JP7592995B2 - Zoom lens, lens barrel, interchangeable lens, and imaging device - Google Patents

Description

The present invention relates to a zoom lens, a lens barrel, an interchangeable lens, and an imaging device.

For example, users have a wide variety of requirements for interchangeable lenses for interchangeable lens cameras. In particular, the categories of large aperture zoom lenses with an F-number of less than 3, standard range zoom lenses equivalent to about 24mm to 70mm on 35mm film, and relatively high magnification zoom lenses including a standard range of about 28mm to 150mm, have received a certain amount of support from users and expectations are high. In addition, major user demands include the ability to take close-up shots, fast autofocus speeds, and quiet autofocus operation, in addition to relatively small size and high performance.

In terms of high performance, for example, in addition to having a resolution corresponding to an image sensor with 20 to 40 million pixels or more, it is required that there is little coma flare from the open aperture, high contrast, no distortion of point images even at the periphery of the angle of view, little chromatic aberration so that unnecessary coloring does not occur even in areas with large brightness differences, and that there is little distortion aberration and that straight lines can be depicted as straight lines. In terms of being relatively compact, it is desirable that the filter diameter is small and the overall length is also suppressed. In terms of close-up photography, it is desirable that a shooting distance of about 0.3 m can be secured in all zoom ranges. In terms of improving the speed and quietness of autofocus, it is desirable to reduce the amount of movement required for focusing and to suppress the load on the driving source of the focusing mechanism as much as possible, and it is required to optimize and minimise the refractive power of the optical system of the focusing unit, reduce the weight of the driven unit, and simplify the driving method.

As a zoom type suitable for high performance and high-speed focusing while ensuring a back focus amount compatible with interchangeable lens cameras, a configuration consisting of a first lens group with positive refractive power, a second lens group with negative refractive power, a third lens group with negative refractive power, and a subsequent lens group with positive refractive power, with the third lens group serving as a focus lens group, is known (for example, Patent Document 1).

Patent No. 5888038

However, the F-number of Patent Document 1 is relatively large, and there is room for improvement in terms of large aperture.

The present invention relates to a zoom lens, a lens barrel, an interchangeable lens, and an imaging device that have been improved in consideration of the above points. The first object of the present invention is to achieve both a small size, high performance, and a large aperture. The second object of the present invention is to achieve a small and quiet autofocus system.

The zoom lens of this embodiment is composed of, in order from the object side, a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having negative refractive power, and a subsequent lens group having positive refractive power, wherein an interval between adjacent lens groups changes when zooming from the short focal length end to the long focal length end, and the third lens group constitutes a focusing lens group that moves during focusing, the third lens group is composed of two lenses, one negative lens and one positive lens, at least one of the second lens group and the third lens group has at least one positive lens Gp, the subsequent lens group has an Nth lens group having negative refractive power and an interval between adjacent lens groups changes when zooming from the short focal length end to the long focal length end, and a surface closest to the image side of the second lens group is convex toward the image side, and the following conditional expressions (1), (4) and (8) are satisfied.
(1) 26<νdGp
(4) 0.1<f2/f3<1.0
(8) 0.5<|fN/frm|<2.5
however,
νdGp: Abbe number of the at least one positive lens Gp,
νdGp=(NdGp-1)/(NFGp-NCGp)
NdGp: the refractive index of the at least one positive lens Gp with respect to the d line,
NFGp: the refractive index of the at least one positive lens Gp with respect to the F line,
NCGp: the refractive index of the at least one positive lens Gp with respect to the C-line,
f2: the focal length of the second lens group,
f3: the focal length of the third lens group ,
fN: focal length of the Nth lens group,
frm: composite focal length of the subsequent lens group at intermediate focal length fm,
Intermediate focal length fm=(fw・ft) ^1/2
fw: focal length of the entire system when focused at infinity at the short focal length end,
ft: focal length of the entire system when focused at infinity at the long focal length end,
It is.

The lens barrel, interchangeable lens, and imaging device of this embodiment have any of the zoom lenses described above.

The present invention makes it possible to achieve both compact size and high performance as well as a large aperture. It also makes it possible to achieve a compact and quiet autofocus system.

FIG. 2 is a lens configuration diagram of a zoom lens according to a first numerical example. FIG. 11 is a lens configuration diagram of a zoom lens according to a second numerical example. FIG. 11 is a lens configuration diagram of a zoom lens according to a third numerical example. FIG. 13 is a lens configuration diagram of a zoom lens according to a fourth numerical example. FIG. 13 is a lens configuration diagram of a zoom lens according to a fifth numerical example. FIG. 13 is a lens configuration diagram of a zoom lens according to a sixth numerical example. FIG. 13 is a lens configuration diagram of a zoom lens according to Numerical Example 7. FIG. 13 is a lens configuration diagram of a zoom lens according to Numerical Example 8. FIG. 13 is a lens configuration diagram of a zoom lens according to a ninth numerical example. FIG. 13 is a lens configuration diagram of a zoom lens according to a tenth numerical example. FIG. 4 is an aberration curve diagram of the zoom lens of Numerical Example 1 at the short focal length extremity. FIG. 11 is an aberration curve diagram of the zoom lens of Numerical Example 1 at an intermediate focal length. FIG. 4 is an aberration curve diagram of the zoom lens of Numerical Example 1 at the long focal length end. FIG. 11 is an aberration curve diagram of the zoom lens at the short focal length extremity in Numerical Example 2. FIG. 11 is an aberration curve diagram of the zoom lens of Numerical Example 2 at an intermediate focal length. FIG. 11 is an aberration curve diagram of the zoom lens at the long focal length extremity in Numerical Example 2. FIG. 11 is an aberration curve diagram of the zoom lens at the short focal length extremity in Numerical Example 3. FIG. 11 is an aberration curve diagram of the zoom lens of Numerical Example 3 at an intermediate focal length. FIG. 11 is an aberration curve diagram of the zoom lens at the long focal length extremity in Numerical Example 3. FIG. 11 is an aberration curve diagram of the zoom lens at the short focal length extremity in Numerical Example 4. FIG. 11 is an aberration curve diagram of the zoom lens of Numerical Example 4 at an intermediate focal length. FIG. 11 is an aberration curve diagram of the zoom lens at the long focal length end of Numerical Example 4. FIG. 13 is an aberration curve diagram of the zoom lens at the short focal length extremity in Numerical Example 5. FIG. 13 is an aberration curve diagram of the zoom lens of Numerical Example 5 at an intermediate focal length. FIG. 13 is an aberration curve diagram of the zoom lens at the long focal length extremity in Numerical Example 5. FIG. 13 is an aberration curve diagram of the zoom lens of Numerical Example 6 at the short focal length extremity. FIG. 13 is an aberration curve diagram of the zoom lens of Numerical Example 6 at an intermediate focal length. FIG. 13 is an aberration curve diagram of the zoom lens at the long focal length extremity in Numerical Example 6. FIG. 13 is an aberration curve diagram of the zoom lens at the short focal length extremity in Numerical Example 7. FIG. 13 is an aberration curve diagram of the zoom lens of Numerical Example 7 at an intermediate focal length. FIG. 13 is an aberration curve diagram of the zoom lens at the long focal length extremity in Numerical Example 7. FIG. 13 is an aberration curve diagram of the zoom lens of Numerical Example 8 at the short focal length extremity. FIG. 13 is an aberration curve diagram of the zoom lens of Numerical Example 8 at an intermediate focal length. FIG. 13 is an aberration curve diagram of the zoom lens at the long focal length end of Numerical Example 8. FIG. 13 is an aberration curve diagram of the zoom lens of Numerical Example 9 at the short focal length extremity. FIG. 13 is an aberration curve diagram of the zoom lens of Numerical Example 9 at an intermediate focal length. FIG. 13 is an aberration curve diagram of the zoom lens at the long focal length extremity in Numerical Example 9. FIG. 23 is an aberration curve diagram of the zoom lens of Numerical Example 10 at the short focal length extremity. FIG. 23 is an aberration curve diagram of the zoom lens of Numerical Example 10 at an intermediate focal length. FIG. 23 is an aberration curve diagram of the zoom lens of Numerical Example 10 at the long focal length end. 1 is a first diagram showing an example of an imaging apparatus equipped with a zoom lens according to an embodiment of the present invention. FIG. 2 is a second diagram showing an example of an imaging apparatus equipped with the zoom lens of the present embodiment.

As shown in the lens configuration diagrams of Figures 1 to 10, the zoom lens of this embodiment is composed of, in order from the object side, a front lens group GF and a rear lens group GR.

Throughout all numerical embodiments 1 to 10 (FIGS. 1 to 10), the front lens group GF 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, and a third lens group G3 with negative refractive power.

The rear lens group GR has a positive refractive power as a whole throughout all of Numerical Examples 1 to 10 (FIGS. 1 to 10). I is the designed image surface.
In Numerical Examples 1 to 6 (FIGS. 1 to 6), the rear lens group GR is composed of, in order from the object side, 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, resulting in a positive-negative-negative-positive-negative six-group zoom lens configuration as a whole.
In Numerical Example 7 (FIG. 7), the rear lens group GR is composed of, in order from the object side, a fourth lens group G4 with positive refractive power, a fifth lens group G5 with negative refractive power, a sixth lens group G6 with positive refractive power, and a seventh lens group G7 with positive refractive power, resulting in a seven-group zoom lens configuration of positive-negative-negative-positive-negative-positive as a whole.
In Numerical Example 8 (FIG. 8), the rear lens group GR is composed of, in order from the object side, 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 positive refractive power, resulting in a positive-negative-negative-positive-positive six-group zoom lens configuration as a whole.
In Numerical Example 9 (FIG. 9), the rear lens group GR is composed of, in order from the object side, a fourth lens group G4 with positive refractive power, a fifth lens group G5 with positive refractive power, and a sixth lens group G6 with negative refractive power, resulting in a positive-negative-negative-positive-negative six-group zoom lens configuration as a whole.
In Numerical Example 10 (FIG. 10), the rear lens group GR is composed of, in order from the object side, a fourth lens group G4 with positive refractive power and a fifth lens group G5 with positive refractive power, resulting in a positive-negative-negative-positive-positive five-group zoom lens configuration as a whole.

According to the lens movement trajectories in Figures 1 to 10, when zooming from the short focal length end to the long focal length end, the spacing between adjacent lens groups (first lens group G1 to fifth lens group G5, first lens group G1 to sixth lens group G6, or first lens group G1 to seventh lens group G7) changes. For example, in the case of a six-group zoom lens configuration consisting of the first lens group G1 to sixth lens group G6, when zooming from the short focal length end to the long focal length end, the spacing between the first lens group G1 and the second lens group G2 increases, the spacing between the second lens group G2 and the third lens group G3 increases or decreases, the spacing between the third lens group G3 and the fourth lens group G4 decreases, the spacing between the fourth lens group G4 and the fifth lens group G5 increases or decreases, and the spacing between the fifth lens group G5 and the sixth lens group G6 decreases.

As described above, the rear lens group GR has at least two lens groups (for example, at least two of the fourth lens group G4, the fifth lens group G5, the sixth lens group G6, and the seventh lens group G7), and the two lens groups can be moved on the optical axis by changing the spacing between them when changing magnification from the short focal length end to the long focal length end. With this configuration, it is possible to effectively suppress fluctuations in spherical aberration and field curvature when changing magnification.

In addition, among the first lens group G1, the second lens group G2, the third lens group G3, and the subsequent lens group GR, at least two of the lens groups arranged in order from the object side can be moved on the optical axis by changing the spacing between each lens group when changing magnification from the short focal length end to the long focal length end. With this configuration, it is possible to effectively suppress fluctuations in spherical aberration and field curvature when changing magnification.

Furthermore, among the subsequent lens groups GR, the lens group arranged closest to the image side (for example, the fifth lens group G5, the sixth lens group G6, or the seventh lens group G7) can be fixed with respect to the image plane when changing magnification from the short focal length end to the long focal length end. By adopting such a configuration, it is possible to suppress backlash during manufacturing and decentering and backlash that occur when changing magnification.

In addition, all of the lens groups included in the zoom lens can be moved along the optical axis by changing the spacing between each lens group when changing magnification from the short focal length end to the long focal length end. With this configuration, it is possible to effectively suppress fluctuations in spherical aberration and field curvature when changing magnification.

In Numerical Examples 1 to 7 (FIGS. 1 to 7), the fifth lens group G5 constitutes an Nth lens group having negative refractive power whose spacing from each adjacent lens group changes when varying magnification from the short focal length end to the long focal length end.
In Numerical Example 8 (FIG. 8), the fourth lens group G4 constitutes an Nth lens group having negative refractive power, the distance between which changes between adjacent lens groups when varying magnification from the short focal length extremity to the long focal length extremity.
In Numerical Example 9 (FIG. 9), the sixth lens group G6 constitutes an Nth lens group having negative refractive power, the spacing between adjacent lens groups changing during zooming from the short focal length extremity to the long focal length extremity.
Note that the embodiment in which the fifth lens group G5 is the Nth lens group having negative refractive power is merely an example, and various design modifications are possible. For example, the rear lens group GR may be provided with two or more lens groups having negative refractive power, and one of the lens groups may be the Nth lens group.

In all of Numerical Examples 1 to 6, the first lens group G1 is composed of a negative lens 11, a positive lens 12, and a positive lens 13, in that order from the object side.
In Numerical Example 7, the first lens group G1 is composed of a negative lens 11A, a positive lens 12A, and a positive lens 13A.
In Numerical Example 8, the first lens group G1 is composed of a negative lens 11B, a positive lens 12B, and a positive lens 13B.
In Numerical Example 9, the first lens group G1 is composed of a negative lens 11C, a positive lens 12C, and a positive lens 13C.
In Numerical Example 10, the first lens group G1 is composed of a negative lens 11D, a positive lens 12D, and a positive lens 13D.

In all of Numerical Examples 1 to 6, the second lens group G2 is composed of, in order from the object side, a negative lens 21, a negative lens 22, and a positive lens 23.
In Numerical Example 7, the second lens group G2 is composed of, in order from the object side, a negative lens 21A, a negative lens 22A, and a positive lens 23A.
In Numerical Example 8, the second lens group G2 is composed of, in order from the object side, a negative lens 21B, a negative lens 22B, and a positive lens 23B.
In Numerical Example 9, the second lens group G2 is composed of, in order from the object side, a negative lens 21C, a negative lens 22C, and a positive lens 23C.
In Numerical Example 10, the second lens group G2 is composed of, in order from the object side, a negative lens 21D, a negative lens 22D, and a positive lens 23D.

In all of Numerical Examples 1 to 6, the third lens group G3 is composed of a negative lens element 31 and a positive lens element 32, in that order from the object side.
In Numerical Example 7, the third lens group G3 is composed of, in order from the object side, a negative lens element 31A and a positive lens element 32A.
In Numerical Example 8, the third lens group G3 is composed of, in order from the object side, a negative lens element 31B and a positive lens element 32B.
In Numerical Example 9, the third lens group G3 is composed of, in order from the object side, a negative lens element 31C and a positive lens element 32C.
In Numerical Example 10, the third lens group G3 is composed of, in order from the object side, a negative lens element 31D and a positive lens element 32D.

In Numerical Examples 1-3, the fourth lens group G4 is composed of an aperture stop SP, a positive lens 41, a positive lens 42, and a negative lens 43, in that order from the object side.
In Numerical Example 4-6, the fourth lens group G4 is composed of, in order from the object side, a positive lens 41', an aperture stop SP, a positive lens 42', and a negative lens 43'.
In Numerical Example 7, the fourth lens group G4 is composed of, in order from the object side, a positive lens 41A, an aperture stop SP, a positive lens 42A, and a negative lens 43A.
In Numerical Example 8, the fourth lens group G4 is composed of, in order from the object side, a negative lens element 41B and a positive lens element 42B.
In Numerical Example 9, the fourth lens group G4 is composed of, in order from the object side, an aperture stop SP, a positive lens 41C, a positive lens 42C, and a negative lens 43C.
In Numerical Example 10, the fourth lens group G4 is composed of, in order from the object side, an aperture stop SP, a positive lens 41D, a positive lens 42D, and a negative lens 43D.

In Numerical Example 1-3, the fifth lens group G5 is composed of, in order from the object side, a negative lens element 51 and a positive lens element 52.
In Numerical Example 4-6, the fifth lens group G5 is composed of, in order from the object side, a negative lens 51', a negative lens 52', and a positive lens 53'.
In Numerical Example 7, the fifth lens group G5 is composed of, in order from the object side, a negative lens 51A, a negative lens 52A, and a positive lens 53A.
In Numerical Example 8, the fifth lens group G5 is composed of, in order from the object side, an aperture stop SP, a positive lens 51B, a positive lens 52B, and a negative lens 53B.
In Numerical Example 9, the fifth lens group G5 is composed of, in order from the object side, a positive lens 51C, a negative lens 52C, a positive lens 53C, and a positive lens 54C.
In Numerical Example 10, the fifth lens group G5 is composed of, in order from the object side, a positive lens 51D, a positive lens 52D, a negative lens 53D, and a positive lens 54D.

In Numerical Examples 1-5, the sixth lens group G6 is composed of a negative lens 61, a positive lens 62, and a positive lens 63, in that order from the object side.
In Numerical Example 6, the sixth lens group G6 is composed of, in order from the object side, a negative lens 61', a positive lens 62', a positive lens 63', and a negative lens 64'.
In Numerical Example 7, the sixth lens group G6 is composed of, in order from the object side, a negative lens element 61A and a positive lens element 62A.
In Numerical Example 8, the sixth lens group G6 is composed of, in order from the object side, a positive lens 61B, a positive lens 62B, a negative lens 63B, and a positive lens 64B.
In Numerical Example 9, the sixth lens group G6 is composed of, in order from the object side, a negative lens element 61C, a positive lens element 62C, and a positive lens element 63C.

In Numerical Example 7, the seventh lens group G7 is composed of, in order from the object side, a negative lens 71A and a positive lens 72A.

The zoom lens of this embodiment is small and highly functional, yet has a large aperture with an F-number of less than 3, and can cover a zoom range equivalent to 24 to 70 mm or 28 to 150 mm in 35 mm film equivalent. It also has a compact focus group configuration that is ideal for making autofocus compact and quiet.

Generally speaking, as the angle of view increases, coma, astigmatism, lateral chromatic aberration, field curvature, and distortion tend to increase. On the other hand, as the telephoto lens increases, the effects of spherical aberration and axial chromatic aberration tend to increase. In addition, as the aperture increases, coma and spherical aberration increase, and the entire optical system and focus section tend to become longer in order to correct these aberrations.

The zoom lens of this embodiment has a configuration that solves the above-mentioned problems in correcting aberrations, and in particular the problem of increasing the length of the focus lens group.

In positive-lead zoom lenses, focusing is often performed in the second lens group, which has the strongest negative power and is located closer to the object than the aperture. However, focusing in the second lens group is prone to cause changes in magnification due to focusing, and there are also disadvantages in that it is difficult to reduce weight and achieve high focusing speed.

In contrast, the zoom lens of this embodiment divides the negative lens group with the strongest power described above into the second lens group G2 and the third lens group G3, and uses only the third lens group G3 as the focus lens group that moves during focusing, thereby making the focus lens group smaller and lighter, thereby achieving faster and quieter autofocus. Specifically, the third lens group G3, which is the focus lens group, moves (extends) toward the object side when focusing from an object at infinity to a close object.

In addition, because there is no longer a need to secure the extension space required for focusing with the conventional second lens group, the distance between the first lens group G1 and the second lens group G2 can be set small at the short focal length end, which contributes to improving the ability to correct distortion and field curvature. Also, by contributing to magnification by moving the position of each lens group, including the third lens group G3, relative to the image plane, the freedom of design is increased, leading to improved performance.

In the zoom lens of this embodiment, when changing magnification from the short focal length end to the long focal length end, the first lens group G1 in particular is moved (extended) toward the object side relative to the image plane, improving the ability to control the height of the light rays passing through the lens group and making the entire system smaller.

Here, if the balance of aberration exchange between the second lens group G2 and the third lens group G3 is lost, it may lead to fluctuations in imaging performance due to focusing, so appropriate conditions are set regarding the exchange of aberration between the second lens group G2 and the third lens group G3. In particular, appropriate conditions are set for controlling chromatic aberration in large-aperture zoom lenses that cover a wide-angle range, standard range, and semi-telephoto range.

Specifically, in the zoom lens of this embodiment, it is preferable that at least one of the second lens group G2 and the third lens group G3 has at least one positive lens Gp and that the following conditional expressions (1), (1A), and (1B) are satisfied.
(1) 26<νdGp
(1A) 29<νdGp
(1B) 29<νdGp<45
however,
νdGp: Abbe number of at least one positive lens Gp,
νdGp=(NdGp-1)/(NFGp-NCGp)
NdGp: the refractive index of at least one positive lens Gp for the d line,
NFGp: the refractive index of at least one positive lens Gp for the F line;
NCGp: the refractive index of at least one positive lens Gp with respect to the C-line;
It is.

Conditional expressions (1), (1A), and (1B) define the appropriate range of Abbe numbers for the positive lens Gp (any positive lens) included in at least one of the second lens group G2 and the third lens group G3. By satisfying conditional expression (1), it is possible to appropriately set the exchange of aberration with the paired negative lens for achromatization, to satisfactorily correct chromatic aberration during focusing, and to achieve high image quality, and it is also possible to appropriately set the manufacturing error sensitivity and obtain excellent initial performance. This effect is more pronounced when conditional expressions (1A) and (1B) are satisfied.
If the lower limit of condition (1) is exceeded, the exchange of aberration with the paired negative lens becomes excessive due to achromatism, and the fluctuation of chromatic aberration during focusing becomes large, degrading image quality, or the sensitivity to manufacturing errors becomes high, making it difficult to obtain the initial performance.
If the upper limit of conditional expression (1B) is exceeded, the difference in Abbe number with respect to the paired negative lens for achromatization becomes too small, which may make it difficult to control chromatic aberration.

In the zoom lens of this embodiment, it is preferable that the third lens group G3 has at least one positive lens and satisfies the following conditional expression (2).
(2) 1.8<Nd3p
however,
Nd3p: the refractive index for the d-line of at least one positive lens in the third lens group G3,
It is.

At least one positive lens in the third lens group G3 may be the same positive lens as the positive lens Gp included in at least one of the second lens group G2 and the third lens group G3 described above, or may be a different positive lens.

Because the third lens group G3 is a focus lens group, the lens group thickness must be set appropriately to efficiently secure the extension space when focusing on close distances.

Conditional expression (2) defines the appropriate range of refractive index of at least one positive lens in the third lens group G3. By satisfying conditional expression (2), it is possible to reduce the size of at least one positive lens in the third lens group G3, and thus the size of the entire optical system, and to effectively suppress fluctuations in spherical aberration due to changes in shooting distance.
If the lower limit of the conditional expression (2) is exceeded, it becomes necessary to reduce the radius of curvature of the positive lens in the third lens group G3 in order to obtain power for appropriate chromatic aberration control with the negative lens paired with the third lens group G3, and the central thickness of the positive lens becomes excessively large, narrowing the extension space of the focus lens group, which may result in the entire optical system becoming larger in size in order to secure the necessary extension space. Also, the aberration correction ability may become insufficient, causing large fluctuations in spherical aberration due to changes in shooting distance.

It is preferable that the zoom lens of this embodiment satisfies the following conditional expression (3).
(3) 1.65<NdGp
however,
NdGp: the refractive index of at least one positive lens Gp for the d line,
It is.

The third lens group G3, which is a focus lens group, has negative power and extends toward the object side when focusing on close distances. This means that it is necessary to secure space between the second lens group G2 and the third lens group G3 for this extension, and it is therefore necessary to set the lens group thicknesses of the second lens group G2 and the third lens group G3 appropriately.

Conditional expression (3) defines an appropriate range of refractive index for the positive lens Gp (positive lens satisfying conditional expression (1)) included in at least one of the second lens group G2 and the third lens group G3. By satisfying conditional expression (3), it is possible to reduce the size of the positive lens Gp included in at least one of the second lens group G2 and the third lens group G3, and thus the size of the entire optical system, and to effectively suppress fluctuations in spherical aberration due to changes in shooting distance.
If the lower limit of the conditional expression (3) is exceeded, in order to obtain power for appropriate chromatic aberration control with the negative lens paired with at least one of the second lens group G2 and the third lens group G3, it becomes necessary to reduce the radius of curvature of the positive lens Gp, and the central thickness of the positive lens Gp becomes excessively large, narrowing the extension space of the focus lens group, which may result in the entire optical system becoming larger in size in order to secure the necessary extension space. Also, the aberration correction ability may become insufficient, causing large fluctuations in spherical aberration due to changes in shooting distance.

It is preferable that the zoom lens of this embodiment satisfies the following conditional expressions (4), (4A), and (4B).
(4) 0.1<f2/f3<1.0
(4A) 0.1<f2/f3<0.6
(4B) 0.2<f2/f3<0.5
however,
f2: focal length of the second lens group G2,
f3: focal length of the third lens group G3,
It is.

In the zoom lens of this embodiment, the third lens group G3 is formed by dividing the second lens group of a typical positive-lead zoom lens, and by dividing the negative power and allocating it to the focusing lens group, it is possible to suppress changes in image magnification during focusing.

Conditional expressions (4), (4A), and (4B) define the ratio of the focal lengths of the second lens group G2 and the third lens group G3 in this configuration (the appropriate range of the focal length of one of the second lens group G2 and the third lens group G3 relative to the other). By satisfying conditional expression (4), it is possible to suppress the change in image magnification and to reduce the focusing movement amount of the third lens group G3, thereby shortening the entire lens. This effect is more pronounced when conditional expressions (4A) and (4B) are satisfied.
If the upper limit of conditional expression (4) is exceeded, the power of the third lens group G3 becomes too strong, and there is a concern that the change in image magnification will be too large.
If the lower limits of the conditional expressions (4) and (4A) are exceeded, the power of the third lens group G3 becomes too weak, the focusing movement amount increases, and this may lead to an increase in the length and size of the entire lens.

In the zoom lens of this embodiment, the surface of the second lens group G2 closest to the image side can be made convex toward the image side. This makes it possible to reduce the height of the off-axis light beam passing through a high position of the lenses in the second lens group G2 toward the third lens group G3, and also makes it possible to reduce the radial size of the third lens group G3, which is a focus lens group and is therefore arranged with a certain amount of space between it and the second lens group G2.

In the zoom lens of this embodiment, the surface of the third lens group G3 closest to the object side can be made concave toward the object side. This allows the surface of the third lens group G3 closest to the object side, which is a focus lens group and therefore arranged with a certain amount of space between it and the second lens group G2, to refract the off-axis light beam from the second lens group G2 closer to the object side, thereby reducing the radial size of the third lens group G3.

In the zoom lens of this embodiment, it is preferable that the surface of the second lens group G2 closest to the image side is a convex surface facing the image side, and the surface of the third lens group G3 closest to the object side is a concave surface facing the object side, and that the following conditional expressions (5) and (5A) are satisfied.
(5) 0.1<R3gf/R2gl<10.0
(5A) 0.2<R3gf/R2gl<5.0
however,
R2gl: radius of curvature of the surface of the second lens group G2 closest to the image side,
R3gf: radius of curvature of the surface of the third lens group G3 closest to the object,
It is.

Because the third lens group G3 is a focusing lens group, the surface spacing between it and the second lens group G2 changes depending on the shooting distance, but because the second lens group G2 and the third lens group G3 can be considered to be configured by dividing a negative lens group that was originally one unit, it is necessary to appropriately suppress the fluctuation in aberration caused by the change in surface spacing. In particular, because a thick light beam passes through at the short focal length end, it is necessary to appropriately set the exchange of spherical aberration between the second lens group G2 and the third lens group G3.

Conditional expressions (5) and (5A) define the appropriate range of the radius of curvature of the surface (final surface) closest to the image side of the second lens group G2 and the surface (leading surface) closest to the object side of the third lens group G3. By satisfying conditional expression (5), the direction of the curvature of the surface (final surface) closest to the image side of the second lens group G2 and the surface (leading surface) closest to the object side of the third lens group G3 can be aligned, making it possible to reduce the minimum air gap between the second lens group G2 and the third lens group G3, and to ensure a large amount of extension during close-range focusing, thereby shortening the minimum shooting distance. This effect is more pronounced when conditional expression (5A) is satisfied.
If either the upper or lower limit of condition (5) is exceeded, the exchange of spherical aberration between the second lens group G2 and the third lens group G3 becomes excessive, and there is a risk of significant fluctuation in imaging performance due to focusing.

In the zoom lens of this embodiment, the third lens group G3 can have a negative lens and a positive lens. In order to suppress aberration fluctuations during focusing, it is necessary that the exchange of various aberrations is completed to a certain extent within the third lens group G3, which is the focusing lens group. By having a negative lens and a positive lens in the third lens group G3, which is the focusing lens group, it is possible to complete the exchange of chromatic aberration in particular within the third lens group G3, thereby suppressing changes in chromatic aberration due to focusing.

In the zoom lens of this embodiment, the third lens group G3 can be configured with two lenses: one negative lens and one positive lens. By handling the chromatic aberration in the third lens group G3, which is the focusing lens group, with the minimum number of lenses, one negative lens and one positive lens, it is possible to configure the third lens group G3 to be small and lightweight.

In the zoom lens of this embodiment, the third lens group G3 can be made up of two lenses, one negative lens and one positive lens, positioned in that order from the object side. By making the third lens group G3, which moves out to the object side when focusing on close distances, out of two lenses, one negative lens and one positive lens, positioned in that order from the object side, it is possible to move the principal point position of the third lens group G3 closer to the second lens group G2, thereby shortening the minimum shooting distance.

In the zoom lens of this embodiment, the third lens group G3 is composed of two lenses, one negative lens and one positive lens, which are positioned in order from the object side, and each negative lens and positive lens can be cemented. If there is excessive exchange of aberration between the third lens group G3, which is the focusing lens group, and the other lens groups, the aberration fluctuation during focusing becomes large, and the image performance is likely to fluctuate depending on the shooting distance. By configuring the third lens group G3, which is the focusing lens group, with two lenses, one negative lens and one positive lens, which are the minimum necessary for chromatic aberration correction, it is possible to reduce the size of the third lens group G3, which is the focusing lens group, while improving the chromatic aberration correction ability and suppressing the image performance fluctuation during focusing. By forming each negative lens and positive lens into a cemented lens, it is possible to reduce the number of mechanical components and contribute to the weight reduction of the focusing lens group while balancing the aberration correction ability and manufacturing error sensitivity in the third lens group G3. In addition, by arranging one negative lens and one positive lens in order from the object side, it is possible to move the principal point position of the third lens group G3 closer to the second lens group G2, thereby shortening the minimum shooting distance.

In the zoom lens of this embodiment, the third lens group G3 is made up of two lenses, one negative lens and one positive lens, positioned in that order from the object side, and each of the negative lens and the positive lens is cemented together. It is preferable that the following conditional expressions (6) and (6A) are satisfied.
(6) 1<Ndp/Ndn<1.5
(6A) 1<Ndp/Ndn<1.4
however,
Ndp: the refractive index of the positive lens in the third lens group G3 at the d line,
Ndn: the refractive index of the negative lens in the third lens group G3 at the d line,
It is.

The third lens group G3, which is a focusing lens group, needs to have a small group thickness. Conditional expressions (6) and (6A) stipulate the appropriate ratio of the refractive indexes of the positive lens and the negative lens in the third lens group G3. By satisfying conditional expression (6), it is possible to reduce the size of the third lens group G3 and thus the entire optical system. This effect is more pronounced when conditional expression (6A) is satisfied.
If either the upper limit or the lower limit of conditional expression (6) is exceeded, it will be necessary to reduce the radius of curvature of either the positive lens or the negative lens in the third lens group G3 in order to compensate for the refractive index ratio that has become an issue, which will increase the group thickness of the third lens group G3 and may result in the overall optical system becoming larger.

It is preferable that the zoom lens of this embodiment satisfies the following conditional expression (7).
(7) N3a>1.7
however,
N3a: the average value of the refractive indexes for the d line of all the lenses in the third lens group G3,
It is.

The third lens group G3, which is a focusing lens group, needs to have a small group thickness. Conditional expression (7) defines an appropriate range for the average refractive index within the third lens group G3. By satisfying conditional expression (7), it is possible to reduce the size of the third lens group G3 and, in turn, the entire optical system.
If the lower limit of conditional expression (7) is exceeded, it will be necessary to reduce the radius of curvature of each lens in order to obtain negative power for the third lens group G3, which may increase the group thickness of the third lens group G3 and result in an increase in the size of the entire optical system.

In the zoom lens of this embodiment, the subsequent lens group has an N-th lens group having negative refractive power, the spacing between each of the adjacent lens groups changing during zooming from the short focal length end to the long focal length end, and it is preferable that the following conditional expressions (8) and (8A) be satisfied:
(8) 0.5<|fN/frm|<2.5
(8A) 0.7<|fN/frm|<2.1
however,
fN: focal length of the Nth lens group,
frm: composite focal length of the subsequent lens group at intermediate focal length fm,
Intermediate focal length fm=(fw・ft) ^1/2
fw: focal length of the entire system when focused on infinity at the short focal length end,
ft: focal length of the entire system when focused at infinity at the long focal length end,
It is.

By providing a negative lens group (Nth lens group) whose spacing from adjacent lens groups changes during magnification change in the rear lens group GR, which has positive refractive power overall, it acts as a compensator during magnification change, ensuring the amount of back focus at the short focal length end and improving aberration correction capability. In addition, by moving the Nth lens group in the rear lens group GR during magnification change, it is possible to improve the aberration correction capability of the entire system while contributing to magnification change.

Conditional expressions (8) and (8A) define an appropriate range of the focal length of the Nth lens group over the entire range of magnification change from the short focal length end to the long focal length end. By satisfying conditional expression (8), it is possible to reduce the size of the entire optical system and improve the imaging performance by performing favorable aberration correction. This effect is more pronounced when conditional expression (8A) is satisfied.
If the upper limit of conditional expression (8) is exceeded, the power of the Nth lens unit becomes too weak, and the amount of movement during zooming becomes large, which may result in an increase in the size of the entire optical system.
If the lower limit of conditional expression (8) is exceeded, the power of the Nth lens group will be too strong, and the exchange of aberrations with the other lens groups will be excessive. As a result, the error sensitivity will deteriorate and errors accompanying the movement due to magnification change will likely cause changes in imaging performance.

In the zoom lens of this embodiment, the first lens group G1 can be configured with three lenses, one negative lens and two positive lenses. In order to increase the magnification, particularly to increase the focal length at the long focal length end, the composite magnification of the lens groups after the second lens group G2 at the long focal length end must be increased, and the aberration generated in the first lens group G1 will be magnified on the image plane accordingly. For this reason, in order to increase the magnification, it is necessary to sufficiently suppress the amount of aberration generated in the first lens group G1, and therefore it is desirable to configure the first lens group G1 with three lenses, one negative lens and two positive lenses. In addition, by limiting the first lens group G1 to a three-lens configuration, the height of the light passing through the first lens group G1 can be suppressed, which is particularly effective in reducing the size of the first lens group G1 in the radial direction.

Specifically, it is desirable for the first lens group G1 to be configured so that, from the object side, it has a negative meniscus lens with a convex surface facing the object side, a positive lens with a strong convex surface facing the object side, and one positive lens behind that. By adopting this configuration, it is possible to sufficiently suppress the amount of aberration occurring in the first lens group G1, and it is possible to improve the ability to correct mainly chromatic aberration of magnification while avoiding an increase in the overall length.

It is preferable that the zoom lens of this embodiment satisfies the following conditional expression (9).
(9) 0.6<D1/D2<1.0
however,
D1: the thickness of the first lens group G1 on the optical axis,
D2: the thickness of the second lens group G2 on the optical axis,
It is.

Conditional expression (9) defines an appropriate ratio of the thicknesses of the first lens group G1 and the second lens group G2 on the optical axis. By satisfying conditional expression (9), it is possible to reduce the size of the first lens group G1 and the second lens group G2.
If the upper limit of conditional expression (9) is exceeded, the thickness on the optical axis of the first lens group G1 will become too large, and the off-axis light beam, particularly at the short focal length end, will be high from the optical axis, which may cause the first lens group G1 to become large in the radial direction.
If the lower limit of conditional expression (9) is exceeded, the thickness on the optical axis of the second lens group G2 will become too large, and the off-axis light beam, particularly at the short focal length end, will be high from the optical axis, and the first lens group G1 and the second lens group G2 may also become large in the radial direction.

It is preferable that the zoom lens of this embodiment satisfies the following conditional expressions (10) and (10A).
(10)-20<f1/f23t<-6
(10A)-10<f1/f23t<-6
however,
f1: focal length of the first lens group G1,
f23t: composite focal length of the second lens group G2 and the third lens group G3 when focusing on infinity at the long focal length end,
It is.

Conditional expressions (10) and (10A) define an appropriate range for the focal length of the first lens group G1 relative to the composite focal length of the second lens group G2 and the third lens group G3 when focusing on infinity at the long focal length extremity. By satisfying conditional expression (10), the front lens diameter and the total optical length can be reduced, and various aberrations such as curvature of field and distortion can be effectively corrected. This effect is more pronounced when conditional expression (10A) is satisfied.
If the upper limits of conditional expressions (10) and (10A) are exceeded, the front lens diameter and the total optical length may become large.
If the lower limit of condition (10) is exceeded, the positive power of the first lens group G1 will become too strong, causing excessive aberrations to occur, particularly large field curvature and distortion, which may make it difficult to correct each aberration.

It is preferable that the zoom lens of this embodiment satisfies the following conditional expression (11).
(11) 0.20<D(2R-3F)T/D(2F-3R)T<0.60
however,
D(2R-3F)T: the distance on the optical axis from the surface of the second lens group G2 closest to the image side to the surface of the third lens group G3 closest to the object side when focusing on infinity at the long focal length end,
D(2F-3R)T: the distance on the optical axis from the surface of the second lens group G2 closest to the object to the surface of the third lens group G3 closest to the image when focusing on infinity at the long focal length end,
It is.

Conditional expression (11) defines an appropriate range for the distance between the second lens group G2 and the third lens group G3 relative to the total thickness of the second lens group G2 and the third lens group G3 when focusing on infinity at the long focal length extremity.
By satisfying conditional expression (11), the sensitivity of the focus lens group can be made appropriate, and it is possible to improve the performance during focusing without increasing the size of the optical system.
If the upper limit of conditional expression (11) is exceeded, the distance between the second lens group G2 and the third lens group G3 becomes too wide, which increases the focusing movement amount of the third lens group G3, which is the focus lens group, and may result in an increase in the overall lens length.
If the lower limit of conditional expression (11) is exceeded, the focus sensitivity of the third lens group G3, which is the focus lens group, may become too high, which may result in a deterioration in autofocus accuracy, or the balance of aberration correction between the groups before and after the focus lens group may be easily lost, which may result in a deterioration in imaging performance associated with focusing.

It is preferable that the zoom lens of this embodiment satisfies the following conditional expressions (12), (12A), (13), and (13A).
(12) 2.0<|f3/ffw|<5.0
(12A) 2.5<|f3/ffw|<4.5
(13) 1.0<|f3/fft|<4.0
(13A) 1.5<|f3/fft|<3.5
however,
f3: focal length of the third lens group G3,
ffw: the composite focal length of the first lens group G1, the second lens group G2, and the third lens group G3 when focusing on infinity at the short focal length extremity,
fft: the composite focal length of the first lens group G1, the second lens group G2, and the third lens group G3 when focusing on infinity at the long focal length extremity,
It is.

Because the third lens group G3 contributes not only to focusing but also to magnification, it is important to set it to an appropriate focal length range to prevent the balance of aberrations from being lost, resulting in increased aberrations or an increase in the size of the lens.

Conditional expressions (12), (12A), (13), and (13A) indicate "the appropriate range of the focal length of the third lens group G3, which is the lens group on the object side of the aperture stop" at each zoom point.
By satisfying conditional expressions (12) and (13), the overall lens system can be made compact, various aberrations can be favorably corrected, and accurate manufacture and assembly can be facilitated. This effect is more pronounced when conditional expressions (12A) and (13A) are satisfied.
If the upper limits of conditional expressions (12) and (13) are exceeded, the sensitivity to manufacturing errors will be reduced, but the burden of magnification change on the other lens groups will be increased, and the "amount of displacement associated with magnification change" of each lens group will increase. In order to ensure these amounts of displacement, it will be disadvantageous for size reduction and will also be disadvantageous in terms of aberration correction.
If the lower limits of the conditional expressions (12) and (13) are exceeded, the contribution of the third lens group G3 to the zoom ratio becomes relatively large, and the zoom ratio burden of the other lens groups becomes small. This is advantageous in terms of size reduction of the entire zoom lens system and aberration correction, but it is not preferable from a practical standpoint because the sensitivity to manufacturing errors increases, making it difficult to manufacture and assemble with high precision.

In this embodiment, it is possible to configure a high-performance zoom lens having a small and lightweight focus lens group that is capable of zooming from a wide angle to a standard range with a large aperture while suppressing an increase in size, particularly in the radial direction. From the viewpoint of effectively achieving suppression of an increase in size of the entire system and high performance while ensuring a certain degree of back focus amount, it is preferable to satisfy the following conditional expressions (14), (14A), (15), and (15A).
(14) 1.5<Bfw/Ya<4.0
(14A) 2.0<Bfw/Ya<3.0
(15) 1.5<Bfw/fw<4.0
(15A) 1.5<Bfw/fw<3.0
however,
Bfw: air-equivalent distance (back focus amount) from the surface closest to the image side of the subsequent lens group to the image plane when focusing on infinity at the short focal length end,
Ya: maximum image height,
fw: focal length of the entire system when focused at infinity at the short focal length end,
It is.

By satisfying conditional expressions (14) and (15), it is possible to effectively suppress an increase in size of the entire system and achieve high performance while ensuring a certain degree of back focal length. This effect is more pronounced when conditional expressions (14A) and (15A) are satisfied.
If the upper limits of the conditional expressions (14) and (15) are exceeded, the back focus becomes too large, leading to an increase in the size of the entire lens system (an increase in the overall lens length).
If the lower limits of the conditional expressions (14) and (15) are exceeded, it becomes difficult to ensure the required back focal length, and the optical performance is deteriorated.

In the zoom lens of this embodiment, from the viewpoint of effectively achieving a small and lightweight focus group while also achieving high performance and a large aperture, it is preferable that the F-number be 3 or less.

In addition, in any of the numerical examples 1-10 described below, it is possible to move the image by moving any lens group or partial lens group in a direction approximately perpendicular to the optical axis, making it possible to configure a so-called image stabilization optical system. For example, if the fifth lens group G5 in numerical examples 1-7, the fourth lens group G4 in numerical example 8, the sixth lens group G6 in numerical example 9, the fourth lens group G4 or the fifth lens group G5 in numerical example 10, or a part of each lens group is made into an anti-vibration lens group, image stabilization can be performed with a relatively small lens group, which is preferable because it prevents the lenses from becoming too large.

In addition, it is even more desirable for the rear group, which has positive power overall, to have a positive fourth lens group including an aperture stop, a negative fifth lens group, and a positive sixth lens group. Since the fourth lens group G4 and the sixth lens group G6, which have positive power within the rear lens group GR, have a large exchange of aberrations and are highly sensitive to manufacturing errors, it is preferable for them to move together when changing magnification. This makes it possible to reduce sensitivity to manufacturing errors while maintaining high aberration correction capabilities.

A zoom lens having a positive fourth lens group including a diaphragm, a negative fifth lens group, and a positive sixth lens group as the rear group having positive power as a whole as described above, can set an appropriate focal length range of the sixth lens group G6 with respect to the fourth lens group G4 by satisfying the following conditional expressions (16) and (16A), and can achieve a balance between aberration correction and sensitivity to manufacturing errors.
(16) 0.3<f4/f6<0.9
(16A) 0.45<f4/f6<0.75
however,
f4: focal length of the fourth lens group G4,
f6: focal length of the sixth lens group G6,
It is.

By satisfying conditional expression (16), it is possible to achieve a good balance between aberration correction and sensitivity to manufacturing errors. This effect is more pronounced when conditional expression (16A) is satisfied.
If the upper limit of conditional expression (16) is exceeded, the refractive power of the fourth lens group G4 becomes too small, the aberration correction ability decreases, the load of aberration correction in the sixth lens group G6 increases, and the balance of the manufacturing error sensitivity may be lost. In addition, the off-axis light after the fourth lens group G4 becomes high, and the entire lens may become long.
If the lower limit of conditional expression (16) is exceeded, the refractive power of the sixth lens group G6 will become too small, making it more difficult to control the exit pupil position, particularly at the wide-angle end (short focal length end), and there is a risk that the aberration correction ability will decrease in order to ensure an appropriate back focus amount.

As described above, the third lens group G3, which is a focus lens group, can be composed of two lenses, a negative lens and a positive lens. This improves the chromatic aberration correction ability of the third lens group G3. If the following conditional expression (17) is satisfied for each of the negative lens and the positive lens in the third lens group G3, better optical performance can be achieved.
(17) 1.4<ν3n/ν3p<3.0
however,
ν3n: Abbe number of the negative lens in the third lens group G3 for the d line,
ν3p: Abbe number of the positive lens in the third lens group G3 for the d line,
It is.

Here, the Abbe number for the d-line is calculated by the following formula.
νd=(Nd-1)/(NF-NC)
however,
Nd: refractive index at d line,
NF: refractive index at F line,
NC: refractive index at C line,
It is.

By satisfying conditional expression (17), the ability to correct chromatic aberration in the third lens group G3 can be improved, and changes in imaging performance due to focusing can be suppressed.
If either the upper or lower limit of condition (17) is exceeded, appropriate correction of chromatic aberration becomes difficult, and the exchange of chromatic aberration with other lens groups increases, possibly resulting in deterioration of the change in imaging performance during focusing.

It is preferable that the zoom lens of this embodiment satisfies the following conditional expression (18).
(18) 2.5<f1/fw<6.0
however,
f1: focal length of the first lens group G1,
fw: focal length of the entire system when focused at infinity at the short focal length end,
It is.

Conditional expression (18) indicates "an appropriate range of the focal length of the first lens group G1 relative to the focal length of the entire system at the short focal length end." By appropriately setting the focal length of the first lens group G1 so as to satisfy conditional expression (18), it is possible to reduce the size of the first lens group G1 and thus the entire lens system, prevent the focal length at the short focal length end from becoming too long, and achieve good control of coma aberration and spherical aberration.
If the upper limit of conditional expression (18) is exceeded, the focal length of the first lens group G1 becomes too long, and the light passing through the first lens group G1 becomes high and large in the radial direction.
If the lower limit of conditional expression (18) is exceeded, it becomes difficult to control coma and spherical aberration at the long focal length extremity, and these aberrations may worsen, or the focal length at the short focal length extremity may become too long.

It is preferable that the zoom lens of this embodiment satisfies the following conditional expressions (19) and (19A).
(19) 2.0<frw/Ya<3.5
(19A) 2.5<frw/Ya<3.1
however,
frw: focal length of the subsequent lens group when focusing on infinity at the short focal length end,
Ya: maximum image height,
It is.

In conditional expressions (19) and (19A), the maximum image height refers to the half diagonal length of the effective image surface size. For example, in the case of a digital camera, the half diagonal length of the effective pixel range of the image sensor is the maximum image height.

A positive-lead type zoom lens such as that of this embodiment has a power arrangement in which the object side is negative and the image side is positive. Increasing the power of the positive rear group (rear lens group GR) is advantageous for making the entire system smaller, but is disadvantageous in ensuring the back focus amount. It also becomes difficult to ensure the back focus amount at the short focal length end. By appropriately setting the power of the positive rear group (rear lens group GR), it is possible to ensure the back focus amount required by the camera system with good performance while suppressing the increase in size of the entire system.

Conditions (19) and (19A) indicate "an appropriate range for the focal length of the positive rear lens group (rear lens group GR) at the short focal length extremity."
By satisfying conditional expression (19), it is possible to reduce the size of the entire lens system, to satisfactorily correct various aberrations, and to appropriately set the sensitivity to manufacturing errors. This effect is more pronounced when conditional expression (19A) is satisfied.
If the upper limit of condition (19) is exceeded, the power of the positive rear lens group (rear lens group GR) becomes weak, making it easier to ensure the amount of back focus, but the overall system becomes longer and larger.
If the lower limit of conditional expression (19) is exceeded, it becomes more difficult to achieve both an adequate back focal length and control of spherical aberration, making it difficult to correct the spherical aberration, or the exchange of aberration between the lens groups becomes excessive, which may worsen the sensitivity to manufacturing errors.

In the zoom lens of this embodiment, when changing the magnification from the short focal length extremity to the long focal length extremity, the first lens group G1 moves (is extended) toward the object side with respect to the image plane. In this case, it is preferable that the zoom lens of this embodiment satisfies the following conditional expression (20).
(20) 0.2<M1/f1<0.6
however,
M1: the amount of movement of the first lens group G1 in the optical axis direction when changing magnification from the short focal length end to the long focal length end (the amount of extension toward the object side),
f1: the focal length of the first lens group G1.

Conditional expression (20) defines the ratio between the amount of movement (extension) of the first lens group G1 during zooming and the focal length of the first lens group G1. By satisfying conditional expression (20), it is possible to reduce the size of the first lens group G1 and thus the entire lens system, and to effectively correct various aberrations to achieve excellent optical performance and prevent deterioration of imaging performance due to manufacturing errors such as the inclination of the lens barrel.
If the upper limit of conditional expression (20) is exceeded, the overall lens length at the short focal length extremity becomes too short, or the overall lens length at the long focal length extremity becomes too long. If the overall lens length at the short focal length extremity becomes too short, the movement space of each lens group becomes limited, and the contribution to magnification becomes small, making it difficult to correct the overall aberration. If the overall lens length at the long focal length extremity becomes too long, not only does it hinder the miniaturization in the overall length direction, but it also increases the radial size in order to ensure the peripheral light amount at the long focal length extremity, and it is also easy to invite deterioration of the imaging performance due to manufacturing errors such as the inclination of the lens barrel.
If the lower limit of conditional expression (20) is exceeded, the contribution of the second lens group G2 and the third lens group G3 to the magnification is reduced, and the burden on the positive rear group increases overall. Alternatively, the refractive power of the second lens group G2 and the third lens group G3 must be strengthened. In either case, this leads to the deterioration of various aberrations. In addition, the overall lens length at the short focal length extremity becomes long, increasing the height of the light rays passing through the first lens group G1, and leading to an increase in the size of the first lens group G1.

It is preferable that the zoom lens of this embodiment satisfies the conditions (21) and (21A).
(21) 1.00<(1-Mt^2)×MRt^2<8.00
(21A) 1.00<(1-Mt^2)×MRt^2<3.00
however,
Mt: lateral magnification of the third lens group G3 when focusing on infinity at the long focal length end,
MRt: lateral magnification of the subsequent lens group when focusing on infinity at the long focal length end,
It is.

Conditional expressions (21) and (21A) indicate "the appropriate range of the focus sensitivity of the third lens group G3, which is the focus lens group at the long focal length end." By satisfying conditional expression (21), it is possible to make the sensitivity of the third lens group G3, which is the focus lens group, appropriate and improve the performance during focusing without increasing the size of the optical system. This effect is more pronounced when conditional expression (21A) is satisfied.
If the upper limit of conditional expression (21) is exceeded, the focus sensitivity of the third lens group G3, which is the focus lens group, may become too high, which may result in a deterioration in autofocus accuracy, or the balance of aberration correction between the groups before and after the focus lens group may be easily lost, which may result in a deterioration in imaging performance during focusing.
If the lower limits of conditional expressions (21) and (21A) are exceeded, the focus sensitivity of the third lens group G3, which is the focus lens group, will become too low, making it necessary to increase the distance between the second lens group G2 and the third lens group G3, which could result in an increase in the overall lens length.

Specific numerical examples 1-10 are shown. In the aberration curve diagram, the solid line indicates the sagittal cross-sectional aberration of the d-line, the dashed line indicates the meridional cross-sectional aberration of the d-line, the dashed line indicates the sagittal cross-sectional aberration of the g-line, and the dashed two-dot line indicates the meridional cross-sectional aberration of the g-line. In the aberration curve diagram and the table, f indicates the focal length of the entire system, F indicates the F-number, w indicates the half angle of view, y indicates the image height, Ya indicates the maximum image height, R indicates the radius of curvature, D indicates the lens thickness or lens spacing, Nd indicates the refractive index at the d-line, νd indicates the Abbe number at the d-line, BF indicates the back focus, K indicates the conic constant of the aspheric surface, A4 indicates the fourth-order aspheric coefficient, A6 indicates the sixth-order aspheric coefficient, A8 indicates the eighth-order aspheric coefficient, and A10 indicates the tenth-order aspheric coefficient. The focal length, F-number, and half angle of view of the entire system are shown in the order of the short focal length end - the intermediate focal length - the long focal length end. The unit of length is [mm]. Here, when the reciprocal of the paraxial radius of curvature (paraxial curvature) is C and the height from the optical axis is H, the aspheric surface is defined by the following formula.
x=CH ² /[1+[1-(1+K)C ² H ² ] ^1/2 ]+A ₄ H ⁴ +A ₆ H ⁶ +A ₈ H ⁸ +A ₁₀ H ¹⁰

[Numerical Example 1]
Fig. 1, Fig. 11 to Fig. 13 and Tables 1 to 5 show the zoom lens of Numerical Example 1. Fig. 1 is a lens configuration diagram. Figs. 11, 12 and 13 are aberration curve diagrams at the short focal length end, the intermediate focal length end and the long focal length end. Table 1 shows surface data, Table 2 shows aspheric surface data, Table 3 shows variable distance data, Table 4 shows zoom lens group data and Table 5 shows conditional expression data.

The zoom lens of Numerical Example 1 is composed of, from the object side, a front lens group GF and a rear lens group GR. The front lens group GF 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, and a third lens group G3 with negative refractive power. The rear lens group GR has positive refractive power as a whole, and is composed of, from the object side, a fourth lens group G4 with positive refractive power, a fifth lens group (Nth lens group) G5 with negative refractive power, and a sixth lens group G6 with positive refractive power.

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

The second lens group G2 is composed of, in order from the object side, a negative meniscus lens 21 convex toward the object side, a biconcave negative lens 22, and a biconvex positive lens 23 (positive lens Gp). The negative meniscus lens 21 is composed of a hybrid lens in which an aspherical layer made of a synthetic resin material is bonded to the object side surface of the glass lens. The biconvex positive lens 23 is composed of a hybrid lens in which an aspherical layer made of a synthetic resin material is bonded to the image side surface of the glass lens. The biconcave negative lens 22 and the biconvex positive lens 23 are cemented together.

The third lens group G3 is composed of, in order from the object side, a biconcave negative lens 31 and a biconvex positive lens 32 (positive lens Gp). The biconcave negative lens 31 and the biconvex positive lens 32 are cemented together.

The fourth lens group G4 is composed of, in order from the object side, an aperture stop SP, a biconvex positive lens 41, a biconvex positive lens 42, and a negative meniscus lens 43 that is convex toward the image side. The biconvex positive lens 41 has aspheric surfaces on both sides. The biconvex positive lens 42 and the negative meniscus lens 43 are cemented together.

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

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

(Table 1)
f=16.5~28.0~48.6, F=2.9~2.9~2.9, w=42.0~27.0~16.1, Ya=14.24
Surface number RD Nd νd Glass type (glass material)
1 349.940 2.17 1.85896 22.73 S-NPH5(OHARA)
2 125.000 4.08 1.74100 52.64 S-LAL61(OHARA)
3 303.720 0.15
4 63.693 6.42 1.73400 51.47 S-LAL59(OHARA)
5 198.470 D1
6* 123.440 0.10 1.52970 42.70 Optical resin
7 68.456 1.50 1.80400 46.53 S-LAH65VS(OHARA)
8 16.537 8.56
9 -51.212 1.20 1.80400 46.53 S-LAH65VS(OHARA)
10 66.763 5.00 1.73800 32.33 S-NBH53V(OHARA)
11 -47.401 0.12 1.52970 42.70 Optical resin
12* -44.020 D2
13 -33.451 0.90 1.73400 51.47 S-LAL59(OHARA)
14 33.451 3.75 1.85883 30.00 NBFD30(HOYA)
15 -424.930 D3
16 Aperture 1.40
17* 41.636 6.20 1.49700 81.54 S-FPL51(OHARA)
18* -62.583 0.20
19 75.999 6.88 1.59522 67.73 S-FPM2(OHARA)
20 -33.020 1.21 1.84666 23.78 S-TIH53W(OHARA)
21 -51.212 D4
22 -140.160 1.20 1.80100 34.97 S-LAM66(OHARA)
23 22.069 4.32 1.92286 20.88 E-FDS1-W(HOYA)
24 53.657 D5
25 43.199 1.10 2.00100 29.13 TAFD55(HOYA)
26 19.825 6.30 1.49700 81.61 FCD1(HOYA)
27 116.850 0.32
28* 47.716 7.65 1.49700 81.54 S-FPL51(OHARA)
29* -33.842 BF
* denotes a rotationally symmetric aspheric surface.
(Table 2)
Face number K A4 A6 A8 A10
6 0 1.55019E-05 -2.22450E-08 2.51370E-11 1.87942E-15
12 0 3.29948E-06 -4.54242E-09 -6.26158E-11 3.89206E-13
17 0 -9.95529E-06 -2.30967E-09 -2.60998E-11 9.49283E-14
18 0 -1.02858E-06 -2.30427E-09 -3.63509E-11 9.32441E-14
28 0 -3.22716E-06 5.53584E-09 -3.85931E-11 8.74751E-14
29 0 1.10134E-06 -1.08719E-08 2.37398E-12 -1.65988E-13
(Table 3)
D1 D2 D3 D4 D5 BF
Short focal length end f=16.5 1.250 6.218 27.029 1.491 13.817 39.247
Intermediate focal length f=28.1 10.231 6.796 11.477 8.698 6.610 50.002
Long focal length end f=48.5 34.205 8.317 4.050 13.562 1.751 61.927
(Table 4)
Lens group Focal length 1st lens group 142.6
Second lens group: -27.25
Third lens group: -62.31
Fourth lens group 29.34
Fifth lens group: -57.33
6th lens group 53.89
1st to 3rd lens groups: Short focal length end: -19.03, Long focal length end: -20.54
Subsequent lens group: Short focal length end: 39.57, Long focal length end: 37.44
(Table 5)
(1) 26<νdGp
Positive lens 23 (positive lens Gp): 32.32
Positive lens 32 (positive lens Gp): 30.00
(2) 1.8<Nd3p: 1.85883
(3) 1.65<NdGp
Positive lens 23 (positive lens Gp): 1.73800
Positive lens 32 (positive lens Gp): 1.85883
(4) 0.1<f2/f3<1.0: 0.44
(5) 0.1<R3gf/R2gl<10.0:0.76
(6) 1<Ndp/Ndn<1.5:1.07
(7) N3a > 1.7: 1.796
(8) 0.5<|fN/frm|<2.5:1.53
(9) 0.6<D1/D2<1.0:0.78
(10) -20<f1/f23t<-6: -9.47
(11) 0.20<D(2R-3F)T/D(2F-3R)T<0.60:0.281
(12) 2.0<|f3/ffw|<5.0:3.27
(13) 1.0<|f3/fft|<4.0:2.38
(14) 1.5<Bfw/Ya<4.0:2.76
(15) 1.5<Bfw/fw<4.0:2.39
(16) 0.3<f4/f6<0.9:0.544
(17) 1.4<ν3n/ν3p<3.0:1.72
(18) 2.5<f1/fw<6.0:3.60
(19) 2.0<frw/Ya<3.5:2.78
(20) 0.2<M1/f1<0.6:0.24
(21) 1.00<(1-Mt^2)×MRt^2<8.00:2.545

[Numerical Example 2]
Fig. 2, Fig. 14 to Fig. 16 and Tables 6 to 10 show the zoom lens of Numerical Example 2. Fig. 2 is a lens configuration diagram. Figs. 14, 15 and 16 are aberration curve diagrams at the short focal length end, the intermediate focal length end and the long focal length end. Table 6 shows surface data, Table 7 shows aspheric surface data, Table 8 shows variable distance data, Table 9 shows zoom lens group data and Table 10 shows conditional expression data.

The lens configuration of the zoom lens in Numerical Example 2 is similar to the lens configuration of the zoom lens in Numerical Example 1, except for the following points.
(1) The positive lens 32 (positive lens Gp) of the third lens group G3 is not a biconvex positive lens, but is a plano-convex positive lens that is convex on the object side.

(Table 6)
f=16.5~28.5~48.6, F=2.9~2.9~2.9, w=42.0~26.8~16.1, Ya=14.24
Surface number RD Nd νd Glass type (glass material)
1 368.508 2.17 1.85896 22.73 S-NPH5(OHARA)
2 125.000 4.58 1.74100 52.64 S-LAL61(OHARA)
3 480.387 0.15
4 59.429 6.61 1.67790 55.34 S-LAL12(OHARA)
5 182.982 D1
6* 151.330 0.10 1.52970 42.70 Optical resin
7 74.978 1.50 1.80400 46.53 S-LAH65VS(OHARA)
8 16.435 8.49
9 -46.380 1.40 1.77250 49.60 S-LAH66(OHARA)
10 55.204 5.22 1.73800 32.33 S-NBH53V(OHARA)
11 -49.343 0.20 1.52970 42.70 Optical resin
12* -42.716 D2
13 -36.457 1.30 1.72000 50.23 S-LAL10(OHARA)
14 30.646 3.90 1.85025 30.05 S-NBH57(OHARA)
15∞D3
16 Aperture 1.30
17* 42.436 6.32 1.49710 81.56 M-FCD1(HOYA)
18* -60.195 0.20
19 72.187 6.87 1.59522 67.73 S-FPM2(OHARA)
20 -33.293 1.40 1.84666 23.78 S-TIH53W(OHARA)
21 -53.968 D4
22 -113.518 1.40 1.80100 34.97 S-LAM66(OHARA)
23 22.123 4.47 1.92286 20.88 E-FDS1-W(HOYA)
24 57.089 D5
25 42.894 1.40 2.00100 29.13 TAFD55(HOYA)
26 19.871 5.70 1.49700 81.61 FCD1(HOYA)
27 84.692 0.20
28* 40.337 8.14 1.49710 81.56 M-FCD1(HOYA)
29* -34.034 BF
* denotes a rotationally symmetric aspheric surface.
Table 7
Face number K A4 A6 A8 A10
6 0 1.69364E-05 -3.01171E-08 4.58285E-11 -1.94966E-14
12 0 4.53006E-06 2.78274E-09 -1.18907E-10 5.85653E-13
17 0 -9.60746E-06 -4.72907E-09 -8.90566E-12 3.79932E-14
18 0 -1.89625E-06 -7.40575E-09
28 0 -3.77184E-06 -6.97085E-09 2.12525E-11 8.54793E-14
29 0 2.03163E-06 -1.59070E-08
Table 8
D1 D2 D3 D4 D5 BF
Short focal length end f=16.5 1.000 6.038 26.757 2.000 13.175 38.990
Intermediate focal length f=28.5 3.259 7.502 9.030 9.763 5.412 53.533
Long focal length end f=48.6 31.922 8.255 3.950 13.175 2.000 61.584
Table 9
Lens group Focal length 1st lens group 130.3
Second lens group: -26.17
Third lens group: -64.79
Fourth lens group 29.53
Fifth lens group: -56.09
Sixth lens group: 52.93
1st to 3rd lens groups: Short focal length end: -19.01, Long focal length end: -26.63
Subsequent lens group: Short focal length end: 39.61, Long focal length end: 35.59
(Table 10)
(1) 26<νdGp
Positive lens 23 (positive lens Gp): 32.32
Positive lens 32 (positive lens Gp): 30.05
(2) 1.8<Nd3p: 1.85025
(3) 1.65<NdGp
Positive lens 23 (positive lens Gp): 1.73800
Positive lens 32 (positive lens Gp): 1.85025
(4) 0.1<f2/f3<1.0: 0.40
(5) 0.1<R3gf/R2gl<10.0:0.85
(6) 1<Ndp/Ndn<1.5:1.08
(7) N3a > 1.7: 1.785
(8) 0.5<|fN/frm|<2.5:1.51
(9) 0.6<D1/D2<1.0:0.80
(10) -20<f1/f23t<-6: -8.81
(11) 0.20<D(2R-3F)T/D(2F-3R)T<0.60:0.280
(12) 2.0<|f3/ffw|<5.0:3.41
(13) 1.0<|f3/fft|<4.0:2.43
(14) 1.5<Bfw/Ya<4.0:2.74
(15) 1.5<Bfw/fw<4.0:2.37
(16) 0.3<f4/f6<0.9: 0.558
(17) 1.4<ν3n/ν3p<3.0:1.67
(18) 2.5<f1/fw<6.0:3.29
(19) 2.0<frw/Ya<3.5:2.78
(20) 0.2<M1/f1<0.6:0.25
(21) 1.00<(1-Mt^2)×MRt^2<8.00:1.996

[Numerical Example 3]
Fig. 3, Fig. 17 to Fig. 19 and Tables 11 to 15 show the zoom lens of Numerical Example 3. Fig. 3 is a lens configuration diagram. Figs. 17, 18 and 19 are aberration curve diagrams at the short focal length end, the intermediate focal length end and the long focal length end. Table 11 shows surface data, Table 12 shows aspheric surface data, Table 13 shows variable distance data, Table 14 shows zoom lens group data and Table 15 shows conditional expression data.

The lens configuration of the zoom lens of Numerical Example 3 is similar to the lens configuration of the zoom lens of Numerical Example 1, except for the following points.
(1) The positive lens 32 (positive lens Gp) in the third lens group G3 is not a biconvex positive lens, but is a positive meniscus lens convex toward the object side.

Table 11
f=16.5~28.2~48.6, F=2.9~2.9~2.9, w=41.9~26.9~16.1, Ya=14.24
Surface number RD Nd νd Glass type (glass material)
1 444.922 2.00 1.84666 23.78 S-TIH53W(OHARA)
2 119.286 4.81 1.72916 54.68 S-LAL18(OHARA)
3 517.614 0.15
4 60.346 6.50 1.75500 52.32 S-LAH97(OHARA)
5 177.527 D1
6* 123.260 0.10 1.52970 42.70 Optical resin
7 67.227 1.50 1.77250 49.60 S-LAH66(OHARA)
8 15.727 8.82
9 -47.511 1.70 1.83481 42.74 S-LAH55VS(OHARA)
10 108.989 4.86 1.74077 27.79 S-TIH13(OHARA)
11 -49.540 0.10 1.52970 42.70 Optical resin
12* -50.382 D2
13 -43.191 0.90 1.71300 53.87 S-LAL8(OHARA)
14 36.368 2.83 1.90366 31.34 S-LAH95(OHARA)
15 1014.485 D3
16 Aperture 1.30
17* 40.844 5.72 1.49700 81.54 S-FPL51(OHARA)
18* -58.146 0.20
19 59.425 6.16 1.60300 65.44 S-PHM53(OHARA)
20 -39.266 1.80 1.84666 23.78 S-TIH53W(OHARA)
21 -67.092 D4
22 -119.956 1.50 1.80100 34.97 S-LAM66(OHARA)
23 19.726 4.42 1.92286 20.88 E-FDS1-W(HOYA)
24 48.277 D5
25 37.619 1.00 2.00100 29.13 TAFD55(HOYA)
26 16.997 5.95 1.49700 81.61 FCD1(HOYA)
27 143.659 1.69
28* 49.008 8.14 1.49700 81.54 S-FPL51(OHARA)
29* -32.352 BF
* denotes a rotationally symmetric aspheric surface.
(Table 12)
Face number K A4 A6 A8 A10
6 0 1.61683E-05 -2.82648E-08 4.04557E-11 -1.88010E-14
12 0 4.69990E-06 -9.81276E-09 -5.19004E-11 4.01179E-13
17 0 -9.89042E-06 -5.22417E-09 -3.25786E-11 5.66871E-14
18 0 -3.00384E-06 -3.99768E-09 -4.11839E-11 3.58618E-14
28 0 -6.28769E-06 1.27418E-08 -1.65986E-10 5.48898E-13
29 0 -3.21298E-06 -1.46508E-08 -8.55460E-11 -9.52581E-14
(Table 13)
D1 D2 D3 D4 D5 BF
Short focal length end f=16.5 1.000 5.987 29.148 3.380 10.469 36.363
Intermediate focal length f=28.2 6.434 7.273 11.186 9.219 4.634 49.517
Long focal length end f=48.6 31.516 9.410 4.067 12.327 1.527 59.479
(Table 14)
Lens group Focal length 1st lens group 126.1
Second lens group: -23.68
Third lens group: -82.42
Fourth lens group: 28.57
Fifth lens group: -50.74
Sixth lens group: 51.94
1st to 3rd lens groups: Short focal length end: -19.62, Long focal length end: -27.61
Subsequent lens group: Short focal length end: 40.00, Long focal length end: 36.20
Table 15
(1) 26<νdGp
Positive lens 23 (positive lens Gp): 27.79
Positive lens 32 (positive lens Gp): 31.34
(2) 1.8<Nd3p: 1.90366
(3) 1.65<NdGp
Positive lens 23 (positive lens Gp): 1.74077
Positive lens 32 (positive lens Gp): 1.90366
(4) 0.1<f2/f3<1.0:0.29
(5) 0.1<R3gf/R2gl<10.0:0.86
(6) 1<Ndp/Ndn<1.5:1.11
(7) N3a > 1.7: 1.808
(8) 0.5<|fN/frm|<2.5:1.34
(9) 0.6<D1/D2<1.0:0.79
(10) -20<f1/f23t<-6: -8.38
(11) 0.20<D(2R-3F)T/D(2F-3R)T<0.60:0.311
(12) 2.0<|f3/ffw|<5.0:4.20
(13) 1.0<|f3/fft|<4.0:2.99
(14) 1.5<Bfw/Ya<4.0:2.55
(15) 1.5<Bfw/fw<4.0:2.21
(16) 0.3<f4/f6<0.9:0.550
(17) 1.4<ν3n/ν3p<3.0:1.72
(18) 2.5<f1/fw<6.0:3.15
(19) 2.0<frw/Ya<3.5:2.81
(20) 0.2<M1/f1<0.6:0.25
(21) 1.00<(1-Mt^2)×MRt^2<8.00:1.996

[Numerical Example 4]
Fig. 4, Fig. 20 to Fig. 22 and Tables 16 to 20 show the zoom lens of Numerical Example 4. Fig. 4 is a lens configuration diagram. Figs. 20, 21 and 22 are aberration curve diagrams at the short focal length end, the intermediate focal length end and the long focal length end. Table 16 shows surface data, Table 17 shows aspheric surface data, Table 18 shows variable distance data, Table 19 shows zoom lens group data and Table 20 shows conditional expression data.

The lens configuration of the zoom lens of Numerical Example 4 is similar to the lens configuration of the zoom lens of Numerical Example 1, except for the following points.
(1) The positive lens 23 (positive lens Gp) of the second lens group G2 is not a hybrid lens, but is an aspheric lens having an aspheric surface on the image side.
(2) The fourth lens group G4 is composed of, in order from the object side, a biconvex positive lens 41', an aperture stop SP, a biconvex positive lens 42', and a negative meniscus lens 43' convex toward the image side. The biconvex positive lens 42' has an aspheric surface on the object side. The biconvex positive lens 42' and the negative meniscus lens 43' are cemented together.
(3) The fifth lens group G5 is composed of, in order from the object side, a biconcave negative lens 51', a biconcave negative lens 52', and a positive meniscus lens 53' convex toward the object side. The biconcave negative lens 52' and the positive meniscus lens 53' are cemented together.
(4) The positive lens 62 in the sixth lens group G6 is not a positive meniscus lens convex toward the object side, but is a biconvex positive lens.
(5) The biconvex positive lens 63 in the sixth lens group G6 does not have aspheric surfaces on both sides, but has an aspheric surface only on the object side.

Table 16
f=16.4~28.2~48.5, F=2.9~2.9~2.9, w=42.0~27.1~16.1, Ya=14.24
Surface number RD Nd νd Glass type (glass material)
1 2692.178 2.37 1.84666 23.78 S-TIH53W(OHARA)
2 151.356 5.10 1.80400 46.53 S-LAH65VS(OHARA)
3 3686.730 0.15
4 71.758 6.39 1.75500 52.32 S-LAH97(OHARA)
5 233.756 D1
6* 78.496 0.05 1.52970 42.70 Optical resin
7 57.064 1.50 1.83481 42.74 S-LAH55VS(OHARA)
8 15.892 9.04
9 -91.408 1.40 1.69680 55.53 S-LAL14(OHARA)
10 27.396 6.42 1.68948 31.02 L-TIM28(OHARA)
11* -103.276 D2
12 -27.881 1.00 1.53775 74.70 S-FPM3(OHARA)
13 80.466 2.98 1.90366 31.34 S-LAH95(OHARA)
14 -1034.624 D3
15 34.665 6.01 1.55332 71.68 M-FCD500(HOYA)
16 -68.601 1.00
17 Aperture 2.30
18* 52.301 6.32 1.61881 63.85 M-PCD4(HOYA)
19 -32.784 3.48 1.84666 23.78 S-TIH53W(OHARA)
20 -73.735 D4
21 -437.375 1.40 2.00100 29.13 TAFD55(HOYA)
22 69.701 1.67
23 -103.385 1.40 1.80610 40.93 S-LAH53V(OHARA)
24 27.165 3.97 1.94595 17.98 FDS18-W(HOYA)
25 166.724 D5
26 104.775 1.40 1.84666 23.78 S-TIH53W(OHARA)
27 26.064 6.25 1.49700 81.54 S-FPL51(OHARA)
28 -52.988 0.15
29* 46.590 6.20 1.49710 81.56 M-FCD1(HOYA)
30 -51.757 BF
* denotes a rotationally symmetric aspheric surface.
Table 17
Face number K A4 A6 A8 A10
6 0 1.09778E-05 -1.68183E-08 1.45658E-11 -1.22128E-14
11 44.65936 1.20183E-06 1.13729E-08 -2.02364E-10 7.90405E-13
18 0 -8.72559E-06 -8.20277E-09 -1.07667E-12 -3.25462E-14
29 0 -3.33429E-06 1.13062E-08 -4.50608E-11 1.15988E-13
Table 18
D1 D2 D3 D4 D5 BF
Short focal length end f=16.2 1.000 6.696 23.511 1.500 9.848 37.499
Intermediate focal length f=28.2 2.967 8.038 6.739 7.349 4.039 52.387
Long focal length end f=48.5 32.172 8.363 1.500 9.848 1.500 62.838
Table 19.
Lens group Focal length 1st lens group 138.4
Second lens group -25.00
Third lens group: -72.58
Fourth lens group 27.48
Fifth lens group: -39.26
Sixth lens group: 41.23
1st to 3rd lens groups: Short focal length end: -18.94, Long focal length end: -25.92
Subsequent lens group: Short focal length end: 40.53, Long focal length end: 36.73
Table 20
(1) 26<νdGp
Positive lens 23 (positive lens Gp): 31.02
Positive lens 32 (positive lens Gp): 31.34
(2) 1.8<Nd3p: 1.90366
(3) 1.65<NdGp
Positive lens 23 (positive lens Gp): 1.68948
Positive lens 32 (positive lens Gp): 1.90366
(4) 0.1<f2/f3<1.0: 0.34
(5) 0.1<R3gf/R2gl<10.0:0.27
(6) 1<Ndp/Ndn<1.5:1.24
(7) N3a > 1.7: 1.721
(8) 0.5<|fN/frm|<2.5:1.02
(9) 0.6<D1/D2<1.0:0.76
(10) -20<f1/f23t<-6: -9.17
(11) 0.20<D(2R-3F)T/D(2F-3R)T<0.60:0.272
(12) 2.0<|f3/ffw|<5.0:3.83
(13) 1.0<|f3/fft|<4.0:2.80
(14) 1.5<Bfw/Ya<4.0:2.63
(15) 1.5<Bfw/fw<4.0:2.28
(16) 0.3<f4/f6<0.9:0.666
(17) 1.4<ν3n/ν3p<3.0:2.38
(18) 2.5<f1/fw<6.0:3.42
(19) 2.0<frw/Ya<3.5:2.85
(20) 0.2<M1/f1<0.6:0.26
(21) 1.00<(1-Mt^2)×MRt^2<8.00:2.388

[Numerical Example 5]
Fig. 5, Fig. 23 to Fig. 25 and Tables 21 to 25 show the zoom lens of Numerical Example 5. Fig. 5 is a lens configuration diagram. Figs. 23, 24 and 25 are aberration curve diagrams at the short focal length end, the intermediate focal length end and the long focal length end. Table 21 shows surface data, Table 22 shows aspheric surface data, Table 23 shows variable distance data, Table 24 shows zoom lens group data and Table 25 shows conditional expression data.

The lens configuration of the zoom lens in Numerical Example 5 is similar to the lens configuration of the zoom lens in Numerical Example 4.

Table 21
f=16.5~28.1~48.5, F=2.9~2.9~2.9, w=42.0~26.7~16.1, Ya=14.24
Surface number RD Nd νd Glass type (glass material)
1 2451.756 2.26 1.84666 23.78 S-TIH53W(OHARA)
2 165.561 4.46 1.78800 47.37 S-LAH64(OHARA)
3 2335.532 0.15
4 63.208 6.26 1.75500 52.32 S-LAH97(OHARA)
5 181.795 D1
6* 114.364 0.05 1.52970 42.70 Optical resin
7 73.287 1.50 1.83481 42.74 S-LAH55VS(OHARA)
8 16.000 9.01
9 -112.009 1.40 1.73400 51.47 S-LAL59(OHARA)
10 44.410 5.52 1.68948 31.02 L-TIM28(OHARA)
11* -85.317 D2
12 -27.853 1.40 1.60300 65.44 S-PHM53(OHARA)
13 191.609 3.02 1.85478 24.80 S-NBH56(OHARA)
14 -128.098 D3
15 34.776 6.49 1.55332 71.68 M-FCD500(HOYA)
16 -58.842 1.00
17 Aperture 2.30
18* 56.494 6.22 1.61881 63.85 M-PCD4(HOYA)
19 -33.032 1.40 1.84666 23.78 S-TIH53W(OHARA)
20 -79.415 D4
21 -147.237 1.40 2.00100 29.13 TAFD55(HOYA)
22 107.016 1.16
23 -135.833 1.40 1.80610 40.93 S-LAH53V(OHARA)
24 25.162 3.71 1.94595 17.98 FDS18-W (HOYA)
25 102.481 D5
26 107.499 1.40 1.85478 24.80 S-NBH56(OHARA)
27 26.020 5.78 1.49700 81.54 S-FPL51(OHARA)
28 -54.639 0.15
29* 58.071 5.89 1.49710 81.56 M-FCD1(HOYA)
30 -40.822 BF
* denotes a rotationally symmetric aspheric surface.
Table 22
Face number K A4 A6 A8 A10
6 0 1.20367E-05 -2.07979E-08 1.96627E-11 -1.80585E-14
11 28.84614 -6.92047E-08 9.39420E-10 -1.20445E-10 4.12078E-13
18 0 -9.05652E-06 -1.05668E-08 3.82396E-12 -4.30322E-14
29 0 -3.22815E-06 1.43652E-08 -6.60275E-11 2.01020E-13
Table 23
D1 D2 D3 D4 D5 BF
Short focal length end f=16.5 1.000 7.993 23.724 2.000 12.349 38.614
Intermediate focal length f=28.1 13.985 8.005 10.125 7.970 6.419 46.297
Long focal length end f=48.5 31.376 8.847 2.000 12.349 2.000 58.980
Table 24
Lens group Focal length 1st lens group 131.3
Second lens group: -24.65
Third lens group: -75.24
Fourth lens group 27.40
Fifth lens group: -37.90
Sixth lens group: 41.67
1st to 3rd lens groups: Short focal length end: -19.11, Long focal length end: -26.69
Subsequent lens group: Short focal length end: 42.50, Long focal length end: 37.16
Table 25
(1) 26<νdGp
Positive lens 23 (positive lens Gp): 31.02
(2) 1.8<Nd3p: 1.85478
(3) 1.65<NdGp
Positive lens 23 (positive lens Gp): 1.68948
(4) 0.1<f2/f3<1.0:0.33
(5) 0.1<R3gf/R2gl<10.0:0.33
(6) 1<Ndp/Ndn<1.5:1.16
(7) N3a > 1.7: 1.729
(8) 0.5<|fN/frm|<2.5:0.94
(9) 0.6<D1/D2<1.0:0.75
(10) -20<f1/f23t<-6: -8.65
(11) 0.20<D(2R-3F)T/D(2F-3R)T<0.60:0.288
(12) 2.0<|f3/ffw|<5.0:3.94
(13) 1.0<|f3/fft|<4.0:2.82
(14) 1.5<Bfw/Ya<4.0:2.71
(15) 1.5<Bfw/fw<4.0:2.35
(16) 0.3<f4/f6<0.9: 0.657
(17) 1.4<ν3n/ν3p<3.0:2.64
(18) 2.5<f1/fw<6.0:3.09
(19) 2.0<frw/Ya<3.5:2.99
(20) 0.2<M1/f1<0.6:0.23
(21) 1.00<(1-Mt^2)×MRt^2<8.00:2.214

[Numerical Example 6]
Fig. 6, Fig. 26 to Fig. 28 and Tables 26 to 30 show the zoom lens of Numerical Example 6. Fig. 6 is a lens configuration diagram. Figs. 26, 27 and 28 are aberration curve diagrams at the short focal length end, the intermediate focal length end and the long focal length end. Table 26 shows surface data, Table 27 shows aspheric surface data, Table 28 shows variable distance data, Table 29 shows zoom lens group data and Table 30 shows conditional expression data.

The lens configuration of the zoom lens of Numerical Example 6 is similar to the lens configuration of the zoom lens of Numerical Example 5, except for the following points.
(1) The biconvex positive lens 23 (positive lens Gp) in the second lens group G2 is not an aspheric lens.
(2) The negative lens 52' in the fifth lens group G5 is not a biconcave negative lens, but is a negative meniscus lens convex toward the object side.
(3) The sixth lens group G6 is composed of, in order from the object side, a negative meniscus lens 61' convex toward the object side, a biconvex positive lens 62', a positive meniscus lens 63' convex toward the object side, and a negative meniscus lens 64' convex toward the object side. The negative meniscus lens 61' is composed of a hybrid lens in which an aspheric layer made of a synthetic resin material is bonded to the object side surface of a glass lens. The negative meniscus lens 61' and the biconvex positive lens 62' are cemented together. The positive meniscus lens 63' and the negative meniscus lens 64' are cemented together.

Table 26
f=16.4~28.2~48.6, F=2.9~2.9~2.9, w=42.0~26.7~16.1, Ya=14.24
Surface number RD Nd νd Glass type (glass material)
1 2691.580 2.40 1.94595 17.98 FDS18-W(HOYA)
2 236.756 3.54 1.80400 46.53 S-LAH65VS(OHARA)
3 5547.365 0.15
4 72.410 6.02 1.80400 46.53 S-LAH65VS(OHARA)
5 230.547 D1
6* 95.297 0.05 1.51640 52.20 Optical resin
7 64.508 1.50 1.80400 46.53 S-LAH65VS(OHARA)
8 17.355 9.98
9 -50.114 1.40 1.80400 46.53 S-LAH65VS(OHARA)
10 25.471 7.21 1.69895 30.13 S-TIM35(OHARA)
11 -45.259 D2
12 -27.255 1.40 1.65160 58.55 S-LAL7(OHARA)
13 51.605 3.55 1.90366 31.31 TAFD25(HOYA)
14 -486.016 D3
15 37.238 5.71 1.59522 67.73 S-FPM2(OHARA)
16 -56.263 1.00
17 Aperture 0.20
18* 43.481 5.28 1.59201 67.02 M-PCD51(HOYA)
19 -51.709 1.40 1.94595 17.98 FDS18-W(HOYA)
20 -216.709 D4
21 -226.901 1.40 1.90525 35.04 S-LAH93(OHARA)
22 107.748 0.91
23 2425.350 1.40 1.89190 37.13 S-LAH92(OHARA)
24 26.148 3.55 1.94595 17.98 FDS18-W(HOYA)
25 89.414 D5
26* 74.669 0.08 1.51640 52.20 Optical resin
27 78.667 1.40 1.92119 23.96 FDS24(HOYA)
28 32.953 8.72 1.49700 81.61 FCD1(HOYA)
29 -28.987 0.15
30 41.11 3.40 1.49700 81.61 FCD1(HOYA)
31 535.828 1.40 1.90043 37.37 TAFD37(HOYA)
32 159.099 BF
* denotes a rotationally symmetric aspheric surface.
Table 27
Face number K A4 A6 A8 A10
6 0 1.13949E-05 -1.29877E-08 1.78064E-11 -7.48111E-15
18 0 -7.64091E-06 -5.79808E-09 -2.39943E-11 1.32093E-14
26 0 -8.66387E-06 -2.62725E-10 6.88313E-11 -1.98047E-13
Table 28
D1 D2 D3 D4 D5 BF
Short focal length end f=16.4 1.000 10.133 17.453 2.000 10.344 37.004
Intermediate focal length f=28.2 13.764 7.581 7.477 6.726 5.622 47.897
Long focal length end f=48.6 34.142 6.947 2.000 10.344 2.000 60.358
Table 29.
Lens Group Focal Length 1st Lens Group 136.1
Second lens group: -26.47
Third lens group: -58.96
Fourth lens group 27.53
Fifth lens group: -47.75
6th lens group 41.79
1st to 3rd lens groups: Short focal length end: -17.14, Long focal length end: -25.18
Subsequent lens group: Short focal length end: 35.87, Long focal length end: 33.13
Table 30
(1) 26<νdGp
Positive lens 23 (positive lens Gp): 30.13
Positive lens 32 (positive lens Gp): 31.31
(2) 1.8<Nd3p: 1.90366
(3) 1.65<NdGp
Positive lens 23 (positive lens Gp): 1.69895
Positive lens 32 (positive lens Gp): 1.90366
(4) 0.1<f2/f3<1.0: 0.45
(5) 0.1<R3gf/R2gl<10.0:0.60
(6) 1<Ndp/Ndn<1.5:1.15
(7) N3a > 1.7: 1.778
(8) 0.5<|fN/frm|<2.5:1.38
(9) 0.6<D1/D2<1.0:0.60
(10) -20<f1/f23t<-6: -9.54
(11) 0.20<D(2R-3F)T/D(2F-3R)T<0.60:0.217
(12) 2.0<|f3/ffw|<5.0:3.44
(13) 1.0<|f3/fft|<4.0:2.34
(14) 1.5<Bfw/Ya<4.0:2.60
(15) 1.5<Bfw/fw<4.0:2.25
(16) 0.3<f4/f6<0.9: 0.659
(17) 1.4<ν3n/ν3p<3.0:1.87
(18) 2.5<f1/fw<6.0:3.79
(19) 2.0<frw/Ya<3.5:2.52
(20) 0.2<M1/f1<0.6:0.28
(21) 1.00<(1-Mt^2)×MRt^2<8.00:2.810

[Numerical Example 7]
Fig. 7, Fig. 29 to Fig. 31 and Tables 31 to 35 show the zoom lens of Numerical Example 7. Fig. 7 is a lens configuration diagram. Figs. 29, 30 and 31 are aberration curve diagrams at the short focal length end, the intermediate focal length end and the long focal length end. Table 31 shows surface data, Table 32 shows aspheric surface data, Table 33 shows variable distance data, Table 34 shows zoom lens group data and Table 35 shows conditional expression data.

The zoom lens of Numerical Example 7 is composed of, in order from the object side, a front lens group GF and a rear lens group GR. The front lens group GF 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, and a third lens group G3 with negative refractive power. The rear lens group GR has positive refractive power as a whole, and is composed of, in order from the object side, a fourth lens group G4 with positive refractive power, a fifth lens group G5 (Nth lens group) with negative refractive power, a sixth lens group G6 with positive refractive power, and a seventh lens group G7 with positive refractive power.

The first lens group G1 is composed of, in order from the object side, a negative meniscus lens 11A convex toward the object side, a biconvex positive lens 12A, and a positive meniscus lens 13A convex toward the object side. The negative meniscus 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 biconvex positive lens 23A (positive lens Gp). The negative meniscus lens 21A is composed of a hybrid lens in which an aspheric layer made of a synthetic resin material is bonded to the object side surface of a glass lens. The biconcave negative lens 22A and the biconvex positive lens 23A are cemented together.

The third lens group G3 is composed of, in order from the object side, a negative meniscus lens 31A that is convex toward the image side, and a positive meniscus lens 32A (positive lens Gp) that is convex toward the image side. The negative meniscus lens 31A and the positive meniscus lens 32A are cemented together.

The fourth lens group G4 is composed of, in order from the object side, a biconvex positive lens 41A, an aperture stop SP, a biconvex positive lens 42A, and a negative meniscus lens 43A that is convex toward the image side. The biconvex positive lens 42A has an aspheric surface on the object side. The biconvex positive lens 42A and the negative meniscus lens 43A are cemented together.

The fifth lens group G5 is composed of, in order from the object side, a biconcave negative lens 51A, a negative meniscus lens 52A convex toward the object side, and a positive meniscus lens 53A convex toward the object side. The negative meniscus lens 52A and the positive meniscus lens 53A are cemented together.

The sixth lens group G6 is composed of, in order from the object side, a negative meniscus lens 61A convex toward the object side, and a biconvex positive lens 62A. The negative meniscus lens 61A is composed of a hybrid lens in which an aspheric layer made of a synthetic resin material is bonded to the object side surface of a glass lens. The negative meniscus lens 61A and the biconvex positive lens 62A are cemented together.

The seventh lens group G7 is composed of, in order from the object side, a negative meniscus lens 71A convex toward the image side and a biconvex positive lens 72A.

Table 31
f=16.5~28.3~48.5, F=2.9~2.9~2.9, w=41.9~27.0~16.4, Ya=14.24
Surface number RD Nd νd Glass type (glass material)
1 291.692 2.400 1.92286 20.88 E-FDS1-W(HOYA)
2 120.449 6.220 1.65100 56.16 S-LAL54(OHARA)
3 -548.226 0.150
4 43.818 5.020 1.71299 53.87 S-LAL8(OHARA)
5 66.449 D1
6* 336.420 0.150 1.52972 42.53 Optical resin
7 93.659 1.500 1.77250 49.60 S-LAH66(OHARA)
8 17.192 9.980
9 -49.824 1.400 1.83481 42.74 S-LAH55VS(OHARA)
10 19.857 7.210 1.78880 28.43 S-NBH58(OHARA)
11 -65.958 D2
12 -25.418 1.400 1.81600 46.62 S-LAH59(OHARA)
13 -114.054 2.550 1.95375 32.32 TAFD45(HOYA)
14 -51.081 D3
15 35.236 5.710 1.67300 38.25 S-NBH52V(OHARA)
16 -56.235 1.000
17 Aperture 0.200
18* 41.527 5.280 1.61881 63.85 M-PCD4(HOYA)
19 -32.696 1.400 1.92286 20.88 E-FDS1-W(HOYA)
20 -146.106 D4
21 -104.542 1.200 2.00100 29.13 TAFD55(HOYA)
22 47.405 1.310
23 404.479 1.200 2.00100 29.13 TAFD55(HOYA)
24 22.161 3.550 1.94595 17.98 FDS18-W(HOYA)
25 2810.371 D5
26* 64.096 0.162 1.52972 42.53 Optical resin
27 80.539 1.400 1.92119 23.96 FDS24(HOYA)
28 27.502 6.720 1.61800 63.33 S-PHM52(OHARA)
29 -31.729 D6
30 -38.041 1.400 1.85883 30.00 NBFD30(HOYA)
31 -74.136 0.200
32 494.049 4.600 1.75500 52.32 S-LAH97(OHARA)
33 -45.462 BF
* denotes a rotationally symmetric aspheric surface.
Table 32
Face number K A4 A6 A8 A10
6 0 1.67962E-05 -2.80721E-08 4.50181E-11 -3.41388E-14
18 0 -6.55265E-06 -1.22352E-08 1.11553E-11 -8.32023E-14
26 0 -7.85801E-06 1.97385E-08 -2.73144E-11 0.00000E+00
Table 33
D1 D2 D3 D4 D5 D6 BF
Short focal length end f=16.5 1.270 13.559 12.011 2.000 8.843 2.200 39.805
Intermediate focal length f=28.3 15.791 8.124 6.877 5.729 5.114 11.880 39.805
Long focal length end f=48.5 32.305 7.824 2.148 8.595 2.248 26.784 39.805
Table 34
Lens group Focal length 1st lens group 122.4
Second lens group: -21.35
Third lens group: -74.65
Fourth lens group 24.24
Fifth lens group: -32.01
6th lens group 46.93
7th lens group 123.6
1st to 3rd lens groups: Short focal length end: -16.83, Long focal length end: -26.15
Subsequent lens group: Short focal length end: 37.33, Long focal length end: 44.70
Table 35
(1) 26<νdGp
Positive lens 23A (positive lens Gp): 28.43
Positive lens 32A (positive lens Gp): 32.32
(2) 1.8<Nd3p: 1.95375
(3) 1.65<NdGp
Positive lens 23A (positive lens Gp): 1.78880
Positive lens 32A (positive lens Gp): 1.95375
(4) 0.1<f2/f3<1.0: 0.29
(5) 0.1<R3gf/R2gl<10.0:0.39
(6) 1<Ndp/Ndn<1.5:1.08
(7) N3a > 1.7: 1.885
(8) 0.5<|fN/frm|<2.5:0.80
(9) 0.6<D1/D2<1.0:0.68
(10) -20<f1/f23t<-6: -8.95
(11) 0.20<D(2R-3F)T/D(2F-3R)T<0.60:0.244
(12) 2.0<|f3/ffw|<5.0:4.44
(13) 1.0<|f3/fft|<4.0:2.85
(14) 1.5<Bfw/Ya<4.0:2.80
(15) 1.5<Bfw/fw<4.0:2.42
(16) 0.3<f4/f6<0.9:0.517
(17) 1.4<ν3n/ν3p<3.0:1.44
(18) 2.5<f1/fw<6.0:3.28
(19) 2.0<frw/Ya<3.5:2.62
(20) 0.2<M1/f1<0.6:0.33
(21) 1.00<(1-Mt^2)×MRt^2<8.00:2.192

[Numerical Example 8]
Fig. 8, Fig. 32 to Fig. 34 and Tables 36 to 40 show the zoom lens of Numerical Example 8. Fig. 8 is a lens configuration diagram. Figs. 32, 33 and 34 are aberration curve diagrams at the short focal length end, the intermediate focal length end and the long focal length end. Table 36 shows surface data, Table 37 shows aspheric surface data, Table 38 shows variable distance data, Table 39 shows zoom lens group data and Table 40 shows conditional expression data.

The zoom lens of Numerical Example 8 is composed of, in order from the object side, a front lens group GF and a rear lens group GR. The front lens group GF 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, and a third lens group G3 with negative refractive power. The rear lens group GR has positive refractive power as a whole, and is composed of, in order from the object side, a fourth lens group G4 (Nth lens group) with negative refractive power, a fifth lens group G5 with positive refractive power, and a sixth lens group G6 with positive refractive power.

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

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

The third lens group G3 is composed of, in order from the object side, a biconcave negative lens 31B and a biconvex positive lens 32B (positive lens Gp). The biconcave negative lens 31B and the biconvex positive lens 32B are cemented together.

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

The fifth lens group G5 is composed of, in order from the object side, an aperture stop SP, a biconvex positive lens 51B, a biconvex positive lens 52B, and a biconcave negative lens 53B. The biconvex positive lens 51B has an aspheric surface on the object side. The biconvex positive lens 52B and the biconcave negative lens 53B are cemented together.

The sixth lens group G6 is composed of, in order from the object side, a biconvex positive lens 61B, a biconvex positive lens 62B, a biconcave negative lens 63B, and a biconvex positive lens 64B. The biconvex positive lens 61B has an aspheric surface on the object side. The biconcave negative lens 63B and the biconvex positive lens 64B are cemented together.

Table 36
f=15.5~26.0~43.7, F=2.9~2.9~2.9, w=44.3~28.4~17.6, Ya=14.24
Surface number RD Nd νd Glass type (glass material)
1 199.785 2.170 1.89286 20.36 S-NPH4(OHARA)
2 102.000 4.500 1.51742 52.43 S-NSL36(OHARA)
3 252.412 0.150
4 73.641 5.400 1.69680 55.53 S-LAL14(OHARA)
5 462.457 D1
6* 81.668 1.600 1.95150 29.83 M-TAFD405(HOYA)
7 18.244 10.500
8 -43.000 1.200 1.72916 54.09 S-LAL19(OHARA)
9 36.802 6.500 1.90366 31.31 TAFD25(HOYA)
10 -52.610 D2
11 -40.000 0.900 1.78800 47.37 S-LAH64(OHARA)
12 36.096 4.020 1.85478 24.80 S-NBH56(OHARA)
13 -110.287 D3
14* -172.999 1.300 1.80139 45.45 M-TAF31(HOYA)
15 30.000 3.200 1.67270 32.10 S-TIM25(OHARA)
16 141.865 D4
17 Aperture 1.400
18* 45.066 5.000 1.88202 37.22 M-TAFD307(HOYA)
19 -104.442 0.200
20 40.401 6.800 1.43875 94.94 S-FPL53(OHARA)
21 -39.367 1.200 2.05090 26.94 TAFD65(HOYA)
22 102.564 D5
23* 39.054 5.000 1.59201 67.02 M-PCD51(HOYA)
24 -142.331 6.804
25 57.370 4.000 1.90043 37.37 TAFD37A(HOYA)
26 -169.112 0.200
27 -721.402 1.100 1.88300 40.80 TAFD30(HOYA)
28 19.345 6.500 1.49710 81.56 M-FCD1(HOYA)
29* -84.510 BF
* denotes a rotationally symmetric aspheric surface.
Table 37
Face number K A4 A6 A8 A10
6 0 3.64346E-06 -2.47870E-09 -4.61506E-13 -7.42412E-17
14 0 3.17941E-06 4.43317E-09 0.00000E+00 0.00000E+00
18 0 -9.18320E-07 1.42386E-09 4.71883E-13 0.00000E+00
23 0 -4.01194E-06 -2.63557E-10 0.00000E+00 0.00000E+00
29 0 8.71569E-06 1.73183E-09 1.40611E-11 0.00000E+00
Table 38
D1 D2 D3 D4 D5 BF
Short focal length end f=15.5 1.270 3.251 11.988 14.454 16.804 35.592
Intermediate focal length f=26.0 14.385 10.741 4.498 7.158 7.047 50.304
Long focal length end f=43.7 30.919 13.039 2.200 3.000 2.270 67.802
Table 39.
Lens group Focal length 1st lens group 149.1
Second lens group: -34.85
Third lens group: -103.0
Fourth lens group: -72.60
Fifth lens group: 54.75
Sixth lens group: 41.02
1st to 3rd lens groups: Short focal length end: -27.82, Long focal length end: -35.09
Subsequent lens group: Short focal length end: 34.64, Long focal length end: 38.60
Table 40
(1) 26<νdGp
Positive lens 23B (positive lens Gp): 31.31
(2) 1.8<Nd3p: 1.85478
(3) 1.65<NdGp
Positive lens 23B (positive lens Gp): 1.90366
(4) 0.1<f2/f3<1.0: 0.34
(5) 0.1<R3gf/R2gl<10.0:0.76
(6) 1<Ndp/Ndn<1.5:1.04
(7) N3a > 1.7: 1.821
(8) 0.5<|fN/frm|<2.5:1.98
(9) 0.6<D1/D2<1.0:0.62
(10) -20<f1/f23t<-6:-7.11
(11) 0.20<D(2R-3F)T/D(2F-3R)T<0.60:0.345
(12) 2.0<|f3/ffw|<5.0:3.70
(13) 1.0<|f3/fft|<4.0:2.94
(14) 1.5<Bfw/Ya<4.0:2.50
(15) 1.5<Bfw/fw<4.0:2.30
(16) 0.3<f4/f6<0.9:-
(17) 1.4<ν3n/ν3p<3.0:1.91
(18) 2.5<f1/fw<6.0:4.30
(19) 2.0<frw/Ya<3.5:2.43
(20) 0.2<M1/f1<0.6:0.24
(21) 1.00<(1-Mt^2)×MRt^2<8.00:1.073

[Numerical Example 9]
Fig. 9, Fig. 35 to Fig. 37 and Tables 41 to 45 show the zoom lens of Numerical Example 9. Fig. 9 is a lens configuration diagram. Figs. 35, 36 and 37 are aberration curve diagrams at the short focal length end, the intermediate focal length end and the long focal length end. Table 41 shows surface data, Table 42 shows aspheric surface data, Table 43 shows variable distance data, Table 44 shows zoom lens group data and Table 45 shows conditional expression data.

The zoom lens of Numerical Example 9 is composed of, from the object side, a front lens group GF and a rear lens group GR. The front lens group GF 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, and a third lens group G3 with negative refractive power. The rear lens group GR has positive refractive power as a whole, and is composed of, from the object side, a fourth lens group G4 with positive refractive power, a fifth lens group G5 with positive refractive power, and a sixth lens group G6 (Nth lens group) with negative refractive power.

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 plano-convex positive 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 11C and the plano-convex positive lens 12C are cemented together.

The second lens group G2 is composed of, in order from the object side, a negative meniscus lens 21C convex toward the object side, a biconcave negative lens 22C, and a biconvex positive lens 23C (positive lens Gp). The negative meniscus lens 21C is composed of a hybrid lens in which an aspheric layer made of a synthetic resin material is bonded to the object side surface of a glass lens. The biconcave negative lens 22C and the biconvex positive lens 23C are cemented together.

The third lens group G3 is composed of, in order from the object side, a biconcave negative lens 31C and a positive meniscus lens 32C that is convex toward the object side. The biconcave negative lens 31C and the positive meniscus lens 32C are cemented together.

The fourth lens group G4 is composed of, in order from the object side, an aperture stop SP, a positive meniscus lens 41C convex toward the object side, a biconvex positive lens 42C, and a biconcave negative lens 43C. The biconvex positive lens 42C and the biconcave negative lens 43C are cemented together.

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

The sixth lens group G6 is composed of, in order from the object side, a biconcave negative lens 61C, a positive meniscus lens 62C convex toward the object side, and a positive meniscus lens 63C convex toward the image side. The biconcave negative lens 61C and the positive meniscus lens 62C are cemented together.

Table 41
f=18.5~43.5~101.9, F=2.9~2.9~2.9, w=39.0~17.8~7.7, Ya=14.24
Surface number RD Nd νd Glass type (glass material)
1 187.168 2.170 1.85478 24.80 S-NBH56(OHARA)
2 80.603 7.600 1.59410 60.47 FCD600(HOYA)
3∞0.150
4 63.500 6.520 1.75500 52.32 S-LAH97(OHARA)
5 192.516 D1
6* 239.004 0.100 1.52972 42.53 Optical resin
7 160.004 1.500 1.88300 40.80 TAFD30(HOYA)
8 22.078 8.359
9 -55.226 1.200 1.83481 42.74 S-LAH55VS(OHARA)
10 33.000 8.670 1.90366 31.31 TAFD25(HOYA)
11 -55.650 D2
12 -37.260 0.900 1.72000 50.23 S-LAL10(OHARA)
13 38.462 3.882 1.85478 24.80 S-NBH56(OHARA)
14 51649.350 D3
15 Aperture 1.400
16 50.801 4.000 1.90043 37.37 TAFD37A(HOYA)
17 975.716 0.200
18 48.000 5.900 1.49700 81.55 S-FPL51(OHARA)
19 -51.398 1.200 2.00100 29.13 TAFD55(HOYA)
20 187.444 D4
21* 35.764 7.028 1.59201 67.02 M-PCD51(HOYA)
22 -70.613 0.757
23 -93.412 1.100 1.65412 39.68 S-NBH5(OHARA)
24 29.706 6.000 1.49710 81.56 M-FCD1(HOYA)
25* -83.798 0.120
26 95.634 3.800 2.00100 29.13 TAFD55(HOYA)
27 -104.300 D5
28 -102.465 1.000 1.95375 32.32 TAFD45(HOYA)
29 25.594 3.200 1.72825 28.46 S-TIH10(OHARA)
30 57.718 2.000
31 -82.802 3.000 1.72916 54.09 S-LAL19(OHARA)
32 -37.073 FB
* denotes a rotationally symmetric aspheric surface.
Table 42
Face number K A4 A6 A8 A10
6 0 4.78916E-06 -6.98122E-09 9.90946E-12 -7.96602E-15
21 0 -3.33582E-06 7.06755E-09 0.00000E+00 0.00000E+00
25 0 1.37019E-05 5.59672E-09 2.30684E-11 0.00000E+00
Table 43
D1 D2 D3 D4 D5 BF
Short focal length end f=18.5 1.270 6.060 33.889 15.290 2.904 30.120
Intermediate focal length f=43.5 23.139 8.060 12.538 6.435 2.587 47.793
Long focal length end f=102 46.858 17.379 1.027 3.167 1.282 66.140
Table 44
Lens group Focal length 1st lens group 106.2
Second lens group: -37.37
Third lens group: -63.36
Fourth lens group: 71.96
Fifth lens group 28.89
Sixth lens group: -55.85
1st to 3rd lens groups: Short focal length end: -25.99, Long focal length end: -61.90
Subsequent lens group: Short focal length end: 37.98, Long focal length end: 34.86
Table 45
(1) 26<νdGp
Positive lens 23C (positive lens Gp): 31.31
(2) 1.8<Nd3p: 1.85478
(3) 1.65<NdGp
Positive lens 23C (positive lens Gp): 1.90366
(4) 0.1<f2/f3<1.0:0.59
(5) 0.1<R3gf/R2gl<10.0:0.67
(6) 1<Ndp/Ndn<1.5:1.08
(7) N3a > 1.7: 1.787
(8) 0.5<|fN/frm|<2.5:1.60
(9) 0.6<D1/D2<1.0:0.83
(10) -20<f1/f23t<-6:-6.25
(11) 0.20<D(2R-3F)T/D(2F-3R)T<0.60:0.414
(12) 2.0<|f3/ffw|<5.0:2.43
(13) 1.0<|f3/fft|<4.0:1.02
(14) 1.5<Bfw/Ya<4.0:2.12
(15) 1.5<Bfw/fw<4.0:1.62
(16) 0.3<f4/f6<0.9:-
(17) 1.4<ν3n/ν3p<3.0:2.03
(18) 2.5<f1/fw<6.0:2.80
(19) 2.0<frw/Ya<3.5:2.67
(20) 0.2<M1/f1<0.6:0.44
(21) 1.00<(1-Mt^2)×MRt^2<8.00:2.466

[Numerical Example 10]
Fig. 10, Fig. 38 to Fig. 40 and Tables 46 to 50 show the zoom lens of Numerical Example 10. Fig. 10 is a lens configuration diagram. Figs. 38, 39 and 40 are aberration curve diagrams at the short focal length end, the intermediate focal length end and the long focal length end. Table 46 shows surface data, Table 47 shows aspheric surface data, Table 48 shows variable distance data, Table 49 shows zoom lens group data and Table 50 shows conditional expression data.

The zoom lens of Numerical Example 10 is composed of, in order from the object side, a front lens group GF and a rear lens group GR. The front lens group GF 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, and a third lens group G3 with negative refractive power. The rear lens group GR has positive refractive power as a whole, and is composed of, in order from the object side, a fourth lens group G4 with positive refractive power, and a fifth lens group G5 with positive refractive power. That is, in the zoom lens of Numerical Example 10, there is no "Nth lens group with negative refractive power" in the rear lens group GR.

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 positive meniscus lens 12D that is convex toward the object side, and a positive meniscus lens 13D that is convex toward the object side. The negative meniscus lens 11D and the positive meniscus 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, and a biconvex positive lens 23D. The negative meniscus lens 21D is composed of a hybrid lens in which an aspheric layer made of a synthetic resin material is bonded to the object side surface of a glass lens. The biconcave negative lens 22D and the biconvex positive lens 23D are cemented together.

The third lens group G3 is composed of, in order from the object side, a biconcave negative lens 31D and a biconvex positive lens 32D (positive lens Gp). The biconcave negative lens 31D and the biconvex positive lens 32D are cemented together.

The fourth lens group G4 is composed of, in order from the object side, an aperture stop SP, a biconvex positive lens 41D, a biconvex positive lens 42D, and a biconcave negative lens 43D. The biconvex positive lens 42D and the biconcave negative lens 43D 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 object 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 biconvex positive lens 54D has an aspheric surface on the image side. The biconcave negative lens 53D and the biconvex positive lens 54D are cemented together.

Table 46
f=16.45~28.25~48.52, F=2.9~2.9~2.9, w=42.0~26.3~16.0, Ya=14.24
Surface number RD Nd νd Glass type (glass material)
1 300.000 2.170 1.89286 20.36 S-NPH4(OHARA)
2 105.831 5.600 1.71299 53.87 S-LAL8(OHARA)
3 748.550 0.150
4 72.109 4.900 1.71700 47.93 S-LAM3(OHARA)
5 266.864 D1
6* 78.790 0.100 1.52972 42.53 Optical resin
7 60.000 1.500 1.88300 40.80 TAFD30(HOYA)
8 17.488 8.359
9 -45.000 1.200 1.80400 46.53 S-LAH65VS(OHARA)
10 46.803 6.987 1.85478 24.80 S-NBH56(OHARA)
11 -49.429 D2
12 -33.265 0.900 1.80400 46.53 S-LAH65VS(OHARA)
13 30.233 2.934 1.90366 31.31 TAFD25(HOYA)
14 -260.986 D3
15 Aperture 1.400
16 61.905 4.000 1.72000 46.02 S-LAM61(OHARA)
17 -168.572 0.200
18 32.382 5.900 1.49700 81.55 S-FPL51(OHARA)
19 -67.943 1.200 2.00100 29.13 TAFD55(HOYA)
20 122.065 D4
21* 51.218 3.000 1.69350 53.19 L-LAL13(OHARA)
22 110.800 9.285
23 46.472 4.000 1.85896 22.73 S-NPH5(OHARA)
24 -243.446 0.200
25 -7538.335 1.100 1.85478 24.80 S-NBH56(OHARA)
26 23.861 6.000 1.49710 81.56 M-FCD1(HOYA)
27* -57.300 FB
* denotes a rotationally symmetric aspheric surface.
Table 47
Face number K A4 A6 A8 A10
6 0 7.91690E-06 -8.06890E-09 7.35877E-12 -5.59588E-15
21 0 -4.18450E-06 3.53827E-09 0.00000E+00 0.00000E+00
27 0 9.39673E-06 3.24717E-09 1.77693E-11 0.00000E+00
Table 48
D1 D2 D3 D4 BF
Short focal length end f=16.45 1.270 6.004 26.148 13.059 35.953
Intermediate focal length f=28.252 16.323 8.900 11.033 7.098 49.900
Long focal length end f=48.520 31.792 10.354 2.505 4.187 66.845
Table 49.
Lens group Focal length 1st lens group 131.3
Second lens group: -31.20
Third lens group: -58.08
Fourth lens group: 57.04
Fifth lens group: 46.85
1st to 3rd lens groups: Short focal length end: -20.29, Long focal length end: -27.72
Subsequent lens group: Short focal length end: 36.81, Long focal length end: 32.80
Table 50
(1) 26<νdGp
Positive lens 32D (positive lens Gp): 31.31
(2) 1.8<Nd3p: 1.90366
(3) 1.65<NdGp
Positive lens 32D (positive lens Gp): 1.90366
(4) 0.1<f2/f3<1.0:0.54
(5) 0.1<R3gf/R2gl<10.0:0.67
(6) 1<Ndp/Ndn<1.5:1.06
(7) N3a > 1.7: 1.854
(8) 0.5<|fN/frm|<2.5:-
(9) 0.6<D1/D2<1.0:0.71
(10) -20<f1/f23t<-6: -8.47
(11) 0.20<D(2R-3F)T/D(2F-3R)T<0.60:0.32
(12) 2.0<|f3/ffw|<5.0:2.86
(13) 1.0<|f3/fft|<4.0:2.09
(14) 1.5<Bfw/Ya<4.0:2.52
(15) 1.5<Bfw/fw<4.0:2.18
(16) 0.3<f4/f6<0.9:-
(17) 1.4<ν3n/ν3p<3.0:1.49
(18) 2.5<f1/fw<6.0:7.97
(19) 2.0<frw/Ya<3.5:2.58
(20) 0.2<M1/f1<0.6:0.25
(21) 1.00<(1-Mt^2)×MRt^2<8.00:2.47

With reference to Figures 41 and 42, we will explain a digital camera (imaging device) 100 equipped with the zoom lens of this embodiment.

The digital camera 100 has a camera body (housing) 101, a photographing 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 zoom switch 110.

The camera body 101 houses each component of the digital camera 100. The photographing lens 102 is, for example, a unit formed by incorporating the zoom lens of this embodiment into a lens barrel and/or an interchangeable lens. 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. The operation button 108 is a physical switch for setting the photographing mode of the digital camera 100. The memory card slot 109 is a slot for inserting a memory card (not shown) that stores images photographed by the digital camera 100. The zoom 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 zoom switch 110, the spacing between the lens groups of the zoom lens 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 zoom lens, lens barrel, interchangeable lens, and imaging device of this embodiment can achieve both small size and high performance and a large aperture. In addition, it is possible to achieve a compact and quiet autofocus. For example, while being small and high performance, it is possible to have a large aperture with an F-number of less than 3 and cover a zoom range equivalent to 24 to 70 mm or 28 to 150 mm in 35 mm film conversion. In addition, it is possible to adopt a compact focus group configuration that is suitable for a compact and quiet autofocus.

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 zoom lens of this embodiment can 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).

GF Front lens group GR Rear lens group G1 First lens group G2 Second lens group 23 23A 23B 23C Positive lens (Gp)
G3 3rd lens group (focus lens group)
32 32A 32D Positive lens (Gp)
G4: 4th lens group (Nth lens group)
G5 Fifth lens group (Nth lens group)
G6 6th lens group (Nth lens group)
G7 Seventh lens group 100 Digital camera (imaging device)
102 Photographic lenses (lens barrels, interchangeable lenses)

Claims (16)

The optical system is composed of, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a negative refractive power, and a subsequent lens group having a positive refractive power.
When changing magnification from the short focal length end to the long focal length end, the spacing between adjacent lens groups changes.
the third lens group constitutes a focusing lens group that moves during focusing,
the third lens group is made up of one negative lens and one positive lens,
At least one of the second lens group and the third lens group has at least one positive lens Gp,
the rear lens group includes an Nth lens group having a negative refractive power, the distance between which changes between adjacent lens groups when zooming from the short focal length end to the long focal length end;
the surface of the second lens group closest to the image side is a convex surface facing the image side,
The following conditional expressions (1), (4) , and (8) are satisfied:
A zoom lens characterized by:
(1) 26<νdGp
(4) 0.1<f2/f3<1.0
(8) 0.5<|fN/frm|<2.5
however,
νdGp: Abbe number of the at least one positive lens Gp,
νdGp=(NdGp-1)/(NFGp-NCGp)
NdGp: the refractive index of the at least one positive lens Gp with respect to the d line,
NFGp: the refractive index of the at least one positive lens Gp with respect to the F line,
NCGp: the refractive index of the at least one positive lens Gp with respect to the C-line,
f2: the focal length of the second lens group,
f3: the focal length of the third lens group ,
fN: focal length of the Nth lens group,
frm: composite focal length of the subsequent lens group at intermediate focal length fm,
Intermediate focal length fm=(fw・ft) ^1/2
fw: focal length of the entire system when focused at infinity at the short focal length end,
ft: focal length of the entire system when focused at infinity at the long focal length end. the third lens group includes at least one positive lens,
The following condition (2) is satisfied:
2. The zoom lens according to claim 1.
(2) 1.8<Nd3p
however,
Nd3p: the refractive index for the d-line of the at least one positive lens in the third lens group. The following condition (3) is satisfied:
3. The zoom lens according to claim 1 or 2.
(3) 1.65<NdGp
however,
NdGp: the refractive index for the d-line of the at least one positive lens Gp. the surface of the third lens group closest to the object side is concave with respect to the object side;
4. The zoom lens according to claim 1, wherein the first and second lenses are arranged in a first and second directions. the surface of the third lens group closest to the object side is concave with respect to the object side;
The following condition (5) is satisfied:
5. The zoom lens according to claim 1, wherein the first and second lenses are arranged in a first direction and a second direction.
(5) 0.1<R3gf/R2gl<10.0
however,
R2gl: the radius of curvature of the surface of the second lens group closest to the image side,
R3gf: the radius of curvature of the surface of the third lens group closest to the object side. the third lens group includes a negative lens and a positive lens;
6. The zoom lens according to claim 1, wherein the first and second lenses are arranged in a first and second directions. the third lens group is made up of one negative lens and one positive lens, positioned in that order from the object side;
7. The zoom lens according to claim 1, wherein the first and second lenses are arranged in a first and second directions. the third lens group is made up of one negative lens and one positive lens, which are arranged in that order from the object side, and each of the negative lens and the positive lens is cemented together;
8. The zoom lens according to claim 1, wherein the first and second lenses are arranged in a first direction and a second direction. the third lens group is made up of one negative lens and one positive lens, which are arranged in that order from the object side, and each of the negative lens and the positive lens is cemented together;
The following condition (6) is satisfied:
9. The zoom lens according to claim 1, wherein the first and second lenses are arranged in a first and second directions.
(6) 1<Ndp/Ndn<1.5
however,
Ndp: the refractive index of the positive lens in the third lens group with respect to the d line,
Ndn: the refractive index of the negative lens in the third lens group with respect to the d line. The following condition (7) is satisfied:
10. The zoom lens according to claim 1, wherein the first and second lenses are arranged in a first direction and a second direction.
(7) N3a>1.7
however,
N3a: the average value of the refractive index for the d line of all the lenses in the third lens group. The first lens group is made up of three lenses: one negative lens and two positive lenses.
11. The zoom lens according to claim 1. The following condition (9) is satisfied:
12. The zoom lens according to claim 1, wherein the first and second lenses are arranged in a first direction and a second direction.
(9) 0.6<D1/D2<1.0
however,
D1: the thickness of the first lens group on the optical axis,
D2: The thickness of the second lens group on the optical axis. The following condition (10) is satisfied:
13. The zoom lens according to claim 1, wherein the first and second lenses are arranged in a first direction and a second direction.
(10)-20<f1/f23t<-6
however,
f1: the focal length of the first lens group,
f23t: a composite focal length of the second lens group and the third lens group when focusing on infinity at the long focal length extremity. The following condition (11) is satisfied:
14. The zoom lens according to claim 1,
(11) 0.20<D(2R-3F)T/D(2F-3R)T<0.60
however,
D(2R-3F)T: the distance on the optical axis from the surface of the second lens group closest to the image side to the surface of the third lens group closest to the object side when focusing on infinity at the long focal length end ,
D(2F-3R)T: the distance on the optical axis from the surface of the second lens group closest to the object to the surface of the third lens group closest to the image when focusing on infinity at the long focal length extremity. 15. A lens barrel and an interchangeable lens comprising the zoom lens according to claim 1. An imaging device comprising the zoom lens according to any one of claims 1 to 14 .

Images