Self-Calibration

• US 20100161529A1
• Filed: 12/18/2009
• Published: 06/24/2010
• Est. Priority Date: 12/19/2008
• Status: Active Grant

• Current Assignee: Ingenia Holdings Limited
• Original Assignee: Ingenia Holdings Limited
• Inventors: Cowburn, Russell Paul
• Granted Patent: US 8,615,475 B2
• Time in Patent Office: Days
• US Class Current: 706/12
• CPC Class Codes: G07D 7/2033 Matching unique patterns, i.e. patterns that are unique to each individual paper

Abstract

Mitigation of processing artefacts caused by surfaces with high contrast printing or colouring transitions within a system to compare signatures derived from inherent physical surface properties of different articles to authenticate or validate articles and within a system to generate signatures from inherent physical surface properties of different articles.

Claims

1. A method of performing a comparison between fuzzy data signatures, the method comprising:

performing a cross-comparison between a test signature and each of a plurality of record signatures; and

determining whether the test signature matches one of the plurality of record signatures using a self-calibrating method which utilises a measure of the randomness of each signature bit.

2. The method of claim 1, wherein the measure of the randomness is derived from a comparison between a best putative match candidate of the record signatures and one or more further putative match candidates of the record signatures.

3. The method of claim 2, wherein the comparison comprises performing a sliding cross-correlation of each of the one or more further putative match candidates against the best putative match candidate to determine a best correlation location, and wherein the measure of the randomness is derived by determining the number of times that the bit value of each bit of the best putative match candidate is the same as the bit value at the same bit position in each of the one or more further putative match candidates at the best correlation location.

4. The method claim 2, wherein the method further comprises using the measure of randomness to determine a confidence result as to whether the best putative match signature is or is not derived from the same article as the test signature.

5. The method of claim 1 wherein each signature is generated from an article by a method comprising:

sequentially directing a coherent beam onto each of a plurality of different regions of the article;

collecting a set comprising groups of data points from signals obtained when the coherent beam scatters from the different regions of the article, wherein different ones of the groups of data points relate to scatter from the respective different regions of the article; and

determining a signature for the article from the set of groups of data points.

6. The method of claim 5, wherein the determining comprises:

capping the magnitude of large magnitude intensity signal transitions; and

using the capped magnitude data to determine the signature.

7. The method of claim 6, wherein the capping comprises identifying large magnitude transitions and limiting the magnitude of the transition.

8. The method of claim 6, wherein the capping comprises:

differentiating the intensity data;

selecting a differential value at a low percentile;

scaling the selected value to determine a threshold;

setting all differentials with a value greater than the threshold to zero; and

reintegrating the modified differentials.

9. A method of generating a signature for an article, the method comprising:

sequentially directing a coherent beam onto each of a plurality of different regions of the article;

collecting a set comprising groups of data points from signals obtained when the coherent beam scatters from the different regions of the article, wherein different ones of the groups of data points relate to scatter from the respective different regions of the article; and

determining a signature for the article from the set of groups of data points, the determining comprising capping the magnitude of large magnitude intensity signal transitions and using the capped magnitude data for determining the signature.

10. The method of claim 9, wherein the capping comprises identifying large magnitude transitions and limiting the magnitude of the transition.

11. The method of claim 9, wherein the capping comprises:

differentiating the intensity data;

selecting a differential value at a low percentile;

scaling the selected value to determine a threshold;

setting all differentials with a value greater than the threshold to zero; and

reintegrating the modified differentials.

12. Apparatus operable to perform a comparison between fuzzy data signatures, the apparatus comprising:

a cross-comparison unit configured to perform a comparison between a test signature and each of a plurality of record signatures; and

a determining unit configured to determine whether the test signature matches one of the plurality of record signatures using a self calibrating approach by utilising a measure of the randomness of each signature bit to perform the determination.

13. The apparatus of claim 12, wherein the determining unit is operable to derive the measure of the randomness is from a comparison between a best putative match candidate of the record signatures and one or more further putative match candidates of the record signatures.

14. The apparatus of claim 13, wherein the determining unit is operable to carry out the comparison by performing a sliding cross-correlation of each of the one or more further putative match candidates against the best putative match candidate to determine a best correlation location, and to derive the measure of the randomness by determining the number of times that the bit value of each bit of the best putative match candidate is the same as the bit value at the same bit position in each of the one or more further putative match candidates at the best correlation location.

15. The apparatus of claim 13, wherein the determining unit is operable to further use the measure of randomness to determine a confidence result as to whether the best putative match signature is or is not derived from the same article as the test signature.

16. The apparatus of claim 12, further comprising a signature generator operable to generate the test signature from an article, the signature generator comprising:

a source operable to sequentially direct a coherent beam onto each of a plurality of different regions of the article;

a detector operable to collect a set comprising groups of data points from signals obtained when the coherent beam scatters from the different regions of the article, wherein different ones of the groups of data points relate to scatter from the respective different regions of the article; and

a determiner operable to determine a signature for the article from the set of groups of data points.

17. The apparatus of claim 16, wherein the determiner is operable to:

cap the magnitude of large magnitude intensity signal transitions; and

use the capped magnitude data to determine the signature.

18. The apparatus of claim 17, wherein the determiner is operable to cap the magnitude of large magnitude intensity signal transitions by identifying large magnitude transitions and limiting the magnitude of the transition.

19. The apparatus of claim 17 wherein the determiner is operable to cap the magnitude of large magnitude intensity signal transitions by:

differentiating the intensity data;

selecting a differential value at a low percentile;

scaling the selected value to determine a threshold;

setting all differentials with a value greater than the threshold to zero; and

reintegrating the modified differentials.

20. Apparatus for generating a signature for an article, the apparatus comprising:

a source operable to sequentially direct a coherent beam onto each of a plurality of different regions of the article;

a detector operable to collect a set comprising groups of data points from signals obtained when the coherent beam scatters from the different regions of the article, wherein different ones of the groups of data points relate to scatter from the respective different regions of the article; and

a determiner operable to determine a signature for the article from the set of groups of data points, the determiner operable to cap the magnitude of large magnitude intensity signal transitions and to use the capped magnitude data for determining the signature.

21. The apparatus of claim 20, wherein the determiner is operable to cap the magnitude of large magnitude intensity signal transitions by identifying large magnitude transitions and limiting the magnitude of the transition.

22. The apparatus of claim 20, wherein the determiner is operable to cap the magnitude of large magnitude intensity signal transitions by:

differentiating the intensity data;

selecting a differential value at a low percentile;

scaling the selected value to determine a threshold;

setting all differentials with a value greater than the threshold to zero; and

reintegrating the modified differentials.