Optical watermark
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United States of America Patent
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Apr 29, 2008
Grant Date -
May 9, 2002
app pub date -
Mar 16, 2001
filing date -
Sep 15, 2000
priority date (Note) -
In Force
status (Latency Note)
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Abstract
A multiple-layered watermark is generated to be placed on document, to protect against counterfeiting and forgery. Hidden information embedded into each of the watermark's layers is only detectable by using a corresponding decoder. Because of the multiple-layered structure, it is difficult to reverse engineer the optical watermark. The generalized watermark structure significantly increases the 'key space' of the decoder.
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Family
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Cited Art Landscape
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