| 摘要 |
<p>PURPOSE:To detect invasion of a human body being stand still and an object except the human body by projecting a light beam to a slit, and detecting the invasion of the human body, etc., to a detecting area by the change of the light current of a photodetector. CONSTITUTION:A projecting means projects a light beam in the shape of two slits to a prescribed reference object 3. The flux of reflected light of the light beam is covered with a light receiving lens 4 to two-slits-shaped spots. T detecting means to have three respective independently light receiving parts, a photodetector 5 at the converging position of the two slit-shaped spots so that light currents IA, IB and IC can be respectively obtained from respective light receiving parts is provided, and a detecting means to detect an object 6 to be detected invades to the front surface side of the object 3 based on the change of light currents IA to IC is provided. When the element 5 light- receives the flux of reflected light from the object 3, light currents IA and I2 are positioned so as to come to IA=IB and the detecting means decides that when the light currents IA and IC comes to IA>IB and IC-IA are changed and the object 6 invades.</p> |
