| 摘要 |
<p>PURPOSE:To identify the presence or absence of the intrusion of an object by detecting the intensity of the reflected light from a monitoring section intermittently at prescribed sampling intervals and successively and relatively comparing the data on the intensities of a pair of the reflected light rays. CONSTITUTION:A photodetector 7 successively detects the modulating intermittent reflected light rays reflected from a background surface or object surface and intermittently outputs the modulating detection currents having the amplitudes corresponding to the light intensities thereof. An amplifier section 10 detects and amplifies the modulating detection currents and outputs an AD detection signal AC. A smoothing section rectifies and smoothes this signal and outputs a DC detection signal DC. A converting section 12 converts the crest components of the signal DC successively to the corresponding sampling data DATA in synchronization with the sampling signal CTL outputted by a control arithmetic section 14. A memory section 13 alternately records the data DATA and updates the recording data at every inputting. The arithmetic section 14 reads out the updated data DATA recorded in a pair of memory regions M 1, M 2 and computes the relative ratio. The signal indicating the intrusion of the object is outputted when the relative ratio exceeds the set threshold.</p> |
