Patent ID: 8040780

Claim:
An optical pickup device comprising: a semiconductor laser for emitting laser light; an objective lens for irradiating luminous flux emitted from said semiconductor laser to an optical disc; a diffraction grating for branching luminous flux reflected from the optical disc; and a photodetector having a plurality of light receiving parts which receive luminous flux branched by said diffraction grating; wherein: said diffraction grating has 3 sets of regions “A”,'“B”, and “C”; among disc diffraction light diffracted by a track formed on said optical disc, zero-order disc diffraction light is entered to said region “A” of the diffraction grating; and the zero-order disc diffraction light, +first-order disc diffraction light, and −first-order disc diffraction light are entered to the region “B” thereof; said photodetector detects a reproduction signal from grating diffraction light diffracted by said regions “A”, “B”, and “C”; two, or more light receiving parts of said photodetector for detecting either +first-order grating diffraction light or −first-order grating diffraction light of said diffraction grating region “A” are arrayed in a substantially straight line along a direction which is made substantially coincident with a radial direction of said optical disc; and wherein: two, or more light receiving parts of said photodetector for detecting either +first-order grating diffraction light or −first-order grating diffraction light of said diffraction grating region “B” are arrayed along a direction which is made substantially coincident with a tangential direction of said optical disc.