JPS6152410B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a light splitting device for photometry in single-lens reflex cameras and the like.

2. Description of the Related Art Conventionally, there has been known a photometry method in a single-lens reflex camera in which a part or all of the reflective surface of a quick return mirror is made semitransparent, and the light beam transmitted therethrough is guided to a photoreceptor for photometry. For example, in 1977-
In No. 14445, a reflective film is formed in one direction on a transparent flat plate provided with a directional cut groove in a certain direction on the back surface of a semi-transparent quick return mirror.
A photometric device is disclosed in which light transmitted through the back surface of a quick return mirror is guided in a fixed direction.

However, in general, in order to maintain the brightness of the finder, it is not possible to reduce the luminous flux reflected toward the finder system, and for other reasons, it is desired to improve the light utilization efficiency in such photometry systems.

SUMMARY OF THE INVENTION An object of the present invention is to improve the conventional technology and provide a light splitting device for photometry with increased light utilization efficiency.

The structure and operation of the present invention will be explained below with reference to the drawings.

FIG. 1 is a sectional view of a camera having a light splitting device according to a first embodiment of the present invention. The light splitting device of this embodiment is a reflecting mirror that splits a luminous flux in terms of amplitude (for example, a semi-transparent mirror) or a reflecting mirror that splits a luminous flux in area with a mixture of transparent and reflective parts (for example, a mirror that splits a luminous flux in terms of area). It consists of a main mirror 1, such as a mirror with
The entire mirror is placed in the position of a conventional quick return mirror. In the figure, 3 is the photographic lens,
12 is a focus plate, and 13 is a pentaprism for a finder. Figure 2 shows how the luminous flux is split when a semi-transparent mirror is used as the main mirror 1, and how the split luminous flux is guided to the light-receiving element. The light beam 4 emitted in parallel is first reflected by the transflective surface 5 of the main mirror 1, and most of it is directed toward the finder system, and the light beam 6 that has passed through the main mirror is reflected by the small sub-mirror group 2 on the back surface of the main mirror. , guided to the light receiving element 8. As is clear from FIG. 2, in the photometry device of this example, in order to efficiently guide the light flux that has passed through the main mirror to the light receiving element, the direction of the surface of the microscopic submirror changes depending on its position on the back surface of the main mirror. ing. Figure 2 shows one cross section,
Furthermore, in order to improve the light condensing ability, when the back surface of the main mirror is viewed in plan, minute sub-mirrors are provided in a concentric circular arc shape with a certain point as the center. Figure 2 shows the case where a semi-transparent mirror is used as the main mirror, but when an area type mirror with many pinholes is used as the main mirror, the way the luminous flux is divided is as shown in Figure 3. Become. In FIG. 3, 9 is a completely reflective portion, and 10 is a transmittable pinhole region. In this case as well, the direction of the surface of the minute sub-mirror changes depending on the position of the back surface of the main mirror, as in the case of the semi-transparent mirror of the previous embodiment. In the above, the micro submirror is a plane mirror, but it is possible to further improve the light collection efficiency by using a curved mirror with an appropriate curvature within the cross section shown in FIGS. 2 and 3.

Generally, in a single-lens reflex camera, when a reflective mirror with some kind of transparency is used as the quick return mirror, during exposure, reverse light from the viewfinder side can enter through the flipped up quick return mirror. There is sex.
Also in the light splitting device of the present invention, since a transparent main mirror is used as a quick return mirror, there is a possibility that the above-mentioned reverse light from the finder may enter even when the mirror is flipped up. As a more reliable method for preventing such back-incoming light, when the quick-return mirror flips up, the sub-mirror can be rotated toward the main mirror using mechanical or electrical control (not shown in Figures 2 and 3). It is possible to fold it down and cover the transparent part of the main mirror completely or most of the transparent part. As a particularly preferred embodiment, when an area-type reflective mirror with many pinholes is used as the main mirror,
One submirror is provided corresponding to one or more pinholes, and when the main mirror (quick return mirror) flips up, the submirrors cover each pinhole, completely preventing reverse light from entering. can. The sub-mirror 7 shown in broken lines in FIG. 3 covers the pinhole. When using a reflecting mirror with semi-transparent mirrors in all areas as the main mirror, it is difficult to cover all of this area with sub-mirrors, but it is necessary to provide sub-mirrors densely or to make them partially semi-transparent in correspondence with the sub-mirrors. In the same manner as described above, it is possible to almost completely prevent reverse light from entering.

As shown in the description of the embodiments above, by using the light splitting device according to the present invention, it is possible to efficiently guide the photometric light flux from the photographing lens to the light receiving element. Furthermore, the size of the reflective surface of the microscopic submirror used in the light splitting device of the present invention,
By changing the shape, the location and density of the minute submirrors, it is possible to form light splitting devices having various photometric characteristics. For example, in camera photometry, in order to maintain f-number proportionality,
If it is necessary to reduce the amount of light near the optical axis, this purpose can be achieved by reducing the density of minute sub-mirrors provided in that area.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a camera having a light splitting device according to a first embodiment of the present invention. FIG. 2 is an enlarged sectional view of a portion thereof. FIG. 3 is an enlarged sectional view of a light splitting device according to another embodiment of the present invention. In the figure, 1 is the main mirror, 2 is the submirror, 3 is the photographic lens system, 4 is the light emitted from the photographic lens system, and 5
is a reflective surface, 6 is a ray of light transmitted through the main mirror, 7 is a submirror that has been flipped up, 8 is a light receiving element, 9 is a complete reflective surface, 10 is a pinhole, and 13 is a pentaprism.

Claims (1)

[Claims] 1. A light-receiving section is placed behind the reflecting mirror, and a part or all of the main reflecting surface of the reflecting mirror is used as a light splitting surface, and a microscopic light beam that passes through this is guided to the light-receiving section. A photometric light splitting device comprising a submirror group provided on the light splitting surface and the reflection side of the reflecting mirror, wherein each microscopic submirror in the microscopic submirror group has an inclination with respect to the split light beam depending on its installed position. A light splitting device for photometry that is characterized by a change in . 2. Claim 1, characterized in that each of the minute sub-mirrors is arranged concentrically with each other.
Light splitting device for photometry. 3. The light splitting device for photometry according to claim 1, wherein the reflecting surface of each of the minute submirrors is a light-converging curved surface. 4. A light receiving section is placed behind the reflecting mirror, and a part or all of the main reflecting surface of the reflecting mirror is used as a light splitting surface, and a group of minute sub-mirrors that guide the divided light flux passing through this to the light receiving section is arranged on the reflecting mirror. A photometric light splitting device provided on the opposite side of the light splitting plane, wherein each microscopic submirror in the microscopic submirror group has an inclination with respect to the split light beam that changes depending on its installed position, Each of the minute submirrors in the group of minute submirrors is rotatable around a predetermined axis, and is configured to rotate in conjunction with the movement of the reflecting mirror when it rises, thereby shielding the light splitting surface from light. A light splitting device for photometry that is characterized by: 5. The fourth aspect of the present invention is characterized in that the light splitting surface is an area-type light splitting surface in which a transparent part and a reflective part are mixed, and the minute sub-mirrors are arranged corresponding to each transparent part. Light splitting device for photometry.