PULSE RADAR

PURPOSE:To improve distance measurement accuracy by a means for changing a threshold value and by calculating reception pulse rise time with a plurality of threshold values utilized. CONSTITUTION:Since threshold voltage input to a comparator COMP via a threshold changing means 5 is changed for every reception, the rise time of an output pulse of the COMP also changes for one pulse. In addition information on a reception level of a light receiver 2 is input to a microcomputer 3, and the threshold changing means 5 is controlled so that an appropriate threshold can be obtained according to the level. Thus a plurality of threshold values for each pulse input from the means 5 are set respectively at appropriate values according to their reception levels. Thus, based on output pulses from a flipflop 6 by a plurality of comparator outputs which have been detected sequentially at different thresholds for each of the reception, the rise time of the received pulse is determined by the microcomputer 3, and a distance to a target can be calculated based on the time.