| 摘要 |
PURPOSE:To prevent malfunction due to a slight change in light quantity in a light-receiving element, by changing the driving time of a display lamp for displaying the signal level according to the size of the quantity of light received by the light-receiving element. CONSTITUTION:The pulse-modulated light from a light-projecting means 1 is supplied through a light-receiving element 2 and an amplifying circuit 3 to both a control circuit 4 and a display level discriminating circuit 11. In the circuit 4, discrimination is performed with a given discrimination level l1, and after signal processing at 6, the drive of a load 8 is controlled through an output circuit 7. Moreover, a display lamp 9 displays the operating condition of the load 8. On the other hand, in the circuit 11, when the input voltage exceeds a discrimination level l2 to the negative side, an LED 13 is turned on only during the period W, and as the quantity of received light increases, the light-emitting period W is increased. Accordingly, when the optical axes of the light-projecting means 1 and the light-receiving element 2 respectively coincide with each other, the luminance of the LED 13 becomes maximum, and the regulation of the optical axes is completed. |
