Patent ID: 7697392

Claim:
An optical pickup apparatus which conducts reproducing and/or recording information for a first optical information recording medium comprising a first protective substrate whose thickness is t 1 and conducts reproducing and/or recording information for a second optical information recording medium comprising a second protective substrate whose thickness is t 2 (t 1 ≦t 2 ), the optical pickup apparatus comprising: a first light source to emit a first light flux having a wavelength λ 1 (350≦λ 1 (nm)≦480) for recording and/or reproducing the first optical information recording medium; a second light source to emit a second light flux having a wavelength λ 2 (λ 1 <λ 2 ) for recording and/or reproducing the second optical information recording medium; an output angle conversion element to convert an output angle of the first light flux and the second light flux which is incident to the output angle conversion element, wherein the output angle conversion element is placed fixedly in an optical path which is common to the first light flux and the second light flux and the output angle conversion element is a single lens; an objective optical element to converge the first light flux onto an information recording plane of the first optical information recording medium and the second light flux onto an information recording plane of the second optical information recording medium; a separation element to separate the first light flux and the second light flux which are output from the first light source and the second light source from the first light flux and the second light flux which are reflected on the information recording planes of the first optical information recording medium and the second optical information recording medium; and an optical detector to receive both of the first light flux and the second light flux which are reflected on the information recording planes of the first optical information recording medium and the second optical information recording medium, wherein both optical surfaces of the output angle conversion element are refractive surfaces, and wherein at least one optical surface of the objective optical element comprises a step structure in which patterns are arranged to be in a form of concentric circles whose center is on an optical axis of the objective optical element and the following formula is satisfied: 3×λ1/( n 1−1)≦ d ≦2×λ2/( n 2−1), where d represents an average depth of the step structures, n 1 represents a refraction index of the objective optical element for the first light flux, and n 2 represents a refraction index of the objective optical element for the second light flux.