Scanning optical system

Abstract

Disclosed is a scanning optical system that includes a semiconductor laser; a polygon mirror that deflects and scans a light beam emitted from the laser; and an imaging optical system that forms a beam spot on a photoconductive drum. The imaging optical system consists of a curved surface mirror having a positive power mainly in the main scanning direction and an anamorphic lens having a positive power mainly in the auxiliary scanning direction. The anamorphic lens having an anamorphic surface whose optical axis is decentered from a reference ray that reaches the center of the scanning range. The sectional shape of the anamorphic surface in an auxiliary scanning direction being a non-circular curved line to correct coma in the auxiliary scanning direction. The anamorphic surface is a rotationally asymmetrical surface that is defined by a two dimensional polynomial expression.

Dependencies are inferred from the claim text.