Harmonic-based verifier device for a magnetic security thread having linear and non-linear ferromagnetic characteristics
US5614824A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | May 15, 1995 |
| Grant date | Mar 25, 1997 |
| Priority date | — |
| Expiry date | May 15, 2015 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG07D7/004
- WIPO fieldControl
- WIPO sectorInstruments
Abstract
A security thread for use in a paper-based value document, such as currency or banknote paper, includes a plastic substrate coated with one or more regions of "soft" magnetic material. A device for verifying both the authenticity and the denomination of the document includes a coil that is driven by an alternating current to thereby provide a uniform magnetic field within a predetermined spatial region. As the document passes in proximity to the drive coil, the applied magnetic field saturates the regions of magnetic material on the security thread. The magnetic regions provide a response magnetic field that, because of the saturation of the magnetic regions, is a non-linear response containing a multiple of frequency components, including a component at the fundamental or drive frequency and various harmonic frequency components. A receive coil senses the response magnetic field. A signal processor connected to the receive coil utilizes the response signals at the fundamental frequency and the low-order harmonic frequencies to determine both the type of magnetic material on the security thread and the denomination of the document from the spatial distribution of the magnetic regio…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.