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19 April 2002 Achromatic features for optically variable devices
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Proceedings Volume 4677, Optical Security and Counterfeit Deterrence Techniques IV; (2002)
Event: Electronic Imaging, 2002, San Jose, California, United States
We have studied the use of achromatic features in Optically Variable Devices (OVD) for document security applications. We present various forms of matt structures as we have implemented them in OVD designs. By tailoring the scattering characteristics of the surface relief, we have created OVDs which appear in various intensities of white or gray, and whose brightness can vary as the viewing conditions are changed. Furthermore, we have realized surface reliefs which appear bright and colorless when viewed within a predetermined solid angle and appears dark in all other viewing directions. The gratings appear bright and colorless when viewed from one side of the grating normal; however, when these gratings are rotated by 180 degrees in their plane, the gratings appear dark. We will show gratings of this type, where the surface reliefs have been engineered so that the bright and colorless appearance covers an enlarged solid angle.
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Andreas Schilling, Rene Staub, and Wayne Robert Tompkin "Achromatic features for optically variable devices", Proc. SPIE 4677, Optical Security and Counterfeit Deterrence Techniques IV, (19 April 2002);

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