OPTICAL LENS, METHOD FOR MANUFACTURING THE SAME, METHOD FOR MANUFACTURING OPTICAL LENS ARRAY, METHOD FOR PRODUCING FOCUS ERROR SIGNAL AND OPTICAL PICKUP DEVICE

摘要

PROBLEM TO BE SOLVED: To provide an optical lens and a method for manufacturing the lens having different focal distances on first and second planes perpendicular to each other, to provide an optical lens array, to provide a method for producing focus error signals and an optical pickup device which use the above lens. SOLUTION: The lens has a projecting part 20 having a convex curved face and functioning as an optical lens formed as integrated on a substrate 10 having a flat face. The projecting part 20 is formed in such a manner that the radius of curvature in a first cross section including the axis in the focus direction of the optical lens differs from the radius of curvature in a second cross section perpendicular to the first cross section with the axis in the focus direction as the crossing line, that the focal distance differs between on first plane and on the second plane perpendicular to each other, and that an almost oval or rectangular groove is formed along the boundary between the substrate 10 and the projecting part 20. The lens is used to produce focus error signals and to constitute the optical pickup device.