Patent ID: 7623434
Filing Date: 2009-11-24
Classification: G11B

Abstract:
1. An objective optical lens for use in an optical pickup apparatus for recording and/or reproducing information by converging a first light flux with a wavelength λ 1 (λ 1 <450 nm) emitted by a first light source on an information recording surface of a first optical information recording medium through a first protective substrate with a thickness t 1 , for recording and/or reproducing information by converging a second light flux with a wavelength λ for recording and/or reproducing information by converging a third light flux with a wavelength λ an optical surface divided into at least two areas including: a central area including an optical axis and comprising a first diffractive structure; and a peripheral area surrounding the central area and comprising a second diffractive structure, the objective lens is a single lens and is commonly used for the first to third optical information recording media, the objective lens converges diffracted light fluxes of the first to third light fluxes generated in the first diffractive structure onto information recording surfaces of the first to third optical information recording media, respectively, the diffracted light fluxes of the first to third light fluxes generated in the first diffractive structure have same diffraction order as each other, and the objective lens converges diffracted light fluxes of the first and second light fluxes generated in the second diffractive structure onto information recording surfaces of the first and second optical information recording media, respectively, the diffracted light fluxes of the first and second light fluxes generated in the second diffractive structure have different diffraction order as each other, wherein the second diffractive structure is a wavelength selective diffractive structure comprising a plurality of patterns arranged concentrically, each of the plurality of patterns has a cross section including an optical axis in a stepped shape with a plurality of levels, each step of the stepped shape is shifted by height of steps corresponding to a predefined number of the plurality of levels for every predefined number of the levels, and the diffraction orders of the diffracted light fluxes of the first and second light fluxes generated in the second diffractive structure are 0 for the first light flux and 1 for the second light flux.