Abstract

Optical coatings that display color shifts with viewing angle are ideal candidates for document security devices since the average person can detect the color shift and such shifts readily defeat color copiers, printers and cameras. Documents made using these instruments do not have the telltale color shift of the original and thus can be readily identified as being counterfeit. The optical signature in its final product form must also be immune to simulation and origination. Furthermore, it must be able to withstand all the rigors arising from normal handling and machine verification.

© 1995 Optical Society of America