JPH06160778A - Variable power optical system provided with vibration-proof function - Google Patents

Abstract

PURPOSE:To obtain a variable power optical system provided with a vibration- proof function capable of stabilizing a photographed image by optically correcting the blurring of the photographed image at the time when the variable power optical system vibrates and obtaining a still picture. CONSTITUTION:This variable power optical system is provided with a 1st group 1 fixed in the case of varying power and focusing nearer to an object side than a variable power part. The 1st group 1 is turned centering around a point on an optical axis separated from a rear side principal point to an image surface side by almost focal distance and spatially fixed with respect to the tilt of the variable power optical system, so that the blurring of the photographed image is corrected at the time when the variable power optical system vibrates, and focusing is performed to a finite distance object by moving at least one lens group out of the lens groups provided nearer to the image surface side than the variable power part on the optical axis.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable power optical system having a vibration-proof function, and more particularly, by rotating a part of a lens group of the variable power optical system with a point on the optical axis as a center point. Anti-vibration function suitable for photographic cameras, video cameras, etc. that stabilizes the captured image by optically correcting the blur of the captured image when the variable magnification optical system vibrates (tilts) to obtain a still image. The present invention relates to a variable power optical system having.

[0002]

2. Description of the Related 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, various anti-vibration optical systems having a function of preventing blur of a photographed image have been proposed.

For example, in Japanese Examined Patent Publication No. 56-21133, some optical members are moved in a direction of canceling the vibrational displacement of an image due to vibration in accordance with an output signal from a detection means for detecting a vibration state in an optical device. By doing so, the image is stabilized.

According to Japanese Patent Laid-Open No. 61-223819, in a photographing system in which a refracting variable apex angle prism is arranged closest to the subject, the apex angle of the refracting variable apex prism is changed in response to the vibration of the photographing system. The image is deflected to stabilize the image.

Japanese Patent Publication No. 56-34847, Japanese Patent Publication No. 5
In Japanese Patent Laid-Open No. 7-7414, an optical member that is spatially fixed against vibration is arranged in a part of a photographing system, and a prism image generated by the vibration of this optical member is used to deflect a photographed image. A still image is obtained on the image plane.

Further, in Japanese Patent Laid-Open No. 50-137555, a lens unit on the object side in a telephoto lens is rotated about a point on the optical axis that is away from the principal point position by the focal length of the lens unit. As a result, blurring of a captured image when the telephoto lens is tilted is corrected.

In Japanese Unexamined Patent Publication No. 63-115126, vibration of the photographing system is detected by using an acceleration sensor or the like, and a part of the lens group of the photographing system is orthogonal to the optical axis according to a signal obtained at this time. There is also a method of obtaining a still image by vibrating the camera.

In addition to this, in Japanese Patent Laid-Open No. 2-238429 and US Pat. No. 2,959,088, the first and second refractive powers are negative and positive.
A lens system composed of two lens groups, a first lens group and a second lens group, is arranged in front of the photographing system, and when the photographing system vibrates, the second lens group is used as a vibration-proof operation lens group, and a gimbal is supported at its focal position. We propose a vibration-proof optical system using the inertial pendulum method.

[0010]

Generally, driving means such as an actuator is used to decenter the lens group, or the prism apex angle of the variable apex angle prism is changed to deflect a photographed image to obtain a still image. was when there is a vibration of a high frequency of several 10H _Z is a vibration proof optical system of the active type, for example can not follow such a frequency characteristic of the control system characteristics and sensors, that very difficult to correct image blur There is a problem.

On the other hand, the above-mentioned Japanese Unexamined Patent Publication No. 2-23842.
Inertia in which two lens groups, a negative first lens group and a positive second lens group, are arranged in front of the photographing system and a second lens group is supported by a gimbal, as proposed in Japanese Patent Publication No. 9 and US Pat. No. 2,959,088. The anti-vibration optical system using the pendulum system has a feature that relatively good anti-vibration characteristics can be obtained even when there is high-frequency vibration as compared with the above-mentioned active-type anti-vibration optical system.

However, since a lens group dedicated to image stabilization is arranged in front of the photographing system and the lens group is vibrated to eliminate blurring of a photographed image to obtain a still image, the entire lens system becomes large. There was a problem.

On the other hand, in order to prevent the deterioration of optical properties during image stabilization, some lenses of the photographing system are decentered parallel to the optical axis to perform image stabilization, and the correction angle is increased. There is a problem that it is very difficult to sufficiently correct the eccentric aberration at the time of image stabilization, and a large eccentric magnification chromatic aberration occurs at the time of image stabilization in the optical system using the variable apex angle prism.

According to the present invention, a lens group constituting a part of a variable power optical system is rotated about a point on the optical axis as a rotation center, and a photographed image when the variable power optical system vibrates (tilts). By compensating for blurring, the overall size of the device is reduced and the amount of eccentricity generated when the lens group is decentered is suppressed to a small amount, and eccentric aberration is satisfactorily corrected and high optical performance is maintained. An object is to provide a variable power optical system having a function.

[0015]

A variable-magnification optical system having a vibration-proof function according to the present invention is a variable-magnification optical system in which a fixed first lens unit is provided on the object side of a variable-magnification section for zooming and focusing. The first group is rotated about a point on the optical axis, which is separated from the principal point on the rear side to the image plane side by the approximate focal length thereof, and is a space for tilting of the variable power optical system. Is fixed to correct the blur of the captured image when the variable magnification optical system vibrates, and at least one lens group of the lens groups provided on the image plane side of the variable magnification section is on the optical axis. It is characterized in that the finite distance object is focused by moving it.

Further, the variable power optical system having the image stabilizing function of the present invention comprises a first lens unit having a positive refractive power which is fixed during variable power and focusing in order from the object side, and a negative refractive power having a variable power function. A second lens group of a force, and at least one lens group that is fixed or moves at the time of zooming, and the first lens group is on the optical axis separated from the rear principal point to the image plane side by the approximate focal length. Is rotated about the point of (1) to be spatially fixed with respect to the tilt of the variable power optical system to correct the blurring of the photographed image when the variable power optical system vibrates, and the second group. It is characterized in that at least one of the lens groups provided closer to the image plane is moved on the optical axis to focus an object at a finite distance.

Further, in the variable power optical system having the image stabilizing function of the present invention, the first lens unit having a positive refractive power which is fixed at the time of zooming and focusing in order from the object side, and the negative refractive power having the variable power function. A fourth lens unit having a second lens unit having a positive power, a third lens unit having a positive refractive power, and a fourth lens unit having a positive refractive power, and an image plane that varies with zooming is provided in the third lens unit and the fourth lens unit. Is corrected by moving either one of them on the optical axis and focusing is performed, and the first group is centered on a point on the optical axis that is separated from the rear principal point to the image plane side by the approximate focal length. It is characterized in that it is rotated and spatially fixed with respect to the tilt of the variable power optical system to correct the blurring of a photographed image when the variable power optical system vibrates.

[0018]

FIG. 1 is a schematic diagram showing the paraxial refractive power arrangement of an optical system of Example 1 of the present invention, and FIG. 2 is a lens sectional view of Numerical Example 1 of the present invention.

5, FIG. 6, FIG. 7, FIG. 8 and FIG. 9 are the wide-angle end, the middle, the telephoto end, the telephoto end without eccentricity, and the telephoto in which the blur angle of 2 degrees is corrected in the numerical embodiment 1 of the present invention. Aberration diagrams at the ends, and FIGS. 10, 11, 12, 13, and 14 are the wide-angle end, the middle, the telephoto end, and the telephoto end without decentering according to Numerical Embodiment 2 of the present invention.
FIG. 1 is an aberration diagram at the telephoto end in which the blur angle of 2 degrees is corrected.
5, FIG. 16, FIG. 17, FIG. 18, and FIG. 19 are aberration diagrams of the numerical example 3 of the present invention at the wide-angle end, the middle, the telephoto end, the telephoto end without eccentricity, and the telephoto end in which the blur angle of 2 degrees is corrected. Is.

In the figure, reference numeral 1 is a first lens unit having a positive refractive power which is fixed at the time of zooming and focusing, and is a point on the optical axis which is separated from the rear principal point to the image plane side by a substantial focal length thereof. By rotating about 5 as a center, the blur (image blur) of the captured image when the variable power optical system is tilted is corrected. That is, the first group 1 is configured to maintain a stationary state with respect to the space even when the variable power optical system (entire camera) tilts.

A second lens unit 2 having a negative refractive power, which moves along the optical axis direction for zooming, has a zooming unit. The second lens group 2 is moved, for example, as indicated by an arrow a to change the magnification from the wide-angle end to the telephoto end.

Reference numeral 3 denotes a third lens unit having a fixed positive refractive power, and 4 a positive lens having both an image surface correction function for correcting an image surface that fluctuates with zooming and a focusing function for focusing. It is the 4th group of the refractive power of.

In this embodiment, when zooming from the wide-angle end to the telephoto end with the fourth lens group 4 focused on an object at infinity or a near object, a curve b having a convex surface on the object side.
It is moved on the optical axis as shown.

Numeral 10 is a lens group which is fixed during zooming and image stabilization, and also serves as, for example, a protective glass having a paraxial refractive power of substantially zero. The image-side lens surface of the lens group 10 is formed of an aspherical surface having a shape in which the positive refracting power becomes stronger from the central portion toward the peripheral portion.

In the present embodiment, 9 is a counterweight, which is provided at one end of a holding member 8 for holding the first group 1, and the first group 1 serves as a center of the zooming optical system. The weight of the first group 1 when rotating according to the inclination is balanced.

In this embodiment, for example, the first group 1 is spatially fixed by the counterweight 9 when the variable power optical system is tilted. In other words, I try to keep my initial posture.

Next, the principle of the optical system according to the present invention, which is performed during image stabilization, will be described with reference to FIG. In FIG.
The same elements as those shown in are given the same reference numerals. In the figure, when the variable magnification optical system is tilted, the first group (correction lens group) 1 is relatively rotated about the point 5 on the optical axis by, for example, an angle θ. .

Now, let f1 be the focal length of the first lens unit 1 and f be the focal length of the entire lens system. If camera shake of the angle ω (tilt of the variable-magnification optical system) occurs at this time, the amount of movement Δ of the captured image (object image) on the image plane is represented by Δ = f · cosω ····· (1) Be done.

At this time, the eccentricity sensitivity of the first group 1 (the ratio of the eccentricity of the first group 1 to the amount of movement of the photographed image) h _S is expressed by h _S = f / f ₁ (2) Be done. Therefore, the amount of eccentricity of the first group 1 (the amount of eccentricity in the direction perpendicular to the optical axis) necessary for correcting the camera shake is Δ = f · cosω = (f / F ₁ ) · E (3)

For example, if the distance from the principal point position of the first lens unit 1 to the center of rotation on the image plane side is a, and the correction angle required for the first lens unit 1 at this time is angle θ, then E = a · tan θ. It becomes (4). From the above equations (3) and (4), f · tan ω = (f / f ₁ ) a · tan θ ∴f ₁ · tan ω = a · tan θ (5) where a = f ₁ ‥‥‥‥‥‥ If (6) is set, then ω = θ, and the camera shake angle ω and the rotation angle θ required for the first group 1
Match.

Therefore, in the present embodiment, based on the above-described principle, the first group 1 is spatially stationary with a position distant from the principal point position of the first group 1 by the focal length thereof as a fulcrum. The camera is supported in such a state that the camera shake is prevented.

That is, by rotating the first group 1 by a predetermined amount around the point 5 on the optical axis for image stabilization, a lens group for variable image stabilization and a variable lens group are provided as compared with the conventional image stabilization optical system. Anti-vibration is performed without newly adding an optical member such as a vertical angle prism.

In the present embodiment, a fixed lens group 10 is provided on the object side of the first lens group 1 for correcting decentering aberration during image stabilization so that good optical performance is maintained during image stabilization. .

The lens surface on the image side of the fixed lens group 10 is composed of an aspherical surface formed so that the positive refractive power becomes stronger from the central part of the lens toward the peripheral part as described above. The eccentric aberration generated during image stabilization, especially the eccentric coma aberration on the telephoto side, is well corrected.

The fixed lens group 10 also has a function as a protective glass so that an external force is not directly applied to the variable magnification optical system from the outside except for vibration isolation.

In FIG. 2, SSP is a fixed diaphragm,
It is arranged between the first group 1 and the second group 2. Aperture SSP
Suppresses a change in the image plane illuminance ratio around the screen during image stabilization so that an appropriate light amount distribution can be obtained on the image pickup surface even during image stabilization.

In the present embodiment, it is preferable to satisfy the following conditions in order to maintain good optical performance while reducing the size of the entire lens system.

That is, when the focal length of the first lens unit 1 is f ₁ and the focal length of the entire system in the telescope is fT, 0.45 <| f ₁ /fT|<0.65 (a) It is to set each element so that the condition is satisfied.

Conditional expression (a) is for appropriately setting the refractive power of the first lens unit 1 and for reducing the amount of eccentric aberration when the first lens unit 1 is decentered mainly for image stabilization. Is.

If the upper limit of conditional expression (a) is exceeded and the refracting power of the first lens unit 1 becomes too weak, the decentering amount of the first lens unit 1 will increase during image stabilization, and as a result, the center of the lens of the first lens unit 1 will increase. From the optical axis to the optical axis becomes too large, the lens diameter of the first unit 1 increases, which is not good.

If the lower limit of conditional expression (a) is exceeded and the refractive power of the first lens unit 1 becomes too strong, the amount of rotation during image stabilization will decrease, but the amount of eccentric aberration will increase, which is not desirable. .

In the present embodiment, the first group (correction lens group) 1 is spatially fixed against the tilt of the variable power optical system to perform image stabilization, but for example in an actual device such as a video camera. When applied and panned, part of the lens approaches the edge of the camera.

Therefore, in the present embodiment, by controlling the variable power optical system by applying a force from the outside by the control means,
I try to get close to the edge of the camera and not hit it.

Further, in the anti-vibration optical system to which the inertial pendulum is applied as in the present invention, for example, when the anti-vibration optical system becomes smaller and lighter, the anti-vibration suppression rate against low frequency vibration due to the influence of friction or the like. May decrease.

In such a case, as described above, the control means externally applies a force to control the vibration-proof optical system, thereby effectively performing the vibration-proof.

FIG. 4 is a schematic diagram showing the paraxial refractive power arrangement of the optical system of Example 2 of the present invention. In the figure, the same elements as those shown in FIG. 1 are designated by the same reference numerals.

In the figure, 6 is a third lens unit having a positive refracting power, which has both an image plane correction function for correcting an image plane that fluctuates with zooming and a focusing function for focusing, and 7 is fixed. Is a fourth group of the positive refractive power of.

The present embodiment differs from the first embodiment in that the third lens group 6 is moved on the optical axis as indicated by the arrow b in the figure to correct the image plane which fluctuates due to zooming and to focus. That is, the present point and the fourth group are fixed during zooming and focusing.

The other structure and the principle of vibration isolation are substantially the same as those of the first embodiment, and the same effects as those of the first embodiment are obtained.

As described above, according to the present invention, at least one lens group among the plurality of lens groups provided closer to the image surface than the second lens group (magnifying portion) is moved along the optical axis to correct the image surface and focus. In the variable power optical system that performs both of the above and the above, at the time of image stabilization, the first group is rotated from the rear principal point to the image plane side about a point on the optical axis that is separated by approximately its focal length. As a result, a vibration damping effect is obtained while maintaining good optical performance.

Next, numerical examples of the present invention will be shown. In the numerical examples, 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, and Ni and νi are respectively from the object side of the i-th lens. The refractive index of glass and the Abbe number. Table 1 shows the relationship with each conditional expression in each numerical example.

Incidentally, R23 and R in the numerical embodiments 1 and 3
24, R21 and R22 in Numerical Example 2 are each a glass material (parallel plane plate) such as a face plate.

In Numerical Examples 1 to 3, R1 and R2 are lens groups having a function of correcting eccentric aberration during image stabilization, and R8 is a fixed diaphragm SSP for preventing changes in the image plane illuminance ratio during image stabilization.
Is.

The aspherical shape has an X axis in the optical axis direction, an h axis in the direction perpendicular to the optical axis, a positive light traveling direction, R ₀ is a paraxial radius of curvature, and B, C, D, and E are non-apertures, respectively. When using spherical coefficient

[0055]

[Equation 1] It is expressed by

Further, for example, the meaning of "D-0x" is "1.
0- ^x "is meant.

[0057]

[Equation 2]

[0058]

[Table 1] From the center of rotation R3 surface 6.629 R2 surface aspherical surface R ₀ = ∞ K = 0 B = −1.567D−04 R17 surface aspherical surface R ₀ = −7.6694 K = 3.257D + 00 B = −5.522D− 02 C = -4.060D-03 D = -1.530D-02 E = -6.584D-03

[0059]

[Equation 3]

[0060]

[Table 2] From the center of rotation R3 surface 5.242 R2 surface aspherical surface R ₀ = ∞ K = 0 B = −1.597D-04 R 15 surface aspherical surface R ₀ = 1.583 K = −7.8874D-02 B = −2. 815D-02 C = -2.773D-02 D = 1.404D-02 R20 surface aspheric surface _R0 = -2.351 K = 0 B = 5.229D-04 C = -5.074D-02 D =- 2.869D-02

[0061]

[Equation 4]

[0062]

[Table 3] From the center of rotation R3 surface 6.772 R2 surface Aspheric surface _R0 = ∞ K = 0 B = -1.503D-04 R17 surface Aspheric surface _R0 = 2.340 K = 3.307D + 00 B = -5.602D-02 C = -8.296D-03 D = -1.426D-02 E = -9.769D-03

[0063]

[Table 4]

[0064]

According to the present invention, as described above, the first group, which is an element of the variable power optical system, is rotated to spatially fix the first group against the tilt of the variable power optical system. In addition, it is configured to correct the image blur when the variable power optical system vibrates (tilts), and it is possible to obtain good vibration isolation characteristics even for high frequency vibration, and to downsize the entire device. It is possible to achieve a variable power optical system having an anti-vibration function.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a paraxial refractive power arrangement of an optical system according to Example 1 of the present invention.

FIG. 2 is a lens cross-sectional view of Numerical Example 1 of the present invention.

FIG. 3 is an explanatory diagram showing the principle of an optical system performed at the time of image stabilization according to the present invention.

FIG. 4 is a schematic diagram showing a paraxial refractive power arrangement of an optical system according to Example 2 of the present invention.

FIG. 5 is a diagram of various types of aberration at the wide-angle end according to Numerical Example 1 of the present invention.

FIG. 6 is a diagram of various types of aberration in the middle of Numerical Example 1 of the present invention.

FIG. 7 is a diagram of various types of aberration at the telephoto end according to Numerical Example 1 of the present invention.

FIG. 8 is a lateral aberration diagram in a numerical example 1 of the present invention at the telephoto end without decentering.

FIG. 9 is a lateral aberration diagram in the numerical example 1 of the present invention in which a blur angle of 2 ° is corrected at the telephoto end.

FIG. 10 is a diagram of various types of aberration at the wide-angle end according to Numerical Example 2 of the present invention.

FIG. 11 is a diagram of various types of aberration in the middle of Numerical Example 2 of the present invention.

FIG. 12 is a diagram of various types of aberration at the telephoto end according to Numerical Example 2 of the present invention.

FIG. 13 is a lateral aberration diagram in a numerical example 2 of the present invention at the telephoto end without decentering.

FIG. 14 is 2 at the telephoto end of Numerical Embodiment 2 of the present invention.
Lateral aberration diagram with corrected blur angle

FIG. 15 is a diagram of various types of aberration at the wide-angle end according to Numerical Example 3 of the present invention.

FIG. 16 is a diagram of various types of aberration in the middle of Numerical Example 3 of the present invention.

FIG. 17 is a diagram of various types of aberration at the telephoto end according to Numerical Example 3 of the present invention.

FIG. 18 is a lateral aberration diagram in a state without decentering at the telephoto end according to Numerical Example 3 of the present invention.

FIG. 19 is 2 at the telephoto end of Numerical Embodiment 3 of the present invention.
Lateral aberration diagram with corrected blur angle

[Explanation of symbols]

 1 1st group 2 2nd group 3,6 3rd group 4,7 4th group d d line g g line y image height Y maximum image height ΔM meridional image surface ΔS sagittal image surface 8 holding member 9 counterweight 10 lens group

Claims (5)

[Claims] 1. A variable power optical system in which a fixed first lens unit is provided closer to the object side than the variable power unit at the time of variable power and focusing, and the first lens unit is located from the rear side principal point to the image plane side. It is rotated about a point on the optical axis that is separated by the approximate focal length to be spatially fixed to the tilt of the variable power optical system, and a photographed image when the variable power optical system vibrates. In addition to correcting blur, at least one of the lens groups provided on the image plane side of the variable power unit is moved on the optical axis to focus on a finite distance object. Variable magnification optical system with anti-vibration function. 2. A first lens unit having a positive refractive power which is fixed during zooming and focusing from the object side, a second lens unit having a negative refractive power having a zooming function, and a lens unit fixed during zooming or At least one lens unit that moves, and the first unit rotates about a point on the optical axis that is away from the rear principal point to the image plane side by approximately its focal length, At least one of lens groups provided on the image plane side of the second group is fixed spatially with respect to tilting of the system to correct blur of a captured image when the variable power optical system vibrates. A variable-magnification optical system having a vibration-proof function, characterized in that an object at a finite distance is focused by moving two lens groups on the optical axis. 3. A first group having a positive refractive power, which is fixed during zooming and focusing, from the object side, a second group having a negative refractive power having a zooming function, and a third group having a positive refractive power. , And the fourth of positive refractive power
The image plane, which has four lens groups, is corrected by moving one of the third group and the fourth group on the optical axis and focusing is performed by the first lens group. The group is rotated about a point on the optical axis, which is separated from the rear principal point to the image plane side by approximately its focal length, and is spatially fixed with respect to the tilt of the variable power optical system. A variable-magnification optical system having an anti-vibration function, which is characterized by correcting blur of a captured image when the magnification optical system vibrates. 4. A lens group A having a fixed paraxial refracting power of substantially 0 is provided on the object side of the first lens group during zooming and image stabilization, and decentering aberration is corrected by the lens group A. A variable power optical system having a vibration isolation function according to claim 1, 2 or 3. 5. The variable power optical system having an image stabilizing function according to claim 4, wherein at least one lens surface of the lens group A is composed of an aspherical surface.