Patent ID: 7710847
Filing Date: 2010-05-04
Classification: G11B

Abstract:
1. An optical pickup apparatus comprising: a first light source for emitting a first light flux having a wavelength λ a second light source for emitting a second light flux having a wavelength λ a light converging optical system including a coupling lens and an objective lens, wherein the light converging system converges a light flux from the first light source onto an information recording surface of a first optical information recording medium through a protective layer having a thickness t wherein the first light source and the second light source are arranged so that a distance between the first light source and the coupling lens become optically equal to a distance between the second light source and the coupling lens, wherein a first diffraction structure is provided on an optical surface of the objective lens through which both the light flux of the wavelength λ wherein the following equation (1) is satisfied when d wherein the following equation (2) is satisfied by the chromatic aberration ΔfB of the composite system including the objective lens and coupling lens with respect to the light flux of the wavelength λ wherein a second diffraction structure is formed on an optical surface of the coupling lens through which both the light flux of the wavelength λ wherein the following equation (3) is satisfied when d where m f m n n