Varying the rate at which data appear on an optical disc rotated at a constant linear velocity to prevent unauthorized duplication of the disc
US6477124B2 · kind B2 · utility
Assignee
Inventor
Key dates
| Filing date | May 18, 2001 |
| Grant date | Nov 5, 2002 |
| Priority date | — |
| Expiry date | May 29, 2021 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B20/00086
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
Apparatus and method for recording data to an optical disc to prevent unauthorized duplication of the disc. The disc includes a data placement zone to which first data are written at a first data rate as the disc is rotated at a selected linear velocity. The disc further includes a velocity disruption zone to which second data are written at a second different data rate as the disc is rotated at the selected linear velocity. The variation in frequency between the first and second data rates preferably causes a readback system to lose frequency lock on the second data during a continuous access operation on the first and second data. An unauthorized disc can also be detected by comparing the disc linear velocity as the second data are accessed to a target linear velocity. Access to the disc can be denied when a velocity mismatch is detected.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.