Vladimir P. Raksha

Integration of contrasting technologies into advanced optical security devices

OVP security pigment, the active ingredient in OVI security ink, is an assembly of high performance microscopic filters. The market acceptance of these filters has led them to become perhaps the most widely distributed interference devices on the planet. Recently, interference devices have been developed that provide the security industry with features beyond proven overt protection. New products are being launched that unite the attributes of optical interference with those of other technologies. One approach integrates thin film interference and diffractive interference to create a host of new security devices. The combined effects are complex and often surprising. The science behind the fusion is explored and the effects demonstrated. Interference pigment technology has also been combined with the science of magnetics to create a new line of OVP security pigments. To facilitate the practical use of such pigments, novel application technology has been developed which allows for the creation of new overt effects. This paper examines pigment designs and describes the physics behind the advanced application technology. The science of layering security features has long been demonstrated effective in deterring counterfeiting. Now it is possible to provide multiple layers of security within the same device through the integration of proven technologies.

Overt and covert verification via magnetic optical security devices

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.