JPH08122711A - Vibrationproofing correction optical system - Google Patents

Abstract

PURPOSE: To provide a vibrationproofing correction optical system with small number of constitutional lenses of an eccentric lens group and satisfactory image-forming performance even in vibrationproofing correction. CONSTITUTION: In this vibrationproofing correction optical system provided with a lens group Gf fixed in a direction perpendicular to an optical axis and a vibrationproofing correction lens group Gv including the eccentric lens group movable in a direction nearly perpendicular to the optical axis sequentially from an object side, the lens group Gf is equipped with a first lens group G1 with positive refracting power, a focusing lens group G2 with negative refracting power and which performs focusing on an object at near distance by moving along the optical axis and a lens group G3a, and the vibrationproofing correction lens group Gv is equipped with the eccentric lens group G3b with at least one aspherical lens, which satisfies a condition 4.0|ff/f| assuming the focal distance of the lend group Gf as ff, and that of the whole optical system as (f).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image stabilization optical system,
More specifically, it is possible to correct the fluctuation of the image position due to camera shake when photographing through the photographing optical system, and the fluctuation of the image position occurring when photographing in a vibrating place such as an automobile or a helicopter. The present invention relates to an image stabilization optical system.

[0002]

2. Description of the Related Art A conventional image stabilization optical system is disclosed in Japanese Patent Laid-Open No.
-115126, JP-A-63-133119, JP-A-63-202714, JP-A-2-23
As disclosed in Japanese Patent Publication No. 0114, etc., by eccentricizing a part of the lens group of the optical system substantially perpendicularly to the optical axis, the fluctuation of the image position due to the shaking of the optical system due to camera shake or the like is corrected. ing. In this specification, the movement of the lens group in a direction substantially orthogonal to the optical axis to correct the fluctuation of the image position caused by camera shake or the like is referred to as “anti-vibration” or “anti-vibration correction”. A lens group that is eccentrically moved in a direction substantially orthogonal to the optical axis is referred to as an "eccentric lens group".

[0003]

However, in the conventional image stabilization optical system as described above, in order to keep the aberration characteristics of the decentering lens group at the time of decentering, that is, at the time of image stabilization as well,
The number of constituent lenses of the eccentric lens group increases and the size increases, and the weight also increases. JP-A-63-133119
In the image stabilization optical system disclosed in Japanese Patent Application Laid-Open No. 63-202714 and Japanese Patent Application Laid-Open No. 2-230114,
The decentering lens group is composed of three or more lenses.
As a result, the conventional image stabilization optical system as described above has a disadvantage that the load of the actuator for eccentrically driving the eccentric lens group is large.

Japanese Patent Laid-Open No. 63-115126 discloses an image stabilization optical system in which the decentering lens group is composed of two lenses. However, in the image stabilization optical system disclosed in this publication, since the whole extension method is adopted as the focusing method, the operability is remarkably inferior to the internal focusing method and is not realistic. The present invention has been made in view of the above problems, and an object thereof is to provide an image stabilization optical system having a small number of constituent lenses in a decentering lens group and having good imaging performance even during image stabilization. And

[0005]

In order to solve the above-mentioned problems, in the present invention, in order from the object side, a lens group Gf fixed in a direction perpendicular to the optical axis and a lens group Gf fixed in a direction substantially perpendicular to the optical axis. Anti-vibration correction lens group G including a movable eccentric lens group
In the image stabilization optical system including v and
f is a first lens group G1 having a positive refractive power, a focusing lens group G2 having a negative refractive power and moving along the optical axis to focus on a short-distance object, and a lens group G3a. When the image stabilization lens group Gv includes an eccentric lens group G3b having at least one aspherical lens, the focal length of the lens group Gf is ff, and the focal length of the entire optical system is f. , 4.0 <| ff / f | is satisfied, and an image stabilization optical system is provided.

According to a preferred aspect of the present invention, when the radius of curvature of the object-side surface of the aspherical lens is ra and the radius of curvature of the image-side surface of the aspherical lens is rb, 0.4 < The condition of (rb + ra) / (rb-ra) <1.0 is satisfied.

[0007]

In a normal internal focusing type telephoto lens that does not have a decentering mechanism (anti-vibration correction mechanism), the first lens group having a positive refractive power,
The second lens group having negative refracting power for focusing and the third lens group having positive refracting power are used in order to reduce the total lens length and simplify the focusing mechanism. ) Arrangement. In this type of telephoto lens, it is better to cancel the aberrations generated in each lens group with each other and to reduce the aberrations as a whole lens system without individually correcting the aberrations in each lens group. The number of constituent lenses of the lens group is small, which is economically advantageous.

When an eccentric mechanism is added to a normal internal focusing type telephoto lens to construct an anti-vibration optical system, the diameter of the eccentric mechanism is relatively small so that an actuator, which is a driving means, has a small load. It is preferable that the second lens group or the third lens group is a decentered lens group. Considering the aberration after decentering, that is, the aberration at the time of image stabilization, it is preferable to correct the aberration in the decentering lens unit and dispose this decentering lens unit on the image side of the afocal system.

By the way, in an internal focusing type telephoto lens having no decentering mechanism, the combined focal length of the first lens group and the second lens group is positively or negatively large from the viewpoint of shortening the total lens length and correcting aberrations. , Constitutes almost an afocal system.
Therefore, it is optimal to select the third lens group as the decentering lens group in order to suppress the aberration variation due to the decentering. However, the third lens group is an eccentric lens group,
If the third lens group, which is the decentering lens group, is used alone to correct the aberrations after the decentering, the aberration balance canceled by the lens groups of the entire lens system will be lost.

Therefore, in the conventional anti-vibration correction optical system in which the decentering mechanism is added to the normal internal focusing type telephoto lens, the third lens, which is the decentering lens group, is used in order to satisfactorily correct various aberrations of the entire lens system. Aberrations of the entire lens system are corrected both before and after decentering by correcting aberrations not only in the group but also in the first lens group and the second lens group independently.

That is, in the conventional optical system in which the internal focusing type telephoto lens is changed to the image stabilization optical system with the decentering mechanism, the first lens group having a positive refracting power and the second lens group having a negative refracting power for focusing are used. And the third decentering lens unit having a positive refracting power.
It is composed of three lens groups. In order to satisfactorily correct various aberrations after decentering, it is necessary to correct aberrations in each lens group including the third lens group, which is a decentering lens group. For this reason, the number of lenses of the third lens group, which is the eccentric lens group, increases, and the weight increases, so that the load on the actuator that eccentrically drives the eccentric lens group increases.

Let us consider the decentering lens group. First, a light ray that is incident on the lens surface of the optical system that is closest to the object side in parallel to the optical axis will be referred to as a Rand light ray. At this time, considering the aberration of the Rand ray after decentering, it is desirable that the decentering lens group has a minimum deviation angle with respect to the Rand ray. Then, when taking the minimum argument, Ran
It is optimum that the d ray is substantially parallel to the optical axis in consideration of the aberration variation after decentering.

Further, no matter what height of the Rand ray is incident on the most object-side lens surface of the optical system, when the Rand ray is incident on the decentering lens group, the Rand ray is parallel to the optical axis. preferable. Therefore, R incident on the decentering lens group
In order to make the and light rays substantially parallel to the optical axis, it is optimal to make all the lens groups on the object side of the decentering lens group, that is, the front optical system, substantially afocal.

Therefore, in the image stabilization optical system of the present invention, the lens group Gf fixed in the direction perpendicular to the optical axis and the decentering lens group movable in the direction substantially perpendicular to the optical axis are arranged in this order from the object side. In the image stabilization optical system including the image stabilization lens group Gv, the lens group Gf includes a first lens group G1 having a positive refracting power and a negative refracting power along the optical axis. A focusing lens group G2 that moves to focus on a short-distance object and a lens group G3a are provided, and the image stabilization lens group Gv includes a decentering lens group G3b having at least one aspherical lens. The lens group Gf substantially forms an afocal system.

That is, in the present invention, in order to reduce the number of lenses of the decentering lens group, the following structure is adopted. First, a correction for correcting the normal aberration that occurs due to the eccentric lens group G3b having a small aberration variation due to decentering and the decentering lens group G3b configured so that the aberration variation due to decentering is reduced in the third lens group. It is divided into a lens group G3a.

Further, as described above, no matter what height of the Rand ray is incident on the most object-side lens surface of the optical system, when the Rand ray is incident on the decentering lens group G3b, the Rand ray is almost on the optical axis. It is desirable to make them parallel. Therefore, the correction lens group G3a is disposed on the object side of the decentering lens group G3b, and the front optical system is composed of the first lens group G1 having positive refractive power, the focusing lens group G2 having negative refractive power, and the correction lens group G3a. The lens group Gf, which is, is a substantially afocal system.

That is, in the present invention, the following conditional expression (1) is satisfied in order to make the lens group Gf substantially afocal. 4.0 <| ff / f | (1) where, ff: focal length of lens group Gf f: focal length of the entire optical system

Conditional expression (1) defines an appropriate range for the ratio of the focal length ff of the lens group Gf and the focal length f of the entire optical system, and makes the front lens group Gf substantially afocal. It is a condition for. When the value goes below the lower limit of conditional expression (1), the focal length of the front lens group Gf is not sufficient, and when entering the decentering lens group G3b, the Rand ray does not become substantially parallel to the optical axis. .

Further, in the present invention, it is considered that aberration correction should be performed on the entire optical system during infinity shooting, short distance shooting, and after decentering. Therefore, it is appropriate to correct the aberrations of the front lens Gf as a lens group in which aberration does not change even during short-distance shooting during focusing, and the image stabilization lens group Gv as a lens group in which aberration does not change due to decentering. is there. As a result, aberrations other than the aberration variation due to focusing and the aberration variation due to decentering may be canceled between the front lens group Gf and the image stabilization lens group Gv. That is, unlike the conventional case, it is not necessary to individually perform complete aberration correction within each lens group of the first lens group G1, the second lens group G2, and the third lens group, so that the number of lenses in each lens group, especially It is possible to reduce the number of constituent lenses of the decentering lens group G3b.

Furthermore, if chromatic aberration remains in the decentering lens group G3b without being sufficiently achromatic, chromatic aberration occurs after decentering as if the light beam was bent by a prism. Therefore, in addition to the above consideration, considering that the resolving power deteriorates due to chromatic aberration, the following four points are listed as the main necessary conditions for the configuration of the decentering lens group G3b. The eccentric lens group should have as few lenses as possible and be small and lightweight. The eccentric lens group should have a minimum deviation angle with respect to the Rand ray. The eccentric lens group should be sufficiently achromatic. Aberration variation due to eccentricity is sufficiently corrected

In consideration of the above four points, in the present invention, at least one aspherical lens is used and the decentering lens group G3b is used.
Is composed of the minimum number of lenses. Even when the decentering lens group is configured with a small number of lenses, the above condition can be satisfied by making the front optical system almost afocal, but the condition and the condition may be slightly insufficient. is there. Regarding the conditions, it is preferable that chromatic aberration is corrected within the decentering lens group G3b as much as possible, but in the present invention, an optical material having a large Abbe number νd is used for the aspherical lens so that chromatic aberration after decentering is reduced. Are using. By using such an eccentric lens group using one aspherical lens, it is possible to maintain good aberrations even after decentering.

Further, in the present invention, since the aspherical lens forming the decentering lens group G3b has the minimum deviation angle with respect to the Rand ray, it is preferable that the following conditional expression (2) is satisfied. 0.4 <(rb + ra) / (rb-ra) <1.0 (2) where ra: radius of curvature of object-side surface of aspherical lens rb: radius of curvature of image-side surface of aspherical lens

Conditional expression (2) defines the shape of the aspherical lens for taking the minimum deviation angle with respect to the Rand ray, that is, the shape factor. Within the range defined by the upper limit value and the lower limit value of the conditional expression (2), even after decentering, the Rand ray has a substantially minimum declination angle. However, if it deviates from the above range, the fluctuation of the spherical aberration and the fluctuation of the coma due to the eccentricity become large.

Further, when the decentering lens group is constructed with a small number of lenses as in the present invention, in order to more satisfactorily satisfy the above conditions and, the aberration generated in the decentering lens group G3b is corrected by the correction lens group G3a. It is good to effectively assist the correction. Therefore, the correction lens group G3a has at least one positive lens and at least one negative lens,
It is preferable that the following conditional expression (3) is satisfied. −2.5 <φ3an / φ3ap <−0.9 (3) Here, φ3ap: synthetic refractive power of the positive lens forming the lens group G3a φ3an: synthetic refractive power of the negative lens forming the lens group G3a

Since the decentering lens group G3b has a positive refracting power, spherical aberration and field curvature peculiar to the positive lens occur in the decentering lens group G3b. Therefore, the conditional expression (3) defines a condition for strengthening a slightly negative refracting power in the correction lens group G3a to cancel spherical aberration and field curvature peculiar to the positive lens. Further, the correction lens group G3a is
Having a positive lens and a negative lens in order from the object side is a preferable arrangement for shortening the total lens length.

In order to obtain a good aberration balance,
It is preferable that the following conditional expression (4) is satisfied. 0.3 <| f3a / f | (4) where, f3a: focal length of the correction lens group G3a

Conditional expression (4) defines an appropriate range for the ratio between the refractive power of the correction lens group G3a and the refractive power of the entire lens system. When the value goes below the lower limit of the conditional expression (4), the refracting power of the correction lens group G3a for assisting the aberration correction becomes too large, and high-order aberrations occur in the correction lens group G3a, so that the aberration balance is disturbed. Will end up.

Further, in order to reduce aberration variation due to eccentricity and obtain good image forming characteristics, the correction lens group G3a is composed of a positive lens and a negative lens in order from the object side, and the following conditional expressions (5) and ( It is preferable to satisfy the expression (6). 0.4 <r1 / r2 <1.0 (5) 0.6 <r3 / r4 <1.8 (6) where, r1: radius of curvature of the image side surface of the positive lens of the correction lens group G3a r2: Curvature radius of the object side surface of the negative lens of the correction lens group G3a r3: Curvature radius of the image side surface of the negative lens of the correction lens group G3a r4: Curvature of the object side surface of the aspherical lens of the decentering lens group G3b radius

In conditional expressions (5) and (6), the Rand ray incident on the decentering lens group G3b is a light beam regardless of the height of the Rand ray incident on the most object-side lens surface of the optical system. It is a condition for becoming almost parallel to the axis. If the ranges of the conditional expressions (5) and (6) are exceeded, it becomes difficult to make the Rand ray incident on the decentering lens group G3b substantially parallel to the optical axis.

[0030]

In each of the embodiments, the image stabilization optical system according to the present invention has, in order from the object side, a lens group Gf fixed in the direction perpendicular to the optical axis, and a lens unit movable in the direction substantially perpendicular to the optical axis. An image stabilization lens group Gv including a core lens group, and the lens group Gf is a first lens group G1 having a positive refractive power.
And a focusing lens group G2 that has a negative refractive power and moves along the optical axis to focus on a short-distance object, and a lens group G3a, and the image stabilization lens group Gv is at least 1 Decentering lens group G3b having two aspherical lenses
It has.

Each embodiment of the present invention will be described below with reference to the accompanying drawings. [Embodiment 1] FIG. 1 is a view showing the lens arrangement of an image stabilization optical system according to the first embodiment of the present invention. The image stabilization optical system shown in the figure includes, from the object side, a first lens group G1 including a biconvex lens, a biconvex lens, and a biconcave lens, and a cemented negative lens composed of a positive meniscus lens having a concave surface facing the object side and a biconcave lens. The focusing lens group G2, a correction lens group G3a including a cemented lens of a biconvex lens and a biconcave lens, and a decentering lens group G3b including a biconvex aspherical lens. The decentering lens group G3
An aperture stop is provided on the image side of b.

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 and F is
_NO represents the F number and Bf represents the back focus. Furthermore, the leftmost number indicates the order of each lens surface from the object side,
r is the radius of curvature of each lens surface, d is the distance between each lens surface,
n and ν represent the refractive index and the Abbe number for the d line (λ = 587.6 nm).

The aspherical surface has a height y in the direction perpendicular to the optical axis,
When the amount of displacement in the optical axis direction at height y is S (y), the reference radius of curvature, that is, the radius of curvature of the apex is r, the cone coefficient is k, and the aspherical coefficient of order n is Cn, It is represented by.

[Formula 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 radius of curvature 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 the embodiment is marked with * on the right side of the surface number.

[0034]

[Table 1] f = 180 mm F _NO = 2.8 rd ν n 1 150.240 7.41 69.9 1.51860 2 -260.534 0.10 3 76.990 11.88 82.6 1.49782 4 2672.582 1.08 5 -650.620 3.00 27.6 1.75520 6 203.650 33.41 7 -171.187 3.52 25.5 1.80458 8 -89.111 4.10 64.1 1.51680 9 63.332 19.45 10 98.691 6.61 43.3 1.84042 11 -54.362 3.00 42.0 1.66755 12 50.935 3.00 13 * 60.419 3.93 95.0 1.43425 14 -390.015 Bf = 89.51 (aspherical data) k C ₂ C ₄ 13 surface 1.0000 0.0000 -0.2994 × 10 ^-6 C ₆ C ₈ C ₁₀ -0.4094 × 10 ^-9 0.0000 0.0000 (Condition corresponding value) (1) | ff / f | = 4.18 (2) (rb + ra) / (rb-ra) = 0. 732 (3) φ3an / φ3ap = −1.09 (4) | f3a / f | = 6.67 (5) r1 / r2 = 1.0 (6) r3 / r4 = 0.843

FIG. 2 is a diagram showing various aberrations of the first embodiment in the in-focus state at infinity. FIG. 3 is an aberration diagram showing the lateral aberration before the image stabilization (before decentering) and the lateral aberration during the image stabilization (after decentering) in the infinity in-focus state of the first example. .
In the aberration diagrams of FIG. 2, F _NO represents the F number, Y represents the image height, D represents the d line (λ = 587.6 nm), and G represents the g line (λ = 435.8 nm). . Also,
In the aberration diagram showing astigmatism, the solid line shows the sagittal image plane, and the broken line shows the meridional image plane. further,
In the aberration diagram showing the spherical aberration, the broken line shows the sine condition (sine condition). Further, in the lateral aberration diagram of FIG. 3, the solid line shows the lateral aberration before the image stabilization, and the broken line shows the lateral aberration during the image stabilization. As is clear from each of the aberration diagrams, in the present example, it is understood that various aberrations are well corrected, including at the time of image stabilization correction.

[Embodiment 2] FIG. 4 is a view showing the lens arrangement of an image stabilization optical system according to the second embodiment of the present invention.
The illustrated image stabilization optical system includes a first lens group G1 including, in order from the object side, a biconvex lens, a biconvex lens, a biconcave lens, and a positive meniscus lens having a convex surface facing the object side, a biconcave lens, and a biconvex lens. It is composed of a focusing lens group G2 made of a cemented lens with a concave lens, a correction lens group G3a made of a positive meniscus lens having a concave surface facing the object side and a biconcave lens, and an eccentric lens group G3b made of a biconvex aspherical lens. ing. An aperture stop is provided on the image side of the decentering lens group G3b.

The following table (2) lists the values of specifications of the second embodiment of the present invention. In Table (2), f is the focal length, F
_NO represents the F number and Bf represents the back focus. Furthermore, the leftmost number indicates the order of each lens surface from the object side,
r is the radius of curvature of each lens surface, d is the distance between each lens surface,
n and ν represent the refractive index and the Abbe number for the d line (λ = 587.6 nm).

[0038]

[Table 2] f = 300 mm F _NO = 4.0 rd ν n 1 180.569 9.63 69.9 1.51860 2 -389.102 0.27 3 92.999 11.10 82.6 1.49782 4 -408.534 0.10 5 -392.046 2.99 35.2 1.74950 6 166.071 0.25 7 124.638 4.90 69.9 1.51860 8 462.678 50.05 9 -1175.196 2.80 45.0 1.74400 10 95.980 1.80 11 840.898 4.97 27.6 1.75520 12 -51.345 2.80 52.3 1.74810 13 82.072 15.30 14 -620.041 3.23 52.3 1.74810 15 -72.443 0.93 16 -150.233 2.80 33.7 1.64831 17 157.170 3.00 18 * 91.982 19 -382.542 Bf = 132.89 (aspherical surface data) k C ₂ C ₄ 18 surface 1.0000 0.0000 -0.2023 × 10 ^-6 C ₆ C ₈ C ₁₀ 0.0000 0.0000 0.0000 (Values corresponding to conditions) (1) | ff / f | = 17 .58 (2) (rb + ra) / (rb-ra) = 0.612 (3) φ3an / φ3ap = −0.926 (4) | f3a / f | = 4.22 (5) r1 / r2 = 0.58. 482 (6) r3 / r4 = 1.709

FIG. 5 is a diagram showing various aberrations of the second embodiment in the in-focus state at infinity. FIG. 6 is an aberration diagram showing, in contrast, the lateral aberration before the image stabilization correction and the lateral aberration during the image stabilization correction in the infinity in-focus state of the second example. In the aberration diagrams of FIG. 5, F _NO is the F number, Y is the image height, and D is the d line (λ =
587.6 nm) and G is the g-line (λ = 435.8 nm)
Are shown respectively. Further, in the aberration diagram showing astigmatism, the solid line shows the sagittal image plane and the broken line shows the meridional image plane. Further, in the aberration diagram showing spherical aberration, the broken line shows the sine condition (sine condition). Further, in the lateral aberration diagram of FIG. 6, the solid line shows the lateral aberration before the image stabilization, and the broken line shows the lateral aberration during the image stabilization. As is clear from each of the aberration diagrams, in the present example, it is understood that various aberrations are well corrected, including at the time of image stabilization correction.

[Embodiment 3] FIG. 7 is a diagram showing a lens configuration of an image stabilization optical system according to a third embodiment of the present invention.
The image stabilization optical system shown in the figure includes, from the object side, a first lens group G1 including a biconvex lens, a biconvex lens, and a biconcave lens, and a cemented negative lens composed of a positive meniscus lens having a concave surface facing the object side and a biconcave lens. And a correction lens group G3a including a positive meniscus lens having a concave surface facing the object side and a biconcave lens, and a decentering lens group G3b including a biconvex aspherical lens. An aperture stop is provided on the image side of the decentering lens group G3b.

Table (3) below shows the values of specifications of the third embodiment of the present invention. In Table (3), f is the focal length, F
_NO represents the F number and Bf represents the back focus. Furthermore, the leftmost number indicates the order of each lens surface from the object side,
r is the radius of curvature of each lens surface, d is the distance between each lens surface,
n and ν represent the refractive index and the Abbe number for the d line (λ = 587.6 nm).

[0042]

[Table 3] f = 400 mm F _NO = 5.6 r d ν n 1 154.255 8.87 69.9 1.51860 2 -275.779 1.90 3 98.347 9.21 82.6 1.49782 4 -387.526 0.57 5 -320.052 2.60 35.2 1.74950 6 191.508 67.23 7 -319.750 2.64 27.6 1.74077 8 -87.778 3.54 58.5 1.65 160 9 93.851 13.76 10 -485.500 2.60 31.6 1.75692 11 -98.471 10.40 12 -229.658 2.60 40.3 1.60717 13 80.472 3.00 14 * 98.210 5.00 69.9 1.51860 15 -3890.088 Bf = 161.05 (aspheric surface data) k C ₂ C ₄ 14 faces 1.0000 0.0000 -0.1521 × 10 ^-6 C ₆ C ₈ C ₁₀ 0.6048 × 10 ^-10 0.0000 0.0000 (Values corresponding to conditions) (1) | ff / f | = 9.00 (2) (rb + ra) / (rb- ra) = 0.951 (3) φ3an / φ3ap = −1.66 (4) | f3a / f | = 0.742 (5) r1 / r2 = 0.429 (6) r3 / r4 = 0.819

FIG. 8 is a diagram showing various aberrations of the third embodiment in the in-focus state at infinity. FIG. 9 is an aberration diagram showing, in contrast, the lateral aberration before the image stabilization correction and the lateral aberration during the image stabilization correction in the infinity in-focus state of the third example. In the aberration diagrams of FIG. 8, F _NO is the F number, Y is the image height, and D is the d line (λ =
587.6 nm) and G is the g-line (λ = 435.8 nm)
Are shown respectively. Further, in the aberration diagram showing astigmatism, the solid line shows the sagittal image plane and the broken line shows the meridional image plane. Further, in the aberration diagram showing spherical aberration, the broken line shows the sine condition (sine condition). In the lateral aberration diagram of FIG. 9, the solid line shows the lateral aberration before the image stabilization correction, and the broken line shows the lateral aberration before the image stabilization correction. As is clear from each of the aberration diagrams, in the present example, it is understood that various aberrations are well corrected, including at the time of image stabilization correction.

[Embodiment 4] FIG. 10 is a diagram showing a lens configuration of an image stabilization optical system according to a fourth embodiment of the present invention. The image stabilization optical system shown in the figure includes, from the object side, a first lens group G1 including a biconvex lens, a biconvex lens, and a biconcave lens, and a cemented negative lens composed of a positive meniscus lens having a concave surface facing the object side and a biconcave lens. And a correction lens group G3a including a biconvex lens and a biconcave lens, and a decentering lens group G3b including a biconvex aspherical lens. An aperture stop is provided on the image side of the decentering lens group G3b.

Table (4) below shows the values of specifications of the fourth embodiment of the present invention. In Table (4), f is the focal length, F
_NO represents the F number and Bf represents the back focus. Furthermore, the leftmost number indicates the order of each lens surface from the object side,
r is the radius of curvature of each lens surface, d is the distance between each lens surface,
n and ν represent the refractive index and the Abbe number for the d line (λ = 587.6 nm).

[0046]

[Table 4] f = 600 mm F _NO = 5.6 rd ν n 1 200.793 15.30 82.6 1.49782 2 -357.743 1.29 3 146.613 16.30 82.6 1.49782 4 -508.827 2.03 5 -380.563 7.12 35.2 1.74950 6 287.106 61.06 7 -2109.331 6.65 25.4 1.80518 8 -264.297 6.32 49.4 1.77279 9 209.371 52.83 10 379.365 6.00 30.1 1.69895 11 -185.088 31.34 12 -189.513 6.00 46.4 1.80411 13 98.412 3.00 14 * 145.862 5.00 95.0 1.43425 15 -443.261 Bf = 189.71 (aspheric data) k C ₂ C ₄ 14 Surface 1.0000 0.0000 -0.8466 × 10 ^-7 C ₆ C ₈ C ₁₀ 0.5631 × 10 ^-10 0.0000 0.0000 (Value corresponding to the condition) (1) | ff / f | = 4.15 (2) (rb + ra) / (rb-ra ) = 0.505 (3) φ3an / φ3ap = −2.24 (4) | f3a / f | = 0.370 (5) r1 / r2 = 0.977 (6) r3 / r4 = 0.675

FIG. 11 is a diagram of various types of aberration in the fourth embodiment when focused on an object at infinity. FIG. 12 is an aberration diagram showing, in contrast, the lateral aberration before the image stabilization correction and the lateral aberration during the image stabilization correction in the infinity in-focus state of the fourth example. In the aberration diagrams of FIG. 11, F _NO is the F number, Y is the image height, D is the d line (λ = 587.6 nm), and G is the g line (λ = 435.8).
nm) respectively. Further, in the aberration diagram showing astigmatism, the solid line shows the sagittal image plane and the broken line shows the meridional image plane. Further, in the aberration diagram showing spherical aberration, the broken line shows the sine condition (sine condition). In addition, in the lateral aberration diagram of FIG.
The solid line shows the lateral aberration before the image stabilization, and the broken line shows the lateral aberration at the image stabilization. As is clear from each of the aberration diagrams, in the present example, it is understood that various aberrations are well corrected, including at the time of image stabilization correction.

[0048]

As described above, according to the present invention, it is possible to realize an image stabilization optical system having a small number of lenses in the decentering lens group and having good imaging performance during image stabilization. Further, in the present invention, since the decentering lens group can be made an aspherical lens to be small and lightweight, it is possible to reduce the load on the drive device for image stabilization. Furthermore, it is possible to configure the image stabilization optical system of the present invention as a tracking device that constantly frames a specific subject at a predetermined location.

[Brief description of drawings]

FIG. 1 is a diagram showing a lens configuration of an image stabilization optical system according to Example 1 of the present invention.

FIG. 2 is a diagram of various types of aberration in the first example when focused on an object at infinity;

FIG. 3 is an aberration diagram showing, in contrast, the lateral aberration before the image stabilization is corrected and the lateral aberration during the image stabilization in the infinity in-focus state of the first example.

FIG. 4 is a diagram showing a lens configuration of an image stabilization optical system according to Example 2 of the present invention.

FIG. 5 is a diagram of various types of aberration in the second example upon focusing at infinity.

FIG. 6 is an aberration diagram showing, in contrast, the lateral aberration before the image stabilization correction and the lateral aberration during the image stabilization correction in the infinity in-focus state of the second example.

FIG. 7 is a diagram showing a lens configuration of an image stabilization optical system according to Example 3 of the present invention.

FIG. 8 is a diagram of various types of aberration in the in-focus state of 3rd Example.

FIG. 9 is an aberration diagram showing, in contrast, the lateral aberration before the image stabilization is corrected and the lateral aberration during the image stabilization in the infinity in-focus state of the third example.

FIG. 10 is a diagram showing a lens configuration of an image stabilization optical system according to Example 4 of the present invention.

FIG. 11 is a diagram of various types of aberration in the fourth embodiment upon focusing at infinity.

FIG. 12 is an aberration diagram showing, in contrast, the lateral aberration before the image stabilization correction and the lateral aberration during the image stabilization correction in the infinity in-focus state of the fourth example.

[Explanation of symbols]

 Gf Afocal lens group Gv Anti-vibration correction lens group G1 First lens group G2 Focusing lens group G3a Correction lens group G3b Decentering lens group

Claims (5)

[Claims] 1. A lens group Gf fixed in a direction perpendicular to the optical axis and an image stabilization lens group Gv including a decentering lens group movable in a direction substantially perpendicular to the optical axis in order from the object side. In the image stabilization optical system provided, the lens group Gf has a first lens group G1 having a positive refractive power, and has a negative refractive power to move along the optical axis to focus on a short-distance object. Focusing lens group G2 and a lens group G3a, the image stabilization lens group Gv includes an eccentric lens group G3b having at least one aspherical lens, and the focal length of the lens group Gf is ff. , Where the focal length of the entire optical system is f, the image stabilization optical system satisfies the condition of 4.0 <| ff / f |. 2. When the radius of curvature of the object side surface of the aspherical lens is ra and the radius of curvature of the image side surface of the aspherical lens is rb, 0.4 <(rb + ra) / (rb- The image stabilization optical system according to claim 1, wherein the condition of ra) <1.0 is satisfied. 3. The lens group G3a has at least one positive lens and at least one negative lens, and the combined refractive power of the positive lenses constituting the lens group G3a is φ3ap, and the lens group G3a is The anti-vibration correction optical system according to claim 1 or 2, wherein a condition of -2.5 <φ3an / φ3ap <-0.9 is satisfied, when the composite refractive power of the negative lenses constituting the lens is φ3an. . 4. The focal length of the lens group G3a is f3a
4. When the focal length of the entire optical system is f, the condition of 0.3 <| f3a / f | is satisfied, and the image stabilization optical system according to any one of claims 1 to 3. system. 5. The lens group G3a comprises, in order from the object side, a positive lens and a negative lens, wherein the radius of curvature of the image side surface of the positive lens of the lens group G3a is r1 and the negative lens of the lens group G3a is negative. The radius of curvature of the object side surface of the lens is r2, the radius of curvature of the image side surface of the negative lens of the lens group G3a is r3, and the eccentric lens group G is
When the radius of curvature of the object-side surface of the aspherical lens 3b is r4, the following conditions are satisfied: 0.4 <r1 / r2 <1.0 0.6 <r3 / r4 <1.8 The image stabilization optical system according to any one of claims 1 to 4.