Patent ID: 7580601

Claim:
A beam focusing lens having an optical axis for focusing at a point of focus a light beam having different angles of divergence in orthogonal directions perpendicular to the optical axis, wherein the beam focusing lens consists of: a first lens component having positive refractive power; a second lens component having positive refractive power; at least one surface of at least one of said first lens component and said second lens component is an anamorphic aspherical surface; and the shape of the anamorphic aspherical surface satisfies the following condition: Z =( Cx·X 2 +Cy·Y 2 )/(1+{1−( Kx·Cx 2 ·X 2 +Ky·Cy 2 ·Y 2 )} 1/2 ) +Σ A i {(1 −B i ) X 2 +(1 +B i ) Y 2 } i where X is the distance (in mm) from the optical axis in a first direction of a point on the anamorphic aspherical surface, Y is the distance (in mm) from the optical axis in a second direction that is orthogonal to the first direction of the point on the anamorphic aspherical surface, Z is the length (in mm) of a line drawn from the point on the anamorphic aspherical surface at the coordinate distances X and Y from the optical axis to the tangential plane of the anamorphic aspherical surface vertex, Cx is the curvature (=1/the radius of curvature, R in mm) in the first direction of the anamorphic aspherical surface on the optical axis, Cy is the curvature (=1/the radius of curvature, R in mm) in the second direction of the anamorphic aspherical surface on the optical axis, Kx is the eccentricity in the first direction, Ky is the eccentricity in the second direction, A i is the ith first aspherical coefficient, B i is the ith second aspherical coefficient, and the summation extends over i.