JPH0516011B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic exposure control device, and particularly to an automatic exposure control device for an endoscope used in transendoscopic photography.

In strobe photography using automatic exposure control, overexposure occurs when shooting at close range. This is because when shooting at close range, the strobe light emission is stopped near the high light output area of the strobe light emission distribution, and the time at which the light emission stops is delayed from the proper flash stop time due to a delay in the flash stop signal, etc., and the flash output is high by this delay. This occurs because the area is exposed to light. In particular, in transendoscopic strobe photography, the influence of overexposure in short-distance strobe photography is large due to the use of long transmission paths.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an automatic exposure control device for an endoscope that can prevent overexposure during close-range strobe photography.

An embodiment of the present invention will be described below with reference to the drawings.

According to FIG. 1, an endoscope camera 2 is attached to an eyepiece of an endoscope 1, and a connector 4 at the tip of a universal cord 3 of the endoscope 1 is connected to a light source unit 5.

The endoscope 1 is provided with a light guide 6 extending from the end of the endoscope to the inside of the light source unit 5, and an image guide 7 extending from the end of the endoscope to the eyepiece of the endoscope. . The endoscope camera 2 is provided with a beam splitter 8 on an extension of the optical axis of the image guide 7. A light receiving element (for example, a photodiode) 9 is mounted on the side of the beam splitter 8.
is provided. The light receiving element 9 is connected to an integrator 11 via an amplifier 10. A switch 12 is connected in parallel to an integrating capacitor 11a of this integrator 11. The release switch 13 is connected to a signal line 14 of the endoscope 1. Similarly, the outputs of amplifier 10 and integrator 11 are connected to signal lines 15 and 16.
are connected to each.

The output end of the amplifier 10 is connected to the input end of the A/D converter 17 of the light source unit 5 via a signal line 15. The output end of A/D converter 17 is connected to port 18 . A CPU 19 is connected to this port 18 . CPU 19 is memory 2
Connected to 0. A set switch 21 is connected to the port 18, as well as a D/A converter 22 and an A/D converter 23. The output terminal of the D/A converter 22 is connected to the input terminal of the comparator 24 together with the output terminal of the integrator 11 of the camera 2. The output terminal of the comparator 24 is connected to the input terminal of the lighting control circuit 25. This lighting control circuit 2
5 is configured to control the power applied to the strobe tube 26 and the lamp 27 to control the emission of the photographing light and the collation light, and to transmit an electric signal corresponding to the power to the A/D converter 23. There is. The mirror 28 serves as the optical path of the strobe tube 26 and the lamp 27.
Provided to switch the optical path of the light.

The operation of the automatic exposure control device of the endoscope system will be explained with reference to the flowchart of FIG.

First, setting data is input via the set switch 21. This setting data includes the exposure level B, information α corresponding to the distance required for correction, and correction ratio β. These data are obtained by taking into consideration film sensitivity, endoscope type, light source unit type, imaged area, etc. Exposure level B is the set value
When set as BO, there is a range of allowable error Δβ for this set value BO as shown in FIG.
α is a function of the distance value D that requires correction even if this allowable error Δβ is taken into account. The correction ratio β is appropriately set according to the photographing conditions of close-range photography, which may result in overexposure. When these set values BO, α, and β are input to port 18 by set switch 21,
The CPU 19 processes the setting data BO, α, and β, respectively, and stores them in the memory 20. Once the initial values have been set in this way, the system operates according to the flowchart shown in FIG. That is, first, it is determined whether the exposure level B has been changed from the initial value. For example, if the exposure level B has been changed depending on the brightness of the desired photograph, the exposure level B is reset, and if not, it is determined whether or not the distance determination value α has changed. When there is a change in α, α is reset. If there is no change, it is determined whether there is a change in the correction ratio β. If there is a change in β, β is reset, and if there is no change, the power applied to the light source is measured. In this case, lamp 27
An electric signal corresponding to the light incident on the light guide 6 by the mirror 28, that is, a voltage signal corresponding to the power applied to the light source is output from the lighting control circuit 25, and this voltage signal is sent to the A/D converter. 2
3 is input. This voltage signal is converted into a digital signal by the A/D converter 23, and is sent to port 1.
8 and is input to the CPU 19 for arithmetic processing.
The CPU 19 stores the light source power data in the memory 20. On the other hand, the lamp 2 via the light guide 6
The light 7 illuminates the object 29. The reflected light from the object 29 enters the beam splitter 8 via the image guide 7. A portion of the reflected light incident on the beam splitter 8 is incident on the light receiving element 9. The light receiving element 9 outputs a photocurrent corresponding to the incident light. The photocurrent is voltage amplified by an amplifier 10 and sent to a signal line 15.
A/D converter 17 of light source unit 5 via
supplied to The output of the amplifier 10 is also supplied to the integrator 11, and at this time, the switch 1 of the integrator 11
2 is closed, the integrator 11 does not perform an integrating operation.

The reflected light voltage signal input to the A/D converter 17 is digitally converted and sent through the port 18.
It is input to the CPU 19. The CPU 19 processes the reflected light voltage signal and stores the reflected light data in the memory 20. Thereafter, the CPU 19 calculates the ratio A between the voltage signal corresponding to the light source power and the voltage signal corresponding to the reflected light using the following equation.

A=(voltage signal corresponding to reflected light)/(voltage signal corresponding to light source power) This ratio A is compared with the distance judgment value α, and A≦α
In this case, the CPU 19 determines that the distance is not close and outputs exposure level B. When A>α, the CPU 19 determines that the distance is short and outputs data of exposure level B×correction ratio β. Data B or B×β is port 1
8 to the D/A converter 22, and then to the comparator 24 as reference data.

When the release switch 13 is closed to take a photograph in the above state, a release signal is input to the illumination control circuit 25. The illumination control circuit 25 raises the mirror 28 in response to the release signal to form an optical path for the strobe tube 26 and causes the strobe tube 26 to emit light. The strobe light illuminates the object 29 through the light guide 6, and the reflected light from the object 29 enters the beam splitter 8 through the image guide 7. The light receiving element 9 outputs a photocurrent corresponding to the strobe reflected light. At this time, since the switch 12 of the integrator 11 is open, the light reception signal amplified by the amplifier 10 is integrated by the integrator 11. Integrator 11 outputs an integral signal as shown in FIG. 4a, and this integral signal is input to comparator 24 via signal line 16.
During non-close shooting, the reference data of exposure level B is input to the comparator 24 via the D/A converter 22, so when the integral signal reaches the reference value B, the output of the comparator 24 is as shown in FIG. 4b. to be reversed. When the output signal of the comparator 24 is input to the illumination control circuit 25, the strobe tube 26 stops emitting light. At this time, the light emission time of the strobe tube 26 should be T0-T1 time, but due to transmission delay of the integral signal, etc., from the time the integral value reaches the reference value until the strobe tube 26 stops emitting light, T1-
There is a delay of T2 time, so the actual light emission time of the strobe tube 26 is T0 - T2. In other words, the delay
Overexposure occurs for T1-T2 time. However, in non-close-distance photography, the exposure amount for the T1-T2 time falls within the allowable error range, so it has almost no effect on the photograph.

When performing close-range photography, the integrator 11
An integral signal as shown in FIG. At this time, the CPU 19 selects short distance mode.
In other words, since it is determined that A>α, comparator 2
4, reference value data of B×β is input. Therefore, the light emission of the strobe tube 26 is stopped at time T3 when the integral signal reaches the reference value B×β. At this time, the light emission time T0−T3 will result in underexposure, but since there is a delay time T3−T4, the actual light emission time is T0−
The exposure becomes T4, and the appropriate exposure amount corresponding to the set value B is obtained.

Further, in the above embodiment, correction is performed in close-range photography, but the following may be used.
In other words, in anticipation of overexposure due to transmission delays, etc. during close-range photography, the exposure level B is set low to ensure proper exposure during close-range photography, and conversely, correction is made during non-close-range photography, that is, when underexposure occurs. You can do it like this. That is, in the above embodiment, the values of exposure level B, distance judgment value α, and correction rate β are changed as appropriate, and when it is determined that the short distance mode, that is, A>α, the comparator 24 is set to the reference value B (exposure due to transmission delay, etc.). A reference value of B×β (β≧1) may be input to the comparator 24 when it is determined that the non-short range mode, that is, A≦α, is input. .

As explained above, according to the present invention, there is provided a means for automatically correcting the exposure reference value during close-range photography, where the influence of overexposure due to signal delay, etc. becomes large, so overexposure may occur during close-range photography. This can be prevented.

It should be noted that the present invention is not limited to the above-described embodiments; for example, the light receiving element may be provided in the endoscope, the amplifier and integrator may be provided in the light source unit or the endoscope, and the comparator may be provided in the camera or the endoscope. Also, although only one ratio A is set between the voltage signal corresponding to the light source power and the voltage signal corresponding to the reflected light, it is also possible to set multiple values and calculate β for each case to change the degree of correction. good. Further, in this embodiment, A is determined as a ratio of voltage signals, but it may be determined as a ratio of other electrical signals as appropriate.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an endoscope system having an automatic exposure control device according to an embodiment of the present invention, and FIG.
The figure is a flow chart to explain the operation of the circuit in Figure 1, Figure 3 is a graph diagram showing the relationship between shooting distance and exposure amount, and Figure 4 is a time chart to explain automatic exposure control. It is a diagram. 1... Endoscope, 2... Endoscope camera, 5... Light source unit, 9... Light receiving element, 10... Amplifier,
11... Integrator, 14, 15, 16... Signal line, 17... A/D converter, 18... Port, 19... CPU, 20... Memory, 21...
Set switch, 22...D/A converter, 2
3...A/D converter, 24...Comparator, 25...Lighting control circuit, 26...Strobe tube, 27...Lamp, 28...Mirror.

Claims (1)

[Scope of Claims] 1. An illumination light source for illuminating a subject; a power measuring means for measuring the light source power of the illumination light source during examination; and an electrical signal corresponding to the light source power measured by the power measuring means. reflected light measuring means for measuring the reflected light from the subject; means for outputting an electrical signal corresponding to the measured value of the reflected light measuring means; and an electrical signal corresponding to the collimation light power. and an electric signal corresponding to the reflected light; a means for generating correction judgment value data for a reflected light level according to a distance that requires exposure correction during photographing; a reference value output means that compares the output value of the means with the correction judgment value and outputs a corrected reference value or a non-corrected reference value according to the comparison result; a photographing light source that irradiates photographing light during photographing; and the photographing light. and means for outputting an exposure stop signal when the exposure value exceeds a reference value output from the reference value output means. An automatic exposure control device for an endoscope, characterized in that: