Patent ID: 6542278
Filing Date: 2003-04-01
Classification: G02B

Abstract:
A scanning optical apparatus comprising:a deflecting element for reflectively deflecting a beam emitted from light source means, into a main scanning direction; and an optical element for focusing the beam reflectively deflected by said deflecting element, on a surface to be scanned, wherein said optical element comprises two or more lenses, radii of curvatures in a sub-scanning direction of at least one lens surface of at least one lens out of said two or more lenses continuously change from on the axis toward off the axis in the main scanning direction, a rate of change of the curvatures in the sub-scanning direction within one beam on the lens surface is set to not more than 10%, and a shape of the at least one lens in the main scanning direction is determined so that F-numbers in the sub-scanning direction of the beam incident to the surface to be scanned are approximately constant in an effective scanning area, and wherein the at least one lens is disposed on a surface-to-be-scanned side with respect to a middle point between a deflection point on said deflecting element and the surface to be scanned.