JPH01140119A - Oscillationproof optical system - Google Patents

Abstract

PURPOSE:To well correct the blur of an image by oscillation, etc., and the chromatic aberration generated at the time of refraction by displacing the relative distances between the respective prism hypotenuses of a pair of prisms thereby changing the relative positions between the prisms. CONSTITUTION:A photographing lens 1 and the prism 6 consisting of the two prisms 6a, 6b each having a triangular shape are provided. The prisms 6a, 6b are disposed on both sides of an air layer in such a manner that the vertexes are positioned in the directions opposite to each other with respect to an optical axis 7. Of a pair of the prisms 6, for example, the prism 6b is moved to the image plane side by a distance l along the optical axis to change the relative positions between the prisms 6a and 6b. Particularly the relative positions between the prisms 6a and 6b are changed by changing the relative positions of the hypotenuses of the prisms 6a, 6b. The image is thereby displaced by the distance DELTA on the formed image 8 in the direction perpendicular to the optical axis 7, by which the blur of the image generated from, for example, the oscillation, etc., is corrected and the chromatic aberration generated at the time of the refraction is well corrected.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to an anti-vibration optical system, and in particular to an anti-vibration optical system using at least one pair of prisms suitable for photographic cameras, video cameras, etc. This invention relates to an anti-shake optical system that corrects image blur and the like.

(Prior Art) Conventionally, when photographing from a moving car or aircraft, vibrations are transmitted to the photographing system, causing blur in the photographed image.

As means for preventing such troubles, various vibration-proof optical systems using parallel plane plates or variable apex angle prisms have been proposed.

FIGS. 2 and 3 are schematic diagrams of conventional anti-vibration optical systems. In FIG. 2, a parallel plane plate 22 is placed on the image plane side of the main lens system 21.
is arranged, and the plane-parallel plate 22 is rotated by a rotation means having a rotation axis in a direction perpendicular to the plane of the paper according to the amount of image shake, thereby correcting the pretension of the image on the imaging plane 23.

In addition, in FIG. 3, a refractive variable apex angle prism 4 consisting of two types of elastic members 4a and 4b is arranged on the object side of the main lens system 21, and the prism 4 is moved by an actuator 5 in response to the shake of the entire imaging system. The image blur on the imaging plane 23 is corrected by changing the apex angle of the image plane 23.

However, in the image stabilization optical system shown in FIG. 2, in order to increase the amount of image deflection, the rotation angle of the parallel plane plate 23 must be increased or the parallel plane plate 23 must be made thicker, which increases the size of the entire imaging system. There were some drawbacks.

Furthermore, the anti-vibration optical system shown in Figure 3 requires a large force to control the apex angle of the prism, which necessitates a large actuator, making it difficult to respond quickly as the entire imaging system becomes larger. There was a drawback.

(Problems to be Solved by the Invention) The present invention disposes at least one pair of prisms near or inside the photographic lens, and utilizes changes in the relative positions of each prism in the pair of prisms. To provide a compact and simple-configured anti-vibration optical system capable of quickly and effectively correcting image blur caused by shake of a photographic lens.

(Means for Solving the Problems) A photographing lens and a pair of prisms are provided, and the relative position between each prism of the pair of prisms is adjusted according to the tilt angle of the photographing lens due to vibration or the like. In an anti-vibration optical system that obtains a still image on an imaging plane by changing the relative distance between the hypotenuses of each prism of the pair of prisms, the relative position between each prism is changed. That's what I did.

(Embodiment) FIGS. 1A and 1B are schematic diagrams of an optical system according to an embodiment of the present invention. In the figure, 1 is a photographing lens, and 6 is a pair of prisms, two triangular prisms 6a.

6b, and the apex angles of the prisms 6a and 6b are opposite to each other with respect to the optical axis 7 with an air layer in between. It is arranged like this.

The same figure (A) is the standard state, the same figure (B) is a pair of prisms 6
One of the prisms, in this embodiment prism 6b, is moved along the optical axis 7 by a distance l toward the image plane to change the relative position between the two prisms 6a and 6b.

In particular, the relative position between the prisms 6a and 6b is changed by changing the relative position of the oblique sides of each prism 6a and 6b.

As a result, the image is displaced by a distance Δ on the image forming plane 8 in a direction perpendicular to the optical axis 7, thereby correcting image pretension caused by, for example, vibration.

In this embodiment, for example, the pair of prisms 6 may be rotated as a unit in a plane perpendicular to the plane of the paper to similarly correct the image pretension in the direction perpendicular to the plane of the paper.

In this embodiment, it is preferable that the two prisms 6a and 6b be made of different materials since this can reduce the influence of chromatic aberration.

FIG. 4 shows a distance l! in the direction along the optical axis between each prism 6a, 6b in the pair of prisms 6 of FIG. 11 is an explanatory diagram showing a state when the imaging position on the imaging plane 8 is displaced by a distance Δ. FIG.

In the figure, the refractive index, Abbe number, and apex angle of the prism 6a are na, shear, and δa, respectively, and the refractive index, Abbe number, and apex angle of the prism 6b are nb and νb, respectively.

Let it be δb. Also, let θa be the angle of the incident light beam deflected by the prism 6a, θb be the angle deflected by the prism 6b, 1 be the distance between the two prisms 6a and 6b, and S be the distance from the prism 6b to the imaging point 8. Then, it can be expressed as θa=(na-1)δa Δ =1·θa+S·θb. Here, in order to make the angle θa independent of the wavelength, dθa/dλ=0. That is, the material of the two prisms 6a and 6b is expressed by the formula (
The influence of chromatic aberration can be eliminated if the lens is made of a material that satisfies (1).

In order to perform more precise color correction, it is necessary to make the amount of displacement Δ independent of the wavelength. That is, since dΔ/dλ=0, it is necessary to satisfy -(2).

Generally, equation (2) is completely satisfied only in one particular arrangement. Therefore, according to equations (1) and (2), it is preferable to use a material having an Abbe number that satisfies the chromatic aberrations.

In addition, as shown in FIG. 5, each prism 6a.

6b is constructed by pasting together two members 6al and 6a2 or 6bl and 6b2 with different numbers of attachments, and each prism 6
Chromatic aberration may be corrected within a and 6b.

In FIG. 4, the apex angles δa and δb of the prisms 6a and 6b are
Letting δb〉δa, the right side of equation (3) becomes 1〈 νb/υ
It is preferable to set a≦3 in order to correct a predetermined chromatic aberration in a well-balanced manner.

FIG. 6 is a schematic diagram of an optical system according to another embodiment of the present invention.

In the figure, numerals 11 and 12 each represent a pair of prisms.

A pair of prisms if, 12 are arranged in orthogonal directions, and each prism 11a.

By displacing flb, 12a, and 12b in the optical axis direction, the light beam is deflected in two directions in the same manner as described above, thereby correcting the image pretension.

6(A) is a schematic diagram of the prism 11.12 in the X-Y plane, and FIG. 6(B) is a schematic diagram of the prism 11.12 in the Z-Y plane.
FIG. 3 is a schematic diagram in the X plane.

FIG. 7 is an explanatory diagram of another embodiment of a pair of prisms according to the present invention.

In this embodiment, the prisms 6a and 6b are displaced in a direction perpendicular to the optical axis to obtain the same effect as described above.

The figure (A) is the standard state, and the figure (B) is the same figure (A).
This shows the case where the light beam is deflected by a distance Δ on the image forming plane 8 when the prism 6b is displaced by a distance l111 from the state shown in FIG.

In this embodiment, the amount of deflection Δ of the light beam on the imaging plane is approximately proportional to the product of the amount of displacement of the prism 6b and the apex angle of the prism 6b. However, if the amount of displacement is too large, a large amount of space is required for movement, which increases the size of the entire lens system, generates many aberrations, and greatly reduces optical performance, which is not good.

Further, it is not good to make the prism apex angle too large because the optical properties will be greatly reduced. For this reason, the prism apex angle δ
It is preferable to set δ within the range of 2°≦δ≦45′ from the viewpoint of various aberrations and size.

FIGS. 8(A) and 8(B) are schematic diagrams of an embodiment in which the present invention is applied to a zoom lens. In the figure, 13 is a focus lens group, 14 is a variator, and 115 is a compensator. The variator 14 and the compensator 15 constitute a variable power section. 16 is a relay lens group.

Figure (A) shows the case where a pair of prisms 17 are placed on the object side of the variable magnification section, and since the amount of displacement of the image is constant regardless of the variable magnification state of the variable magnification section, the shake of the entire lens system Once the angle is detected, the amount of displacement of the prism can be immediately determined. Therefore, it is suitable for a vibration-proof optical system of the vibration angle detection control type.

Figure (B) shows the case where the prism 17 is placed on the image plane side of the variable magnification section, and since the amount of displacement of the image changes depending on the variable magnification state of the variable magnification section, an image movement amount detection control type anti-shake optical system is used. suitable for

Generally, when the positions of a plurality of prisms are relatively changed to deflect a light beam, the position of the light beam passing through the prisms changes, and the optical path length along the way changes. For example, in Figure 9 (A
) as a reference state, and as shown in FIG. 9(B), the prism 6a,
The distance in the optical axis direction of 6b is changed by 1. Then, the distance of the light beam 18 passing through the prism 6b changes from x1 to x2. The optical path difference ΔX at this time is Δx x Δ−(tan δ)−(n−1) where δ is the apex angle of the prism 6b and n is the refractive index.

Therefore, if there is an influence of the optical path difference ΔX, the amount of day focus caused by it may be detected in advance and the focus lens group may be driven.

In the above embodiment, a plurality of pairs of prisms 6 may be arranged and the distance between each prism may be changed independently.

(Effects of the Invention) According to the present invention, by changing the relative position of each prism of a pair of prisms having a predetermined shape as described above, it is possible to satisfactorily correct image pretension caused by vibration, etc. It is possible to achieve an anti-vibration optical system with high optical performance that can also satisfactorily correct chromatic aberration that occurs during refraction of the prism.

[Brief explanation of the drawing]

Figures 1 (A) and (B) are schematic diagrams of an optical system according to an embodiment of the present invention, Figures 2 and 3 are schematic diagrams of conventional anti-vibration optical systems, respectively, and Figure 4 is a schematic diagram of an optical system according to an embodiment of the present invention. Explanatory diagrams of chromatic aberration of such a pair of prisms, FIGS. 5, 6 (^), (B). FIGS. 7(^') and (B) are explanatory views of a pair of prisms according to the present invention, and FIGS. 8(^) and (B) are illustrations of an embodiment when the present invention is applied to a zoom lens. The explanatory diagrams, FIGS. 9(A) and 9(B), are explanatory diagrams showing the optical path difference of the light beams passing through a pair of prisms according to the present invention. In the figure, 1 is a photographing lens, 2 is a parallel plane plate, 3°8 is an imaging plane, 4 is an elastic prism, 5 is an actuator, 6,
11 and 17 are a pair of prisms, 7 is an incident light beam, 13 is a focus lens group, 14 is a variator, 115 is a compensator, and 16 is a relay lens group. % 2 Figure 4 Figure 5 aGb 7th mouth (A) Shini 7 2 (B) Ki 8 times (A) Kan 8 mouth (B) Figure 9 (A)

Claims (6)

[Claims] (1) A photographing lens and a pair of prisms are provided, and the image forming surface is formed by changing the relative position between each prism of the pair of prisms in accordance with the tilt angle of the photographing lens due to vibration, etc. The anti-vibration optical system described above for obtaining a still image is characterized in that the relative distance between the hypotenuses of each prism of the pair of prisms is changed to change the relative position between each prism. Anti-vibration optical system. (2) At least one of the pair of prisms is displaced in a direction parallel to the optical axis or in a direction perpendicular to the optical axis to change the relative position between the prisms. Anti-vibration optical system according to scope 1. (3) Each of the prisms of the pair of prisms is arranged such that the apex angles with respect to the optical axis are opposite to each other with an air layer in between. Vibrational optical system. (4) The Abbe number of the material of each prism of the pair of prisms is different, ν1 is the Abbe number of the material of the prism with the smaller apex angle, and the Abbe number of the material of the prism with the larger apex angle is The anti-vibration optical system according to claim 2, characterized in that, when ν2, the following condition is satisfied: 1<ν2/ν1<3. (5) The pair of prisms are set to be rotatable within a plane perpendicular to the optical axis while changing the relative distance between hypotenuses that intersect with the optical axis of each prism of the pair of prisms. An anti-vibration optical system according to claim 1. (6) Two of the above-mentioned pair of prisms are provided, one pair of prisms changes the relative distance between the prism hypotenuses that intersect with the optical axis of each prism, and the other pair of prisms changes the relative distance between each prism. 2. The anti-vibration optical system according to claim 1, wherein the direction of the apex angle of the prism is perpendicular to the direction of the apex angle of the one pair of prisms.