Overt and covert verification via magnetic optical security devices

Paul G. Coombs; Vladimir Raksha; Tom Markantes

doi:10.1117/12.462709

19 April 2002 Overt and covert verification via magnetic optical security devices

Paul G. Coombs, Vladimir Raksha, Tom Markantes

Proceedings Volume 4677, Optical Security and Counterfeit Deterrence Techniques IV; (2002) https://doi.org/10.1117/12.462709
Event: Electronic Imaging, 2002, San Jose, California, United States

Abstract

The currency of over 70 countries is protected today by security ink incorporating microscopic optical interference filters. The physics of light interference enables the manufacture of multi-layer security devices such as these that are both highly chromatic and color shifting. Further, the technique of thin film deposition allows the inclusion of layers that perform magnetically as well as optically. This investigation involved the creation of security devices that bring together the usually separate functionalities of overt optical and covert magnetic verification into a single device. This allows the devices to be used both for information storage as well as for overt detection and verification--thereby creating improved protection without the addition of separate security devices. Two examples are explored: an optically variable magnetic stripe and a product tag into which an identifiable covert pattern is magnetized. Integrated devices were produced using several different magnetic metals and alloys. The optical and magnetic characteristics of each device were measured and the results included in this report. Devices were built using single-component magnetic layers as well as more complex magnetic materials. Parameters relevant to magnetic materials include remanence (field strength remaining after magnetization) and coercivity (resistance to demagnetization). Also relevant to optical devices is their so-called color travel-often plotted as an arc in a* b* or L* a* b* space. The color travel of sample devices was measured to allow comparison.

Citation Download Citation

Paul G. Coombs, Vladimir Raksha, and Tom Markantes "Overt and covert verification via magnetic optical security devices", Proc. SPIE 4677, Optical Security and Counterfeit Deterrence Techniques IV, (19 April 2002); https://doi.org/10.1117/12.462709

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