JP3357930B2 - Zoom lens - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom lens, and more particularly to a zoom lens suitable for a lens shutter type camera or the like.

[0002]

2. Description of the Related Art As a zoom lens suitable for a lens shutter type camera or the like and having no limitation on back focus, a so-called multi-group composed of three or more movable lens groups in accordance with recent advances in lens barrel technology. Various zoom lenses have been proposed in which high zoom ratio and high performance are achieved by using a zoom lens. In recent years, along with miniaturization of a camera body, various zoom types have been proposed in which a lens system is miniaturized. Specifically, various proposals have been made regarding zoom lenses such as a positive / negative positive / negative three-unit zoom lens and a positive / negative positive / negative four-unit zoom lens.

In general, in a multi-unit zoom lens, since the trajectory of each lens unit at the time of zooming has more freedom in selection,
The degree of freedom in aberration correction increases. Further, since the number of lens groups responsible for zooming increases, the burden of zooming on each lens group can be reduced, and high zooming and high performance can be achieved.
Further, with the recent progress of lens barrel technology and the like, problems such as a complicated lens barrel structure due to an increase in movable parts have been overcome to some extent.

Conventionally, in a zoom lens having no limitation on the back focus, a negative lens group is arranged closest to the image side of the lens system, and a positive lens group is arranged closest to the object side. By increasing the change in the overall length of the lens and the change in the back focus during magnification, the zooming is effectively performed, and the size of the lens system is reduced. Positive / negative 3
The group zoom lens includes, in order from the object side, a first lens group having a positive refractive power, a second lens group having a positive refractive power, and a third lens group having a negative refractive power.
When zooming from the wide-angle end to the telephoto end, the air gap between the first lens group and the second lens group increases, and the air gap between the second lens group and the third lens group decreases. Each lens group moves toward the object side (for example, Japanese Patent Laid-Open No. 2-256015).

On the other hand, the positive / negative / negative four-group zoom lens includes, 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 positive refractive power, and a negative refractive power. And a fourth lens unit for power, and at the time of zooming from the wide-angle end to the telephoto end, the air gap between the first lens unit and the second lens unit increases, and the second lens unit and the third lens unit The air gap between the groups is reduced, and the air gap between the third lens group and the fourth lens group is reduced (for example, Japanese Patent Application Laid-Open No. 60-57814).

In a lens shutter type camera provided with a zoom lens, the lens system is housed (collapsed) in the camera body in a state where the air gap between adjacent lens groups is minimized during zooming. Therefore, in order to reduce the thickness of the camera body, it is necessary to reduce the thickness of the lens when retracted (thickness of the retracted lens). In order to reduce the thickness of the collapsible lens, it is effective to directly reduce the thickness of each lens unit.

[0007]

However, in a positive / negative three-group zoom lens as disclosed in Japanese Patent Application Laid-Open No. 2-256015, the third lens group bears the zooming of the entire lens system. The ratio is large. For this reason, when an attempt is made to increase the zoom ratio, there is an inconvenience that the fluctuation of off-axis aberration generated in the third lens unit during zooming increases.

In a positive / negative / positive / negative four-unit zoom lens disclosed in Japanese Patent Application Laid-Open No. 60-57814, the combined refractive power of the first lens unit and the second lens unit at the wide angle end is close to zero. Therefore, when trying to widen the angle,
A sufficient back focus cannot be obtained, and the off-axis light beam passing through the fourth lens group is separated from the optical axis, so that there is a problem that the effective diameter of the rear lens becomes large. further,
The number of movable lens groups constituting the lens system is increased as compared with the positive / negative three-group zoom lens, which is advantageous for high zoom ratio. However, the height of the off-axis light beam passing through the second lens unit changes greatly during zooming. Instead, the angle of incidence changes greatly. For this reason, if the zoom ratio exceeds 2.5, the fluctuation of off-axis aberration generated in the second lens group increases, and there is a disadvantage that the performance cannot be improved.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has as its object to provide a high-magnification zoom lens having excellent imaging performance while achieving a simple configuration and miniaturization.

[0010]

According to the present invention, a first lens group G1 having a positive refractive power and a second lens group having a negative refractive power are arranged in order from the object side. G2 and a third lens group G3 having a positive refractive power
A fourth lens group G4 having a positive refractive power, and a fifth lens group G5 having a negative refractive power. The first lens group G1 and the fifth lens group G5 are used for zooming from the wide-angle end to the telephoto end. 2
The air gap between the lens group G2 and the second lens group G2 increases, the air gap between the third lens group G3 and the third lens group G3 decreases, and the air gap between the third lens group G3 and the fourth lens group G4 increases. In a zoom lens in which at least the first lens group G1 and the fifth lens group G5 move to the object side so as to increase and reduce the air gap between the fourth lens group G4 and the fifth lens group G5, The third lens group includes:
It consists of one positive lens, the focal length of the first lens group G1 and f1, the focal length of the third lens group G3 f
3, the focal length of the entire lens system at the wide-angle end is fw, and the back focus at the wide-angle end is Bfw. 0.05 <(f1-f3) / (f1 + f3) <0.6 0.18 <Bfw / Provided is a zoom lens characterized by satisfying a condition of fw <0.35.

According to another aspect of the present invention, the object side
The first lens group having a positive refractive power and the negative lens
A second lens group having a bending power and a third lens group having a positive refractive power
A lens group, a fourth lens group having a positive refractive power,
A fifth lens group having a refractive power, and telephoto from the wide-angle end.
Upon zooming to the end, the first lens group and the second lens
The air gap between the second lens group and the second lens group increases.
The air gap between the third lens group and the third lens group is reduced.
The air gap with the fourth lens group is increased, and
The air gap between the lens group and the fifth lens group is reduced.
At least the first lens group and the fifth lens group
In the zoom lens group moves to the object side, the second
The lens group is concave at least on the object side in order from the object side.
The negative lens component with the concave surface facing the object side
A lens component, and the focal length of the first lens group is f
1, the focal length of the third lens group is f3,
The focal length of the entire lens system at the end is fw, and at the wide-angle end
When the back focus is Bfw , a zoom lens characterized by satisfying the following condition : 0.05 <(f1-f3) / (f1 + f3) <0.6 0.18 <Bfw / fw <0.35 Offer
I do.

[0012]

In the zoom lens according to the present invention, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, a third lens group G3 having a positive refractive power, and a positive refractive power. The fourth lens group G4 having a power and the fifth lens group G5 having a negative refractive power
When zooming from the wide-angle end to the telephoto end,
The distance between the first lens group G1 and the second lens group G2 increases, the distance between the second lens group G2 and the third lens group G3 decreases, and the distance between the third lens group G3 and the fourth lens group G4. Increases so that the distance between the fourth lens group G4 and the fifth lens group G5 decreases, so that at least the first lens group G1
It has a basic configuration for moving the lens group G5 to the object side.
Based on this basic configuration, it is possible to achieve a zoom lens that is simultaneously reduced in size, simplified in configuration, and increased in magnification.

The configuration of the zoom lens according to the present invention will be described. In the zoom lens according to the present invention, the negative lens group is arranged closest to the image, similarly to the conventional zoom lens having no limitation on the back focus. Further, in order to increase the angle of view, the back focus at the wide-angle end is shortened to some extent, and the height of the off-axis light beam passing through the fifth lens group G5 is separated from the optical axis, thereby suppressing the fluctuation of coma aberration due to the angle of view. ing. Then, by increasing the change of the back focus at the time of zooming, and changing the height of the off-axis light beam passing through the fifth lens group G5 with the zooming,
The fluctuation of coma due to zooming is suppressed. Further, by shortening the overall length of the lens at the wide-angle end compared to the telephoto end, the change in the overall length of the lens (the distance from the lens surface closest to the object side to the image plane) during zooming is increased, and the first lens at the wide-angle end is reduced. By making the height of the off-axis light beam passing through the group G1 closer to the optical axis, the effective diameter of the front lens is reduced.

In the zoom lens system according to the present invention, in order to achieve both a simple configuration and a high zoom ratio, the ratio of the zooming effect of the fifth lens group G5 disposed closest to the image plane is reduced. In addition, the first to fourth lens groups G1 to G4 have a variable power function. In particular, at the time of zooming from the wide-angle end to the telephoto end, the second lens group G2 performs a zooming action by increasing the change in the magnification used by the second lens group G2.

At the wide-angle end, the first lens group G1 and the second lens group G2 are brought as close as possible so that the combined refractive power of the first lens group G1 and the second lens group G2 becomes a strong negative refractive power. By arranging the first lens group G1 and the second lens group G2 at positions away from the image plane, a sufficient back focus is ensured. A third lens group G3 having a positive refractive power and a fourth lens group G having a positive refractive power
By making the distance closer to 4, a strong positive refractive power is obtained as a combined refractive power. Conversely, at the telephoto end, the first lens group G1 having a positive refractive power is moved to the object side to increase the distance between the first lens group G1 and the second lens group G2, thereby enhancing the convergence function and increasing the lens power. The overall length has been reduced. Further, by moving the third lens group G3 having a positive refracting power to the object side and narrowing the distance between the second lens group G2 and the third lens group G3, the overall length of the lens is further reduced.

In the present invention, the combined refractive power of the first lens group G1 and the second lens group G2 is always negative during zooming,
During zooming from the wide-angle end to the telephoto end, the air gap between the first lens group G1 and the second lens group G2 increases. As described above, since the second lens group G2 is used for multiplication, the combined refractive power of the first lens group G1 and the second lens group G2 is:
The value at the telephoto end is smaller than that at the wide-angle end. Further, the use magnification β2w of the second lens group G2 at the wide angle end is −1 <
By setting β2w <0, a sufficient back focus is obtained at the wide-angle end, and the height of the off-axis light beam passing through the first lens group G1 is made closer to the optical axis, which leads to a reduction in the effective diameter of the front lens. .

Hereinafter, the conditional expressions of the present invention will be described. The zoom lens of the present invention satisfies the following conditional expressions (1) and (2). 0.05 <(f1-f3) / (f1 + f3) <0.6 (1) 0.18 <Bfw / fw <0.35 (2) where, f1: focal length of the first lens group G1 f3: second Focal length fw of the three lens groups G3: focal length of the entire lens system at the wide-angle end Bfw: back focus at the wide-angle end

Conditional expression (1) satisfies the first lens group G1 and the third lens group G1.
This defines the ratio of the focal length to the lens group G3, and is a condition for achieving a balance between reducing the overall length of the lens at the telephoto end and reducing the effective diameter of the front lens. If the upper limit of conditional expression (1) is exceeded, the focal length of the first lens group G1 becomes too large with respect to the focal length of the third lens group G3,
The convergence effect of the first lens group G1 is weakened. For this reason,
It becomes difficult to reduce the overall length of the lens at the telephoto end. Conversely, if the lower limit of conditional expression (1) is not reached, the focal length of the third lens group G3 becomes too large with respect to the focal length of the first lens group G1, and the first lens group G
The convergence effect of 1 is increased. For this reason, although it is advantageous to reduce the total length of the lens at the telephoto end, the height of the off-axis light beam passing through the first lens group G1 is away from the optical axis, so that the effective diameter of the front lens increases. .

Conditional expression (2) defines an appropriate range for the back focus at the wide-angle end. When the value exceeds the upper limit of conditional expression (2), a sufficient back focus can be obtained at the wide-angle end, so that the effective diameter of the rear lens can be reduced. However, at the wide-angle end, the difference between the height of the off-axis light beam passing through the fifth lens group G5 and the height of the on-axis light beam is so small that it is difficult to correct the on-axis aberration and the off-axis aberration independently. turn into. Conversely, if the lower limit of conditional expression (2) is not reached, a sufficient back focus cannot be obtained at the wide-angle end. Further, at the wide-angle end, the height of the off-axis light beam passing through the fifth lens group G5 is separated from the optical axis, so that the effective diameter of the rear lens becomes large and the positive distortion cannot be satisfactorily suppressed. Would.

In the present invention, while achieving a high zoom ratio and a simple configuration, the conditional expressions (1) and (2) are simultaneously satisfied in order to further suppress the fluctuations of the various aberrations that occur during zooming. It is desirable that the following conditional expressions (3) and (4) are further satisfied. −0.4 <(f3-f4) / (f3 + f4) <0.3 (3) 0.6 <(β5t / β5w) · (fw / ft) <0.9 (4) where, f4: fourth The focal length of the lens group G4 ft: The focal length of the entire lens system at the telephoto end β5w: The magnification of use of the fifth lens group G5 at the wide-angle end β5t: The magnification of use of the fifth lens group G5 at the telephoto end

Conditional expression (3) indicates that the third lens group G3 and the fourth
This is to balance the focal length with the lens group G4. If the upper limit of conditional expression (3) is exceeded, the focal length of the fourth lens group G4 will be positively larger than the focal length of the third lens group G3. As a result, the position of the principal point of the combination of the third lens group G3 and the fourth lens group G4 at the telephoto end moves toward the object side, and the convergence action is strengthened. As a result, the overall length of the lens at the telephoto end is reduced. However, when trying to increase the zoom ratio, it becomes difficult to suppress fluctuation of off-axis aberration generated in the third lens group G3 during zooming from the wide-angle end to the telephoto end.

Conversely, if the lower limit of conditional expression (3) is not reached, the focal length of the third lens group G3 will be positively larger than the focal length of the fourth lens group G4. As a result, the position of the principal point of the combination of the third lens group G3 and the fourth lens group G4 at the telephoto end moves toward the image plane, so that it becomes impossible to reduce the overall length of the lens at the telephoto end. Also,
Negative spherical aberration that occurs alone in the fourth lens group G4 cannot be corrected, and a simple configuration cannot be achieved. To obtain better imaging performance, the upper limit of conditional expression (3) is set to 0.2, and the lower limit is set to-.
It is preferably 0.3.

Conditional expression (4) defines an appropriate range for the ratio of the zooming performed by the fifth lens group G5 to the zooming of the entire lens system. If the upper limit of conditional expression (4) is exceeded, the ratio of zooming carried by the fifth lens group G5 becomes too large, and the fluctuation of off-axis aberration generated in the fifth lens group G5 during zooming is satisfactorily corrected. You will not be able to do it.

On the other hand, if the lower limit of conditional expression (4) is not reached, the ratio of the variable power carried by the first lens group G1 to the fourth lens group G4 becomes large. In addition, the fluctuation of off-axis aberration generated in the third lens group G3 increases. To suppress the fluctuation of this off-axis aberration,
It is necessary to increase the number of lenses that make up each lens group,
This is contrary to the simple configuration, which is one of the objects of the present invention.
In order to obtain better imaging performance, conditional expression (4) must be satisfied.
Is preferably 0.85, and the lower limit is preferably 0.65.

In order to further enhance the performance in the present invention, the first lens unit G1 is configured so that the focal length f1 is larger than the focal length fw of the entire lens system at the wide-angle end, and the following conditional expression: It is desirable to satisfy (5). 0.1 <(ft−f1) / (f1−fw) <1.2 (5)

Conditional expression (5) defines an appropriate focal length of the first lens group G1 with respect to the focal length at the wide-angle end and the focal length at the telephoto end. The purpose is to achieve a balance with miniaturization of the lens diameter. When the value exceeds the conditional value of the conditional expression (5), the refractive power distribution at the telephoto end becomes a telephoto type, which is advantageous for shortening the overall length of the lens. However, when the height of the off-axis light beam passing through the first lens group G1 is away from the optical axis and an attempt is made to secure a constant peripheral light amount, the lens diameter of the first lens group G1 becomes large, and positive distortion occurs. Correct correction cannot be performed.

Conversely, if the lower limit of conditional expression (5) is not reached, a sufficient back focus is obtained at the wide-angle end.
The height of the off-axis light beam passing through the fifth lens group G5 approaches the optical axis, and the effective diameter of the rear lens can be reduced. However, the overall length of the lens at the telephoto end increases, which is not preferable. In order to obtain better imaging performance, it is preferable to set the upper limit of conditional expression (5) to 1.0 and the lower limit to 0.15.

In order to further reduce the size and increase the zoom ratio in the present invention, the zooming from the wide-angle end to the telephoto end is performed after satisfying some or all of the conditional expressions (1) to (5). At this time, it is desirable to move all the lens groups to the object side. In the present invention, in order to simplify the lens barrel structure, the first lens group G1 and the fifth lens group G5 are used for zooming.
Can be moved integrally, or the second lens group G2 and the fourth lens group G4 can be moved integrally. Further, the first lens group G1 and the fifth lens group can be moved integrally, and the second lens group G2 and the fourth lens group G4 can be simultaneously moved together.

The first lens group G1 and the third lens group G
3, the third lens group 3 and the fifth lens group 5, the second lens group 2 and the fifth lens group 5, or the first lens group 1, the third lens group 3, and the fifth lens group 5. And can be moved integrally. During zooming, the second lens group G2, the third lens group G3, or the fourth lens group G3.
The lens group G4 is fixed, or the second lens group G
By fixing the second lens unit G4 and the fourth lens group G4, it is possible to simplify the lens barrel structure.

Further, according to the present invention, upon focusing from a long-distance object to a short-distance object,
Using one lens group of the second lens group G2 to the fifth lens group G5, it is possible to suppress fluctuations of various aberrations that occur at the time of close-distance focusing and obtain good imaging performance. In addition, by moving a plurality of lens groups independently or integrally to perform short-distance focusing, a single lens group is moved to perform short-distance focusing. It is also possible to better correct fluctuations in various aberrations.

According to the present invention, the second lens group G2
Is divided into a plurality of lens groups, and when zooming from the wide-angle end to the telephoto end, each of the split lens groups is moved individually, so that fluctuations in various aberrations that occur during zooming can be suppressed well and high zooming can be achieved. It is also possible to connect to. further,
According to the present invention, in order to simplify the configuration of the lens system,
It is preferable that the third lens group G3 includes one positive lens component. Further, when performing so-called short-distance focusing from a long-distance object to a short-distance object, by moving at least the third lens group G3, the weight of the focusing group can be reduced. According to the present invention,
In order to obtain a sufficient back focus at the wide-angle end and satisfactorily correct positive distortion, the second lens group G2
It is preferable that the lens includes at least a cemented negative lens component having a concave surface facing the object side and a negative lens component having a concave surface facing the object side in order from the object side.

[0032]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a diagram showing the distribution of refractive power of a zoom lens according to each embodiment of the present invention and the movement of each lens group during zooming from the wide-angle end to the telephoto end. As shown in FIG. 1, the zoom lens according to each embodiment of the present invention includes, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, The zoom lens includes a third lens group G3 having a positive refractive power, a fourth lens group G4 having a positive refractive power, and a fifth lens group G5 having a negative refractive power, and zooming from the wide-angle end to the telephoto end. At this time, the air gap between the first lens group G1 and the second lens group G2 increases, the air gap between the second lens group G2 and the third lens group G3 decreases, and the third lens group G
Each lens group moves toward the object side such that the air gap between the third lens group G4 and the fourth lens group G4 increases and the air gap between the fourth lens group G4 and the fifth lens group G5 decreases.

[Embodiment 1] FIG. 2 is a diagram showing a lens configuration of a zoom lens according to a first embodiment of the present invention. The zoom lens in FIG. 2 includes a first lens group G1 including a cemented positive lens L1 of a biconvex lens and a negative meniscus lens having a concave surface facing the object side, a biconcave lens L21, and a positive meniscus lens L22 having a convex surface facing the object side. A second lens group G2 including a negative meniscus lens L23 having a concave surface facing the object side, a third lens group G3 including a biconvex lens L3,
A fourth lens group G4 comprising a cemented positive lens L4 of a biconvex lens and a negative meniscus lens having a concave surface facing the object side; a positive meniscus lens L51 having a concave surface facing the object side; a negative meniscus lens having a concave surface facing the object side L52 and a fifth lens group G5 including a negative meniscus lens 53 having a concave surface facing the object side.

The aperture stop S is arranged between the third lens unit G3 and the fourth lens unit G4, and moves together with the fourth lens unit G4 when zooming from the wide-angle end to the telephoto end. FIG. 2 shows the positional relationship between the lens groups at the wide-angle end. When the magnification is changed to the telephoto end, the lens unit moves on the optical axis along a zoom trajectory indicated by an arrow in FIG. However, at the time of zooming from the wide-angle end to the telephoto end, the second lens group G2 and the fourth lens group G4 move integrally. Table 1 below summarizes data values of the first embodiment of the present invention. In Table (1),
f is the focal length, FNO is the F number, 2ω is the angle of view,
Bf represents the back focus. Further, the surface number indicates the order of the lens surface from the object side along the traveling direction of the light beam, and the refractive index and Abbe number indicate the d-line (λ = 58).
7.6 nm).

The aspherical surface has a height in the direction perpendicular to the optical axis of y,
Assuming that the displacement amount in the optical axis direction at the height y is S (y), the reference radius of curvature is R, the conic coefficient is k, and the nth order aspherical coefficient is Cn, the following equation (a) is used. .

[Number 1] ^{S (y) = (y 2} / R) / ^{[1+ (1-k · y 2} / R 2) 1/2 ] ^{_{+ C 2 · y 2 + C}} 4 · y 4 + C 6 · y 6 + C 8 · y ⁸ + C ₁₀ · y the ¹⁰ + ··· (a), the paraxial curvature radius r of the aspherical surface is defined by the following formula (b). r = 1 / (2 · C ₂ + 1 / R) (b) The aspherical surface in the specification table of each embodiment is marked with an asterisk (*) to the left of the surface number.

[0036]

[Table 1] f = 38.8-74.8-110.5mm FNO = 4.0-6.2-8.1 2ω = 57.4-31.2-21.6 ° (Variable interval in scaling) f 38.8342 74.8480 110.5144 d3 2.1349 12.3653 17.5814 d9 3.5163 1.9043 1.0046 d11 2.7628 4.3748 5.2744 d15 13.3197 5.3470 1.6326 Bf 9.3860 30.8407 49.9960 (Conditional value) (1) (f1-f3) / (f1 + f3) = 0 .411 (2) Bfw / fw = 0.242 (3) (f3-f4) / (f3 + f4) =-0.057 (4) (β5t / β5w) · (fw / ft) = 0.745 (5) (Ft-f1) / (f1-fw) = 0.777

3 to 5 show various aberration diagrams of the first embodiment. 3 is an aberration diagram at the wide-angle end (shortest focal length state), FIG. 4 is an aberration diagram at an intermediate focal length state, and FIG. 5 is an aberration diagram at the telephoto end (longest focal length state). In each aberration diagram, FN represents the F number,
H indicates the height of the incident light, Y indicates the image height, and A indicates the incident angle of the principal ray. In the aberration diagram showing astigmatism, a solid line indicates a sagittal image plane S, and a broken line indicates a meridional image plane M. As is clear from the aberration diagrams, in this embodiment, various aberrations are favorably corrected in each focal length state.

[Embodiment 2] FIG. 6 is a diagram showing a lens configuration of a zoom lens according to a second embodiment of the present invention. The zoom lens of FIG. 6 includes a first lens group G1 including a cemented positive lens L1 of a biconvex lens and a negative meniscus lens having a concave surface facing the object side, a cemented negative lens L21 of a biconcave lens and a biconvex lens, and an object lens on the object side. A positive lens L composed of a second lens group G2 including a concave meniscus lens L22 having a concave surface, a third lens group G3 including a biconvex lens L3, and a biconvex lens and a negative meniscus lens having a concave surface facing the object side.
A fourth meniscus lens L51 having a concave surface facing the object side, a negative meniscus lens L52 having a concave surface facing the object side, and a negative lens 53 having a negative meniscus lens 53 facing the object side. And G5.

The aperture stop S is disposed between the third lens group G3 and the fourth lens group G4, and moves integrally with the fourth lens group G4 when zooming from the wide-angle end to the telephoto end. FIG. 6 shows the positional relationship of each lens group at the wide-angle end. When the magnification is changed to the telephoto end, the lens unit moves on the optical axis along a zoom trajectory indicated by an arrow in FIG. However, at the time of zooming from the wide-angle end to the telephoto end, the second lens group G2 and the fourth lens group G4 move integrally. Table 2 below summarizes the data values of the second embodiment of the present invention. In Table (2),
f is the focal length, FNO is the F number, 2ω is the angle of view,
Bf represents the back focus. Further, the surface number indicates the order of the lens surface from the object side along the traveling direction of the light beam, and the refractive index and Abbe number indicate the d-line (λ = 58).
7.6 nm).

[0040]

[Table 2] f = 38.8-75.3-110.6mm FNO = 4.0-6.3-8.0 2ω = 57.8-31.2-21.6 ° (Variable interval in zooming) f 38.8217 75.3325 110.5581 d3 2.0093 11.3819 17.2253 d8 3.5163 1.9748 1.0047 d10 2.7628 4.3044 5.2745 d14 13.8392 5.4268 1.6326 Bf 9.2758 31.8273 49.9987 (Aspherical data) k C ₂ C ₄ 7 planes 1.0000 0.0000 0.15320 × 10 ^-4 C ₆ C ₈ C ₁₀ 0.56450 × 10 ⁻⁷ -0.26640 × 10 ⁻⁸ 0.20890 × 10 ⁻¹⁰ (Conditional value) (1) (f1−f3) / (f1 + f3) = 0.391 (2) Bfw / fw = 0.239 (3) (f3-f4) / (f3 + f4) =-0.082 (4) (β5t / β5w) · (fw / ft) = 0.745 (5) (ft−f1) / (f1- fw) = 0.954

7 to 9 show various aberration diagrams of the second embodiment. FIG. 7 is a diagram illustrating various aberrations at the wide-angle end (shortest focal length state), FIG. 8 is a diagram illustrating various aberrations at the intermediate focal length state, and FIG. 9 is a diagram illustrating various aberrations at the telephoto end (longest focal length state). In each aberration diagram, FN represents the F number,
H indicates the height of the incident light, Y indicates the image height, and A indicates the incident angle of the principal ray. In the aberration diagram showing astigmatism, a solid line indicates a sagittal image plane S, and a broken line indicates a meridional image plane M. As is clear from the aberration diagrams, in this embodiment, various aberrations are favorably corrected in each focal length state.

[Embodiment 3] FIG. 10 is a diagram showing a lens configuration of a zoom lens according to a third embodiment of the present invention.
The zoom lens in FIG. 10 includes a first lens group G1 including a negative meniscus lens L11 having a convex surface facing the object side and a positive meniscus lens L12 having a convex surface facing the object side, a biconcave lens L21, and a convex surface facing the object side. A second lens group G2 including a positive meniscus lens L22 and a biconcave lens L23, a third lens group G3 including a biconvex lens L3,
A fourth lens group G4 comprising a cemented positive lens L4 of a biconvex lens and a negative meniscus lens having a concave surface facing the object side; a positive meniscus lens L51 having a concave surface facing the object side; a negative meniscus lens having a concave surface facing the object side L52 and a fifth lens group G5 including a negative meniscus lens 53 having a concave surface facing the object side.

The aperture stop S is arranged between the third lens unit G3 and the fourth lens unit G4, and moves together with the fourth lens unit G4 when zooming from the wide-angle end to the telephoto end. FIG. 10 shows the positional relationship between the lens units at the wide-angle end. When the magnification is changed to the telephoto end, the lens unit moves on the optical axis along a zoom trajectory indicated by an arrow in FIG. However, at the time of zooming from the wide-angle end to the telephoto end, the second lens group G2 and the fourth lens group G4 move integrally. Table 3 below summarizes data values of the third embodiment of the present invention. In Table (3), f represents the focal length, FNO represents the F number, 2ω represents the angle of view, and Bf represents the back focus. Further, the surface number indicates the order of the lens surface from the object side along the traveling direction of the light beam, and the refractive index and Abbe number indicate the d-line (λ = 58).
7.6 nm).

[0044]

[Table 3] f = 28.3-50.2-85.4mm FNO = 3.3-5.2-7.9 2ω = 75.8-45.8-27.8 ° (Variable spacing in zooming) f 28.2704 50.1532 85.3776 d4 1.8838 6.3577 8.6719 d10 3.1102 2.5346 1.2558 d12 1.2558 1.8314 3.1102 d16 6.7029 3.0019 1.2558 Bf 7.7417 22.7359 43.6537 ( Aspherical Data) k C ₂ C ₄ 11 faces 0.0000 0.0000 -0.12500 × 10 ^{- 3} C ₆ C ₈ C ₁₀ -0.51280 × 10 ^-6 0.37640 × 10 ^-8 -0.18560 × 10 ^-9 (Conditional value) (1) (f1-f3) / (f1 + f3) = 0.505 (2) Bfw / fw = 0.274 (3) (f3-f4) / (f3 + f4) = 0.034 (4) (β5t / β5w) · (fw / ft) = 0.804 (5) (ft−f1) / (f1) -Fw) = 0.412

FIGS. 11 to 13 show various aberrations of the third embodiment. FIG. 11 is a diagram showing various aberrations at the wide-angle end (shortest focal length state), FIG. 12 is a diagram showing various aberrations at the intermediate focal length state, and FIG. 13 is a diagram showing various aberrations at the telephoto end (longest focal length state). In each aberration diagram, FN represents the F number, H represents the height of the incident light, Y represents the image height, and A represents the incident angle of the principal ray. In the aberration diagram showing astigmatism, a solid line indicates a sagittal image plane S, and a broken line indicates a meridional image plane M. As is clear from the aberration diagrams, in this embodiment, various aberrations are favorably corrected in each focal length state.

[Embodiment 4] FIG. 14 is a diagram showing a lens configuration of a zoom lens according to a fourth embodiment of the present invention.
The zoom lens in FIG. 14 includes a first lens group G1 including a negative meniscus lens L11 having a convex surface facing the object side and a positive meniscus lens L12 having a convex surface facing the object side, and a biconcave lens and a positive lens having a convex surface facing the object side. The second lens group G2 composed of a negative lens L21 and a biconcave lens L22, the third lens group G3 composed of a biconvex lens L3, and the positive junction of a biconvex lens and a negative meniscus lens having a concave surface facing the object side. A fourth lens group G4 including a lens L4 and a positive meniscus lens L5 having a concave surface facing the object side;
1. A fifth lens group G5 including a negative meniscus lens L52 having a concave surface facing the object side and a negative meniscus lens 53 having a concave surface facing the object side.

The aperture stop S is arranged between the third lens unit G3 and the fourth lens unit G4, and moves together with the fourth lens unit G4 when zooming from the wide-angle end to the telephoto end. FIG. 14 shows the positional relationship between the lens groups at the wide-angle end. When the magnification is changed to the telephoto end, the lens unit moves on the optical axis along a zoom trajectory indicated by an arrow in FIG. However, at the time of zooming from the wide-angle end to the telephoto end, the second lens group G2 and the fourth lens group G4 move integrally. Table 4 below summarizes the data values of the fourth embodiment of the present invention. In Table (4), f represents the focal length, FNO represents the F number, 2ω represents the angle of view, and Bf represents the back focus. Further, the surface number indicates the order of the lens surface from the object side along the traveling direction of the light beam, and the refractive index and Abbe number indicate the d-line (λ = 58).
7.6 nm).

[0048]

[Table 4] f = 28.3-49.8-85.4mm FNO = 3.3-5.1-8.0 2ω = 56.2-46.0-27.8 ° (Variable spacing in zooming) f 28.2951 49.8197 85.4017 d4 1.8837 6.3575 8.6717 d9 3.1101 2.5346 1.2558 d11 1.2558 1.8314 3.1101 d15 6.7027 3.0018 1.2558 Bf 7.5972 22.5827 43.9649 ( Aspherical Data) k C ₂ C ₄ 10 faces 0.0000 0.0000 -0.14130 × 10 ^{- 3} C ₆ C ₈ C ₁₀ 0.43 180 × 10 ^-7 -0.34090 × 10 ^-7 0.58020 × 10 ^-9 (Conditional value) (1) (f1-f3) / (f1 + f3) = 0.553 (2) Bfw / fw = 0.268 (3) (f3-f4) / (f3 + f4) =-0.004 (4) (β5t / β5w) · (fw / ft) = 0.807 (5) (ft−f1) / (f1) -Fw) = 0.239

FIGS. 15 to 17 show various aberrations of the fourth embodiment. FIG. 15 is a diagram illustrating various aberrations at the wide-angle end (shortest focal length state), FIG. 16 is a diagram illustrating various aberrations at the intermediate focal length state, and FIG. 17 is a diagram illustrating various aberrations at the telephoto end (longest focal length state). In each aberration diagram, FN represents the F number, H represents the height of the incident light, Y represents the image height, and A represents the incident angle of the principal ray. In the aberration diagram showing astigmatism, a solid line indicates a sagittal image plane S, and a broken line indicates a meridional image plane M. As is clear from the aberration diagrams, in this embodiment, various aberrations are favorably corrected in each focal length state.

Further, in the present invention, by introducing an aspherical surface to any one of the lens surfaces, it is possible to obtain higher performance imaging performance and to simplify the configuration.
Further, by appropriately moving (eccentric) one lens group or a plurality of lens groups in a direction substantially orthogonal to the optical axis, a change in an image position caused by camera shake or the like is corrected, and a so-called image stabilizing effect is obtained. It is also possible.

[0051]

As described above, according to the present invention, a simple configuration with a small number of constituent lenses is provided, and a high zoom ratio can be achieved.
A zoom lens with excellent imaging performance can be realized.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a distribution of refractive power of a zoom lens according to each embodiment of the present invention and a state of movement of each lens unit during zooming from a wide-angle end to a telephoto end.

FIG. 2 is a diagram illustrating a lens configuration of a zoom lens according to a first example of the present invention.

FIG. 3 is a diagram illustrating various aberrations of the first embodiment at a wide-angle end.

FIG. 4 is a diagram illustrating various aberrations of the first embodiment at an intermediate focal length.

FIG. 5 is a diagram illustrating various aberrations of the first embodiment at a telephoto end.

FIG. 6 is a diagram illustrating a lens configuration of a zoom lens according to a second example of the present invention.

FIG. 7 is a diagram illustrating various aberrations of the second embodiment at a wide-angle end.

FIG. 8 is a diagram illustrating various aberrations of the second embodiment at an intermediate focal length.

FIG. 9 is a diagram illustrating various aberrations at the telephoto end according to the second exemplary embodiment.

FIG. 10 is a diagram illustrating a lens configuration of a zoom lens according to a third example of the present invention.

FIG. 11 is a diagram illustrating various aberrations of the third embodiment at a wide-angle end.

FIG. 12 is a diagram illustrating various aberrations of the third embodiment at an intermediate focal length.

FIG. 13 is a diagram illustrating various aberrations of the third embodiment at a telephoto end.

FIG. 14 is a diagram showing a lens configuration of a zoom lens according to Example 4 of the present invention.

FIG. 15 is a diagram illustrating various aberrations of the fourth embodiment at a wide-angle end.

FIG. 16 is a diagram illustrating various aberrations of the fourth embodiment at an intermediate focal length.

FIG. 17 is a diagram illustrating various aberrations of the fourth embodiment at a telephoto end.

[Explanation of symbols]

 G1 first lens group G2 second lens group G3 third lens group G4 fourth lens group G5 fifth lens group S aperture stop

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-136014 (JP, A) JP-A-4-293007 (JP, A) JP-A-3-225308 (JP, A) 225309 (JP, A) JP-A-3-225310 (JP, A) JP-A-2-168214 (JP, A) JP-A-7-151975 (JP, A) JP-A-7-49453 (JP, A) (58) Field surveyed (Int.Cl. ⁷ , DB name) G02B 9/00-17/08 G02B 21/02-21/04 G02B 25/00-25/04

Claims (9)

(57) [Claims] 1. A first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a positive refractive power, in order from the object side. And a fifth lens group having a negative refractive power. When zooming from the wide-angle end to the telephoto end, the air gap between the first lens group and the second lens group increases. The air gap between the second lens group and the third lens group decreases, the air gap between the third lens group and the fourth lens group increases, and the fourth lens group and the fifth lens group increase. In a zoom lens in which at least the first lens group and the fifth lens group move toward the object side so that an air gap between the third lens group and the fifth lens group moves toward the object side, the third lens group includes one positive lens . The focal length of one lens group is f1, and the focal length of the third lens group is f1. Where f3 is the focal length of the entire lens system at the wide-angle end, and Bfw is the back focus at the wide-angle end. 0.05 <(f1-f3) / (f1 + f3) <0.6 0.18 <Bfw A zoom lens satisfying the condition: /fw<0.35. 2. A lens having a positive refractive power in order from the object side.
A first lens group, a second lens group having a negative refractive power,
A third lens group having a positive refractive power and a third lens group having a positive refractive power
A fourth lens group and a fifth lens group having a negative refractive power
The first lens group for zooming from the wide-angle end to the telephoto end.
The air gap between the lens and the second lens group increases, and
The air gap between the lens group and the third lens group is reduced,
The air gap between the third lens unit and the fourth lens unit is increased.
And an air gap between the fourth lens group and the fifth lens group.
At least the first lens group and
The zoom lens in which the fifth lens group moves to the object side.
And the second lens group includes at least an object
The negative lens component with the concave surface facing the side and the concave surface on the object side
A negative lens component directed toward the third lens unit , wherein the focal length of the first lens unit is f1, and the third lens unit is
The focal length of the lens group is f3, and the entire lens system at the wide-angle end
Is the focal length of fw, and the back focus at the wide-angle end
When the scan and Bfw, 0.05 <(f1-f3 ) / (f1 + f3) <0.6 0.18 <Bfw / fw < zoom lens that satisfies the 0.35 condition. 3. The focal length of the third lens group is f3.
The focal length of the fourth lens group is set to f4, and at the wide-angle end
The use magnification of the fifth lens group is β5w at the telephoto end.
, The magnification of use of the fifth lens group is β5t,
Let fw be the focal length of the entire lens system at the telephoto end.
When the focal length of the whole definitive lens system and ft, -0.4 <(f3-f4 ) / (f3 + f4) <0.3 0.6 <(β5t / β5w) · (fw / ft) <0.9 3. The zoom lens according to claim 1, wherein the following condition is satisfied. 4. The focal length of said first lens group is f1.
And the focal length of the entire lens system at the wide-angle end is fw,
If the focal length of the entire lens system at the telephoto end is ft,
When the focal length f1 of the first lens group is
The lens system according to any one of claims 1 to 3, wherein the focal length is larger than the focal length fw of the entire zoom system, and a condition of 0.1 <(ft-f1) / (f1-fw) <1.2 is satisfied. The zoom lens described. 5. When zooming from the wide-angle end to the telephoto end,
All lenses of the first to fifth lens groups
5. The group moves to the object side.
The zoom lens according to any one of the above items . 6. When zooming from the wide-angle end to the telephoto end,
The second lens group and the fourth lens group move integrally.
The zoom lens according to claim 5 , wherein: 7. When zooming from the wide-angle end to the telephoto end,
The first lens group and the fifth lens group move integrally.
The zoom lens according to claim 5, wherein From 8. far objects when focused with respect to a close object, the zoom lens according to any one of claims 1 to 7, characterized in that moving at least the third lens group . 9. The second lens group includes, in order from the object side, at least a cemented negative lens component having a concave surface facing the object side;
The zoom lens according to claim 1 , further comprising a negative lens component having a concave surface facing the object side.