| 摘要 |
PURPOSE: To reduce noise and power consumption and to effectively use a mirror face of a rotary polygon mirror. CONSTITUTION: When an angle between a connection surface 24 being on the side opposite to a light source 12 for an optical axis of an image forming optical system 16 when a mirror face 22 is faced perpendicularly to the optical axis of the image forming optical system 16 and the mirror face 22 faced perpendicularly to the optical axis of the image forming optical system 16 is defined asβ, and the angle between the connection surface 24 being on the light source 12 side for the optical axis of the image forming system 16 and the mirror face 22 faced perpendicularly to the optical axis of the image forming optical system 16 is defined asγ, the angleγis made different from the angleβ. Since a projecting part is reduced, and its weight is lightened, the noise when the rotary polygon mirror 14 is rotated is reduced, and the power consumption of a driving motor is reduced. Further, the use range of the mirror face 22 is biased by providing a light beam detector 18 on the outside of an image forming surface 20, but the mirror face 22 is biased by the slope of the connection surface 24 also, thus the mirror face 22 is used effectively. |
