Volumetric holographic photocopy prevention film

摘要

The present invention is directed to a photocopy prevention film applied to a document to be protected that comprises either a volume holographic refraction grating or a surface holographic refraction grating. The refraction grating is bonded to a document and either causes normally scattered light to be focused toward the photoreceptors of a photocopy machine or causes light normally reflected toward the receptors to be scattered away from the receptors. The film is created by splitting a coherent laser beam into a reference beam and a target beam. The target beam reflects off of a special target and onto a photographic emulsion. The reference beam is also incident to the photographic emulsion. The beam reflected from the target and the reference beam create interference planes within the emulsion which can be developed to create differing refractive index planes within the emulsion or etched away to create a surface grating. The beam and target can cause the film to scatter or focus the light depending on whether saturation of the photoreceptors or black-out of the photoreceptors is desired.