Secure card and sensing system
US4656473A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Oct 4, 1984 |
| Grant date | Apr 7, 1987 |
| Priority date | — |
| Expiry date | Oct 4, 2004 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG07F7/12
- WIPO fieldControl
- WIPO sectorInstruments
Abstract
An identification card is disclosed as for supporting commercial or other significant transactions involving a designated subject. The card incorporates a machine-readable record and is produced with an individual birefringent characteristic to modulate a light beam for card identification. In one embodiment, the card incorporates apparent stress waves to modulate an orientation-frequency characteristic (e.g. polarization angle) of a light beam. The machine-readable record on the card indicates the characteristic birefringence for confirming the card to be authentic. Methods are disclosed for producing and testing the cards. A system is disclosed for sensing card characteristics by modulated light including polarized light techniques to record and verify the cards with allowance for changes, as by card aging.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.