| 摘要 |
PROBLEM TO BE SOLVED: To easily take out and exchange worn parts by forming an aperture part at a position facing a polygon mirror, arranging a switch permitting the driving of a rotary body interlocking with the attachment and detachment of a cover covering the aperture part and detecting the wear of a thrust receiving member. SOLUTION: When a laser light beam is detected within a prescribed time after it is emitted from a semiconductor laser 121, it is judged that the laser light beam is normally reflected on the polygon mirror 1. However, when it is not detected by a detection control means 151, it is judged that the thrust receiving member of the mirror 1 is worn. Besides, the cover 142 for covering the aperture part is fitted and provided with a projection. When the cover 142 is fitted, the projection enters the switch and an actuator is actuated. By detaching the cover 142, the mirror 1 can be exchanged and cleaned. Thus, the using limit of the mirror 1 because of the wear of the thrust receiving member can be immediately detected and replacement of the worn parts of the mirror 1 is facilitated. |
