Optically Variable Ink
Optically variable ink (OVI) is an anti-counterfeiting measure used on many major modern banknotes.
The ink displays two distinct colors depending on the angle the bill is viewed at. The United States fifty-dollar bill, for example, uses color shifting ink for the numeral 50 so that it displays copper at one angle and bright green in another. [1]
OVI is particularly useful as an anti-counterfeiting measure as it is not widely available; the major manufacturer is a Swiss company called SICPA.
Color-shifting inks reflect various wavelengths in white light differently, depending on the angle of incidence to the surface. An unaided eye will observe this effect as a change of color while the viewing angle is changed. A color copier or scanner can copy a document only at one fixed angle relative to the document’s surface.[2]
[edit] References
- ^ http://www.sicpa.com/731/764/1860/1911/7512.asp
- ^ http://www.icao.int/mrtdsymposium/2007/Docs/DIS_ICAO_Montreal_Presentation%202007_final.pdf
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