Optical disk having sub-blocks and sub-block indentification marks

An optical disk which comprises a true groove and on which positional information indicating a physical location on the track groove is represented by a wobble shape of the track groove,

• wherein the optical disk includes a plurality of positional information units that are arranged on the track groove, and
• wherein each said positional information unit includes:
• a positional information section that represents the positional information by a combination of wobble patterns selected from multiple types of wobble attains that have been defined so as to correspond to respective signal waveforms that rise and fall mutually differently;
• and
• a sync mark section having a wobble pattern in a shape distinguishable from the wobble patterns of the positional information section wherein the wobble patterns of each said positional information section are each defined by either a first displacement shape or a second displacement shape, the first displacement shape having been defined so as to correspond to a signal waveform that rises relatively steeply and falls relatively gently, the second displacement shape having been defined so as to correspond to a signal waveform that rises relatively gently and falls relatively steeply.