| 摘要 |
PURPOSE:To prevent surely malfunction just after application of power supply by providing a period not outputting an object detecting signal to a counter circuit counting a period pulse. CONSTITUTION:A pulse is generated from a periodic pulse generating circuit 1 having a counter circuit CT, light is projected by a projecting means 2 and detected by a photodetecting means 3. A counter circuit 4 outputs a count-up signal V0 when the periodic pulse VCK reaches a prescribed value. An RS filp-flop circuit 5 is set by this signal V0, its output Q goes high and an object detecting signal VX is outputted to an output circuit 7 via a gate circuit 6 comprising an AND circuit. A reset circuit 9 consists of comparators CP1, CP2, an OR circuit, a reference power supply ES, a resistor R1 and a capacitor C1. The output of the comparator CP2 goes to a high level at the leading edge of a constant voltage power supply 8, the circuits 4, 5 are reset and the output of the signal VX is blocked for a prescribed time from application of power supply. |
