| 摘要 |
PURPOSE:To decide whether the detector is in a proper state or not every time a body is detected by inputting a signal from the detector to a comparator which decides whether the body is present or not and a comparator which detects whether the detector is in the normal state or not. CONSTITUTION:A light beam from a projector 2 is reflected by the body to be detected and then photodetected by a photodetector 3. The detection signal comparator 4 compares the detection signal with a reference level to decide whether the object body is present or not. The proper state comparator 5 compares the detection signal with a reference level and outputs a decision signal. A holding circuit 6 is reset with the output of the comparator 4 through a trigger generating circuit 7 and the current output of the comparator 5 is outputted to a latch circuit 8. When the output of the comparator 4 goes down to a low level and inputs its signal to the control input terminal CP of the latch circuit 8 through an NOT circuit 9, the latch circuit 8 outputs information of the holding circuit 6 to a driving circuit 10. Consequently, the detector 1 decides whether the detector 1 is in the proper state or not every the body is detected. |
