| 摘要 |
The invention provides a method of providing copy protecting to data recorded on a data medium of the CD-ROM type that is readable by means of a laser beam. Applications thus lie in providing copy protection for digital optical disks (CD-ROM, DVD-ROM, etc.). The medium includes a sensitive zone over at least a portion of its surface, said zone possessing at least one optical property that is modified on being illuminated by the laser beam. The method implies that a computer program using the data reads from the sensitive zone on at least two separate occasions and compares the results of the reads in order to verify that the optical property of the sensitive zone has indeed been modified. The modification to the optical property is maintained for a predetermined duration of modification. The sensitive Zone may cover the entire medium. The optical property that is modified may be index of reflection or polarization. The sensitive zone con be obtained by depositing a layer of a photorefractive material such as lithium niobate. |
