| 摘要 |
PROBLEM TO BE SOLVED: To improve the rotation jitter of a rotation polygon mirror in a printing operation so as to prevent increase of a light emission time while shortening a first printing out time by controlling rotation by a second rotation controlling means when the rotation polygon mirror is waiting, and controlling rotation by a first rotation controlling means during a printing operation. SOLUTION: This apparatus is provided with a speed object origin changeover switch 8 of a rotation polygon mirror for scanning on a photosensitive member by a laser beam modulated by an image signal, and a target speed setting register 9. For detecting the speed of a scanner motor 3, a BD signal as a highly accurate control object origin to be used for printing, and an FG signal as a speed detection origin to be used at the time of preliminary rotation without the need of a high accuracy are switched optionally according to the state of the apparatus. That is, the rotation control is executed by the FG signal in the preliminary rotation for preliminarily rotating the rotation polygon member during waiting, and the rotation control is executed by the BD signal with a high accuracy during the printing operation. Therefore, there is no risk of the semiconductor laser deterioration due to increase of the light emission time. |
