TARGET DETECTOR FOR ERASING SENSITIVITY WITHIN SPECIFIED DISTANCE

摘要

PURPOSE: To suppress or remove excess electromagnetic radiation reflected from a target by arranging a second radiation detector on a receiver assembly to receive a target radiation reflected from a target located within a predetermined distance. CONSTITUTION: A second photodetector 30 is arranged in a region of a slot 28 where a light beam reflected from a target within a distance related to a receiver assembly 10' is introduced. Consequently, the photodetector 30 receives intensive reflected light beam only of the direct light beam when the target approaches an input hole 16. Output signal from the photodetector 30 is fed to a gain block 32 thence to the inverted input of an amplifier 34. Since the amplifier 34 operates to subtract the output signal of the photodetector 30 from the output signal of a first photodetector 14, the components of a target radiation R generated through internal reflection and scattering and received by the photodetector 14 can be eliminated effectively.