| 摘要 |
PROBLEM TO BE SOLVED: To reduce manufacturing cost per one polygon mirror mechanism, to obtain high yield, to suppress the plane tilt of a polygon mirror and to prevent the quality of an image formed at a recording medium from being lowered. SOLUTION: The image is exposed and formed by irradiating the recording medium 1 with a laser beam emitted from a laser light beam through the polygon mirror mechanism 31 and scanning the medium 1. Then, a positioning part 7 with respect to an opposite party and a part to be positioned 6 are separately formed at the coupling part 5 of a supporting frame 3 with respect to a polygon mirror rotation driving part M and the part to be coupled 4 of the driving part M with respect to the coupling part 5 of the frame 3. Besides, a part to be coupled and a part to be positioned are formed at the rotation driving part of a polygon mirror mechanism being different from the mirror mechanism 31. Thus, the different polygon mirror mechanism can be coupled to the coupling part of the frame 3 so that it can be exchanged for the polygon mirror mechanism of the coupling part side. |
