| 摘要 |
PURPOSE:To eliminate a drawback due to the performance of a light reception element and heighten the accuracy of distance measurement, by enabling the detection through the single light reception element of the quantities of reflected light based on two light fluxes emitted at a prescribed distance from each other. CONSTITUTION:Light sources A1, A2 are alternately lighted on and off according to a prescribed chart. Light fluxes having passed through the slits B1, B2 of a projection mask B are condensed by a projection lens C to form a sign image on an object D. The light fluxes reflected by the object are scanned by a scanning mirror F to form an image on a detection mask H through a light reception lens G. When the set angle of the mirror F is optimal, the projected images B1', B2' of the slits B1, B2 equally cover detection slits H1, H2. For this reason, the quantity of incident light to a photoelectric converter I does not change even if the light sources A1, A2 are alternately lighted on and off. As a result, a distance can be measured by rotating the mirror F until the output signal of the converter I becomes a DC signal. The quantity of the rotation of the mirror corresponds to the distance. |
