| 摘要 |
PURPOSE:To prevent the effective part of a mirror surface of a rotary polygonal mirror from deforming during work by providing a means which prevents the effective part of a mirror surface from deforming owing to an impact to plural mirror surfaces of the rotary polygonal mirror. CONSTITUTION:Two grooves 6d and 6e are provided over the entire circumference of the rotary polygonal mirror 6 near the upper end surface 6b and lower end surface of mirror surfaces 6a. The edges parts which have the highest probability of striking among edges in each mirror surface 6a are edgespart containing a point P' and that on the opposite side, and the next rank of the propability of strinking edges are for edges between mirror surfaces 6a and 6a. For this purpose, projection parts 6d and 6e are provided to the mirror surface 6a to prevent an accident greatly. |
