OPTICAL PICKUP-USE OBJECT LENS, OPTICAL PICKUP AND OPTICAL DISK UNIT

摘要

An optical pickup-use object lens (15) having a numerical aperture of at least 0.8, for correcting light, within a wavelength range of several nm based on up to 420 nm, for chromatic aberration at an image point on the optical axis. The object lens comprises, in an arranged order from a light source, a first lens group (GR1) having a compound plane (S2) of a refraction plane (S2r) and a diffraction plane (S2d), and a second lens group (GR2) having a positive refraction power, wherein the compound plane of the first lens group is formed by adding a diffraction plane having a positive refraction power onto an aspherical refraction plane having a negative refraction power, and a lens constituting the second lens group uses a single lens including at least one aspherical plane. This small object lens enables an effective chromatic aberration correction and a laser beam condensation up to a diffraction limit.