DIFFRACTIVE STRUCTURES WITHIN POLYMER SUBSTRATES, THEIR MANUFACTURE AND USE
Disclosed are optical devices suitable as security devices for document authentication, which comprise at least one two-dimensional array of elongate laser-modified tracks extending within a document substrate that have a distinct optical refractive index compared to the unmodified substrate, which...
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Main Authors | , , , , |
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Format | Patent |
Language | English French German |
Published |
26.07.2023
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Subjects | |
Online Access | Get full text |
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