| 摘要 |
PURPOSE: To detect an unfair copied disk by reproducing a physical characteristic information recording on a magnetic recording layer of optical recording medium with a magnetic head and collating the measured information with a measuring physical characteristic information detection means. CONSTITUTION: The CD can not be copied since a disk copy prohibition system is adopted. Further, ID No. different at every disk is recorded on the optical mark part 387 of the CD. For instance, the data of '204312001' are read by a photosensor 386 constituted of a light emitting part 386a and a light receiving part 386b to be inputted to Disk ID No. (OPT) of a key control table 404 in the memory of a CPU. Naturally, though this method is suitable, for further increasing a copy prevention effect, a high Hc part 401 with remarkably high Hc such as 40000e, etc., by barium ferrite is provided, and ID No. (Mag) data '205162' for magnetism is magnetically recorded in a factory. |
