| 摘要 |
PROBLEM TO BE SOLVED: To suppress the suction of air into a housing space in nearly a hermetic state in which a rotary polyhedral mirror is housed at the time of rotational driving of this rotary polyhedral mirror and to suppress the adhesion of the dust sucked together with the air on the opposite surface, etc., of the rotary polyhedral mirror. SOLUTION: The housing space 4 is internally provided with an inflow regulating member 16 covering the joint part between a housing case 1 and cap cover 2 near the rotary polyhedral mirror 9. The point where the end of the inflow regulating member 16 faces the inner peripheral surface of the housing space 4, i.e., the point where the microspacing of the joint part between the housing case 1 and the cap cover 2 is communicated with the inside of the housing space 4, is located in a region where the suction force generated by the flow of the air occurring in the housing space 4 accompanying the rotation of the rotary polyhedral mirror 9 is small. Then, the suction of the air from the microspacing of the joint part between the housing case 1 and the cap cover 2 into the housing space 4 at the time of rotational driving of the rotary polyhedral mirror 9 is suppressed. |
