| 摘要 |
Hard to simulate, readily distinguishable from counterfeits, optical interference authenticating devices are provided by depositing two coatings on a substrate, each coating comprising at least one optical interference layer, the material of each layer being selected so that the two coatings together and separately have different spectral reflectance and spectral transmittance characteristics at different angles of incidence of light thereon. The substrate may be, for example, a polyester film and a first one of the coatings is sufficiently radiation absorbing of, say, infrared radiation that at least one portion of that coating can be removed by an infrared laser beam through, for example, a mask to provide a readily distinguishable pattern on the substrate. The first coating may be, for example, a multilayer absorber coating containing Inconel, aluminum or some other suitable material, while the other coating, which is insufficiently radiation absorbing by, for example, infrared radiation to be substantially resistant to excavation solely by the infrared laser beam may be, for example, a multilayer coating of ZrO2 or SiO2, etc. If the first coating is outermost from the substrate then only the first coating will be excavated by the infrared laser beam. If the second coating is outermost from the substrate then both the first and second coatings will be excavated by the infrared laser beam.
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