| 摘要 |
PURPOSE:To enable distance to be accurately detected despite inclusion of pulsating current in external light by detecting the point where the change rate of the pulsating components contained in external light is smallest and projecting pulse light to the measuring object at this time and receiving the same with photo detectors. CONSTITUTION:A photo detector 15 which detects the change rate of external light is provided besides photo detectors 11 thru 14 which are so arrayed as to be able to respectively receive the pulse light reflected by the measuring object according to the distance of the measuring object. In case pulsating components by fluorescent lamps, etc. are contained in the external light, a circuit 22 inputs a pulse signal to the input terminal of an AND circuit 23 near the point where the change rate of the external light becomes minimum, and this causes a light emitting element 20 to emit pulse light, which light is reflected by the measuring object and is received in the photo detectors 11 thru 14. |
