Patent ID: 8094542
Filing Date: 2012-01-10
Classification: G11B

Abstract:
1. An optical pickup device comprising: a semiconductor laser that emits a laser beam; a diffraction grating that diverges a luminous flux emitted from said semiconductor laser; an objective lens that irradiates the luminous flux, emitted from said semiconductor laser, onto an optical disc; and an optical detector that receives the luminous flux reflected by the optical disc wherein said diffraction grating has a first area and a second area that have the same groove period and that have a phase difference of 180 degrees in groove period structures, a division line that separates the first area and the second area is a division line running through a center of said diffraction grating and continuing from one end of said diffraction grating to another end or from one position on one end of said diffraction grating to another position on the end, wherein, when a virtual line running through a center of said diffraction grating orthogonally to the grooves is assumed to be a center line, the division line that separates the first area and the second area comprises a first division line extending from one end of said diffraction grating to the center line, a second division line running from another end, which is opposite to the one end, to the center line, and a third division line running through the center and connecting the first division line and the second division line and in a direction orthogonal to the grooves, a position on the one end of said first division line is different from a position on the another end of said second division line.