Scanning image formation optical system, optical scanner using the optical system, and image forming apparatus using the optical scanner

摘要

A scanning image formation optical system for use in an optical scanner for scanning a surface for one or more scanning lines. The optical scanner scans the surface by causing one or more coupled luminous fluxes from a light source to be incident on a deflecting reflective surface of a rotating optical deflector, which rotates around a rotary axis of the optical deflector and is parallel to the deflecting reflective surface. The luminous fluxes are deflected diagonally relative to a surface perpendicular to the rotary axis of the optical deflector, and the deflected luminous fluxes are converged toward the surface by the scanning image formation optical system so as to form an optical spot on the scanned surface. The scanning image forming optical system includes two or more special tilt surfaces, each formed such that a tilt amount of a sub-scanning cross-sectional configuration changes in a main scanning direction.