Patent ID: 8867782

Claim:
A system for detecting visibly hidden content on a print media, comprising: a print media printed with image content comprising one or more visible colorants; the print media further printed with 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 a substantial spectral absorption just outside the human visible spectrum, and a comparatively much reduced absorption within the human visible spectrum; 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 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; and 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 a bandwidth of at least a portion of the substantial spectral absorption just outside the human visible spectrum of the at least one spectral edge marker material.