JP2535969B2 - Variable magnification optical system with anti-vibration function - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention provides a function of correcting blurring of a captured image due to vibration,
Regarding a variable power optical system having a so-called image stabilization function, particularly when the movable lens group for image stabilization is reduced in size and weight and the movable lens group is moved, for example, in a direction orthogonal to the optical axis to exert an image stabilization effect. The present invention relates to a variable power optical system having a vibration isolation function for preventing deterioration of optical performance and improving the controllability of an actuator.

(Prior Art) When an image is captured from a moving object such as a car or an airplane in progress, vibration is transmitted to the image capturing system and the captured image is blurred.

Conventionally, an image stabilizing optical system having a function of preventing blurring of a photographed image has been disclosed in Japanese Patent Application Laid-Open No. 50-80147 and Japanese Patent Publication No. 56-2
No. 1133, Japanese Patent Application Laid-Open No. Sho 61-223819, and the like.

In JP-A-50-80147, when the angular magnification of the first variable power system is M ₁ and the angular magnification of the second variable power system is M ₂ in a zoom lens having two afocal variable power systems, M ₁ = 1-1
Magnification is changed in each variable power system so as to have a relationship of / M ₂ , and the second variable power system is spatially fixed to correct image blur to stabilize the image.

In Japanese Patent Publication No. 56-21133, the image is moved by moving some optical members in a direction that cancels the vibrational displacement of the image due to the vibration in accordance with the output signal from the detection means for detecting the vibration state of the optical device. We are trying to stabilize.

In JP-A-61-223819, in an image pickup system in which a refractive variable apex angle prism is arranged closest to the object side, an image is obtained by changing the apex angle of the refractive variable apex angle prism in response to the vibration of the image pickup system. The image is stabilized by deflecting it.

In addition, JP-B-56-34847 and JP-B-57-7414 dispose a spatially fixed optical member with respect to vibration in a part of the photographing system, and generate the optical member with respect to the vibration of the optical member. The still image is obtained on the imaging plane by deflecting the captured image by utilizing the prism action.

Also, a method of detecting a vibration of a photographing system using an acceleration sensor and obtaining a still image by vibrating a part of a lens group of the photographing system in a direction orthogonal to an optical axis according to a signal obtained at this time is also available. Is being done.

In general, a mechanism for obtaining a still image by eliminating vibration of a photographed image by vibrating a part of a lens group of the photographing system is required to have good responsiveness.

For this reason, the movable lens group is made as small and lightweight as possible, the inertial mass is reduced, the relationship between the image blur correction amount and the movable lens movement amount is simplified, and the calculation time for conversion is shortened. A shooting system is required.

Further, when the movable lens group is decentered, if many eccentric coma, eccentric astigmatism, eccentric field curvature, etc. occur, the image becomes blurred due to eccentric aberration when the image blur is corrected.
For example, if a large amount of eccentric distortion occurs, the amount of movement of the image on the optical axis and the amount of movement of the peripheral image differ. Therefore,
If the movable lens group is decentered in order to correct the image blur for the image on the optical axis, a phenomenon similar to the image blur will occur in the peripheral part, and it will cause a significant deterioration in the optical characteristics. .

As described above, in the image pickup system for image stabilization, particularly in the variable power optical system, when the movable lens group is moved in the direction orthogonal to the optical axis to be in the eccentric state, the eccentric aberration generation amount is small and the deterioration of the optical performance is small. Is required.

However, it is generally very difficult to obtain an imaging system that satisfies all of the above conditions. In particular, decentering a lens group having a part of refractive power of the imaging system greatly reduces the optical performance, resulting in a good image. There was a drawback that was not obtained.

(Problems to be Solved by the Invention) The present invention aims to reduce the size and weight of a movable lens when correcting a blur of an image by moving a part of lens groups of a variable power optical system in a direction orthogonal to an optical axis. , A variable power optical system having an anti-vibration function, which improves the responsiveness, and produces good optical performance with a small amount of the various decentering aberrations described above when the movable lens group is moved for parallel decentering. For the purpose of providing.

(Means for Solving the Problem) In a variable power optical system having a plurality of lens groups and changing the distance by changing at least one lens group interval among lens intervals formed by two adjacent lens groups A variable power position detecting means for detecting a variable power position of the variable power optical system,
At least one lens group among the lens groups on both sides with respect to the lens group spacing based on the variable power position signal from the variable power position detection means, a focus lens group for focusing, or a lens group adjacent to the focus lens group. Is to correct the blurring of the captured image by moving in the direction orthogonal to the optical axis.

(Embodiment) FIGS. 1 to 3 are schematic diagrams showing a method of correcting a blur of an image when the image blurs due to, for example, vibration in a variable power optical system according to the present invention. The variable power optical system shown in FIG. 1 has two lens groups, a first lens group 1 having a positive refractive power and a second lens group 2 having a negative refractive power, in order from the object side. FIG. 1 shows a so-called two-unit zoom lens that performs zooming and performs focusing by moving the first lens unit 1 on the optical axis. In addition, 5 is a light beam which forms an image at a point A on the image plane 3, and 4 is an optical axis of the variable power optical system. In the figure, (A) shows the optical arrangement at the wide-angle end, and (B) shows the optical arrangement at the telephoto end.

FIG. 1 is a schematic diagram of an optical system when there is no vibration and there is no image blurring. In the figure, since the light beam 5 has no vibration and no image blur, one point A on the image plane 3 at the wide-angle end and the telephoto end.
Image.

FIG. 2 is a schematic diagram of the optical system when vibration is transmitted to the variable power optical system and an image is blurred. In the same figure, for the sake of simplicity, the image formation state due to the blurring of the light flux is shown on the wide-angle side and the telephoto side when the entire variable-magnification optical system tilts forward around the point A and the image blurs.

That is, the light beam 5 to be focused on the point A is point B on the image plane 3 on the wide-angle side, and point C on the image plane 3 on the telephoto side.
Are imaged respectively.

Now, during film exposure, if the variable-magnification optical system tilts monotonously from the state shown in FIG. 2A to the state shown in FIG. The image to be formed as a point image at the wide angle side is line segment AB, and at the telephoto side is line segment
It is formed as a blurred line image of AC.

FIG. 3 is a schematic diagram when the blurring of the image in FIG. 2 is corrected. In the figure, the first lens group 1 is a movable lens group for image blur correction, and the image blur is corrected by decentering the optical axis 4 in a direction orthogonal to the optical axis 4. In the figure, 4a
Is the optical axis of the first lens group, and the optical axis 4 of the first lens group and the optical axis 4 of the second lens group, which were coaxial before blur correction, are parallel.

As shown in FIG. 2, the first lens group is decentered in parallel by a predetermined amount with respect to the image blur caused by the forward tilt of the entire variable power optical system, so that the point B at the wide angle end and the telephoto end as shown in FIG. Thus, the light beam which forms an image at the point C can be formed at the point A which is an original image forming point.

By thus decentering the first lens group in parallel, the image is stabilized. In the present embodiment, the blurring of the image can be similarly corrected even if the second lens group is decentered in parallel instead of the first lens group.

In the present embodiment, the parallel eccentric amount E of the movable lens unit for shake correction, which is the first lens unit, is E = −δy / S, where δy is the image blur amount and S is the eccentricity sensitivity of the movable lens unit. … (1). Here, the image blurring amount δy is obtained, for example, by adding a minus sign to the length of the line segment AB on the wide angle side and the length of the line segment AC on the telephoto side in FIG.

This is because the signs of E and δy are plus for the upper part of the optical axis and minus for the lower part.

The eccentric sensitivity S is a ratio of the amount of movement of the image point on the image plane to the amount of parallel eccentricity of the movable lens group.

In the present embodiment, the image blur amount δy is detected, and the parallel eccentric amount E of the movable lens group for image blur correction is calculated based on the decentering sensitivity S of the movable lens group peculiar to the variable power optical system. 1)
It is obtained from the formula.

The present invention is not limited to the two-group zoom lens shown in FIG. 1 to FIG. 3, but has a plurality of lens groups, and is a variable power optical system for varying the magnification by changing the interval of at least one of the lens groups. If it can be applied to any variable power optical system.

Next, in a general variable-magnification optical system, the relationship between the image blurring amount, the movable lens group for correction for correcting the blurring amount, and the moving amount will be shown. The blur amount can be detected in various forms by various detecting means, but for simplicity, all will be described in terms of the blur amount | δy |.

The movable lens group is the P-th group, and the parallel decentering amount of the P-th group is
E _P , the paraxial lateral magnification of the P-th group is B _P , and the paraxial lateral magnification of the entire lens system arranged closer to the image plane than the P-th group is β _q , E _P = − | δy | / { the _{(1-β P) · β} q} ...... (2). Here, (1-β _P ) · β _q is the eccentricity sensitivity. Since equation (2) is a general equation that does not consider aberration,
In practice, it is better to slightly change it in consideration of various aberrations.

In the variable power optical system, β _P , β _{q and the} like in the equation (2) change depending on the position of the movable lens group for image blur correction in the optical system. As a result, | δy | and (1-β _P ) ・Since the ratio of β _q changes, it is preferable to provide a variable power position detecting means for detecting the variable power position for correction.

In the present embodiment, in order to satisfactorily correct the image blurring while reducing the occurrence of eccentric aberration, it is preferable to change to satisfy | (1−β _P ) · β _q |> 0.1 (3) It is better to construct a double optical system.

If the conditional expression (3) is not satisfied, the moving amount of the movable lens unit for image blur correction increases and the lens outer diameter of the movable lens unit increases, which is not preferable.

Generally, if an attempt is made to correct image blur by decentering a part of lens groups of an optical system in parallel, decentration aberrations occur and the imaging performance deteriorates.

Therefore, next, in an arbitrary refractive power arrangement, when the movable lens group is moved in the direction orthogonal to the optical axis to correct the blurring of the image, the occurrence of decentering aberration is considered from an aberrational standpoint.
Explained based on the method presented by Matsui at the 23rd Lecture on Applied Physics (1962).

The aberration amount Δ'Y of the entire system when a part of the lens group of the photographing lens is decentered by parallel E is the aberration amount ΔY before decentering and the eccentric aberration amount ΔY (E) generated by decentering as shown in equation (a).
Will be the sum of Here, the eccentric aberration ΔY (E) is the first-order eccentric coma aberration (II E), the first-order eccentric astigmatism (III E), and the first-order eccentric field curvature (PE) as shown in the equation (b). 1st-order eccentric distortion aberration (VE1), 1st-order eccentric distortion-added aberration (VE2),
The secondary decentering astigmatism (III E ^2), a secondary decentering field plane distortion (PE ^2), 2-order decentering distortion (VE ² 1), 2-order decentering distortion shark aberration (VE ² 2) , And the primary origin movement (Δ
E) It is represented by the ^third origin movement (ΔE ³ ). Also (c)
The aberrations from (II E) to (ΔE ³ ) in the equations (m) are composed of two lens groups, a fixed lens group and a movable lens group, in order from the object side. The aberration coefficient of the movable lens group when the incident angle and the exit angle of the light ray to the movable lens group are α _P and ▲ ▼, respectively.
It is expressed using I _P , II _P , III _P , P _P , and V _P.

Δ'Y = ΔY + ΔY (E) (a) _{(PE) = - α P P} P (e) (PE ² ) = α _P ² P _P (i) _{^{(VE 2 2) = α P}} ▲ ▼ P P (k) (ΔE) = - 2 (α 'P -α P) (l) From the above equation, in order to reduce the occurrence of decentration aberration, the various aberration coefficients I _P , II _P , III _P , P _P , V _P of the movable lens group are set to small values, or the equations (b) to (k It is necessary to set the various aberration coefficients in a well-balanced manner so as to cancel each other out, as shown in the equation). In the movable lens group, it is necessary to satisfactorily correct astigmatism and distortion in addition to spherical aberration, coma and Petzval sum.

Generally, in order to correct off-axis aberrations as well as on-axis aberrations in the movable lens group in a well-balanced manner, the height h of on-axis rays and the height of principal rays of off-axis rays in the movable lens groups have different values. It becomes necessary to configure the lens system as described above.

Therefore, in the present embodiment, the movable lens group is composed of a plurality of lenses as shown in the numerical examples described later, and the movable lens group in the variable power optical system is set as described above to decenter the movable lens group. The amount of eccentric aberration generated when it is set is reduced.

In general, in a variable power optical system, a lens group to be moved at the time of zooming or focusing, or a lens group adjacent to the lens group has a relatively good aberration correction in the lens group, or balances the aberration in the vicinity thereof. In many cases, there is a lens group that performs good correction. Also, when considering a composite system of the lens group and an adjacent lens group, each aberration is often corrected well.

Therefore, in this embodiment, as described above, the variable power lens group that is moved during zooming, or at least one of the lens groups on both sides of the variable power lens group, or the focus lens group that is moved during focusing, or At least one lens group of the focus lens group is used as a movable lens group for image blur correction, and is moved in the direction orthogonal to the optical axis, so that the amount of eccentric aberration is reduced and the image blur is well corrected. There is.

In particular, a variable power optical system is achieved which prevents the decentering aberration coefficients of the above equations (C) to (g) from increasing, corrects the blurring of a predetermined image, and prevents deterioration of the optical performance.

FIG. 4 is a lens sectional view of a variable power optical system of a numerical example according to the present invention. In the figure, (A) is the wide-angle end, and (B) is the telephoto end. I is a first lens group having a negative refractive power, II is a second lens group having a positive refractive power, and III is a third lens group having a negative refractive power. The second and third lens units II and III are moved as indicated by arrows to change the magnification from the wide-angle end to the telephoto end.

In this embodiment, image blurring can be corrected by decentering any one of the first, second and third lens groups I, II and III.

FIGS. 5A and 5B are lateral aberration diagrams of the numerical example at the wide-angle end and the telephoto end. Y ₀ is the object height in the figure, y ₁ denotes the image height.

Next, in Numerical Examples, the entire lens system is tilted forward by 9 minutes with respect to the film surface as an example, and the first, second, and third lens groups for correcting the blurring of the image at this time are independently displayed. Lateral aberration diagrams when parallel eccentricity is given by the value shown in −1 are shown in FIGS. 6, 7, and 8 as reference examples. In the figure, (A) is the wide-angle end and (B) is the telephoto end.

Further, Tables 2 to 4 show the image forming positions of the chief ray on the film surface at each object height in order to show the correction state of the eccentric distortion when the image blur is corrected by each lens group.

According to the present embodiment, as shown in FIGS. 6, 7, 8 and Table-2, Table-3, and Table-4, the eccentric distortion can be achieved while reducing the amount of eccentric aberration due to the parallel decentering of the movable lens group. Corrected well,
Moreover, a variable power optical system having a high optical performance in which a predetermined image blur is corrected is achieved.

In the above embodiments, the case where the movable lens group is decentered in parallel to correct the blurring of the image has been described, but the same object of the present invention is obtained even if the lens is rotationally decentered or both are performed at the same time. Can be achieved.

The blur caused by the vibration of the variable magnification optical system is not limited to the center of the film, and the present invention can be suitably applied to any point of blur. The number of lens groups for image blur correction is not limited to one, but two or more lens groups may be independently decentered. The image blur correction may be performed only on the telephoto side where blurring is likely to occur, instead of uniformly performing it over the entire zoom range.

Next, numerical examples of the present invention will be shown. In the numerical example
Ri is the radius of curvature of the i-th lens surface in order from the object side, Di
Is the i-th lens thickness and air gap from the object side, Ni and ν
r is the refractive index and Abbe number of the glass of the i-th lens in order from the object side.

The aspherical shape has an X axis along the optical axis and H along the direction perpendicular to the optical axis.
Axis, light traveling direction is positive, R is paraxial radius of curvature, A, B, C, D,
When E is each aspherical coefficient It is expressed by

Numerical examples Aspherical coefficient of the second surface B = 5.319 × 10 ⁻⁶ C = 1.919 × 10 ⁸ D = −4.745 × 10 ⁻¹³ E = 1.304 × 10 ⁻¹³ Decentering Sensitivity of Each Lens Group (1-β _P ) · β _q Table (Effect of the Invention) According to the present invention, among the lens groups constituting the variable power optical system, at least one lens group satisfying the above-mentioned conditions is decentered to correct the blurring of an image and to be decentered due to decentering. It is possible to achieve a variable power optical system having an image stabilizing function capable of maintaining high optical performance by suppressing the amount of aberration as much as possible.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 to 3 are schematic diagrams of an embodiment of a method for correcting image blur in a variable power optical system of the present invention, and FIG. 4 is a numerical value of the variable power optical system of the present invention. Sectional view of lens of Example, 5 (A),
FIG. 6B is an aberration diagram of a numerical example of the present invention, and FIGS. 6 to 8 are aberration diagrams when each lens group is decentered in the numerical example of the present invention. In the figure, I, II, and III are the first, second, and third lens groups, respectively, y ₀ is the object height, and y ₁ is the image height.

Claims (1)

(57) [Claims] 1. A plurality of lens groups, at least one of which is a lens interval composed of two adjacent lens groups.
In a variable power optical system which performs variable power by changing the distance between two lens groups, a variable power position detecting means for detecting a variable power position of the variable power optical system is provided, and a variable power position signal from the variable power position detecting means is provided. Based on the distance between the lens groups, at least one of the lens groups on both sides, a focus lens group for focusing, or a lens group adjacent to the focus lens group is moved in a direction orthogonal to the optical axis for photographing. A variable-magnification optical system having an image stabilization function characterized by correcting image blur.