Method and apparatus for comparing document features using texture analysis

• US 7,920,714 B2
• Filed: 07/31/2006
• Issued: 04/05/2011
• Est. Priority Date: 07/31/2006
• Status: Expired due to Fees

• Current Assignee: Canadian Bank Note Company, Limited
• Original Assignee: Canadian Bank Note Company, Limited
• Inventors: O'Neil, David Giles
• Primary Examiner(s): Lu; Tom Y
• Application Number:
  US11/496,166
• Publication Number:
  US 20080030798A1
• Time in Patent Office: 1,709 Days
• Field of Search: 382/100, 382/135, 382/141, 382/209, 382/210
• US Class Current: 382/100
• CPC Class Codes: G07D 7/2016 using feature extraction, e.g. segmentation, edge detection or Hough-transformation
• CPC Class Codes: G07D 7/206 Matching template patterns

Abstract

Systems and methods for assisting in the determination of the authenticity of security documents based on known characteristics of similar but authentic security documents. The system and methods use digital processing to capture a digital image of the document being examined and they use a feature localization or detection technique to search for a specific feature in the document based on a stored image of a similar feature from an authentic document. Once the feature on the subject document has been found, the digital image of the localized feature is transformed, by applying mathematical transforms or other image/mathematical operators, such that the result will have distinguishing characteristics that can be derived or analyzed. When the distinguishing characteristics have been analyzed, these are then compared to the stored distinguishing characteristics of similar features from known authentic documents. Based on the comparison, a score is then generated that is indicative of how similar or how different the distinguishing characteristics of the feature being examined are from the features from known authentic documents. The system may also be used such that multiple features from a single document are assessed and scored separately from one another with a final aggregate or weighted score being provided to the user for the whole document.

Claims

1. In a document comparison system having a document reader communicating with a document inspection engine and configured for assessing whether a document read by the document reader is authentic, a method of analyzing a texture feature of the document for comparison with an expected texture feature characteristic of a predetermined printing method used to manufacture the document, the method comprising:

a) obtaining a digital image of at least a portion of the document comprising a texture feature which is characteristic of the predetermined printing method used to manufacture the document;

b) obtaining data for the document from an analysis of the texture feature of the digital image;

c) comparing the data for the document obtained in step b) with expected data for the expected texture feature; and

,

d) generating a score based on a comparison between the obtained data for the document and the expected data;

whereby the score is useful to assess whether the document is authentic by indicating whether the document was manufactured by the predetermined printing method.

2. A method according to claim 1 whereby the predetermined printing method comprises inkjet printing.

3. A method according to claim 1 whereby the texture feature is printed matter.

4. A method according to claim 3 whereby the predetermined printing method is intaglio printing and step a) comprises obtaining a first digital image of the at least one portion of the document when it is directionally illuminated at 90 degrees and obtaining a second digital image of the at least one portion of the document when it is directionally illuminated at an angle other than 90 degrees.

5. A method according to claim 4 whereby step b) comprises generating histograms for the first and second digital images.

6. A method according to claim 1 comprising applying a normalized cross-correlation between the obtained digital image of the texture feature of the document and a digital image of the expected texture feature.

7. A method according to claim 5 whereby the texture feature of the obtained digital image is isolated by applying normalized cross-correlation.

8. A method according to claim 6 comprising applying an edge tracking process to the texture feature of the obtained digital image.

9. A method according to claim 3 whereby the obtained data for the document comprises direction and contour changes of one or more portions of the printed matter of the texture feature of the obtained digital image.

10. A method according to claim 9 whereby the obtained data for the document and the expected data comprise histograms.

11. Non-transitory computer readable media having embodied thereon computer instructions for executing a method of analyzing a texture feature of a document for comparison with an expected texture feature characteristic of a predetermined printing method used to manufacture the document, the method comprising:

a) obtaining a digital image of at least a portion of the document comprising a texture feature which is characteristic of the predetermined printing method used to manufacture the document;

b) obtaining data for the document from an analysis of the texture feature of the digital image;

c) comparing the data for the document obtained in step b) with expected data for the expected texture feature; and

,

d) generating a score based on a comparison between the obtained data for the document and the expected data;

whereby the score is useful to assess whether the document is authentic by indicating whether the document was manufactured by the predetermined printing method.

12. Non-transitory computer readable media according to claim 11 whereby the predetermined printing method comprises inkjet printing.

13. Non-transitory computer readable media according to claim 11 whereby the texture feature is printed matter.

14. Non-transitory computer readable media according to claim 13 whereby the predetermined printing method is intaglio printing and step a) comprises obtaining a first digital image of the at least one portion of the document when it is directionally illuminated at 90 degrees and obtaining a second digital image of the at least one portion of the document when it is directionally illuminated at an angle other than 90 degrees.

15. Non-transitory computer readable media according to claim 14 whereby step b) comprises generating histograms for the first and second digital images.

16. Non-transitory computer readable media according to claim 11 comprising applying a normalized cross-correlation between the obtained digital image of the texture feature of the document and a digital image of the expected texture.

17. Non-transitory computer readable media according to claim 16 whereby the texture feature of the obtained digital image is isolated by applying normalized cross-correlation.

18. Non-transitory computer readable media according to claim 17 comprising applying an edge tracking process to the texture feature of the obtained digital image.

19. Non-transitory computer readable media according to claim 13 whereby the obtained data for the document comprises direction and contour changes of one or more portions of the printed matter of the texture feature of the obtained digital image.

20. Non-transitory computer readable media according to claim 19 whereby the obtained data for the document and the expected data comprise histograms.