| 摘要 |
A device for generating an electric signal in response to movement of an object (1) past a predetermined point or within a predetermined area. At least three light sensitive elements (4, 5, 6) are placed side by side in the path of movement of the object (1) so that the object (1) moves past the elements (4, 5, 6) in sequence. A light source (2) is disposed for illuminating the light sensitive elements (4, 5, 6) directly or indirectly via a reflector (3). The light sensitive elements (4, 5, 6) are coupled to a signal processsing circuit, (12- 15) for evaluating the signals from the elements. The two outer light sensitive elements (4, 6) are coupled to respective differential amplifiers (12, 13), while the intermediate light sensitive element (5) is reference coupled to both of the differential amplifiers (12, 13).
|
