Patent ID: 7646696

Claim:
An objective element for use in an optical pickup apparatus including a first light source emitting a first light flux with a wavelength λ 1 for information reproducing and/or recoding, a second light source emitting a second light flux with a wavelength λ 2 for information reproducing and/or recording, a third light source emitting a third light flux with a wavelength λ 3 for information reproducing and/or recording and a light converging system having an objective optical element, for converging the first light flux on information recording surface of a first optical information recording medium having a protective layer with a thickness t 1 , converging the second light flux on information recording surface of a second optical information recording medium having a protective layer with a thickness t 2 , and converging the third light flux on information recording surface of a third optical information recording medium having a protective layer with a thickness t 3 , the objective optical element comprising: two or more optical elements having a first surface including a first phase difference providing structure and a second surface including a second phase difference providing structure, the first phase difference providing structure has a plurality of ring-shaped zones whose centers are on an optical axis when the first surface is viewed from an optical axis direction and the second phase difference providing structure has a plurality of ring-shaped zones whose centers are on an optical axis when the second surface is viewed from an optical axis direction; wherein the first light flux enters into the objective optical element as an almost infinite parallel light flux for information reproducing and/or recording on the first optical information recording medium, the second light flux enters into the objective optical element as an almost infinite parallel light flux for information reproducing and/or recording on the second optical information recording medium, and the third light flux enters into the objective optical element as an almost infinite parallel light flux for information reproducing and/or recording on the third optical information recording medium, and wherein the first phase difference providing structure corrects a spherical aberration of the objective optical element by providing a phase difference to light fluxes with at least two of the wavelengths λ 1 , λ 2 , and λ 3 , and the second phase difference providing structure corrects a spherical aberration of the objective optical element by providing a phase difference to light fluxes with at least two of the wavelengths λ 1 , λ 2 , and λ 3 .