| 摘要 |
PROBLEM TO BE SOLVED: To accurately control a scanner motor and to extend the service life of a photosensitive drum by a method wherein a rotation driving means is controlled in accordance with a beam detection signal in a first mode and it is controlled in accordance with a rotation speed signal in a second mode. SOLUTION: An emitted laser light is scanned in a horizontal direction in response to rotation of a polygon mirror 104 and a part of the light is detected by a beam detection section 4, thereby generating a beam detection signal (BD signal). An FG 3-3 transmits a speed detection signal (FG signal) while a scanner motor 3-2 rotates making one revolution. A switch 8 selects the BD signal or FG signal along an instruction of a CPU 1 to output it to a speed judgment circuit 5 and a speed error detection circuit 7. Therefore, the CPU 1 can drive and control the scanner motor 3-2 by the same speed even when either the BD signal or FG signal is selected. As a result, it is possible to control the scanner motor with high accuracy and to extend the service life of the photosensitive drum. |
