JPH02239221A - Vibrationproof optical system - Google Patents

Abstract

PURPOSE:To simplify the parts relating to turning and to miniaturize the entire part of the device by disposing the optical system consisting of a 1st group and 2nd group having specific optical properties in front of a photographing system. CONSTITUTION:The optical system 10 has the lens groups; the 1st group 1 (focal length f1) having a negative refracting power and the turnable 2nd group 2 having a positive refracting power, successively from an object side. The 2nd group is so formed as to be turnable around a fulcrum 3 on the optical axis apart by approximately beta2.f1/(1-beta2) from the principal point on the image side of the 2nd group 2 to the image side. The blur of the photographic image generated when the optical system is disposed in front of the photographing system and when the photographing system oscillates is well corrected while the parts relating to the turning of the movable lens group arising from the oscillation of the photographing system are simplified, the weight of the movable lens group is reduced and the size over the entire part of the device is reduced.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to an anti-vibration optical system, and particularly to an anti-vibration optical system, which is placed in the direction of a photographing system, and which optically prevents blurring of photographed images when the photographing system vibrates (tilts). The present invention relates to an anti-vibration optical system suitable for photographic cameras, video cameras, etc., which stabilizes photographed images by performing static correction to obtain still images.

(Prior Art) When attempting to photograph a moving object such as a moving car or an airplane, vibrations are transmitted to the photographing system, causing precipitation in the photographed image.

2. Description of the Related Art Various anti-vibration optical systems have been proposed that have a function of preventing blur in a photographed image.

For example, in Japanese Patent Publication No. 56-21133, a part of the optical member is moved in a direction that offsets the dynamic displacement of an image due to vibration in response to an output signal from a detection means for detecting a vibration state in an optical device. Efforts are being made to stabilize the image.

Japanese Patent Laid-Open No. 61-223819 discloses an imaging system in which a refractive variable apex angle prism is disposed closest to the subject, and an image is captured by changing the apex angle of the refractive variable apex prism in response to vibrations of the imaging system. The image is stabilized by deflecting it.

Special Publication No. 56-34847, Special Publication No. 57-7414
In the above publication, an optical member that is spatially fixed against vibration is arranged in a part of the photographing system, and the photographed image is deflected and formed by utilizing the bulim effect that occurs in response to the vibration of this optical member. A still image is obtained on the surface.

In addition, it uses an acceleration sensor to detect vibrations in the shooting system,
There is also a method of obtaining a still image by vibrating a lens group in the photographing system in a direction perpendicular to the optical axis in accordance with the signal obtained at this time.

In addition, in U.S. Patent No. 2959088, an afocal system consisting of two lens groups, a first group and a second group, each having negative and positive refractive powers with the same absolute value of focal length @f, is placed in front of the photographing system. We have proposed an anti-vibration optical system using an inertial pendulum system in which the second group is used as a movable lens group for anti-vibration when the system vibrates, and is gimbally supported at its focal position.

(Problem to be solved by the invention) Generally, an anti-vibration optical system is placed in front of the photographing system, and a part of the movable lens group of the anti-vibration optical system is vibrated to eliminate blur in the photographed image and obtain a still image. If you try to do this, the entire device will become larger,
Further, there is a problem in that the relationship between the amount of correction for blurring of the photographed image and the amount of movement of the movable lens group becomes complicated, which complicates the mechanism of the entire device.

Another problem is that when the movable lens group is vibrated, the amount of decentering aberrations that occur increases, resulting in a significant drop in optical performance.

For example, in U.S. Pat. No. 2,959,088 to Moeshi, the second group, which is a movable lens group, is gimbally supported at a position on the optical axis separated by a focal length f from its principal point.

In order to reduce fluctuations in aberrations when the second group is vibrated, the focal length f of the second group should be as large as possible. However, when the focal length f is increased, its support point is displaced to the rear of the photographing system, and, for example, the position of the counterweight becomes distant from the second group, resulting in an increase in the size of the entire apparatus.

On the other hand, in order to reduce the size of the entire device, the focal length of the second group is 111.
It is possible to reduce f, but then there is a problem in that fluctuations in decentering aberrations increase when the second group is vibrated.

The present invention is arranged in the correction of the photographing system to simplify the rotational relationship of the movable lens group that occurs when the photographing system vibrates, and to reduce the weight of the movable lens group. The object of the present invention is to provide an anti-vibration optical system that is well-corrected while reducing the overall size.

(Means for Solving the Problems) The anti-vibration optical system of the present invention has a first lens having a negative refractive power in order from the object side.
An optical system having two lens groups, a lens group and a second group with positive refractive power, the material of the lens constituting the second group is made of a plastic material, and the focal length of the first group is f1. , when the imaging magnification of the second group is β2, the fulcrum is a point on the optical axis that is approximately β2·fl/(1-β2) away from the image-side principal point of the second group toward the image plane. The second group is rotatably placed in front of the photographing system, and blurring of the W and shadow images when the photographing system is tilted is corrected by rotating the second group. It is characterized by

In particular, in the present invention, the optical system having the first group and the second group has a predetermined refractive power as a whole, and the imaging magnification β2 of the second group is configured to have an infinite value; or the second
When the focal length of the first group is f2, the condition -fl≦f2 is satisfied, and when the distance between the principal points of the first group and the second group is e, the first group and the second group are adjusted so that e=fl+f2. It is characterized in that the groups are arranged so that the imaging magnification β2 of the second group becomes infinite.

(Embodiment) FIG. 1 is a schematic diagram of a main part of an embodiment in which the image stabilization 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 10 denotes an anti-vibration optical system, which is installed in front of the photographing system 11. The anti-vibration optical system 10 has two lens groups, in order from the object side: a first group with negative refractive power (focal length @f1) and a rotatable second group with positive refractive power (focal length @f2). are doing.

The first group 1 is held by a lens barrel (not shown) and fixed to an imaging system (camera body). The second group 2 forms an object image (virtual image) formed in the focal plane by the first group 1 on a predetermined plane at a magnification β2 (finite or infinite).

3 is a fulcrum on the optical axis 11a for rotating the second group, and is located at a distance β2·fl/(1−β2) from the image-side principal point of the second group 2. (When the magnification β2 is infinite, -f
1) 5 is a holding member that holds the second group. A counterweight 4 is provided at the other end of the holding member 5, and has a weight that balances the weight of the second group, which rotates the second group about the fulcrum 3. 6 is an imaging plane.

In this embodiment, for example, the photographing system 11 (camera body) has an angle θ
When tilted, the first group 1 is tilted by the same angle θ together with the imaging system 1l. On the other hand, the second group is spatially fixed by a counterweight 4. In other words, the initial posture is maintained. At this time, the first and second groups are configured as described above, and the rotational relationship is simplified by making the first and second groups produce the same angle of ray deviation as the inclination angle of the imaging system. The fulcrum for rotating the second group is positioned as close to the object as possible, and the pre-correction of the photographed image is achieved while reducing the overall size of the device to obtain a still image.

In addition, as shown in numerical examples to be described later, the material of the lens constituting the second group is made of plastic material, thereby reducing the weight of the second group and the entire anti-vibration optical system. The rotation operation during vibration isolation is made quick and accurate with a small driving force.

In particular, in this embodiment, the second group having a positive refractive power is constituted by a positive lens made of a plastic material and both lens surfaces are convex, thereby effectively reducing the weight of the second group, which tends to be heavy.

In addition, in this embodiment, the lens can be manufactured by plastic molding, which facilitates mass production and makes it possible to easily obtain an aspherical lens.

Additionally, the weight of the counterweight used to balance the second lens group has been reduced, thereby reducing the weight of the entire anti-vibration optical system.

FIG. 2 is a schematic diagram for explaining the anti-vibration effect of the anti-vibration optical system 10 in this embodiment. In the figure, the anti-vibration optical system is a thin lens, and each element is adjusted so that the whole has a predetermined refractive power. This shows the case where .

Let A be the intersection of the first group and the optical axis 11a when the W&shadow system is not tilted, and B be the intersection of the second group 2 and the optical axis 11a.

When the imaging system is tilted upward by a small angle θ1 due to imaging, etc.,
The first group 1 is similarly tilted by an angle θ1, but the second group 2 maintains its initial attitude.

In Figure 2, for simplicity, the imaging system is relatively fixed, the subject moves downward at an angle of 101 degrees, and point B also moves to point B1, which is inclined downward at 101 degrees around fulcrum 3. This shows the state in which the

(However, B, B1 = β2・f1・θ1. / (1 −
β2). ) Here, consider the imaging state of point C at the center of the screen. The object in the initial non-vibrating state is at point D on the optical axis 11a. If the ray is traced in the opposite direction from point C, the ray connecting point C and point B1 will not be subject to refraction and will travel straight, moving downward from the rear focal position of the first group 1, that is, the object point position D of the second group. The image is formed on point D1. Here, when it is 1, it becomes =(1-β2)·f2.

Considering the state of image formation by the first group at this time, the imaging light at point D1, which is a distance f1·θ1 away from the optical axis 11a on the image-side focal plane of the first group, is emitted from the first group in parallel. If the slope is 4D-A-D1=θ, the imaging relational expression, D-DI
From =fl·θ, θ=−θ1.

That is, the light is emitted parallel to the same direction as the object in the initial state. This means, conversely, that the subject does not move from point C at the center of the screen even if the photographing system is tilted.

Next, consider the imaging state at points other than the center of the screen.

7g3 is a schematic diagram for explaining the image stabilizing effect of the image stabilizing optical system 10 when the imaging system is tilted by an angle θ1, similar to FIG. 2. In this figure, the same symbols as in FIG. 2 have the same meanings.

Point C2 indicates a point around the screen. An arbitrary point on the image-side focal plane of the first group 1 is designated as D2. When toiA-D2=ω, D1·D2=fl·ω. If the intersection of the extension of points D2 and Bl and the focal plane of the entire system is C2, then from the magnification relationship, C-C2=D1.D2.β2=f1.ω.β2.

The focal length of the entire defense optical system, 11fT, is fT=f1・β2
Therefore, in the initial state, a light beam having an optical axis 11a and an inclination ω forms an image at a position distant from the optical axis by a distance lift·β2·ω. This is the same as C-C2 described above.

By the way, ZD-A-D1=-θ1, and the subject D at the center of the screen is imaged at a constant point C regardless of the tilt of the photographing system (camera body).

As a result, any arbitrary point C2 around the screen is focused on a constant point regardless of the tilt of the camera body, and an image stabilization effect can be obtained.

FIG. 4 is a schematic diagram for explaining the vibration-proofing effect shown in the same way as in FIG. 2 when the vibration-proofing optical system is constituted by an afocal system.

In this embodiment, the first group 1 and the second group 2 are arranged so as to satisfy the equation e=fl+f2, where e is the distance between their principal points.

At this time, the fulcrum 3, which is the center of rotation of the second group, is the 9th axis 1
The point is a distance (-fl) from the image-side principal point of the second group 2 on 1a.

In particular, the focal length of the first and second groups is 111fl, f2 is −fl
≦f2, that is, the first group and the second group constitute an afocal system in which the angular magnification γ is γ≦1. This allows the fulcrum 3 to be positioned closer to the object than the rear focal point of the second group, thereby reducing the size of the entire device when rotating the second group.

In Figure 4, like Figure 2, for simplicity, the photographing system and first group 1 are relatively fixed, and the subject is positioned downward at an angle of 10! It shows a state in which the point B has moved in a direction tilted by 101 degrees, and the point B has also moved to a point B1 which is tilted 101 degrees downward about the fulcrum 3. (However, B, B
1=-fl·θ1. ) Now consider the image-formed frame at point C at the center of the screen. The object in the initial non-vibrating state is at point D on the optical axis 11a. If the light rays are traced backward from point C, the light beams incident on the second group will be parallel. The light rays passing through point B1 are not subjected to refraction and therefore travel parallel to the nine axes.

The rear focus of the first group 1 and the front focus of the second group 2 are configured so that the first group and the east second group satisfy the formula e=fl+f2, so when there is no tilt, they are on the optical axis 11a. They match at point D. On the other hand, the luminous flux when tilted is from point D to B-B
An image is formed at a point D1 located downwardly from the optical axis by the same distance as l.

That is, in FIG. 4, D-D1=-fl·θ1.

Consider the imaging state of the image point D1 by the first group 1 at this time. Imaging light at point D1, which is located at a distance of f1·θ1 from the optical axis 11a on the image-side focal plane of the first group, is emitted from the first group in parallel, and the inclination θ at that time is expressed by the imaging relational expression, D-DI = fl・θ
Therefore, θ=−θl.

That is, the light is emitted parallel to the same direction as the object in the initial state. This means, conversely, that the subject does not move from point C at the center of the screen even if the photographing system is tilted.

The above has been explained by taking a thin lens system as an example, but the same applies to a thick lens system as long as the distance between the principal points is small.

In the explanation of Fig. 4, we took the center of the screen as an example to show the case where the photographing system vibrates and is tilted, but the first and second groups constitute an afocal system as described above even at points other than the center of the photographic screen. It is clear from this that a still image can be obtained with the blurring of the photographed image corrected in the same way as in the center of the screen.

FIG. 5 is a lens sectional view of a numerical example in which the image stabilizing optical system 10 of the present invention is mounted in front of a zoom lens as the photographing system 11.

In the figure, 10 is an anti-vibration optical system with a first group 1 having negative refractive power.
and a rotatable second group with positive refractive power. l1 is the photographing system, which includes a focus lens group F and a variable power lens group V.
, a correction lens group C for correcting the image plane that changes with zooming, and an imaging lens group R. Sho ST
is the aperture.

Next, a numerical example related to FIG. 5 will be shown.

In the numerical examples, Ri is the radius of curvature of the i-th lens surface from the object side, Di is the thickness and air gap of the i-th lens from the object side, and Ni and νi are the i-th lens surface from the object side, respectively.
These are the refractive index and Abpe number of the glass of the th lens.

The aspherical shape has an X axis in the optical axis direction, an H axis in a direction perpendicular to the optical axis,
The traveling direction of the light is positive, R is the paraxial radius of curvature, A, B, C,
It is expressed by the formula +DH'+EH'°, where D and E are each aspherical coefficients.

Numerical example (anti-vibration optical system) R1・Aspheric surface R 2- 93.41 R: ]-630.30 R 4- 49.16 R5・Aspheric surface R 6-283.43 fl rumor-90 Aspheric coefficient No. 1 side R- 63.86 B- 5.07x 10-' C- 5.08X 10-" D- -1.18X 10'-13 (I shadow system) F Mackerel 8.28-76.29 R I- 104.07 DI 2.601 2
- 45.63 0 2- 9.308
3-163.62 0 3- 0.15
R 4- 40.88 D 4- 5
．． 00It 5- 121.42 0 5-variable f
2-90 1-10.80 2-6.42 3-3.10 4.Variable 5-14.00 Nl Seal 1.51823 ν 1-59. 0N 2
-1.69350 ν 2-53.2N 3-1.
49171 ν 3-57.4e-0 51.59 -7.08x 1G-' -5. O x 10-" 2.51x 10-L3 PNoi: 1.4 ~ 1.7 N 1.80518 ν 1-25.4N
2-1.60311 ν 2-80.7N 3-1
．． 62299 ν 3-58.1R 6-16
3.97 R 7- 14.87 R 8- -18.14 R 9- 17.54 RIQ- -93.94 Rll- -24.08 RI2-134.1)2 R13- 105.88 8 4- - 27.07 RI5- Aperture RI6- 38.07 R 7-156.99 8 8- -24.96 8l9- -74.34 82 [)- 22.98 821- 944.98 822 Rin 23.30 823- 11 .75 R24- 871.81 R25- -46.29 R28- 15.91 R27- ω D 6- 1.20 0 7- 4.54 D 8- 1.00 0 9- 3.50 010-Variable DI1- 1.00 1) 12-variable D 3- 3.90 014- 1. :10 D] 5- 2.00 016- 3.20 D 7 meals 1.85 0 8- 1.20 019- 0.15 020- 4.00 D21-10.98 D22- 1.00 D23- 1. 88 D24@2.50 D25- 0. ! 5 028- 3.60 027- 5.00 N 4-1.83400 N N 5-1. 71299 6-1. 84666 N 7@1. 69680 N 8-1. 71299 N NIO-1. 84666 NJI-1.82299 N12-1.80518 Nl3 rot 1.51633 N14-1.62299 4-37.2 5 swelling 53, 8 6-23.9 7-55.5 8-53.8 9-58. 1 ν10-23.9 ν11-58.1 ν 12-25.4 ν 13-64.1 ν 14-58.1 R28 set ■ D28- 6.00 Nl5 city 1.51633 ν15-64.1 R29-
oo In each of the above embodiments, the fulcrum position for rotating the second group is strictly from the image-side principal point of the second group (-f1) or β2.
Even if the distance is not fl/(1-β2), as long as an acceptable still image can be obtained due to vibration, it may be set within a tolerance range of, for example, ±10%.

Further, in this embodiment, an auxiliary mechanism for holding the second group at the fulcrum and a damping mechanism may be provided to prevent adverse effects caused by contact with the pane point.

(Effects of the Invention) According to the present invention, the first group of optical properties as described above and 'M
By placing the optical system having two groups in front of the photographing system, the rotational relationship can be simplified, the fulcrum for rotating the second group can be moved closer to the second group, and the entire device can be made more compact. Furthermore, the lens material of the second group is made of plastic to reduce the weight of the counterweight as well as the second group, thereby reducing the weight of the entire anti-vibration optical system, resulting in an anti-vibration optical system with good rotational operability. system can be achieved.

Further, by providing a counterweight to the second group, it is possible to correct the pre-shape of a photographed image without using a vibration detecting means such as an acceleration sensor, thereby achieving an anti-vibration optical system that can easily obtain a still image.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of the essential parts of an embodiment of the anti-vibration optical system of the present invention installed in front of the imaging system, and Figs. 2, 3, and 4 are the anti-vibration optical systems of the present invention, respectively. 5 is a cross-sectional view of a lens in a numerical embodiment of the present invention, and FIGS. 6, 7, and 8 are a reference state in a numerical embodiment of the present invention, respectively. When the shooting system is tilted by 1°, the shooting system is tilted by -1°.
It is an aberration diagram when tilted. In the aberration diagrams, (A) is the wide-angle end, (B) is the telephoto end, h is the incident height when the center of the luminous flux is O, and y is the image height. In the figure, 10 is an anti-shake optical system, 11 is an imaging system, 1 is a first group,
2 is a second group, 3 is a fulcrum, 4 is a counterweight, 5 is a holding member, and 6 is an imaging plane. Figure 1o Figure (A) Figure (B) Spherical aberration, astigmatism, distortion, mC4 diagram (A) Figure (B) Spherical aberration, astigmatism, distortion, ngin diagram (A)

Claims (5)

[Claims] (1) An optical system having two lens groups, a first group with a negative refractive power and a second group with a positive refractive power, in order from the object side, and the material of the lens constituting the second group is plastic. When the focal length of the first group is f1 and the imaging magnification of the second group is β2, approximately β2·f1/(1 The second group is arranged in front of the photographing system so that it can rotate about a point on the optical axis that is separated by -β2), and the blurring of the photographed image when the photographing system is tilted is An anti-vibration optical system characterized by compensation by rotating a second group. (2) The optical system having the first group and the second group has a predetermined refractive power as a whole, and the imaging magnification β2 of the second group is configured to have a finite value. The anti-vibration optical system according to claim 1. (3) When the focal length of the second group is f2, -f1≦
The first group and the second group are arranged so that e=f1+f2 when the principal point distance between the first group and the second group is e, and the image formation of the second group satisfies the condition f2. The anti-vibration optical system according to claim 1, characterized in that the magnification β2 is configured to be infinite. (4) The holding member that holds the second group is provided with a counterweight that balances the weight of the second group with respect to the fulcrum. The anti-vibration optical system according to 3. (5) The vibration-proof optical system according to claim 2 or 3, wherein the second group has a positive lens made of a plastic material and both lens surfaces are convex.