| 摘要 |
PURPOSE:To realize a high density spot small in bending of image surfaces in both main- and sub-scanning directions and the variance of spot diameter and to satisfacto rily correct surface inclination by permitting a 2nd image forming optical system to connect the reflecting position and scanning surface of a rotating polygon mirror in the sub-scanning direction in almost a conjugate relation. CONSTITUTION:Luminous fluxes reflected by the rotating polygon mirror 3 are image- formed in a spot shape on the scanning surface 7, and scan said surface 7 at the same speed, as the rotating polygon mirror 3 rotates at the fixed speed in the direction of the arrow. The 2nd image forming optical system 8 has an ftheta function. Viewed from the deflecting surface, the lens system consisting of lenses 81 and 82 connects infinity on the side of a light source 1 and the position of the scanning surface 7 in a conjugate relation. On the other hand, viewed from the surface orthogonally intersecting the deflecting surface, said lens system connects the reflecting position of the rotating polygon mirror 3 and the scanning surface 7 in almost a conjugate relation. Thus, surface inclination can be corrected satisfactorily, and the bending of image surfaces can be corrected in the main- and sub-scanning directions, thereby accomplishing the diameters of high density spots. |
