Method for tamper-proof identification using photorefractive crystals
US5619025A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | May 5, 1994 |
| Grant date | Apr 8, 1997 |
| Priority date | — |
| Expiry date | May 5, 2014 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06K19/06046
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
A method and apparatus for document verification exploits a temporally variable physical process to generate a reproducible effect that cannot be copied. A document such as a credit card is provided with a spot or stripe that incorporates at least one, and preferably a large plurality of photorefractive crystals arrayed in a random manner. The document verifying apparatus includes a coherent light source such as a diode laser to illuminate the photorefractive crystals, and a photosensor to receive light scattered from the photorefractive crystals. The random distribution and orientation of photorefractive crystals comprises a unique characteristic for each card or document, and this characteristic is not based on any assigned number or code. The response of photorefractive crystals to the coherent illumination comprises a time-varying characteristic that is dependent upon the intensity and temporal nature of the illumination itself. Input to the laser illuminator may be varied to elicit differing responses from the photorefractive crystals, and this factor may be very difficult for a counterfeiter to ascertain. Also, for any given illumination intensity or temporal pattern, the ima…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.