| 摘要 |
PURPOSE:To reduce noise caused by air coming in and out from the window of the cover of a rotary polygon mirror. CONSTITUTION:The rotary polygon mirror 1 is covered with the cover 2. Besides, the cylindrical part 2a of the cover 2 is provided with the window 3 where a laser beam irradiating the reflecting surface 1b of the outside circumferential surface of the mirror 1 is passed through. The inside aperture end 3a of the window 3 opened on the inner surface side of the cylindrical part 2a is chamfered. Thus, the cross section of the window 3 is enlarged toward the inner surface of the cylindrical part 2a so as to prevent the large noise from being caused because the air passed through the window 3 is suddenly converged. |
