| 摘要 |
PURPOSE:To detect exactly a range to a target object even in a fog, a snow, etc. by providing a sensitivity variable means which sets the receiving sensitivity of a reflected light signal to a low sensitivity at a prescribed level when light sending an optical signal increasing thereafter as time elapses. CONSTITUTION:A light sending device G emits pulse light Lt from a laser diode 12 in response to the supply of the transmitting trigger signal St of a period Tp from a control circuit F. On the other hand, a light receiving device H condenses the incident light containing reflected pulse light Lr. A photodetecting output making the reflected light Lr incident to a photodetector 17 is amplified by a pre-amplifier 18 to obtain the photodetecting signal Sr of an analog pulse and is inputted to the control circuit F. The control circuit F is constituted of a clock circuit 20, a time variable attenuating circuit 21, a wide band amplifier 22 and a signal processing circuit 23, and basing on a delay time extending from the time point of arrival of a trigger pulse Sd from the clock circuit 20 to the arrival time point of a photodetecting pulse Se, a range data DR corresponding to a range to a target object is formed by the processing circuit 23 and outputted. |
