on infinity at the short focal length extremity,
m1RW: paraxial lateral magnification of the optical system on the image side of the first focusing lens group when focusing on infinity at the short focal length end,
m2W: paraxial lateral magnification of the second focusing lens group when focusing on infinity at the short focal length end,
m2RW: paraxial lateral magnification of the optical system on the image side of the second focusing lens group when focusing on infinity at the short focal length end,
It is.

Condition (5B) defines the ratio of the focusing sensitivities of the first and second focusing lens groups when focusing on an object at infinity at the short focal length extremity.
If the upper limit of conditional formula (5B) is exceeded, the focus sensitivity of the second focusing lens group becomes too high, and the precision required for the mechanism that moves the second focusing lens group becomes high, leading to increased costs. Also, in order to correct the focus change caused by the movement of the second focusing lens group, the movement amount of the first focusing lens group increases, which is undesirable because it increases the aberration fluctuation. More preferably, the upper limit of conditional formula (5B) should be set to 9.0, further 8.0, further 7.0, further 6.0, or even 5.0.
If the lower limit of conditional expression (5B) is exceeded, the focus sensitivity of the first focusing lens group becomes too high, the precision required for the mechanism that moves the first focusing lens group becomes high, leading to increased costs. Also, the amount of movement of the second focusing lens group increases in order to correct the focus change caused by the movement of the first focusing lens group, which is undesirable because it increases the aberration fluctuation.

It is preferable that the variable magnification optical system of this embodiment satisfies the following conditional expressions (6B) and (7B).
(6B) 0.6<d1W/d2W<1.0
(7B) 3.0<d1T/d2T<30
however,
d1W: the length from the aperture stop to the optical surface of the first focusing lens group closest to the aperture stop at the short focal length end,
d2W: the length from the aperture stop to the optical surface of the second focusing lens group closest to the aperture stop at the short focal length end,
d1T: the length from the aperture stop to the optical surface of the first focusing lens group closest to the aperture stop at the long focal length end,
d2T: the length from the aperture stop to the optical surface of the second focusing lens group closest to the aperture stop at the long focal length end,
It is.

Similar to (6) and (7) described in <Aspect 1>, by satisfying conditional expressions (6B) and (7B), the correction of off-axis aberrations is appropriately shared between the first and second focusing lens groups, and the distances of the first and second focusing lens groups from the aperture stop are made uniformly close, so that off-axis aberrations at the short focal length end can be effectively corrected and the mechanical arrangement of the optical system at the long focal length end can be appropriately performed. It is more preferable to set the upper limit of conditional expression (7B) to 20. It is also more preferable to set the lower limit of conditional expression (7B) to 4.0, further 5.0, or even 6.0.

Specific numerical examples 1 to 6, 9 to 11 and comparative examples (reference examples) 7 and 8 are shown. In the longitudinal aberration diagrams and lateral aberration diagrams and tables, d-line, g-line, and C-line are aberrations for each wavelength, S is sagittal, M is meridional, FNO. is F-number, f is focal length, W is half angle of view, Y is image height, BF is back focus, L is lens total length, R is radius of curvature, D is lens thickness or lens spacing, N(d) is refractive index for d-line, and ν(d) is Abbe number for d-line. D0 indicates object distance (distance from the front surface to the object) at a close distance. The back focus is the distance from the surface closest to the image side of the entire lens system to the designed image surface, and indicates the value of the air-equivalent length not including a cover glass or the like between the surface closest to the image side of the entire lens system and the designed image surface. F-number, focal length, magnification, half angle of view, image height, back focus, total lens length, and lens distance D, which changes with zooming and focusing, are shown in the order of short focal length end - intermediate focal length - long focal length end. The unit of length is [mm].
A rotationally symmetric aspheric surface is defined by the following equation:
x=cy2/[1+[1-(1+K)c2y2]1/2]+A4y4+A6y6+A8y8 +A10y10+A12y12...
(where c is the curvature (1/r), y is the height from the optical axis, K is the cone coefficient, A4, A6, A8,
.... are aspheric coefficients of each order)

[Numerical Example 1]
14 to 23 and Tables 1 to 4 show the variable magnification optical system of Numerical Example 1. FIGS. 14 and 15 are diagrams showing the lens configurations at the short focal length end and the long focal length end when focusing on infinity. FIGS. 16 and 17 are diagrams showing longitudinal aberration and lateral aberration when focusing on infinity at the short focal length end. FIGS. 18 and 19 are diagrams showing longitudinal aberration and lateral aberration when focusing on infinity at the long focal length end. FIGS. 20 and 21 are diagrams showing longitudinal aberration and lateral aberration when focusing on a close distance at the short focal length end. FIGS. 22 and 23 are diagrams showing longitudinal aberration and lateral aberration when focusing on a close distance at the long focal length end. Table 1 shows surface data, Table 2 shows aspheric surface data, Table 3 shows various data, and Table 4 shows lens group data.

The variable magnification optical system of Numerical Example 1 is composed of, in order from the object side, a first lens group G1 with positive refractive power, a second lens group G2 with negative refractive power, a third lens group G3 with negative refractive power, an aperture stop AST, a fourth lens group G4 with positive refractive power, a fifth lens group G5 with negative refractive power, and a sixth lens group G6 with positive refractive power. A cover glass CG is disposed between the sixth lens group G6 and the image surface (IM in Figures 3 to 13).

The first lens group G1, the second lens group G2, and the third lens group G3 constitute an object-side lens group G _ob . The first lens group G1 constitutes an object-side first lens group G _ob1 , and the second lens group G2 and the third lens group G3 constitute an object-side second lens group G _ob2 .

The fourth lens group G4, the fifth lens group G5, and the sixth lens group G6 constitute an image side lens group G _im . The fourth lens group G4 constitutes an image side first lens group G _im1 having a positive refractive power, the fifth lens group G5 constitutes an image side intermediate lens group G _im2 , and the sixth lens group G6 constitutes an image side final lens group G _L.

The third lens group G3, which is at least a part of the object-side second lens group G _ob2 , constitutes an object-side focusing lens group FL _ob that moves in the optical axis direction when focusing from infinity to a close distance. The fifth lens group G5, which is at least a part of the image-side intermediate lens group G _im2 , constitutes an image-side focusing lens group FL _im that moves in the optical axis direction when focusing from infinity to a close distance.

The first lens group G1 is composed of, in order from the object side, a biconcave negative lens 11A, a biconvex positive lens 12A, and a positive meniscus lens 13A that is convex toward the object side. The biconcave negative lens 11A and the biconvex positive lens 12A are cemented together.

The second lens group G2 is composed of, in order from the object side, a negative meniscus lens 21A convex toward the object side, a biconcave negative lens 22A, and a positive meniscus lens 23A convex toward the object side. The negative meniscus lens 21A has an aspheric surface on the object side.

The third lens group G3 is composed of, in order from the object side, a biconcave negative lens 31A and a biconvex positive lens 32A. The biconcave negative lens 31A has an aspheric surface on the object side. The biconcave negative lens 31A and the biconvex positive lens 32A are cemented together.

The fourth lens group G4 is composed of, in order from the object side, a biconvex positive lens 41A, a negative meniscus lens 42A convex toward the object side, a biconvex positive lens 43A, and a positive meniscus lens 44A convex toward the object side. The negative meniscus lens 42A and the biconvex positive lens 43A are cemented together.

The fifth lens group G5 is composed of, in order from the object side, a biconcave negative lens 51A and a positive meniscus lens 52A that is convex toward the object side. The biconcave negative lens 51A has an aspheric surface on the object side. The biconcave negative lens 51A and the positive meniscus lens 52A are cemented together.

The sixth lens group G6 is composed of, in order from the object side, a biconvex positive lens 61A, a biconcave negative lens 62A, a plano-convex positive lens 63A convex toward the object side, a biconcave negative lens 64A, and a biconvex positive lens 65A. The biconvex positive lens 61A has aspheric surfaces on both sides. The biconcave negative lens 64A and the biconvex positive lens 65A are cemented together.

(Table 1)
[Face data]
Magnification ratio: 3.57
Surface number RDN(d) ν(d)
1 -1915.234 2.000 2.10420 17.0
2 341.346 4.000 1.90366 31.3
3 -4611.553 0.150
4 60.151 5.000 1.90043 37.4
5 106.070 D5
6* 48.826 1.300 1.80139 45.5
7 20.705 8.521
8 -92.232 1.000 1.75500 52.3
9 48.288 1.000
10 49.459 3.000 2.10420 17.0
11 149.797 D11
12* -45.440 1.000 1.80139 45.5
13 185.987 2.000 1.79504 28.7
14 -133.322 D14
15 aperture INFINITY 1.150
16 137.550 3.500 1.67790 55.3
17 -73.251 0.100
18 40.641 1.100 2.10420 17.0
19 27.460 6.500 1.49700 81.7
20 -178.135 0.100
21 39.267 2.600 1.69680 55.5
22 81.022 D22
23* -42.640 1.000 1.85135 40.1
24 49.622 2.500 1.98613 16.5
25 1014.959 D25
26* 41.110 6.000 1.76802 49.2
27* -46.464 0.628
28 -199.295 1.000 1.79504 28.7
29 29.712 0.751
30 39.046 4.000 1.49700 81.7
31 INFINITY 0.430
32 -267.036 1.000 1.88300 40.8
33 37.232 7.000 1.57501 41.5
34 -47.690 D34
35 INFINITY 1.500 1.51633 64.1
36 INFINITY -
* denotes a rotationally symmetric aspheric surface.
(Table 2)
[Aspheric data]
Surface number K A4 A6 A8 A10
6 0.000 0.3331E-05 0.3068E-09 0.5417E-12 0.2928E-14
12 0.000 -0.4940E-06 0.1794E-09 0.0000E+00 0.0000E+00
23 0.000 0.6859E-05 0.4322E-08 0.0000E+00 0.0000E+00
26 0.000 -0.3872E-05 0.1217E-07 -0.3689E-10 0.1297E-12
27 0.000 0.1089E-04 0.2657E-08 -0.2609E-10 0.1146E-12
(Table 3)
[Various data]
Infinity Near distance
Wide-angle Mid-range Telephoto Wide-angle Mid-range Telephoto
FNO. 4.1 4.1 4.1 - - -
f 24.60 45.01 87.75 - - -
Magnification - - - -0.078 -0.133 -0.268
W 42.4 25.4 13.7 - - -
Y 21.64 21.64 21.64 21.64 21.64 21.64
BF 39.66 59.14 88.40 39.66 59.14 88.40
L 166.87 184.74 222.33 166.87 184.74 222.33
D0 - - - 281.083 272.083 221.083
D5 0.800 16.291 34.747 0.800 16.291 34.747
D11 7.722 12.638 9.559 3.693 8.558 3.693
D14 28.231 10.124 2.806 32.260 14.204 8.672
D22 6.548 11.640 16.880 6.266 10.953 15.560
D25 15.067 6.067 1.100 15.349 6.755 2.420
D34 37.670 57.153 86.408 37.670 57.153 86.408
(Table 4)
[Lens group data]
Group starting plane focal length
1 1 171.04
2 6 -31.50
3 12 -86.72
4 16 32.72
5 23 -54.87
6 26 56.24

[Numerical Example 2]
24 to 33 and Tables 5 to 8 show the variable magnification optical system of Numerical Example 2. FIGS. 24 and 25 are diagrams showing the lens configurations at the short focal length end and the long focal length end when focusing on infinity. FIGS. 26 and 27 are diagrams showing longitudinal aberration and lateral aberration when focusing on infinity at the short focal length end. FIGS. 28 and 29 are diagrams showing longitudinal aberration and lateral aberration when focusing on infinity at the long focal length end. FIGS. 30 and 31 are diagrams showing longitudinal aberration and lateral aberration when focusing on a close distance at the short focal length end. FIGS. 32 and 33 are diagrams showing longitudinal aberration and lateral aberration when focusing on a close distance at the long focal length end. Table 5 shows surface data, Table 6 shows aspheric surface data, Table 7 shows various data, and Table 8 shows lens group data.

The lens configuration of the variable magnification optical system of Numerical Example 2 is similar to the lens configuration of the variable magnification optical system of Numerical Example 1, except for the following points.
(1) The negative lens 11A in the first lens group G1 is a negative meniscus lens that is convex toward the object side.
(2) The negative lens 62A in the sixth lens group G6 is a negative meniscus lens that is convex toward the object side.

(Table 5)
[Face data]
Magnification ratio: 3.57
Surface number RDN(d) ν(d)
1 3831.171 2.000 2.10420 17.0
2 198.323 4.000 1.90366 31.3
3 -2565.529 0.150
4 73.888 5.000 1.90043 37.4
5 144.384 D5
6* 62.554 1.300 1.80139 45.5
7 25.882 7.552
8 -85.385 1.000 1.75500 52.3
9 30.517 1.146
10 39.970 3.000 2.10420 17.0
11 98.379 D11
12* -130.348 1.000 1.80139 45.5
13 95.771 2.000 1.79504 28.7
14 -7493.366 D14
15 aperture INFINITY 1.150
16 60.570 3.500 1.67790 55.3
17 -285.708 0.100
18 38.755 1.100 2.10420 17.0
19 27.844 6.500 1.49700 81.7
20 -114.420 0.100
21 45.292 2.600 1.69680 55.5
22 131.589 D22
23* -36.590 1.000 1.85135 40.1
24 38.724 2.500 1.98613 16.5
25 104.529 D25
26* 40.682 6.000 1.76802 49.2
27* -51.976 0.300
28 282.714 1.000 1.79504 28.7
29 30.249 0.684
30 39.254 4.000 1.49700 81.7
31 INFINITY 3.068
32 -179.158 1.000 1.88300 40.8
33 36.265 7.000 1.57501 41.5
34 -42.113 D34
35 INFINITY 1.500 1.51633 64.1
36 INFINITY -
* denotes a rotationally symmetric aspheric surface.
(Table 6)
[Aspheric data]
Surface number K A4 A6 A8 A10
6 0.000 0.2585E-05 0.1254E-08 -0.1906E-11 0.5999E-14
12 0.000 -0.1877E-06 0.9698E-09 0.0000E+00 0.0000E+00
23 0.000 0.9828E-05 0.1526E-08 0.0000E+00 0.0000E+00
26 0.000 -0.4278E-05 0.1221E-07 -0.2431E-10 0.6786E-13
27 0.000 0.1152E-04 0.2082E-08 -0.1153E-10 0.4971E-13
(Table 7)
[Various data]
Infinity Near distance
Wide-angle Mid-range Telephoto Wide-angle Mid-range Telephoto
FNO. 4.1 4.1 4.1 - - -
f 24.60 45.00 87.75 - - -
Magnification - - - -0.078 -0.132 -0.257
W 42.4 25.4 13.7 - - -
Y 21.64 21.64 21.64 21.64 21.64 21.64
BF 39.73 58.78 87.73 39.73 58.78 87.73
L 167.17 185.75 223.55 167.17 185.75 223.55
D0 - - - 281.083 272.083 221.083
D5 0.800 17.809 38.567 0.800 17.809 38.567
D11 9.376 15.751 13.381 2.746 8.346 2.746
D14 29.334 9.044 1.500 35.965 16.448 12.136
D22 6.237 8.502 10.330 6.145 7.877 8.998
D25 11.434 5.605 1.777 11.526 6.230 3.109
D34 37.738 56.795 85.744 37.738 56.795 85.744
(Table 8)
[Lens group data]
Group starting plane focal length
1 1 172.95
2 6 -27.29
3 12 -163.74
4 16 30.07
5 23 -33.86
6 26 45.00

[Numerical Example 3]
34 to 43 and Tables 9 to 12 show the variable magnification optical system of Numerical Example 3. FIGS. 34 and 35 are diagrams showing the lens configurations at the short focal length end and the long focal length end when focusing on infinity. FIGS. 36 and 37 are diagrams showing longitudinal aberration and lateral aberration when focusing on infinity at the short focal length end. FIGS. 38 and 39 are diagrams showing longitudinal aberration and lateral aberration when focusing on infinity at the long focal length end. FIGS. 40 and 41 are diagrams showing longitudinal aberration and lateral aberration when focusing on a close distance at the short focal length end. FIGS. 42 and 43 are diagrams showing longitudinal aberration and lateral aberration when focusing on a close distance at the long focal length end. Table 9 shows surface data, Table 10 shows aspheric surface data, Table 11 shows various data, and Table 12 shows lens group data.

The lens configuration of the variable magnification optical system of Numerical Example 3 is similar to the lens configuration of the variable magnification optical system of Numerical Example 1, except for the following points.
(1) The positive lens 23A of the second lens group G2 is a biconvex positive lens.
(2) The positive lens 52A in the fifth lens group G5 is a biconvex positive lens.
(3) The negative lens 64A in the sixth lens group G6 is a negative meniscus lens that is convex toward the object side.

(Table 9)
[Face data]
Magnification ratio: 3.57
Surface number RDN(d) ν(d)
1 -1587.534 2.000 2.10420 17.0
2 281.437 4.000 1.90366 31.3
3 -1013.279 0.150
4 58.712 5.000 1.90043 37.4
5 103.642 D5
6* 57.344 1.300 1.80139 45.5
7 19.690 9.339
8 -56.799 1.000 1.75500 52.3
9 181.449 1.354
10 81.595 3.000 2.10420 17.0
11 -633.249 D11
12* -45.869 1.000 1.80139 45.5
13 87.563 2.000 1.79504 28.7
14 -336.920 D14
15 aperture INFINITY 2.114
16 163.059 3.500 1.67790 55.3
17 -67.459 0.100
18 44.920 1.100 2.10420 17.0
19 29.355 6.500 1.49700 81.7
20 -108.647 0.200
21 32.923 2.600 1.69680 55.5
22 59.241 D22
23* -42.074 1.000 1.85135 40.1
24 57.246 2.500 1.98613 16.5
25 -947.963 D25
26* 59.216 6.000 1.76802 49.2
27* -47.897 0.521
28 -247.180 1.000 1.79504 28.7
29 32.705 0.361
30 37.922 4.000 1.49700 81.7
31 INFINITY 0.200
32 298.740 1.000 1.88300 40.8
33 28.747 7.000 1.57501 41.5
34 -76.244 D34
35 INFINITY 1.500 1.51633 64.1
36 INFINITY -
* denotes a rotationally symmetric aspheric surface.
(Table 10)
[Aspheric data]
Surface number K A4 A6 A8 A10
6 0.000 0.4323E-05 -0.2701E-08 0.7877E-11 -0.8244E-14
12 0.000 -0.9991E-07 0.2492E-08 0.0000E+00 0.0000E+00
23 0.000 0.6908E-05 0.4743E-08 0.0000E+00 0.0000E+00
26 0.000 -0.2617E-05 0.2233E-08 0.4981E-10 -0.9297E-13
27 0.000 0.9366E-05 -0.3690E-08 0.7196E-10 -0.1366E-12
(Table 11)
[Various data]
Infinity Near distance
Wide-angle Mid-range Telephoto Wide-angle Mid-range Telephoto
FNO. 4.1 4.1 4.1 - - -
f 24.60 45.01 87.75 - - -
Magnification - - - -0.078 -0.137 -0.263
W 42.4 25.3 13.6 - - -
Y 21.64 21.64 21.64 21.64 21.64 21.64
BF 39.66 61.12 84.82 39.66 61.12 84.82
L 168.07 181.33 219.06 168.07 181.33 219.06
D0 - - - 281.083 272.083 221.083
D5 0.800 11.200 34.735 0.800 11.200 34.735
D11 5.892 11.093 8.091 2.871 7.878 2.871
D14 29.963 11.125 4.061 32.984 14.339 9.281
D22 5.674 11.147 15.907 5.513 10.516 14.381
D25 15.735 5.296 1.100 15.896 5.927 2.626
D34 37.670 59.132 82.828 37.670 59.132 82.828
(Table 12)
[Lens group data]
Group starting plane focal length
1 1 153.85
2 6 -36.14
3 12 -66.16
4 16 31.71
5 23 -59.60
6 26 69.27

[Numerical Example 4]
44 to 53 and Tables 13 to 16 show the variable magnification optical system of Numerical Example 4. Figs. 44 and 45 are diagrams showing the lens configurations at the short focal length end and the long focal length end when focusing on infinity. Figs. 46 and 47 are diagrams showing longitudinal aberration and lateral aberration when focusing on infinity at the short focal length end. Figs. 48 and 49 are diagrams showing longitudinal aberration and lateral aberration when focusing on infinity at the long focal length end. Figs. 50 and 51 are diagrams showing longitudinal aberration and lateral aberration when focusing on a close distance at the short focal length end. Figs. 52 and 53 are diagrams showing longitudinal aberration and lateral aberration when focusing on a close distance at the long focal length end. Table 13 shows surface data, Table 14 shows aspherical surface data, Table 15 shows various data, and Table 16 shows lens group data.

The lens configuration of the variable magnification optical system of Numerical Example 4 is similar to the lens configuration of the variable magnification optical system of Numerical Example 1, except for the following points.
(1) The positive lens 52A in the fifth lens group G5 is a biconvex positive lens.

(Table 13)
[Face data]
Magnification ratio: 3.57
Surface number RDN(d) ν(d)
1 -2621.594 2.000 2.10420 17.0
2 268.665 4.000 1.90366 31.3
3 -2719.336 0.150
4 54.731 5.000 1.90043 37.4
5 97.495 D5
6* 55.629 1.300 1.80139 45.5
7 20.140 8.847
8 -72.718 1.000 1.75500 52.3
9 79.964 1.000
10 69.299 3.000 2.10420 17.0
11 4161.031 D11
12* -45.985 1.000 1.80139 45.5
13 94.748 2.000 1.79504 28.7
14 -288.385 D14
15 aperture INFINITY 1.285
16 198.641 3.500 1.67790 55.3
17 -62.272 0.100
18 40.775 1.100 2.10420 17.0
19 27.281 6.500 1.49700 81.7
20 -208.894 0.100
21 36.142 2.600 1.69680 55.5
22 70.900 D22
23* -43.280 1.000 1.85135 40.1
24 52.913 2.500 1.98613 16.5
25 -17721.023 D25
26* 43.524 6.000 1.76802 49.2
27* -46.328 0.746
28 -180.172 1.000 1.79504 28.7
29 30.487 0.680
30 39.251 4.000 1.49700 81.7
31 INFINITY 0.200
32 -1206.007 1.000 1.88300 40.8
33 33.629 7.000 1.57501 41.5
34 -55.835 D34
35 INFINITY 1.500 1.51633 64.1
36 INFINITY -
* denotes a rotationally symmetric aspheric surface.
(Table 14)
[Aspheric data]
Surface number K A4 A6 A8 A10
6 0.000 0.4009E-05 -0.1360E-08 0.3155E-11 -0.1479E-14
12 0.000 -0.1602E-06 0.1707E-08 0.0000E+00 0.0000E+00
23 0.000 0.6546E-05 0.4689E-08 0.0000E+00 0.0000E+00
26 0.000 -0.3200E-05 0.8083E-08 -0.9438E-11 0.6900E-13
27 0.000 0.1037E-04 0.2743E-09 0.3104E-11 0.4601E-13
(Table 15)
[Various data]
Infinity Near distance
Wide-angle Mid-range Telephoto Wide-angle Mid-range Telephoto
FNO. 4.1 4.1 4.1 - - -
f 24.60 45.02 87.75 - - -
Magnification - - - -0.077 -0.137 -0.273
W 42.4 25.4 13.7 - - -
Y 21.64 21.64 21.64 21.64 21.64 21.64
BF 39.66 60.88 89.31 39.66 60.88 89.31
L 166.67 180.65 218.13 166.67 180.65 218.13
D0 - - - 281.083 272.083 221.083
D5 0.800 11.300 29.581 0.800 11.300 29.581
D11 6.436 11.120 8.970 2.864 7.828 4.089
D14 28.672 10.890 3.524 32.244 14.182 8.405
D22 6.108 11.413 16.524 5.660 10.732 15.118
D25 15.874 5.926 1.100 16.323 6.607 2.506
D34 37.670 58.893 87.322 37.670 58.893 87.322
(Table 16)
[Lens group data]
Group starting plane focal length
1 1 147.41
2 6 -34.35
3 12 -68.22
4 16 32.77
5 23 -58.69
6 26 58.78

[Numerical Example 5]
54 to 63 and Tables 17 to 20 show the variable magnification optical system of Numerical Example 5. Figs. 54 and 55 are diagrams showing the lens configurations at the short focal length end and the long focal length end when focusing on infinity. Figs. 56 and 57 are diagrams showing longitudinal and lateral aberrations at the short focal length end when focusing on infinity. Figs. 58 and 59 are diagrams showing longitudinal and lateral aberrations at the long focal length end when focusing on infinity. Figs. 60 and 61 are diagrams showing longitudinal and lateral aberrations at the short focal length end when focusing on a close distance. Figs. 62 and 63 are diagrams showing longitudinal and lateral aberrations at the long focal length end when focusing on a close distance. Table 17 shows surface data, Table 18 shows aspherical surface data, Table 19 shows various data, and Table 20 shows lens group data.

The lens configuration of the variable magnification optical system of Numerical Example 5 is similar to the lens configuration of the variable magnification optical system of Numerical Example 1.

(Table 17)
[Face data]
Magnification ratio: 3.57
Surface number RDN(d) ν(d)
1 -4963.048 2.000 2.10420 17.0
2 295.813 4.000 1.90366 31.3
3 4753.337 0.150
4 58.010 5.000 1.90043 37.4
5 103.319 D5
6* 48.480 1.300 1.80139 45.5
7 20.679 8.306
8 -100.470 1.000 1.75500 52.3
9 46.201 1.000
10 47.918 3.000 2.10420 17.0
11 133.289 D11
12* -46.724 1.000 1.80139 45.5
13 144.598 2.000 1.79504 28.7
14 -144.754 D14
15 aperture INFINITY 1.150
16 136.660 3.500 1.67790 55.3
17 -74.193 0.100
18 39.993 1.100 2.10420 17.0
19 27.245 6.500 1.49700 81.7
20 -185.521 0.100
21 39.981 2.600 1.69680 55.5
22 83.451 D22
23* -41.120 1.000 1.85135 40.1
24 51.439 2.500 1.98613 16.5
25 1654.803 D25
26* 40.265 6.000 1.76802 49.2
27* -47.393 0.581
28 -238.007 1.000 1.79504 28.7
29 29.365 0.826
30 39.620 4.000 1.49700 81.7
31 INFINITY 0.698
32 -515.005 1.000 1.88300 40.8
33 35.334 7.000 1.57501 41.5
34 -51.048 D34
35 INFINITY 1.500 1.51633 64.1
36 INFINITY -
* denotes a rotationally symmetric aspheric surface.
(Table 18)
[Aspheric data]
Surface number K A4 A6 A8 A10
6 0.000 0.3339E-05 0.1581E-10 0.1807E-11 0.1372E-14
12 0.000 -0.4831E-06 0.3692E-09 0.0000E+00 0.0000E+00
23 0.000 0.7024E-05 0.4607E-08 0.0000E+00 0.0000E+00
26 0.000 -0.3510E-05 0.1161E-07 -0.3199E-10 0.1171E-12
27 0.000 0.1096E-04 0.1818E-08 -0.1909E-10 0.9592E-13
(Table 19)
[Various data]
Infinity Near distance
Wide-angle Mid-range Telephoto Wide-angle Mid-range Telephoto
FNO. 4.1 4.1 4.1 - - -
f 24.60 45.00 87.75 - - -
Magnification - - - -0.078 -0.135 -0.274
W 42.4 25.4 13.7 - - -
Y 21.64 21.64 21.64 21.64 21.64 21.64
BF 39.75 59.99 89.40 39.75 59.99 89.40
L 166.37 182.50 218.85 166.37 182.50 218.85
D0 - - - 281.083 272.083 221.083
D5 0.800 13.854 31.063 0.800 13.854 31.063
D11 7.122 12.591 8.721 2.824 8.575 2.824
D14 28.559 9.908 3.068 32.856 13.924 8.965
D22 6.168 11.219 16.585 5.809 10.562 15.271
D25 15.051 6.024 1.100 15.410 6.682 2.414
D34 37.764 57.998 87.409 37.764 57.998 87.409
(Table 20)
[Lens group data]
Group starting plane focal length
1 1 164.94
2 6 -31.31
3 12 -86.61
4 16 32.72
5 23 -53.56
6 26 54.79

[Numerical Example 6]
64 to 73 and Tables 21 to 24 show the variable magnification optical system of Numerical Example 6. Figs. 64 and 65 are diagrams showing the lens configurations at the short focal length end and the long focal length end when focusing on infinity. Figs. 66 and 67 are diagrams showing longitudinal aberration and lateral aberration when focusing on infinity at the short focal length end. Figs. 68 and 69 are diagrams showing longitudinal aberration and lateral aberration when focusing on infinity at the long focal length end. Figs. 70 and 71 are diagrams showing longitudinal aberration and lateral aberration when focusing on a close distance at the short focal length end. Figs. 72 and 73 are diagrams showing longitudinal aberration and lateral aberration when focusing on a close distance at the long focal length end. Table 21 shows surface data, Table 22 shows aspheric surface data, Table 23 shows various data, and Table 24 shows lens group data.

The lens configuration of the variable magnification optical system of Numerical Example 6 is similar to the lens configuration of the variable magnification optical system of Numerical Example 1, except for the following points.
(1) In the first lens group G1, the negative lens 11A is a negative meniscus lens convex toward the object side, and the positive lens 12A is a positive meniscus lens convex toward the object side.
(2) In the sixth lens group G6, the negative lens 62A is a negative meniscus lens convex toward the object side, the positive lens 63A is a biconvex positive lens, and the negative lens 64A is a negative meniscus lens convex toward the object side.

(Table 21)
[Face data]
Magnification ratio: 3.57
Surface number RDN(d) ν(d)
1 3057.058 2.000 2.10420 17.0
2 230.063 4.000 1.90366 31.3
3 5144.270 0.150
4 76.308 5.000 1.90043 37.4
5 146.206 D5
6* 57.466 1.300 1.80139 45.5
7 26.040 7.595
8 -92.991 1.000 1.75500 52.3
9 29.771 1.000
10 36.927 3.000 2.10420 17.0
11 78.490 D11
12* -82.637 1.000 1.80139 45.5
13 159.049 2.000 1.79504 28.7
14 -230.863 D14
15 aperture INFINITY 1.150
16 73.063 3.500 1.67790 55.3
17 -150.777 0.100
18 38.266 1.100 2.10420 17.0
19 27.023 6.500 1.49700 81.7
20 -130.223 0.100
21 50.438 2.600 1.69680 55.5
22 198.813 D22
23* -35.922 1.000 1.85135 40.1
24 36.653 2.500 1.98613 16.5
25 113.299 D25
26* 36.918 6.000 1.76802 49.2
27* -55.580 0.401
28 376.434 1.000 1.79504 28.7
29 29.361 1.295
30 50.695 4.000 1.49700 81.7
31 -165.933 1.432
32 2407.389 1.000 1.88300 40.8
33 31.034 7.000 1.57501 41.5
34 -58.610 D34
35 INFINITY 1.500 1.51633 64.1
36 INFINITY -
* denotes a rotationally symmetric aspheric surface.
(Table 22)
[Aspheric data]
Surface number K A4 A6 A8 A10
6 0.000 0.2471E-05 0.1435E-08 -0.1480E-11 0.5324E-14
12 0.000 -0.3511E-06 0.1159E-08 0.0000E+00 0.0000E+00
23 0.000 0.9516E-05 0.2770E-08 0.0000E+00 0.0000E+00
26 0.000 -0.3487E-05 0.9016E-08 -0.1666E-10 0.8347E-13
27 0.000 0.1081E-04 -0.2269E-09 -0.6259E-11 0.6792E-13
(Table 23)
[Various data]
Infinity Near distance
Wide-angle Mid-range Telephoto Wide-angle Mid-range Telephoto
FNO. 4.1 4.1 4.1 - - -
f 24.60 45.01 87.75 - - -
Magnification - - - -0.078 -0.133 -0.258
W 42.4 25.4 13.7 - - -
Y 21.64 21.64 21.64 21.64 21.64 21.64
BF 40.01 59.24 87.78 40.01 59.24 87.78
L 169.10 186.25 227.36 169.10 186.25 227.36
D0 - - - 281.083 272.083 221.083
D5 0.800 17.069 40.675 0.800 17.069 40.675
D11 10.477 16.139 13.901 3.866 9.011 3.866
D14 29.123 8.913 1.500 35.733 16.042 11.536
D22 7.009 9.912 12.557 6.899 9.284 11.318
D25 12.447 5.744 1.719 12.557 6.373 2.958
D34 38.025 57.250 85.790 38.025 57.250 85.790
(Table 24)
[Lens group data]
Group starting plane focal length
1 1 194.54
2 6 -27.89
3 12 -160.31
4 16 30.42
5 23 -34.47
6 26 45.48

[ Comparative Example (Reference Example) 7 ]
74 to 83 and Tables 25 to 28 show the variable magnification optical system of Comparative Example (Reference Example) 7. Figs. 74 and 75 are diagrams showing the lens configurations at the short focal length end and the long focal length end when focusing on infinity. Figs. 76 and 77 are diagrams showing longitudinal and lateral aberrations at the short focal length end when focusing on infinity. Figs. 78 and 79 are diagrams showing longitudinal and lateral aberrations at the long focal length end when focusing on infinity. Figs. 80 and 81 are diagrams showing longitudinal and lateral aberrations at the short focal length end when focusing on a close distance. Figs. 82 and 83 are diagrams showing longitudinal and lateral aberrations at the long focal length end when focusing on a close distance. Table 25 shows surface data, Table 26 shows aspherical surface data, Table 27 shows various data, and Table 28 shows lens group data.

The variable power optical system of the comparative example (reference example) 7 is composed of, in order from the object side, a first lens group G1 with positive refractive power, a second lens group G2 with negative refractive power, a third lens group G3 with positive refractive power, a fourth lens group G4 with negative refractive power, and a fifth lens group G5 with positive refractive power. The third lens group G3 is composed of, in order from the object side, a third A lens group G3A with positive refractive power, an aperture stop AST, and a third B lens group G3B with positive refractive power. A cover glass CG is disposed between the fifth lens group G5 and the image surface (IM in FIG. 3 to FIG. 13).

The first lens group G1, the second lens group G2, and the third lens group G3A constitute an object-side lens group G _ob . The first lens group G1 constitutes an object-side first lens group G _ob1 , and the second lens group G2 constitutes an object-side second lens group G _ob2 .

The 3B lens group G3B, the 4th lens group G4, and the 5th lens group G5 constitute an image side lens group G _im . The 3B lens group G3B constitutes an image side first lens group G _im1 having a positive refractive power, the 4th lens group G4 constitutes an image side intermediate lens group G _im2 , and the 5th lens group G5 constitutes an image side final lens group G _L.

The second lens group G2, which is at least a part of the object-side second lens group G _ob2 , constitutes an object-side focusing lens group FL _ob that moves in the optical axis direction when focusing from infinity to a close distance. The fourth lens group G4, which is at least a part of the image-side intermediate lens group G _im2 , constitutes an image-side focusing lens group FL _im that moves in the optical axis direction when focusing from infinity to a close distance.

The first lens group G1 is composed of, in order from the object side, a negative meniscus lens 11B convex toward the object side and a biconvex positive lens 12B. The biconvex positive lens 12B has an aspheric surface on the image side. The negative meniscus lens 11B and the biconvex positive lens 12B are cemented together.

The second lens group G2 is composed of, in order from the object side, a biconcave negative lens 21B, a biconcave negative lens 22B, and a positive meniscus lens 23B that is convex toward the object side. The biconcave negative lens 22B has an aspheric surface on the object side.

The third A lens group G3A is composed of, in order from the object side, a positive meniscus lens 31B convex toward the object side, a negative meniscus lens 32B convex toward the object side, and a biconvex positive lens 33B. The biconvex positive lens 33B has an aspheric surface on the image side. The negative meniscus lens 32B and the biconvex positive lens 33B are cemented together.

The third lens group G3B is composed of, in order from the object side, a biconvex positive lens 34B and a negative meniscus lens 35B that is convex toward the image side. The biconvex positive lens 34B has an aspheric surface on the object side. The biconvex positive lens 34B and the negative meniscus lens 35B are cemented together.

The fourth lens group G4 is composed of, in order from the object side, a negative meniscus lens 41B convex toward the object side and a biconcave negative lens 42B.

The fifth lens group G5 is composed of a biconvex positive lens 51B. The biconvex positive lens 51B has an aspheric surface on the image side.

(Table 25)
[Face data]
Magnification ratio: 4.69
Surface number RDN(d) ν(d)
1 39.606 1.200 1.84666 23.8
2 25.127 8.000 1.72916 54.7
3* -356.458 D3
4 -60.992 0.900 1.91082 35.2
5 13.522 2.634
6* -42.338 1.200 1.69400 56.3
7 24.761 0.150
8 20.286 2.150 1.94595 18.0
9 136.531 D9
10 15.507 2.900 1.67270 32.2
11 69.100 0.100
12 27.265 0.600 1.90366 31.3
13 11.100 3.650 1.52500 70.3
14* -129.604 1.687
15 aperture INFINITY 3.500
16* 21.390 4.000 1.50670 70.5
17 -15.349 0.600 1.80518 25.5
18 -23.546 D18
19 32.364 0.600 1.83481 42.7
20 13.485 1.826
21 -29.972 0.600 1.61800 63.4
22 90.862 D22
23 19.953 7.000 1.52500 70.3
24* -54.432 D24
25 INFINITY 2.000 1.51633 64.1
26 INFINITY -
* denotes a rotationally symmetric aspheric surface.
(Table 26)
[Aspheric data]
Surface number K A4 A6 A8 A10
3 0.000 0.1466E-05 -0.3854E-09 -0.4997E-12 -0.3519E-15
6 0.000 0.1891E-04 0.1204E-06 0.0000E+00 0.0000E+00
14 0.000 0.3726E-04 0.1658E-06 0.0000E+00 0.0000E+00
16 0.000 -0.3682E-04 -0.3794E-07 0.0000E+00 0.0000E+00
24 0.000 0.4414E-04 -0.4717E-07 0.0000E+00 0.0000E+00
(Table 27)
[Various data]
Infinity Near distance
Wide-angle Mid-range Telephoto Wide-angle Mid-range Telephoto
FNO. 3.4 4.5 5.6 - - -
f 18.54 40.00 87.00 - - -
Magnification - - - -0.057 -0.084 -0.115
W 32.0 14.5 6.7 - - -
Y 10.81 10.81 10.81 10.81 10.81 10.81
BF 13.30 13.30 13.30 13.30 13.30 13.30
L 102.98 103.97 104.69 102.98 103.97 104.70
D0 - - - 300.000 300.000 300.000
D3 4.096 14.716 23.799 4.052 9.603 13.962
D9 23.664 10.852 1.000 23.707 15.965 10.837
D18 3.059 7.183 11.598 3.333 5.842 8.474
D22 14.881 13.936 11.019 14.606 15.276 14.143
D24 10.981 10.981 10.981 10.981 10.981 10.981
(Table 28)
[Lens group data]
Group starting plane focal length
1 1 53.69
2 4 -11.43
3 10 16.96
4 19 -15.45
5 23 28.74

[ Comparative Example (Reference Example) 8 ]
84 to 93 and Tables 29 to 32 show the variable magnification optical system of Comparative Example (Reference Example) 8. Figs. 84 and 85 are diagrams showing the lens configurations at the short focal length end and the long focal length end when focusing on infinity. Figs. 86 and 87 are diagrams showing longitudinal and lateral aberrations at the short focal length end when focusing on infinity. Figs. 88 and 89 are diagrams showing longitudinal and lateral aberrations at the long focal length end when focusing on infinity. Figs. 90 and 91 are diagrams showing longitudinal and lateral aberrations at the short focal length end when focusing on a close distance. Figs. 92 and 93 are diagrams showing longitudinal and lateral aberrations at the long focal length end when focusing on a close distance. Table 29 shows surface data, Table 30 shows aspherical surface data, Table 31 shows various data, and Table 32 shows lens group data.

The variable power optical system of the comparative example (reference example) 8 is composed of, in order from the object side, a first lens group G1 with negative refractive power, a second lens group G2 with negative refractive power, a third lens group G3 with positive refractive power, a fourth lens group G4 with negative refractive power, and a fifth lens group G5 with positive refractive power. The third lens group G3 is composed of, in order from the object side, a third A lens group G3A with positive refractive power, an aperture stop AST, and a third B lens group G3B with positive refractive power. A cover glass CG is disposed between the fifth lens group G5 and the image surface (IM in FIG. 3 to FIG. 13).

The first lens group G1, the second lens group G2, and the third lens group G3A constitute an object-side lens group G _ob . The first lens group G1 constitutes an object-side first lens group G _ob1 , and the second lens group G2 constitutes an object-side second lens group G _ob2 .

The 3B lens group G3B, the 4th lens group G4, and the 5th lens group G5 constitute an image side lens group G _im . The 3B lens group G3B constitutes an image side first lens group G _im1 having a positive refractive power, the 4th lens group G4 constitutes an image side intermediate lens group G _im2 , and the 5th lens group G5 constitutes an image side final lens group G _L.

The second lens group G2, which is at least a part of the object-side second lens group G _ob2 , constitutes an object-side focusing lens group FL _ob that moves in the optical axis direction when focusing from infinity to a close distance. The fourth lens group G4, which is at least a part of the image-side intermediate lens group G _im2 , constitutes an image-side focusing lens group FL _im that moves in the optical axis direction when focusing from infinity to a close distance.

The first lens group G1 is composed of, in order from the object side, a negative meniscus lens 11C that is convex toward the object side, a negative meniscus lens 12C that is convex toward the object side, and a positive meniscus lens 13C that is convex toward the object side. The negative meniscus lens 12C has aspheric surfaces on both sides.

The second lens group G2 is composed of a negative meniscus lens 21C that is convex toward the image side.

The third lens group G3A is composed of a biconvex positive lens 31C. The biconvex positive lens 31C has aspheric surfaces on both sides.

The third lens group G3B is composed of, in order from the object side, a negative meniscus lens 32C convex toward the object side and a biconvex positive lens 33C. The negative meniscus lens 32C and the biconvex positive lens 33C are cemented together.

The fourth lens group G4 is composed of, in order from the object side, a biconcave negative lens 41C and a negative meniscus lens 42C that is convex toward the object side. The negative meniscus lens 42C has aspheric surfaces on both sides.

The fifth lens group G5 is composed of a positive meniscus lens 51C that is convex toward the image side.

(Table 29)
[Face data]
Magnification ratio: 4.04
Surface number RDN(d) ν(d)
1 26.083 1.400 1.78800 47.4
2 15.989 8.700
3* 575.918 1.900 1.58253 59.3
4* 15.374 3.500
5 24.898 4.300 1.84666 23.8
6 218.465 D6
7 -20.651 1.100 1.74100 52.6
8 -115.711 D8
9* 14.321 3.700 1.58253 59.3
10* -33.732 1.400
11 aperture INFINITY 1.800
12 40.399 1.000 1.91082 35.2
13 10.219 6.100 1.49700 81.6
14 -26.104 D14
15 -90.449 1.000 1.77250 49.6
16 34.071 1.500
17* 22.889 2.350 1.58313 59.4
18* 20.203 D18
19 -40.311 2.600 1.75520 27.5
20 -19.719 D20
21 INFINITY 1.000 1.51633 64.1
22 INFINITY -
* denotes a rotationally symmetric aspheric surface.
(Table 30)
[Aspheric data]
Surface number K A4 A6 A8 A10 A12
3 0.000 0.8459E-05 0.2652E-07 -0.4612E-09 0.2430E-11 -0.4082E-14
4 0.000 -0.3291E-04 -0.4004E-07 -0.1965E-08 0.1258E-10 -0.4166E-13
9 0.000 -0.3604E-04 -0.1395E-06 0.5028E-09 0.0000E+00 0.0000E+00
10 0.000 0.5026E-04 -0.1844E-06 0.1141E-08 0.0000E+00 0.0000E+00
17 0.000 0.1906E-03 -0.2103E-05 0.6937E-08 0.3572E-10 0.0000E+00
18 0.000 0.2548E-03 -0.1991E-05 -0.2460E-08 0.1031E-09 0.0000E+00
(Table 31)
[Various data]
Infinity Near distance
Wide-angle Mid-range Telephoto Wide-angle Mid-range Telephoto
FNO. 3.7 4.5 5.4 - - -
f 12.30 24.50 49.71 - - -
Magnification - - - -0.055 -0.109 -0.223
W 43.6 23.5 11.8 - - -
Y 10.81 10.81 10.81 10.81 10.81 10.81
BF 17.22 18.08 17.91 17.22 18.08 17.91
L 102.23 97.77 105.51 102.23 97.77 105.51
D0 - - - 203.000 203.000 201.000
D6 7.819 6.429 4.623 7.679 5.579 3.579
D8 26.010 10.502 1.560 26.149 11.353 2.604
D14 1.622 8.536 25.030 1.956 8.896 25.854
D18 6.872 11.533 13.700 6.538 11.173 12.876
D20 15.761 16.618 16.447 15.761 16.618 16.447
(Table 32)
[Lens group data]
Group starting plane focal length
1 1 -51.38
2 7 -34.09
3 9 18.37
4 15 -28.51
5 19 48.48

[Numerical Example 9]
94 to 103 and Tables 33 to 36 show the variable magnification optical system of Numerical Example 9. Figs. 94 and 95 are diagrams showing the lens configurations at the short focal length end and the long focal length end when focusing on infinity. Figs. 96 and 97 are diagrams showing longitudinal and lateral aberrations at the short focal length end when focusing on infinity. Figs. 98 and 99 are diagrams showing longitudinal and lateral aberrations at the long focal length end when focusing on infinity. Figs. 100 and 101 are diagrams showing longitudinal and lateral aberrations at the short focal length end when focusing on a close distance. Figs. 102 and 103 are diagrams showing longitudinal and lateral aberrations at the long focal length end when focusing on a close distance. Table 33 shows surface data, Table 34 shows aspherical surface data, Table 35 shows various data, and Table 36 shows lens group data.

The variable magnification optical system of Numerical Example 9 is composed of, from the object side, a first lens group G1 with positive refractive power, a second lens group G2 with negative refractive power, an aperture stop AST, a third lens group G3 with positive refractive power, a fourth lens group G4 with negative refractive power, a fifth lens group G5 with positive refractive power, and a sixth lens group G6 with negative refractive power. A cover glass CG is disposed between the sixth lens group G6 and the image surface (IM in Figures 3 to 13).

The first lens group G1 and the second lens group G2 constitute an object-side lens group G _ob 1 , and the second lens group G2 constitutes an object-side second lens group G _{ob 2} .

The third lens group G3, the fourth lens group G4, the fifth lens group G5, and the sixth lens group G6 constitute an image side lens group G _im . The third lens group G3 constitutes an image side first lens group G _im1 having a positive refractive power, the fourth lens group G4 constitutes an image side intermediate lens group G _im2 , and the fifth lens group G5 and the sixth lens group G6 constitute an image side final lens group G _L.

The second lens group G2, which is at least a part of the object-side second lens group G _ob2 , constitutes an object-side focusing lens group FL _ob that moves in the optical axis direction when focusing from infinity to a close distance. The fourth lens group G4, which is at least a part of the image-side intermediate lens group G _im2 , constitutes an image-side focusing lens group FL _im that moves in the optical axis direction when focusing from infinity to a close distance.

The first lens group G1 is composed of, in order from the object side, a negative meniscus lens 11D that is convex toward the object side, a biconvex positive lens 12D, and a positive meniscus lens 13D that is convex toward the object side. The negative meniscus lens 11D and the biconvex positive lens 12D are cemented together.

The second lens group G2 is composed of, in order from the object side, a negative meniscus lens 21D convex toward the object side, a biconcave negative lens 22D, a biconvex positive lens 23D, a biconcave negative lens 24D, and a positive meniscus lens 25D convex toward the object side. The negative meniscus lens 21D has an aspheric surface on the object side. The biconcave negative lens 24D and the positive meniscus lens 25D are cemented together.

The third lens group G3 is composed of, in order from the object side, a biconvex positive lens 31D, a biconvex positive lens 32D, a biconvex positive lens 33D, and a negative meniscus lens 34D that is convex toward the image side. The biconvex positive lens 31D has an aspheric surface on the object side. The biconvex positive lens 33D and the negative meniscus lens 34D are cemented together.

The fourth lens group G4 is composed of, in order from the object side, a biconcave negative lens 41D and a biconvex positive lens 42D. The biconcave negative lens 41D has an aspheric surface on the object side. The biconcave negative lens 41D and the biconvex positive lens 42D are cemented together.

The fifth lens group G5 is composed of, in order from the object side, a positive meniscus lens 51D convex toward the image side, a biconvex positive lens 52D, a biconcave negative lens 53D, and a biconvex positive lens 54D. The positive meniscus lens 51D has an aspheric surface on the object side. The biconcave negative lens 53D and the biconvex positive lens 54D are cemented together.

The sixth lens group G6 is composed of a negative meniscus lens 61D that is convex toward the object side.

(Table 33)
[Face data]
Magnification ratio: 16.62
Surface number RDN(d) ν(d)
1 132.137 2.100 1.91082 35.3
2 67.831 9.200 1.49700 81.5
3 -928.112 0.100
4 65.820 6.000 1.59522 67.7
5 447.652 D5
6* 912.183 1.200 1.85135 40.1
7 22.039 7.171
8 -41.784 1.000 1.80400 46.6
9 98.152 0.150
10 47.939 7.300 1.78472 25.7
11 -34.914 0.704
12 -27.874 1.000 1.80400 46.6
13 55.543 2.442 1.80809 22.8
14 665.255 D14
15 aperture INFINITY 1.000
16* 89.782 4.000 1.55332 71.7
17 -80.897 0.100
18 103.295 4.500 1.48749 70.2
19 -44.844 0.100
20 96.213 5.000 1.48749 70.2
21 -32.595 1.000 1.80518 25.4
22 -122.573 D22
23* -30.830 0.900 1.69350 53.2
24 40.039 3.500 1.72151 29.2
25 -236.626 D25
26* -130.595 4.400 1.58313 59.4
27 -32.766 0.100
28 37.087 5.800 1.48749 70.2
29 -39.497 1.500
30 -41.322 1.000 1.88300 40.8
31 41.827 5.300 1.51742 52.4
32 -41.679 D32
33 122.550 1.100 1.48749 70.2
34 34.903 D34
35 INFINITY 2.000 1.51633 64.1
36 INFINITY -
* denotes a rotationally symmetric aspheric surface.
(Table 34)
[Aspheric data]
Surface number K A4 A6 A8 A10
3 0.000 0.2811E-05 -0.3369E-08 -0.2096E-11 0.2471E-13
16 0.000 -0.1375E-05 0.2414E-08 -0.2084E-10 0.8459E-13
23 0.000 0.7528E-05 0.2042E-08 -0.1698E-11 0.0000E+00
26 0.000 -0.9765E-05 0.4055E-09 -0.9703E-11 -0.3800E-14
(Table 35)
[Various data]
Infinity Near distance
Wide-angle Mid-range Telephoto Wide-angle Mid-range Telephoto
FNO. 3.3 4.8 5.8 - - -
f 18.20 75.15 302.51 - - -
Magnification - - - -0.061 -0.177 -0.285
W 40.0 9.8 2.5 - - -
Y 13.50 13.50 13.50 13.50 13.50 13.50
BF 35.32 52.52 52.20 35.32 52.52 52.20
L 196.46 229.09 250.77 196.46 229.09 250.77
D0 - - - 258.000 223.000 198.000
D5 2.100 42.154 70.138 1.000 37.433 54.849
D14 47.556 19.626 1.000 48.656 24.346 16.289
D22 3.500 21.966 32.682 3.697 20.584 28.125
D25 25.427 12.203 2.300 25.230 13.586 6.857
D32 4.210 2.280 14.103 4.210 2.280 14.103
D34 33.000 50.197 49.885 33.000 50.197 49.885
(Table 36)
[Lens group data]
Group starting plane focal length
1 1 110.71
2 6 -15.82
3 16 33.73
4 23 -53.86
5 26 44.61
6 33 -100.52

[Numerical Example 10]
104 to 113 and Tables 37 to 40 show the variable magnification optical system of Numerical Example 10. Figs. 104 and 105 are diagrams showing the lens configurations at the short focal length end and the long focal length end when focusing on infinity. Figs. 106 and 107 are diagrams showing longitudinal aberration and lateral aberration when focusing on infinity at the short focal length end. Figs. 108 and 109 are diagrams showing longitudinal aberration and lateral aberration when focusing on infinity at the long focal length end. Figs. 110 and 111 are diagrams showing longitudinal aberration and lateral aberration when focusing on a close distance at the short focal length end. Figs. 112 and 113 are diagrams showing longitudinal aberration and lateral aberration when focusing on a close distance at the long focal length end. Table 37 shows surface data, Table 38 shows aspherical surface data, Table 39 shows various data, and Table 40 shows lens group data.

The variable magnification optical system of Numerical Example 10 is composed of, in order from the object side, a first lens group G1 with positive refractive power, a second lens group G2 with negative refractive power, a third lens group G3 with negative refractive power, an aperture stop AST, a fourth lens group G4 with positive refractive power, a fifth lens group G5 with positive refractive power, a sixth lens group G6 with negative refractive power, and a seventh lens group G7 with negative refractive power. A cover glass CG is disposed between the seventh lens group G7 and the image surface (IM in Figures 3 to 13).

The first lens group G1, the second lens group G2, and the third lens group G3 constitute an object-side lens group G _ob . The first lens group G1 constitutes an object-side first lens group G _ob1 , and the second lens group G2 and the third lens group G3 constitute an object-side second lens group G _ob2 .

The fourth lens group G4, the fifth lens group G5, the sixth lens group G6, and the seventh lens group G7 constitute an image side lens group G _im . The fourth lens group G4 constitutes an image side first lens group G _im1 having a positive refractive power, the fifth lens group G5 constitutes an image side intermediate lens group G _im2 , and the sixth lens group G6 and the seventh lens group G7 constitute an image side final lens group G _L.

The third lens group G3, which is at least a part of the object-side second lens group G _ob2 , constitutes an object-side focusing lens group FL _ob that moves in the optical axis direction when focusing from infinity to a close distance. The fifth lens group G5, which is at least a part of the image-side intermediate lens group G _im2 , constitutes an image-side focusing lens group FL _im that moves in the optical axis direction when focusing from infinity to a close distance.

The first lens group G1 is composed of, in order from the object side, a negative meniscus lens 11E convex toward the object side, a biconvex positive lens 12E, and a biconvex positive lens 13E. The negative meniscus lens 11E and the biconvex positive lens 12E are cemented together.

The second lens group G2 is composed of, in order from the object side, a biconvex positive lens 21E, a biconcave negative lens 22E, a biconcave negative lens 23E, and a positive meniscus lens 24E that is convex toward the object side. The biconvex positive lens 21E and the biconcave negative lens 22E are cemented together. The biconcave negative lens 23E and the positive meniscus lens 24E are cemented together.

The third lens group G3 is composed of a biconcave negative lens 31E.

The fourth lens group G4 is composed of, in order from the object side, a biconvex positive lens 41E, a biconcave negative lens 42E, a biconvex positive lens 43E, a positive meniscus lens 44E convex toward the image side, and a negative meniscus lens 45E convex toward the image side. The biconcave negative lens 42E and the biconvex positive lens 43E are cemented together. The positive meniscus lens 44E and the negative meniscus lens 45E are cemented together.

The fifth lens group G5 is composed of, in order from the object side, a biconvex positive lens 51E, a biconcave negative lens 52E, and a biconvex positive lens 53E. The biconvex positive lens 51E and the biconcave negative lens 52E are cemented together. The biconvex positive lens 53E has aspheric surfaces on both sides.

The sixth lens group G6 is composed of, in order from the object side, a negative meniscus lens 61E convex toward the object side, a positive meniscus lens 62E convex toward the object side, and a biconvex positive lens 63E. The negative meniscus lens 61E has an aspheric surface on the object side. The negative meniscus lens 61E and the positive meniscus lens 62E are cemented together.

The seventh lens group G7 is composed of, in order from the object side, a negative meniscus lens 71E that is convex toward the object side, and a positive meniscus lens 72E that is convex toward the object side. The negative meniscus lens 71E and the positive meniscus lens 72E are cemented together.

(Table 37)
[Face data]
Magnification ratio: 4.71
Surface number RDN(d) ν(d)
1 166.234 1.500 1.90265 35.7
2 86.857 6.500 1.49782 82.6
3 -400.618 0.100
4 81.505 5.700 1.43700 95.1
5 -5366.791 D5
6 85.160 6.000 1.90265 35.7
7 -85.143 1.500 1.48749 70.3
8 84.445 2.700
9 -144.821 1.000 1.69680 55.5
10 30.606 2.000 1.84666 23.8
11 41.680 D11
12 -53.008 1.000 1.80610 41.0
13 149.426 D13
14 aperture INFINITY 1.500
15 55.142 5.500 1.49782 82.6
16 -23.931 0.800
17 -21.882 1.300 1.64769 33.7
18 35.629 6.000 1.90366 31.3
19 -32.217 0.100
20 -36.421 1.900 1.49782 82.6
21 -31.683 1.000 1.90366 31.3
22 -127.712 D22
23 22.917 5.000 1.49782 82.6
24 -168.476 1.000 1.90265 35.7
25 43.499 4.000
26* 76.865 5.500 1.75501 51.2
27* -45.498 D27
28* 623.398 1.000 1.72903 54.0
29 16.719 2.000 1.80809 22.7
30 22.053 1.500
31 85.188 1.300 1.59319 67.9
32 -54.499 D32
33 372.233 2.500 1.75500 52.3
34 75.681 1.000 2.00100 29.1
35 81.351 D35
36 INFINITY 2.500 1.51680 63.9
37 INFINITY -
* denotes a rotationally symmetric aspheric surface.
(Table 38)
[Aspheric data]
Surface number K A4 A6 A8
26 0.000 -0.2309E-04 -0.5216E-07 -0.1981E-09
27 0.000 -0.9774E-05 -0.4774E-07 -0.1053E-09
28 0.000 -0.1190E-05 0.5726E-08 0.6576E-11
(Table 39)
[Various data]
Infinity Near distance
Wide-angle Mid-range Telephoto Wide-angle Mid-range Telephoto
FNO. 2.9 2.9 2.9 - - -
f 30.90 74.60 145.50 - - -
Magnification - - - -0.053 -0.110 -0.208
W 14.5 6.0 3.0 - - -
Y 8.00 8.00 8.00 8.00 8.00 8.00
BF 20.66 26.40 18.11 20.66 26.40 18.11
L 184.77 186.25 183.78 184.77 186.25 183.78
D0 - - - 514.000 514.000 514.000
D5 2.000 36.337 61.673 2.000 36.337 61.673
D11 5.846 6.960 4.697 7.195 7.322 5.000
D13 63.664 26.782 1.500 62.315 26.420 1.197
D22 11.265 10.334 16.389 10.402 7.010 3.104
D27 2.000 5.419 3.413 2.863 8.743 16.698
D32 7.581 2.266 6.253 7.581 2.266 6.253
D35 18.315 24.049 15.759 18.315 24.049 15.759
(Table 40)
[Lens group data]
Group starting plane focal length
1 1 134.77
2 6 -116.07
3 12 -48.43
4 15 62.11
5 23 41.41
6 28 -85.16
7 33 -143.53

[Numerical Example 11]
114 to 123 and Tables 41 to 44 show the variable magnification optical system of Numerical Example 11. Figs. 114 and 115 are diagrams showing the lens configurations at the short focal length end and the long focal length end when focusing on infinity. Figs. 116 and 117 are diagrams showing longitudinal aberration and lateral aberration when focusing on infinity at the short focal length end. Figs. 118 and 119 are diagrams showing longitudinal aberration and lateral aberration when focusing on infinity at the long focal length end. Figs. 120 and 121 are diagrams showing longitudinal aberration and lateral aberration when focusing on a close distance at the short focal length end. Figs. 122 and 123 are diagrams showing longitudinal aberration and lateral aberration when focusing on a close distance at the long focal length end. Table 41 shows surface data, Table 42 shows aspherical surface data, Table 43 shows various data, and Table 44 shows lens group data.

The variable magnification optical system of Numerical Example 11 is composed of, in order from the object side, a first lens group G1 with negative refractive power, a second lens group G2 with positive refractive power, a third lens group G3 with negative refractive power, an aperture stop AST, a fourth lens group G4 with negative refractive power, a fifth lens group G5 with positive refractive power, a sixth lens group G6 with negative refractive power, and a seventh lens group G7 with positive refractive power.

The first lens group G1, the second lens group G2, and the third lens group G3 constitute an object-side lens group G _ob . The first lens group G1 constitutes an object-side first lens group G _ob1 , and the second lens group G2 and the third lens group G3 constitute an object-side second lens group G _ob2 .

The fourth lens group G4, the fifth lens group G5, the sixth lens group G6, and the seventh lens group G7 constitute an image side lens group G _im . The fourth lens group G4 and the fifth lens group G5 constitute an image side first lens group G _im1 having a positive refractive power, the sixth lens group G6 constitutes an image side intermediate lens group G _im2 , and the seventh lens group G7 constitutes an image side final lens group G _L.

The third lens group G3, which is at least a part of the object-side second lens group G _ob2 , constitutes an object-side focusing lens group FL _ob that moves in the optical axis direction when focusing from infinity to a close distance. The sixth lens group G6, which is at least a part of the image-side intermediate lens group G _im2 , constitutes an image-side focusing lens group FL _im that moves in the optical axis direction when focusing from infinity to a close distance.

The first lens group G1 is composed of, in order from the object side, a negative meniscus lens 11F convex toward the object side, a biconcave negative lens 12F, and a biconvex positive lens 13F. The biconcave negative lens 12F has aspheric surfaces on both sides.

The second lens group G2 is composed of, in order from the object side, a positive meniscus lens 21F convex toward the object side, a negative meniscus lens 22F convex toward the object side, and a biconvex positive lens 23F. The negative meniscus lens 22F and the biconvex positive lens 23F are cemented together.

The third lens group G3 is composed of a biconcave negative lens 31F.

The fourth lens group G4 is composed of a negative meniscus lens 41F that is convex toward the image side. The negative meniscus lens 41F has an aspheric surface on the object side.

The fifth lens group G5 is composed of, in order from the object side, a negative meniscus lens 51F convex toward the object side, a biconvex positive lens 52F, and a positive meniscus lens 53F convex toward the object side. The positive meniscus lens 53F has an aspheric surface on the object side. The negative meniscus lens 51F and the biconvex positive lens 52F are cemented together.

The sixth lens group G6 is composed of a biconcave negative lens 61F. The biconcave negative lens 61F has aspheric surfaces on both sides.

The seventh lens group G7 is composed of a positive meniscus lens 71F that is convex toward the object side.

(Table 41)
[Face data]
Magnification ratio: 2.64
Surface number RDN(d) ν(d)
1 240.482 1.250 1.71300 53.9
2 16.511 8.206
3* -180.377 1.000 1.51760 63.5
4* 46.529 0.397
5 72.105 2.900 1.84666 23.8
6 -198.577 D6
7 25.193 1.850 1.80420 46.5
8 90.430 0.200
9 23.660 1.000 1.68893 31.2
10 12.556 5.200 1.59282 68.6
11 -62.442 D11
12 -52.247 1.000 1.71736 29.5
13 775.713 D13
14 aperture INFINITY 2.000
15* -22.616 1.000 1.51760 63.5
16 -3904.543 D16
17 15.263 1.000 1.80518 25.5
18 12.311 3.697 1.59282 68.6
19 -27.689 0.100
20* 35.428 1.000 1.51760 63.5
21 47.279 D21
22* -39.442 1.000 1.80998 40.9
23* 21.795 D23
24 32.163 2.000 1.84666 23.8
25 102.228 -
* denotes a rotationally symmetric aspheric surface.
(Table 42)
[Aspheric data]
Surface number K A4 A6 A8 A10
3 0.000 -0.1180E-03 0.1150E-05 -0.5919E-08 0.1061E-10
4 0.000 -0.1230E-03 0.1174E-05 -0.6326E-08 0.1203E-10
15 0.000 0.7257E-05 -0.1464E-06 0.0000E+00 0.0000E+00
20 0.000 -0.1380E-03 -0.9064E-07 -0.9667E-08 0.8359E-10
22 0.000 -0.8885E-04 0.3144E-06 0.0000E+00 0.0000E+00
23 0.000 -0.8260E-04 0.4346E-06 -0.1418E-08 0.9465E-11
(Table 43)
[Various data]
Infinity Near distance
Wide-angle Mid-range Telephoto Wide-angle Mid-range Telephoto
FNO. 2.9 2.9 2.9 - - -
f 12.48 20.00 33.00 - - -
Magnification - - - -0.072 -0.117 -0.198
W 49.7 29.8 18.2 - - -
Y 10.81 10.81 10.81 10.81 10.81 10.81
BF 7.55 10.36 12.32 7.55 10.36 12.32
L 84.64 72.67 71.56 84.64 72.67 71.56
D0 - - - 150.000 150.000 150.000
D6 29.269 11.600 1.000 29.269 11.600 1.000
D11 1.459 2.122 4.141 0.500 0.646 1.974
D13 2.242 2.379 1.000 3.201 3.855 3.167
D16 4.192 3.613 2.359 4.192 3.613 2.359
D21 2.493 2.674 2.703 3.629 4.377 5.171
D23 2.638 5.128 13.233 1.502 3.425 10.766
(Table 44)
[Lens group data]
Group starting plane focal length
1 1 -27.28
2 7 19.35
3 12 -68.20
4 15 -43.95
5 17 17.03
6 22 -17.21
7 24 54.71

Values for each conditional expression in Numerical Examples 1 to 6 and 9 to 11 are shown in Table 45.
(Table 45)
Example 1 Example 2 Example 3 Example 4
Conditional formula (1) (1') 1.580 4.835 1.110 1.163
Condition (2) (2') 0.071 0.250 0.246 0.067
Condition (3) (3') 3.454 2.583 1.097 3.016
Condition (4) (4') 0.131 0.132 0.142 0.130
Condition (5) (5') 1.889 4.892 1.901 1.546
Condition (6) (6') 1.307 1.378 1.375 1.347
Condition (7) (7') 0.088 0.059 0.127 0.111
Conditional expression (1A) (1B) 0.633 0.207 0.901 0.860
Conditional expression (2A) (2B) 14.006 4.000 4.072 14.983
Conditional expression (3A) (3B) 0.131 0.132 0.142 0.130
Conditional expression (4A) (4B) 3.454 2.583 1.097 3.016
Conditional expression (5A) (5B) 0.529 0.204 0.526 0.647
Conditional expression (6A) (6B) 0.765 0.726 0.727 0.743
Conditional expression (7A) (7B) 11.379 16.920 7.885 8.998
Example 5 Example 6 Comparative Example 7 Comparative Example 8
Condition (1) (1') 1.617 4.650 - -
Condition (2) (2') 0.040 0.276 - -
Condition (3) (3') 5.947 2.176 - -
Condition (4) (4') 0.126 0.127 - -
Condition (5) (5') 1.902 4.738 - -
Condition (6) (6') 1.346 1.320 - -
Condition (7) (7') 0.097 0.054 - -
Conditional expression (1A) (1B) 0.618 0.215 - -
Conditional expression (2A) (2B) 24.878 3.617 - -
Conditional expression (3A) (3B) 0.126 0.127 - -
Conditional expression (4A) (4B) 5.947 2.176 - -
Conditional expression (5A) (5B) 0.526 0.211 - -
Conditional expression (6A) (6B) 0.743 0.757 - -
Conditional expression (7A) (7B) 10.311 18.405 - -
Example 9 Example 10 Example 11
Condition (1) (1') 0.294 1.170 3.964
Condition (2) (2') 3.086 12.211 3.095
Condition (3) (3') 1.490 1.099 0.380
Condition (4) (4') 2.288 1.412 0.592
Condition (5) (5') 2.010 9.498 1.986
Condition (6) (6') 2.477 2.168 0.145
Condition (7) (7') 0.021 0.043 0.072
Conditional expression (1A) (1B) 0.294 0.855 0.252
Conditional expression (2A) (2B) 3.086 0.082 0.323
Conditional expression (3A) (3B) 1.490 1.412 0.592
Conditional expression (4A) (4B) 2.288 1.099 0.380
Conditional expression (5A) (5B) 2.010 0.105 0.504
Conditional expression (6A) (6B) 2.477 0.461 6.905
Conditional expression (7A) (7B) 0.021 22.993 13.859

As is clear from Table 45, Numerical Examples 1 to 6 and 9 to 11 satisfy at least one of conditional expressions (1), (1'), (1A), and (1B), conditional expressions (2), (2'), (2A), and (2B), conditional expressions (3), (3'), (3A), and (3B), conditional expressions (4), (4'), (4A), and (4B), conditional expressions (5), (5'), (5A), and (5B), conditional expressions (6), (6'), (6A), and (6B), and conditional expressions (7), (7'), (7A), and (7B). In addition, as is clear from the longitudinal aberration diagrams and the lateral aberration diagrams, various aberrations are relatively well corrected.

Even if a lens or lens group with no substantial power is added to a variable power optical system included in the scope of the claims of the present invention, it is still included in the technical scope of the present invention (it does not circumvent the technical scope of the present invention). Furthermore, terms such as "consisting of (being composed of)" and "consisting of (being composed of)" (closed-form terms) are intended to mean that, in addition to the components listed, optical elements such as lenses, filters, and cover glasses with no substantial refractive power, fixed apertures such as flare cutters, mirror frame members that hold lenses, image stabilization mechanisms, and image sensors may also be included.

The variable magnification optical system of this embodiment is not limited to the five-group, six-group, or seven-group configuration shown in the numerical examples above. In addition, an aspheric or diffractive surface may be used on any of the surfaces, and the aspheric surface may be a glass-molded aspheric surface or a ground aspheric surface formed directly on the lens surface, a composite aspheric lens (hybrid lens) in which a resin layer is applied to the lens surface and an aspheric surface is then applied on top of that, or a plastic aspheric surface in which the lens itself is made of a resin material.

The variable magnification optical system of this embodiment has the following configuration. It should be noted that this configuration can be a limitation for differentiating the present invention from the prior art including the above-mentioned Patent Document 1.
When focusing from infinity to a close distance, the air gap between the object-side focusing lens unit and the aperture stop may change.
When focusing from infinity to a close distance, the air gap between the image-side focusing lens unit and the aperture stop may change.
When focusing from infinity to a close distance, the first lens unit on the object side does not need to move.
When focusing from infinity to a close distance, the first image-side lens unit does not need to move.
When focusing from infinity to a close distance, the final lens unit on the image side does not need to move.
When focusing from infinity to close distances, the aperture diaphragm does not need to move.
The object-side focusing lens unit may have negative refractive power.
The image-side focusing lens group may be composed of two or less lens elements.
The first object-side lens group may be made up of two or more lens elements.
The first object-side lens group may be made up of three or more lens elements.
The first lens unit on the object side may have positive refractive power.
When varying magnification from the short focal length extremity to the long focal length extremity, the first object-side lens unit may move relative to the image plane.

In this specification, the following definitions or variations of terms may be considered.
The lens group may refer to a portion of an optical system having at least one lens element separated by an air gap that changes when varying magnification or focusing.
The lens component may refer to a single lens or a cemented lens in which multiple lenses are cemented together.
A lens group or a part of the lens group may be moved in a direction perpendicular to the optical axis to function as an image stabilization group that corrects image blur caused by camera shake.
It is preferable that the aperture stop be disposed between the object-side focusing lens group and the image-side focusing lens group as an independent member, but the aperture stop may be fulfilled by a frame that houses the lenses.
The values of the radius of curvature, surface spacing, refractive index, Abbe number, number of variable spacings during magnification change, etc. of each lens are not limited to the values shown in each embodiment and may take other values.
A lens group that does not move relative to the image plane during zooming or focusing may be added to the object side of the first lens group on the object side or to the image plane side of the final lens group on the image side. Specifically, a front converter and a rear converter may be added.

With reference to Figures 124 and 125, we will explain a digital camera (imaging device) 100 equipped with the variable magnification optical system of this embodiment.

The digital camera 100 has a camera body (housing) 101, a photographing lens (interchangeable lens) 102, a viewfinder 103, a flash 104, a shutter button 105, a power button 106, an LCD monitor 107, operation buttons 108, a memory card slot 109, and a magnification switch 110.

The camera body 101 houses the various components of the digital camera 100. The photographing lens 102 is, for example, a unit formed by incorporating the variable magnification optical system of this embodiment into a lens barrel. The viewfinder 103 is a viewing window for determining the subject and composition. The flash 104 emits a flash when photographing at night or in a dark place. The shutter button 105 is a physical switch for executing photographing with the digital camera 100. The power button 106 is a physical switch for switching the power of the digital camera 100 on and off. The liquid crystal monitor 107 displays images photographed by the digital camera 100, etc. The operation button 108 is a physical switch for setting the photographing mode of the digital camera 100, etc. The memory card slot 109 is a slot for inserting a memory card (not shown) that stores images photographed by the digital camera 100, etc. The magnification change switch 110 is a physical switch for performing magnification change (zooming) between the short focal length end and the long focal length end. By operating the magnification change switch 110, the spacing between the lens groups in the variable magnification optical system of this embodiment can be changed as appropriate.

The digital camera 100 has a central processing unit 111, an image processing unit 112, a light receiving element 113, a signal processing unit 114, a semiconductor memory 115, and a communication card 116 as internal functional components of the camera body 101.

The central processing unit 111 performs various types of arithmetic processing within the digital camera 100. The image processing unit 112 performs various types of image processing on images captured by the digital camera 100. The light receiving element 113 takes in and receives external light used for photometry processing. The signal processing unit 114 performs various types of signal processing such as shooting instruction signals and image processing signals. The semiconductor memory 115 forms a temporary storage area for images captured by the digital camera 100. The communication card 116 enables wireless communication with an external device (not shown).

The configuration of the digital camera 100 described here is merely one example, and various design changes are possible (there is a degree of freedom in the specific form of the digital camera 100).

The variable magnification optical system of this embodiment can also be applied to devices other than the digital camera 100 described above, such as interchangeable lenses, portable information terminal devices, video cameras, silver halide cameras, optical sensors, and projection optical systems (projectors).

Figure 126 is a diagram showing an example of the external configuration of a lens barrel (interchangeable lens) LX equipped with a variable magnification optical system according to this embodiment. The lens barrel LX is configured, for example, as a variable magnification interchangeable lens for a single-lens reflex camera. The lens barrel LX has a fixed barrel 10, and a lens mount 100LM is fixed to the rear side surface of the fixed barrel 10. A variable magnification ring 11 is fitted to the front region in the optical axis direction of the circumferential surface of the fixed barrel 10, and a focus ring 12 is fitted to the rear region. Rubber rings ZG, FG are fixed to the circumferential surfaces of the variable magnification ring 11 and focus ring 12, improving the feel during operation.

The lens barrel LX can be attached to and detached from a camera body (not shown) by a lens mount 100LM provided on a fixed barrel 10, and zooming can be performed to the long focal length (telephoto) side or the short focal length (wide) side by rotating the magnification change ring 11. In addition, by pressing a retraction button B arranged on the periphery and operating the magnification change ring 11 further to the short focal length side, the lens barrel LX can be set to a retracted state in which the length is at its minimum. Focusing is performed automatically by a built-in motor, but manual focusing is also possible by rotating the focus ring 12.

Inside the fixed barrel 10, there are an outer linear cylinder 13 and an inner linear cylinder (not shown) that are arranged coaxially with a required gap in the barrel diameter direction. These linear cylinders are integrated with each other at their rear ends, and are moved linearly in the optical axis direction together inside the fixed barrel 10 as the magnification ring 11 rotates due to cam engagement between a linear groove in the optical axis direction provided on the fixed barrel 10 and a cam groove provided on the magnification ring 11.

Although not shown, a helicoid tube with a helicoid groove formed on the outer periphery is fitted to the outer periphery of the inner linear tube. This helicoid tube moves in the axial direction together with the inner linear tube, but is linked to the variable magnification ring 11, and is rotated around the axis on the circumferential surface of the inner linear tube with the rotation of the variable magnification ring 11. In addition, a front linear tube 16 is fitted between the helicoid tube and the outer linear tube 13 in the radial direction. This front linear tube 16 is fitted into the helicoid groove of the helicoid tube, and is moved in the optical axis direction by the rotation of the helicoid tube. A lens L1 is supported on the front end of this front linear tube 16. The lens L1 depicted in FIG. 126 can be, for example, the lens located closest to the object side of the variable magnification optical system of this embodiment. In addition, the lens barrel LX is provided with a component (for example, an ON/OFF switch for the vibration-proof drive) for exerting and supporting the function of the variable magnification optical system of this embodiment.

G _ob object side lens group G _ob1 object side first lens group G _ob2 object side second lens group FL _ob object side focusing lens group (first focusing lens group, second focusing lens group)
G _im image side lens group G _im1 image side first lens group G _im2 image side intermediate lens group G _L image side final lens group FL _im image side focusing lens group (first focusing lens group, second focusing lens group)
AST Aperture LX Lens Barrel (Interchangeable Lens)
100 Digital camera (imaging device)
102 Shooting lens (interchangeable lens)

Claims (17)

The optical system is composed of, in order from the object side, an object-side lens group, an aperture stop, and an image-side lens group,
the object-side lens group includes, in order from the object side, a first object-side lens group and a second object-side lens group;
the image-side lens group is composed of, in order from the object side, an image-side first lens group having a positive refractive power, an image-side intermediate lens group, and an image-side final lens group;
When changing magnification from the short focal length end to the long focal length end, the spacing between adjacent lens groups changes.
At least a part of the object-side second lens group includes an object-side focusing lens group that moves in the optical axis direction during focusing from infinity to a close distance,
At least a part of the image-side intermediate lens group has an image-side focusing lens group that moves in the optical axis direction during focusing from infinity to a close distance,
The object-side focusing lens group and the image-side focusing lens group move along different paths in the optical axis direction when focusing from infinity to a close distance,
When the object-side focusing lens group is the first focusing lens group and the image-side focusing lens group is the second focusing lens group, the following conditional expressions (1) and (2) are satisfied:
A variable magnification optical system characterized by:
(1) 1.170≦｜f1/f2｜<10
(2) 3.0<|p2T/p1T|<20
however,
f1: focal length of the first focusing lens group,
f2: focal length of the second focusing lens group,
p1T: focus sensitivity of the first focusing lens group when focusing on infinity at the long focal length end,
p2T: focus sensitivity of the second focusing lens group when focusing on infinity at the long focal length end,
p1T=(1-m1T^2)×m1RT^2
p2T=(1-m2T^2)×m2RT^2
m1T: paraxial lateral magnification of the first focusing lens group when focusing on infinity at the long focal length end,
m1RT: paraxial lateral magnification of the optical system on the image side of the first focusing lens group when focusing on infinity at the long focal length end,
m2T: paraxial lateral magnification of the second focusing lens group when focusing on infinity at the long focal length end,
m2RT: the paraxial lateral magnification of the optical system on the image side of the second focusing lens group when focusing on infinity at the long focal length end. The following condition (3) is satisfied:
2. The variable magnification optical system according to claim 1 .
(3) 0.10<|p2W/p2T|<10
however,
p2W: focus sensitivity of the second focusing lens group when focusing on infinity at the short focal length end,
p2T: focus sensitivity of the second focusing lens group when focusing on infinity at the long focal length end,
p2W=(1-m2W^2)×m2RW^2
p2T=(1-m2T^2)×m2RT^2
m2W: paraxial lateral magnification of the second focusing lens group when focusing on infinity at the short focal length end,
m2RW: paraxial lateral magnification of the optical system on the image side of the second focusing lens group when focusing on infinity at the short focal length end,
m2T: paraxial lateral magnification of the second focusing lens group when focusing on infinity at the long focal length end,
m2RT: the paraxial lateral magnification of the optical system on the image side of the second focusing lens group when focusing on infinity at the long focal length end. The following condition (4) is satisfied:
3. A variable magnification optical system according to claim 1 or 2 .
(4) 0.05<|p1W/p1T|<5.0
however,
p1W: focus sensitivity of the first focusing lens group when focusing on infinity at the short focal length end,
p1T: focus sensitivity of the first focusing lens group when focusing on infinity at the long focal length end,
p1W=(1-m1W^2)×m1RW^2
p1T=(1-m1T^2)×m1RT^2
m1W: paraxial lateral magnification of the first focusing lens group when focusing on infinity at the short focal length extremity,
m1RW: paraxial lateral magnification of the optical system on the image side of the first focusing lens group when focusing on infinity at the short focal length end,
m1T: paraxial lateral magnification of the first focusing lens group when focusing on infinity at the long focal length end,
m1RT: the paraxial lateral magnification of the optical system on the image side of the first focusing lens group when focusing on infinity at the long focal length end. The following condition (5) is satisfied:
4. The variable magnification optical system according to claim 1 , wherein the first lens is a lens having a first focal length of 100 mm or less.
(5) 1.5<|p2W/p1W|<15
however,
p1W: focus sensitivity of the first focusing lens group when focusing on infinity at the short focal length end,
p2W: focus sensitivity of the second focusing lens group when focusing on infinity at the short focal length end,
p1W=(1-m1W^2)×m1RW^2
p2W=(1-m2W^2)×m2RW^2
m1W: paraxial lateral magnification of the first focusing lens group when focusing on infinity at the short focal length extremity,
m1RW: paraxial lateral magnification of the optical system on the image side of the first focusing lens group when focusing on infinity at the short focal length end,
m2W: paraxial lateral magnification of the second focusing lens group when focusing on infinity at the short focal length end,
m2RW: the paraxial lateral magnification of the optical system on the image side of the second focusing lens group when focused on infinity at the short focal length extremity. The following conditional expressions (6) and (7) are satisfied:
5. A variable magnification optical system according to claim 1 , wherein the first lens is a lens having a first focal length of 100 mm or less.
(6) 1.3<d1W/d2W<2.0
(7) 0.015<d1T/d2T<0.15
however,
d1W: the length from the aperture stop to the optical surface of the first focusing lens group closest to the aperture stop at the short focal length end,
d2W: the length from the aperture stop to the optical surface of the second focusing lens group closest to the aperture stop at the short focal length end,
d1T: the length from the aperture stop to the optical surface of the first focusing lens group closest to the aperture stop at the long focal length end,
d2T: the length from the aperture stop to the optical surface of the second focusing lens group that is closest to the aperture stop at the long focal length extremity. The optical system is composed of, in order from the object side, an object-side lens group, an aperture stop, and an image-side lens group,
the object-side lens group includes, in order from the object side, a first object-side lens group and a second object-side lens group;
the image-side lens group is composed of, in order from the object side, an image-side first lens group having a positive refractive power, an image-side intermediate lens group, and an image-side final lens group;
When changing magnification from the short focal length end to the long focal length end, the spacing between adjacent lens groups changes.
At least a part of the object-side second lens group includes an object-side focusing lens group that moves in the optical axis direction during focusing from infinity to a close distance,
At least a part of the image-side intermediate lens group has an image-side focusing lens group that moves in the optical axis direction during focusing from infinity to a close distance,
The object-side focusing lens group and the image-side focusing lens group move along different paths in the optical axis direction when focusing from infinity to a close distance,
When the object-side focusing lens group is the first focusing lens group and the image-side focusing lens group is the second focusing lens group, the following conditional expressions (1') and (2') are satisfied:
A variable magnification optical system characterized by:
(1') 1.0<|f1/f2|<10
(2') 0.03<|p2T/p1T|≦0.250
however,
f1: focal length of the first focusing lens group,
f2: focal length of the second focusing lens group,
p1T: focus sensitivity of the first focusing lens group when focusing on infinity at the long focal length end,
p2T: focus sensitivity of the second focusing lens group when focusing on infinity at the long focal length end,
p1T=(1-m1T^2)×m1RT^2
p2T=(1-m2T^2)×m2RT^2
m1T: paraxial lateral magnification of the first focusing lens group when focusing on infinity at the long focal length end,
m1RT: paraxial lateral magnification of the optical system on the image side of the first focusing lens group when focusing on infinity at the long focal length end,
m2T: paraxial lateral magnification of the second focusing lens group when focusing on infinity at the long focal length end,
m2RT: the paraxial lateral magnification of the optical system on the image side of the second focusing lens group when focusing on infinity at the long focal length end. The following condition (3') is satisfied:
7. The variable magnification optical system according to claim 6 .
(3') 1.0<|p2W/p2T|<10
however,
p2W: focus sensitivity of the second focusing lens group when focusing on infinity at the short focal length end,
p2T: focus sensitivity of the second focusing lens group when focusing on infinity at the long focal length end,
p2W=(1-m2W^2)×m2RW^2
p2T=(1-m2T^2)×m2RT^2
m2W: paraxial lateral magnification of the second focusing lens group when focusing on infinity at the short focal length end,
m2RW: paraxial lateral magnification of the optical system on the image side of the second focusing lens group when focusing on infinity at the short focal length end,
m2T: paraxial lateral magnification of the second focusing lens group when focusing on infinity at the long focal length end,
m2RT: the paraxial lateral magnification of the optical system on the image side of the second focusing lens group when focusing on infinity at the long focal length end. The following condition (4') is satisfied:
8. The variable magnification optical system according to claim 6 or 7 .
(4') 0.0015<|p1W/p1T|<0.15
however,
p1W: focus sensitivity of the first focusing lens group when focusing on infinity at the short focal length end,
p1T: focus sensitivity of the first focusing lens group when focusing on infinity at the long focal length end,
p1W=(1-m1W^2)×m1RW^2
p1T=(1-m1T^2)×m1RT^2
m1W: paraxial lateral magnification of the first focusing lens group when focusing on infinity at the short focal length extremity,
m1RW: paraxial lateral magnification of the optical system on the image side of the first focusing lens group when focusing on infinity at the short focal length end,
m1T: paraxial lateral magnification of the first focusing lens group when focusing on infinity at the long focal length end,
m1RT: the paraxial lateral magnification of the optical system on the image side of the first focusing lens group when focusing on infinity at the long focal length end. The following condition (5') is satisfied:
9. The variable magnification optical system according to claim 6 , wherein the first lens is a lens having a first focal length of 100 nm or less.
(5')1.5<|p2W/p1W|<15
however,
p1W: focus sensitivity of the first focusing lens group when focusing on infinity at the short focal length end,
p2W: focus sensitivity of the second focusing lens group when focusing on infinity at the short focal length end,
p1W=(1-m1W^2)×m1RW^2
p2W=(1-m2W^2)×m2RW^2
m1W: paraxial lateral magnification of the first focusing lens group when focusing on infinity at the short focal length extremity,
m1RW: paraxial lateral magnification of the optical system on the image side of the first focusing lens group when focusing on infinity at the short focal length end,
m2W: paraxial lateral magnification of the second focusing lens group when focusing on infinity at the short focal length end,
m2RW: the paraxial lateral magnification of the optical system on the image side of the second focusing lens group when focused on infinity at the short focal length extremity. The following conditional expressions (6') and (7') are satisfied:
10. The variable magnification optical system according to claim 6 ,
(6') 1.3<d1W/d2W<2.0
(7') 0.015<d1T/d2T<0.15
however,
d1W: the length from the aperture stop to the optical surface of the first focusing lens group closest to the aperture stop at the short focal length end,
d2W: the length from the aperture stop to the optical surface of the second focusing lens group closest to the aperture stop at the short focal length end,
d1T: the length from the aperture stop to the optical surface of the first focusing lens group closest to the aperture stop at the long focal length end,
d2T: the length from the aperture stop to the optical surface of the second focusing lens group that is closest to the aperture stop at the long focal length extremity. The optical system is composed of, in order from the object side, an object-side lens group, an aperture stop, and an image-side lens group,
the object-side lens group includes, in order from the object side, a first object-side lens group and a second object-side lens group;
the image-side lens group is composed of, in order from the object side, an image-side first lens group having a positive refractive power, an image-side intermediate lens group, and an image-side final lens group;
When changing magnification from the short focal length end to the long focal length end, the spacing between adjacent lens groups changes.
At least a part of the object-side second lens group includes an object-side focusing lens group that moves in the optical axis direction during focusing from infinity to a close distance,
At least a part of the image-side intermediate lens group has an image-side focusing lens group that moves in the optical axis direction during focusing from infinity to a close distance,
The object-side focusing lens group and the image-side focusing lens group move along different paths in the optical axis direction when focusing from infinity to a close distance,
When one of the object-side focusing lens group and the image-side focusing lens group, which has a larger absolute value of refractive power, is designated as the first focusing lens group, and the other of the image-side focusing lens group, which has a smaller absolute value of refractive power, is designated as the second focusing lens group, the following conditional expressions (1A) and (2A) are satisfied:
A variable magnification optical system characterized by:
(1A) 0.618≦｜f1/f2｜<1
(2A) 4.072≦｜p2T/p1T｜<30
however,
f1: focal length of the first focusing lens group,
f2: focal length of the second focusing lens group,
p1T: focus sensitivity of the first focusing lens group when focusing on infinity at the long focal length end,
p2T: focus sensitivity of the second focusing lens group when focusing on infinity at the long focal length end,
p1T=(1-m1T^2)×m1RT^2
p2T=(1-m2T^2)×m2RT^2
m1T: paraxial lateral magnification of the first focusing lens group when focusing on infinity at the long focal length end,
m1RT: paraxial lateral magnification of the optical system on the image side of the first focusing lens group when focusing on infinity at the long focal length end,
m2T: paraxial lateral magnification of the second focusing lens group when focusing on infinity at the long focal length end,
m2RT: the paraxial lateral magnification of the optical system on the image side of the second focusing lens group when focusing on infinity at the long focal length end. The following condition (3A) is satisfied:
12. The variable magnification optical system according to claim 11 .
(3A) 0.02<|p2W/p2T|<2.0
however,
p2W: focus sensitivity of the second focusing lens group when focusing on infinity at the short focal length end,
p2T: focus sensitivity of the second focusing lens group when focusing on infinity at the long focal length end,
p2W=(1-m2W^2)×m2RW^2
p2T=(1-m2T^2)×m2RT^2
m2W: paraxial lateral magnification of the second focusing lens group when focusing on infinity at the short focal length end,
m2RW: paraxial lateral magnification of the optical system on the image side of the second focusing lens group when focusing on infinity at the short focal length end,
m2T: paraxial lateral magnification of the second focusing lens group when focusing on infinity at the long focal length end,
m2RT: the paraxial lateral magnification of the optical system on the image side of the second focusing lens group when focusing on infinity at the long focal length end. The following condition (4A) is satisfied:
13. The variable magnification optical system according to claim 11 or 12 .
(4A) 0.7<|p1W/p1T|<7.0
however,
p1W: focus sensitivity of the first focusing lens group when focusing on infinity at the short focal length end,
p1T: focus sensitivity of the first focusing lens group when focusing on infinity at the long focal length end,
p1W=(1-m1W^2)×m1RW^2
p1T=(1-m1T^2)×m1RT^2
m1W: paraxial lateral magnification of the first focusing lens group when focusing on infinity at the short focal length extremity,
m1RW: paraxial lateral magnification of the optical system on the image side of the first focusing lens group when focusing on infinity at the short focal length end,
m1T: paraxial lateral magnification of the first focusing lens group when focusing on infinity at the long focal length end,
m1RT: the paraxial lateral magnification of the optical system on the image side of the first focusing lens group when focusing on infinity at the long focal length end. The following condition (5A) is satisfied:
14. The variable magnification optical system according to claim 11 ,
(5A) 0.1<|p2W/p1W|<10
however,
p1W: focus sensitivity of the first focusing lens group when focusing on infinity at the short focal length end,
p2W: focus sensitivity of the second focusing lens group when focusing on infinity at the short focal length end,
p1W=(1-m1W^2)×m1RW^2
p2W=(1-m2W^2)×m2RW^2
m1W: paraxial lateral magnification of the first focusing lens group when focusing on infinity at the short focal length extremity,
m1RW: paraxial lateral magnification of the optical system on the image side of the first focusing lens group when focusing on infinity at the short focal length end,
m2W: paraxial lateral magnification of the second focusing lens group when focusing on infinity at the short focal length end,
m2RW: the paraxial lateral magnification of the optical system on the image side of the second focusing lens group when focused on infinity at the short focal length extremity. The following conditional expressions (6A) and (7A) are satisfied:
15. A variable magnification optical system according to claim 11 .
(6A) 0.6<d1W/d2W<1.0
(7A) 3.0<d1T/d2T<30
however,
d1W: the length from the aperture stop to the optical surface of the first focusing lens group closest to the aperture stop at the short focal length end,
d2W: the length from the aperture stop to the optical surface of the second focusing lens group closest to the aperture stop at the short focal length end,
d1T: the length from the aperture stop to the optical surface of the first focusing lens group closest to the aperture stop at the long focal length end,
d2T: the length from the aperture stop to the optical surface of the second focusing lens group that is closest to the aperture stop at the long focal length extremity. 16. An interchangeable lens comprising the variable magnification optical system according to claim 1. 16. An image pickup apparatus comprising the variable magnification optical system according to claim 1.

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