US Patent 7193759 Scanning optical system

There is provided a scanning optical system, which is provided with a light source that emits at least one beam, a polygonal mirror, and an imaging optical system that converges the at least one beam deflected by the polygonal mirror to form at least one beam spot on a surface to be scanned. The at least one beam incident on the polygonal mirror is inclined in an auxiliary scanning direction which is perpendicular to the main scanning direction. Further, at least one lens surface of the imaging optical system is configured such that a beam reflected therefrom proceeds toward an outside region of the polygonal mirror.