Patent ID: 8125873

Claim:
An objective lens for use in an optical pickup apparatus which conducts reproducing and/or recording information by converging a light flux with a predetermined wavelength λ 1 meeting 390 nm≦λ 1 ≦420 nm on a information recording surface of an optical information recording medium, wherein at least part of a plurality of basic structures as optical path difference providing structures are mutually superimposed and formed on a predetermined region of an optical surface of the objective lens, and the objective lens satisfying the following expression: (λβ−λ1)−×(λα−λ1)<0 (1) where λα is a wavelength within a range of the wavelength λ 1 ±50 nm and at which a diffraction efficiency of one of the plurality of basic structures is maximized, and 243 is a wavelength within a range of the wavelength λ 1 ±50 nm and at which a diffraction efficiency of another of the plurality of basic structures is maximized.