| 摘要 |
PURPOSE:To decide presence/absence of a body while eliminating errors, etc., due to variance of current parts, temperature, and humidity by driving and modulating a light emitting element, counting light emission pulses and photodetection pulses periodically to find the difference by digital processing. CONSTITUTION:An oscillating circuit 1 drives and modulates the light emitting element 8 of a light emitting circuit 2. The modulated light is photodetected by a photodetecting element 9, whose output is supplied to a digital deciding circuit 6 of a digital pulse number. The circuit 6-1 inputs signal pulses from the oscillating circuit 1 and counts the pulses simultaneously by counter circuits composed of flip-flop circuits. Then, a circuit 6-2 decides whether the number of received pulses is equal to the number of transmitted pulses or stays within a set permissible number range. The decided result is outputted from an output circiut 7 to inform presence/absence of a body. |
