Patent ID: 7948841

Claim:
An optical pickup device comprising: one or more semiconductor lasers which emit a light beam, a first objective lens, which focuses the light beam emitted from the semiconductor lasers onto a first optical disc, a second objective lens which focuses the laser beam emitted from the semiconductor lasers onto a second optical disc, a grating which branches a light beam reflected from the second optical disc, an optical detector having a plurality of light receiving parts, which receives light beams branched by the grating, and an actuator which displaces the first and second objective lenses in a radial direction of the first optical disc, wherein the first and second objective lenses are mounted in juxtaposition, in a direction substantially perpendicular to the displacement direction, a center of the first objective lens is located on an axis extending from a center of the first optical disc in the displacement direction, the grating has six areas of a first area, a second area, a third area, a fourth area, a fifth area and a sixth area, the first area and the second area of the grating are in point symmetry with respect to the center of the grating, the third area and the fifth area of the grating are in point symmetry with respect to a center of the grating, the fourth area and the sixth area of the grating are in point symmetry with respect to the center of the grating, the first area of the grating is interposed between the fourth area and the fifth area, the second area of the grating is interposed between the third area and the sixth area, and center parts of the first area and the second area of the grating are arranged to be spaced by a distance d in a direction perpendicular to the displacement direction.