| 摘要 |
<p>PURPOSE:To accurately detect an object even when infrared rays generated by any cause act as an external disturbance in an object detector using the infrared rays. CONSTITUTION:A microcomputer 22 makes a light-emitting element 6a emit light only for a definite time. A photodetector 6b receives reflected light reflected when radiated light from the light-emitting element 6a hits an object (a human being), and a light-receiving circuit 25 integrates and processes the detection signal of the photodetector 6b. As a result, a light-receiving signal R which is output from the light-receiving circuit 25 is continued to be output for a short while even after the light-emitting element 6a has finished light- emitting, and the time (the delay time) is set so as to be a prescribed time in a normal light-emitting and light-receiving operation. The microcomputer 22 judges that the object exists when the delay time is the prescribed time or lower, and it judges that the object does not exist when the delay time exceeds the prescribed time or when the light-receiving signal R is not output.</p> |
