Optical disc, device for checking optical disc and device for recording information on optical disc
US5696757A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 23, 1996 |
| Grant date | Dec 9, 1997 |
| Priority date | — |
| Expiry date | Sep 23, 2016 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B7/261
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
An optical disc on which a number of spiral trains of regular pits and at least one train of irregular pits are formed. The regular pits of each of the trains is arranged symmetrically with respect to the center of a track. Each of the irregular pits has a predetermined shape different from a shape of each of the regular pits. An arrangement of the train of the irregular pits being differs from an arrangement of each of the trains of the regular pits. A tracking error signal being obtained from the train of the irregular pits. An irregular pit can not be copied even when a normal optical disc containing such an irregular pit is copied by performing a conventional copying method. Thus, an illegal copy disc can be discriminated from a normal optical disc by checking whether or not an irregular pit is included in an optical disc to provide good copy protection by easily detecting an illegal copy disc.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.