| 摘要 |
PROBLEM TO BE SOLVED: To provide a polygon mirror which can prevent degradation of the drawing quality caused by the deformation of a reflection plane, and which can moreover work each reflection plane easily. SOLUTION: The polygon mirror 10 has the shape of a hexagonal prism equipped with 6 faces of the reflection plane 11 on the periphery, and is rotated around a rotary shaft 12 serving as a central axis. In order to reduce the change of optical power by the deformation of the reflection plane 11 by the rotation of the polygon mirror 10, a diffraction structure 13 is formed at each reflection plane 11 of the polygon mirror 10. Since the deformation by the centrifugal force of the reflection plane 11 changes only the power of the vertical direction mainly to the rotary shaft 12, the diffraction structure 13 has the diffraction action only in the vertical direction to the rotary shaft in each reflection plane. |
