JPH0211884B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to an illumination device that provides illumination light to an illumination window at the tip of an endoscope insertion section.

"Prior art and its problems" As is well known, an endoscope illumination device guides the light from its light source lamp to the illumination window at the tip of the body insertion part through a light guide made of an optical fiber bundle, and illuminates the inside of the body cavity. It illuminates the observation section of the Conventionally, this illumination device is provided with a light amount adjusting means in order to keep the brightness of the observation section constant regardless of the distance from the illumination window to the observation section. As one means for adjusting the amount of light, a device is known in which the brightness of a light source lamp is kept constant, a variable aperture device is provided in the optical path between the lamp and the light guide, and this variable aperture device is driven by a servo motor. ing. However, this conventional device
Since there is a limit to the response speed of the servo motor, there is a problem in that the response speed of the variable throttle device is slow. In other words, in an endoscope, the body-inserted part enters the pinched lumen, so the distance between the tip of the endoscope and the observation part often changes rapidly. In contrast, the response of the mechanically variable diaphragm device may be delayed. For this reason, the brightness of the screen is not constant, especially during television shooting and cinema shooting, and control of the mechanical aperture is complicated and difficult.

On the other hand, in a lighting device that uses a tungsten lamp or other lamp in the light source section whose illuminance changes depending on the magnitude of the applied voltage, the observation section can be controlled by controlling the applied voltage of the lamp without using a mechanical diaphragm. Brightness can be changed.
Although this conventional device can change the amount of illumination light with a fast response speed to changes in the brightness of the observation section (subject), there is a problem in that the range in which the amount of light can be changed is narrow. That is, in order to vary the amount of light over a wide range, a current lower than the holding current must be passed through the lamp, which may change the color temperature of the lamp, which may impede accurate diagnosis.

``Object of the Invention'' The present invention has been made by focusing on the problems of the conventional illumination device, and is capable of changing the amount of light with good responsiveness to changes in the brightness of the observation section. It is an object of the present invention to provide an endoscope illumination device that allows a wide range of change in light amount and also does not cause a change in color temperature.

"Summary of the Invention" The endoscope illumination device of the present invention includes a lamp current changing means that changes the lamp current of the discharge tube according to the brightness of the observation section, and is inserted between the discharge tube and the light guide. The present invention is characterized in that the amount of illumination light can be changed over a wider range by providing an optical filter that can be removed from the lamp, and making the lamp current changing means cooperate with the optical filter.

"Embodiments of the Invention" The present invention will be described below with reference to illustrated embodiments. In FIG. 1, light from a discharge tube 10 passes through a light guide 21 of an endoscope to an object (observation section) 22.
The reflected light from the subject 22 enters the television camera 25 via the image guide 23 and beam splitter 24. Beam splitter 24
The separated light is converted into a voltage by a photoelectric conversion element 30, and this voltage is amplified by an amplifier 31. The difference between this amplified voltage and the reference voltage obtained by the exposure level adjustment circuit 41 is amplified by the differential amplifier 40, and the discharge tube drive transistor 50 is activated according to the output value of the differential amplifier 40. Controls the amount of energization of 10.

The lower and upper limits of the current applied to the discharge tube driving transistor 50 are limited by the lamp current limiting circuit 60. That is, the lamp current limiting circuit 60 limits the lamp current of the discharge tube 10 between an upper limit value (near the rated current of the discharge tube 10) and a lower limit value (near the holding current of the discharge tube 10). The discharge tube 10 has a characteristic that it operates stably without any change in color temperature at a voltage value between the rated current and the holding current. In order to set the upper limit value, a constant voltage circuit consisting of a Zener diode 61 and a resistor 62, and a diode 63 directed to this constant voltage circuit are used. Further, in order to set the lower limit value, voltage dividing resistors 64 and 65 and a diode 66 extending from the voltage dividing point to the base of the discharge tube drive transistor 50 are used. In this example,
The upper limit value is 20A and the lower limit value is 10A.

The optical filter 80 is provided in the optical path between the light guide 21 and the discharge tube 10 so as to be movable back and forth.
An optical filter insertion/removal control circuit 70 is provided to control insertion/removal of the optical filter. The optical filter insertion/removal control circuit 70 inserts/removes the optical filter 80 according to the output voltage of the differential amplifier 40, and includes a reference voltage source 72 and a comparison circuit 71 for detecting an upper limit value, and a comparison circuit 71 for detecting a lower limit value. Reference voltage source 7
4 and a comparison circuit 73, a flip-flop 75 that stores the outputs of the comparison circuit 71 and the comparison circuit 73 and outputs an insertion signal and an extraction signal for the optical filter 80, and a drive transistor 76 that drives a solenoid 77. 77 drives the optical filter 80.

Next, the operation of the above embodiment will be explained. When the amount of light reflected from the subject 22 changes due to a change in the distance between the endoscope tip and the subject 22, the output of the photoelectric conversion element 30 and the differential amplifier 4 change.
0 changes, the discharge tube drive transistor 50
The drive current changes to compensate for the change in the amount of reflected light.

In this case, if the base voltage of the discharge tube drive transistor 50 becomes even slightly higher than the value corresponding to the rated current of the discharge tube 10, excess current flows to the ground via the diodes 63 and 61. A current exceeding the rated current does not flow through the discharge tube 10. Conversely, if the base voltage of the discharge tube drive transistor 50 becomes even slightly lower than the value corresponding to the holding current of the discharge tube 10, the discharge tube drive transistor 50 is disconnected from the power supply via the resistor 65 and the diode 66. Since it flows to the base, discharge tube 10
A current less than the holding current does not flow through.

FIG. 2 is a time chart of the above embodiment. First, when the lamp current reaches 19A or more, which is close to the upper limit current of 20A, an escape signal is output from the flip-flop 75, and the lamp current increases to the lower limit current of the discharge tube.
It is preset so that the insertion signal is output from the flip-flop 75 when the voltage is close to 10A and less than 11A.

Now, consider a state in which the optical filter 80 is inserted into the optical path (time point T in the figure). That is,
Drive transistor 76 is off and solenoid 77 is not activated. In this state, as the tip of the endoscope gradually moves away from the subject 22, the reflected light from the subject 22 that is input to the photoelectric conversion element 30 gradually weakens, so that the differential amplifier 40 and the discharge tube drive transistor 5
0, the discharge tube 10 gradually becomes brighter. When the lamp current exceeds 19A, an escape signal is output from the flip-flop 75 and the drive transistor 76 is turned on, so the solenoid 7
7 is activated, and the optical filter 80 escapes from the optical path.

When the optical filter 80 escapes from the optical path, the photoelectric conversion element 30 suddenly receives a large amount of light, so the light from the discharge tube 10 suddenly decreases due to the feedback loop, and the lamp current drops to around 11A. . Therefore, since there is room to increase the lamp current again, the distal end of the body insertion part can be further separated from the subject 22. Then, as the tip of the endoscope moves away from the subject 22, the lamp current gradually increases to exceed 19A, but at this time the optical filter 80 does not issue an escape signal (it has already escaped). ). When the current reaches 20A, the lamp current limiting circuit 60 holds it at 20A.

Conversely, when the subject 22 approaches, the discharge tube 10 gradually becomes darker as described above. And when the lamp current becomes less than 11A, the flip-flop 75
An insertion signal is output from the drive transistor 76.
is turned off, so the solenoid 77 is deactivated and the optical filter 80 is inserted into the optical path.

When the optical filter 80 enters the optical path, the amount of light received by the photoelectric conversion element 30 suddenly decreases, so the feedback loop causes the light from the discharge tube 10 to suddenly increase, causing the lamp current to approach 19A. . Therefore, since there is room to reduce the lamp current again, the distal end of the body insertion part can be brought closer to the subject 22. Then, as the tip of the endoscope moves closer to the subject 22, the lamp current gradually decreases, and finally, the lamp current is held at 10 A by the current limiting circuit 60. Even when the current is below 11A, the optical filter 80 has already been inserted, so no insertion signal is output.

What must be taken into account here is to determine the light transmittance of the optical filter so that the lamp current does not exceed 19 A when the optical filter 80 is inserted.
When the optical filter 80 is inserted, the lamp current
If the voltage exceeds 19A, an escape signal will be output at the moment of insertion, so escape and insertion will be repeated, causing an oscillation phenomenon. In order to prevent this, it is preferable to set the light transmittance of the optical filter 80 to 50% or more.

Photoelectric conversion element 30 that detects the brightness of the subject →
A differential amplifier 40 that detects the difference between the output of this photoelectric conversion element 30 and a reference voltage → a discharge tube drive transistor 50 that controls the lamp current by the output of this differential amplifier → a discharge tube drive transistor 50 that is driven by this drive transistor 50 The feedback loop of the discharge tube 10→the brightness of the object illuminated by the discharge tube 10 has an extremely fast response. It is possible to obtain a response speed of 1ms or less. Therefore, instantaneous changes in light intensity caused by insertion and removal of the optical filter 80 are also fed back, so visual observation and
During television photography or cine photography, this change in light amount is not perceptible to the naked eye, and therefore stable images can be obtained without any hindrance to observation or photography. In addition, since the optical filter 80 is inserted and removed from the optical path, the discharge tube 1
Since the amount of energization at 0 is not lower than the holding current, no change occurs in the color temperature of the lamp.

The value of the lamp current that causes the optical filter 80 to output the escape signal (19A in the above embodiment) and the value of the lamp current that causes the optical filter 80 to output the insertion signal (11A in the above embodiment) are determined depending on the characteristics of the lamp. It can be determined arbitrarily. Further, if the optical filter 80 uniformly attenuates light,
The material does not matter.

"Effects of the Invention" As described above, the present invention changes the amount of illumination light through the cooperation of both the lamp current changing means and the optical filter, so the amount of illumination light can be spread over a wide range and with good responsiveness. It can be changed. Further, since the lamp current is not lowered below the holding current, the color temperature does not change, and therefore, the possibility of misdiagnosis can be eliminated. Furthermore, unlike conventional devices, this device does not use expensive elements such as servo motors, so it is inexpensive, and the circuit configuration is simple, so high reliability can be obtained.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the illumination device for an endoscope according to the present invention, and FIG. 2 is a time chart of this embodiment. DESCRIPTION OF SYMBOLS 10... Discharge tube (illumination lamp), 21... Light guide, 22... Subject (observation part), 30... Photoelectric conversion element, 40... Differential amplifier, 60... Lamp current limiting circuit, 70... Optical filter insertion/removal control circuit.

Claims (1)

[Scope of Claims] 1. In an endoscope illumination device that illuminates an observation section with light from a discharge tube through a light guide and an illumination window at the tip of the body-inserted section, a photoelectric conversion element that detects the brightness of the observation section. and; lamp current changing means for changing the lamp current of the discharge tube between the vicinity of the holding current of the discharge tube and the rated current according to the output of the photoelectric conversion element; An endoscope, comprising: an optical filter to be inserted and removed; and an optical filter insertion/removal control means for inserting and removing the optical filter into the optical path at a level near the holding current or rated current of the discharge tube. lighting equipment. 2. The illumination device for an endoscope according to claim 1, wherein the optical filter has a light transmittance of 50% or more. 3. In claim 1 or 2, the lamp current changing means includes a differential amplifier that detects a difference between an output value of a photoelectric conversion element and a reference value;
An endoscope illumination device comprising current control means for controlling lamp current according to the output value of the differential amplifier.