| 摘要 |
PURPOSE:To detect the presence of an object in a light path, by emitting light subjected to pulse modulation from a light emitting element and receiving said light by a light receiving element. CONSTITUTION:A timing generating circuit 1, a light emitting element driving circuit 2, a light emitting element 3, a light receiving element 4, a signal processing circuit 7 and an output circuit 8 etc. are provided. The circuit 7 is synchronous to the light emitting element driving pulse of the circuit 1 and has detection points different in timing. When an object S is interposed between the elements 3, 4, pulse light is blocked. That is, the circuit 7 is one utilizing the setting/resetting function of a shift register and a delay processing signal relating to 'presence' and 'absence' of the matter is directly obtained from the serial output OUT of the shift register and, therefore, circuit constitution can be simplified. By this method, erroneous operation can be prevented and detection sensitivity can be also enhanced. |
