| 摘要 |
<p>PROBLEM TO BE SOLVED: To heighten resolution, and enable detection with high accuracy by making plural light emitting elements emit the light by pulses in mutually different periods with respective elements, and almost overalapping respective scanning areas with each other. SOLUTION: Scanning areas Aa and Ab of respective light beams reflected by a rotary polygon mirror and a reflecting mirror, have a scanning width W on a road R, and exist slightly in front and in rear by a distance B, but are put in an almost overlapped condition. Therefore, even if both a pulse light mission period of the respective light beams and a scanning period necessary for a single scan are the same as usual, since a phase of pulse light emission is shifted, mutual interference of reflected light beams can be prevented. Even if a pulse light emission period of respective light emitting elements of a light projecting part 2 is not shortened, width directional resolutionΔW is substantially doubled. Therefore, from a relational expression, rotating speed of the rotary polygon mirror is set high in a range where the width directional resolutionΔW can be sufficiently secured, and when a scanning period of a light beam is shortened, lengthwise directional resolutionΔL can be heightened at the same time. Therefore, detection can be performed with higher accuracy than usual.</p> |
