Playback system for an optical disc representing a character or a graphic pattern formed by specified pit patterns
US5875156A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jan 6, 1998 |
| Grant date | Feb 23, 1999 |
| Priority date | — |
| Expiry date | Jan 6, 2018 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B7/0079
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A CD-ROM is provided with an area for forming a character/graphic pattern. The character/graphic pattern is formed in such a way that data, which generate on the CD-ROM two sorts of pit patterns having average reflectances different from each other to a perceptible extent, are respectively recorded inside and outside the character/graphic pattern. Unless an illegal copy disc is produced by duplicating the legal original disc of the CD-ROM at a very high precision, the character/graphic pattern of the copy disc is invisibly deformed by the discrepancy between the arrangements of the pit patterns of the copy disc and the original disc.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.