| 摘要 |
PURPOSE:To take a measurement of distance in stable operation by increasing the quantity of light emission of a light emitting element monotonously from the small quantity of light to the large quantity of light without performing the logarithmic compression of the output of a photodetecting element nor the automatic gain adjustment of an amplifier. CONSTITUTION:When an oscillator operates to generate a clock pulses with a 62.5mus period, the output of a time forming circuit 2 is inverted to a level H for t=25ms, and a transistor (TR) 4 turns on and off repeatedly in response to the inversion. The output of an inverter 5 falls to L for a time of 25ms and a TR6 turns off to charge a capacitor 8 with a constant current, so that the output voltage of a buffer circuit 9 rises. Consequently, the collector current of a TR12 increases. Projection light generated by turning on a light emitting diode 13 is photodetected by SPDs 14 and 15, whose outputs are superposed upon a DC component as shown by (a). Outputs of BPFs 18 and 19 appear as shown by (b). A decision on measured distance is made from the difference from the outputs. Thus, the quantity of light emission of the light emitting element is increased monotonously from the small quantity to the large quantity to decide on a distance measurement state in stable operation. |
