JPH02238429A - Vibration proofing optical system - Google Patents

Abstract

PURPOSE:To satisfactorily correct a blur, while miniaturizing the whole device by setting a point on an optical axis separated by a specific distance to an image surface side from a principal point of an 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 of a photographing image at the time when the photographing system is inclined by turning a second group. CONSTITUTION:When a focal distance of a first group 1 and image forming magnification of a 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 an image side of the second group 2 is set as a supporting point 3 so that the second group 2 becomes turnable and placed in front of a photographing system, and a blur of a photographing image at the time when the photographing system 11 is included is corrected by turning the second group 2 concerned. In such a way, a vibration proofing optical system 10 by which a turning relation is simplified and the supporting point 3 at the time of turning the second group 2 is brought close to the second group 2, and the whole device is miniaturized can be obtained.

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, small camera cameras, etc., which stabilizes photographed images by correcting the image to obtain a still image.

(Prior Art) When attempting to photograph a moving object such as a moving car or aircraft, vibrations are transmitted to the photographing system, causing blur in the photographed 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. 61-2241819 discloses that in a photographing 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 photographing system to obtain an image. 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 vibrations is arranged in a part of the photographing system, and by utilizing the prism effect generated in response to vibrations of this optical member, 1N! The two images are deflected to obtain a still image on the imaging plane.

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 moving 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. Pat. No. 2,959,088, the first group and the second group 7ff have a negative focal length Rf that is equal in absolute value and an IF refractive power.
An afuokanore system consisting of two lens groups is placed in front of the first ring lens system, and when the photographing system vibrates, the 7jS2
We are proposing an anti-vibration optical system using an inertial pendulum system in which the group is the main movable lens for anti-vibration, and its focal point is supported gimbally at seven positions.

(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. If this were to be achieved, the overall size of the device would increase, and the relationship between the blur correction function of the photographed image and the amount of movement of the movable lens group would become complicated, resulting in a problem that the mechanism of the entire device would become 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 U.S. Pat. No. 2,959,088 mentioned by IM, the second group, which is a movable lens group, is gimbally supported at a position on nine axes that is distanced from its principal point by a focal length f.

In order to reduce aberration fluctuations when the second group is vibrated, the focal length 111f 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 f of the 'fJZ group can be made smaller, but this poses the problem of increasing eccentric aberration fluctuations when the second group is vibrated.

The present invention is arranged in front of the photographing system to simplify the rotational relationship of the movable lens group due to the vibration of the photographing system to prevent blurring of the photographed image that occurs when the photographing system vibrates, and also to decenter the movable lens group. (Means for Solving the Problems) The purpose of the present invention is to provide an anti-vibration optical system that produces less decentering aberrations when the device is tilted and is well-corrected while reducing the size of the entire device. The system consists of the first lens with negative refractive power in order from the object side.
This optical system has two lens groups, a lens group and a second group with positive refractive power, and has a predetermined refractive power as a whole, and the focal length of the first group is set to fl. When the imaging magnification of the second group is β2, approximately β2·fl/(
The second group is placed in front of the photographing system so as to be rotatable about a point on the optical axis that is 1-β2) apart, and the blurring of the photographed image when the photographing system is tilted is corrected. It is characterized in that the correction is made by rotating the second group.

In particular, in the present invention, the holding member that holds the second group includes:
It is characterized in that a counterweight is provided to the fulcrum to balance the weight of the second group.

(Example) FIG. 1 is a schematic diagram of the main parts of an example of a one-piece/i-cage system when the image stabilization optical system of the present invention is mounted on the αη side 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 l1. 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 i!llfl) and a rotatable second group with positive refractive power (focal length 111f2). 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.

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. 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 the same angle of ray deflection 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 shake of the photographed image is corrected while reducing the size of the entire device and obtaining a still image.

FIG. 2 is a schematic diagram for explaining the anti-vibration effect of the anti-vibration optical system 10 at this time, and in this figure, the anti-vibration optical system is shown as a thin lens.

When the photographing system is not tilted, the intersection of the first group and the optical axis 11a is A,? Let B be the intersection of the lg2 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 Bl, which is inclined 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 optical axis 11a. If the ray is traced backwards from point C, the ray connecting point C and point Bl will go straight because it is not subjected to refraction, and will move downward away from the rear focal point 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? Since DC= (2-β2-■)・f2, β 2 D-D1=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 tilt is ZD-A-DI=θ, the imaging relational expression, D-D1=
From fl·θ, θ=101.

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=fl·ω. If the point D2, C2 is the intersection of the extension of Bl and the focal plane of the entire system, it becomes Z due to the magnification relationship.

Since the focal length lfT of the entire anti-vibration optical system is fT=f1・β2, the optical axis 11a in the initial state and the light beam having the inclination ω are located at a distance @f1・β2・ω from the optical axis on the focal plane. Form an image. This is the same as C-C2 described below.

By the way, 4D-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.

In this embodiment, in order to make the distance from the image-side principal point of the second group to the fulcrum 3 shorter than the opposite sign value of the focal length f1 of the first group, the following is satisfied.

This means that fl<0 or 4β2×1. However, in the range of 0<β2 minus 1, β2·fl/(1−β2) is negative. That is, the fulcrum 3 will be located closer to the object than the second group, making the vibration isolation mechanism structurally difficult.

Further, in the case of β2 to 0, the value becomes β2·fl/(1−β2) 0.

For this reason, in this embodiment, it is set to approximately -100<β2<-0.3, thereby appropriately setting the position of the fulcrum 3, and thereby reducing the size of the entire device.

Next, a concrete numerical example of this embodiment will be shown. However, e is the distance between the principal points of the first group and the second group, and 2 is the distance from the image-side principal point of the second group to the fulcrum 3 when rotating the second group.

fl=-90 f2=33.33β2=-
0.5 e = 102 = 30 In addition, in this embodiment, the fulcrum position for rotating the second group does not have to be strictly apart from the image-side principal point of the second group by β2·fl/(1-β2). , it may be set within a permissible range of ±10%, for example, as long as an acceptable still image can be obtained due to vibration.

Further, in this embodiment, an auxiliary mechanism for holding the second group at the fulcrum and a damping mechanism may be provided to prevent the 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 with the group in front of the m-shading 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. Therefore, it is possible to achieve a vibration-proof optical system.

Furthermore, by providing a counterweight for the second group, it is possible to correct blur in a photographed image without using a photographing 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 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 and 3 each illustrate the anti-vibration effect of the anti-vibration optical system of the present invention. It is a schematic diagram for explaining. 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 (3)

[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, and having a predetermined refractive power as a whole, The focal length of the first group is f
1. When the imaging magnification of the second group is β2, the fulcrum is a point on the optical axis that is approximately β2·f1/(1-β2) away from the image-side principal point of the second group toward the image plane. The second group is arranged in front of the photographing system so as to be rotatable, and blurring of the photographed image when the photographing system is tilted is corrected by rotating the second group. An anti-vibration optical system characterized by: (2) 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. Vibrational optical system. (3) The focal length f1 of the first group and the imaging magnification β2 of the second group satisfy the following condition: -f1>β2·f1/(1-β2) The vibration-proof optical system according to claim 2.