Patent ID: 7898927
Filing Date: 2011-03-01
Classification: G11B

Abstract:
1. An optical pickup device for recording information onto an optical information recording medium and reading and erasing information recorded on the optical information recording medium, comprising: a light source; a diffraction grating for separating a light beam emitted from the light source into at least three light beams; and a photodetector for receiving the separated light beams reflected from the optical information recording medium, wherein the diffraction grating is divided into a first region, a second region, a third region, and a fourth region having periodic structures of different phases from one another by dividing lines extending in a direction parallel to a tangential direction of tracks of the optical information recording medium, the second region and the third region are located between the first region and the fourth region sequentially from the first region side, the periodic structure of the second region has a phase difference of approximately 180 degrees from the periodic structure of the third region, the periodic structure of the first region has a phase difference of approximately 180 degrees from the periodic structure of the fourth region, and the light source includes a first light source and a second light source.