JPH0449099B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic exposure device, and particularly to an automatic exposure device used in an endoscopic photographing system.

When taking automatic exposure photographs of the inside of a body cavity using an endoscopic imaging system, there is a limit in which automatic exposure control cannot be performed for flash light as the photographing light in close-range photography. It becomes overexposed. As a means for preventing overexposure in such close-range photography, Japanese Patent Application Laid-Open No. 10127/1984 discloses that a diaphragm is inserted into the photographing light source when it is determined that the automatic exposure limit has been reached. However, endoscopes illuminate objects through light guides for observation and photography. For this reason, when a diaphragm is provided between the light source and the light guide, the angle at which the photographing light enters the light guide changes, which changes the illumination angle of the object and deteriorates the light distribution of the illumination light to the object. If the light distribution inside the body cavity deteriorates, the quality of the photographic image will deteriorate, making it impossible to make an accurate diagnosis. for example,
Accurate diagnosis becomes difficult because the condition of a diseased part of a gastric ulcer or the like, ie, the degree of unevenness of the diseased part and the depth of the ulcer, are not clearly shown. Also, in JP-A No. 55-147619,
A method of adjusting automatic exposure using an ND filter has been disclosed, but since such a method does not control in real time, the exposure value may differ when metering a moving subject, resulting in an incorrectly exposed photo. There is a problem with it.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an automatic exposure device for an endoscope photographing system that can obtain properly exposed photographs even when photographing at close ranges exceeding the automatic exposure photographing limit using photographic light.

Embodiments of the present invention will be described below with reference to the drawings. According to FIG. 1, an endoscope 1, a light source unit 2
The endoscope camera 3 constitutes an endoscope photographing system. The endoscope 1 is provided with an image guide 5 and a light guide 6, and a subject 4 is illuminated by light guided through the light guide 6.
An objective lens 7 is provided at the front end of the image guide 5, and an eyepiece lens 8 is provided at the rear end. A camera 3 is glued to the eyepiece 9, and a beam splitter 10 of the camera 3 faces the eyepiece 8. A film 11 is placed opposite a beam splitter 10 with a mirror shutter 12 in between. The camera control circuit 13 is connected to a light receiving element 14 and a release switch 15 provided on the side surface of the beam splitter 10. A signal end of the camera control circuit 13 is connected to a connection pin 16. The light source unit 2 is provided with a xenon (Xe) discharge lamp 18.
The connector portion 20 is connected to the light source unit 2 such that the light guide end 19 is located on the optical axis of the light source unit 2.
The connection pin 21 of the connector part 20 is connected to the light source unit 2.
The light source control unit 17 is connected to the light source control unit 17 through the socket. The Xe discharge lamp 18 is composed of a cathode 22 and an anode 23 facing each other, and a reflecting surface 24. Xe discharge lamp 18 and light guide end 1
A condenser lens 25, a shutter blade 26, and an aperture blade 28 are sequentially arranged between the lens 9 and the shutter blade 9. The shutter blades 26 are driven by a shutter solenoid 27, and the aperture blades 28 are driven by an aperture motor 29. A light guide member 3 made of, for example, an acrylic rod between the light guide end 19 and the aperture blade 28
1 is arranged. The tip of the light guiding member 31 has an inclined surface facing the lamp 18, and the light receiving element 32 is disposed at the rear end. In FIG. 2, the shutter blade 26, the aperture blade 28, the light guide member 31, etc. are shown in perspective.

FIG. 3 shows the circuit configuration of the camera control circuit 13. According to this circuit, the light receiving element 14 is connected to an operational amplifier 36 of an integrator/current/voltage converter 37. An integral capacitor 34 and a current-voltage conversion resistor 35 are connected in series between the inverting input terminal and the output terminal of the operational amplifier 36. Short-circuit analog switches 38 and 39 are connected to the integral capacitor 34 and the resistor 35, respectively. The output terminal of the integrator and current-voltage converter 37 is connected to the operational amplifier 4 of the comparator 40.
It is connected to the non-inverting input terminal of 1. operational amplifier 41
The inverting input terminal of is connected to the 1-chip CPU 33 via the DD/A converter 42. operational amplifier 4
The output terminal of 1 is connected to the non-inverting input terminal of an operational amplifier 47 of the buffer circuit 43 via an analog switch 44. Further, the non-inverting input terminal of this operational amplifier 47 is connected to the output terminal of the operational amplifier 36 via an analog switch 45. Analog switches 44 and 45 are opened and closed by the output signal of CPU 33, and analog switch 45 is controlled by a signal via inverter gate 46. The inverting input terminal of the operational amplifier 47 is grounded via a resistor 48 and connected to an output terminal via a resistor 49. The output end of this buffer circuit 43 is connected to terminal e. Terminal f is grounded, terminals a and b are
Connected to Vcc and GND respectively. Terminals c and d are connected via serial interface 50.
Connected to CPU33. The CPU 33 includes an inverter 51, a light emitting diode (LED) 52, and a resistor 5.
Connected to Vcc via 3.

FIG. 4 shows the light source control circuit 1 of the light source unit 2.
7 circuit configurations are shown. In this circuit, terminals c and d are serial interface 5
Connected to 4. serial interface 54
is the CPU55, ROM56, RAM5 via the bus.
7, A/D converter 58, D/A converter 5
9, connected to a condition setting display unit 60 and a parallel interface 61. Terminal e is connected to non-inverting input terminals of operational amplifiers 64 and 67 of low amplification amplifier circuit 62 and high amplification amplifier circuit 63. The inverting input terminal of the operational amplifier 64 is grounded via a resistor 65 and connected to the output terminal via a feedback resistor 66. Similarly, resistors 68 and 69 are connected to the inverting input terminal of operational amplifier 67. The output terminal of the amplifier circuit 62 is connected to the non-inverting input terminal of the comparator 70. The output end of the comparator 70 is connected to the parallel I/F 61. The non-inverting input terminal of the operational amplifier 72 of the potentiometer amplifier circuit 71 is connected to the aperture potentiometer 30, and the inverting input terminal thereof is connected to resistors 73 and 74. Light receiving element 32
The current-voltage converter 75 connected to the operational amplifier 7
6 and a resistor 77. The output terminal of the D/A converter 59 is connected to the inverting input terminal of the operational amplifier 79 of the aperture driver 78, and the resistor 8
0 to the emitter of the transistor 82 and the aperture motor 29. The collector of the transistor 82 is connected to Vs via the resistor 81, and the base is connected to the output terminal of the operational amplifier 79.

FIG. 5 shows the power circuit of the light source unit 2. As shown in FIG. It is connected to a high voltage generation source consisting of a high voltage generation circuit 83 and a high voltage generation coil 84 of the Xe discharge lamp 18. This high voltage generation source is connected to a rectifier circuit 89 via an Xe lamp current control section composed of an Xe lamp current control circuit 85, a current detection resistor 86, and a current control transistor 87, and a chiyoke coil 90. A power terminal of this rectifier circuit 89 is connected to a secondary winding of a transformer 88 . The flash capacitor 91 is connected to a rectifier circuit 93 via a resistor 92. A power terminal of the rectifier circuit 93 is connected to a secondary winding of a transformer 94. The primary winding of the transformer 94 is connected via the triax 95.
Connected to AC current line. Triack 95
is connected to a capacitor charging voltage control circuit 96 that generates a control signal according to the charging voltage of the capacitor 91. One end of the capacitor 91 is connected to the transistor 9
7 emitter and a transistor drive circuit 98 . The collector of the transistor 97 is connected to the cathode of the Xe lamp 18, and the base is connected to the drive circuit. Power supply circuit 99 is connected to the AC line via transformer 100. The “CHARGE” signal from which the capacitor 91 is “CHARGE” UP from the capacitor charging voltage control circuit 96 is connected to the “CHARGE” terminal of the parallel I/F 61 . “FLASH” and “STOP” signals input to the transistor drive circuit 98 are connected to the parallel I/F 6
Input from 1.

In the above-described circuit, the A/D converter 58 has a built-in multiplexer and can output an 8-bit digital output, and specifically, ADC0808 manufactured by NS is used. This ADC0808 has 8 channels of analog inputs and 8 bits of digital output, but in the embodiment, 4 channels of analog inputs _A0 to _A3 are used. These inputs A ₀ to A ₃ are connected to the outputs of amplifier circuits 62, 63, 71 and current-voltage converter 75. The serial interface 54 and the CPU 55 are made by Intel.
If you are using 8085, you are part of that family.
Connected to camera 3 as UART using 8251A. The ROM 56 is selected according to the program capacity, and if the capacity is 2K bytes, the family 2716 is used. Further, 2114 is used for the RAM 57. The D/A converter 59 is used to convert 8-bit digital data into analog output, and specifically uses NS's DAC1008. This has the advantage of being directly connected to the data bus of the CPU 55. Note that since the analog output of this D/A converter 59 is a current output, it is converted into a voltage by the aperture driver 78. In addition, the A/D converter 5
The 8-bit resolution is effectively treated as 16-bit. The condition setting/display unit 60 controls shooting still film sensitivity, cine (TV) film sensitivity, still/cine correction during auto shooting, still auto/manual switching, cine auto/manual switching, and cine manual, that is, manual light intensity setting. I'm starting to be able to do it. The parallel interface 61 uses Intel's Family 8255A.

Next, the operation of the endoscopic imaging system described above will be explained. When the power supply circuit (Fig. 5) of the light source unit 2 is turned on, the Xe lamp 18 automatically lights up.
After this, the light source signal processing circuit (FIG. 4) initializes and performs preprocessing for pre-photographing exposure calculation according to the flowchart of FIG. 6. That is, when the ASA sensitivity etc. are set in the condition setting/display unit 60, only the setting data is output and stored in the RAM.
57. Flush capacitor 91
(Fig. 5) is determined to be "CHARGE" UP. If the determination is "YES", the multiplexer of the A/D converter 58 is set to _A3 . At this time, the parallel interface 61 outputs a "FLASH" signal. In response to this "FLASH" signal, the transistor drive circuit 98 of FIG.
turns on transistor 97. As a result, the charge stored in the capacitor 91 flows into the Xe lamp 18, causing the lamp to emit a high-intensity flash. At this time, the shutter blade 26 and the aperture blade 28
is open, and part of the flash light from the Xe lamp 18 is guided to the light receiving element 32 by the light guide member 31. The light receiving element 32 detects flash light as photographing light. The output of the light-receiving element 32 is amplified by a current-voltage converter 75 and converted into a voltage signal, which is input to the terminal A ₃ of the A/D converter 58 . The data is stored in the data RAM 57 of the A/D converter 58. It is determined whether 100 ms has passed since the start of the flash, and if the determination is "NO", the A/D converter 58 takes in the light reception data of the light receiving element 32 and stores it in the RAM 5.
Store in 7. If the determination is "YES", a "STOP" signal is output from the parallel interface 61. In response to this "STOP" signal, the transistor 97 is turned off, and the flashing of the Xe lamp 18 is stopped, resulting in normal light emission.A/ The received light data taken into the D converter 58 and stored in the RAM 57 is integrated and stored in the RAM 57 as a total flash light amount value L·t (lux·sec).

After the pre-processing of the pre-photographing exposure calculation is performed, endoscopic observation and endoscopic photographing are performed.

When performing endoscopic photography, the eyepiece section 9 of the endoscope 1
Camera 3 is attached to. At this time, the light receiving element 14 of the camera 3 receives reflected light from the subject via the image guide 5, the eyepiece 8, and the beam splitter 10. At this time, when the serial interface 54 detects that the camera 3 is connected to the endoscope 1, pre-photographing exposure calculation begins in accordance with the flowchart of FIG. That is,
First, the multiplexer of the A/D converter 58
The photometric data set in the _A3 channel and corresponding to the light receiving element 32 is taken into the A/D converter 58. This photometric data is data corresponding to illumination light, and is stored in the RAM 57 as an Lsend value.
A/D converter multiplexer is A ₀ or
A is set to ₁ , and the reflected light data corresponding to the reflected light from the subject from camera 3 is imported. The data of the A/D converter 58 is stored in the RAM 5 as the amount of reflected light Lrcv.
7 is stored. Next, a pre-photographing exposure value S is calculated based on the following equation.

S = K/ASA
Includes Lux/sec conversion value.

ASA: Film sensitivity Lsend: Incident light amount of the light guide Lsend/Lrcv: Reflection coefficient of the subject K/ASA determines the required light amount (Lux/Sec) on the film surface, and is a coefficient for converting this into illumination light. Includes loss factors such as ride guide and image guide.

It is determined whether the pre-photographing exposure value S obtained by the above calculation is larger than the total flash light amount value L·t. If this determination is "YES", inappropriate exposure is displayed. If the determination is "NO", it is determined whether the exposure light amount S is smaller than L.t/10. If this determination is "NO", appropriate exposure is displayed. If the determination is "YES", it is determined whether the exposure value S is smaller than L·t/40. If this judgment is “YES”, inappropriate exposure will be displayed; if “NO”, “FLASH” will be displayed.
Signal generation is prohibited. In addition, L・t/10 means the minimum automatic exposure light amount when the Xe lamp 18 flashes, that is, the shooting light automatic exposure lower limit light amount, and L・t/40 means the normal lighting light of the Xe lamp 18, that is, the observation light. Indicates the minimum automatic exposure light amount, that is, the observation light automatic exposure lower limit light amount.
This means that the above-mentioned two judgments determine whether the measurement light amount S is within the light amount range from the shooting light automatic exposure lower limit light amount to the observation light automatic exposure light amount, and within this light amount range, no photographing light is generated and observation is performed. Automatic exposure photography is performed using only light. Note that display of appropriate and inappropriate exposure is performed in the photographing condition setting display unit 60, and information on prohibition of generation of the "FLASH" signal is stored in the RAM 57.

By sequentially performing the above pre-photographing exposure calculation flow, it is possible to always know whether or not it is possible to photograph the object being observed with the appropriate exposure. Further, it is sequentially determined whether to generate flash light or to use normal lighting during the photographing.

Next, the operation after the release switch 15 is closed for photographing will be explained.

If it is determined in the pre-photographing exposure calculation that photographing can be performed properly, the photographing operation is performed according to the time chart shown in FIG.

That is, when the release switch 15 is closed at T1, the light source aperture 28 begins to open, the signals at the camera contact pins e to f become low level, the light source shutter 26 begins to close, and the light incident on the light guide end 19 is reduced. is shielded from light, and the integrator/current-voltage converter 37
The output of becomes 0 value. Camera 3 at T2 after a predetermined time
The mirror shutter 12 opens and the light source shutter 26 opens.
When opened, light enters the light guide end 19, and the output of the integration/current-voltage converter 37 operates as an integrator to integrate the light reception signal corresponding to the reflected light from the object. At time T3 when the light source shutter 26 is fully opened, the Xe lamp 18 flashes. When the calculated exposure value reaches the appropriate exposure value, a “STOP” signal is generated and the Xe lamp 18
The light emission is stopped at T4, and after a certain period of time, at T5, the mirror shutter 12 is closed and the release switch 15 is opened to complete the photographing. After this, Xe lamp 1
8 normally lights up and returns to the observation state. Note that Vref in exposure calculation is determined by the ASA setting provided on the camera, and since the light source is also set to the same ASA, exposure calculation before shooting is possible.

Next, the operation of close-range photography under the condition of L・t/10<S<L・t/40, that is, automatic exposure photography that is not based on the flashing light of the Xe lamp 18, is performed according to the time chart in Fig. 8. I will explain. In this case, the mirror shutter 12 of camera 3 begins to open at T2, and
When the mirror shutter 12 is fully opened, the "FLASH" signal is not generated, so the Xe lamp 1
8 is lit normally without flashing, that is, the observation light is incident on the light guide end 19. The observation light passes through the light guide 6, and the reflected light from the nearby subject 4 enters the camera 3 via the image guide 5, exposing the film 11 in the camera 3 and converting it into a light reception signal by the light receiving element 14. Ru. The received light signal is integrated by the integrator and current-voltage converter 37, but since a large amount of reflected light enters the camera 3 even with observation light due to close-up photography, the integration time is short and the integrated voltage becomes the reference voltage Vref at T4. . A “STOP” signal is generated at this T4. The CPU 55 generates a "SHUTTER CLOSE" signal in response to the "STOP" signal to close the shutter 26. Thereafter, at T5, the mirror shutter 12 is closed and the release switch 15 is opened to complete close-up photography. In this way, in close-range photography, automatic exposure photography is performed without generating photographing light and using low-light observation light as photographing light, so even in fairly close-up photography, a properly exposed photograph can be obtained without overexposure.

Next, several embodiments will be described with reference to FIG. In this embodiment, a light receiving element 32 is arranged near the Xe lamp 18 so as to detect observation light and photographing light. Since the other configurations are the same as those of the embodiment shown in FIG. 1, the same reference numerals are given and the explanation will be omitted. However, in the case of this embodiment, since the maximum light amount L·t for photography of 100 msec cannot be measured, the exposure time t is calculated by the following equation (2).

t (msec) = K/ASA×L×1/S×F (2) L: Light reception signal corresponding to the reflected light from the subject S: Amount of aperture F: Flash magnification 10<t _F <100 (3 ) t _F < 10 10 < t _NF < 250 (4) t _F : Exposure time during flash t _NF : Exposure time during non-flash The automatic exposure range during flash is determined by formula (3), and the automatic exposure range during non-flash The exposure range is determined using equation (4). However, the formula
In the case of (4), the flash magnification F is not calculated. In the case of non-flash, the exposure time starts from 10 msec, but automatic exposure is possible up to the maximum exposure time of the camera 3's shutter time, that is, 250 msec. If the exposure light at t _F = 10 msec is less than the exposure amount at t _NF = 250 msec, it means that the continuous photographing range has been expanded. still,
The flash magnification F can be calculated from the light reception signal corresponding to the observation light and the light reception signal corresponding to the flash light. In the case of non-flash light, t may be calculated by omitting the lower term of equation (2), and in this case, the exposure range is determined as shown in equation (4).

As explained above, according to the present invention, when photographing at close range, the light source is not flashed and the close-range subject is illuminated using normal lighting, so overexposure at close range can be prevented without impairing the light distribution of the illumination. Ru. In addition, exposure calculations are performed in real time even when shooting from close range, so even moving subjects can be photographed with fairly appropriate exposure.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of an endoscopic imaging system using an automatic exposure device according to an embodiment of the present invention;
Fig. 2 is a perspective view of the diaphragm mechanism and shutter mechanism, Fig. 3 is a circuit diagram of the camera, Fig. 4 is a circuit diagram of the signal processing circuit of the light source unit, Fig. 5 is a circuit diagram of the power supply circuit, Fig. 6 7 is a flowchart explaining the pre-processing of pre-shooting exposure calculation, FIG. 7 is a flowchart explaining the operation of pre-shooting exposure calculation, and FIG. 8 is a time chart explaining the shooting operation of automatic exposure shooting using shooting light. 9 is a time chart explaining automatic exposure photographing operation using observation light, and FIG. 10 is a schematic configuration diagram of an endoscope photographing system using an automatic exposure device according to another embodiment. . 1... Endoscope, 2... Light source unit, 3... Camera, 5... Image guide, 6... Light guide, 9... Eyepiece, 12... Mirror shutter, 1
3... Camera control circuit, 14... Light receiving element, 15
...Release switch, 17...Light source control circuit,
18... Xe discharge lamp, 19... Light guide end, 31... Light guiding member, 32... Light receiving element, 33
...CPU, 55...CPU.

Claims (1)

[Scope of Claims] 1. An illumination device that irradiates illumination light toward a subject; A control device that controls the illumination device to emit a constant amount of light during observation, and increases the constant amount of light to control flash emission during photography; a first light receiving element that receives illumination light from the illumination means; a second light receiving element that receives reflected light of the illumination light from the subject; and outputs from the first and second light receiving elements during observation prior to photographing. determining means for calculating a pre-photographing exposure value based on the ratio and determining whether or not the calculated exposure value is within an exposure control limit during flash emission of the illumination means; and the calculated exposure value. is larger than the lower limit of exposure control during flash emission, the control means is set to a flash emission enabled state, and when the calculated exposure value is smaller than the exposure control lower limit during flash emission, the control means is set to a flash emission disabled state. An automatic exposure device for an endoscope photographing system, comprising: a switching means for controlling the emission of a constant amount of light; and a light control means for stopping the flash emission based on the output of the second light receiving element during flash photography. .