Patent ID: 7701813
Filing Date: 2010-04-20
Classification: G11B

Abstract:
1. A recording and reproduction apparatus that records and reproduces information by directing a laser beam at an optical recording medium having (i) spiral or concentric circular grooves for tracking a laser beam, (ii) an information recording layer, (iii) an identification region, and (iv) an information recording region, wherein a track pitch Tp 2 of the circular grooves that are formed in the identification region is larger than a track pitch Tp 1 of the circular grooves that are formed in the information recording region, and wherein a width of the circular grooves formed in the identification region is less than a width between the circular grooves, the recording and reproduction apparatus comprising: an irradiation unit for directing the laser beam at the optical recording medium; a light receiving unit for receiving the laser beam reflected by the information recording layer, the reflected laser beam being received by a photodetector that is split into two parts by a split line parallel to a direction of the circular grooves; a control unit for determining whether the circular grooves on a side of the optical recording medium where the laser beam is incident are convex or concave based on sum signal and a difference signal of photodetection signals outputted from the photodetector, and for subjecting the circular grooves to tracking control based on a result of the determination of whether the circular grooves are convex or concave; and an objective lens arranged to make a spot diameter of the laser beam directed by the irradiation unit larger than the width of the circular grooves formed in the identification region and less than the width between the circular grooves formed in the identification region.