Patent ID: 7489615

Claim:
An objective optical element 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 first light flux with a wavelength λ 1 emitted by a first light source, for recording and/or reproducing information on a second optical information recording medium having a protective substrate with a thickness t 2 (t 1 ≦t 2 ) using a second light flux with a wavelength λ 2 (λ 1 <λ 2 ) emitted by a second light source and for recording and/or reproducing information on a third optical information recording medium having a protective substrate with a thickness t 3 (t 2 <t 3 ) using the third light flux (λ 2 <λ 3 ) emitted by the third light source and for forming a converged spot on an information recording surface of each of the first through third optical information recording media, the objective optical element comprising: a first phase structure for compensating a deterioration in a performance forming the converged spot on the information recording surface of the first optical information recording medium caused by an temperature change; a second phase structure for reducing a spherical aberration based on a thickness difference between the protective substrate t 1 and the protective substrate t 2 or a wavelength difference between the wavelength λ 1 and the wavelength λ 2 ; and a third phase structure for reducing a spherical aberration based on a thickness difference between the protective substrate t 1 and the protective substrate t 3 .