Documents and methods involving multiple watermarks
US7539325B2 · kind B2 · utility
55Cited by
108References
22Claims
0Family size
Assignee
Inventors
Key dates
| Filing date | Jun 1, 2004 |
| Grant date | May 26, 2009 |
| Priority date | — |
| Expiry date | Apr 4, 2026 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B20/00086
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
Two or more digital watermarks are embedded in a document. In one implementation the digital watermarks include characteristics that are chosen so that the watermarks will be affected in different manners if the document is subsequently copied or reproduced. A detection method or mechanism reads two or more of the watermarks and compares their characteristics. In another claim, two or more digital watermarks correspond to characteristics that are evaluated for authentication. Of course, other claims are provided as well.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.