Patent ID: 7660225

Claim:
An objective lens for use in an optical pickup apparatus, the optical pickup apparatus comprising: a first light source for emitting a first light flux with a first wavelength λ 1 ; a second light source for emitting a second light flux with a second wavelength λ 2 ; a converging optical system comprising an objective lens; and a photodetector, wherein the optical pickup apparatus reproduces and/or records information for a first optical information recording medium having a protective layer with a thickness t 1 by using the first light flux with the first wavelength λ 1 emitted by the first light source, the optical pickup apparatus reproduces and/or records information for a second optical information recording medium having a protective layer with a thickness t 2 (t 1 ≦t 2 ) by using the second light flux with the second wavelength λ 2 (λ 1 <λ 2 ) emitted by the second light source, the objective lens comprising: an optical surface comprising at least two regions including a central area including an optical axis; and a peripheral area surrounding the central area, wherein the objective lens has a single lens structure, and the central area comprises a diffractive structure in which a diffraction order providing a maximum efficiency for each of the first light flux and the second light flux is a same each other, and a phase structure providing a same amount of optical path difference for each of the first light flux and the second light flux.