Patent ID: 6735160
Filing Date: 2004-05-11
Classification: G11B

Abstract:
An optical disc on which primary digital information and secondary digital information are recorded, wherein:the primary digital information is recorded as pits that are formed at discrete reference positions on a track; the secondary digital information is recorded as deviations of slight amounts in positions of certain pits from corresponding reference positions; each slight amount is within a range where pits that are formed on an optical disc on which only the primary digital information is recorded deviate from corresponding reference positions during reproduction; the secondary digital information is recorded with a phase modulation where edges that determine lengths of the certain pits in a track direction are formed at positions whose phases are advanced and delayed by the slight amounts from corresponding positions when the certain pits are formed to record only the primary digital information; and each slight amount is constant and is within a range of jitter that is observed, during reproduction, for pits on an optical disc on which only the primary digital information is recorded.