Patent ID: 6469969
Filing Date: 2002-10-22
Classification: G11B

Abstract:
In a method for writing data to an optical disc wherein a first set of data having a desired informational content is modulated to provide a corresponding series of data symbols, each data symbol having a leading edge, a trailing edge and a nominal symbol length corresponding to a population of preselected symbol lengths, and wherein relative timing of at least selected ones of the leading and trailing edges are adjusted to improve optical disc readback characteristics, the improvement characterized as the method further comprising steps of:(a) providing a second set of data; and (b) further adjusting at least selected ones of the leading edges or trailing edges of the data symbols to embed the second set of data upon the series of data symbols so that the informational content of the first set of data is stored in relation to lengths of pits and lands on the optical disc and the informational content of the second set of data is stored in relation to variations of the lengths of the pits and lands, wherein the second set of data provides hidden codes associated with the optical disc which are substantially undetectable to a human upon visual inspection of the optical disc.