JPH03121410A - Photographic light quantity controller for endoscope - Google Patents

Abstract

PURPOSE:To prevent over-exposure even in a range of an about middle distance and to obtain a sharp photograph which is free from a blur by providing a photodetector, a photometric circuit, a shutter control means, and an illuminating light quantity control means. CONSTITUTION:The photometric circuit 33 which integrates the output from the photodetector 15 and outputs the integrated state value thereof and the shutter control means 34 which closes a shutter 32 provided in an illuminating optical path when the output increases and attains a preset value are provided. The control means differentiates and detects the rise of the integrated value and controls the brightness of a light source 30 to the min. brightness for photographing when the differentiated output thereof is above a 1st reference value. The means maximizes the brightness of the light source 30 when the output is below the 2nd reference value smaller than the 1st reference value. The means controls the brightness of the light source 30 to the prescribed brightness between the min. and max. when the output is between the 1st and 2nd reference values. The generation of the problem of the photographic blur is obviated in this way and the range where the photographing can be made with the ideal exposure time is widened. The sharp photograph is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an endoscope photographing light amount control device for controlling the amount of illumination light when taking photographs through an endoscope.

[Conventional technology]

Endoscopes are generally capable of not only observing the inside of a body cavity but also taking photographs. The exposure time during photographing is determined by integrating the output of the light receiving element that receives the reflected light from the subject illuminated by the light source, and when the integrated voltage reaches the set voltage, controlled by closing a mechanical shutter.

However, mechanical shutters require time from when they receive the closing signal until they actually close (usually 0.
．． 05 seconds). Therefore, the exposure becomes overexposed. The exposure time ΔT for the amount of overexposure is constant regardless of the length of the total exposure time T at that time. Therefore, when the total exposure time T is short, that is, when the subject is bright, such as during close-up photography, the influence of ΔT increases, resulting in significant overexposure.

Conventionally, therefore, the rise of the output of an integral state value obtained by integrating the output of the light receiving element is differentially detected, and when this differential output value is equal to or greater than a reference value, the amount of light emitted by the light source is reduced to the observation state level, and the total exposure time T was made longer to reduce the influence of ΔT (Japanese Patent Publication No. 61-36928).

[Problem to be solved by the invention]

In the endoscope photographing light amount control device as described above, the lower the reference value, the wider the range in which overexposure can be reduced. However, if the reference value is lowered, the exposure time becomes longer and blurring occurs, so the reference value has to be set to a considerably higher value.

As a result, considerable overexposure still occurred in the middle distance range where the above-mentioned differential output was lower than the reference value.

This invention eliminates such conventional drawbacks, prevents overexposure during photography even at medium distances, and provides a photographic light amount for endoscopes that can obtain clear photographs without blur as a whole. The purpose is to provide a control device.

[Means to solve the problem]

In order to achieve the above object, the endoscope photography light amount control device of the present invention includes a light receiving element that receives reflected light from a subject illuminated by a light source and converts the brightness into an electrical signal, and A photometric circuit that integrates the output from the element and outputs the integrated state value, and a shutter provided in the illumination optical path that closes when the output from the photometric circuit increases and reaches a preset value. shutter control means; differentially detecting the rising edge of the integral state value; when the differential output is equal to or higher than a first reference value, the brightness of the light source is minimized within a variable range of brightness for photographing; and the differential output is is less than a second reference value that is smaller than the first reference value, the brightness of the light source is maximized, and when the differential output is between the first and second reference values, the brightness of the light source is reduced. The present invention is characterized in that an illumination light amount control means is provided for controlling the brightness to a predetermined brightness between the maximum and minimum values.

[Effect]

During close-range photography, the differential output is equal to or greater than the first reference value, and the brightness of the light source is minimized within the variable range of brightness for photography. Therefore, the exposure time is extended, the ratio of the time required for the shutter to close to the exposure time is reduced, and overexposure during photographing is alleviated.

During long-distance shooting, the differential output becomes less than the second reference value, and the brightness of the light source becomes maximum. Therefore, the exposure time is not extended, and photographic blur does not occur.

In this case, since the exposure time is originally long, the problem of overexposure does not occur.

During medium-distance shooting, the differential output is between the first and second reference values, and the brightness of the light source is a predetermined brightness between the maximum and minimum. Therefore, the exposure time is extended to some extent and overexposure is alleviated, but since the exposure time is not extended as much as when the brightness of the light source is minimized, the problem of photographic blur does not occur.

〔Example〕

Examples will be described with reference to the drawings.

In FIG. 1a, l is an endoscope. 2 is an imaging device that is detachably attached to the endoscope l. 3 is a photographing light amount control device for an endoscope. In this system, the light source device 3
The light from the light source 30 provided inside the endoscope l
1 to the insertion section distal end 12 through the light guide fiber 13, and illuminates the subject 100 inside the body cavity. The reflected light is then transmitted from the insertion section distal end 12 to the eyepiece section 14 through an image guide fiber (not shown). The light receiving element 1 provided in the eyepiece section 14
5, and the received light brightness is converted into an electrical signal.

The light source 30 provided in the light source device 3 is, for example, a xenon lamp, and its emitted light passes through a condenser lens 31 and is condensed onto the input end face of the light guide fiber 13. A mechanical shutter 3 that can be opened and closed is installed in the illumination optical path between them.
2 is provided.

33 is a photometric circuit connected to the output end of the light receiving element 15, which integrates the output from the light receiving element 15 and outputs the integrated state value. 34 is a shutter control circuit that controls the opening/closing operation of the shutter 32;

35 is a light source 30 for controlling the amount of light emitted from the light source 30;
This is a light source current control circuit that controls the current supplied to the light source.

21 is a synchro switch provided in the photographing device 2, and is connected to a sequence circuit 36 provided in the light source device 3. When the synchro switch 21 is turned on and off, the sequence circuit 36 controls the photometry circuit 3.
3. The operations of the shutter control circuit 34 and the light source current control circuit 35 are sequentially started or ended.

37 is an exposure index setting switch for setting an exposure index according to the sensitivity of the film 25 used in the photographing device 2, and the appropriate exposure setting circuit 38 is activated by the input thereof.
settings are made.

The output value from the photometry circuit 33 and the output value from the appropriate exposure setting circuit 38 are compared by a first comparator 40, and the shutter closing operation of the shutter control circuit 34 is controlled. That is,
When the output from the photometry circuit 33 reaches the set value of the appropriate exposure setting circuit 38, the shutter 32 is closed.

4I is a reference voltage setting circuit that automatically sets reference voltages dl, dt (dl > cL >) according to the output voltage vR from the appropriate exposure setting circuit 38. The reference voltages d+, dt set here are Used as a reference value to control the magnitude of current.

FIG. 1b shows an example of the reference voltage setting circuit 41. As shown in FIG. In this circuit, the first and second amplifiers 411
．． The output voltage (3) from the appropriate exposure setting circuit 38 is divided and inputted to the positive-pole side input terminal of each of the input terminals 412.

From the power supply voltage V of the device, the first voltage dividing resistor 413.4
14 and second voltage dividing resistors 413 and 415, reference voltages v1 and v2 are obtained.

Then, the reference potential point and the first and second operational amplifiers 4
The input terminal on the negative side of 11,412 is connected to the resistor 4.
18.418. Additionally, feedback resistors 416, 417 are connected between the output terminal of each operational amplifier 411, 412 and the negative input terminal.
is connected.

Therefore, as shown in FIG. 1b, resistor 413
, 414, 415. 416, 417, 418 are Rs, R4, Rs, Rt, R1.

If R1, the first and second operational amplifiers are 411°41
The output voltage (reference voltage) dl, dt from 2 is cL
= (VR-Vr) ・Rt/Rsdt” (V
-Vz) ” Rt /R1.

Therefore, if Rt>Rz and for ease of calculation R4=Rs (ie, V l = V 2 ), then dl>dt.

Also, Ro << R! Then, Vr = V-Re / , (Ra + R4)■! ±
VRs/(Ra+R6). However, v
R such that both l and V are smaller than the minimum value of vR.
Set s and Rs.

Also, for example, Rt-RJ R2 electric R3/2 By keeping it as d, 62d.

This is a convenient ratio for controlling the present embodiment. Note that the specific magnitudes of dl and dt depend on the magnitude of the output voltage v3 of the appropriate exposure setting circuit 38 and the differentiation circuit 42.
It is determined by considering the magnitude of the output voltage.

The first and second reference voltages d+ and cL are the output of a differentiation circuit 42 that differentially detects the rising edge of the integral state value output from the photometry circuit 33, and the second and third comparators 43.4.
4, and the comparison result is sent to the light source current control circuit 35.
sent to.

When the output of the differentiating circuit 42 is equal to or higher than the first reference voltage 61, the light source current is controlled to the minimum, and the amount of light emitted from the light source 30 is minimized.

When the output of the differentiating circuit 42 is equal to or lower than the second reference voltage d2, the light source current is controlled to the maximum, and the amount of light emitted from the light source 30 becomes maximum.

The output of the differentiating circuit 42 is the first and second reference voltages d+, dz
When the light source current is between the maximum and minimum values, the light source current is controlled to a predetermined current value between the maximum and minimum values, and the amount of light emitted from the light source 30 has an intermediate brightness.

FIGS. 2a to 2c are time charts showing the operation of the above embodiment.

When the synchronization switch 21 of the photographing device 2 is turned on, the shutter (camera shutter) 22 of the photographing device 2 opens with a slight delay and closes after a certain period of time (for example, 0.25 seconds) has elapsed. Further, at the same time as the synchro switch 21 is turned on, the shutter 32 in the light source device 3 is temporarily closed by a signal from the sequence circuit 36, and the entire operation period signal is turned on. Then, after a short predetermined time t, the shutter 32 of the light source device 3 is opened, and after the camera shutter 22 is closed, the entire operation period signal is turned off after t2 has elapsed from the beginning (all operations are completed).

When the initial shutter close signal falls, at the same time, the shutter 32 of the light source begins to open, and at the same time, the amount of light emitted from the light source 30 is temporarily maximized.

However, when the distance to the subject 100 is short, the differential output is detected to be higher than the first reference voltage 61. At this time, as shown in FIG. 2a, the amount of light emitted by the light source 30 decreases to the minimum within the variable range of brightness for photographing, the increase in the integral value becomes gradual, and the integral output voltage reaches the set voltage. The time will be extended. Then, when the integrated output voltage reaches the set voltage, the shutter 32 of the light source closes and the exposure ends. Therefore, compared to the case where the amount of light emitted by the light source 30 remains at the maximum, the exposure time is extended, the ratio of the time ΔT required for the shutter 32 to close to the exposure time is small, and the amount of light between 61 and 61 is minimized. Therefore, overexposure of the film surface 25 is alleviated.

Conversely, when the distance to the subject 100 is long, the differential output is detected to be less than or equal to the second reference voltage d2. At that time, as shown in FIG. 2b, the amount of light emitted by the light source 30 remains at the maximum, and when the integrated output voltage reaches the set voltage, the shutter 32 of the light source closes and the exposure ends.

Therefore, the exposure time is not extended and the problem of photographic blur does not occur.

When the distance to the subject 100 is intermediate, the differential output is detected between the first and second reference voltages d+ and dz.

At that time, as shown in FIG. 2c, the amount of light emitted by the light source 30 is controlled to a predetermined brightness between the maximum and the small R, and the integral value rises moderately and gradually, and the integral output voltage The time it takes for the voltage to reach the set voltage is extended to some extent.

Then, when the integrated output voltage reaches the set voltage, the shutter 32 of the light source closes and the exposure ends. Therefore, although the exposure time is extended to some extent and overexposure of the film surface 25 is alleviated, the exposure time is not extended to the extent that the amount of light emitted by the light source 30 is lowered to the minimum, and the problem of blur does not occur.

Note that the differential output is the first and second reference voltages d+.

When it is in the middle of d2, the amount of light emitted by the light source 30 may be controlled in multiple stages depending on the magnitude of the differential output. Further, three or more reference voltages may be provided to perform more detailed control.

〔Effect of the invention〕

According to the imaging light amount control device for an endoscope of the present invention, when the distance to the subject is medium, that is, when the differential output is below the reference value, and even when overexposure occurs conventionally, the exposure time This extends the exposure time to a certain extent, which prevents overexposure.Moreover, the exposure time does not extend as much as when the brightness of the light source is minimized within the variable range of shooting brightness, so the problem of blurring does not occur, making it ideal. This has the excellent effect of widening the range that can be photographed with a short exposure time and producing clear photographs.

[Brief explanation of drawings]

FIGS. 1a and 1b are circuit diagrams showing the configuration of an embodiment of the present invention, and FIGS. 2a to 2c are time charts showing the operation of the embodiment. 15... Light receiving element, 30... Light source, 32... Shutter, 33... Photometry circuit, 34... Shutter control circuit, 35... Light source current control circuit, 42... Differential circuit.

Claims (1)

[Scope of Claims] A light-receiving element that receives reflected light from an object illuminated by a light source and converts its brightness into an electrical signal; and a light-receiving element that integrates the output from the light-receiving element and outputs its integral state value. a photometric circuit; a shutter control means for closing a shutter provided in the illumination optical path when the output from the photometric circuit increases and reaches a preset value; and differential detection of the rising edge of the integral state value. When the differential output is greater than or equal to the first reference value, the brightness of the light source is minimized within the variable range of photographic brightness, and the differential output is equal to or less than a second reference value, which is smaller than the first reference value. When , the brightness of the light source is maximized, and when the differential output is between the first and second reference values, the brightness of the light source is controlled to a predetermined brightness between the maximum and minimum values. A photographing light amount control device for an endoscope, characterized in that an illumination light amount control means is provided.