Patent ID: 6977782

Claim:
An objective lens unit manufacturing method for manufacturing an objective lens unit, with a numerical aperture not less than 0.7, made up by a plurality of lenses, by positioning a lens in a cylindrically-shaped lens holder of a synthetic resin material, using another lens, already mounted and secured to said lens holder, as a reference, and for securing said lens to said lens holder, for setting relative positions of said one and the other lens, said method comprising: causing a light beam to be incident on the respective lenses in said lens holder; reflecting said light beam, converged by said respective lenses, by a reflecting member; causing the light beam reflected by said reflecting member to be re-incident on said respective lenses to detect focusing error signals with respect to said reflecting member, based on a light beam transmitted through said respective lenses; and determining the amount of said spherical aberration in said light beam transmitted through said respective lenses, based on changes in said focusing error signals when said reflecting member is moved along the optical axes of said respective lenses, to adjust the distance between said respective lenses based on the amount of said spherical aberration.