Laser remote sensing device according to the running time measurement principle of a light pulse

摘要

This device operates in accordance with the principle of measuring the transit time of a light pulse. The light beam (j1) emitted by a transmitting diode (14) fed by a laser pulse generator (10) passes to a transmitter lens (12). The greatest proportion of the light beam is directed to a target object. The light rays (j3) reflected from the target object pass to a receiving diode (23) of a measuring channel (I). A small proportion of the light beam (j1) emitted by the transmitting diode is dispersed at the transmitter lens and conducted as reference beam (j2) to a receiving diode (15) of a reference channel (II). Each of the receiving diodes is allocated one parallel resonant circuit (17; 16) each as load impedance. The emitted laser pulse triggers the reference and the measuring channel in optical manner. To obtain the time-significant signal edges, the first sinewave zero crossing is detected in the reference channel and the second sinewave zero transition of the sinusoidal oscillation started in the relevant parallel resonant circuit is detected in the measuring channel. The sensitivity of the device can be increased by the galvanic isolation between the transmitter and receiver. Using a parallel resonant circuit as load impedance has the further advantage that the optical filters previously required are no longer needed. IMAGE