JPH06194560A - Variable power photographic optical system - Google Patents

Abstract

(57) [Abstract] [Purpose] To realize a variable-magnification shooting optical system that can shorten the overall camera length during telephoto shooting and that is easy to process and assemble. A variable magnification photographing optical system having at least a front lens group 2 and a rear lens group 3, wherein a rear lens group 3 and an image forming surface 1 are fixed, and an optical path from the rear lens group 3 to the image forming surface 1 is formed. It has a back focus variable mechanism 100 for changing the length, and while performing zooming by moving the front lens group 2, a back focus variable mechanism according to zooming so that the image forming position always matches the image forming plane 1. The optical path length is changed by 100.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable magnification photographing optical system. The variable magnification photographing optical system of the present invention can be used as a photographing system of a still camera, an electronic camera, or a video camera.

[0002]

2. Description of the Related Art A variable power photographing optical system has at least a front lens group and a rear lens group, and changes the distance between the front lens group and the rear lens group while keeping the entire position of the front lens group and the rear lens group on the image plane. It is displaced to perform zooming.

Generally, since the front and rear lens groups are extended toward the object side during telephoto shooting, there is a problem that the total length of the camera becomes large during telephoto shooting. In addition, since both the front and rear lens groups move during zooming, it is necessary to make processing precision, assembly precision, etc. stricter in order to suppress lens eccentricity that causes image quality deterioration. It was difficult to reduce the manufacturing cost.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and an object thereof is to provide a variable magnification photographing optical system which can shorten the total length of the camera at the time of telephoto photographing and which can be easily processed and assembled. To do.

[0005]

A variable magnification photographing optical system of the present invention has at least a front lens group, a rear lens group, and a back focus variable mechanism.

In the variable magnification photographing optical system according to the first aspect, "the rear lens group and the image plane" are fixed, and the back focus variable mechanism changes the "optical path length from the rear lens group to the image plane". Then, while performing zooming by moving the front lens group, the back focus variable mechanism changes the optical path length in accordance with zooming so that the image forming position always matches the image forming surface.

In the variable magnification photographing optical system according to the sixth aspect, the "front lens group and the image plane" are fixed, and the back focus variable mechanism changes the "optical path length from the front lens group to the image plane". Then, while performing zooming by moving the rear lens group, the back focus variable mechanism changes the optical path length in accordance with zooming so that the image forming position always matches the image forming surface.

The back focus variable mechanism includes "first and second plane mirrors arranged so as to sequentially reflect the image-forming light beam and turn the optical path of the image-forming light beam by 180 degrees, and the two plane mirrors described above in association with zooming. Has a moving mechanism for integrally moving the rear lens group in a direction parallel to the optical axis of the rear lens group (claims 2 and 7), or "the rear lens group is formed by sequentially reflecting image-forming light beams. First and second plane mirrors arranged so as to be bent in a direction orthogonal to the lens optical axis, and with zooming, the first plane mirror is moved in the rear lens group optical axis direction.
And a moving mechanism for simultaneously moving the second plane mirror in a direction orthogonal to the optical axis of the rear lens group "(claims 3 and 8).

Further, the back focus variable mechanism is arranged so as to be parallel to and swingable with respect to each other so as to sequentially reflect the image-forming light flux and bend it in a direction parallel to the optical axis of the rear lens group. With the plane mirror of, and zooming,
It has a moving / rotating mechanism for moving the first and second plane mirrors in directions opposite to each other in a direction parallel to the optical axis of the rear lens group, and for rotating them while maintaining a parallel relationship with each other. "
The present invention can also be configured as described above (claims 4 and 9), in which "a first plane mirror that reflects an image-forming light flux and bends it in a direction orthogonal to the optical axis of the rear group lens and a first plane mirror are used. The 2nd and 3rd which reflect the reflected light flux so that it is folded back 180 degrees
Plane mirror, a fourth plane mirror that reflects the light flux reflected by the third plane mirror in the same direction and in the same direction as the image-forming light flux that is incident on the first plane mirror, and the first and fourth plane mirrors associated with zooming.
And a moving mechanism for integrally moving the second and third flat mirrors in the direction orthogonal to the optical axis of the rear group lens (Claims 5 and 10).

[0010]

As described above, in the present invention, the front lens group or the rear lens group and the image plane position are fixed,
The change in the optical path length between the fixed lens group and the image plane due to zooming is realized by displacing the plurality of plane mirrors by the back focus variable mechanism.

[0011]

EXAMPLES Specific examples will be described below. Figure 1
An example is shown in which the variable magnification optical system according to claim 1 is applied to a zoom lens having a two-group configuration. FIG. 1B shows a relative position change of the image forming surface 1, the front lens group 2, and the rear lens group 3 due to zooming.

That is, the front lens group 2 and the rear lens group 3 are
As the magnification changes from the wide-angle end (WIDE) to the telephoto end (TELE), the lens unit moves toward the object side while monotonically narrowing the group interval, and the back focus becomes longer accordingly.

FIG. 1 (A) conceptually shows this application example, in which the rear lens group 3 and the image plane 1 are fixed,
The change of the group distance due to the magnification change is realized by displacing the front lens group 2 in the optical axis direction. The back focus change mechanism 100 realizes a change in back focus due to zooming.

A large change in back focus due to zooming is covered by the back focus variable mechanism 100, and the amount of extension of the front lens group 2 associated with telephoto photography is "a change in group spacing".
Since it is only for the telephoto shooting, the total length of the camera does not increase remarkably due to the extension of the front lens group 2.

2 to 5 show a specific embodiment of the back focus variable mechanism. The embodiment of FIG. 2 is an embodiment of the variable magnification photographing optical system described in claim 2. The back focus variable mechanism has a first plane mirror 4, a second plane mirror 5, and a moving mechanism (not shown) for moving these.

When the image-forming light flux emerges from the rear lens group 3, it is sequentially reflected by the plane mirrors 4 and 5 so that the optical path is turned back by 180 degrees and forms an image on the image-forming surface 1. At the time of zooming, the front lens group 2 is displaced to adjust the group distance to the rear lens group 3, and at the same time, the plane mirrors 4 and 5 are integrally moved in a direction parallel to the optical axis of the rear lens group. Assuming that the moving distance of the plane mirrors 4 and 5 is d, the back focus changes by 2d with this moving distance. Therefore, the back focus can be largely changed with a small moving amount of the plane mirrors 4 and 5.

As the moving mechanism (not shown), a known appropriate mechanism such as a mechanism using a rack and a pinion or a mechanism using a wire and a pulley can be used.

The embodiment of FIG. 3 is an embodiment of the variable magnification photographing optical system described in claim 3. The back focus variable mechanism is provided with the first plane mirror 6 and the second plane mirror 6 arranged so as to sequentially reflect the image-forming light flux and bend it in a direction orthogonal to the optical axis of the rear group lens.
The flat mirror 7 and a moving mechanism (not shown) for moving them at the same time.

When the image-forming light flux emerges from the rear lens group 3,
The light is reflected in order by the plane mirrors 6 and 7, and the optical path is changed to the rear lens group 3.
The image is bent in a direction orthogonal to the optical axis of, and an image is formed on the image plane 1. At the time of zooming, the front lens group 2 is displaced to adjust the group distance from the rear lens group 3, and at the same time, the first lens group 2 is adjusted.
The plane mirror 6 is moved in the optical axis direction of the rear group lens 3 and the second plane mirror 7 is moved in the direction orthogonal to the optical axis of the rear group lens 3 at the same time. The moving mechanism can be configured using, for example, a wire and a pulley.

The embodiment of FIG. 4 is an embodiment of the variable magnification photographing optical system described in claim 4. The back focus variable mechanism includes first and second plane mirrors 8 and 9 which are arranged so as to be parallel and swingable so as to sequentially reflect the image-forming light flux and bend it in a direction parallel to the optical axis of the rear group lens 3. It has a moving / rotating mechanism (not shown) for moving / rotating these.

When the image forming light flux is emitted from the rear lens group 3,
The light is sequentially reflected by the plane mirrors 8 and 9 and the optical path is changed to the rear lens group 3
An image is formed on the image plane 1 by being bent in a direction parallel to the optical axis of. At the time of zooming, the front lens group 2 is displaced to adjust the group distance from the rear lens group 3, and at the same time, the first plane mirror 8 and the second plane mirror 9 are moved in the optical axis direction of the rear lens group 3. While moving in opposite directions in parallel directions,
Rotate while maintaining a parallel relationship with each other. The moving / rotating mechanism may use a pulley and a wire to move, and a cam to rotate.

The embodiment of FIG. 5 is an embodiment of the variable magnification photographing optical system described in claim 5. The back focus variable mechanism includes a first plane mirror 10 that reflects the image-forming light flux and reflects it so as to bend it in a direction orthogonal to the optical axis of the rear group lens 3, and the plane mirror 1.
The second and third plane mirrors 11 and 12 (which are integrated with the plane mirror 11) that reflect the light flux reflected by 0 so as to be folded back by 180 degrees, and the light flux reflected by the plane mirror 12 are referred to as "plane mirror 1".
A fourth plane mirror 13 (integrated with the plane mirror 10) that reflects in the same direction and in the same direction as the image forming light beam incident on 0,
It has a moving mechanism (not shown) that integrally moves the second and third plane mirrors 11 and 12 in a direction orthogonal to the optical axis direction of the rear group lens 3.

When the image-forming light flux emerges from the rear lens group 3,
The light is sequentially reflected by the plane mirrors 10, 11, 12, and 13, the optical path is bent in a direction parallel to the optical axis of the rear group lens 3, and an image is formed on the image forming surface 1. At the time of zooming, the front lens group 2 is displaced to adjust the group distance from the rear lens group 3, and at the same time, the first and fourth plane mirrors 10 and 14 are fixed, and the second and third plane mirrors are fixed. 11 and 12 are integrally moved in a direction orthogonal to the optical axis direction of the rear group lens 3.

As the moving mechanism (not shown), a mechanism using a rack and a pinion, a mechanism using a wire and a pulley, etc. can be used as in the case of the embodiment shown in FIG.

FIG. 6 shows an example in which the variable magnification photographing optical system described in claim 6 is applied to a zoom lens having a two-group structure. In order to avoid complication, the same reference numerals as those in FIG. 1 are used for those which seem not to be confused. Figure 1 (B)
Indicates a relative positional change between the image forming surface 1, the front lens group 2, and the rear lens group 3 due to zooming. This figure is the same as FIG. 1 (B).

The front lens group 2 and the rear lens group 3 move toward the object side while monotonically narrowing the group distance as the magnification changes from the wide-angle end (WIDE) to the telephoto end (TELE), and the back focus accordingly. become longer. FIG. 6 (A) conceptually shows this application example, in which the front lens group 2 and the image plane 1 are fixed, and the change in the group spacing due to zooming causes the rear lens group 3 to move in the optical axis direction. It is realized by displacing to. Also,
The change of the optical path length from the front lens group 2 to the image plane 1 due to the magnification change is realized by the back focus variable mechanism 100.

Since the back focus variable mechanism 100 covers a large change in back focus due to zooming and the front lens group 2 is fixed, the total length of the camera does not increase even during telephoto shooting.

7 to 10 show concrete examples of the back focus variable mechanism. The embodiment of FIGS.
Each of them is an example of the variable magnification photographing optical system according to claims 7 to 10. Except for the fact that the front lens group 2 is fixed and the rear lens group 3 is moved, the examples shown in FIGS. 7 to 10 are the same as the examples shown in FIGS. Omit it.

[0029]

As described above, according to the present invention, a novel variable magnification photographing optical system can be provided. Since the variable magnification photographing optical system of the present invention has the above-mentioned configuration, it is possible to reduce or eliminate the increase in the total length of the camera at the time of telephoto photographing.

Further, since one of the front and rear lens groups is fixed, extremely high precision is not required for processing precision and assembling precision for suppressing lens decentering which causes deterioration of image quality. Cost reduction is possible.

In the variable magnification photographing optical system according to the second to fifth and sixth to tenth aspects, since the change in the optical path length due to the change in magnification is absorbed by the movement or rotation of the plurality of plane mirrors, the optical path length is largely changed by the small movement of the plane mirror. Further, by retracting these plane mirrors when the lens is housed, it is possible to make the camera configuration more compact than before.

[Brief description of drawings]

FIG. 1 is an explanatory diagram in which the invention according to claim 1 is applied to a two-group zoom lens.

FIG. 2 is a diagram for explaining one embodiment of the invention according to claim 2;

FIG. 3 is a diagram for explaining one embodiment of the invention according to claim 3;

FIG. 4 is a diagram for explaining one embodiment of the invention according to claim 4;

FIG. 5 is a diagram for explaining one embodiment of the invention according to claim 5;

FIG. 6 is an explanatory diagram in which the invention according to claim 6 is applied to a two-group zoom lens.

FIG. 7 is a diagram for explaining one embodiment of the invention according to claim 7;

FIG. 8 is a diagram for explaining one embodiment of the invention according to claim 8;

FIG. 9 is a diagram for explaining one embodiment of the invention according to claim 9;

FIG. 10 is a diagram for explaining one embodiment of the invention according to claim 10;

[Explanation of symbols]

 1 Image plane 2 Front group lens 3 Rear group lens 100 Back focus variable mechanism

Claims (10)

[Claims] 1. A variable magnification photographing optical system having at least a front lens group and a rear lens group, wherein a rear lens group and an image forming surface are fixed, and an optical path length from the rear lens group to the image forming surface is changed. A back focus variable mechanism for zooming is performed by moving the front lens group, and the optical path length is changed by the back focus variable mechanism according to zooming so that the image forming position always matches the image forming plane. A variable-magnification photographic optical system configured as described above. 2. The variable magnification photographing optical system according to claim 1, wherein the back focus variable mechanism is provided so as to sequentially reflect the image-forming light beam and turn the optical path of the image-forming light beam by 180 degrees. And a moving mechanism for integrally moving the two flat mirrors in a direction parallel to the optical axis of the rear lens group with zooming. 3. The variable magnification photographing optical system according to claim 1, wherein the back focus variable mechanism is arranged so as to sequentially reflect the image-forming light flux and bend it in a direction orthogonal to the optical axis of the rear lens group. With the second plane mirror, with zooming, the first plane mirror is moved in the direction of the rear lens group optical axis, and the second plane mirror is moved in the direction orthogonal to the rear group lens optical axis.
A variable-magnification photographic optical system having a moving mechanism for moving at the same time. 4. The variable magnification photographing optical system according to claim 1, wherein the back focus variable mechanism is capable of reflecting the image-forming light flux sequentially and bending in parallel with the optical axis of the rear lens group so that they are parallel to each other and swing. And the first and second plane mirrors arranged in the first and second plane mirrors are moved in a direction parallel to the optical axis of the rear lens group in the opposite directions in accordance with zooming, while maintaining a parallel relationship with each other. A variable magnification photographing optical system having a moving / rotating mechanism for rotating. 5. The variable magnification photographing optical system according to claim 1, wherein the back focus variable mechanism reflects the image-forming light flux and reflects it so as to bend it in a direction orthogonal to the optical axis of the rear group lens. And second and third plane mirrors that reflect the light flux reflected by the first plane mirror so as to be folded back by 180 degrees, and a third plane mirror.
A fourth plane mirror that reflects the light flux reflected by the plane mirror in the same direction as the imaging light flux that is incident on the first plane mirror, and fixes the first and fourth plane mirrors with zooming,
A variable magnification photographing optical system comprising: a moving mechanism that integrally moves the second and third plane mirrors in a direction orthogonal to the optical axis of the rear lens group. 6. A variable magnification photographing optical system having at least a front lens group and a rear lens group, wherein the front lens group and the image forming surface are fixed, and the optical path length from the front lens group to the image forming surface is changed. It has a back focus variable mechanism that performs zooming by moving the rear lens group, and changes the optical path length by the back focus variable mechanism according to zooming so that the image forming position always matches the image forming plane. A variable-magnification photographic optical system configured as described above. 7. The variable magnification photographing optical system according to claim 6, wherein the back focus variable mechanism is arranged so as to sequentially reflect the image-forming light beam and turn the optical path of the image-forming light beam by 180 degrees. And a moving mechanism for integrally moving the two flat mirrors in a direction parallel to the optical axis of the rear lens group with zooming. 8. The variable magnification photographing optical system according to claim 6, wherein the back focus variable mechanism is arranged so as to sequentially reflect the image-forming light flux and bend it in a direction orthogonal to the optical axis of the rear lens group. With the second plane mirror, with zooming, the first plane mirror is moved in the direction of the rear lens group optical axis, and the second plane mirror is moved in the direction orthogonal to the rear group lens optical axis.
A variable-magnification photographic optical system having a moving mechanism for moving at the same time. 9. The variable magnification photographing optical system according to claim 6, wherein the back focus variable mechanism is capable of reflecting the image-forming light beam in order and bending in a direction parallel to the optical axis of the rear lens group so that they are parallel to each other and swing. And the first and second plane mirrors arranged in the first and second plane mirrors are moved in a direction parallel to the optical axis of the rear lens group in the opposite directions in accordance with zooming, while maintaining a parallel relationship with each other. A variable magnification photographing optical system having a moving / rotating mechanism for rotating. 10. The variable magnification photographing optical system according to claim 6, wherein the back focus variable mechanism reflects the image-forming light flux and bends it in a direction orthogonal to the optical axis of the rear lens group. And second and third plane mirrors that reflect the light flux reflected by the first plane mirror so as to be folded back by 180 degrees, and a third plane mirror.
A fourth plane mirror that reflects the light flux reflected by the plane mirror in the same direction as the imaging light flux that is incident on the first plane mirror, and fixes the first and fourth plane mirrors with zooming,
A variable magnification photographing optical system comprising: a moving mechanism that integrally moves the second and third plane mirrors in a direction orthogonal to the optical axis of the rear lens group.