Methods and systems using multiple watermarks
US6636615B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Nov 3, 1999 |
| Grant date | Oct 21, 2003 |
| Priority date | — |
| Expiry date | Nov 3, 2019 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B20/00086
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
Two or more digital watermarks, with different characteristics, are embedded in a document. The characteristics are chosen so that the watermarks will be affected in different manners if the document is subsequently copied or reproduced. The detection process or mechanism reads two or more of the watermarks and compares their characteristics. While wear and handling may change the characteristics of the digital watermarks in a document, the relationship between the characteristics of the multiple digital watermarks in a document will nevertheless give an indication as to whether a document is an original or a copy of an original. Document wear can be independently assessed and used as an aid in interpreting the detected watermark characteristics.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.