Patent ID: 7463568
Filing Date: 2008-12-09
Classification: G11B

Abstract:
1. An objective optical element for use in an optical pickup apparatus which is provided with a first light source of a wavelength λ 1 , a second light source of a wavelength λ 2 (λ 1 <λ 2 ) and a light converging optical system including a magnification changing element and the objective optical element, wherein the light converging optical system converges a light flux from the first light source onto an information recording plane of a first optical information recording medium through a protective substrate having a thickness t wherein the objective optical element has an optical magnification m wherein the objective optical element comprises on at least one surface: a common region through which the light flux having the first wavelength λ an exclusive region through which the light flux having the first wavelength λ wherein the exclusive region includes an exclusive diffractive structure having a function to suppress an increase of spherical aberration due to a raise of atmospheric temperature in accordance with a wavelength fluctuation of the light flux having the first wavelength λ wherein the light flux having the second wavelength λ wherein the optical magnifications m