Patent ID: 8223613

Claim:
An optical pickup device adapted to interface with a multi-layer optical disc having a plurality of recording layers, comprising: a semiconductor laser diode which emits an optical flux; an objective lens which converges the optical flux emitted from said semiconductor laser diode and radiates the optical flux to an optical disc; a diffraction grating which branches an optical flux reflected from said optical disc; and a photodetector which receives an optical flux branched by said diffraction grating and has a plurality of light receiving parts, wherein: said diffraction grating has three areas A, B and C; among diffracted beams diffracted by a track of said optical disc, only a 0-th order diffracted beam diffracted on a track of said optical disc becomes incident upon said area A, and 0-th and ±1-st order diffracted beams diffracted on a track of said optical disc become incident upon said area B; said photodetector detects a reproduction signal from optical fluxes diffracted in said areas A, B and C; said plurality of light receiving parts which detect the +1-st order diffracted beam or the −1-st diffracted beam diffracted in said area A of said diffraction grating to which only said 0-th order diffracted beam diffracted on a track of said optical disc are disposed separated from light receiving planes which receive diffracted beams from other areas and aligned in a direction substantially perpendicular to a direction corresponding to the track of said optical disc.