JPH10161189A - Real image type finder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the portability of a camera to reduce the outside dimension of the camera at the time of carrying it by setting plural reflection mirrors, out of reflection mirrors constituting a catoptric system for erectly observing the real image of a subject formed by an objective lens through an ocular, as movable plane reflection mirrors. SOLUTION: After luminous flux which forms the real image Z2 is reflected by the 2nd to the 4th plane reflection mirrors M2 to M4, it passes through the ocular L2 and reaches an eye point EP. The mirrors M2 to M4 are movably mounted on a camera main body, and the outside dimension (height) of the camera is reduced by moving the mirrors to a position where a distance from the optical axis of the ocular L2 to the upper ends of the mirrors M2 and M3 and a distance from the optical axis of the ocular L2 to the upper end of the mirror M4 are shortened when the camera is not used. Thus, the portability of the camera is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a real image type finder used for a video camera, an electronic camera, a single-lens reflex camera, a compact camera and the like.

[0002]

2. Description of the Related Art A conventional real image finder is shown in FIGS.
It will be described based on. FIG. 6 is a diagram showing an example of an optical system of a real image type viewfinder of a conventional single-lens reflex camera. FIG.
At the time of photographing, the plane reflecting mirror M1 has moved to the position shown by the two-dot chain line, and the luminous flux emitted from the subject at the time of photographing is affected by the objective lens (photographing lens) L1.
An inverted real image Z1 of the subject is formed on the photosensitive surface of the film F.

In the non-photographing mode, a flat reflecting mirror M1 is used.
Is at the position shown by the solid line, and the luminous flux emitted from the subject at the time of non-shooting passes through the objective lens L1 and then passes through the plane reflecting mirror M1.
To form a real image Z2 of the subject on the imaging surface of the reticle S at a position conjugate with the photosensitive surface of the film F. The light beam forming the real image Z2 is reflected three times by the penta roof prism P, and then reaches the eye point EP through the eyepiece L2. Therefore, the photographer can observe the erect image of the subject.

FIG. 7 is a view showing an example of an optical system of a conventional real-image finder of a compact camera. FIG.
In, after passing through the objective lens L1, the light beam emitted from the subject is bent in a right angle direction by the first plane reflecting mirror M1, and after passing through the field lens FL, forms a real image Z of the subject. The light beam forming the real image Z is reflected by the second, third and fourth plane reflecting mirrors M2, M3 and M4, and then passes through the eyepiece L2 to reach the eye point EP. Therefore, the photographer can observe the erect image of the subject similarly to the observation by the real image type viewfinder of the single-lens reflex camera.

[0005]

However, in the above-described conventional real-image finder, the penta roof prism P in the real-image finder of the single-lens reflex camera is also the second and third planes in the real-image finder of the compact camera. The reflecting mirrors M2 and M3 are both fixed to the camera body in a non-movable state, which causes the external dimensions of the camera to be constantly increased, which is a factor that impairs the portability of the camera.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a real-image finder that can reduce the external dimensions of a camera when the camera is carried to improve the portability of the camera.

[0007]

In order to achieve the above object, a real image finder according to the present invention comprises a reflection optical system for observing a real image of a subject formed by an objective lens through an eyepiece upright. At least two of the mirrors
One reflecting mirror was a movable flat reflecting mirror.

[0008]

Embodiments of the present invention will be described below. FIGS. 1 and 2 are diagrams showing an optical system of a real image finder according to a first embodiment in which claim 1 of the present invention is applied to a single-lens reflex camera. In FIG. 1, a luminous flux emitted from a subject during non-shooting is an objective lens (shooting lens) L1.
After being passed through the first plane reflecting mirror M1, it is bent upward at a right angle to form a real image Z2 of the subject on the focusing screen S at a position conjugate with the photosensitive surface of the film F.
The light beam forming the real image Z2 is reflected by the second, third and fourth plane reflecting mirrors M2, M3 and M4, and then reaches the eye point EP through the eyepiece L2. Therefore, the photographer can observe the erect image of the subject.

Here, the second, third and fourth plane reflecting mirrors M2, M3 and M4 are respectively mounted on the camera body in a movable state. When the camera is not used, as shown in FIG. Distance H1 from the optical axis of eyepiece L2 to the upper end of each of second and third plane reflecting mirrors M2 and M3
And the fourth plane reflecting mirror M4 from the optical axis of the eyepiece L2.
By moving the camera to a position where the distance H2 to the upper end of the camera is shortened, the external dimensions (height) of the camera can be reduced.

FIGS. 3 and 4 show the optical system of a real image type finder according to a second embodiment in which the second aspect of the present invention is applied to a single-lens reflex camera. In FIG. 3, a luminous flux from a subject passes through an objective lens (photographing lens) (not shown) and a first flat reflecting mirror (not shown), and a focusing plate S
A real image Z of the subject is formed on the top. And the real image Z
After passing through the field lens FL,
The light is reflected by the second and third plane reflecting mirrors M2 and M3 and the prism P as a fourth reflecting means, and the eyepiece L2
And reaches the eye point EP. Therefore, the photographer can observe the erect image of the subject.

Further, each of the second and third plane reflecting mirrors M2,
M3 is movably attached to the camera body, and when the camera is not used, as shown in FIG. 4, from the optical axis of the eyepiece L2 to the upper ends of the second and third plane reflecting mirrors M2 and M3. By moving the camera to a position where the distance H1 is shortened, the external dimensions (height) of the camera can be reduced.

The above is the same as the first embodiment shown in FIGS. 1 and 2, but in the second embodiment, the prism P is used as the fourth reflecting means in order to obtain the following effect. Further, the entrance surface of the prism P is a curved surface to have a positive refractive power. That is, the conventional finder optical system shown in FIG. 6 uses the penta roof prism P to reduce the area of the reflection surface and to cross the optical path to shorten the optical path length, thereby reducing the size of the finder. The optical system of the second embodiment of the finder according to the present invention shown in FIG. 4 differs from the optical system of the conventional finder in that it has a wide reflecting surface capable of individually reflecting the entire light beam to the eyepiece L2. Although a long optical path length using the plane reflecting mirrors M2 and M3 is required, the optical path length between the real image Z and the eyepiece L2 is longer than when the fourth reflecting means is a plane reflecting mirror. The viewfinder magnification is set to 4th
While keeping the reflecting means of a flat reflecting mirror,
The distance between the real image Z and the eyepiece L2 can be increased, and the space for arranging the members constituting the reflection optical system can be increased.

Further, in the finder optical system of this embodiment, by making the entrance surface of the prism P a positive refraction surface, a position closer to the real image can be obtained as compared with the case where a prism having a plane entrance surface is arranged. Has a positive refractive power. As a result, a higher finder magnification is obtained as compared with the case where a prism having a flat incident surface is arranged.

[0014]

FIG. 5 is a diagram showing an optical system of a third embodiment in which the real image type finder according to the present invention is applied to a compact camera. In FIG. 5, an objective lens L1, first, second and third plane reflecting mirrors M1, M2 and M3,
The optical system using the prism P and the like is basically the same as the optical system of the second embodiment. However, in this embodiment, the width (dimension in the left-right direction) of the camera when not used is reduced. It is an example.

That is, in FIG. 5, a light beam emitted from a subject during non-photographing passes through an objective lens L1 and is then bent rightward by a first plane reflecting mirror M1 to form a real image Z of the subject. . The luminous flux forming the real image Z reaches the eye point EP after being reflected by the second and third plane reflecting mirrors M2 and M3 and the prism P. Here, each of the second and third plane reflecting mirrors M2 and M3 is movably attached to the camera body, and when the camera is not used, as shown in FIG.
The outer dimensions (width) of the camera can be reduced by moving to a position where the distance H from the first optical axis to the right ends of the second and third plane reflecting mirrors M2 and M3 is shortened.

Further, in the present embodiment, both the entrance surface and the reflection surface of the prism P are curved surfaces having a positive refractive power to substitute for the function of the eyepiece, and the eyepiece is omitted.

[0017]

According to the real image type finder of the present invention,
When the camera is not used, the external dimensions of the camera can be reduced, so that the portability of the camera can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a finder optical system according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a moving state of a movable flat reflecting mirror of the finder optical system according to the first embodiment of the present invention.

FIG. 3 is a diagram illustrating a finder optical system according to a second embodiment of the present invention.

FIG. 4 is a view showing a moving state of a movable flat reflecting mirror of a finder optical system according to a second embodiment of the present invention.

FIG. 5 is a view showing a finder optical system according to a third embodiment of the present invention and a moving state of a movable plane reflecting mirror of the finder optical system.

FIG. 6 is a diagram showing an example of an optical system of a real image type viewfinder of a single-lens reflex camera according to a conventional technique.

FIG. 7 is a diagram showing an example of an optical system of a real image type finder of a compact camera according to a conventional technique.

[Explanation of symbols]

 L1 ‥‥ Objective lens M1 ‥‥ First plane reflector M2 ２Second plane reflector M3 ‥‥ Third plane reflector M4 ４Fourth plane reflector S ‥‥ Focus plate P 板 Prism L2 eyepiece

Claims (2)

[Claims] 1. A real image type viewfinder for observing a real image of a subject formed by an objective lens through an eyepiece, wherein a reflection optical system for observing the real image upright through the eyepiece is independently provided by the reflection optical system. A real image type comprising a plurality of plane reflecting mirrors having an area capable of reflecting the entire light beam to the eyepiece, wherein at least two of the plane reflecting mirrors are movable plane reflecting mirrors. Viewfinder. 2. The real image type viewfinder according to claim 1, wherein a reflecting member closest to a pupil of a photographer among the reflecting members constituting the reflecting optical system is a prism.