Patent ID: 7885167
Filing Date: 2011-02-08
Classification: G11B

Abstract:
1. An objective lens for an optical pickup apparatus recording or reproducing information by converging a light flux with a wavelength λ 1 in the range of 380 nm<λ 1 <420 nm emitted from a light source onto an information recording surface of an optical information recording medium, the objective lens comprising: a single lens including at least one aspheric surface, wherein the objective lens converges only the light flux with the wavelength λ wherein the objective lens satisfies the following expressions: where φ (mm) is an effective aperture at a light source side of the objective lens, d (mm) is a thickness on an optical axis of the objective lens, f (mm) is a focal length of the objective lens, NA is a numerical aperture at an image side of the objective lens, and n is a refractive index of the objective lens for the wavelength λ