Patent ID: 7974172

Claim:
An optical pickup apparatus comprising: a laser light source configured to selectively emit laser light with a first wavelength and laser light with a second wavelength, the first and second wavelengths being different from each other; a diffraction grating including first and second regions of periodic structures different in phase from each other and a third region which is disposed between the first and second regions and of which a periodic structure is different in phase from the first and second regions, the diffraction grating being configured to diffract the laser light to generate a main luminous flux and a sub luminous flux; an objective lens configured to focus the main luminous flux and the sub luminous flux generated by the diffraction grating on the same track of an optical disc; and a photodetector configured to receive reflected light of the main luminous flux and the sub luminous flux focused on the optical disc, and output a detection signal for generating a main push-pull signal and a sub push-pull signal, a relationship between a width of incident light incident on the objective lens corresponding to the third region, and pupil diameters of the objective lens corresponding to the first and second wavelengths being adjusted so that a ratio of a minimum value to a maximum value of a signal level of a differential push-pull signal generated from the main push-pull signal and the sub push-pull signal is substantially 50% or more, and a ratio of a signal level of the sub push-pull signal to a signal level of the main push-pull signal is substantially 15% or more, in both cases of the laser lights with the first and second wavelengths.