RECEIVING SIGNAL DISCRIMINATING SYSTEM FOR ULTRASONIC AUTO-FOCUSING DEVICE

PURPOSE:To take out only ultrasonic reflected waves and to extend an automatic range finding range, by comparing and processing a stored ultrasonic receiving signal of the first range finding cycle and an ultrasonic receiving signal of the second range finding cycle. CONSTITUTION:RAMs 5 and 6 are controlled to be switched through a read/ write controlling circuit 8 so that one and the other are set to the read mode and the write mode alternately in every ultrasonic range finding cycle. An ultrasonic receiving signal of the first range finding cycle passing through an OR gate o from the RAM5 or 6 and an ultrasonic receiving signal of the following second range finding cycle are applied to an AND gate 10, and noise or the like is eliminated through the gate 10 to take out only ultrasonic reflected waves. As a the automatic range finding range due to ultrasonic waves in a TV camera or result, the like is extended.