Patent ID: 7508596
Filing Date: 2009-03-24
Classification: G11B

Abstract:
1. An objective lens included in an optical pickup device that records an information signal onto and/or reproduces an information signal from an optical recording medium, wherein the objective lens has a numerical aperture of 0.82 or higher and has a first surface and a second surface that are both aspherical, the objective lens focusing a light beam onto the optical recording medium, the first surface and the second surface having surface-to-surface eccentricity therebetween that causes an aberration, the aberration being correctable by tilting an optical axis of the objective lens relative to a central axis of the light beam incident on the objective lens, and wherein the aberration caused by the surface-to-surface eccentricity includes a third-order coma aberration, and wherein when the optical axis is tilted relative to the central axis of the incident light beam so that the third-order coma aberration becomes substantially 0 mλ rms, each of astigmatism, spherical aberration, and high-order coma aberration becomes 20 mλ rms or less.