Patent ID: 6154245
Filing Date: 2000-11-28
Classification: B41J,G02B

Abstract:
An optical element comprising:a resinous optical element having optical surfaces longitudinal in a main scanning direction and comprising two optical surfaces, each having an image effective portion and an image ineffective portion,wherein the shape in the main scanning direction of the image ineffective portion of at least one optical surface is represented by the sum of a function representing a shape in the main scanning direction of the image effective portion and a spline function,wherein when the X-axis is defined along the optical-axis direction of the optical element and the Y-axis is defined along an axis perpendicular to the optical axis in the main scanning plane, the spline function is expressed by the following polynomial:X=S.sub.0 +.SIGMA.S.sub.m H.sup.mwhere H=Y-H.sub.0, H.sub.0 is a nodal point of the spline function, Sm is a spline coefficient, m is a positive integer, S.sub.0 is a spline coefficient, and Y is a value along the Y-axis, andwherein thicknesses in the optical-axis direction of the image ineffective portions are determined by the spline function.