JPH03143421A - Signal processing equipment for electronic endoscope - Google Patents

Abstract

PURPOSE:To reproduce brightness in the central part of picture, which is desired to be observed most precisely, with an optimum brightness for any picture angle of an object by extracting an output electric signal or image signal in a specified period almost at the middle of a vertical and/or horizontal scanning periods and by controlling a diaphragm, which regulates an illumination light, according to that extracted signal level. CONSTITUTION:A light source 39 is lighted by an electric power supplied from a light source operation circuit 39 and emits a parallel light. A diaphragm 36 is installed in front of the parallel light emitted from the light source 39 and controls the light quantity of the parallel light. A contraction ratio of the diaphragm 36 is controlled by a control circuit 40, to which an electric or image signal is put in from a signal processing circuit 29 as a basis of contraction control and a vertical and horizontal synchronizing signals are also put in from a synchronizing signal generation circuit 31. In front of the diaphragm 36, a collimation lens 35 is arranged to make the light emitted out of the diaphragm 36 parallel.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a signal processing device for an electronic endoscope, and particularly to a signal processing device for an electronic endoscope suitable for use with a wide variety of subjects.

[Conventional technology]

Electronic endoscopes usually insert a light guide inside a subject such as a human body, irradiate light from the light guide onto the subject, detect the reflected light from the subject with an image sensor, and convert it into an electrical signal. Then, this electrical signal is processed into a video signal suitable for display on a monitor such as a CRT, and the video signal is output to the monitor to obtain an image of the subject on the monitor.

Incidentally, in an electronic endoscope, the area (ie, angle of view) occupied by a reproduced image on the monitor differs depending on the type of subject. That is, as shown in FIG. 5(1), the electrical signal representing the subject image indicated by the solid line ■ exists only near the middle of the horizontal scanning period of the horizontal synchronization signal in FIG. 5(2); Some parts are O level. Furthermore, the electrical signal representing the subject image indicated by the broken line ■ exists for almost the entire horizontal scanning period of the horizontal synchronizing signal in FIG. will be played. This also applies to the vertical component.

On the other hand, in electronic endoscope devices, the amount of light that enters the light guide from the light source is usually controlled by an aperture in order to maintain the brightness of the reproduced image on the monitor at a certain constant level. The aperture is controlled by smoothing the level of the output electrical signal of the image sensor, and setting the median value of the aperture in accordance with the smoothed electrical signal level.

In such an aperture control mechanism, as shown in Fig. 5 (1), for a subject indicated by the solid line ■ where the image exists only near the middle of the monitor screen, the smoothed aperture control signal will be converted to the solid line ■'
In the case of the electric signal (2) from the subject whose reproduced image is displayed on substantially the entire surface of the monitor screen, the smoothed aperture control signal becomes as shown by the broken line (2). As is clear from Fig. 5 (1), in such a conventional aperture control method, the median value of the aperture changes depending on the imaging area of the subject, and on the other hand, the tracking speed of the aperture is extremely slow. The drawback was that whenever the subject changed, the screen as a whole would become too bright or too dark, or hunting would occur.

[Problem to be solved by the invention]

For this reason, in the past, an ID code was set for each subject, and each time the subject was changed, the ID code was set again to change the median aperture value. The median aperture value was manually set by the electronic endoscope scanner.

For this reason, when you want to observe objects with an angle of view of λ one after another, or when you want to quickly observe another object, it takes time and effort to set the median aperture value, making it impossible to observe quickly.

The present invention has been made in order to eliminate the above-mentioned drawbacks of the conventional signal processing device of an electronic endoscope.
It is an object of the present invention to provide a signal processing device for an electronic endoscope that can always obtain reproduced images with appropriate brightness without having to reset the median value of the aperture each time.

[Means to solve the problem]

The signal processing device for an electronic endoscope of the present invention includes a light source that emits light to be irradiated onto a subject, an aperture that controls the amount of light from the light source, an aperture control means that controls the operation of the aperture, and a light source that emits light to be irradiated onto a subject. An electronic endoscope comprising a signal processing means for processing an electric signal proportional to the amount of reflected light into a video signal, and a synchronization signal generation means for supplying a vertical synchronization signal and a horizontal synchronization signal of the video signal to the signal processing means etc. In the signal processing device, the aperture control means is an extraction means for extracting the electric signal or video signal only during a predetermined period approximately in the middle of a vertical scanning period of the vertical synchronization signal and/or a horizontal scanning period of the horizontal synchronization signal. , a smoothing means for smoothing the electric signal or the video signal extracted by the extraction means, a holding means for holding the voltage level of the electric signal or the video signal smoothed by the smoothing means for a predetermined period, and the holding means. The invention is characterized by comprising a drive means for controlling the operation of the aperture according to a voltage level held by the means.

[Effect]

In the signal processing device for an electronic endoscope according to the present invention, an electrical signal or a video signal from a subject is extracted only during a predetermined period approximately in the middle of a vertical scanning period and/or a horizontal scanning period, and the electrical signal extracted in this way is The signal or video signal is smoothed, this smoothed voltage level is held for a predetermined period of time, and the operation of the aperture is controlled according to this smoothed voltage level. Even when observing, the subject image can always be reproduced on the monitor screen with optimal brightness. This is because, in general, with electronic endoscopes, as shown in Figure 5 (1), the part of the subject image that has the highest brightness and is most desired to be observed is set near the center of the monitor's playback screen. Therefore, by controlling the aperture according to the voltage level of the image near the center of the monitor, you can always obtain a reproduced image with a brightness that corresponds to the illuminance of the part of the subject that you want to observe most. It is from.

〔Example〕

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

FIG. 2 is a block diagram showing a circuit configuration when a light guide 21 is connected to an embodiment 28 of the signal processing device for an electronic endoscope of the present invention and an image of a subject 22 is displayed on a monitor 41. Further, FIG. 1 is a circuit diagram showing an embodiment of the aperture control circuit 40 in the block diagram of FIG. 2. In FIG.

First, the block diagram shown in FIG. 2 will be explained. In Figure 2,
The light source 39 is lit by power supplied from the light source lighting circuit 38 and emits parallel light. A diaphragm 36 is installed in front of the parallel light emitted from the light source 39 to control the amount of the parallel light. The aperture amount of the aperture 36 is controlled by an aperture control circuit 401, and an electric signal or a video signal serving as a reference for the aperture control operation is inputted from the signal processing circuit 29 to the aperture control circuit 401. Further, a vertical synchronization signal and a horizontal synchronization signal are input from the synchronization signal generation circuit 31. A collimating lens 35 is installed in front of the aperture 36 to convert the light emitted from the aperture 36 into parallel light. Further, a rotating disk 33 driven by a motor 34 is installed in front of the collimating lens 35. The rotating disk 33 has red, green,
Three color filters of blue are installed, and the light emitted from the collimator lens 35 becomes sequential light of red, one fit, and blue. The emitted light that is sequentially converted into red, green, and blue light by the rotating disk 33 is condensed by a condensing lens 32 installed in front of the rotating disk 33, and enters the optical fiber 27 in the light guide 21. .

The illumination light emitted from the output end of the optical fiber 27 is irradiated onto the subject 22, and the reflected light from the subject 22 is condensed by the condensing lens 23 provided in front of the light guide 21. The light enters the CCD 24 provided on the back surface of the camera. A drive pulse signal is supplied to the CCD 24 from a synchronizing signal generation circuit 31 in a signal processing device 28 via a signal line 26. Further, the output electric signal of the CCD 24 is inputted to a signal processing circuit 29 provided in a signal processing device 28 via a signal line 25.

The signal processing circuit 29 has R and G signals suitable for displaying the output electric signal of the CCD 24 on the monitor 41.

The video signal is processed into a B or composite video signal and supplied to the monitor 41 via the output signal line 30. A synchronizing signal generating circuit 31 provided in the signal processing bag [28 is connected to the signal processing circuit 2
In addition to supplying a horizontal synchronization signal and a vertical synchronization signal to the diaphragm control circuit 9 and the aperture control circuit 40, the synchronization signal is also supplied to the motor control circuit 37, and the control timing of the motor control circuit 37 is set.

Next, the aperture control circuit 40 shown in FIG. 1 will be explained.

The input terminal l is connected from the signal processing area i1'829 to the CCD2.
The output electric signal of No. 4 or the video signal processed by the signal processing circuit 29 is manually inputted. Input terminal l: An amplifier 2 is connected to this, and an electronic switch 3 is connected to the output terminal of the amplifier 2. A clamp circuit 4 is connected to the output terminal of the electronic switch 3 for setting the absolute voltage value of the black level of the electrical signal or video signal input to the input terminal 1.

A smoothing/holding circuit 5 that performs smoothing and holding functions is connected to the output terminal of the clamp circuit 4.

The smoothing/holding circuit 5 includes a diode 6, a capacitor 7 connected to the cathode side of the diode 6 and having one terminal installed, a resistor 8 connected in parallel with the capacitor 7 to the cathode side of the diode 6, and It consists of a series connection branch of an electronic switch 9. The output terminal of the smoothing/holding circuit 5 is connected to a voltage follower circuit 10, and the output terminal of the voltage follower circuit 10 is connected to an inverting input terminal of an operational amplifier 14 via a resistor 11. Operational amplifier 14
A resistor 12 is connected between the inverting input terminal and the output terminal of the operational amplifier 14, and a sliding terminal of a variable resistor 13 is connected to the non-inverting input terminal of the operational amplifier 14. A DC voltage is supplied to the variable resistor 13 from a power source (not shown). An amplifier 15 is connected to the output terminal of the operational amplifier 14, and an output terminal 16 to which a DC motor (not shown) is connected is connected to the output terminal of the amplifier 15.

An output terminal of a monostable multivibrator 18 is connected to the control terminal of the electronic switch 3 and the control terminal of the electronic switch 9. The trigger input terminal of the monostable multivibrator 18 is an input terminal 1 to which a horizontal synchronization signal HD is applied.
7 is connected and the monostable multivibrator 18
The output terminal of the monostable multivibrator 20 is connected to the reset terminal of. An input trigger terminal of the monostable multivibrator 20 is connected to an input terminal 19 to which a vertical synchronizing signal VD is applied.

Next, the operation of the aperture control circuit 40 shown in FIG. 1 will be explained.

An output electric signal of the CCD 24 or a video signal processed by the signal processing circuit 29 is input to the input terminal 1 , amplified by the amplifier 2 and supplied to the electronic switch 3 . On the other hand, the input terminal 17 is connected to the synchronizing signal generating circuit 31 as shown in FIG. 4 (1).
A horizontal synchronizing signal HD as shown in FIG. A high level pulse signal appears at the output terminal 18. The output pulse signal of this monostable multivibrator 18 is supplied to an electronic switch 3.9 to
The electronic switches 3 and 9 are ON and connected only during the period T in which the output pulse signal 8 is at a high level. On the other hand, the input terminal 19 is supplied with a vertical synchronizing signal VD as shown in FIG. As shown in 4), a pulse signal that is at a high level for a predetermined period T4 approximately in the middle of the vertical scanning period of the vertical synchronization signal VD is output from the monostable multivibrator 20, and the pulse signal is output from the monostable multivibrator 20 to the reset terminal of the monostable multivibrator 18. is man-powered. The reset Hm of the monostable multivibrator 18 operates with negative logic and is active only during the period T4 when the output pulse signal of the monostable multivibrator 20 is at a high level. In this way, the electronic switch 3 is turned on and off by the output signal of the monostable multivibrator 18, so the signal input from the electronic switch 3 to the input terminal l is output from the monostable multivibrator 18 during the horizontal scanning period. There is only a period T during which the output pulse signal is at a high level, and this monostable multivibrator 1
8 itself is controlled by the monostable multivibrator 20, so that the output pulse signal of the monostable multivibrator 18 is controlled during the T1 period in which the output pulse signal of the monostable multivibrator 20 is at a high level during the vertical scanning period. It is limited to the T5 section where the level is high. This means that the electronic switch 3 is turned on during the T1 period in the vertical direction and the T5 period in the horizontal direction of the playback screen on the monitor. It should be noted that the respective periods of the fire synchronization signal HD not shown in (1) of FIG. 4 and of the vertical synchronization signal v[) shown in (3) of FIG.

An electric signal or a video signal input manually to the input terminal 1 in FIG. 1 is amplified by the amplifier 2 and has a waveform as shown by the solid line or broken line in FIG. 3(2). A horizontal synchronizing signal HD as shown in FIG. 3 (1) is input to the input terminal 17 in FIG. 1, and an output pulse signal as shown in FIG. The switch 3 is turned on and off by the output pulse signal shown in FIG. 3 (3). As a result, as shown in FIG. 3(4), the output terminal of the electronic switch 3 receives the electrical signal of FIG. 3(2) or the pulse signal of FIG. 3(2) only during the period when the pulse signal of FIG. A video signal is output. This means that only the vicinity of the center of the electrical signal or video signal shown in Figure 3 (2) is extracted by the pulse signal shown in Figure 3 (3), resulting in a waveform as shown in Figure 3 (4). means.

The voltage signal shown in FIG. 3(4) outputted from the electronic switch 3 is set to the absolute voltage value of the black level by the clamp circuit 4. That is, the absolute voltage value of the 0-level reference line of the voltage waveform shown in FIG. 3(4) is applied by the clamp circuit 4. The output signal of the clamp circuit 4 is sent to the smoothing/holding circuit 5.
is applied manually, resulting in a voltage waveform as shown in FIG. 3 (5). That is, the voltage signal input to the smoothing/holding circuit 5 is rectified by the diode 6 and charged to the capacitor 7, so that the signal waveform is smoothed. When the output voltage value of the clamp circuit 4 becomes lower than the voltage level due to the charge charged in the capacitor 7, the diode 6 is cut off. When the electronic switch 9 is in the ON state, the electric charge charged in the capacitor 7 is
It is discharged via the electronic switch 9 with a time constant determined by the capacitance of the capacitor 7 and the resistance value of the resistor 8, but when the electronic switch 9 is in the OFF state, the charge stored in the capacitor 7 is not discharged. Retained. Since the electronic switch 9 is controlled by the output pulse signal of the monostable multi-bi break 18 shown in FIG. 3 (3), a voltage waveform as shown in FIG. 3 (5) is output from the smoothing/holding circuit 5. becomes. That is, it is sampled during a period T during which the output pulse signal of the monostable multivibrator 18 is at a high level, and held during a period T during which the output signal from the monostable multivibrator 18 is at a low level.

In this way, by the functions of the electronic switch 3.9, the smoothing/holding circuit 5, etc., as shown in FIG. 3, an image is reproduced on almost the entire horizontal surface of the monitor screen indicated by the solid line in FIG. 3 (2). In the case of a subject whose image is reproduced only in the approximate center of the monitor screen as shown by the broken line in figure (2), the electronic switch as shown in figure (4) If only the waveform in the approximate center is extracted in step 3, the same figure (2) will also be obtained for the object indicated by the solid line in figure (2).
In the case of the object indicated by the broken line, the voltage waveforms are approximately the same.As a result, as shown in (5) in the same figure, the output voltage waveform of the smoothing/holding circuit 5 is equal to the voltage waveform for both the object indicated by the solid line and the object indicated by the broken line. The voltage value will be between -.

The output voltage signal of the smoothing/holding circuit is input to the operational amplifier 14 via the voltage follower circuit 10. In the operational amplifier 14, since the reference voltage value for setting the median brightness of the playback screen is manually applied to the non-inverting input terminal via the variable resistor 13, the reference voltage value and the human input are connected to the inverting input terminal side. The voltage value of the difference between the voltage value and the output signal of the voltage follower circuit lO is amplified by a gain set by a resistor 11.12, further amplified by an amplifier 15, and then output to an output terminal 16.
The signal is input to an electronic motor (not shown) that controls the aperture 36 shown in FIG.

In this way, the aperture 36 is controlled at a level that corresponds to the level of the video signal at approximately the center in the horizontal and vertical directions of the subject image reproduced on the monitor, and the diaphragm 36 is controlled at a level that corresponds to the level of the video signal at approximately the center in the horizontal and vertical directions of the subject image reproduced on the monitor. The area set in the center is illuminated with the most appropriate amount of light, resulting in an optimal image.

Note that in this embodiment, the center of the reproduced image is extracted in both the vertical and horizontal directions, but it is not always necessary to extract the median values in the vertical and horizontal directions; The median value of only one of the directions may be extracted.

[Effects of the Invention] In the signal processing device for an electronic endoscope of the present invention, the output electric signal or video signal from the image sensor is extracted only during a predetermined period approximately in the middle of the vertical scanning period and/or the horizontal scanning period. The aperture that limits the irradiation light is controlled based on the extracted signal level, so no matter what angle of view the subject is viewed from, the brightness of the central part that is most wanted to be observed is reproduced on the monitor at the optimum brightness. , it can be widely applied to various objects reproduced on a monitor in different areas without any manual scanning.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an embodiment of the aperture control circuit of the signal processing device for an electronic endoscope according to the present invention, and Fig. v2 is a circuit diagram showing a combination of the signal processing device for an electronic endoscope according to the present invention with a light guide and a monitor. 3 is a waveform diagram showing an example of the waveform of each part of the circuit in FIG. 1. FIG. 4 is a block diagram showing an example of the configuration for displaying a subject image using FIG. 5 is a waveform diagram showing a trigger signal waveform and an output waveform. FIG. 5 is a waveform diagram for explaining the operation of a conventional signal processing device for an electronic endoscope. 3.9... Electronic switch, 4... Clamp circuit, 5... Smoothing/holding circuit, 10... Voltage follower circuit, 18, 20... Monostable multivibrator, 21...
・Light guide, 22...Subject, 23, 32.3
5...Lens, 24...CCD. 27... Optical fiber, 28... Signal processing device,
29... Signal processing circuit, 31... Synchronous signal generation circuit, 33... Rotating plate, 34... Motor, 3
6... Aperture, 37... Motor control circuit,
38...Light source lighting circuit, 39...Light source, 40...
- Aperture control circuit, 41...monitor.

Claims (1)

[Scope of Claims] 1. A light source that emits light to irradiate a subject, an aperture that controls the amount of light from the light source, an aperture control means that controls the operation of the aperture, and a light source that is proportional to the amount of light reflected from the subject. A signal processing device for an electronic endoscope, comprising a signal processing means for processing an electric signal into a video signal, and a synchronization signal generation means for supplying a vertical synchronization signal and a horizontal synchronization signal of the video signal to the signal processing means, etc. The aperture control means includes: extraction means for extracting the electric signal or video signal only during a predetermined period approximately in the middle of the vertical scanning period of the vertical synchronization signal and/or the horizontal scanning period of the horizontal synchronization signal; a smoothing means for smoothing the extracted electric signal or video signal; a holding means for holding the voltage level of the electric signal or the video signal smoothed by the smoothing means for a predetermined period; and a voltage level held by the holding means. A signal processing device for an electronic endoscope, comprising: a drive means for controlling the operation of the aperture according to a voltage level.