Varying tone securing document
US5197765A · kind A · utility
44Cited by
17References
45Claims
0Family size
Assignee
Inventors
Key dates
| Filing date | Jul 12, 1991 |
| Grant date | Mar 30, 1993 |
| Priority date | — |
| Expiry date | Jul 12, 2011 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S283/902
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
An improved security document which protects documents from copying on color copying machines. The document has cancellation terms and background pattern in two tones. If the copier is adjusted to obscure the cancellation term on reproduced copies at one tone, the cancellation at the other tone will appear. In an alternative embodiment, the density of the cancellation term and the background pattern vary across the face of the document. In this case, the cancellation term will appear somewhere on the copy no matter what copier adjustments are made.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.