OPTICAL PICKUP LENS AND OPTICAL PICKUP DEVICE

摘要

With regard to a plastic optical pickup lens having a numerical aperture (NA) of at least 0.84 and provided with annular zone steps to improve temperature characteristics, an optical pickup lens and an optical pickup device are provided with which appropriately-sized light spots can be formed at depth positions of three or more information recording surfaces without producing higher-order spherical aberrations to the greatest extent possible, even when the thickness of a disk has changed. The tangent angle ? (h), the tangent angle approximation f, and the normalized beam height h of the optical pickup lens satisfy the following conditional expression: -1 < tangent angle ? (h)- (tangent angle approximation f × normalized beam height h) < +1. However, the tangent angle ? (h) is the tangent angle (°) when the beam height is h, the tangent angle approximation f is the value of the angle (°) when h = 1 when each point of the tangent angle ? (h) has been obtained by linear approximation, and the normalized beam height h is the value obtained by normalizing the outermost circumference of the effective diameter of the lens to 1.