| 摘要 |
PROBLEM TO BE SOLVED: To provide a polygon mirror constituted so that the flatness of a mirror surface is prevented from being deteriorated because of the centrifugal force of the polygon mirror produced when it is rotated at a high speed. SOLUTION: This polygon mirror 1 is rotated with a rotary shaft 3 as a center. Then, a holding member 21 holding the mirror surface 2 of the mirror 1 is constituted of a plane surface passed near the central part of the mirror 1 in a longitudinal direction of the mirror surface and including the shaft 3 and a holding member 12 is constituted of the plane surface passed more outside than the central part in the longitudinal direction of the mirror surface and including the shaft 3. By forming the cross section of the holding member 21 in a direction being in parallel with the shaft 3 thick and forming the cross section of the holding member 12 to be gradually thin only in the direction being in parallel with the shaft 3, the centrifugal force acting on the mirror surface 2 is made constant. |
