Patent ID: 8941886
Filing Date: 2015-01-27
Classification: B42D,C09D,G06K,H04N

Abstract:
1. A method for hiding data in an image having a plurality of pixels to produce print media wherein the hidden data is detectable by an image capture device, but is generally imperceptible to a human observer when the print media is viewed, comprising: printing image content with one or more visible colorants on the print media; printing of at least one spectral edge marker material onto at least one image region of the print media to provide visibly hidden data, wherein the spectral edge marker material has both a substantial spectral absorption just outside the human visible spectrum, and a comparatively much reduced absorption within the human visible spectrum; operating an image capture device having a visible spectral response which includes both red, green, and blue spectrally distinct imaging channels and an overall spectral response including a spectral region just outside the visible spectrum; wherein the at least one visible colorant is printed on the print media in regions that are both overlapping with and adjacent to the image regions having the at least one selectively printed spectral edge marker material, such that image regions having only the at least one visible colorant and the image regions having the at least one selectively printed spectral edge marker material and the at least one visible colorant are color matched; wherein the image capture device detects the at least one spectral edge marker material ink using at least one spectrally distinct color imaging channel having a spectral response inclusive of at least a portion of the spectral absorption of the at least one spectral edge marker material; and wherein the spectral edge marker materials have less density in the visible spectrum than do the one or more visible colorants, as indicated by an optical density difference (ΔD), where ΔD is at least 0.2, and preferably ΔD≧0.3.