Patent ID: 7218599
Filing Date: 2007-05-15
Classification: G11B

Abstract:
1. An optical pickup, comprising: a light source for emitting a light beam; a converging element for converging the light beam onto an optical recording medium; an optical diffraction element, that is provided between the light source and the converging element, for dividing the light beam into at least a main beam and two sub-beams; and a photodetector section including light receiving elements for respectively receiving light beams divided by a parting line along a track direction of the optical recording medium, said light beams reflected from the optical recording medium; the optical diffraction element including first concavo-convex patterns, each having a concavo-convex shape with a groove formed in a direction perpendicular to the track direction, and second concavo-convex patterns, each having a concavo-convex shape which deviates from that of the first concavo-convex pattern, the optical diffraction element further including at least first through third allocation pattern regions successively provided in the direction perpendicular to the track direction, the allocation pattern regions being classified in accordance with allocation patterns formed by at least one of the first and second concavo-convex patterns, and when (i) a region borderline, extending parallel to the track direction, which is formed in an allocation pattern border section between the first and second allocation pattern regions provided successively, and (ii) each concavo-convex pattern border section between the first and second concavo-convex patterns overlap, the concavo-convex pattern border sections are provided so that at least one of (1) a linear overlapping section where the region borderline and a part of pattern borderlines in a pattern borderline group in the concavo-convex pattern border sections, each extending parallel to the track direction, overlap, and (2) a point overlapping section where the region borderline and at least one point of the concavo-convex pattern border sections overlap is formed.