Patent ID: 6898169
Filing Date: 2005-05-24
Classification: G11B

Abstract:
1. An optical pickup head device comprising: a light source for emitting a light beam; a diffraction means for diffracting the light beam from the light source into a plurality of beams of zero-order diffracted light and at least first-order diffracted light; a convergence means for converging the beams from the diffraction means on an optical recording medium; a beam splitting means for splitting the beams reflected from the optical recording medium; and a photodetection means for receiving the beams from the beam splitting means and outputting a signal that corresponds to an amount of light received, wherein the optical recording medium comprises tracks for recording information, the diffraction means comprises grating patterns with a nonuniform period or phase, a size of the at least first-order diffracted light converged on the optical recording medium is larger in a direction parallel to a tangent to the track than in a direction perpendicular to the tangent, and P