Patent ID: 7280458

Claim:
An optical pickup apparatus comprising: a first light source to emit a first light beam having a first wavelength corresponding to a recording medium; a first optical path changer to change a proceeding path of the first light beam incident thereon towards the recording medium; an objective lens to receive from said first optical path changer and to focus the first light beam to form a light spot on a recording surface of the recording medium; a diffraction member to divide and diffract the first light beam reflected by the recording medium and having passed through said objective lens to be incident thereon, the reflected first light being divided into five light regions, said diffraction member comprising a first diffraction region being wider in a tangential direction corresponding to a tangential direction of the recording medium than in a radial direction corresponding to a radial direction of the recording medium, and second through fifth diffraction regions sequentially arranged in the tangential and radial directions such that adjacent ones of the second through fifth diffraction regions in the radial direction are separated by the first diffraction region; and a first photodetector having first through fifth light receiving portions to receive corresponding portions of the first light beam reflected by the recording medium and diffracted by the first through fifth diffraction regions of said diffraction member and having passed through said objective lens and said first optical path changer; wherein the first diffraction region generates ±1 st order beams and includes an astigmatism generation pattern so that the ±1 st order beams are magnified in the radial direction.