SPECTRAL EDGE MARKING FOR STEGANOGRAPHY OR WATERMARKING

• US 20130335783A1
• Filed: 06/19/2012
• Published: 12/19/2013
• Est. Priority Date: 06/19/2012
• Status: Active Grant

• Current Assignee: Eastman Kodak Company
• Original Assignee: Eastman Kodak Company
• Inventors: Kurtz, Andrew F., Schroeder, Kurt M., Rabbani, Majid
• Granted Patent: US 8,947,744 B2
• Time in Patent Office: Days
• US Class Current: 358/3.28
• CPC Class Codes: B42D 25/333 Watermarks
• CPC Class Codes: B42D 25/382 absorbing or reflecting infrared light
• CPC Class Codes: B42D 25/387 absorbing or reflecting ultraviolet light
• CPC Class Codes: G06K 1/121 by printing code marks applying code marks to labels B65C9/46; marking or coding completed packages B65B61/26
• CPC Class Codes: G06K 19/06103 the marking being embedded in a human recognizable image, e.g. a company logo with an embedded two-dimensional code
• CPC Class Codes: G06K 19/0614 the marking being selective to wavelength, e.g. color barcode or barcodes only visible under UV or IR methods or arrangements for sensing record carriers using a selected wavelength, see G06K7/12
• CPC Class Codes: H04N 1/32133 on the same paper sheet, e.g. a facsimile page header
• CPC Class Codes: H04N 2201/327 which are undetectable to the naked eye, e.g. embedded codes
• CPC Class Codes: H04N 2201/3271 Printing or stamping

Abstract

A print media (200) comprises paper or other substrate, on which image content, whether text or images are printed with accompanying hidden data (220). The image content is printed with one or more normal printing process visible colorants (340), while the hidden data (220) is printed with spectral edge markers (320). The spectral edge marker materials (320) have a substantial spectral absorption just outside the human visible spectrum, and only slight visible absorption, which is masked by the visible colorants (340). Although the hidden data is nominally visually imperceptible, an image capture device (250) having a visible spectral response that extends into a spectral region just outside the visible spectrum where the spectral edge marker absorption occurs, can then detect the hidden data.

Claims

1. A print media having visibly hidden content embedded in image content, comprising:

the print media comprising both image content and hidden data;

the image content printed with one or more normal printing process colorants to provide images or text;

the hidden data provided by selective printing of at least one spectral edge marker material onto at least one image region of the print media to provide visually hidden data, where the spectral edge marker material has a substantial spectral absorption just outside the human visible spectrum; and

where the at least one normal printing process colorant is at least 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 normal printing process colorant and the image regions having the at least one selectively printed spectral edge marker material and the at least one normal printing process colorant are color matched;

an image capture device directed at the print media, the 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; 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 at least a portion of the spectral absorption of the at least one spectral edge marker material.

2. The print media of claim 1 wherein color matching of image content printed with the spectral edge markers and normal colorants compared to adjacent image regions printed with only normal colorants is comparable within two Just Noticeable Differences (JNDs).

3. The print media of claim 1 wherein color matching of image content printed with the spectral edge markers and normal printing process colorants compared to an original color specified for that image content when printed with only normal printing process colorants is comparable within two Just Noticeable Differences (JNDs).

4. The print media of claim 1 wherein color changes caused by the visible crosstalk of the spectral edge marker materials into the visible spectrum is substantially masked by the presence of the normal printing process colorants.

5. The print media of claim 4 wherein the normal printing process colorants are visible colorants that have significant visible light absorption but comparatively low optical absorption within at the least a portion of a bandwidth of the spectral edge absorber that has substantial spectral absorption.

6. The print media of claim 4 wherein the optical absorption of the normal printing process colorants that are visible colorants, as denoted by an optical density difference (Δ

D), is less absorbing than the spectral edge marker materials in at least a portion of the spectral region just outside the human visible spectrum, by a density difference Δ

D≧

0.2.

7. The print media of claim 4 wherein the optical absorption of the normal printing process colorants that are visible colorants is no more than half as light absorbing as the spectral edge marker materials in at least a portion of the spectral region just outside the human visible spectrum.

8. The print media of claim 1 wherein the spectral edge marker materials are UV absorbers, IR absorbers, or both, wherein these absorbers are not visibly fluorescing.

9. The print media of claim 8 wherein the UV absorbing spectral edge markers provide significant light absorption within a spectrum spanning 375-425 nm, and the IR absorbing spectral edge markers provide significant light absorption within a spectrum spanning 675-725 nm.

10. The print media of claim 1 wherein the hidden data is steganographic data or watermarking data.

11. The print media of claim 1 wherein the spectral absorption of the spectral edge marker materials, as indicated by an optical density (D), has an optical density D≧

0.5.

12. The print media of claim 1 wherein the hidden data provided with the image content provides a robust watermark.

13. The print media of claim 1 wherein the image content consists of at least one of images, text, colored fields, grey fields, or combinations thereof.

14. A print media having visibly hidden data embedded in image content, comprising:

the print media comprising both image content and hidden data;

the image content printed with one or more normal printing process colorants to provide images or text;

the hidden data provided by selective printing of at least one spectral edge marker material onto at least one image region of the print media to provide visually hidden data, where the spectral edge marker material has a first spectral absorption just outside the human visible spectrum;

the hidden data further provided by selective printing of at least one normal printing process colorant to image regions including those having the at least one spectral edge marker material, such that image regions having only the at least one normal printing process colorant and the image regions having the at least one selectively printed spectral edge marker material and the at least one normal printing process colorant are color matched, and where the at least one normal printing process colorant has both a significant visible light absorption and a second spectral absorption within at the least a portion of a bandwidth of the spectral edge absorber that has substantial spectral absorption;

an image capture device directed at the print media, the 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 at least matched with the first spectral absorption of the at least one spectral edge marker material; and

wherein the difference between the first spectral absorption of the at least one spectral edge marker material and the second spectral absorption of the normal printing process colorant provides a density difference detectable by at least one spectrally distinct color imaging channel of the image capture device having a spectral response inclusive of at least a portion of the spectral absorption of the at least one spectral edge marker material.

15. The print media of claim 14 wherein the density difference provided by the at least one spectral edge marker material and the at least one normal printing process colorant in the spectral region just outside the visible spectrum, as indicated by an optical density difference (Δ

D), has an optical density Δ

D<

0.1.

16. The print media of claim 14 where the hidden data within the image content provides a fragile watermark.

17. The print media of claim 14 wherein the spectral edge marker materials are UV absorbers, IR absorbers, or both, wherein these absorbers are not visibly fluorescing.

18. The print media of claim 14 wherein color matching of image content printed with the spectral edge markers and normal colorants compared to adjacent image regions printed with only normal colorants is comparable within two Just Noticeable Differences (JNDs).

19. The print media of claim 14 wherein color matching of image content printed with the spectral edge markers and normal printing process colorants compared to an original color specified for that image content when printed with only normal printing process colorants is comparable within two Just Noticeable Differences (JNDs).