Patent ID: 7336576
Filing Date: 2008-02-26
Classification: G11B

Abstract:
1. An optical disk medium having a spiral recording track, wherein: said optical disk medium comprises a plurality of tilt detection areas formed at a plurality of radial positions on said medium, each of said tilt detection areas having a plurality of special marks (SM) for detecting a plurality of tilts of said medium in a single round of said medium; a plurality of grooves are periodically formed in a radial direction of said medium, said optical disk medium having, as said recording track, said grooves or a plurality of lands between said grooves or both of said grooves and said lands; and each of said special marks being formed by first and second coupling portions arranged in close proximity to each other in a tracking direction along which said recording track extends, said first coupling portion being formed as a coupling groove having a depth substantially equal to that of said grooves and a length in said tracking direction which is longer than twice a groove pitch of said grooves, said first coupling portion coupling a particular one of the grooves and one of two grooves adjacent to said particular groove on opposite sides thereof, said second coupling portion being formed as a coupling groove having a depth substantially equal to that of said grooves and a length in said tracking direction which is longer than twice said groove pitch, said second coupling portion coupling said particular groove and the other of said two grooves.