26 March 1998 Methods of protection of volume holograms against optical copying
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Two methods were proposed for protection of holograms against optical copying and against the reconstruction of the model for holographic record. The first method is suitable for the production of master-holograms. It deals with the introduction of different phase inhomogeneities in the object beam with two-exposure technique. Thus a complicated fringe pattern is formed on/before the surface of the object of holographic record. The second method deals with the creation of the parts of the photosensitive media of volume holograms, which thickness differs from the thickness of the rest hologram. These parts have another color than the rest hologram, but in laser light they look black. The procedure of the creation of these marks is concerned with dry process of the OmniDex photopolymers and allows to apply such security marks continuously during the replication of holograms with DuPont's machine.
© (1998) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Theodor V. Bulygin, Gennady G. Levin, Leonid S. Yamnikov, Erick G. Semenov, and Nina V. Markova "Methods of protection of volume holograms against optical copying", Proc. SPIE 3294, Holographic Materials IV, (26 March 1998); doi: 10.1117/12.304528; https://doi.org/10.1117/12.304528

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