Non-diffractive optically variable security devices
conference paper
At the past optical security conferences attention was focused on diffractive structures, e.g. holograms, embossed gratings and thin—film devices, as security elements on valuable documents. The main reasons for this emphasis are, that the iridescent effect of such diffractive optically variable devices (OVD’s) can be easily observed by the naked eye and that their fraud-resistance is considered excellent. No attention has been paid to non—diffractive optically variable phenomena like reversible photosensitivity, e.g. luminescence and photochroism. These may be employed in non-diffractive OVD’s which may be readily authenticated and may provide excellent fraud-resistance as well. In order to survey the enormous variety of document security features the library SECURIDAT was compiled from a number of public domain databases. This paper discusses a few security applications of reversible photosensitivity that resulted from a search in SECURIDAT, viz. dual fluorescence with longwave remanence, thermochroism, stimulation of mixed inorganic phosphors and photochroism.
TNO Identifier
282188
Publisher
SPIE
Source title
Proceedings Holographic Optical Security Systems, ECO4, 14-15 March 1991, The Hague, The Netherlands
Editor(s)
Fagan, W.F.
Collation
13 p.
Place of publication
Bellingham, USA
Pages
113-125