| 摘要 |
PURPOSE:To attain the response in the unit of microseconds and to miniaturize the circuit by setting a prescribed time by a counter and discriminating a signal incident before the set time elapses after a light reception signal is incident as a noise signal. CONSTITUTION:A pulse modulation light projected by a lighting means A is received by a photodetection means B to generate photodetection signals 1, 1'... the signals 1, 1'... are signals with a prescribed period and a photodetection signal 2 is a noise signal. When the photodetection signal 1 is inputted to a count means C, the state so far is reset and a pulse signal 3 is outputted after a preset time elapses. When the next photodetection signal 1' is inputted while the pulse signal 3 is outputted, a discrimination means D discriminates a signal as the signal incident at a prescribed period and gives an output signal 4 to a signal processing means E. When the noise signal 2 is inputted to the count means C before a prescribed time elapses after the incidence of the photodetection signal 1, the count means C resets the state so far the same as the processing of the photodetection signal 1.
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