Operating circuit for pulsed reflected light beam monitor - generates light beam pulses and detects reflected beam in single phase-locked circuit

摘要

An operating circuit is for use with a reflected visible or invisible light beam monitor. It is insensitive to other light disturbances and uses an interval phase locked loop to relate the generated light beam pulses and the reflected returning pulses. The central integrated circuit (1) consists of an oscillator (2) producing a rectangular waveform and driving an amplifying and differentiating stage (8) which, in turn, feeds a l.e.d. (9). Reflected light is detected by a phototransistor (11) which feeds a phase comparator (4) via a differentiating capacitance. This comparator is also fed by the original signal, and the output affects the original oscillator (2) frequency to form an overall phase locked loop with high immunity to external disturbances.