| 摘要 |
<p>PURPOSE:To positively detect a person arriving at a reception position. CONSTITUTION:Light pulses from light emitting elements 11 and 12 are projected at approximately 30 deg. toward the front alternately, reflected light is received by a photodetector 16 between the light emitting elements 11 and 12, the light reception output Is compared with a threshold by a comparator 24, and then signals equal to or above the threshold are output as pulses. The output of the comparator 24 corresponding to the reflection light of the light pulses of the light emitting elements 11 and 12 is separated and then one of separated output is delayed by the phase difference between both pulses and is supplied to an AND circuit 27. On the other hand, the other is directly supplied to the AND circuit 27. Output from the AND circuit 27 indicates that a person arrived at a monitoring position 13. A detection range R1 of the monitoring position 13 is approximately 1/5 of the case where one light emitting element is used, thus preventing the person near the monitoring position 13 from being detected by mistake.</p> |
