Patent ID: 7826314

Claim:
An apparatus for reading subdivided information from an optical disk, which comprises a track groove and on which information is recorded along the track groove, the track groove including a plurality of unit sections that are arranged along the track groove and that have side faces displaced periodically along the track groove, the side faces of the unit sections being displaced in a single fundamental period, the subdivided information allocated to each said unit section being represented by a shape given to the unit section, and the side faces of each said unit section being displaced according to a pattern to be selected from first and second wobble patterns that have the same fundamental frequency but mutually different shapes, wherein the apparatus comprises: an optical head, which irradiates the optical disk with light and generates an electric signal responsive to part of the light that has been reflected from the optical disk, read signal processing means for generating a wobble signal which has an amplitude changing with the wobble pattern from the electric signal, rise value acquiring means for sampling and holding an absolute gradient value of the wobble signal when the signal rises, fall value acquiring means for sampling and holding an absolute gradient value of the wobble signal when the signal falls, and subdivided information detecting means for determining the subdivided information by majority by comparing the values held by the rise and fall value acquiring means with each other.