TRI-METROGON SCANNING TYPE DISTANCE MEASURING DEVICE AND METHOD FOR MEASURING DISTANCE

PROBLEM TO BE SOLVED: To reduce a measuring error of a distance caused by a secondary reflection on an object in scanning a light beam. SOLUTION: A floodlamp 1 scans a light beam in one plane. The light beam scanned is partly branched by means of a beam splitter 15 and a position of the light beam branched is detected by means of a scan sensor 16. A pair of position sensors 21a, 21b composed of PSD is disposed with a plane scanning the light beam as a symmetrical plane, and both position sensors 21a, 21b are commonly connected at each terminal in which increase and reduction of a signal value are coincident with each other according to a distance to the object 7. Therefore, even if a luminescent spot due to a secondary reflection is generated on the object 7 in a transverse direction to the symmetrical plane between both position sensors 21a, 12b, an error component resulting from the secondary reflection is removed from an output synthesized from the position sensors 21a, 21b and the distance to the object 7 can be accurately measured.