JPH09230242A - Zoom lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a large-diameter zoom lens realizing high-speed autofocusing and having a high variable power ratio by constituting the lens to satisfy specified conditional expressions. SOLUTION: This zoom lens is constituted of a 1st lens group G1 having negative refractive power, a 2nd lens group G2 and a 3rd lens group G3 having positive refractive power, a 4th lens group G4 having the negative refractive power, and a 5th lens group G5 having the positive refractive power in this order from an object side, and is the large-diameter zoom lens having the high variable power ratio, for instance, whose focal distance is 28.9-77.5mm and whose f-number is 2.9. In the case of variable magnification from a wide angle end to a telephoto end, the lateral magnification of the lens group G2 is always positive and is monotonously decreased. The following conditional expressions are satisfied: 0.0<ΔX4/ΔX2<0.3 (0<ΔX4), 0.3<ΔX5/ΔX2<0.75 (0<ΔX5). In the expressions, ΔX2 represents the moving amount of the lens group G2 in an optical axis direction from the wide angle end to the telephoto end, ΔX4 the moving amount of the lens group G4 in the optical axis direction from the wide angle end to the telephoto end, and ΔX5 the moving amount of the lens group G5 in the optical axis direction from the wide angle end to the telephoto end.

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 used in a single-lens reflex camera or the like.

[0002]

2. Description of the Related Art Conventionally, as a focusing method for a zoom lens,
There is a method in which the lens unit closest to the object side is extended to perform focusing. This focusing method can be realized with a very simple lens barrel structure. However, since the focal length of the lens unit closest to the object side, that is, the first lens unit, is long, the required movement amount (focus movement amount) of the lens for focusing is large, and the size and weight of the lens system are increased. It has the drawback of causing

Therefore, as a method for improving the above-mentioned drawbacks, the first lens group is divided into a plurality of lens subgroups,
A method has been proposed in which focusing is performed by moving a part of the plurality of lens subgroups. For example, JP
In Japanese Patent Application Laid-Open No. 9-15214 and Japanese Patent Application Laid-Open No. 2-244110, a first lens unit having a positive refracting power is divided into two lens units, a front lens unit having a positive refracting power and a rear lens unit having a negative refracting power, to obtain negative refraction. Focus is achieved by moving the group after the force.

Further, in JP-A-2-201310 and JP-A-4-15612, the first negative refractive power is
Focusing is performed by dividing the lens group into two lens groups, a front group having negative refractive power or positive refractive power and a rear group having negative refractive power, and moving the rear group having negative refractive power. On the other hand, in Japanese Unexamined Patent Publication No. 3-228008, focusing is performed by moving a second lens group of a lens system having a positive, negative, positive, and positive four-group configuration.

Further, in JP-A-5-173070 and JP-A-5-173071, in a zoom lens system composed of two or more groups of positive and negative or negative and positive, the second lens group is made to have a negative refractive power. A method has been proposed in which focusing is performed by dividing a group and a rear group having negative refractive power, or a front group having positive refractive power and a rear group having positive refractive power, and moving the front group.

On the other hand, a so-called anti-shake correction method has been conventionally known, which corrects a change in the image position due to camera shake or the like. For example, in JP-A-1-189621, the first
A lens group is disclosed in JP-A-1-191112 and JP-A-1191112.
In Japanese Patent Laid-Open No. 284823/1982, the second lens group is disclosed in
Japanese Patent No. 1911113 proposes a method of moving the final lens group in the direction orthogonal to the optical axis to perform image stabilization.

[0007]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
5214, JP-A-2-244110, JP-A-2-201310 and JP-A-4-15612.
In the focusing method disclosed in the publication, both the size and weight of the lens system are smaller than those of the focusing method in which the entire lens group closest to the object side is extended. However, in any case, since it is necessary to move a part of the lens subgroup of the first lens group having the largest lens diameter, it is difficult to remarkably improve the driving efficiency in autofocus (AF) or the like.

On the other hand, in the focusing method disclosed in Japanese Patent Application Laid-Open No. 3-228008, focusing is performed by moving the second lens group having a small lens diameter, so that focusing can be speeded up. However, from the viewpoint of aberration correction, it is currently difficult to apply this focusing method to a wide-angle or telephoto large-diameter zoom lens.

On the other hand, the focusing methods disclosed in JP-A-5-173070 and JP-A-5-173071 enable high-speed focusing and, as shown in the embodiments of the publication, a wide-angle lens. It can be applied to a large-aperture zoom lens of a zoom system or a telephoto system. However, if this focusing method is adopted in a zoom lens having a large zoom ratio, the change in the focus movement amount due to the zoom state becomes large. As a result, as described in the official gazette, focusing with a substantially constant amount of extension is impossible over the entire variable power area.

On the other hand, in the image stabilization system in which the first lens group is moved in the direction orthogonal to the optical axis as in Japanese Patent Laid-Open No. 1-189621, when it is applied to a large-aperture zoom lens like the present invention, it has the largest diameter. It drives the lens group on the large object side. As a result, the size of the drive mechanism for moving the lens group in the direction orthogonal to the optical axis is increased.

Further, in the case of the method of moving the lens group on the most image plane side as in JP-A-1-191113, the lens group distant from the aperture stop is driven in the direction orthogonal to the optical axis. As a result, when it is applied to a large-diameter zoom lens like the present invention, aberration variation due to eccentric drive of the lens group becomes large. Furthermore, JP-A 1-2848
In the case of the method of performing the image stabilization by moving the entire second lens group as in Japanese Patent Laid-Open No. H23-231911 and Japanese Patent Application Laid-Open No. 1-191112, when applied to a large aperture zoom lens like the present invention, the eccentricity of the lens group Aberration fluctuation due to driving becomes large.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a large-aperture zoom lens having a large zoom ratio and capable of speeding up autofocus (AF). Another object of the present invention is to provide a large-diameter zoom lens having a large zoom ratio, which has an image stabilization function.

[0013]

In order to solve the above-mentioned problems, in the present invention, a first lens group G1 having a negative refractive power and a second lens group having a positive refractive power are arranged in order from the object side. G2 and the third lens group G3 having a positive refractive power
And a fifth lens group G5 having a negative refractive power and a fifth lens group G5 having a positive refractive power, the zoom ratio is 1.5.
In the above zoom lens, the lateral magnification of the second lens group G2 is always positive and monotonically decreases during zooming from the wide-angle end to the telephoto end, and the second lens group G2 changes from the wide-angle end to the telephoto end. Of the fourth lens group G4 from the wide-angle end to the telephoto end, and ΔX4 is the movement amount of the fourth lens group G4 from the wide-angle end to the telephoto end. When the amount of movement in the axial direction is ΔX5, when zooming from the wide-angle end to the telephoto end, 0.0 <ΔX4 / ΔX2 <0.3 (0 <ΔX4) 0.3 <ΔX5 / ΔX2 <0.75 ( Provided is a zoom lens which satisfies the condition of 0 <ΔX5).

According to a preferred embodiment of the present invention, the second
The lens group G2 is moved along the optical axis to focus on a short-distance object. Further, at the time of zooming from the wide-angle end to the telephoto end, the second lens group G2 moves along a convex trajectory toward the object side, and the third lens group G3 moves along a substantially linear trajectory. Alternatively, it is preferable that the second lens group G2 moves along a substantially linear trajectory, and the third lens group G3 moves along a trajectory that is convex toward the object side. Furthermore, in the configuration of the present invention as described above, the image stabilization can be performed by moving the second lens group G2 in the direction orthogonal to the optical axis, for example. In this case, the second lens group G2 preferably has at least one cemented lens.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION As described above, according to the present invention, at the time of zooming from the wide-angle end to the telephoto end, the fourth lens group G4 and the fourth lens group G4 should satisfy the following conditional expressions (1) and (2). 5
The lens group G5 moves. 0.0 <ΔX4 / ΔX2 <0.3 (0 <ΔX4) (1) 0.3 <ΔX5 / ΔX2 <0.75 (0 <ΔX5) (2) where ΔX2 is the wide angle of the second lens group G2. Amount of movement from the end to the telephoto end in the optical axis direction ΔX4: Amount of movement of the fourth lens group G4 from the wide-angle end to the telephoto end in the optical axis direction ΔX5: An optical axis from the wide-angle end to the telephoto end of the fifth lens group G5 Amount of movement in direction

Compared to the negative-positive-negative-positive four-group configuration of the conventional example, the negative-positive-positive-negative-positive five-group configuration not only increases the degree of freedom in aberration correction, but is also defined by the conditional expression (1). In the range, the second lens group G2 and the fourth lens group G4 move in the same direction, and the moving speed of the fourth lens group G4 is slower than that of the second lens group G2. That is, during zooming, the distance between the second lens group G2 and the fourth lens group G4 becomes wider at the telephoto end than at the wide-angle end. When the distance between the second lens group G2 and the fourth lens group G4 becomes wider, the light flux converged by the second lens group G2 is narrowed down without being expanded by the third lens group G3 having a positive refractive power, and the fourth lens group It is incident on G4. Therefore, when the diaphragm is arranged near the fourth lens group G4, the diaphragm diameter becomes small, and as a result, the optical system can be downsized.

As described above, the conditional expression (1) defines the movement amount of the fourth lens group G4 with respect to the second lens group G2. If the lower limit of conditional expression (1) is exceeded, the second lens group G
This is inconvenient because the second lens unit G4 and the second lens unit G4 move in opposite directions. On the other hand, when the upper limit of conditional expression (1) is exceeded, the convergence rate of the second lens group G2 becomes small,
If the convergence rate of the lens group G2 is increased, the refracting power of the second lens group G2 becomes stronger. As a result, it becomes difficult to correct the aberration.

Conditional expression (2) defines the moving amount of the fifth lens group G5 with respect to the second lens group G2. The larger the value of the conditional expression (2), the narrower the distance between the fourth lens group G4 and the fifth lens group G5 at the telephoto end. When such an arrangement is adopted, the difference in height of the peripheral light flux in the fourth lens group G4 between the telephoto end and the wide-angle end becomes large, and correction of coma aberration at the telephoto end becomes advantageous. When the value goes below the lower limit of conditional expression (2), the distance between the fourth lens group G4 and the fifth lens group G5 is not sufficiently narrow, and it becomes difficult to correct coma. On the other hand, if the upper limit of conditional expression (2) is exceeded, the fifth
The amount of movement of the lens group G5 becomes too large, and it becomes impossible to maintain the distance between the lens group G5 and the fourth lens group G4, resulting in an increase in the total lens length.

However, in order to achieve both the degree of freedom in aberration correction and the simplification of the lens barrel structure, one of the second lens group G2 and the third lens group G3 is made to have a non-linear trajectory rather than the other. It is preferable to make the trajectories approximately linear and the other trajectories non-linear. Such an orbital shape is advantageous for aberration correction over the entire range from the wide-angle end to the telephoto end.
In particular, during zooming from the wide-angle end to the telephoto end, the second lens group G2 moves along a convex trajectory toward the object side, and the third lens group G3 moves along a substantially linear trajectory, or It is preferable that the second lens group G2 moves along a substantially linear trajectory, and the third lens group G3 moves along a trajectory that is convex toward the object side. In the case of such a form, it becomes possible to effectively correct the field curvature in the intermediate focal length state.

In order from the object side, an object side lens group A (first lens group G1) not involved in focusing, a focusing lens group F (second lens group G2) involved in focusing, and a focusing state Not image side lens group B (lens group after third lens group G3)
The configuration of the present invention is considered based on the thin paraxial optical system configured by Then, the focal length of the object-side lens unit A is f _A , the lateral magnification of the focusing lens unit F in the infinity in-focus state is β _F, and the object at the shooting distance (object-image distance) R is changed from the object at infinity. The focusing movement amount of the focusing lens unit F for focusing (the movement from the object side to the image side is positive) is ΔX
And Further, the length of the entire lens system (distance along the optical axis from the object-side principal point of the object-side lens group A to the image plane) is TL
And the distance along the optical axis from the object side principal point of the object side lens group A to the object is defined as D _o .

In this case, as disclosed in Japanese Patent Laid-Open No. 173070/1993, the relationship shown in the following expression (a) is established. (D _O −f _A ) ΔX≈ (f _A ² × β _F ² ) / (β _F ² −1) (a) Differentiating the above equation (a) by β _F gives the following equation (b). Relationship is obtained. _{ΔX / dβ F = -2β F /} {(β F 2 -1) 2 (D O -f A)} (b)

In a general zoom lens, (D _O −f _A )> 0 in the equation (b). Further, according to the present invention, the focusing lens unit F (the second lens unit G) in the infinity focusing condition is used.
The lateral magnification β _{F in} 2) is β _F > from the wide-angle end to the telephoto end.
0. Therefore, as shown in the following equation (c),
The value on the right side of expression (b) is always negative. ΔX / dβ _F <0 (c)

From equation (c), when the lateral magnification β _F of the focusing lens unit F in the infinity in-focus state monotonically decreases from the wide-angle end to the telephoto end, it is possible to focus on an object at infinity to a close-up object. It can be seen that the focusing movement amount ΔX of the focusing lens unit F of No. 1 increases monotonically from the wide-angle end to the telephoto end. In the above discussion, D _O is approximately treated as a constant.
However, in practice, since D _O will vary depending on the beta _F, when the numerical value D _O is small in some cases ΔX does not increase monotonically.

The shape of the focus cam is described in JP-A-3-23.
As disclosed in Japanese Patent No. 5908 and Japanese Unexamined Patent Publication No. 5-142475, the focusing movement amount that monotonically changes from the wide-angle end to the telephoto end (monotonically increases in each embodiment) is moved in the optical axis direction of the cam. It is determined that the focus shift due to the focus cam is reduced by superimposing the amount and the movement amount in the rotation direction. According to the present invention, with the above-described configuration, the focusing movement amount increases monotonically during zooming from the wide-angle end to the telephoto end. As a result, it is possible to configure a focus cam capable of MF (manual focus) with little focus shift, and it is possible to realize a zoom lens that achieves both high-speed AF and MF with little focus shift.

Further, in order to reduce the focusing movement amount to improve the near-distance aberration performance and reduce the size of the entire lens system, it is desirable to satisfy the following conditional expression (3). 1.0 <ΔX _T / ΔX _W <1.5 (3) where ΔX _W : the amount of movement of the second lens group G2 for focusing from an object at infinity to a close object at the wide-angle end ΔX _T : Amount of movement of the second lens group G2 for focusing from an object at infinity to an object at a close distance at the telephoto end

When the value goes below the lower limit of the conditional expression (3), the focusing movement amount at the wide-angle end becomes larger than that at the telephoto end. That is, the amount of focusing movement is reduced during zooming from the wide-angle end to the telephoto end, and the lateral magnification of the second lens group G2 monotonically decreases from the wide-angle end to the telephoto end. You will not be able to achieve it. On the other hand, if the upper limit of conditional expression (3) is exceeded, the difference in the focus movement amount between the wide-angle end and the telephoto end becomes large. This indicates that the focusing lens group has a weak refractive power, and as a result, the total lens length becomes long, which is not preferable.

When the second lens group G2 is driven in the direction orthogonal to the optical axis for image stabilization correction, the second lens group G2 is used.
Since 2 is a lens group close to the aperture stop, it is possible to suppress a variation in aberration caused by the eccentric drive of the second lens group G2. In this case, by using at least one cemented lens for the second lens group G2, the second lens group G2
It is effective because each of the two alone produces a good aberration state.

[0028]

Embodiments of the present invention will be described below with reference to the accompanying drawings. In each embodiment, the aspherical surface has a height y in the direction perpendicular to the optical axis, a displacement amount (sag amount) in the optical axis direction at the height y, S (y), a reference radius of curvature R, and a conic coefficient. Is represented by κ and the aspherical coefficient of the n-th order is represented by Cn, it is expressed by the following mathematical expression (d).

[Equation 1] S (y) = (y ² / R) / [1+ (1-κ · y ² / R ² ) ^1/2 ] + C ₂ · y ² + C ₄ · y ⁴ + C ₆ · y ⁶ + C ₈ in _{^{· y 8 + C 10 · y}} 10 + ··· (d) each of the embodiments, the aspheric are asterisked right of the surface number.

Example 1 FIG. 1 is a diagram showing a lens configuration of a zoom lens according to Example 1 of the present invention. FIG. 2 is a diagram for explaining the movement of each lens unit upon zooming from the wide-angle end to the telephoto end in the first embodiment. The zoom lens of FIG. 1 has a first negative refractive power in order from the object side.
A lens group G1, a second lens group G2 having a positive refractive power, a third lens group G3 having a positive refractive power, and a fourth lens group G having a negative refractive power.
4 and a fifth lens group G5 having a positive refractive power. The zoom lens of the first embodiment has a focal length of 28.9 to 77.5 m.
It is a large-aperture zoom lens with a large zoom ratio of F number 2.9 at m, and the closest distance is set to 0.6 m.

The first lens group G1 comprises, in order from the object side, a negative meniscus lens having a convex surface facing the object side, a biconcave lens, and a positive meniscus lens having a convex surface facing the object side. The second lens group G2 includes, in order from the object side, a negative positive meniscus lens having a convex surface facing the object side, a biconvex lens, and a negative positive meniscus lens having a concave surface facing the object side. Further, the third lens group G3 is composed of, in order from the object side, a positive meniscus lens having a convex surface facing the object side and a biconvex lens.

The fourth lens group G4 includes, in order from the object side, a cemented negative lens of a positive meniscus lens having a concave surface facing the object side and a biconcave lens, and a biconcave lens and a positive meniscus lens having a convex surface facing the object side. It consists of a cemented negative lens. Further, the fifth lens group G5 is composed of, in order from the object side, a cemented positive lens having a negative meniscus lens having a convex surface facing the object side and a biconvex lens, a biconvex lens, and a negative meniscus lens having a concave surface facing the object side.

The aperture stop S is arranged between the third lens group G3 and the fourth lens group G4. FIG. 1 shows the positional relationship of each lens group at the wide-angle end, and when the magnification is changed to the telephoto end, it moves on the optical axis along the zoom orbit shown by the arrow in FIG. That is, as shown in FIG. 2, during zooming from the wide-angle end to the telephoto end, the second lens group G2 moves along a convex trajectory toward the object side, and the third lens group G3 follows a substantially linear trajectory. To move. In addition, the second lens group G
2 is moved to the image side along the optical axis to focus on a short-distance object. Furthermore, by moving the second lens G2 in the direction orthogonal to the optical axis, the fluctuation of the image position due to camera shake or the like is corrected.

The following table (1) lists the values of specifications 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 is the back focus, β is the shooting magnification, and d0 is the distance from the object to the lens surface closest to the object along the optical axis. Further, the surface number indicates the order of the lens surface from the object side along the direction in which the light beam travels, and the refractive index and Abbe number indicate values for the d-line (λ = 587.6 nm).

[0034]

[Table 1] f = 28.9 to 77.5 FNO = 2.9 2ω = 76.0 to 30.7 (Aspherical data) κ C ₂ C ₄ 4 surface -0.0842 0.0000 7.1296 × 10 ^-8 C ₆ C ₈ C ₁₀ -3.0702 × 10 ^-10 5.0743 × 10 ^-13 -1.5016 × 10 ^-16 κ C ₂ C ₄ 17 surface -3.9460 0.0000 -3.5252 × 10 ^-6 C ₆ C ₈ C ₁₀ 9.6494 × 10 ^-9 -7.6024 × 10 ^-11 1.7602 × 10 ^-13 (Variable spacing during zooming) f / β 28.9 43.0 77.5 -0.0630 -0.0917 -0.1672 d0 ∞ ∞ ∞ 402.423 417.763 418.380 d6 53.167 25.058 2.215 57.865 29.985 8.081 d10 7.339 10.448 7.339 2.641 5.521 1.473 d14 5.227 13.372 33.887 5.227 13.372 33.887 d20 15.835 11.083 3.033 15.835 11.083 3.033 Bf 39.709 45.976 58.847 39.847 39.

As shown in the condition corresponding value column of Table (1),
From the wide-angle end to the telephoto end, the lateral magnification β _{F of} the second lens group G2, which is a focusing lens group, in the in-focus state at infinity monotonously decreases, and the focusing movement amount ΔX of the second lens group G2 monotonically increases. There is. In addition, in the column of the value corresponding to the condition of Table (1),
β _F is the lateral magnification of the second lens group G2, which is the focusing lens group, in the in-focus state at infinity, and ΔX is the focusing of the second lens group G2 for focusing from an object at infinity to an object at a close range. The amount of movement (movement to the image side is positive).

The following Table (2) shows the shape of the focusing moving cam of the first embodiment as a spline function ("Numerical Analysis and Numerical Analysis") concerning the moving amount (ANGLE) in the rotational direction and the moving amount (DIS) in the optical axis direction.
FORTRAN: Maruzen, Spline function and its application: Educational Publishing, etc.). That is, Table (2) shows the movement amount (ANGL) in the rotation direction at the spline interpolation sample point.
E) and the amount of movement in the optical axis direction (DIS) are shown. The amount of movement in the optical axis direction (DIS) is positive when moving toward the object side.

[0037]

[Table 2]

The following table (3) shows the infinity in-focus position of the in-focus moving cam of the first embodiment (position corresponding to infinity) in each focal length state, and the in-focus moving cam for each shooting distance. The amount of rotational movement (focusing amount of rotation) is shown. In Table (3), the wide-angle end (f = 28.9) to the telephoto end (f = 7)
It is standardized so that the amount of variable magnification rotation to 7.5) becomes 50. At this time, the focus rotation amount from the infinity in-focus position (shooting distance R = ∞) to the closest in-focus position (R = 0.6 m) is 5
It is 0.

[0039]

[Table 3] Focal length Infinity correspondence position Shooting distance Focusing rotation amount 28.9mm 0.000 3m 9.019 35.0mm 5.400 2m 13.664 43.0mm 13.000 1.5m 18.426 50.0mm 20.000 1.0m 28.278 60.0mm 31.350 0.7m 41.651 68.0mm 40.250 0.6m 50.000 77.5 mm 50.000

Next, it will be examined whether or not so-called MF (manual focus) is possible in the zoom lens of the first embodiment. If the amount of displacement of the image plane (image forming point) from the position of the predetermined image forming point exceeds the depth of focus of the zoom lens, manual focusing (MF) using a so-called helicoid (spiral screw) or the like is impossible. Will be. The following table (4) shows the displacement amount of the image forming point (image plane) when performing the MF operation using the focusing movement cam of the first embodiment.
It is shown corresponding to each focal length state and each shooting distance state.

[0041]

[Table 4] 0.6m 0.7m 1.0m 1.5m 2m 3m 28.9mm 0.000 0.006 0.000 0.000 -0.015 -0.018 35.0mm -0.037 -0.009 -0.009 0.012 0.013 -0.005 43.0mm -0.038 0.013 0.008 0.018 0.031 0.041 50.0mm -0.059 0.002 -0.005 -0.018 -0.016 -0.010 60.0mm -0.037 0.059 0.043 0.030 0.018 0.004 68.0mm -0.061 0.057 0.052 0.042 0.038 0.027 77.5mm 0.000 0.000 0.000 0.000 0.000 0.000

As is clear from Table (4), the amount of displacement of the image forming point in each focal length state and each photographing distance state is sufficiently small with respect to the focal depth (0.09 mm) of the lens system of the first embodiment. , It can be seen that accurate manual focus with less focus shift is possible.

3 to 8 show the d line (λ = 587.6n).
FIG. 7 is a diagram illustrating various aberrations of the first example with respect to m). Note that FIG.
Is a diagram of various aberrations at the wide-angle end when focused on infinity,
FIG. 4 is a diagram of various aberrations in the state of infinity focusing at the intermediate focal length state, and FIG. 5 is a diagram of various aberrations in the state of focusing at infinity at the telephoto end. FIG. 6 is a diagram of various aberrations at a wide-angle end in a short-distance focus state, FIG. 7 is a diagram of various aberrations at a short-distance focus state at an intermediate focal length condition, and FIG. 8 is a close-up graph at the telephoto end. FIG. 7 is a diagram of various types of aberration in a state in which a distance is in focus. FIG.
[Fig. 6A] is an aberration diagram of Example 1 at the wide-angle end (infinity in-focus state) and the telephoto end (infinity-in-focus state) before image stabilization. FIG. 10 is a diagram of various aberrations at the wide-angle end (infinity in-focus state) and the telephoto end (infinity-in-focus state) during image stabilization in the first embodiment. FIG. 10 shows various aberration amounts when the second lens group G2 is decentered on the image side by an amount corresponding to an angle of view of 0.2 °.

In each aberration diagram, FNO is the F number,
NA indicates the numerical aperture, and Y indicates the image height. In the aberration diagram showing astigmatism, the solid line S shows the sagittal image plane, and the broken line M shows the meridional image plane. Further, in the aberration diagram showing the spherical aberration, a broken line indicates a sine condition (sine condition). As is clear from the aberration diagrams of FIGS. 3 to 8, in the present embodiment,
It can be seen that various aberrations are satisfactorily corrected in each shooting distance state from the wide-angle end to the telephoto end. Further, as is clear from the aberration diagrams of FIGS. 9 and 10, in the present embodiment, the aberration variation during the image stabilization correction is smaller than that before the image stabilization correction, and good imaging performance is maintained. Therefore, it can be seen that image stabilization can be performed.

[Embodiment 2] FIG. 11 is a diagram showing a lens configuration of a zoom lens according to a second embodiment of the present invention.
FIG. 12 is a diagram for explaining the movement of each lens unit upon zooming from the wide-angle end to the telephoto end in the second embodiment. The zoom lens of FIG. 11 has, in order from the object side, a first lens group G1 having negative refractive power and a second lens group G2 having positive refractive power.
And a third lens group G3 having a positive refractive power, a fourth lens group G4 having a negative refractive power, and a fifth lens group G5 having a positive refractive power. The zoom lens of the second embodiment has a focal length of 28.9 ~.
It is a large-diameter zoom lens with a large zoom ratio of 77.5 mm and an F-number of 2.9, and the closest distance is set to 0.6 m.

The first lens group G1 comprises, in order from the object side, a negative meniscus lens having a convex surface facing the object side, a biconcave lens, and a positive meniscus lens having a convex surface facing the object side. The second lens group G2 includes, in order from the object side, a negative positive meniscus lens having a convex surface facing the object side, a biconvex lens, and a negative positive meniscus lens having a concave surface facing the object side. Further, the third lens group G3 is composed of, in order from the object side, a positive meniscus lens having a convex surface facing the object side and a biconvex lens.

The fourth lens group G4 includes, in order from the object side, a cemented negative lens composed of a positive meniscus lens having a concave surface facing the object side and a biconcave lens, and a biconcave lens and a positive meniscus lens having a convex surface facing the object side. It consists of a cemented negative lens. Further, the fifth lens group G5 is composed of, in order from the object side, a cemented positive lens having a negative meniscus lens having a convex surface facing the object side and a biconvex lens, a biconvex lens, and a negative meniscus lens having a concave surface facing the object side.

The aperture stop S is arranged between the third lens group G3 and the fourth lens group G4. FIG.
The positional relationship of each lens group at the wide-angle end is shown, and during zooming to the telephoto end, the lens units move on the optical axis along the zoom orbit shown by the arrow in FIG. That is, as shown in FIG. 12, during zooming from the wide-angle end to the telephoto end, the second lens group G2 moves along a substantially linear trajectory, and the third lens group G2
3 moves along a trajectory convex to the object side. Further, the second lens group G2 is moved to the image side along the optical axis to focus on a short-distance object. Furthermore, by moving the second lens G2 in the direction orthogonal to the optical axis, the fluctuation of the image position due to camera shake or the like is corrected.

The following table (5) lists the values of the specifications of the second embodiment of the present invention. In Table (5), f is the focal length,
FNO is the F number, 2ω is the angle of view, Bf is the back focus, β is the shooting magnification, and d0 is the distance from the object to the lens surface closest to the object along the optical axis. Further, the surface number indicates the order of the lens surface from the object side along the direction in which the light beam travels, and the refractive index and Abbe number indicate values for the d-line (λ = 587.6 nm).

[0050]

[Table 5] f = 28.9 to 77.5 FNO = 2.9 2ω = 75.6 to 30.7 (Aspherical data) κ C ₂ C ₄ 4 surface -0.0842 0.0000 4.7358 × 10 ^-8 C ₆ C ₈ C ₁₀ -4.6171 × 10 ^-10 7.2 146 × 10 ^-13 -2.0611 × 10 ^-16 κ C ₂ C ₄ 17 surface -3.9460 0.0000 -2.9044 × 10 ^-6 C ₆ C ₈ C ₁₀ 1.1660 × 10 ^-8 -8.3609 × 10 ^-11 1.9060 × 10 ^-13 (Variable spacing during zooming) f / β 28.9 43.0 77.5 -0.0637 -0.0916 -0.1672 d0 ∞ ∞ ∞ 398.916 419.501 419.419 d6 51.820 24.270 1.164 56.566 29.183 7.031 d10 12.167 9.167 7.058 7.421 4.254 1.192 d14 5.392 13.537 34.052 5.392 13.537 34.052 d20 15.160 11.010 2.760 15.160 11.010 2.760 Bf 40.245 46.214 59.246 40.245 46.214

As shown in the condition corresponding value column of Table (5),
From the wide-angle end to the telephoto end, the lateral magnification β _{F of} the second lens group G2, which is a focusing lens group, in the in-focus state at infinity monotonously decreases, and the focusing movement amount ΔX of the second lens group G2 monotonically increases. There is. In addition, in the column of the value corresponding to the condition of Table (5),
β _F is the lateral magnification of the second lens group G2, which is the focusing lens group, in the in-focus state at infinity, and ΔX is the focusing of the second lens group G2 for focusing from an object at infinity to an object at a close range. The amount of movement (movement to the image side is positive).

The following Table (6) shows the shape of the focusing moving cam of the second embodiment in terms of the spline function ("Numerical Analysis and Numerical Analysis") relating to the moving amount (ANGLE) in the rotational direction and the moving amount (DIS) in the optical axis direction.
FORTRAN: Maruzen, Spline function and its application: Educational Publishing, etc.). That is, Table (6) shows the movement amount (ANGL) in the rotation direction at the spline interpolation sample point.
E) and the amount of movement in the optical axis direction (DIS) are shown. The amount of movement in the optical axis direction (DIS) is positive when moving toward the object side.

[0053]

[Table 6]

The following table (7) shows the in-focus position of the moving cam for focusing according to the second embodiment in each focal length state (the position corresponding to infinity), and the moving cam for focusing for each photographing distance. The amount of rotational movement (focusing amount of rotation) is shown. In Table (7), from the wide-angle end (f = 28.9) to the telephoto end (f = 7
It is standardized so that the amount of variable magnification rotation to 7.5) becomes 50. At this time, the focus rotation amount from the infinity in-focus position (shooting distance R = ∞) to the closest in-focus position (R = 0.6 m) is 5
It is 0.021.

[0055]

[Table 7] Focal length Infinity correspondence position Shooting distance Focusing rotation amount 28.9mm 0.000 3m 9.109 35.0mm 4.250 2m 13.812 43.0mm 10.500 1.5m 18.608 50.0mm 16.500 1.0m 28.522 60.0mm 27.000 0.7m 42.019 68.0mm 36.500 0.6m 50.021 77.5 mm 50.000

Next, it will be examined whether or not so-called MF (manual focus) is possible in the zoom lens of the second embodiment. If the amount of displacement of the image plane (image forming point) from the position of the predetermined image forming point exceeds the depth of focus of the zoom lens, manual focusing (MF) using a so-called helicoid (spiral screw) or the like is impossible. Will be. The following table (8) shows the displacement amount of the image forming point (image plane) when performing the MF operation using the focusing movement cam of the second embodiment.
It is shown corresponding to each focal length state and each shooting distance state.

[0057]

[Table 8] 0.6m 0.7m 1.0m 1.5m 2m 3m 28.9mm 0.005 0.005 0.005 0.013 -0.002 -0.013 35.0mm -0.035 -0.026 -0.004 0.026 0.028 0.008 43.0mm -0.037 -0.034 0.001 0.023 0.046 0.055 50.0mm -0.055- 0.048 -0.042 -0.021 -0.011 -0.012 60.0mm -0.023 -0.012 -0.046 -0.046 -0.030 -0.025 68.0mm 0.021 0.035 0.006 -0.034 -0.047 -0.029 77.5mm 0.000 0.000 0.000 0.000 0.000 0.000

As is clear from Table (8), the amount of displacement of the image formation point in each focal length state and each photographing distance state is sufficiently small with respect to the focal depth (0.09 mm) of the lens system of the second embodiment. , It can be seen that accurate manual focus with less focus shift is possible.

FIGS. 13 to 18 show the d line (λ = 587.
FIG. 9 is a diagram illustrating various aberrations of the second example with respect to 6 nm). In addition,
FIG. 13 is a diagram of various aberrations at the wide-angle end in the infinity focused state, FIG. 14 is a diagram of various aberrations at the intermediate focal length state at the infinity focused state, and FIG. 15 is a graph of the various aberrations at the telephoto end. FIG. 7 is a diagram of various types of aberration in a focused state. 16 is a diagram of various aberrations in the short-distance focus state at the wide-angle end, FIG. 17 is a diagram of various aberrations in the short-distance focus state at the intermediate focal length state, and FIG. 18 is a near-distance focus state at the telephoto end. FIG. 7 is a diagram of various types of aberration in a state in which a distance is in focus. FIG. 19 is a diagram of various types of aberration at the wide-angle end (infinity in-focus state) and the telephoto end (infinity-in-focus state) before image stabilization in the second embodiment. FIG. 20 is a diagram of various types of aberration at the wide-angle end (infinity in-focus condition) and the telephoto end (infinity-in-focus condition) during image stabilization in the second embodiment. FIG.
0 represents the amount of various aberrations when the second lens group G2 is decentered on the image side by an amount corresponding to an angle of view of 0.2 °.

In each aberration diagram, FNO represents an F number,
NA indicates the numerical aperture, and Y indicates the image height. In the aberration diagram showing astigmatism, the solid line S shows the sagittal image plane, and the broken line M shows the meridional image plane. Further, in the aberration diagram showing the spherical aberration, a broken line indicates a sine condition (sine condition). FIG.
As can be seen from the aberration diagrams of FIGS. 18A to 18C, in the present embodiment, various aberrations are satisfactorily corrected in each shooting distance state from the wide-angle end to the telephoto end. Further, as is clear from the aberration diagrams of FIGS. 19 and 20, in the present embodiment, the aberration variation during the image stabilization is smaller than that before the image stabilization and the good image forming performance is maintained. Therefore, it can be seen that image stabilization can be performed.

[0061]

[Effect] As described above, according to the present invention, it is possible to perform high-efficiency autofocus and accurate manual focus with little focus shift, and have a large zoom ratio with a large zoom ratio that has an image stabilization function. A lens can be realized.

[Brief description of drawings]

FIG. 1 is a diagram showing a lens configuration of a zoom lens according to Example 1 of the present invention.

FIG. 2 is a diagram illustrating the movement of each lens unit during zooming from the wide-angle end to the telephoto end in the first embodiment.

FIG. 3 is a diagram illustrating various aberrations of the first embodiment at a wide-angle end in an infinity in-focus condition;

FIG. 4 is a diagram of various types of aberration in the in-focus state at infinity at the intermediate focal length according to the first example.

FIG. 5 is a diagram of various types of aberration in the first embodiment at a telephoto end and focused at infinity.

FIG. 6 is a diagram of various types of aberration in a short-distance focus state at the wide-angle end according to the first example.

FIG. 7 is a diagram of various types of aberration in a short-distance focus state at the intermediate focal length according to the first example.

FIG. 8 is a diagram of various types of aberration in a short-distance focus state at the telephoto end of the first example.

FIG. 9 is a diagram of various types of aberration at the wide-angle end (infinity in-focus state) and the telephoto end (infinity-in-focus state) before image stabilization in the first embodiment.

FIG. 10 is a diagram of various types of aberration at the wide-angle end (infinity in-focus condition) and the telephoto end (infinity-in-focus condition) during image stabilization in the first embodiment.

FIG. 11 is a diagram showing a lens configuration of a zoom lens according to Example 2 of the present invention.

FIG. 12 is a diagram for explaining the movement of each lens unit upon zooming from the wide-angle end to the telephoto end in the second embodiment.

FIG. 13 is a diagram of various types of aberration of the second example at the wide-angle end when focused on infinity.

FIG. 14 is a diagram of various types of aberration in the second example when focused on an object at infinity at an intermediate focal length.

FIG. 15 is a diagram of various types of aberration of the second example at the telephoto end in the in-focus state at infinity.

FIG. 16 is a diagram of various types of aberration in a short-distance focus state at the wide-angle end according to the second example.

FIG. 17 is a diagram of various types of aberration in a short-distance focus state at the intermediate focal length according to the second example.

FIG. 18 is a diagram of various types of aberration in a close-distance focusing state at the telephoto end of the second example.

FIG. 19 is a diagram of various types of aberration at the wide-angle end (infinity in-focus state) and the telephoto end (infinity-in-focus state) before image stabilization in the second example.

FIG. 20 is a diagram of various types of aberration at the wide-angle end (infinity in-focus condition) and the telephoto end (infinity-in-focus condition) during image stabilization in the second embodiment.

[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

Claims (8)

[Claims] 1. A first lens group G1 having a negative refractive power and a second lens group G having a positive refractive power in order from the object side.
2, a third lens group G3 having a positive refractive power, a fourth lens group G4 having a negative refractive power, and a fifth lens group G5 having a positive refractive power, the zoom ratio is 1. In a zoom lens of 5 or more, the lateral magnification of the second lens group G2 is always positive and monotonically decreases during zooming from the wide-angle end to the telephoto end, and the second lens group G2 changes from the wide-angle end to the telephoto end. To the telephoto end from the wide-angle end of the fourth lens group G4 by ΔX2, and from the wide-angle end to the telephoto end of the fifth lens group G5. When the amount of movement in the optical axis direction is ΔX5, 0.0 <ΔX4 / ΔX2 <0.3 (0 <ΔX4) when changing the magnification from the wide-angle end to the telephoto end.
A zoom lens characterized by satisfying a condition of 3 <ΔX5 / ΔX2 <0.75 (0 <ΔX5). 2. The zoom lens according to claim 1, wherein the second lens group G2 is moved along the optical axis to focus on a short-distance object. 3. At the time of zooming from the wide-angle end to the telephoto end, the second lens group G2 moves along a convex trajectory toward the object side, and the third lens group G3 moves along a substantially linear trajectory. The zoom lens according to claim 1 or 2, wherein 4. The second lens group G2 moves along a substantially linear trajectory during zooming from the wide-angle end to the telephoto end.
The zoom lens according to claim 1, wherein the third lens group G3 moves along a trajectory that is convex toward the object side. 5. A focusing distance from an infinite object to a close-range object at the telephoto end, where ΔX _W is a movement amount of the second lens group G2 for focusing from an infinite object to a close-range object at the wide-angle end. The moving amount of the second lens group G2 for
The zoom lens according to claim 1, wherein a condition of 1.0 <ΔX _T / ΔX _W <1.5 is satisfied, where X _T. 6. The zoom lens according to claim 1, further comprising a displacement means for moving the second lens group G2 in a direction crossing the optical axis. 7. The second lens group G2 has at least 1
7. It has one cemented lens.
A zoom lens according to claim 1. 8. A moving amount of the second lens group G2 in the optical axis direction from the wide-angle end to the telephoto end is ΔX2, and a moving amount of the third lens group G3 in the optical axis direction from the wide-angle end to the telephoto end. ΔX
The zoom lens according to any one of claims 1 to 7, wherein when the zoom ratio is 3, the zoom lens satisfies the condition 1 <ΔX3 / ΔX2 <10 when zooming from the wide-angle end to the telephoto end.