JPH06289324A - Vibration-proof optical system - Google Patents

Abstract

PURPOSE:To reduce a decentering aberration generated at the time of camera shake compensation by using an aspherical surface lens which has nearly no refracting power in a fixed lens arranged on the object side of a lens group that moves at the time of camera shape prevention. CONSTITUTION:A vibration-proof optical system 8 is mounted in front of a photography system 11 and has two lens groups, i.e., a 1st group (focal length f1) having negative refracting power and a 2nd rotatable group 2 (focal length f2) having positive refracting power in order from the object side. When the photography system 11 slants, the 1st group 1 slants at the same angle together with the photography system 11. The 2nd group 2, on the other hand, is spatially fixed by a counterweight 4. At this time, the 2nd group 2 is given the same angle of light beam deviation as the tilt angle of the photography system 11 to correct a camera shake. Then the 1st group 1 is provided with the aspherical surface 7 which has nearly no refracting power to reduce the decentering aberration generated at the time of the rotation of the 2nd group 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration-proof optical system, and more particularly, it is arranged in front of a photographing system and optically corrects a photographed image blur when the photographing system vibrates (tilts) to obtain a still image. The present invention relates to an anti-vibration optical system suitable for a photographic camera, a video camera, etc. in which a captured image is stabilized.

[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.

JP-A-56-34847 and JP-B-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, the vibration of the photographing system is detected by utilizing the acceleration sensor, and a part of the lens group of the photographing system is vibrated in the direction orthogonal to the optical axis in accordance with the signal obtained at this time to obtain a still image. There are also ways to get it.

In addition, in US Pat. No. 2,959,088, an afocal system composed of two lens groups, a first lens group and a second lens group, having negative and positive refracting powers with the same absolute value of the focal length f, is arranged in front of the photographing system. Then, when the photographing system vibrates, the second lens group is used as a vibration-proof movable lens group, and an anti-vibration optical system utilizing an inertial pendulum system in which a gimbal is supported at the focal position is proposed.

[0009]

Generally, an anti-vibration optical system is arranged in front of a photographing system, and a movable lens group of a part of the anti-vibration optical system is vibrated to eliminate blurring of a photographed image and obtain a still image. Then, there is a problem that the entire apparatus becomes large and the relationship between the amount of blur correction of a captured image and the amount of movement of the movable lens group becomes complicated and the mechanism of the entire apparatus becomes complicated.

Further, there is a problem in that the amount of decentering aberration generated when the movable lens group is vibrated is increased and the optical performance is significantly deteriorated.

For example, in the above-mentioned US Pat. No. 2,590,88, the second lens group, which is a movable lens group, has a focal length f from its principal point.
Gimbal is supported at a position apart from the optical axis.

In order to reduce the fluctuation of aberration when the second lens unit is vibrated, the focal length f of the second lens unit should be as large as possible. However, if the focal length f is increased, the supporting point is displaced to the rear of the image pickup system, and the position of the counterweight becomes far from the second group, for example, and the size of the entire apparatus becomes large.

On the other hand, in order to reduce the size of the entire apparatus, it is sufficient to reduce the focal length f of the second lens unit. However, this causes a problem that fluctuations of decentering aberration when the second lens unit is vibrated increases. It was Here, it is effective to use aspherical lenses in the second and first groups in order to correct the decentration aberration variation, especially the decentration distortion aberration occurring at the wide-angle end.

By the way, when it is desired to directly apply an aspherical surface to a glass lens, it is necessary to perform grinding.
This is a very expensive task. On the other hand, it is difficult to produce an aspherical surface by molding and obtain a large diameter aspherical lens. And it tends to be advantageous to mold a plastic lens having a relatively large diameter as compared with glass.

On the other hand, however, when a plurality of plastic lenses are used, the deterioration of the optical performance due to the change of the focal length of the plastic lenses caused by the influence of the wet temperature becomes a problem.

The present invention is arranged in front of the photographing system, and the blurring of the photographed image generated when the photographing system vibrates is appropriately set by the lens configuration to simplify the rotational relation of the movable lens group due to the vibration of the photographing system. It is an object of the present invention to provide an anti-vibration optical system that has been satisfactorily corrected while reducing the generation of decentration aberrations when the movable lens group is decentered and reducing the size of the entire apparatus.

[0017]

The vibration-proof optical system of the present invention rotates the movable lens group inside the photographing optical system with respect to the photographing optical system about a certain point. Alternatively, it is an optical system that corrects the blurring of a photographed image when the photographing system tilts by parallel eccentricity, and has a lens group fixed to the eccentricity of the movable lens on the object side of the movable lens group. The fixed lens has at least one aspherical lens having almost no refractive power.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic view of an essential part of an embodiment in which the image stabilizing optical system of the present invention is mounted in front of a photographing system (fixed focal length lens, zoom lens, etc.).

In the figure, reference numeral 8 is a vibration-proof optical system, which is mounted in front of the photographing system 11. The vibration-proof optical system 8 has two lens groups, in order from the object side, a first lens group having a negative refractive power (focal length f1) and a rotatable second lens group having a positive refractive power (focal length f2). There is.

Reference numeral 3 denotes a fulcrum on the optical axis 9 for rotating the second lens unit, which is a distance β2 · f1 / (1- from the image-side principal point of the second lens unit 2.
Being apart by β2). (Magnification β2 is the magnification of the second group, and when this value is infinite, it is −f1) 5 is a holding member for holding the second group. A counterweight 4 is provided at the other end of the holding member 5 and has a weight that balances with the weight of the second group that rotates the second group around the fulcrum 3. 6 is an image plane.

In this embodiment, for example, the photographing system (camera body)
Is tilted at the angle θ, the first group 1 is tilted at the same angle θ together with the imaging system. On the other hand, the second group is spatially fixed by the counterweight 4. In other words, I try to keep my initial posture. And at this time, the first group and the second group
The group is configured as described above, the second group is caused to generate a beam deflection angle of the same angle as the tilt angle of the imaging system, the rotation relationship is simplified, and the fulcrum for rotating the second group is preferably formed. The still image is obtained by locating the object side and correcting the blur of the photographed image while downsizing the entire device.

By providing the first lens group with the aspherical lens 7 having almost no refracting power, it is possible to greatly reduce the eccentric aberration, especially the eccentric distortion, which occurs when the second group rotates. Become.

Even if a plurality of plastic lenses are used, the influence of the wet temperature can be reduced by giving almost no refractive power to the aspherical lens of the first lens group.

FIG. 2 is a schematic diagram for explaining the vibration-proof effect of the vibration-proof optical system in this embodiment. In FIG. 2, each vibration-proof optical system is a thin lens and has a predetermined refractive power as a whole. It shows the case where the element is set.

Let A be the intersection of the first lens group and the optical axis 9 when the photographing system is not tilted, and B be the intersection of the second lens group 2 and the optical axis 9.

The photographing system moves upward by a minute angle θ1 due to vibration or the like.
When tilted, the first group 1 similarly tilts at an angle θ1 but the second group 2
Keeps his initial position.

In FIG. 2, for the sake of simplicity, the photographing system is relatively fixed, and the subject moves downward in the direction inclined by −θ1 degrees.
The point B also shows a state in which the point B is moved downwardly about the fulcrum 3 to a point B1 tilted by −θ1 degrees.

(However, B, B1 = β2 · f1 · θ1 / (1
-Β2). ) Here, consider the image formation state of the point C at the center of the screen. The first non-vibrating subject is at point D on the optical axis 9. If a ray is traced backward from point C, the ray connecting point C and point B1 will not go through the refraction action and will go straight,
The image is formed at the rear focal position of the first lens group 1, that is, at a point D1 which is located below the object point position D of the second lens group. Where BC = (1-β
2) ・ f2,

[0029]

[Outer 1] Therefore, D.D1 = B.B1.DC / BC = -f1-
θ1.

Considering the image formation state of the image at this time by the first group, the distance f1.multidot.f from the optical axis 11a at the image side focal plane of the first group.
The imaging light at the point D1 which is separated by θ1 is emitted from the first group in parallel and the inclination is ∠D · A · D1 = θ. From the imaging relational expression, D · D1 = f1 · θ, θ = −θ1 Become.

That is, the light is emitted in parallel with the same direction as the subject in the initial state. On the contrary, this means that the subject does not move from the point C at the center of the screen even if the photographing system tilts.

FIG. 3 is a conceptual diagram for explaining the effect of the aspherical lens in the present invention. (A) shows a normal non-eccentric state, and (B) shows a state in which the second group has rotated to correct blur. The height of the off-axis light ray 10 passing through the first group and the second group is higher in the first group and lower in the second group than in the state (A) in the state (B). Since the first lens group has a negative refractive power and the second lens group has a positive refractive power, at this time, a negative distortion aberration variation due to decentering occurs.

In order to correct this eccentric distortion, an aspherical surface whose positive refractive power becomes stronger toward the periphery in the first group, and an aspherical surface whose positive refractive power becomes weaker toward the periphery in the second group are introduced. It is effective to do. Since the weight of the movable second group also affects the counterweight, it is desirable to use a plastic aspherical lens for weight reduction.

At this time, when the aspherical lens is introduced into the first lens group, the negative lens has a strong refractive power and the difference in thickness between the center and the periphery is large, so that plastic molding is difficult. First
It is advantageous in terms of shape to mold the positive lens of the lens group into a plastic mold, but when the humidity temperature changes, the first group and the second group
Since the plastics of the group both become positive lenses, the influence on the optical performance becomes large. In this embodiment, this problem is mitigated by introducing a plastic aspherical lens, which has little power in the first lens group and is effective for aberration correction.

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, and Di is the i-th lens surface from the object side.
The th lens thickness and the air gap, Ni and νi are the refractive index and the Abbe number of the glass of the ith lens in order from the object side.

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, and R as a paraxial radius of curvature.
When A, B, C, D, and E are aspherical coefficients, respectively

[0038]

[Outside 2] It is expressed by

Incidentally, R36 and R37 are filters such as face plates.

[0040]

[Outside 3]

[0041]

According to the present invention, as described above, at least one aspherical lens having almost no refracting power is provided in the fixed lens disposed on the object side of the lens group which is movable at the time of preventing blurring. As a result, it becomes possible to reduce the eccentric aberration that occurs during blur correction.

Further, the influence of temperature and humidity, which is a problem when using a plurality of aspherical plastic lenses, can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic view of a main part of a vibration-proof optical system according to the present invention.

FIG. 2 is a schematic diagram for explaining the image stabilization effect of the image stabilization optical system according to the present invention.

FIG. 3 is a schematic diagram for explaining the image stabilizing effect of the image stabilizing optical system according to the present invention.

FIG. 4 is a lens cross-sectional view of an embodiment of the image stabilization optical system according to the present invention.

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

FIG. 6 is a diagram of various types of aberration at an intermediate zoom position according to an example of the present invention.

FIG. 7 is a diagram of various types of aberration at the telephoto end according to an example of the present invention.

FIG. 8 is distortion aberration with the wide angle end when the imaging system is tilted ± 1 °.

[Explanation of symbols]

 8 Anti-vibration optical system 1 1st group 2 2nd group 3 Rotation center

Claims (1)

[Claims] 1. A blur of a photographed image when the photographing system is tilted by rotating a movable lens group inside the optical system around a certain point or decentering the parallel with respect to the photographing optical system. An optical system for correction, which has a lens group fixed to the decentering of the movable lens on the object side of the movable lens group, and the fixed lens is at least one aspherical lens having almost no refractive power. An anti-vibration optical system having.