Patent ID: 8050163
Filing Date: 2011-11-01
Classification: G11B

Abstract:
1. An optical disc producing method of producing a read-only optical disc in which recording is made in units of a cluster including a row of recording-information bits and an error-correcting code, lands and pits are formed contiguously to each other along a recording track and a sequence of lands and pits complies with a predetermined variable-length modulation rule, the method comprising: a disc forming step of forming the read-only optical disc with the use of an optical disc master; and an identifier appending step of additionally writing a disc-unique identifier to a specific cluster on the read-only optical disc by irradiating laser light having a power higher than a reading power level to the lands to give the lands an optical property equal to that of the pits, in the identifier appending step, with continuous areas corresponding to bits of the identifier being preset in predetermined positions in the cluster, the lands included in each continuous area and located in positions where an entire bit row will comply with the variable-length modulation rule even if the lands are replaced with pits being changed by lasering corresponding to a value of each bit in the identifier appending step to have an optical property equal to that of the pits.