JPH02239220A - Anti-vibration optical system - Google Patents

Abstract

PURPOSE:To obtain the vibrationproof optical system which is well corrected of the blur of a photographic image when a photographing system tilts while the system is miniaturized by forming at least one aspherical face each on the 1st group and 2nd group of the optical system having the two lens groups and correcting the above-mentioned blur by turning the 2nd group. CONSTITUTION:The vibrationproof optical system 10 has the two lens groups; the 1st group 1 having a negative refracting power and the turnable 2nd group 2 having a positive refracting power, successively from an object side. The 1st group 1 is held in a lens barrel and is fixed to the photographing system. The 2nd group 2 forms the object image formed within a focal plane by the 1st group 1 on a prescribed face at a magnification beta2. A fulcrum 3 on an optical axis 11a to turn the 2nd group 2 exists at the position apart by a distance beta2.f1/(1-beta2) from the principal point on the image side of the 2nd group 2 in this case. Namely, the 2nd group 2 is so formed as to generate the deflection angle of the ray which is the same angle as the angle of inclination of the photographing system when the photographing system 11 tilts. The blur of the photographic image is prevented in this way while the optical system is miniaturized.

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 front of a photographing system, and is used to optically prevent 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 correcting 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.

Various types of anti-shake optical systems have been proposed that have the function of preventing blur in photographed images.

For example, in Japanese Patent Publication No. 56-21133, an optical device is provided with an image by moving some optical members in a direction that offsets the vibrational displacement of the image due to vibration, in response to an output signal from a detection means for detecting a vibration state. We are trying to stabilize the situation.

Japanese Patent Application Laid-open No. 1-22:18-19 discloses that in an imaging system in which a refractive variable apex prism is disposed closest to the subject, the apex angle of the refractive variable apex prism is changed in response to vibrations of the imaging system. The image is stabilized by deflecting the image.

Special Publication No. 14847, Publication No. 14847, Special Publication No. 57-741
In Publication No. 4, etc., an optical member that is spatially fixed against vibration is arranged in a part of the photographing system, and the photographed image is deflected by utilizing the prism effect generated in response to the vibration of this optical member, and the imaging plane is A still image is obtained above.

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 some lens groups of the S shadow system in a direction perpendicular to the nine axes in accordance with the signal obtained at this time.

In addition, in US Pat. No. 2,959,088, 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 Ilf, is arranged 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 to obtain a still image. If you try to do this, the entire device will become larger,
Another problem is that the relationship between the amount of pre-correction of the photographed image and the amount of movement of the movable lens group becomes complicated, which complicates the mechanism of the entire apparatus.

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 the above-mentioned US Pat. No. 2,959,0813, 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 downsize the entire device, the focal length of the second group is 11f.
It would be better to make it smaller, but then there was a problem that fluctuations in decentering aberrations would increase when the second group was vibrated.

The present invention aims to simplify the rotational relationship of the movable lens group due to the vibration of the photographing system by appropriately setting the lens configuration to prevent blurring of the photographed image that occurs when the photographing system vibrates by placing it in front of the photographing system. In addition, when the movable lens group is decentered, eccentric aberrations are less likely to occur, and the entire device is made smaller.
The purpose of the present invention is to provide a vibration-proof optical system that is well-corrected.

(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 having positive refractive power, the first group and the second group each having at least one aspherical surface, and the first group having at least one aspherical surface. The focal length of the group is fl
, 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 arranged in front of the photographing system, and the pretension of the photographed image 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 a finite value; Or, when the focal length of the second 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, then e=fl+f2. group and the second group, and the 21st!
It is characterized in that it is configured such that the imaging magnification β2 of T is infinite.

(Embodiment) FIG. 1 is a schematic diagram of a main part of an embodiment in which a dirt-proof 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 1l. 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 11 ifl) and a rotatable second group with positive refractive power (focal length f2). There is.

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 n1 on a predetermined plane at a magnification β2 (1lr limit or infinity).

Reference numeral 3 denotes a fulcrum on the optical axis 11a for rotating the second group, and is located at a distance from the image-side principal point of the second group 2 by a distance β2·fl/(1−β2). (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 81 which rotates around the second group of fulcrums 3. 6 is the imaging plane.

In this embodiment, for example, the photographing system 11 (camera body) has an angle θ
When tilted, the first group 1 and the imaging system 11 are tilted at the same angle θ. 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 group and the second group are configured as described above, and the second group is made to produce a ray deflection angle that is the same angle as the inclination angle of the imaging system, simplifying the rotational relationship, and The fulcrum for rotating the second group is positioned as close to the object side as possible, and the camera shake is corrected to obtain a still image while reducing the size of the entire device.

Furthermore, as shown in the numerical examples described later, at least one aspherical surface is applied to each of the first and second groups to reduce aberration fluctuations in the entire lens system when the anti-vibration optical system is mounted in front of the photographing system. It maintains high optical performance.

Furthermore, when the second group is rotated and decentered during vibration isolation, fluctuations in decentering aberrations are reduced, thereby preventing deterioration in optical performance.

In particular, in this case, it is preferable that the aspherical surface provided on the lens surface of the first group having negative refractive power be such that the positive refractive power becomes stronger as it goes from the center of the lens surface toward the periphery. For example, when applying to a positive refractive surface (convex surface), the curvature should become stronger (the radius of curvature becomes smaller) toward the periphery of the lens, and when applying to a negative refractive surface (concave), the curvature should become weaker (the radius of curvature becomes smaller). It is better to make it larger).

The aspherical surface provided in the second lens group having positive refractive power is preferably such that the positive refractive power becomes weaker from the center of the lens surface toward the periphery. For example, when applying it to a positive refractive surface, the curvature should become weaker (the radius of curvature becomes larger) toward the periphery of the lens, and when applying it to a negative refractive surface, the curvature should become stronger (the radius of curvature becomes smaller). It's good.

In this way, in this embodiment, by specifying the aspherical shape, the optical performance of the entire lens system is kept good when the image stabilization optical system is mounted in front of the photographing system. Furthermore, the occurrence of decentering aberrations when the second group is rotated and decentered is reduced, thereby preventing deterioration of optical performance.

For example, when a zoom lens is used as a photographing system, distortion at the wide-angle end, spherical aberration, coma, etc. at the telephoto end are well corrected.

Furthermore, in this embodiment, the aspherical shapes provided in the first and second groups are 1.9X when the distance between the effective diameter of the aspherical surface and the paraxial spherical surface at a position 70% from the lens center is ΔR1 and ΔR2, respectively. 10-'<lΔRl/fll<3
．． 5x 10-'3 xlO-'< lΔR2
/ f21<2.2x 10-3. This allows the effect of non-spherical lens to be fully demonstrated, for example, maintains good optical performance when an anti-vibration optical system is attached to a photographing system, and allows the second group to be rotated for anti-vibration purposes. This effectively compensates for fluctuations in decentering aberrations caused by

FIG. 2 is a schematic diagram for explaining the anti-vibration effect of the anti-vibration optical system lO in this practical hh example. This shows the case where the element is set.

Let A be the intersection of the first group and the optical axis 11a when the photographing 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 vibration, 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, and the subject moves downward at an angle of 101 degrees, and point B also moves to point B1, which is tilted downward at 101 degrees around fulcrum 3. Indicates the condition.

(However, B, B1=β2·f1·θ1/(1−β2).) Now, consider the imaging state of point C at the center of the screen. The object in the first non-photographed 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, BC=(1-β2)·f2.

Considering the image formation frame of the first group of images at this time, the image forming light at a point DI, which is a distance f1·θ1 away from the optical axis 11a on the image side focal plane of the first group, is directed in parallel from the first group. If the emitted tilt is Zo-A-or=b, then 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.

FIG. 3 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 ZDIA-D2=ω, D1·D2=f1·ω. Letting point D2, C2 be the intersection of the extension of Bl and the focal plane of the entire system, C-C2=D1.D2.β2=f1.ω.β2 from the magnification relationship.

Since the focal length @fT of the entire anti-vibration optical system is fT=f1・β2, the optical glaze 11a in the initial state and the light flux with the inclination ω are focused at a position beyond the optical axis by a distance of 1111fl・β2・ω image is formed. This is the same as Moe's C-C2.

By the way, ZD-A-DI=101, and the object 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 example, the first group! and the second group 2 are arranged so as to satisfy the equation e=fl+f2, where e is the principal point interval.

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

In particular, the focal lengths fl and f2 of the first and second groups are −fl≦f
2, that is, the angular magnification γ of the first and second groups is
An afocal system is configured such that 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 Fig. 4, as in Fig. 2, for simplicity, the photographing system and the first group 1 are relatively fixed, and the subject moves downward at an angle of 101 degrees, and point B also moves downward around the fulcrum 3. The figure shows a state in which the robot has moved to a point B1 tilted by 101 degrees. (However, B, B
1=-fl·θ1. ) 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 light rays are traced backward from point C, the light beams incident on the second group will be parallel. Since the light beam passing through point B1 is not subjected to refraction, it travels parallel to the optical axis.

The rear focal point of the first group 1 and the front focal point of the second group 2 are configured so that the first group and the second group satisfy 2〇=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
The image is formed at a point D1 that is stepped downward from the 9th axis at 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 a point D1 located at a distance of f1·θ1 from the optical axis 11a on the image-side focal plane of the first group is emitted in parallel from the first group, and the inclination θ at that time is determined by the imaging relational expression D-D1. = fl・θ
Therefore, 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.

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 Numerical Example 1, which will be described later, when 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 same figure, 10 is a dirt-proof optical system, and the first group 1 has a negative refractive power.
and a rotatable second group with positive refractive power. 1l is the photographing system, which includes a focus lens group F and a variable magnification lens group V.
, a correction lens group C for correcting image fluctuations due to zooming, and an imaging lens group R. Sho ST
is the aperture.

Next, numerical examples of an anti-vibration optical system according to the present invention and a photographing system equipped with the anti-vibration optical system 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 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) (Numerical example!) Rl/non-spherical R 2- 93. :10 R 3-651.22 R 4- 49.16 15- Aspheric R 6-289.79 f1 -90 Aspheric coefficient 1st surface R- 62.68 11- 5. l2X C-5. :14 Filtration 6.35 D3-:l. +0 0 4 plays 5,63 D 5-14.00 N IllI. 49171 v l-57.4N
2=1.69]50 v 2-53.2N 3
・1.4917 ν 3-57.4 f2 - 90 e=0 10-' 1040IQ-13 51.40 -7.06x 10-' -5.07x 10-" 2.40x +0-13 D I -10.80 0 2- 8. Old 0 3- 3.10 0 4- 4.82 D 5-to 100 N l・I.49171 v I-57.4N
2i. [i9350 v 2s53.2N 3
-1.49171 v 3s57.4R6 - Aspheric fl - -90 Aspheric coefficient 1st surface n- 67.38 Low C- D~ (Photography system) F- 8.28~76 R 1・ 104.07 1+ 2- 45.63 R :]-163.62 1+ 4- 40.88 R 5- 121.42 It 6- 16:l. 97 R 7- 14.67 R 8- -18.14 R 9- 17.54 RIO・ -93.94 Mouth I+- -24.06 1112--1:14.02 6.61X 10-' -5. 74x fO-" 3.73x 10-" f2-90 C ~ 0 6th side R-199.88 B- 7.2 XIO-' C-8.06X 10"" D-:I. 65x IO-'Go29 FNo=l:1.4 ~1.7D
I-2.60 N I-1.805+8
v Is25.40 2- 9.30 N
2-1.60311 ν 2-60.70:
l- 0.15 D 4- 5.00 N 3-1.6229
9 v 3-58.1 D5・Machihen D 6- 1.20 N 4 feces 1.8340
0 ν 4-37.20 7- 4.54 D 8- 1.00 N 5-1.7+29
9 ν 5-5: 1.8D 9- 3.50
N 6ml. 84666 v 6-23.90
10-Variable DI1- 1.00 N 7-1.69680 ν
7-55.5012-Variable R13 105.88 Rl4- -27.07 R15 - Aperture R16-: l8.07 RI7 wet-156.99 1118- -24.96 119-74.34 n20- 22.98 n21- 944.98 R22 ■ 23.30 R23 +1.75 n24- 871.81 R25- -46.29 Ft26- 15.91 1 {27 婁 ■ R28- (X) 1129- ω 013- 3.90 DI4 -1. :10 015- 2.00 016- 3.20 017 Trout 1.85 018- 1.20 Dl9- 0. +5 D20- 4.00 021-10.98 D22 meal l. 00 023 1.88 D24- 2.50 D25- 0.15 D26- 3.60 D27- 5.00 D28- 6.00 N 8-1.71299 ν 8-53. 8 N 9-1.62299 ν 9-58.1NIO
=1.84666 v 10-23.9NII=! ．． 6
2299 v41=58.1Nl2-1.805+8
ν12-25.4N13=1.51633 v 1
:ll64.1N14 horse mackerel 1.62299 ν l4
San 58.1 Nl5 Maro 1.516:13 ν15-64
．． 1. In each of the above embodiments, the fulcrum position for rotating the second group must be fi & closely spaced from the image-side principal point of the second group by (-fl) or β2·fl/(1-β2). However, as long as an acceptable still image can be obtained due to static motion, it may be set within an allowable range of, for example, ±10%.

Further, in this embodiment, an auxiliary mechanism for holding the second group at the fulcrum or a damping mechanism may be provided to prevent adverse effects caused by contact of the end points.

(Effects of the Invention) According to the present invention, the first group and the second group of optical properties as described above are
By placing the optical system containing the group in front of the i-shadow system, we can simplify the rotational relationship, move the fulcrum when rotating the second group closer to the second group, and downsize the entire device. Furthermore, by using aspheric surfaces in each of the first and second groups, the optical performance of the entire lens system is maintained well when mounted in front of the photographing system, and even when the second group is rotated and decentered. It is possible to achieve an anti-vibration optical system having good optical performance with a small amount of decentering aberration.

Furthermore, by providing a counterweight for the second group, it is possible to correct blur in a photographed image without using a motion detection means such as an acceleration sensor, and to achieve an anti-vibration optical system that can easily obtain still images. .

[Brief explanation of drawings]

':i1 Figure is a schematic view of the main part of an embodiment when the anti-vibration optical system of the present invention is installed in front of the #@shading system, and Figure 2. Figure 3,
Fig. 4 is a schematic diagram for explaining the anti-vibration effect of the anti-vibration optical system of the present invention, and Fig. 5 is a diagram showing the anti-vibration optical system of Numerical Example 1 of the present invention installed in front of the Jilt shadow system. 6, 7, and 8 are numerical example 1 of the present invention, respectively.
Aberration diagrams in the reference state, when the ti shadow system is tilted by 1°, and when the imaging system is tilted by -1°, Figs. 9 and 10. 1st
Figure 1 shows aberration diagrams when the anti-pregnancy optical system of Numerical Example 2 of the present invention is mounted in front of the imaging system, in the standard state, when the imaging system is tilted by 10°, and when the imaging system is tilted by -1°. be. In the aberration diagrams, (A) is the wide-angle end, (B) is the telephoto end, h is the incident height when the light beam is centered at 0, 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.

Claims (5)

[Claims] (1) An optical system having two lens groups, a first group having a negative refractive power and a second group having a positive refractive power, in order from the object side, the first group and the second group each having at least Each one has an aspherical surface, and when the focal length of the first group is f1 and the imaging magnification of the second group is β2, approximately from the image side principal point of the second group to the image plane side. The second group is placed in front of the imaging system so that it can rotate about a point on the optical axis that is separated by β2・f1/(1-β2), and the imaging system is tilted. An anti-vibration optical system characterized in that image blur is corrected by rotating the 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 one aspherical surface provided in the first group has a shape in which the positive refractive power becomes stronger as it goes from the center of the lens toward the periphery, and the one aspherical surface provided in the second group has a shape in which the positive refractive power becomes stronger as it goes from the center of the lens to the periphery. 4. The anti-vibration optical system according to claim 2, wherein the optical system has a shape in which the positive refractive power becomes weaker toward the periphery.