Secure documents with hidden signals, and related methods and systems

• US 7,555,139 B2
• Filed: 10/23/2007
• Issued: 06/30/2009
• Est. Priority Date: 05/08/1995
• Status: Expired due to Fees

• Current Assignee: Digimarc Corporation
• Original Assignee: Digimarc Corporation
• Inventors: Rhoads, Geoffrey B., Rodriguez, Tony F.
• Primary Examiner(s): Johns; Andrew W
• Application Number:
  US11/877,518
• Publication Number:
  US 20080130945A1
• Time in Patent Office: 616 Days
• Field of Search: 382/100, 382/135, 382/137, 382/232, 380/54, 380/55, 283/72, 283/85, 283/93, 283/113, 283/901, 283/902, 340/5.86, 713/176, 358/3.28
• US Class Current: 382/100
• CPC Class Codes: G06T 1/0064 Geometric transfor invariant watermarking, e.g. affine transform invariant
• CPC Class Codes: G06T 2201/0052 Embedding of the watermark in the frequency domain
• CPC Class Codes: H04N 1/32144 embedded in the image data, i.e. enclosed or integrated in the image, e.g. watermark, super-imposed logo or stamp
• CPC Class Codes: H04N 1/32203 Spatial or amplitude domain methods H04N1/32309 takes precedence
• CPC Class Codes: H04N 1/32309 in colour image data
• CPC Class Codes: Y10S 283/902 Anti-photocopy

Abstract

A security document comprising artwork including a security pattern, characterized in that the security pattern has the form of a line structure in which lines width or line spacing is adjusted to carry predefined data. The artwork is generated by the modifying at least one color of at least a part of the artwork to embed the security pattern in the artwork. Methods for detecting the security pattern include use of a frequency domain structure to detect the security pattern despite rotation and scaling of the document, use of signal tiling to improve signal detection, and use of statistical analyses to verify detection of the security pattern.

Claims

1. A printed security document, the security document comprising artwork including a security pattern, characterized in that the security pattern has the form of a line structure in which line width and/or line spacing is adjusted to carry predefined data, the artwork is generated by the modifying at least one color of at least a part of the artwork to embed the security pattern in the artwork.

2. The printed security document of claim 1 wherein the security pattern is repeated in blocks across the security document.

3. The printed security document of claim 1 wherein the security pattern includes a pattern in a frequency transform domain that enables reading of the predefined data despite rotation of the security document.

4. The printed security document of claim 1 wherein the security pattern includes a pattern in a frequency transform domain that enables reading of the predefined data despite spatial scaling of the security document.

5. The printed security document of claim 1 wherein the predefined data conveys a device control signal to control reproduction of the printed security document.

6. An article of currency according to claim 1.

7. A method of generating artwork for a security document, the method comprising:

providing a security pattern modulated to carry predefined data; and

modifying width or line spacing of the artwork of the security document according to the security pattern, wherein the artwork is generated by the modifying at least one color of at least a part of the artwork to embed the security pattern in the artwork.

8. The method of claim 7 wherein the security pattern includes a pattern in a frequency transform domain that enables detection of the predefined data despite rotation of the security document.

9. The method of claim 7 wherein the security pattern includes a pattern in a frequency transform domain that enables detection of the predefined data despite spatial scaling of the security document.

10. The method of claim 7 wherein the security pattern is repeated in blocks across the artwork.

11. The method of claim 7 wherein the predefined data signals a device to control reproduction of an image of the security document.

12. The method of claim 7 including:

performing an inverse transform of a frequency domain pattern to produce at least a portion of the security pattern.

13. The method of claim 12 wherein the frequency domain pattern enables detection of the predefined data despite rotation of the security document.

14. A printed document, the document comprising artwork including a security pattern, characterized in that the security pattern has the form of a contour structure in which contours are provided in a manner that modulates at least one color of the artwork to carry predefined data, the artwork is generated by the modifying at least one color of at least a part of the artwork to embed the security pattern in the artwork.

15. In a system that processes visible light scan data acquired from a printed line art document, an improved method of operation including:

utilizing a processor or electronic processing circuitry, analyzing said scan data to detect a control signal steganographically represented by variations in width or placement of lines comprising the line art; and

taking an action in response to detection of the control signal.

16. In a system that processes visible light electronic scan data acquired from a printed line art document, an improved method of operation including:

analyzing said electronic scan data to detect a control signal steganographically represented by variations in width or placement of lines comprising the line art, wherein the analyzing includes transforming the scan data to a complementary signal domain, and detecting a pattern in the transformed data; and

taking an action in response to detection of the control signal.

17. The method of claim 16 in which said transforming generates transform data based on a Fourier transform.

18. A printed currency document, the printed currency document comprising a pattern, the pattern representing or defining a predefined signal, the presence of the predefined signal is not apparent to a human observer of the printed currency document, the predefined signal being determined from the printed currency document by obtaining image data utilizing visible light imaging, the image data corresponding to at least a portion of the printed currency document, transforming the image data to a complementary signal domain to yield transform data, the transforming generates the transform data based on a Fourier transform, and analyzing the transform data to determine the predefined signal.

19. In a system that processes visible light image data corresponding to a printed currency document, a method comprising:

obtaining visible light image data corresponding to at least a portion of a printed currency document;

analyzing using a printer or electronic processor the visible light image data to detect;

i) a plural-bit signal steganographically hidden in the printed currency document through alterations to artwork or a graphic carried by the printed currency document;

or ii) a predefined signal represented or defined by a pattern carried by the printed currency document, the predefined signal being determined from transforming the visible light image data to a complementary signal domain to yield transform data and analyzing the transform data to determine the predefined signal; and

taking an action in response to detection of the;

i) plural-bit signal;

or ii) the predefined signal.

20. The method of claim 19 wherein said act of analyzing comprises analyzing the image data to detect both the plural-bit signal and the predefined signal.

21. The method of claim 20 wherein said act of taking an action is only responsive upon detection of both the plural-bit signal and the predefined signal.

22. The method of claim 19 wherein the presence of the predefined signal is not apparent to a human observer of the printed currency document.

23. A computer readable medium comprising instructions stored thereon or circuitry to perform the method of claim 19.

24. A printed currency document comprising:

i) a plural-bit signal steganographically hidden with alterations to artwork or a graphic carried by the printed currency document, the plural-bit signal being obtained through analysis of visible light image data corresponding to the artwork or graphic; and

ii) a pattern carried by the printed currency document, the pattern representing or defining a predefined signal, the predefined signal being determined from transforming the visible light image data to a complementary signal domain to yield transform data and analyzing the transform data to determine the predefined signal.

25. The printed currency document of claim 24 wherein the presence of the predefined signal is not apparent to a human observer of the printed currency document.