15 March 1996 Computer-generated optically variable devices containing hidden information
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Abstract
A new optically variable device characterized by both rainbow holographic effects and two kinds of hidden elements is presented. Both components are recorded as computer generated Fourier holograms. The first hidden element is a slit or small image formed by a line of text or other image contained in a slit-shaped frame. Under normal illumination conditions the first element shows rainbow holographic and kinematic effects. The second element is a darker image visible at an angular range different than that of the first element. This second image is less visible under usual white light illumination conditions, but appears sharply in laser light. The advantage of the optically variable device proposed is that it gives both rainbow holographic effect and hidden Fourier-plane images at the same time from the whole hologram area. In this way, the need to use special encoded subfields which attract attention is eliminated.
© (1996) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Pawel J. Stepien, Remigiusz Gajda, Tomasz Szoplik, "Computer-generated optically variable devices containing hidden information", Proc. SPIE 2659, Optical Security and Counterfeit Deterrence Techniques, (15 March 1996); doi: 10.1117/12.235466; https://doi.org/10.1117/12.235466
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