| 摘要 |
PURPOSE:To obtain a stable distance detector by removing defects caused by the characteristics of transistors in first and second detecting circuits which logarithmically convert only the varying part of the current output of a semiconductor optical position detector due to pulsed light. CONSTITUTION:The current output IL1 of the semiconductor optical position detector 5 is logarithmically converted through a logarithmically compressing transistor Tr1 in a logatithm conversion part LA1 comprising the transistor Tr1 and an operation amplifier OA1. The same current as the current IL1 is flowed from a power source + Vcc through a FET (FT1) and expanded by an expanding transistor Tr3. When the pulsed light is emitted, a switch SW2 is opened, SW3 is closed, the current variation DELTAIL1 is supplied to the Tr3 from the operation amplifier OA5, and an output VO1 is obtained. Likewise, an output VO2 is obtained from a second detector. Both outputs are inputted to an operation amplifier, and the current ratio corresponding to the distance is obtained from the difference in the output and inputted to a sample and hold circuit SH as a voltage. Therefore the stable distance detector can be obtained. |
