JPH0141968B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in an automatic exposure device in an endoscopic camera that takes pictures of the inside of a human body.

Generally, when photographing the inside of a human body using an endoscope, there is a special situation in which the brightness of each part of the subject often differs greatly within the same photographic range. For example, when photographing the large intestine, the subject is in a concave state, so when lighting it,
The periphery is bright and the center is extremely dark. However, as a doctor, the entire subject within the photographic range is the subject of diagnosis, so in this case, it is desirable to use an average photometry method that controls the exposure amount based on average brightness, or a partial photometry method that is close to it. On the other hand, when photographing a protrusion such as a polyp formed in the stomach, the object has a convex shape, so when it is illuminated, the periphery becomes dark and the center becomes extremely bright.
In this case, since a high-intensity protrusion is particularly targeted for diagnosis, it is sufficient if this protrusion is properly exposed. Therefore, it is desirable to control the exposure amount by central photometry.

There is a strong desire for a photometry method that simultaneously satisfies each condition under these different circumstances. Conventionally, the known method is one in which the photometric area is mechanically varied arbitrarily (Japanese Patent Publication No. 1973-
(Japanese Patent Publication No. 26240, Japanese Patent Publication No. 47-49610), and one that electrically measures the brightness of each part of the subject and calculates the appropriate exposure amount electrically (Japanese Patent Publication No. 55-2857).
No. 2) is known. However, the former example requires a complicated mechanism for varying the size of the aperture provided in front of the photometric element and for moving the lens. Furthermore, the latter example requires a large number of photometric elements, and also requires a complicated electronic circuit to measure the output of each of them, determine the magnitude relationship between them, and control exposure.

In other words, these conventional photometers have very complicated mechanical or electrical configurations, have a large number of parts, and are expensive photometers.
Furthermore, the reliability of the photometry function is relatively low because the optical system requires a movable part, an exposure correction function based on the photometry area, and a complicated arithmetic circuit.

The present invention has been made focusing on the above circumstances,
The purpose of this is to develop an endoscopic camera that can perform appropriate exposure control with an extremely simple configuration even if the brightness distribution varies significantly within the same shooting range, and that can improve the reliability of exposure control. The purpose of the present invention is to provide a photometric device.

Embodiments of the present invention will be described below based on the drawings.

In FIG. 1, reference numeral 1 denotes a photographing lens of an endoscope camera, and this photographing lens 1 constitutes a photographing optical system 4 which forms an image of a subject onto a film 3 of a film cassette 2. A half prism 5 is installed on the optical axis of the photographing optical system 4 to split a part of the light and guide it in a direction perpendicular to the optical axis. The light split by the half prism 5 is made to enter a photometric element 7, which will be described later, through a condenser lens 6. That is, the half prism 5 and the condensing lens 6 constitute a photometric optical system 8 that makes a light image corresponding to the screen to be photographed enter the front side of the photometric element 7.

A disc-shaped aperture body 9 is installed immediately in front of the photometric element 7, and the condenser lens 6 forms an image of the light of the object on the front surface of the aperture body 9. Furthermore, as shown in FIG.
A through-hole 10 is provided at the center of the image forming apparatus, through which the imaging light from the central part of the subject passes through to the photometric element 7 side.
Small through holes 11... are provided. Therefore, only the light transmitted through the through holes 10 and 11 of the aperture body 9 enters the photometric element 7. The photometric element 7 then converts the current into a current according to the amount of incident light.

Further, this photometric element 7 is connected to an integrator 14 consisting of an operational amplifier 12 and an integrating capacitor 13. A normally closed switch 15 is connected in parallel to both ends of the integrating capacitor 13. This switch 15 is controlled by a release control circuit 16, and is normally in a closed state, but is in an open state when photographing. The output terminal of the integrator 14 is connected to one input terminal of a comparator 17, and the other input terminal of the comparator 17 outputs a voltage determined by the ASA information or exposure compensation information of the film 3. An exposure constant setting circuit 18 is connected. Comparator 1
The output terminals of 7 are connected to a shutter control circuit or a light emission control circuit (not shown).

Next, the operation of the embodiment having the above configuration will be explained.

First, the insertion section of the endoscope is introduced into the human body, and the inside of the body cavity is observed. Therefore, when taking a photograph, the endoscope camera is attached to the eyepiece of the endoscope, and the release operation of the endoscope camera is performed. As a result, the release control circuit 16 opens the switch 15 to enable the integrator 14 to perform an integrating operation. On the other hand, since the light emitted from the light source device for an endoscope illuminates the subject through the light guide of the endoscope, the reflected light passes through the image guide of the endoscope to the imaging optical system of the endoscope camera. incident on . Most of this incident light passes through the half prism 5 and forms an image on the film 3. On the other hand, the light split by the half prism 5 is focused on the front surface of the aperture body 9 by the condenser lens 6. Of this imaged light, the light that is imaged on the through holes 10, 11, . . . passes through as it is and enters the photometric element 7. Then, the photometric element 7 converts the current into a current whose magnitude corresponds to the amount of incident light. As described above, this current is integrated by the integrator 14, which is in a state where it can be integrated, and converted into a voltage value. This integrated voltage gradually increases, and when it reaches the output voltage of the exposure constant setting circuit 18, the comparator 17
detects this and outputs an exposure completion signal. This exposure completion signal is input to the shutter control circuit of the endoscopic camera or the light emission control circuit of the endoscope light source device, and in the case of the shutter control circuit, the shutter is closed, and in the case of the light emission control circuit, the light source is closed. Stop or block light emission. Therefore, the photographic optical system 8
The light incident on the is blocked. As a result, exposure for one frame of the film 3 is completed, and then a film winding device (not shown) is automatically operated to wind the film 3. This puts the camera in a standby state in which the next photograph can be taken. Further, the switch 15 is closed.

Incidentally, whether or not the exposure of the film 3 is appropriate is determined depending on whether the amount of light incident on the film 3 per unit area is appropriate. In this embodiment, the capacitance of the integrating capacitor 13 of the integrator 14 and the output value of the exposure constant setting circuit 18 are set such that only the exposed portion of the film 3 corresponding to the through hole 10 located at the center of the aperture body 9 is properly exposed. Set in advance. In other words, if only the central through-hole 10 of the aperture body 9 allows light to pass through, and the other surrounding through-holes 11 do not allow light to pass through, then the exposed area on the film 3 will not be properly exposed. Set each condition so that However, during actual shooting, other transparent holes 1 in the vicinity
1 also allows light to pass through.

Therefore, the actual photometry operation is performed as follows. First, if the subject has a concave shape as shown in FIG. 3, the image formed on the film 3 will be bright only at the periphery and dark at the center. Therefore, the dark bottom part A is photometered by the light transmitted through the central through-hole 10, and at the same time the other surrounding through-holes 11 are measured.
The bright flat area B is photometered by the light transmitted through... In other words, since the method is close to the so-called average metering method, it is possible to prevent a part of the subject from being extremely overexposed or underexposed. If photometry were performed using only the light transmitted through the central through-hole 10, the bottom portion A would be properly exposed, but the flat portion B would be extremely overexposed. According to this embodiment, this can be prevented. This is particularly effective when photographing an object shaped like a clay pipe, such as a large intestine.

On the other hand, when photographing a subject with a protrusion C as shown in FIG. 4, the protrusion C in the center is bright, but the flat area D around it is dark. Therefore, in the case of , the protrusion C is photometered by the light passing through the central through hole 10,
The surrounding flat portion D is photometered using light passing through the surrounding through holes 11. However, since the amount of light passing through the central through-hole 10 is large, this causes the photometric element 7 to output a large output current, but since the amount of light passing through the surrounding through-holes 11 is small, a small output current is generated. Only. In other words, the surrounding through-holes 11 do not significantly contribute to the photometry, and an exposure amount close to that of the central photometry method is determined. Therefore, the protrusion C can be photographed with proper exposure. If the exposure amount of the protrusion C is determined by the average photometry method, even if the screen as a whole is appropriate, the higher the protrusion C is, the more the exposure becomes overexposed, making it unsuitable for diagnosis. However, in this embodiment, the protrusion C is photographed with proper exposure, so there is no such inconvenience, and this is particularly effective when photographing polyps, stomach ulcers, etc.

The results of a photographic test using this method show that the ratio of the area of the central through-hole 10 of the aperture body 9 to the sum of the areas of the through-holes 11 around it is 1:0.2.
It was confirmed that when the exposure value is around 1.5, it is possible to obtain photographs with appropriate exposure for objects with convex or concave shapes inside the human body.

Peripheral through holes 11 in the aperture body 9 of the above embodiment
Although the shape of ... is a perfect circle, the present invention is not limited to this, but may be shaped like a raindrop as shown in FIG. 5, or triangular as shown in FIG. 6. Moreover, they may be arranged randomly instead of being arranged concentrically at equal intervals.

As explained above, the present invention is an automatic exposure device for an endoscopic camera that employs a central metering method, in which an aperture body is provided in front of a photometric element that measures the amount of light incident on the film, and this aperture body is provided only at the center. Because there were multiple holes around it,
Appropriate photography is always possible even when the brightness distribution of objects differs greatly, such as when photographing objects inside the human body. According to the present invention, there is no need for a movable part of the optical system, and there is no need for an exposure correction function based on a photometric area or a complicated arithmetic circuit. Therefore,
A significant simplification of the photometry mechanism can be achieved. Moreover,
The photometry function becomes stable and its reliability can be improved.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of a photometric device showing an embodiment of the present invention, FIG. 2 is a front view of a diaphragm body in the same embodiment, and FIGS. 3 and 4 are exposure states in the embodiment. , FIG. 5, and FIG. 6 are front views of different aperture bodies, respectively. 1... Shooting lens, 3... Film, 4... Shooting optical system, 7... Photometric element, 8... Photometric optical system,
9...Aperture body, 10...Through hole, 11...Through hole, 1
4... Integrator, 17... Comparator, 18... Exposure constant setting circuit.

Claims (1)

[Scope of Claims] 1. A photometric optical system that makes a light image corresponding to the screen to be photographed enter the front side of a photometric element having a single light-receiving surface is provided, and a photometric optical system is provided in front of the photometric element near the focal point of the photometric optical system. is an automatic exposure device for an endoscopic camera using a central metering method, which is equipped with an aperture body that has a through hole that transmits imaging light from the center of the subject, and the aperture body has a plurality of through holes around it. An automatic exposure device for an endoscope camera, characterized in that the output of the photometric element is input to an exposure constant setting circuit. 2. The automatic exposure device for an endoscopic camera according to claim 1, wherein the plurality of peripheral through-holes in the aperture body are provided concentrically with respect to the central through-hole. 3. The automatic exposure device for an endoscopic camera according to claim 1, wherein the plurality of peripheral through-holes in the aperture body are randomly provided.