Patent ID: 8693295

Claim:
An optical disc medium comprising: a substrate; and a recording layer, the recording layer having a plurality of track groups, each track group having a plurality of adjacent information pit trains structured with information pits having the same pit depth and arranged circularly or spirally, wherein the information pit depth of the track groups changes periodically, at a group pitch, radially along the optical disc medium, and the information pit depth of adjacent track groups differ; the number of inforamtion pit trains forming each track group is identical to the number of information pit trains forming an adjacent track group, and the width of each of the information pits is less than or equal to a light-condensing spot's diffraction limit given λ/(4×NA) determined by a numerical aperture NA of an objective lens and a wavelength λ in use, as specifications of an optical disc device which records or plays back using the disc medium.