JPH02103014A - Zoom lens having optical system for correcting camera-shake - Google Patents

Abstract

PURPOSE:To decreases the eccentric aberrations generated at the time of correcting a camera-shake by providing the optical system for correcting the camera-shake to a part of the optical system and satisfying specific conditions. CONSTITUTION:The zoom lens system is constituted successively from an object side, of a 1st lens group I having a positive refractive power, a 2nd lens group II having a positive refractive power, and a 3rd lens group III having a negative refractive power and the optical system for correcting the camera-shake is provided in the 2nd lens group II. The lens groups are so constituted as to satisfy the conditional equations where PHIS is the combined refractive power of the entire system in the shortest focal length state, phiFL, phiFM, phiFS are designated as the combined refractive powers from the lens on the extreme object side in the longest, intermediate, shortest focal length states up to the lens group contg. the optical system for correcting the camera-shake, and phiRL, phiRM, phiRS are designated as the combined refractive powers from the lens on the extreme object side in the longest, intermediate, shortest focal length states up to the lens group contg. the optical system for correcting the camera-shake.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a zoom lens having a camera shake correction optical system that corrects blurring of photographed images caused by vibrations during hand-held shooting of a camera. The present invention relates to a zoom lens that corrects blur in a photographed image by moving the lens group of the parts in a direction perpendicular to the optical axis.

(Prior Art) Most failures in conventional photography are due to out-of-focus and camera shake. However, in recent years, most cameras have come to employ an autofocus mechanism, and as the focusing accuracy of the autofocus mechanism has improved, failures in taking photographs due to out of focus have almost been eliminated. On the other hand, the lenses that come standard with cameras are changing from single focus lenses to zoom lenses. However, zoom lenses are generally designed to have higher magnification and telephoto lenses, and as a result, the effects of camera shake when taking photos have become even more noticeable, and most of the current failures in photography are due to camera shake. It can be said that it is.

On the other hand, lenses that correct the blurring of photographed images by moving some lens groups in the imaging optical system in a direction perpendicular to the optical axis are disclosed in, for example, JP-A-63-115126 and JP-A-63-1999. This has been proposed in Japanese Patent No. 133119 (hereinafter, a lens group that can be moved in a direction perpendicular to the optical axis will be referred to as a camera shake correction optical system).

Furthermore, as a mechanism for moving these camera shake correction optical systems, an acceleration sensor actuator or the like as disclosed in, for example, Japanese Patent Laid-Open No. 62-47011 is used.

(Problems to be Solved by the Invention) However, all the lenses described in the above-mentioned conventional examples are single-focus lenses, and there is no mention of a zoom lens to which a camera shake correction optical system is applied. In order to use an image stabilization optical system in a zoom lens, it is necessary to reduce the deterioration of aberrations due to eccentricity of the image stabilization optical system over the entire zoom range. However, it is difficult to minimize the deterioration of aberrations over the entire zoom range.

Therefore, an object of the present invention is to provide a zoom lens in which decentering aberrations caused by movement of the camera shake correction optical system are reduced over the entire zoom range.

(Means for Solving the Problems) In order to achieve the above object, a zoom lens having a camera shake correction optical system according to the present invention is characterized in that it satisfies the following conditional expression.

(1) 0<lψFL/φSl<1.43(2)
0<lψFM/Φ, 1<1.43(3) 0<lψF
S/ΦSl<1.43(4) O<lψRL/Φ, l
<2.0(5) to Owl, /ΦS1<2.0(6)
0<lψRM/Φ, l<2.0 (7) l to Ll>1
ψR51 However, Φ is the shortest focal length state (hereinafter referred to as the S state)
The composite refractive power of the entire system, ψFL, ψFM, ψ,.

are the longest focal length state (hereinafter referred to as L state), respectively.
Combined refractive power, ψRL, from the lens closest to the object side to the lens immediately before the image stabilization optical system in the intermediate focal length state (hereinafter referred to as the M state) and the S state.

ψRM and ψR8 are the composite refractive powers from the lens closest to the object to the lens group including the image stabilization optical system in the L state, M state, and S state, respectively, and the intermediate focal length is the longest focal length FL and the shortest focal length F.

Then, it is defined as fT7 Zheng.

Each condition will be explained below.

Conditional expressions (1) to (6) are conditions for suppressing the occurrence of decentering aberrations due to movement of the camera shake correction optical system.

Among these, conditions (1) to (3) are the composite refractive power of the lens group located on the object side of the camera shake correction optical system in the nL state, S state, and M state, respectively, and the composite refractive power of the entire system in the S state. , and corresponds to the incident angle α of the axial ray that simultaneously enters the camera shake correction optical system. As the value of condition (1) approaches O, the incident angle α becomes smaller.

In addition, conditions (4) to (6) mean that the composite refractive power from the image stabilization optical system to the lens closest to the object, including the image stabilization optical system in the L state, S state, and M state, is S
It is defined in relation to the composite refractive power of the entire system in the state, and at the same time corresponds to the exit angle β of the axial ray exiting from the camera shake correction optical system. Condition (2)
As the value of .beta. approaches 0, the exit angle .beta. becomes smaller.

By satisfying the above conditions (1) to (6), the L state,
The incident angle α and the exit angle β are kept small over the S state and the M state, and it is possible to reduce aberration fluctuations, especially fluctuations in axial coma aberration and astigmatism due to movement of the camera shake correction optical system. When the upper limits of the above conditions (1) to (6) are exceeded, the incident angle α or the exit angle β becomes extremely large, making it difficult to suppress aberration fluctuations due to eccentricity to a small level.

Condition (7) defines the relationship between the exit angle β of the axial ray exiting from the camera shake correction optical system in the L state and the S state. The amount of blur in a photographed image due to camera shake increases as the focal length becomes longer, so in a zoom lens, the influence of camera shake becomes impossible to ignore as the zoom lens changes from the S state to the dark state. Therefore, the amount of movement necessary for the camera shake correction optical system to correct the amount of blur in a photographed image increases as it approaches the L state, and the occurrence of eccentric aberration becomes more severe. Therefore, by making the exit angle in the L state, where the amount of movement of the camera shake correction optical system is maximum, smaller than the exit angle in the S state, aberration fluctuations due to movement of the camera shake correction optical system can be reduced. For the same amount of movement, the amount in the Hiroshi state is smaller than that in the S state.

In other words, in the state ■ where the amount of blur in the captured image to be corrected is large, the error sensitivity to eccentricity of the image stabilization optical system (
By making the amount of aberration variation/the amount of image height movement of a photographed image smaller than the value in the S state, a zoom lens with less deterioration in aberrations due to eccentricity over the entire zoom range can be constructed.

In specifically configuring the above zoom lens, in order from the object side, a first lens group (1) having a positive refractive power;
The second lens group (It) includes a second lens group (It) having a positive refractive power and a third lens group having a negative refractive power,
II) It is desirable to have a camera shake correction optical system in the camera and to satisfy the following conditions.

(8) 0.1<F2/FL<0.6(9) o
, 2<lfc/FLl<x,.

(I)) 0.1 < lψ,. /ψRo1〈3゜(
11) ol<lψp/<pRl<3.0, where F2 is the composite focal length of the second lens group (II), and fc is the focal length of the image stabilization optical system, ψ. is the refractive power and glaze of the surface closest to the object side of the image stabilization optical system. is the refractive power of the image-side surface of the image stabilization optical system, ψF is the refractive power of the image-side surface of the lens adjacent to the object side of the image stabilization optical system, and ψ2 is the refractive power of the image-side surface of the image stabilization optical system. This is the refractive power of the object-side surface of the adjacent lens.

In order to facilitate movement control of the camera shake correction optical system, it is desirable to make the camera shake correction optical system as small and lightweight as possible. In general, in lens systems, the front group (first lens group (1)) and rear group (third lens group (IID)) tend to have larger outer diameters and become heavier, so image stabilization optical systems It is not preferable to configure the front group and the rear group.

Therefore, it is desirable to provide the camera shake correction optical system in the second lens group (U), which has a relatively small outer diameter and is light in weight.

Furthermore, condition (8) is an expression that defines the composite focal length of the second lens group (II) with respect to the focal length of the entire system in the L state. If the lower limit of condition (8) is exceeded, the second lens group (I
If the refractive power (reciprocal of focal length) of I) becomes too strong,
It becomes difficult to keep aberration fluctuations due to eccentricity of the camera shake correction optical system small. Conversely, if the upper limit of condition (8) is exceeded and the refractive power of the second lens group (It) becomes too weak, the total length of the lens becomes long, which is undesirable.

Condition (9) id, which defines the focal length of the camera shake correction optical system with respect to the focal length of the entire system in the L state.

Similarly to condition (8), if the lower limit of condition (9) is exceeded and the refractive power of the image stabilization optical system becomes too strong, aberration fluctuations due to eccentricity of the image stabilization optical system will become extremely large, causing damage to the entire lens. The optical performance of Conversely, if the upper limit of condition (9) is exceeded and the refractive power of the image stabilization optical system becomes weak,
Although aberration fluctuations due to eccentricity are reduced, the camera shake correction optical system must be moved by a considerable amount in order to correct blur in a photographed image, which is not practical.

Furthermore, conditions (to) and (11) are both condition (9)
) is satisfied, the refractive powers of the camera shake correction optical system and the lens surface adjacent to the camera shake correction optical system are defined, respectively.

If the lower limit of condition (10) is exceeded and the refractive power of the surface closest to the image side of the image stabilization optical system becomes too strong relative to the refractive power of the surface closest to the object side, the axis due to eccentricity of the image stabilization optical system This is not preferable because upper coma aberration increases. On the contrary, if the condition (1
If the upper limit of 0) is exceeded and the refractive power of the surface closest to the object side becomes too strong, fluctuations in astigmatism due to eccentricity will increase, which is also undesirable.

However, if the upper limit of condition (11) is exceeded and the refractive power of the image-side surface of the lens adjacent to the object side of the image stabilization optical system becomes too strong, it will be difficult to suppress fluctuations in axial coma aberration. becomes. Conversely, if the lower limit of condition (11) is exceeded and the refractive power on the object side of the lens adjacent to the image side of the image stabilization optical system becomes too strong, although it is possible to reduce fluctuations in axial coma aberration, , astigmatism, especially fluctuations in astigmatism in the L state, become so large that they cannot be corrected.

(Example) Table 1 below shows the configuration of a zoom lens to which the present invention is applied when focusing on an object at infinity. In this example, r
i indicates the first lens surface from the object side, and the (yellow) mark indicates that the lens surface is aspheric. The shape of the aspherical surface is defined by the following formula, where X is the amount of displacement of the lens surface from the spherical surface at the height Y from the optical axis, CO is the curvature of the spherical surface that is the reference for the aspherical surface, and A
i is an aspheric coefficient.

Table 1 f = 36.2~60.0~100.0F pt,
= 3.7~4.9~58 Radius of curvature Axial spacing Refractive index (Nd) Atsube number (νd) Σd=55.518~54.576~55.890 Aspheric coefficient rho" A4-0.19170XIO-3A6 =-
0,10626X10-5 As= 0.19784xlO-7 A10=-0,29564X10-9 At2=-0,70944xlO-"rla" A4= 0.65175X10-'A6=
-〇, 64039X10-' A8 = 0.21347 mowing 0-7 A10 = -0, 21771X10-9 A12 = 0.86887xlO-12 Fig. 1 shows cross-sectional views of the zoom lens with the above configuration in the S state and the L state.
Shown in Figure 2. Further, aberration diagrams of this example are shown in FIGS. 3 to 8. Of these, Figs. 3, 5, and 7 show the optical plane (Y'
), and Figures 4, 6, and 8 similarly show the case where the image stabilization optical system is parallel decentered by 1.0 at f=362 fin, 60 mm, and 100 adjustment. shows the lateral aberration on the U-plane.

Note that Table 2 shows values regarding each conditional expression of this embodiment.

Table 2

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the lens in the S state of the embodiment of the present invention, FIG. 2 is a cross-sectional view of the lens in the L state of the embodiment of the present invention, and FIGS. 3 to 8 are aberration diagrams of the embodiment of the present invention. It is. Applicant: Minolta Camera Co., Ltd.

Claims (1)

[Scope of Claims] (1) A camera shake correction optical system that corrects image blur caused by camera shake by moving some lens groups in the imaging optical system in a direction perpendicular to the optical axis; A zoom lens having a camera shake correction optical system that satisfies the following conditions: 0<|ψ_F_L/Φ_S|<1.43 0<|ψ_F_M/Φ_S|<1.43 0<|ψ_F_S / Φ_s ｜ <ψ1.43 0 <| ψ_R_L / φ_s ｜ <2.0 0 <| ψ_r_s / φ_s ｜ <2.0 0 < is the composite refractive power of the entire system in the shortest focal length state, and ψ_F_L, ψ_F_M, and ψ_F_S are the lens closest to the object side to the lens immediately before the image stabilization optical system in the longest focal length state, intermediate focal length state, and shortest focal length state, respectively. composite refractive power, ψ_R_L, ψ_R_M
, ψ_R_S are the composite refractive powers from the lens closest to the object to the lens group including the image stabilization optical system in the longest focal length state, intermediate focal length state, and shortest focal length state, respectively, and the intermediate focal length is the maximum focal length When F_L and the shortest focal length are F_S, it is defined as √(f_L·f_S). (2) The 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;
Claim (1) characterized in that the lens group includes a camera shake correction optical system, the axial distance between at least the first lens group and the second lens group changes during zooming, and the following conditions are satisfied: A zoom lens having the camera shake correction optical system described above: 0.1<F_2/F_L<0.6 where F_2 is the composite focal length of the second lens group. (3) A zoom lens having a camera shake correction optical system according to claim (2), which satisfies the following conditions in addition to the above conditions: 0.2<|f_C/F_L|<1. 0 0.1<|ψ_F_C/ψ_R_C|<300.1<|
ψ_F/ψ_R | <3.0 However, f_C is the focal length of the image stabilization optical system, ψ_F_
C is the refractive power of the surface closest to the object side of the image stabilization optical system, ψ_
F_R is the refractive power of the image-side surface of the image stabilization optical system, ψ
_F is the refractive power of the image side surface of the lens adjacent to the object side of the camera shake correction optical system, and ψ_R is the refractive power of the object side surface of the lens adjacent to the image side of the camera shake correction optical system.