Security document and method using invisible coded markings
US6138913A · kind A · utility
112Cited by
79References
23Claims
0Family size
Assignee
Inventors
Key dates
| Filing date | Jan 5, 1998 |
| Grant date | Oct 31, 2000 |
| Priority date | — |
| Expiry date | Jan 5, 2018 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06K19/14
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
An invisible indicia or encoded information is imprinted on a substrate using a compound which produces a fluorescence at a wavelength greater than about 650 nm when exposed to near infrared radiation. The information covered by a layer of material that reflects or absorbs a substantial amount of the visible and UV radiation illuminating its surface.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.