OPTICAL PICKUP DEVICE OBJECTIVE LENS, OPTICAL PICKUP DEVICE, AND OPTICAL INFORMATION RECORDER/PLAYER DEVICE

摘要

Provided is an objective lens whereby the working of a casting which molds an objective lens is simplified and the moldability thereof is improved. The following formula is satisfied by designating ? (°) to be the maximum normal angle in the effective diameter of the light source-side optical surface of the objective lens: 66 = ? = 69.5 (1). The following formula is satisfied by designating S (h) to be the degree of sag with respect to a height (h) from the optical axis in the effective diameter of the light source-side optical surface of the objective lens (where the effective diameter is considered to be 1) when the second derivative S'' (h) has a maximum at h=h1: 0.85 = h1 = 1 (2). The following formulae are satisfied by designating Z (h) to be the degree of sag with respect to the height (h) from the optical axis in the effective diameter of the optical disc-side optical surface of the objective lens (where the effective diameter is considered to be 1) when the first derivative Z' (h) has a minimum at h=h2 and a maximum at h=h3: 0.25 = h2 = 0.4 (3), 0.8 = h3 = 0.9 (4)