Patent ID: 6222662
Filing Date: 2001-04-24
Classification: G02B,Y10S

Abstract:
An image forming apparatus, comprising:a light source for emitting a beam;a beam deflector for deflecting the beam from said light source; andan optical scanning lens for converging the deflected beam to a beam spot on a surface to be scanned so as to scan said surface to be scanned at a uniform velocity,wherein said optical scanning lens comprises a biconvex single lens, andsaid biconvex single lens comprises a first lens surface and a second lens surface as counted from a beam deflector side, said first and second lens surfaces having a nonarcuate shape in a deflection plane determined by:X=Y.sup.2 /[R+R{1+L -(1+L +K)(Y/R).sup.2 +L }]+A.multidot.Y.sup.4 +B.multidot.Y.sup.6 +C.multidot.Y.sup.8 +D.multidot.Y.sup.10 +where X represents a coordinate in an optical axis direction, Y represents a coordinate in a direction perpendicular to the optical axis direction, R represents a paraxial axis curvature radius, K represents a cone constant, A, B, C, D, . . . represent high order coefficients, respectively, R, K, A, B, C, D, . . . being given for specifying said nonarcuate shape; andW, d.sub.1 and L satisfy the following relations:W/L.ltoreq.0.9 and10<(W/L).sup.2.multidot.(L/d.sub.1)<30,where W represents an effective main scanning width, d.sub.1 represents a thickness of said lens and L represents a distance from a deflection start point of said beam deflector to a surface to be scanned, andsaid lens converging a deflected beam, deflected at uniform angular velocity by a beam deflector, onto said surface to be scanned so as to scan said surface to be scanned at a uniform velocity.