Patent ID: 7417938
Filing Date: 2008-08-26
Classification: G11B

Abstract:
1. An optical pickup apparatus, comprising: a light source; a collimator lens for converting light emitted from the light source into a substantially parallel light flux, the collimator lens including two lens groups; an objective lens for condensing the parallel light flux to a recording surface of an optical recording medium including a transparent substrate; and a drive mechanism capable of changing an interval between the two lens groups to correct spherical aberration caused by a change in thickness of the transparent substrate, wherein a first lens group of the collimator lens has a negative power and a second lens group thereof has a positive power, wherein the second lens group having the positive power comprises a negative power lens and a positive power lens, wherein the negative power lens is made of a glass material having relatively high dispersion, and the positive power lens is made of a glass material having relatively low dispersion, wherein the first lens group has a negative power of a focus distance of −10.3 mm and exists at the light source side, wherein the second lens group has a positive power of a focus distance of 7.0 mm and exists at the objective lens side, and wherein the first lens group is fixed, and the second lens group is movable, the moving distance of which, per micrometer of thickness error of the transparent substrate, is 20 micrometers.