| 摘要 |
<p>PURPOSE:To detect scanning speed information by measuring rising time when the output of a light receiving means to light-receive reflected light rises. CONSTITUTION:The faster scanning speed is, the steeper the rising of the output of a light receiving means 34 becomes since the beam diameter of beam light is approximately constant. Accordingly, time taken for the rising of the light receiving means 34 is in inverse proportion to the scanning speed. Time until it attains first threshold level TH1 (TH1>TH2) is timed by a timing means 37 after the output signal of a delaying means 35 to delay the output of the light receiving means 34 for fixed delay time is over second threshold level TH2 and the rising time of the light receiving means 34 is detected by it. Since the rising time is in the inverse proportion to the scanning speed, the output of the timing means can be used as scanning speed information. Thus, the scanning speed information can be detected.</p> |
