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US 2002/0054680 A1Published application
Optical watermark
AssigneeTrustcopy Pte Ltd.
InventorsSheng Huang, Jian Kang Wu
Life of this patent
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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.
Claims45
A method for producing a watermark on a document, the method including the step of:
- a) determining a required plural number of watermark layers and a dot patterns for each of the plurality of watermark layers;
- b) selecting at least one latent image object for each of the plural number of watermark layers and embedding each latent image object into its respective watermark layer;
- c) superposing the watermark layers to form the watermark;
- d) defining and generating a decoder for each of the number of watermark layers;
- and
- e) applying the watermark to the document.
3 more elements
A watermark for use on a document, the watermark having:
- a) a required plural number of watermark layers, each of the plural number of watermark layers each being a dot pattern;
- b) at least one latent image object embedded into each watermark layer;
- and
- c) the watermark layers being superposed to form the watermark
1 more element
Dependencies are inferred from the claim text.