VERFAHREN UND VORRICHTUNG ZUR OPTISCHEN UEBERWACHUNG UND SICHERUNG VON RAEUMEN GEGEN EINDRINGLINGE

摘要

An active optical monitoring device comprises a transmitter (S) and a receiver (E). The transmitter (S) regularly transmits modulated light pulses in a spatial sector and simultaneously transmits synchronous pulses to the receiver (E). The receiver (E) receives the light detected by its optical system and converts it into electric signals. These signals are filtered in a bandpass filter, amplified in a pre-amplifier (7) and rectified in a rectifier (8). In the pause between two light pulses, the basic optical level is defined in a sample-and-hold circuit (10) which is controlled by one synchronous pulse ( phi 2). The output signal of the rectifier (8) is amplified in an amplifier (9) during the light pulse duration. In a differential amplifier (11), the basic level is subtracted from the signal present during the light pulse duration. Via an analog switch (12) which is actuated by the synchronous pulse ( phi 1) for the duration of the light pulses, the signal is sent to a root extractor (13), post-amplified in an amplifier (14) and forwarded via a further analog switch (15) which is also controlled by the synchronous pulse ( phi 1) to an evaluation and alarm circuit. <IMAGE>