JPS6245686Y2 - - Google Patents

Description

[Detailed description of the invention] This invention is a device that can be applied to a photographic device that illuminates the surface to be examined in a slit shape, observes it with a lamp, and takes a picture with a strobe, especially a photo slit lamp used in ophthalmology. This invention relates to a device capable of automatic exposure control.

Generally, when there is a significant difference in brightness between parts of a subject, for example when the subject is illuminated in a slit shape, partial light metering is required to photograph that particular part with the appropriate exposure.

Conventionally, for this purpose, center-weighted photometry, that is, photometry was performed by providing a photometry aperture near the conjugate surface of the film to cover the vicinity of the center of the screen.

If you want to photometer a specific point on the screen, you can make this aperture smaller by moving it closer to the conjugate plane. However, if the object to be photometered is small, it becomes difficult to align the photometering aperture and the object within the viewfinder.

Therefore, as shown in FIG. 1, a photometric aperture 11 having a certain size is provided, and the photometric aperture 11
The amount of light passing through the sensor was measured using a single photodetector.

However, as shown in FIG. 1a, the subject image 5a is narrower than the width of the photometric aperture 11, and
As shown in FIG. 1B, the subject image 5a', which is wider than the width of the photometric aperture 11, is assumed to have uniform and the same illuminance, that is, in FIG. 1st
In Figure b, the background is assumed to be the same bright area as the slit irradiation area. When comparing the two, the amount of light measured in Figure 1B is larger than that in Figure 1A, and even though the illuminance is the same, the photometry is An inconvenient situation arises in which the results are different.

An object of the present invention is to provide a photographic device that solves the above-mentioned drawbacks.

Examples of the present invention will be described below. The embodiment shown in FIG. 2 is an apparatus in which a subject, for example, an eye to be examined, is irradiated in a slit shape, observed with a lamp 1, and photographed with a strobe tube 3. In FIG. 2, light emitted from a lamp 1 is focused on the strobe tube by a condenser lens 2, and illuminates a subject 5 by an illumination lens 4. The light reflected and scattered from the subject 5 is sent to the photographic lens 6.
The light is then separated into a film 9 and a light-receiving element array 8 by a splitting member 7. The function of the light-receiving element array 8 will be explained later with reference to FIG. 3, and as the light-receiving element array 8, a photodiode array, CCD, etc. are used.

Here, the film 9 and the light receiving element array 8 are arranged in an optically conjugate relationship.

Note that the light splitting member 7 may be a known quick return mirror.

In FIG. 2, a light receiving element 10 monitors the light amount of the lamp 1, compares it with a standard light amount, and corrects the exposure conditions of the strobe tube 3. In other words, the lamp 1 has significance as a simulated light source for photography, and the appropriate exposure amount of the strobe tube is detected from the output of the light receiving element array 8 corresponding to the standard light amount of the lamp 1. The deviation is detected by the light receiving element 10, and the appropriate exposure amount of the strobe tube 3 is corrected.

Although it is assumed that the light receiving element 10 monitors the amount of light as the lamp output, it may also monitor the electrical input that is the lamp input.

Now, Figure 3 shows the photodetector array 8 in this invention.
This shows the relationship between the image and the subject image. Here, since the width of each light receiving element of the light receiving element array 8 is smaller than the slit illumination width as shown in FIG. 3a, the subject image 5a illuminated by a wide slit as shown in FIG. 3b ' and a subject image 5a illuminated with a narrow slit as shown in FIG. That is, when the slit illumination width is variable, stable photometry is possible using a light receiving element array consisting of light receiving elements having a width narrower than the minimum slit illumination width of the illuminated image of the subject.

Generally, the illuminance of the object image is non-uniform, but it is sufficient to set the maximum value of the output of each element of the light-receiving element array 8 as the exposure condition.

In this way, by using a light-receiving element array consisting of light-receiving elements having a width narrower than the slit irradiation width, appropriate exposure conditions can be determined regardless of the size of the subject. Furthermore, when the subject is small, even if the subject moves a little, the light will be applied to one of the light receiving elements and a proper exposure can be obtained.

Furthermore, as shown in FIG.
The above effect can be enhanced by making the arrangement direction of the slits orthogonal to the longitudinal direction of the slits in the slit irradiation area.

Furthermore, the following effects can also be obtained by using the above-described light receiving element array. In other words, when there is a small but very strong bright spot on the subject, in the conventional example shown in Figure 1, this bright spot is included in the photometry, resulting in underexposure. An upper threshold value is set for the element, and when the amount of light that exceeds that value enters, it is ignored and exposure is performed using the value of the other element, for example, the value of the element whose output is the maximum value lower than the threshold value. By determining this, appropriate exposure conditions can be obtained even for subjects with small bright spots. As described above, according to the present invention, it is possible to obtain appropriate exposure conditions with a simple configuration without being affected by the amount of background light, and furthermore, when there is a small bright spot overlapping the subject, the light of the bright spot can be Appropriate strobe exposure conditions can be obtained without being affected, and automatic exposure control becomes possible.

[Brief explanation of the drawing]

Figures 1a and b are explanatory diagrams of a conventional example, Figure 2 is a diagram of an embodiment of the present invention, and Figures 3a and b are diagrams showing the relationship between the light-receiving element array and a subject image according to the present invention. , 1 is a lamp, 2 is a condenser lens, 3
is a strobe tube, 4 is a lighting lens, 5 is a subject, 5
a, 5a' are subject images, 6 is a photographing lens, 7 is a light splitting member, 8 is a light receiving element array, 9 is a film, 1
0 is a light receiving element, and 11 is a photometric aperture.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) In a photographic device that illuminates a subject in a slit shape with a variable slit illumination width, observes it with a lamp, and photographs it with a strobe, the minimum slit illumination width of the illuminated image of the subject is A light-receiving element array consisting of light-receiving elements with a narrow width is provided on the image plane of the object so that the arrangement direction thereof is perpendicular to the longitudinal direction of the slit of the irradiated image of the object, and the exposure conditions of the strobe are determined from the output of the light-receiving element array. A photographic device characterized by: (2) Scope of Utility Model Registration Claim No. 1, which determines the exposure conditions of the strobe by detecting the maximum value of the output of each light-receiving element of the light-receiving element array by the lamp.
The photographic device described in (1). (3) A utility model in which the maximum output value is compared with a predetermined threshold value, and when the maximum output value exceeds the threshold value, the outputs of other light receiving elements in the light receiving element array are detected and the exposure conditions are determined. A photographic device according to registered claim 2. (4) The photographing device according to claim 1, which monitors the input or output of the lamp and determines the exposure conditions of the strobe based on the input or output of the lamp and the output of the light receiving element array.