PURPOSE: To prevent erroneous operation even with respect to an object to be detected comprising a mirror surface body, by providing light quantity control means for controlling an output circuit by discriminating whether the object to be detected comprising the mirror surface body is present or not in a detection area on the basis of the light quantity level of reflected light.
CONSTITUTION: Laser beam is emitted to an object to be detected and reflected beam is detected by the beam receiving elements 20a, 20b of a position detecting means arranged to the beam collecting surface of a receiving optical system. The detected output is inputted to a distance measuring control means 5 and an output circuit is operated through a signal processing circuit 25. A beam quantity control means 7 is connected to the means 5 and compares the output of the amplifier G2 of the beam receiving circuit 21a of the means 5 and reference voltage divided by a resistor R5 and a detection area setting variable resistor VR2 to discriminate whether a nomally operale beam receiving signal is obtained or not and freely inhibit the input to the circuit 25 through an OR circuit. By this method, it can be discriminated whether the object to be detected comprising a mirror surface body is present or not in the detection area without erroneous operation.
OKUDA YOSHIHIKO
YORIFUJI ARITAKA
IGARI MOTOO
MIYASHITA HITOSHI
