| 摘要 |
PURPOSE:To surely prevent malfunction due to mutual interference in using plural photoelectric switches by integrating a photodetection signal with a signal synchronously with a projection period while the projection period of a pulse beam from a light emitting element is varied. CONSTITUTION:A programmable frequency divider 3 provided to a projection circuit 1 frequency-divides a reference pulse of a reference period fed from an oscillation circuit 2 in response to the frequency division ratio set externally and supplies its output to a driving circuit 4. The circuit 4 lights a light emitting element 5 in a pulse current synchronously with a pulse signal from the frequency divider 3. A photodetection circuit 6 uses an integration circuit 11 to count an output of a comparator circuit 9 outputting a high level when a signal amplifying a signal from a photodetector 7 opposite to the element 5 having a passing region of an object to be detected in between exceeds a reference level only at the synchronizing state with a signal from the frequency divider 3.
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