JPS6210414B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention provides a TTL photometry device for a single-lens reflex camera;
Especially the pentaprism (hereinafter simply referred to as penta).
The present invention relates to an improvement of a photometric device in which a light receiving element is provided on either the left or right side of an eyepiece lens facing the back surface of the eyepiece.

As the above-mentioned TTL photometry device for a single-lens reflex camera, a photometry device in which a light receiving element made of a Si--GaAs diode or the like is provided above an eyepiece lens facing the back surface of a pentameter is known.

In such a conventional photometry device, light incident through a photographic lens passes through a focusing plane and a field frame, and enters a penta 2 from an incident surface A, as shown by the thin arrow line in FIG. It is configured such that it is reflected by the front reflective surface C and enters the eyepiece 3 provided opposite the back surface D, and also enters the light receiving element 4. 3 receives light from the entire area of the field frame 5, whereas the light receiving element 4 has a dotted hatched optical path range that is kicked by the front triangular surface of the penta 2, so the field frame portion corresponding to that range is It was as shown in Fig. 2, in which light from the field frame excluding the field frame was incident. That is, FIG. 2 shows the entire field frame, of which the light from the top portion indicated by dotted diagonal lines does not enter the light-receiving element 4, and the light from the lower portion below enters the light-receiving element.
The effect on the photovoltaic force of the light-receiving element is not uniform, and the effect is stronger toward the center, which is slightly closer to the top.

In a single-lens reflex camera equipped with such a conventional photometry device, a subject such as a landscape is photographed under conditions such that the top area indicated by the dotted diagonal line in Figure 2 hits the top space of the background. In some cases, you may be able to take a picture with the correct exposure based on the photometry information, but if you are shooting indoors against a background with uniform brightness, or especially when shooting against a landscape with the camera on its side, you may be able to take pictures with the appropriate exposure based on the photometry information. If you set the exposure conditions in the same way, you will not be able to take pictures with proper exposure.

The present invention has been made to solve the above-mentioned problems, and allows proper exposure to be taken based on photometric information even when shooting indoors with a uniform brightness background or when shooting with the camera tilted on its side. It provides a TTL photometry device for single-lens reflex cameras.

The present invention is a TTL photometry device for a single-lens reflex camera in which a light-receiving element is provided on either the top or left or right side of the eyepiece facing the back of the penta, in which light from the entire field of view of the penta enters the photometry element. The reflecting surface of any one of the pentameters corresponding to the range of the light path of incidence to the photometric element is configured such that the reflected light decreases as it moves away from the range of the light path of incidence to the eyepiece lens. This is found in the TTL metering device of single-lens reflex cameras.

That is, the photometry device of the present invention can change the shape of the penta from the conventional shape shown in FIG. is expanded as shown by the dotted line, and the front triangular surface E is accordingly reduced in shape as E', thereby allowing light from the entire field of view frame 5 to enter the light receiving element 4. , the front reflective surface C of the penta having such a shape
can be obtained by adhering a reflective metal film M having a shaded shape as shown in FIG. In FIG. 4, B and E' are the same roof surface and front triangular surface of the pentagram 2 as shown in FIG. part, C
Reference numeral 2 denotes a portion outside the range of the optical path of incidence to the eyepiece lens and corresponding to the range of the optical path of incidence to the photometric element. As mentioned above, by making the shape of the penta so that light from the entire area of the field frame 5 is incident on the light receiving element 4, as shown in FIG. The areas that were not covered are now as shown in Figure 3. However, if this is done alone, the influence of the field frame portion that has not been incident on the light-receiving element will be too strong, and if a photograph is taken based on such photometric information, there is a risk of underexposure. The solution to this fear is the front reflective surface shown in Figure 4.
By making the edge of the C2 portion of the reflective metal film M into a serrated or comb-like shape, the reflected light at the C2 portion is attenuated as it goes away from the C1 portion and enters the light receiving element. The relative strength distribution of the influence of light from the field frame portion on the photovoltaic force of the photodetector is corrected as shown in FIG. 5, so that the photodetector provides photometric information that provides proper exposure. Since light from the entire field frame enters the light-receiving element, the photometry conditions do not change significantly even if the camera is placed on its side to take pictures, and accordingly, pictures are taken with appropriate exposure based on the photometry information in the same way. Further, since the serrated or comb-toothed edges of the reflective metal film M as shown in FIG. 4 are outside the range of the incident light path to the eyepiece, they do not affect the desired field frame from the eyepiece. The reflective metal film M in FIG. 4 is produced by coating the serrated white parts and the front triangular surface with a sheet such as a film, and applying a metal such as aluminum to the exposed part using a known method such as vacuum evaporation or cathode sputtering. It is provided by gluing by means of.

The present invention is not limited to the above-mentioned example, and the light-receiving element is provided on either the left or right side of the eyepiece, and the pentameter is configured so that light from the entire field frame is incident on the light-receiving element accordingly. Even if it is a pentagonal roof surface, the reflective surface that is out of the optical path of incidence to the eyepiece and hits the optical path of incidence to the photometric element is the roof surface of the penta, and the roof surface has a sawtooth shape or a shape as shown in Fig. 4. Even if a reflective metal film with a comb-toothed edge is bonded, or even if the serrated or comb-toothed edge is straight rather than curved as shown in FIG. A hole that does not have a comb-like edge and that is located outside the optical path of incidence to the eyepiece and corresponds to the optical path of incidence to the photometric element, and that gradually increases or decreases so that the transmittance of light increases as it leaves the optical path of incidence to the eyepiece. It may also have a vapor deposition density of

[Brief explanation of the drawing]

Fig. 1 is a side view showing the incident optical path of the photometric device, Fig. 2 is a schematic diagram showing the field frame seen from the light receiving element in the conventional photometric device, and Fig. 3 is light reception when using the pentameter according to the present invention. FIG. 4 is a front view of a pentagram showing an example of a reflective surface, and FIG. 5 is a schematic diagram showing a field frame as seen from the light receiving element in the present invention. 1... Incident light, 2... Penta, 3... Eyepiece, 4... Light receiving element, 5... Field frame, A... Incident surface, B... Roof surface, C... Front reflective surface, D back surface. ,
E, E'...front triangular surface.

Claims (1)

[Claims] 1. A TTL photometry device for a single-lens reflex camera in which a light-receiving element is provided on either the top or the left or right side of an eyepiece facing the back surface of a pentaprism, which uses the pentaprism to capture light from the entire field frame. The reflecting surface of the pentagonal prism corresponding to the optical path range of incidence on the photometric element is configured so that the reflected light can be incident on the photometric element, and the reflected light is attenuated as it moves away from the optical path range of incidence on the eyepiece lens. A TTL photometry device for a single-lens reflex camera, which is characterized by being configured as follows. 2. The TTL photometry device for a single-lens reflex camera according to claim 1, wherein the front reflective surface of the pentaprism is provided with a reflective surface that reduces the reflected light as the distance from the incident optical path range to the eyepiece increases. 3. Claim 1 or 3, wherein the reflecting surface, in which the reflected light decreases as it goes away from the range of the incident optical path to the eyepiece, is an adhesive surface of a metal film whose edges are formed in a serrated or comb-like shape. The single-lens reflex camera described in Section 2
TTL photometer. 4. The TTL photometry device for a single-lens reflex camera according to claim 3, wherein the serrated or comb-like edges are curved in a mid-height direction.