| 摘要 |
PROBLEM TO BE SOLVED: To reduce the windage due to rotation of a polygon mirror as much as possible. SOLUTION: First and second disks 41 and 44 which have the center of rotation of a polygon mirror 39 as centers of rotation and have diameters larger than the diameter of a circumscribed circle of the polygon mirror 39 are provided in both end face parts in the axial direction of the polygon mirror 39 so that they are rotated as one body together with the polygon mirror 39. Peripheral air is blown outward by the centrifugal force in accordance with rotation of first and second disks 41 and 44, and as the result, the air pressure around the polygon mirror 9 is reduced to reduce the air resistance due to turbulence which is brought about by collision between the outer peripheral part of the polygon mirror 39 and peripheral air. |
