| 摘要 |
PURPOSE:To obtain a characteristic having a good signal to noise ratio S/N with a low voltage power source by operating linearly amplifiers irrespectively of the distance and reflectivity of a target object (subject). CONSTITUTION:If the distance from a target object (subject) 3 which is an object to be measured is a middle distance and the reflectivity of the subject is about ''middle'', that is, if the quantity of incident light is about ''middle'', the output of a level decision circuit 12 attains a high level ''H'' so as to output a signal at a distance measuring timing t1 where the voltage value VD set by the output level decision circuit 12 of a gain variable amplifier 9b is attained. Said output is fed to a waveform processing circuit 11 which creates distance measuring information. Namely, the quantity of incident light is amplified linearly to the voltage value VD of the adequate level at which the dynamic range of the circuit can be fully assured, by the gain variable amplifiers 9a, 9b. The signal for the distance measuring timing is thus read. |
