JP2621280B2 - Variable power 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 anti-vibration function, particularly, a movable lens group for anti-vibration, for example, is moved in a direction perpendicular to the optical axis to prevent a decrease in optical performance when exerting an anti-vibration effect. The present invention relates to a variable power optical system having an anti-vibration function.

(Prior Art) When an image is taken from a moving object such as a car or an aircraft in progress, vibration is transmitted to an image taking system, and a blurred image occurs.

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.

Japanese Patent Application Laid-Open No. 50-80147 discloses a zoom lens having two afocal variable power systems in which the first variable power system has an angular magnification of M ₁ and the second variable power system has an angular magnification of M _2. M ₁ = 1−
In each zooming system, zooming is performed so as to have a relationship of 1 / M ₂ , and the second zooming system is spatially fixed to correct image blur and stabilize the image.

In Japanese Patent Publication No. 56-21133, according to an output signal from a detecting means for detecting a vibration state of an optical device, some optical members are moved in a direction to cancel the vibrational displacement of the image due to vibration. We are stabilizing.

Japanese Patent Application Laid-Open No. 61-223819 discloses a photographing system in which a refraction type variable apex angle prism is disposed closest to the subject, and an image is formed by changing the apex angle of the refraction type apex angle prism in accordance with the vibration of the imaging system. The image is stabilized by deflection.

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 vibrating a part of the lens group of the photographing system to reduce the blur of the photographed image simplifies the relationship between the amount of correction of the image blur and the amount of movement of the movable lens, and provides a mechanism for conversion. There is a demand for a photographing system having a simple configuration for shortening the calculation time.

Also, when the movable lens group is decentered, if the eccentric coma, the eccentric astigmatism, and the eccentric curvature of field occur frequently, the image is blurred due to the 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. Because of this,
If the movable lens group is decentered in order to correct the image blur on the image on the optical axis, a phenomenon similar to the image blur occurs in the peripheral portion, which causes a remarkable decrease in optical characteristics. .

As described above, when the movable lens group is moved in a direction perpendicular to the optical axis to be in an eccentric state, the amount of eccentric aberration is small, the optical performance is not reduced, and the imaging system for image stabilization, especially in the variable power optical system, A simple mechanism 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) In the present invention, when a part of the lens units of the variable power optical system is moved in a direction perpendicular to the optical axis to correct image blurring, the mechanism of the movable lens group is simplified. For example, the present invention provides a variable power optical system having an image stabilizing function that can obtain good optical performance with a small amount of the above-described various eccentric aberrations when the movable lens group is moved and parallel decentered, for example. Aim.

(Means for solving the problem) A plurality of lens groups, of which the distance between the first lens group and the second lens group counted from the object side changes at least when zooming or focusing. Where the focal length of the first lens group is f1 and the focal length of the entire system at the telephoto end is fT, 0.2 <| f1 / fT | <5 (A1) The condition is satisfied, and the blur of the captured image caused by the tilt when the zoom optical system is tilted as a whole is detected by the blur detecting means, and the driving means responds to the output signal from the blur detecting means to detect the blur. The optical constants of the plurality of lens groups are set such that blurring of the photographed image is corrected when the first lens group is decentered in parallel by about | f1 · ε |.

(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. Reference numeral 5 denotes a light flux that forms an image at a point A on the image forming surface 3, and reference numeral 4 denotes 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, on the wide-angle side and the telephoto side, for the sake of simplicity, the image forming state due to the blurring of the light beam when the entire zoom optical system is tilted forward by the angle ε around the point A and the image blurs is shown. I have.

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.

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 a correction is made to the blur of the image of FIG. In FIG. 1, the first lens group 1 is a movable lens group for blur correction, and is decentered parallel to the optical axis 4 in a direction orthogonal to the optical axis 4 to correct image blur. 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.

The image stabilization is achieved by decentering the first lens group in parallel as described above.

In this embodiment, the parallel eccentricity E of the movable lens group for shake correction, which is the first lens group, is E = -δy / S where δy is the image blur amount and S is the eccentric sensitivity of the movable lens group. (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 above the optical axis and minus below.

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 this embodiment, the blur amount δy of the image is detected by the blur detecting means inside the camera, and the movable lens group for image blur correction is based on the eccentric sensitivity S of the movable lens group unique to the variable power optical system. Is obtained from equation (1). The drive unit decenters the movable lens group by a predetermined amount to correct image blur.

Note that the present invention is not limited to the two-unit zoom lens shown in FIGS. 1 to 3, and has a plurality of lens units, of which the magnification is changed by changing the distance between the first and second lens units. Alternatively, the present invention can be applied to any zoom optical system as long as it is a zoom optical system that performs focusing.

For example, as compared to a two-unit zoom lens in which a positive refractive power lens group shown in FIGS. 1 to 3 precedes, the first lens group has a negative refractive power, the second lens group has a positive refractive power, A two-unit zoom lens that performs zooming by changing the distance between both lens units and performs focusing by the first lens unit, or negative, positive, and negative refractive power or positive, negative, and positive refractive power in order from the object side The first, second, and third lens groups have three lens groups. At least two of these lens groups are moved to perform zooming. , Negative, negative, and positive refractive power, or positive,
It has four lens groups, negative, positive, and positive refractive power, or positive, negative, positive, and negative refractive power. The present invention can be applied to a four-unit zoom lens or the like that performs zooming by moving at least two lens units so that the distance between the first and second lens units changes.

Next, the relationship between the blur amount of an image and the movement amount of a movable lens group for correction for correcting the blur amount in a general zoom optical system will be described. The shake amount is detected in various forms by various shake detection means, but for the sake of simplicity, all the shake amounts will be described in terms of | δy |.

Now, when the entire variable power optical system is tilted by an angle ε as shown in FIG. 2, the blur amount δy of the image on the image plane is given by: δy = f · ε where the focal length of the entire variable power optical system is f. ... (2) At this time, assuming that the focal length of the first lens group is f1, the eccentric sensitivity S1 of the first lens group is S1 = f / f1 (3). Since S in equation (1) and S1 in equation (3) can be treated as the same, S = S1 and (2),
From equation (3), equation (1) becomes E = −f1 · ε (4).

According to equation (4), the amount of parallel eccentricity E of the first lens group when correcting the image blur by parallel eccentricity of the first lens group in the variable power optical system is independent of the variable power position of the variable power optical system. Becomes In other words, when the camera is tilted by the angle ε and parallel eccentric by | f1 · ε |, the blur of the image can be corrected. As described above, in this embodiment, the parallel eccentricity E can be obtained from the focal length f1 of the first lens group and the tilt angle ε.

However, in practice, it is necessary to stabilize an image by various object distances and various aberration occurrence states. Therefore (4)
It is preferable to treat the expression approximately when effective stabilization of the image is performed.

In this embodiment, when the variable power optical system as a whole is tilted by an angle ε and the captured image is blurred, the first lens group is set to | f1
The optical constants of the plurality of lens groups are set so that blurring of the photographed image is corrected when the eccentricity is approximately ε |.

Further, in this embodiment, the refractive power of the first lens group is set as in the above-described conditional expression (A1) to correct image blurring by the first lens group, and the first lens group is decentered in parallel. The optical performance is prevented from deteriorating.

When the refractive power of the first lens unit is increased beyond the lower limit of conditional expression (A1), the eccentric sensitivity increases, and the amount of movement in the direction orthogonal to the optical axis for correcting image blur is reduced. can do. However, the eccentricity precision becomes severe accompanying this, and the amount of focus movement particularly for zooming on the optical axis becomes extremely large, and a very high-precision lens holding mechanism is required. Further, the first lens group is used for various aberration corrections. It is necessary to increase the number of lenses, and it is not preferable.

If the refractive power of the first lens unit is weakened by exceeding the upper limit of conditional expression (A1), the first
The lens group must be moved a lot in the direction perpendicular to the optical axis, which is not good because the effective diameter of the first lens group increases and the size increases.

Generally, when an attempt is made to correct image blurring by decentering some lens groups of the optical system in parallel, the imaging performance is reduced due to the occurrence of eccentric aberration.

Then, from the viewpoint of aberration theory, the occurrence of eccentric aberration when the movable lens group is moved in a direction perpendicular to the optical axis in an arbitrary refractive power arrangement to correct image blurring,
Explained based on the method presented by Matsui at the 23rd Lecture on Applied Physics (1962).

When the first lens group of the variable power optical system is decentered in parallel by E, the aberration amount ΔY1 of the whole system is equal to the aberration amount ΔY before decentering and the eccentric aberration amount ΔY (E) generated by eccentricity as shown in equation (a). The sum of Here, the aberration amount ΔY includes spherical aberration (I), coma aberration (II), astigmatism (III), Petzval sum (P),
It is represented by distortion (Y).

The eccentric aberration ΔY (E) is expressed by the first-order eccentric coma (II E) and the first-order eccentric astigmatism (III) as shown in the equation (C).
E) First-order eccentric field curvature (PE), first-order eccentric distortion (VE1), first-order eccentricity additive aberration (VE2), and first-order origin movement (ΔE).

Further, the aberrations from (ΔE) to (VE2) in the equations (d) to (i) are caused by setting the incident angle of the light beam to the first lens group to α _p , in a variable power optical system for decentering the first lens group in parallel. _{where p} is the aberration coefficient of the first lens group, I _p , II _p , III _p , P _p , and V _p ;
Similarly, when the lens units arranged on the image plane side of the first lens unit as a whole are the q-th lens unit, the aberration coefficients are calculated using I _q , II _q , III _q , P _q , and V _q. Is represented.

ΔY1 = ΔY + ΔY (E) (a) (ΔE) = − 2 (α ′ _p −α _p ) = − 2 h _p φ _p (d) (II E) = α ′ _p II _q −α _p (II _p + II _q ) − ′ _p I _q + _p ( I _p + I _q ) = h _p φ _p II _q −α _p II _p − ( _p φ _p I _{q −p} I _p (e) (III E) = α ′ _p III _q −α _p (III _p + III _q ) _-'P II _q + _p (II _p + II _q ) = h _p φ _p III _q- α _p III _p- ( _p φ _p II _q - _p II _p (f) (PE) = α' _p P _q- α _{p (P p + P q)} = h p φ p P q -α p P p (g) (VE1) = α 'p V q -α p (V p + V q) -' p III q + p (III p + III _q ) = h _p φ _p V _q −α _p V _p − ( _p φ _p III _q − _p III _p (h) (VE2) = ′ _p P _{q −p} (P _p + P _q ) = _p φ _p P _q − _p P _p (i) From the above equation, to reduce the occurrence of eccentric aberration, the first
The various aberration coefficients I _p , II _p , III _p , P _p , and V _p of the lens group are set to small values, or the various aberration coefficients are canceled out as shown in the equations (a) to (i). It is necessary to set the balance well. In the first lens group, it is necessary to satisfactorily correct astigmatism and distortion in addition to spherical aberration, coma and Petzval sum.

In general, to correct off-axis aberrations as well as on-axis aberrations in the first lens group in a well-balanced manner, the height h of the on-axis rays and the height of the principal ray of the off-axis rays in the first lens group are different from each other. It is necessary to configure the lens system so that

For this reason, in the present embodiment, the first lens group is composed of a plurality of lenses as shown in numerical examples to be described later, and the first lens group in the variable power optical system is set as described above. The amount of eccentric aberration generated when the group is decentered 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 combination system of the lens group and an adjacent lens group, each aberration is often well corrected.

For this reason, in the present embodiment, as described above, the first lens group to be moved is used as a movable lens group for image blur correction and is moved in a direction perpendicular to the optical axis at the time of zooming or focusing, thereby causing eccentric aberration. The image blur is satisfactorily corrected while reducing the amount.

This achieves a variable power optical system that prevents an increase in the eccentric aberration coefficients of the above-described equations (e) to (i), corrects blurring of a predetermined image, and prevents a decrease in optical performance. .

In particular, in the numerical examples to be described later, the first lens group is integrally moved in a direction orthogonal to the optical axis to achieve a variable power optical system that satisfactorily corrects image blurring and generates very little eccentric aberration. I have.

FIG. 4 is a lens sectional view of a zoom optical system according to a numerical example of 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, the first lens group I is decentered in parallel to correct image blur.

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 a numerical example, the entire lens system is tilted forward by 9 minutes with the film surface as an example (ε = −0.002617).
FIG. 6 shows, as a reference example, a lateral aberration diagram when the parallel decentering is performed by the value shown in FIG. In the figure, (A) is the wide-angle end, and (B) is the telephoto end.

Table 2 shows the image formation position of the principal 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 the first lens group.

According to the present embodiment, as shown in FIG. 6 and Table 2, the eccentric distortion can be satisfactorily corrected while the amount of eccentric aberration is reduced by the parallel eccentricity of the first lens group, and the blur of a predetermined image can be reduced. A variable power optical system having a corrected high optical performance is achieved.

In the above embodiment, the case where the image blur is corrected by decentering the first lens group in parallel has been described. However, the object of the present invention can be similarly performed even when the rotation is decentered, or when both are performed simultaneously. 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 image blur correction may be performed only on the telephoto side where blur is likely to occur, instead of performing the correction uniformly over the entire zoom range.

Further, the image blur may be corrected only at a predetermined object distance such as a short-distance object.

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

The aspheric surface has an X-axis in the optical axis direction and H in the direction perpendicular to the optical axis.
R and paraxial radius of curvature, A, B, C, D,
When E is each aspheric coefficient It is represented by the following equation.

(Effects of the Invention) According to the present invention, among the lens groups constituting the variable power optical system, the first lens group that satisfies the above-mentioned condition is decentered to correct image blurring and to perform eccentric aberration accompanying eccentricity. And a variable power optical system having an anti-vibration function capable of maintaining high optical performance while minimizing the amount of generation of light.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 to 3 are schematic views of an embodiment of a method for correcting image blurring in a variable power optical system according to the present invention, and FIG. 4 is numerical values of the variable power optical system according to the present invention. FIGS. 5A and 5B are aberration diagrams of a numerical example of the present invention, and FIGS. 6A and 6B are first lens groups of the numerical examples of the present invention. FIG. 9 is an aberration diagram when is decentered. In the figure, I, II, III each first, second, third lens group, y ₀ is the object height, y ₁ denotes the image height.

Claims (1)

(57) [Claims] 1. A zooming system having a plurality of lens units, wherein the distance between the first lens unit and the second lens unit counted from the object side changes at least when zooming or when focusing. An optical system, wherein the focal length of the first lens group is f
1. Assuming that the focal length of the entire system at the telephoto end is fT, the image satisfies the condition of 0.2 <| f1 / fT | <5. When the first lens group is decentered in parallel by about | f1 · ε | by drive means in accordance with an output signal from the shake detection means, the shake of the photographed image is corrected. A variable power optical system having an image stabilizing function, wherein optical constants of the plurality of lens groups are set as described above.