| 摘要 |
PURPOSE:To prevent erroneous distance measurement, by adding a differentiation circuit to an output terminal of a photoelectric conversion element so as to always keep the back scattering light power from exceeding the received light power. CONSTITUTION:A differentiation circuit 13 is added to an output terminal of a photoelectric conversion element 4, in a distance measuring apparatus which comprises the photoelectric conversion element 4 for detecting reflected light of a pulse laser light 2 from a target object after irradiated from a pulse laser unit 1, a variable gain amplifier 5 for amplifying the electrical signal photoelectrically converted and a counter 9 for determining the distance to the target from the propagation delay time of the pulse laser light 2 and the like. The differentiation circuit 13 whose the output voltage or current is proportional to the frequency and has such a high-pass filter that allow the passage of the input with a smaller pulse width but does not of that with a broader width by damping. Here, it is a signal light as reflected light from a target and a back scattering light that are received and converted into electricity with the element 4. Since the signal light is smaller in the pulse width than the back scattering light, the differentiation circuit 13 which selects and outputs only the pulse of the signal light utilizing this is provided to pick up the signal light. |
