Patent ID: 8605559

Claim:
An optical pickup device comprising: a laser diode, which emits a laser light therefrom; an objective lens, which is configured to irradiate the light beam emitting from said laser diode upon an optical disc; a diffraction grating, which is configured to divide the light beam reflecting on an optical disc; and a photo detector including plural numbers of at least a first light receiving region and a second light receiving region, which are configured to detect the light beams divided by said diffraction grating, wherein the first and second light receiving regions include a plurality of light receiving parts, respectively, said diffraction grating is divided, by a division line nearly coincident with a tangential direction of said optical disc, passing through a center of said diffraction grating, and a division line nearly coincident with a radial direction of said optical disc, into at least four (4) grating regions, not including therein the division line nearly coincident with the radial direction of said optical disc, the first and second light receiving regions detect either one, a +1 st dimensional grating diffraction light or a −1 st dimensional grating diffraction light of the light beam entering into at least the four (4) grating regions, not including the division line nearly coincident with the radial direction of said optical disc are aligned, the plurality of light receiving parts of the first light receiving region are aligned nearly on a straight line in a direction nearly coincident with the radial direction of said optical disc, the plurality of light receiving parts of the second light receiving region for detecting the other dimensional grating diffraction light are aligned, with shifting with respect to a direction nearly coincident with the tangential direction of said optical disc, and a line connecting the plurality of the light receiving parts of the second light receiving region is on a line approaching to be vertical with respect to a direction into which the light beam on the light receiving parts fade away.