Multi-Channel Digital Watermarking

Abstract

The present disclosure relates generally to digital watermarking including watermarking conveyed through multiple channels. One claim recites a method to detect digital watermarks carried in different channels of a physical object. The method comprising: receiving first optically captured image data, the first optically captured image data corresponding to a first channel which is detectable with visible lighting; receiving second optically captured image data, the second optically captured image data corresponding to a second channel with is detectable in a first non-visible spectrum; receiving third optically captured image data, the third optically captured image data corresponding to a third channel with is detectable in a second non-visible spectrum; and using a programmed electronic processor, analyzing the first, second and third optically captured image data to detect watermark components embedded therein. Of course, other claims and combinations are provided too.

1 . An identification document comprising at least one photographic representation of a bearer of the document or indicia printed thereon, said identification document comprising:
 a first digital watermark component conveyed through a first channel, the first channel being visibly perceptible to a human viewer under visible or ambient lighting conditions;   a second digital watermark component conveyed through a second channel, the second channel being substantially non-visible to a human viewer under visible or ambient lighting conditions, but at least a portion of the second channel becomes visible to a human viewer with infrared illumination; and   a third digital watermark component conveyed through a third channel, the third channel being substantially non-visible to a human viewer under visible lighting conditions, but at least a portion of the third channel becomes visible to a human viewer with ultraviolet illumination.   
     
     
         2 . The identification document of  claim 1  in which the first, second and third digital watermark components occupy non-overlapping spatial regions of the identification document. 
     
     
         3 . The identification document of  claim 1  in which at least two of the first, second and third digital watermark components occupy overlapping spatial regions of the identification document. 
     
     
         4 . The identification document of  claim 1  in which the first digital watermark component, the second digital watermark component and the third digital watermark component are intertwined. 
     
     
         5 . The identification document of  claim 1  in which the first digital watermark component comprises a first message, and in which the second digital watermark component and the third digital watermark each comprise at least a portion of the first message. 
     
     
         6 . The identification document of  claim 1  in which the first digital watermark component comprises a first message, and in which at least one of the second digital watermark component and the third digital watermark comprises a cryptographic or reduced-bit representation of the first message. 
     
     
         7 . The identification document of  claim 6  in which the first message is also provided on the identification document via print. 
     
     
         8 . The identification document of  claim 7  in which the print comprises at least one of alphanumeric numbers and machine-readable indicia. 
     
     
         9 . The identification document of  claim 1  in which a first message is distributed across the first digital watermark component, the second digital watermark component and the third digital watermark component. 
     
     
         10 . The identification document of  claim 9  in which each of the first digital watermark component, the second digital watermark component and the third digital watermark component comprises a different portion of the first message. 
     
     
         11 . The identification document of  claim 1  in which the first digital watermark component comprises first elements, the second digital watermark component comprises second elements and the third digital watermark component comprises third elements, with at least some of the first elements, second elements and third elements being spatially interleaved so as to constructively interfere with one another. 
     
     
         12 . The identification document of  claim 3  in which the first digital watermark component comprises first elements, the second digital watermark component comprises second elements and the third digital watermark component comprises third elements, with at least some of the first elements, second elements and third elements being spatially interleaved so as to avoid interfering with one another. 
     
     
         13 . The identification document of  claim 1  in which embedding of at least two of the first digital watermark component, the second digital watermark component and the third digital watermark component makes use of a frequency-domain transformation. 
     
     
         14 . The identification document of  claim 13  in which the embedding of the two components comprises embedding in different frequencies. 
     
     
         15 . The identification document of  claim 1  in which at least one of the first digital watermark component, the second digital watermark component and the third digital watermark component comprises a key to decrypt or decode at least one of the remaining two watermark components. 
     
     
         16 . The identification document of  claim 3  in which the embedding of at least two of the first digital watermark component, the second digital watermark component and the third digital watermark component comprises embedding at different spatial resolutions. 
     
     
         17 . The identification document of  claim 3  in which the first digital watermark component, the second digital watermark component and the third digital watermark component collectively comprise a fragile digital watermark component. 
     
     
         18 . The identification document of  claim 1  in which the first digital watermark component comprises an orientation component, and in which detection of at least one of the second digital watermark component and the third digital watermark component is facilitated via the orientation component. 
     
     
         19 . A method to detect digital watermarks carried in different channels of a physical object, the method comprising:
 receiving first optically captured image data, the first optically captured image data corresponding to a first channel which is detectable with visible lighting;   receiving second optically captured image data, the second optically captured image data corresponding to a second channel with is detectable in a first non-visible spectrum;   receiving third optically captured image data, the third optically captured image data corresponding to a third channel with is detectable in a second non-visible spectrum; and   using a programmed electronic processor, analyzing the first, second and third optically captured image data to detect watermark components embedded therein.   
     
     
         20 . The method of  claim 19  in which the watermarks components are intertwined. 
     
     
         21 . The method of  claim 19  in which the object comprises an identification document. 
     
     
         22 . The method of  claim 19  in which the first non-visible spectrum comprises infrared and the second non-visible spectrum comprises ultraviolet. 
     
     
         23 . An identification document comprising:
 a photographic representation of an authorized bearer of the identification document;   a first channel including a first digital watermark conveyed therein, wherein the first digital watermark is detectable from optical scan data corresponding to at least a portion of the identification document; and   a second channel including a second digital watermark conveyed therein, wherein the second digital watermark only becomes detectable upon stimulation of the identification document through a non-light stimulus.   
     
     
         24 . The identification document of  claim 23  wherein the non-light stimulus comprises at least one of heat, water, chemical agent or electro-magnetic energy. 
     
     
         25 . The identification document of  claim 23  wherein the second channel comprises at least one of thermochromic material, water-fugitive material, chemical-reactive material or magnetic material. 
     
     
         26 . The method of  claim 23  wherein the photographic representation comprises the first channel. 
     
     
         27 . The method of  claim 23  wherein the first digital watermark and the second digital watermark are intertwined.