| 摘要 |
PURPOSE:To reduce a scanning error and to facilitate manufacturing by composing a cylindrical basic structure of a thin reflecting part and reducing factors of dynamic variation due to air resistance during high-speed rotation. CONSTITUTION:A rotary polygonal mirror 23 consists of the basic structure 23a having a cylindrical outward appearance, a polygonal mirror part 23b, and a conic part 23c which connects them together. The basic structure 23a and conic part 23c apply an rotary inertial force to the polygonal mirror which rotates at a high speed, so dynamic variation during rotation is suppressed and the strength and precision of the polygonal mirror are maintained. Further, this part is symmetrical about the center of a rotating shaft, so dynamic unbalance is reduced. The reflecting part 23b having a reflecting surface, on the other hand, is constituted to extremely small size in the direction of the rotating shaft for the basic structure 23a, so the air resistance during the rotation is reduced and the dynamic balance is reduced. |
