| 摘要 |
PURPOSE:To make continuous position detection without contacting by providing a radiation light source, a moving piece having an oblique side inclined in the moving direction, and two photodetectors at least. CONSTITUTION:A level comparator 5 supplies a current to a radiation light source 1. A moving piece 4 is so arranged that it shields a part of a photodetector 2, and an area S of the photodetector 2 is changed in accordance with movement of the moving piece 4. The output of the photodetector 2 is subjected to impedance conversion by a buffer amplifier 6 to output a position detection signal Vo. When the moving piece 4 is moved to the position indicated by a broken line, the boundary line is moved on the photodetector 2 by a length (l), and the quantity of light received on the area is reduced, and this reduction appears as a change of the output. When the angle of inclination of the moving piece 4 is denoted as theta, l=X.tantheta is true, and the output V0 of the photodetector 2 is given by V0proportional X.tantheta. Thus, a stable and continuous position signal is detected by the other potodetector while compensating the temperature characteristic and the secular change with one photodetector 2. |
