Automated methods for distinguishing copies from original printed objects

• US 20040263911A1
• Filed: 11/26/2003
• Published: 12/30/2004
• Est. Priority Date: 01/20/1998
• Status: Active Grant

• Current Assignee: Digimarc Corporation
• Original Assignee: Digimarc Corporation
• Inventors: Levy, Kenneth L., Reed, Alastair M., Sharma, Ravi K., Rhoads, Geoffrey B., Brunk, Hugh L., Hannigan, Brett T., Rodriguez, Tony F., Gustafson, Ammon E., Alattar, Osama M.
• Granted Patent: US 8,144,368 B2
• Time in Patent Office: Days
• US Class Current: 358/3.28
• CPC Class Codes: B29C 45/1418 the inserts being deformed or preformed, e.g. by the injection pressure
• CPC Class Codes: B42D 25/29 Securities; Bank notes
• CPC Class Codes: G06T 1/0021 Image watermarking
• CPC Class Codes: G06T 2201/0064 for copy protection or copy management, e.g. CGMS, copy only once, one-time copy
• CPC Class Codes: G06T 2207/30144 Printing quality
• CPC Class Codes: G06T 7/0002 Inspection of images, e.g. flaw detection
• CPC Class Codes: G07D 7/0034 using watermarks
• CPC Class Codes: G07D 7/004 using digital security elements, e.g. information coded on a magnetic thread or strip
• CPC Class Codes: H04N 1/00002 Diagnosis, testing or measuring; Detecting, analysing or monitoring not otherwise provided for error detection, error correction or monitoring in digital computers or digital computer components G06F11/00
• CPC Class Codes: H04N 1/00005 relating to image data
• CPC Class Codes: H04N 1/00037 Detecting, i.e. determining the occurrence of a predetermined state H04N1/00031 takes precedence
• CPC Class Codes: H04N 1/00092 relating to the original or to the reproducing medium, e.g. imperfections or dirt detecting properties of a sheet H04N1/00681
• CPC Class Codes: H04N 1/32149 Methods relating to embedding, encoding, decoding, detection or retrieval operations
• CPC Class Codes: H04N 1/32208 involving changing the magnitude of selected pixels, e.g. overlay of information or super-imposition H04N1/32219, H04N1/32224 take precedence
• CPC Class Codes: H04N 1/32219 involving changing the position of selected pixels, e.g. word shifting, or involving modulating the size of image components, e.g. of characters H04N1/32224 takes precedence
• CPC Class Codes: H04N 1/32261 in binary data H04N1/32256 takes precedence
• CPC Class Codes: H04N 1/32304 Embedding different sets of additional information
• CPC Class Codes: H04N 1/32309 in colour image data
• CPC Class Codes: H04N 2201/3205 of identification information, e.g. name or ID code H04N2201/3209 takes precedence
• CPC Class Codes: H04N 2201/3207 of an address
• CPC Class Codes: H04N 2201/3226 : of identification information or the like, e.g. ID code, index, title, part of an image, reduced-size image
• CPC Class Codes: H04N 2201/3233 : of authentication information, e.g. digital signature, watermark
• CPC Class Codes: H04N 2201/3239 : using a plurality of different authentication information
• 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

This disclosure describes methods for using embedded auxiliary signals in documents for copy detection and other applications. In on application, the auxiliary signal is formed as an array of elements selected from a set of print structures with properties that change differently in response to copy operations. These changes in properties of the print structures that carry the embedded auxiliary signal are automatically detectable. For example, the changes make the embedded auxiliary signal more or less detectable. The extent to which the auxiliary data is detected forms a detection metric used in combination with one or more other metrics to differentiate copies from originals. Examples of sets of properties of the print structures that change differently in response to copy operations include sets of colors (including different types of inks), sets of screens or dot structures that have varying dot gain, sets of structures with different aliasing effects, etc. Robust and fragile watermarks are used in Image Replacement Documents for a variety of applications. Digital watermarks act as on-board mediators in authentication of a variety of printed documents. Finally, digital watermarks are used to help manage quality of the scanners used in imaging systems.

Claims

1. A method for analyzing an image of a printed object to determine whether the printed image is a copy or an original, the method comprising:

determining whether a machine readable auxiliary signal is embedded in the image, wherein the auxiliary signal is embedded at embedding locations using a set of two or more print structures that change in response to a copy operation, the change causing a divergence or convergence of a characteristic of the print structures such that the machine readable signal becomes more or less detectable; and

based on evaluating the machine readable auxiliary signal, determining whether the printed object is a copy or an original.

2. The method of claim 1 wherein the set of print structures include a first color and a second color that change differently in response to a copy operation.

3. The method of claim 2 wherein at least one of the colors corresponds to an ink color that is out of gamut of a printer or scanner.

4. The method of claim 2 wherein a difference in luminance of the two colors changes in response to a copy operation.

5. The method of claim 1 wherein the set of print structures include a first print structure having a first dot gain property and a second print structure having a second dot gain property;

wherein the first print structure is more susceptible to dot gain than the second print structure in response to a copy operation.

6. The method of claim 1 wherein a difference in luminance of the print structures changes in response to a copy operation due to a difference in susceptibility to dot gain of the print structures.

7. The method of claim 1 wherein the set of print structures include a first print structure having a first aliasing property and a second print structure having a second aliasing property;

wherein the first print structure aliases differently than the second print structure.

8. The method of claim 1 wherein the auxiliary signal is embedded by varying continuity of line structures.

9. The method of claim 8 wherein one print structure comprises a line segment in a first color, and another print structure comprises a line segment in another color.

10. The method of claim 9 wherein the line segments of the different colors are arranged by varying between the first and second colors along a printed line.

11. The method of claim 1 wherein the evaluating includes evaluating a frequency domain metric to detect changes in the print structures.

12. The method of claim 11 wherein the frequency domain metric is a radial frequency domain metric.

13. The method of claim 11 wherein the frequency domain metric is used to evaluate changes in color of a print structure.

14. A storage medium on which is stored instructions for performing the method of claim 1.

15. A method for creating an image to be printed on a printed object, the image being used to determine whether the printed image is a copy or an original, the method comprising:

embedding a machine readable auxiliary signal in the image, wherein the auxiliary signal is embedded at embedding locations using a set of two or more print structures that change in response to a copy operation, the change causing a divergence or convergence of a characteristic of the print structures such that the machine readable signal becomes more or less detectable; and

creating a metric to detect the convergence or divergence from an image scanned of a suspect printed object to determine whether the suspect printed object is a copy or an original.

16. A storage medium on which is stored instructions for performing the method of claim 15.

17. A method for analyzing an image of a printed object to determine whether the printed image is a copy or an original, the method comprising:

determining whether a machine readable auxiliary signal is embedded in the image, wherein the auxiliary signal is embedded at embedding locations using a print structure that changes in response to a copy operation, the change causing a divergence or convergence of a characteristic of the print structure such that the machine readable signal becomes more or less detectable, the print structure comprising a color that changes in response to a copy operation; and

based on evaluating the machine readable auxiliary signal, determining whether the printed object is a copy or an original.

18. The method of claim 17 wherein the auxiliary signal is embedded by varying continuity of line structures.

19. A storage medium on which is stored instructions for performing the method of claim 17.

20. A method for creating an image to be printed on a printed object, the image being used to determine whether the printed image is a copy or an original, the method comprising:

embedding a machine readable auxiliary signal in the image, wherein the auxiliary signal is embedded at embedding locations using a print structure that changes in response to a copy operation, the change causing a divergence or convergence of a characteristic of the print structures such that the machine readable signal becomes more or less detectable; and

creating a metric to detect the convergence or divergence from an image scanned of a suspect printed object to determine whether the suspect printed object is a copy or an original.

21. A storage medium on which is stored instructions for performing the method of claim 20.