| 摘要 |
PURPOSE:To measure distance effectively with high accuracy by sampling and holding the output of a photodetecting element for monitoring when reference light is inputted to a photodetecting element for distance measurement, feeding its output back, and measuring the distance while controlling the quantity of light emission of a light source. CONSTITUTION:When the reference light is inputted to the photodetecting element for distance measurement, sampling pulses are applied to a sample circuit 5 and the output of a photodiode 2 for monitoring which is amplified by an amplifier 3 and a differential amplifier 4 is sampled and held. A transistor (TR) 11 has an impedance value corresponding to the output of the diode 2. The bias point of a laser diode 1 is fixed at a certain value when the reference light is inputted to the photodetecting element for distance measurement and when reflected light is inputted to the photodetecting element for distance measurement. Then, phase variation is removed from the phase difference corresponding to the distance to a target. Consequently, the distance is measured effectively with high accuracy.
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