| 摘要 |
PURPOSE:To process light amount adjustment before writing an image and to prevent the forcible scanning of laser light to an image formation area by detecting the specified rotation position of a polygon mirror surface and performing laser light emission obtaining a horizontal synchronous signal in a non-image formation part. CONSTITUTION:A light emitting diode 4 for detecting a rotation position exposes reflection materials 2a-2f in response to a non-image information area of a photosensitive drum 57 and a phototransistor 5 receives light. While the transistor 5 is electrically conducted, a position detection circuit 3 sequentially outputs a light emitting signal BDR. A light amount automatic adjustment circuit 63 variably adjusts a driving electric current impressed on a laser driving circuit 52 based on the signal BDR so that a light amount level outputted from a photodiode 64 becomes a regulated level. A laser beam LB for polarizing scanning is emitted from a laser 51 based on the signal BDR. When a photodiode 58 detects the laser beam LB through a detecting mirror 55, the horizontal synchronous signal BD deciding writing timing in a main scanning direction is outputted from a horizontal synchronous signal generation circuit 59. |
