| 摘要 |
PURPOSE:To make an optical deflecting device small-sized by detecting the rotative velocity of a motor with laser light reflected on a rotary polygonal mirror. CONSTITUTION:Laser light 12 emitted from a semiconductor laser oscillator 11 is converged by a collimator lens 51 and is made incident on a rotary polygonal mirror 14. Laser light 16 reflected on the surface of the mirror scans a photosensitive drum 15 after its distortion on the scanning plane is compensated by an ftheta lens 52. A photodetector 53 which detects the laser light 16 at a prescribed deflection angle is arranged before a scan start position P1, and the photodetector 53 outputs one detection pulse for one raster when detecting the laser light 16. The rotation number of the rotary polygonal mirror 14 is controlled in accordance with the number of detection pulses per unit time. |
