| 摘要 |
PURPOSE:To measure accurately the depth of snow and to improve S/N by controlling the quantity of light incident on a light detector so that it is always constant, and by using a spectrum diffusion system for the modulation of a light source. CONSTITUTION:A light source 11 projects beam-shaped lights on a plane 10 to be measured. A light detector 14 receives the beam-shaped lights projected from the light source 11 and reflected from the plane 10, and delivers two output signals corresponding to the positions of reception on the light receiving plane. An adder 18 operates the sum of the two output signals of the detector 14 and delivers a sum signal. A subtractor 17 operates the difference between the two output signals of the detector 14 and delivers a difference signal. A comparator 26 compares the sum signal with a reference value and delivers an output signal in accordance with a compared value. Based on the output signal from the comparator 26, a light source driver 28 drives the light source 11 in such a manner that it controls the brightness of the light source 11 so that the quantity of lights received by the detector 14 is always constant. |
