JPH0380232A - Photometric device - Google Patents

Abstract

PURPOSE:To allow spot metering in a narrow range by setting the ratio of the spot metering range for the center photographing range smaller than the are ratio of the spot metering photodetecting part to the average metering photodetecting part of a photometric sensor. CONSTITUTION:The luminous flux P1 at the center of a finder visual field (the visual field rate of the finder is usually 70 to 80% of the photographing picture) images at the center of the spot metering photodetecting part 10A of the photometric sensor 10. The luminous flux P2 on the contour of the spot metering range of the photographing picture (range of 5% of the center of the photographing picture) images at nearly the boundary position of the spot metering photodetecting part 10A and its peripheral photodetecting part 10B. Namely, the luminous flux within the spot metering range eventually enters the spot metering photodetecting part 10A. On the other hand, the luminous fluxes off the spot metering range eventually enter nearly the photodetecting part 10B but the luminous fluxes P4 at the top and bottom ends (V end) of the finder visual field deviate from the photodetecting part 10B. The information on the spot metering range (5% of the center of the photographing image plane) is obtd. in this way at the time of the spot metering.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a photometric device, and particularly to a photometric device that performs average photometry and spot photometry.

[Conventional technology]

FIG. 9 is a plan view of a light receiving section of a photometric sensor that performs average photometry and spot photometry. In the figure, average photometry measures the light of the entire screen that enters the light receiving sections 10A and 10B of the photometric sensor 10, and spot photometry measures the light that enters the central light receiving section (spot photometry light receiving section) 10B of the screen. It measures the light in the center only.

Incidentally, spot photometry requires the photometry range to be narrow (for example, about 5% of the total shooting range), but conventionally, the ratio of the spot photometry range to the entire shooting range is the spot photometry light receiving section 10B relative to the average photometry receiving section. It was determined uniquely by the area ratio of

[Problem to be solved by the invention]

However, when using a commercially available photometric sensor,
As described above, since the ratio of the spot photometry range to the entire photographing range is uniquely determined by the sensor area ratio of the spot photometry light receiving section, there is a problem in that it is not possible to measure the spot photometry range at a desired ratio. In addition, when designing and manufacturing a new photometric sensor that can perform photometry in the spot photometry range with the desired ratio, the cost of the photometry sensor increases, and if the spot photometry receiver is made too small, good signal output may not be obtained. The problem is that there is no.

The present invention has been made in view of the above circumstances, and it is possible to realize spot photometry in a spot photometry range of a desired ratio, regardless of the area ratio of the spot photometry light receiving section to the average photometry light receiving section of the photometry sensor. The purpose is to provide a photometric device.

[Means to solve problems]

In order to achieve the above object, the present invention provides a two-divided photometric sensor having a spot photometric photoreceptor that performs spot photometry in the center of an average photometric photoreceptor that performs average photometry, the average photometric photoreceptor that performs spot photometry. A photometric sensor in which the area ratio of the spot photometry light receiving part to the total shooting range is larger than the ratio of the spot photometry range to the entire shooting range, and the light flux outside the spot photometry range is guided to the spot photometry light receiving part of the photometry sensor, and the light flux outside the spot photometry range is is characterized by comprising a photometric optical system that weights and guides light receiving sections other than the spot photometric light receiving section.

[Effect]

According to the present invention, for example, a commercially available mass-produced photometric sensor is used, and the ratio of the spot photometric range to the entire shooting range is made smaller than the area ratio of the spot photometric light receiving section to the average photometric light reception in the photometric sensor. That's what I do. That is, the photometry optical system guides the light flux within the spot photometry range to the spot photometry light receiving section of the photometry sensor, and the light flux outside the spot photometry range is guided to the light receiving section other than the spot photometry section in a weighted manner, thereby performing spot photometry. It is possible to perform average photometry and to perform spot photometry in a narrower range than the conventional spot photometry range by the photometry sensor.

〔Example〕

Preferred embodiments of the photometric device according to the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is an exploded perspective view of a finder unit in which a photometric device according to the present invention is installed. In the figure, a cemented prism 22 formed by joining four triangular prisms is housed in the finder main body 20, and the cemented prism 22 receives light within a predetermined field of view of the finder via the objective lens 24 of the finder. incident. The light incident on the cemented prism 22 is guided to an eyepiece lens 26 disposed at the rear of the finder main body 20.

Further, a part of the light incident on the cemented prism 22 is guided to a photometry system housed in the side of the finder body 20. In this photometry system, two AE lenses 12 and 14 with a spacing ring 13 in between, an aperture slope 15, a sensor frame 16 in which a photometry sensor 10 is arranged, and a shield case 17 are arranged in sequence on the side of a finder main body 20. It is fixed with set screws 18 and 18, and performs spot photometry and average photometry.

Now, Figure 2 shows the lens 12, 14 and the photometric sensor 1.
This is a side view of the lens 12, in particular, the lens surface on the right side in FIG.
It is a bifocal lens having an outer spherical surface 12B. Further, the photometric sensor 10 has a light receiving 110 as shown in FIG.
A. Has IOB.

Next, the inner spherical surface of the lens I2! 2A and lens 14
The light flux that enters the photometric sensor 10 via the light beam will be explained.

In Fig. 3, the luminous flux P at the center of the viewfinder field of view (the viewfinder field of view is usually 70 to 80% of the shooting screen)
1 is imaged at the center of the spot photometric light receiving 10A of the photometric sensor 10. In addition, the light flux P2 on the contour of the spot photometry range of the photographing screen (in this embodiment, the central 5% range of the photographic field) is located almost at the boundary position between the spot photometry light receiving section 10A and the surrounding light receiving section 10B. The image b, that is, the light beam within the spot photometry range enters the spot photometry light receiving section 10A.

On the other hand, the light beam outside the spot photometry range is
However, the light beam P4 on the upper and lower ends (V completion) of the finder field of view comes to deviate from the light receiving section 10B.

Next, the outer spherical surface 12B of the lens 12 and the lens 14
The light flux that enters the photometric sensor 10 via the light beam will be explained.

In FIG. 4, among the light fluxes outside the spot photometry range, for example, the light flux P3 shown in FIG. The light also enters the portion 10A. Note that since this amount of incident light is small, it hardly affects spot photometry.

Further, the outer spherical surface 12 has a larger curvature than the inner spherical surface 12A.
The light beam P4 on the V end that passes through B is incident on the light receiver 810B. Furthermore, part of the light beam P5 on the left and right ends (H end) of the finder field of view is also received! ! '[Input to 5 IOB.

5vgJ and FIG. 6 are graphs showing the distribution of light incident on the photometric sensor 10 as described above, where the solid line represents the average photometry, and the broken line represents the spot photometry.

As is clear from these graphs, when using average metering, you can obtain information about the luminous flux over the entire viewfinder field of view, and when using spot metering, you can obtain information about the spot metering range (the central 5% of the shooting screen). . Note that during spot photometry, a light flux outside the spot photometry range (see light flux P3 shown in FIG. 4) is also photometered, but this light flux is small.

FIGS. 7 and 8 are diagrams showing other embodiments of the present invention, respectively. In FIG. 7, the AE lens 30 is configured such that its image plane is curved as shown by reference numeral 30A.

As a result, compared to the light that enters the spot photometry light receiving section 10A, the light that enters the surrounding light receiving section 1is10B is weighted, and the area ratio of the spot photometry light receiving section to the average photometry light receiving section is larger than the area ratio of the spot photometry light receiving section to the entire shooting range. It is possible to reduce the ratio of

The photometric optical system shown in FIG. 8 is the same as the photometric optical system shown in FIG. 7, except that a diffuse reflection plate 32 is further provided on the outer periphery of the light receiving l5IOB. This allows V in the viewfinder field of view to
The reflector plate 3 reflects the light beam that deviates from the light receiving section 10B near the end and the H end.
2 and makes it incident on the light receiving section 10B.

〔Effect of the invention〕

As explained above, according to the photometry device according to the present invention, the ratio of the spot photometry range to the entire shooting range can be made smaller than the area ratio of the spot photometry photoreception area to the average photometry photoreception area of the photometry sensor. Spot photometry can be performed in a narrower range using the same photometry sensor than the spot photometry range of conventional photometry sensors.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an exploded perspective view of a finder unit in which a photometric device according to the present invention is installed, and FIG. 21! I is a side view of the main part of Fig. 1, No. 31! Figures 1 and 4 are diagrams used to explain the luminous flux that enters the photometric sensor via the lens shown in Figure 2, and Figures 5 and 6 respectively illustrate the distribution of light that enters the photometric sensor. The graphs shown in FIGS. 7 and 8 are views showing other embodiments of the present invention, and FIG. 9 is a plan view showing an example of the light receiving section of the photometric sensor. 10... Photometry sensor, IOA... Spot photometry light receiving section, OB... Light receiving section, 12. 14, 0... AE lens, 2A... Inner spherical surface, B... Outer spherical surface, 2... Diffuse reflection plate.

Claims (1)

[Scope of Claims] A two-divided photometric sensor having a spot photometric photoreceptor that performs spot photometry in the center of an average photometric photoreceptor that performs average photometry, the area of the spot photometric photoreceptor with respect to the average photometric photoreceptor. a photometric sensor whose ratio is larger than the ratio of a spot photometry range to the entire shooting range; A photometric device comprising: a photometric optical system that weights and guides a light receiving section;