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US 6,357,800 B1Granted
Document with a moire-generating raster structure
AssigneeGiesecke & Devrient GmbH
InventorsJohann Müller, Stefan May
Life of this patent
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AssigneeGiesecke & Devrient GmbH
InventorsJohann Müller, Stefan May
Estimating the term…
A data carrier with at least one halftone images 10 represented by structural elements 12, whereby a predetermined symmetrical widening of structural elements 12 represents a corresponding gray level of halftone image 10. Image 10 has predetermined areas 14, 16 and 22 each having a predetermined number or screen frequency of structural elements 12, the screen frequency of structural elements 12 per unit area of area 14, 16 and 22 being different between at least two areas 14, 16 and 22 and/or structural elements 12 being offset from each other in at least two areas 14, 16 and 22. A data carrier with such a halftone image 10 acquires a moiré pattern in at least predetermined areas of halftone image 10 when copied, so that a copy of the data carrier is recognizable immediately and with the naked eye (FIG. 1).
A data carrier such as a document of value, with at least one halftone image (10) represented by structural elements (12, 18), each structural element having a basic geometry and a size wherein the size ofthe structural element (12, 18) represents a gray level of the halftone image (10), and wherein the halftone image (10) has contiguous first and second contiguous areas, anumber of structural elements per unit area of said first contiguous areabeing different than a number of structural elements per unit area of said second contiguous area, wherein said number of structural elements per unit area of said first contiguous area equals a screen frequency of said first contiguous area and a number of structural elements per unit area of said second contiguous area equals a screen frequency of said second contiguous area, said screen frequency of the first contiguous area thereby being different than a screen frequency of the second contiguous area.
A method for producing a data carrier, for example a document of value, with at least one halftone image (10) represented by structural elements (12, 18), the structural elements having a basic geometry, and a predetermined size of the structural elements (12, 18) representing a gray level of the halftone image (10), comprising the following steps:
Dependencies are inferred from the claim text.