Security device for security document
AssigneeOrell FüSsli Sicherheitsdruck AG
InventorsSylvain Chosson, Dieter Sauter
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Abstract
A security device for verifying an authenticity of a security document comprises an at least partially transparent substrate with a first surface and a second surface. A first pattern is arranged on the first surface. A second pattern is arranged on said second surface. The first and the second pattern each comprise a plurality of pixels with at least three different gray levels visible from a macroscopic perspective. The first and second pattern cover only gray levels in a range between 20% black and 80% black, in particular between 35% black and 65% black. The first pattern is inverted with respect to the second pattern.
Claims15
A security device for verifying an authenticity of a security document, in particular of a banknote, a passport, a document of value, a certificate, or a credit card, the security device comprising:
- an at least partially transparent substrate and with a first surface and a second surface,
- a first pattern arranged on the first surface of the substrate,
- a second pattern arranged on the second surface of the substrate,
- wherein the first pattern on the first surface is arranged fully in register with the second pattern on the second surface,
- wherein the first pattern and the second pattern each comprise a plurality of pixels with at least three different gray levels visible from a macroscopic perspective,
- wherein the first pattern and the second pattern cover only gray levels in a range between 20% black and 80% black,
- wherein the first pattern is inverted with respect to the second pattern, such that a gray level of x % in said first pattern is inverted to a gray level of (100%-x %) in said second pattern.
A method for generating a security device for verifying an authenticity of a security document, in particular of a banknote, a passport, a document of value, a certificate, or a credit card, the method comprising steps of
- providing an at least partially transparent substrate and with a first surface and a second surface,
- providing a first source image with at least three different gray levels,
- modifying a contrast of said first source image to generate a first modified image, wherein the first modified image covers only gray levels in a range between 20% black and 80% black,
- inverting the first modified image for yielding a second modified image, such that a gray level of x % in said first pattern is inverted to a level of (100%-x %) in said second pattern,
- generating a first pattern from said first modified image,
- generating a second pattern from said second modified image,
- applying the first pattern on said first surface of said substrate,
- applying the second pattern on said second surface of said substrate,
- wherein the first pattern on the first surface is arranged fully in register with the second pattern on the second surface.
Dependencies are inferred from the claim text.