Patent ID: 6717705
Filing Date: 2004-04-06
Classification: G02B

Abstract:
A scanning optical system for emitting at least one beam scanning in a main scanning direction, comprising:a light source that emits at least one beam; an anamorphic optical element that converges the at least one beam emitted by said light source in an auxiliary scanning direction which is perpendicular to the main scanning direction; a polygonal mirror that rotates and deflects the at least one beam emerged from said anamorphic optical element to scan in the main scanning direction within a predetermined angular range; and an imaging optical system that converges the at least one beam deflected by said polygonal mirror to form at least one beam spot on a surface to be scanned, said at least one beam spot scanning in the main scanning direction on the surface to be scanned, wherein said imaging optical system has: a scanning lens; and at least one compensation lens provided on the surface side with respect to said scanning lens, said at least one compensation lens compensating for curvature of field, wherein one surface of said scanning lens has an anamorphic aspherical surface, said anamorphic aspherical surface being defined as a surface whose curvature in the auxiliary scanning direction at a point spaced from an optical axis thereof in the main scanning direction is determined independently from a cross-sectional shape thereof along the main scanning direction, wherein one surface of said at least one compensation lens has an aspherical surface, said aspherical surface being defined as a surface in which a tilt angle of a cross-sectional shape in the auxiliary scanning direction changes with a position in the main scanning direction, said aspherical surface being asymmetrical with respect to a plane perpendicular to the auxiliary scanning direction and including a central point thereof.