Patent ID: 7498550
Filing Date: 2009-03-03
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 at the time when 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 wherein the following equation (4) is satisfied when the light flux of the wavelength λ where m f m n n Δn represents the change amount of refractive index of the material constituting the coupling lens and the objective lens with respect to the light of wavelength λ ΔW represents the change amount of wavelength of the first light source for a change of ambient temperature.