PURPOSE: To increase the hightness of a displaying image and the picture quality, by supplying the output signal of an infrared ray detector to a differential amplifier directly and via a delay line and reversing the difference of both inputs in phase every prescribed time to obtain a video signal.
CONSTITUTION: An infrared ray (a) radiated from a subject 1 of observation is switched with an infrared ray (b) radiated from a reference light source 4 in a prescribed period, and these rays are made incident to an infrared ray detector 5. The output signal of the detector 5 is branched to two lines, and one of these two lines is delayed 6 by a prescribed time to the other. Then both signals are supplied to a differential amplifier 7. The output of the amplifier 7 is supplied to the 2nd differential amplifier 8 via a siwtch S which is switched with every above-mentioned prescribed time. Then the video signal is extracted out of the amplifier 8. Thus the signal from which the correspondence component of radiation due to the radiation from a subject and given from the light source 4 is eliminated can be obtained for a time of about double as much as conventional. As a result, both the brightness of a display image and the picture quality are increased.
ISHIBASHI HIROSHI
TSUJINO YOSHINORI
