JPH02238431A - Vibration proofing optical system - Google Patents

Abstract

PURPOSE:To prevent an eccentric aberration fluctuation when a second group vibrates by forming one lens surface by an aspherical surface in a second group, setting a point on an optical axis separated by a specific distance to an image surface side from a principal point of the image side of a second group as a supporting point so that a second group becomes turnable and placing it in front of a photographing system, and correcting a blur at the time when the photographing system is inclined by turning a second group. CONSTITUTION:In a second group 2, at least one lens surface is formed by an aspherical surface, and when a focal distance of a first group 1 and image forming magnification of the second group 2 are denoted as f1 and beta2, respectively, a point on an optical axis separated by about beta2.f1/(1-beta2) to an image surface side from a principal point of the image side of the second group 2 is set as a supporting point 3 so that the second group becomes turnable and placed in front of a photographing system 11. In this state, a blur of a photographing image at the time when the photographing system 11 is inclined is corrected by turning a second group 2. In such a way, a satisfactory optical performance by which the quantity of generation of an eccentric aberration at the time when a second group 2 is turned and brought to eccentricity is small can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of industrial use) The present invention relates to an anti-vibration optical system, and in particular to an anti-vibration optical system that is placed in front of a photographing system 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 performing static correction to obtain still images.

(Prior art) When attempting to take a photograph from a moving object L such as a moving car or aircraft, vibrations are transmitted to the lit JJe system and Ji! Blurring occurs in the shadow image.

2. Description of the Related Art Various types of anti-shake optical systems have been proposed that have a 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 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 publications, an optical member that is spatially fixed against vibration is arranged in a part of the imaging system, and by utilizing the prism effect generated in response to the vibration of this optical member, the photographed image is deflected onto the imaging plane. I am getting a still image.

In addition, it uses an acceleration sensor to detect vibrations in the shooting system,
Depending on the signal obtained at this time, 1l! There is also a method of obtaining a still image by vibrating some lens groups of the shadow system in a direction perpendicular to the optical axis.

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 f, is placed in front of the 15812 system, and the rt When the shadow system vibrates, the second lens group is used as a movable lens group for vibration isolation, and a dirt-proof optical system is proposed that utilizes an inertial pendulum system supported gimbally at its focal position.

(Problems to be Solved by the Invention) In general, 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 produce a still image. In order to achieve this, the entire device becomes larger, and the relationship between the amount of correction for blur in the photographed image and the amount of movement of the movable lens group becomes complicated, resulting in a problem that the mechanism of the entire device becomes complicated.

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. 2,959,088, 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, the focal length is ll! When If 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, making the entire device larger.

In order to reduce the size of the entire device, the focal length f of the second group can be made smaller, but this poses a problem in that eccentric aberration fluctuations increase when the second group is vibrated.

The present invention is arranged in front of the WL shadow system to simplify the rotational relationship of the movable lens group due to the vibration of the imaging system, and to reduce the pre-photographed image that occurs when the imaging system vibrates, and also to decenter the movable lens group. It is an object of the present invention to provide an anti-vibration optical system which produces less decentering aberrations when the object is tilted, and which is well-corrected while reducing the size of the entire device.

(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 second group having an aspheric surface on at least one lens surface, and the focal length of the first group When f1 is the imaging magnification of the second group, and β2 is the imaging magnification of the second group, 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 is The second group is arranged in front of the photographing system so as to be rotatable as a fulcrum, and the shake of the photographed image when the photographing system is tilted is corrected by rotating the second group. It is characterized by what it did.

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 be a finite value, or Said 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 lIlift) and a rotatable second group with positive refractive power (focal length 11if2). 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 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/(l−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 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, in order to simplify the rotation relationship, and to 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 to be described later, at least one lens surface in the second group is made an aspherical surface to reduce eccentric aberration fluctuations when the second group is rotated and decentered during image stabilization. Prevents deterioration of optical performance.

In particular, the aspheric surface at this time has a shape in which the positive refractive power weakens as it goes from the center of the lens surface toward the periphery (when applied to a positive refractive surface, it has a shape in which the curvature becomes gentler toward the periphery of the lens,
For example, m M'. When using a zoom lens, distortion at the wide-angle end and spherical aberration and coma aberration at the telephoto end are well corrected.

Further, in this example, when the aspherical shape is defined as ΔR2, the distance between the effective diameter of the aspherical surface and the paraxial spherical surface at a position 70% from the lens center] xlQ-'< lΔR2 / f21 < 2.2
It is set to satisfy X to -3. This allows the effect of the aspheric lens to be fully exhibited, and satisfactorily corrects fluctuations in decentering aberrations when the second group is rotated for vibration isolation.

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

Let A be the intersection of the first group and the optical axis 11a when the imaging 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, or 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 initial non-vibrating state is at point D on the nine-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)・f2D
-DI=B-Bl ・DC/BC=-fl ・
θ becomes 1.

Considering the state of image formation by the first group at this time, the imaging light at point D1, which is a distance f1 and θ1 from the nine-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-DI-θ, then the imaging relational expression, D-D
Since I=fl·θ, θ=−01.

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.

Similar to FIG. 2, FIG. 3 is a schematic diagram for explaining the image stabilization effect of the image stabilization optical system 10 when the photographing system is tilted by an angle θ1. 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=fl·ω. If the intersection of the extension of point D2 and Bl and the focal plane of the entire system is C2, then from the magnification relationship, C-C2=D1 ・DI= ・β2=f 1 ・
ω・β2.

Since the focal length @fT of the entire anti-vibration optical system is fT=f1・β2, the light beam with the nine axes 11a and the inclination ω in the initial state is separated from the optical axis by a distance of 111fl・β2・ω at the focal plane. image at the position. 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 interval between their principal points.

At this time, the fulcrum 3, which is the center of rotation of the second group, is the optical axis 1.
The point is a distance (1 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 1111fl, f2 is -f
It is set so that l≦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 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 -01 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 focus of the first group 1 and the front focus of the second group 2 are configured so that the first and second groups satisfy the formula e=fl+f2, so when there is no tilt, the 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-DI=-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 expressed by the imaging relational expression D-D1. = fl・θ
Therefore, θ=101.

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

The above description has been made using 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 can also form an afocal system at points other than the center of the photographic screen as described above. 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.

Figure 5 shows the actual numerical value 7 when the anti-vibration optical system 10 of the present invention is attached to a zoom lens as the photographing system 11.
FIG. 3 is a cross-sectional view of a lens in an example of Ji.

In the figure, lO is the anti-vibration optical system and the first group l with negative refractive power.
and a rotatable second group with positive refractive power. 11 is a 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, 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,
When D and E are each aspherical coefficients, it is expressed by the formula +DH'+EH''.

Numerical example (anti-vibration optical system) n l- 71.09 R 2- 615.56 R 3- 165.19 R 4- 53.34 R 5-128.58 1 {6 82.33 I17・ Aspherical surface R 8-150.8O f+ - -90 Aspheric coefficient 7th surface R-B-C- D- 82.62 -1.845 X 10-' 5.776 xlO-" -6.777 XIO-" 1- 11.00 2- 0.20 3- : l. 20 4-11.45 5- 2.80 6- 6.71 7-10.30 Nl・1.7+299 ν l−53.8N 2・1
．． 66672 ν 2・18.3N 3-1.69
680 ν 3-55.5N 4-1.60311
ν 4-80.7f2 ・90 e”Q (Photography system) F- 8.28 ~ 76.29 It +- 104.07 DI-11 2・ 4
5.63 D2-11:l-1ti:1.62D]-R4-
40.88 0 4- 2.60 9.30 0.15 5.00 FNolIl2 1.4-1.7 N l-1.80518 N 2-1.60311 N :1-1.62299 1-25. 4 2-60.7 3・58 R 5- 121.42 1{6・ 163.97 R 7- 14.67 It 8- -18.14 It 9- 17.54 RIO- -93.94 Rll- - 24.06 8l2-134.02 Rl3- 105.88 8l4- -27.07 Old 51 Aperture RI6- 38.07 Rl7--156.99 1118- -24.96 RI9- -74.34 1{20- 22.98 R21- 944.98 R22 Wing 2:1.30 R23- 11.75 R24- 871.81 R25- -46.29 R26- 15.91 D5~Variable D6 proverb 1.20 D 7- 4.54 0 8- 1.00 D 9- :I. 50 DIO-Variable DI1- 1.00 012-Variable D 3- 3.90 014- 1. :10 015- 2.00 016- :1.20 017- 1.85 018- 1.20 019- 0. +5 D20- 4.00 021-10.98 022- 1.00 023- 1.88 024- 2.50 025- 0.15 026- 3.60 N 4-1.83400 N N 5-1.71299 6 -1.84666 N 7-1.69680 N 8-1.71299 N 9-1.62299 NIO-1. 84666 N11-1.62299 N12-1.80518 N13-1.51633 N14-1.62299 4-37.2 5-53.8 6-23.9 7-55.5 8-53.8 l ν10-2 :1.9 νI1-58.1 ν12-25.4 ν13-64.1 ν14-58 027・5.00 1'{211- 00 028- 6.00 N15i. 51633ν15・64.1n29-
00 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 (1 fl) 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 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 arranging the optical system having the group in front of the photographing system, it is possible to simplify the rotational relationship, move the fulcrum when rotating the second group closer to the second group, and downsize the entire device. By using an aspherical surface, it is possible to achieve an anti-vibration optical system with good optical performance and less occurrence of decentering aberrations when the second group is rotated and decentered.

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

[Brief explanation of drawings]

Fig. 1 is a schematic view of the main parts of an embodiment of the image stabilizing optical system of the present invention mounted in front of the photographing system, and Fig. 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, Fig. 5 is a sectional view of a lens of a numerical example of the present invention, Figs. 6, 7, and 8. are the reference states in the numerical examples of the present invention, and when the imaging system is tilted by 1°, the imaging system is -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 set to 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. Meme Daisho (A) ＾-7 Wazu (A) ■Ichimen Karimata-sei'4P tank, H Matakago. M song M Matasu and 2)

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 second group having a non-contact lens on at least one lens surface. It has a spherical surface, and when the focal length of the first group is f1 and the imaging magnification of the second group is β2, approximately β2·f1/ The second group is placed in front of the photographing system so that it can rotate about a point on the optical axis that is separated by (1 - β2) as a fulcrum, and the blurring of the photographed image when the photographing system is tilted is prevented. An anti-vibration optical system characterized in that correction is performed 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 second group has a shape in which the positive refractive power becomes weaker from the center of the lens surface toward the periphery. Anti-vibration optical system.