Patent ID: 6853470
Filing Date: 2005-02-08
Classification: G02B

Abstract:
1. A scanning optical system for emitting a plurality of beams scanning in a main scanning direction, comprising: a light source that emits the plurality of beams; a deflector that simultaneously deflects the plurality of beams incident thereon to scan in the main scanning direction, incident angles of the plurality of beams with respect to said deflector being different from each other in an auxiliary scanning direction which is perpendicular to the main scanning direction; and an imaging optical system that converges the plurality of beams deflected by said deflector to form a plurality of beam spots scanning on respective scan target surfaces in the main scanning direction, wherein said imaging optical system has: a first lens group though which all of the beams deflected by said deflector pass; and a plurality of second lens groups respectively provided for the plurality of beams, each of the plurality of beams emerged from said first lens passing through corresponding one of said plurality of second lens groups, wherein each of said plurality of second lens groups has a lens surface whose optical surface reference axis is tilted with respect to an optical surface reference axis of said first lens group so that a beam reflected by the lens surface is not incident on said deflector, wherein at least one of lens surfaces of each of said plurality of second lens groups except the lens surface tilted with respect to the optical surface reference axis of said first lens group is formed to be an aspherical, surface defined by a two-dimensional polynomial expression.