JPH0446327A - Photometric device - Google Patents

Abstract

PURPOSE:To take out and measure only the brightness in the peripheral part of a photometric region by providing a light shielding means which shields the incidence of the light from a specified region of the photometric region to the front of a photodetecting surface of a photodetector. CONSTITUTION:The light from the peripheral part, i.e. the range between theta1 and theta3 of the light from the photographing range of a camera is made incident through a photometrix aperture 2 of the 1st photometric device A on the photodetecting surface 4a of a photodetector 4. The light from the peripheral part is measured exclusively by the 1st photometric device. On the other hand, the light from the central part, i.e. the range of theta2 of the light form the photographing range of the camera is made incident through a photometric aperture 6 of the 2nd photometric device B on the photodetecting surface 7a of a photodetector 7. Then, the light from the central part is measured exclusively by the 2nd photometric device. The 1st photometric device dividedly measures only the peripheral part of the photographing range of the camera, i.e. the photometric region. The 2nd photometric device dividedly measures only the central part of the photometric region. The results of the measurement by the respective photometric devices are compared and evaluated, by which the exposure correction, such as rear light correction, is executed.

Description

DETAILED DESCRIPTION OF THE INVENTION a. Field of Industrial Application This invention relates to an improvement in a photometry device that measures the brightness of a subject in order to determine exposure.
The present invention relates to a photometry device that extracts and measures only the brightness in the peripheral area of a photometry area.

b. Prior Art For example, when photographing with a camera, exposure correction is required when the subject is under backlight.

Conventionally, methods called split photometry and evaluation photometry (hereinafter simply referred to as "split photometry") have been used as a method for automatic exposure correction in cameras. Split metering is the process of dividing the photometry area corresponding to the shooting range into 2 to 6 areas, measuring the brightness of each divided area individually, and comparing and evaluating the measurement results to make exposure compensation. , which attempts to automatically obtain appropriate exposure.

Conventionally, the photometry device used for this divisional photometry uses a light-receiving element that corresponds to each area to be divided and has a mutually independent light-receiving range. It is placed at the same position as the photographic film above, or placed behind a light-receiving window independent of the photographic optical system, so that light from each area is incident on the corresponding light-receiving range of the light-receiving element. Met.

C1 Problems to be Solved by the Invention However, as described above, the light-receiving element used in the conventional photometric device had to have a special shape having mutually independent patterns of light-receiving ranges. Also, as mentioned above, a light receiving element with a certain division pattern is
Since it is designed exclusively for photometric devices that require such a division pattern, it cannot be used for photometric devices that require a different division pattern, and thus lacks versatility. Therefore, a photometric circuit using this has a problem in that the cost is excessive.

For example, when dividing the photometry area into two and performing split photometry, two independent photometers are used, and one of them measures the overall brightness of the entire photometering area. In addition, it is also conceivable to compare the measurement results of both photometers so that the other one measures the brightness only in the center of the photometering area.

However, in such photometric devices, one photometric device that measures the entire photometric area as a whole will measure light including the center area, which is independently measured by the other photometric device, so the photometric result will be the same as that of the photometric area. It does not respond to the brightness of my surroundings. Therefore, the difference in output between the two-sided optical devices is smaller than the difference in actual brightness between the center and the periphery of the photometric area. Therefore, there are problems in that it is difficult to use as data for automatic exposure correction using split photometry, or that a processing step is required to obtain a value that corresponds only to the brightness of the peripheral area.

The present invention has been made in view of these conventional problems, and an object of the present invention is to provide a photometry device that has a simple configuration and can perform photometry by extracting only the brightness at the peripheral part of the photometry area. In order to achieve the above-mentioned object, the photometry device according to the present invention has a photometry system that measures external brightness by receiving external light incident through an aperture using a light receiving element. The apparatus is characterized in that a light blocking means is provided in front of the light receiving surface of the light receiving element for blocking light from a certain area of the light from the photometric area from entering the light receiving surface.

e. Structure of Embodiment Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing an embodiment of the present invention. This embodiment shows an embodiment in which a photometric device according to the present invention is built inside a camera body.

First, to explain the configuration, 1 is the front cover of the camera,
2 was punched in cover 1 the other day'! 11 photometric apertures,
Reference numeral 3 denotes a circular light-shielding portion constructed as a part of the front cover 1 and placed in the center of the photometric aperture 2; 4, for example, a 5PD (5PD) fixed on a circuit board 5 provided within the camera body;
The first light-receiving element is a silicon photodiode (silicon photodiode).

Here, as shown in the front view in FIG. 2, the first photometric aperture 2 has a substantially annular aperture shape because it has a circular light shielding part 3 in the center. Also.

By each step part 2a for preventing the light shielding part 3 from falling off and holding it on the front cover 1 of the camera.

The photometric aperture 2 is divided into four parts.

These first photometric apertures 2. Light shielding part 3. The first photometric device A according to the present invention is configured by the first photodetector 4, and the amount of external light incident on the photodetector surface 4a of the photodetector 4 through the photometric aperture 2 is received by the photodetector 4. converted into an electrical signal that spreads to

It is used in an automatic exposure control device (not shown) or the like to determine the brightness of its photometric area.

This first photometry device A is tasked with the function of photometering the peripheral portion of the photographing range of the camera. Therefore, the light-receiving angle θ1 needs to be set to approximately match the photographing range of the camera. The light receiving angle θ1 is determined by the inner diameter ch of the first photometric aperture 2 and the light receiving surface 4 of the first light receiving element 4.
Outer diameter Yl of a, from surface 1a of front cover 1 to light receiving surface 4
It can be defined as follows by the distance 1lx1 to a.

Next, 6 is a photometric opening s2 bored in the front cover 1, and 7
Similarly to the first light receiving element 4, the light receiving element @2 is fixed on a circuit board 5 provided within the camera body and is made of, for example, an SPD (silicon photo diode). Here, the second photometric aperture 6 is the same as the first photometric aperture 2.
Unlike this, it does not have a light shielding part. The second photometric aperture 6 and the light receiving element 7 of j12 constitute the photometric device B of j12, and as in the case of the photometric device A of 111 above, external light incident on the light receiving surface 7a is converted into an electrical signal. This second photometry device B is used to determine the brightness of the photometry area in an automatic exposure control device (not shown), etc. This second photometry device B divides the central part of the camera's shooting range from the peripheral part. It has the function of measuring light.

Therefore, the light-receiving angle θ2 needs to be set narrower than the light-receiving angle θ2 of the photometer A of 11. This light receiving angle θ2 is determined by the inner diameter d2 of the second photometric aperture 6. The outer diameter Y2 of the light receiving surface 7a of the second light receiving element 7 can be defined as follows from the distance x2 from the surface 1a of the front cover 1 to the light receiving surface 4a.

However, in order for each of the photometers A and B to measure the camera's shooting range, that is, the photometering area, by dividing it into the peripheral area and the center area as described above, it is necessary to It is necessary to make the limit, that is, the light-blocking angle θ3 by the light-blocking part 3 coincide with the light-receiving angle θ2 of the photometer B. Therefore, in order to satisfy this condition, the thickness of the front cover 1 should be set to 2. The diameter d3 of the light shielding part is set as follows.

f. Effect of the embodiment Next, the operation of the embodiment configured as described above will be explained.

Of the light from the camera shooting range, the shoulder side, i.e. θ1 and 0
The light from the range between 3 and 3 passes through the photometric aperture 2 of the first photometric device A and enters the light receiving surface 4a of the light receiving element 4.

However, since this θ3 matches θ2, this range is outside the photometry range θ2 of the second photometry device B, and light from this range is transmitted to the front cover 1 of the camera around the second photometry aperture 6. The light is blocked by the light receiving element 7 and does not enter the light receiving surface 7a of the second light receiving element 7. Therefore, light from this peripheral area is exclusively photometered by the first photometer.

On the other hand, out of the light from the camera shooting range, the central part, that is, θ2
The light from the range passes through the photometric aperture 6 of the second photometric device B and enters the light receiving surface 7a of the light receiving element 7. However, as mentioned above, since this θ2 matches θ3, this range matches the range that is blocked by the light shielding plate 3 of the first photometric device A, and the light from this range is transmitted to the light receiving element 4 of Ill.
The light does not enter the light receiving surface 4a. Therefore, light from this center is exclusively photometered by the second photometer.

As described above, the first photometric device divides and measures only the peripheral portion of the photographing range of the camera, that is, the photometric area, and the second photometric device divides and measures only the central portion of the photometric area. Exposure correction such as backlight correction is then performed by comparing and evaluating the photometry results from each photometry device.

Note that the present invention is not limited to the embodiments described above, and various modifications are possible. For example, the second photometry device B is not necessary in a device that performs exposure control by measuring only light from the periphery while excluding light from the center. On the other hand, I! When dividing the I light area into three or more,
It is sufficient to use three or more photometric devices each having a different photometric range.

Further, a cover glass may be placed in each opening, in which case it is possible to prevent dust and the like from entering the inside of the photometric device.

Further, a condenser lens may be arranged in each aperture. In that case, even if the light-receiving surface is made small, a sufficient amount of light can be made incident on the light-receiving surface.

Also, put a light shielding plate on the opening! ! 2) A slightly larger light-receiving element may be used, and a light-shielding member may be placed on the surface of its light-receiving surface or in the center of the optical path between the aperture and the light-receiving surface.In that case, Ua may be annular. Since it is not necessary to use a cover glass or a lens, it is easy to manufacture, and since the opening can be sandwiched, it is possible to make it difficult for dust and the like to enter the inside of the photometric device even without a cover glass or lens.

Furthermore, although this embodiment describes the case where the present invention is applied to a camera, the present invention is not limited to this.
The present invention can be applied to any optical device 2 that requires a light receiving device, such as a hand-held exposure needle.

Effects of the Invention As described above, according to the present invention, in a photometry device that measures external brightness by receiving external light incident through an aperture with a light receiving element, a light receiving surface of the light receiving element is provided. Since a light shielding means is provided to prevent light from a certain range of light from entering the photometry area from entering the light receiving surface, it is possible to perform photometry by extracting only the brightness of the peripheral part of the photometry area with a simple configuration. I can do it.

[Brief explanation of the drawing]

FIG. III is a sectional view showing an embodiment of the present invention. Figure 1112 is a front view of the main parts of the present invention. 2: First photometric aperture 3: Light shielding plate 4: First light receiving element Ryo Ganjin Asahi Optical Industry Co., Ltd.

Claims (1)

[Scope of Claims] 1. In a photometry device that measures external brightness by receiving external light incident through an aperture with a light receiving element, a portion of the light from the photometry area is placed in front of the light receiving surface of the light receiving element. A photometric device comprising a light blocking means for blocking light from a certain area from entering the light receiving surface. 2. The photometric device according to claim 1, wherein the light blocking means blocks light corresponding to a central portion of the light from the photometric area from entering the light receiving surface. 3. The photometric device according to claim 1 or 2, wherein the light shielding means is provided in the opening. 4. The side light device according to claim 3, wherein the light shielding means has an annular shape. A photometric device characterized in that it is configured as a light-shielding section surrounded by a slanted aperture. 5. In a photometry device that measures external brightness by receiving external light incident through an aperture with a light receiving element, in front of the light receiving surface of the first light receiving element, out of the light from the photometry area, a certain area of light is detected. A first photometric device is provided with a light shielding means for blocking light from entering the light receiving surface of the first light receiving element, and a second aperture and a second light receiving element are used to detect the certain range of light from the photometric range. a second photometric device that allows only light from the second photometric device to enter the light-receiving surface of the second light-receiving element.