| 摘要 |
PURPOSE:To fix the light output on a photosensitive drum to prevent the variation of the spot diameter by controlling the power of the laser light to a prescribed output in accordance with the scanning position of a scan face. CONSTITUTION:The beam is repeatedly scanned in the direction of an arrow C in accordance with rotation of a rotating polygonal mirror. A photodetector 7 is arranged in the vicinity of the scanning start point, and the passage time of the scanning beam is detected by this photodetector, and light beam scanning and an image signal 1 are synchronized with each other by a detection signal 9. This detection signal 9 is inputted to a pattern generating circuit 2, and this circuit 2 generates a pattern of a control signal indicating a preliminarily set laser intensity, and this signal is inputted to a laser output circuit 3, and the laser output control circuit 3 controls the output level of a semiconductor laser in accordance with inputted intensity signal and image signal. Thus, an effective spot diameter having an approximately fixed size is obtained on the photosensitive drum at all field angles. |
