| 摘要 |
PURPOSE:To prevent generation of mis-detection by opening the 2nd gate circuit at a time zone where no light is irradiated from a light projection section and using an integration circuit to integrate a light signal during the zone thereby inhibiting the detection output when the output level reaches a prescribed value. CONSTITUTION:A light projection section 13 and a photodetector section 14 are provided to a photoelectric switch, a signal having a prescribed frequency from an oscillation circuit 11 is frequency-divided by a frequency division circuit 12, clocks a, b being at H level not at the same time, the light emitting section 13 is driven by a pulse of the clock (a) and irradiated to a detection region 24. The light signal from the region 24 is received by the light receiving section 14, amplified (15) into a prescribed level and fed to the 1st and 2nd gate circuits 16, 17. The circuit 17 is opened during the clock (b) when the light projection section 13 does not irradiate any light. Then the optical signal obtained during this period is integrated by an integration detection circuit 19 and a waveform shaping circuit 21, an inhibition signal is fed to an inhibition circuit 22 while regarding it as an external disturbance light so as to prevent mis-output of the detection signal from the region 24 through the circuit 16. |
