Patent ID: 7664003
Filing Date: 2010-02-16
Classification: G11B

Abstract:
1. An objective lens for use in an optical pickup apparatus for recording and/or reproducing information on a first optical information recording medium having a protective substrate with a thickness t 1 using a light flux with a wavelength λ 1 , for recording and/or reproducing information on a second optical information recording medium having a protective substrate with a thickness t for recording and/or reproducing information on a third optical information recording medium having a protective substrate with a thickness t an optical surface including a central area and a peripheral area arranged at an outside of the central area, wherein the central area transmits a light flux with the wavelength λ the peripheral area transmits a light flux with the wavelength λ the objective lens converges a light flux with the wavelength λ converges a light flux with the wavelength λ converges a light flux with the wavelength λ when the objective optical lens forms the light flux with the wavelength λ the objective lens satisfies the following expressions: where NA