Template matching of a biometric object

1. A biometric object matching method comprising:

capturing, by an image capturing device, a plurality of images of a single biometric object during a single activation of a biometric sensor associated with the image capturing device, each image comprising a plurality of pixels;

determining a ranking metric value of each image of the plurality of images based on analysis of each individual pixel in at least a subset of the plurality of pixels in each image;

ranking the plurality of images based on the ranking metric value of each image of the plurality of images to determine a highest ranked image and at least one non-highest ranked image;

comparing, in a first matching attempt for the biometric object, the highest ranked image to templates of a plurality of pre-stored biometric object templates, wherein a matching metric is determined for each compared template;

determining whether at least one of the matching metrics exceeds a matching threshold value;

generating a match indicating signal when at least one of the matching metrics exceeds the matching threshold value;

when none of the matching metrics exceed the matching threshold value, comparing, in a further matching attempt for the biometric object, one of the non-highest ranked images to templates of the plurality of templates based on the matching metrics, wherein a further matching metric is determined for each compared template;

determining whether at least one of the further matching metrics exceeds the matching threshold value;

generating the match indicating signal when at least one of the further matching metrics exceeds the matching threshold value; and

when none of the further matching metrics exceed the matching threshold value, comparing, in a yet further matching attempt for the biometric object, another one of the non-highest ranked images to templates of the plurality of templates based on the matching metrics, wherein a yet further matching metric is determined for each compared template.

2. The method of claim 1 wherein the comparison of the yet further matching attempt is further based on the further matching metrics of the further attempt.

3. The method of claim 1 , wherein the further matching attempt comprises:

determining a further matching attempt sub-set of the templates based on the matching metrics; and

comparing the non-highest ranked image to templates of the further matching attempt sub-set only.

4. The method of any of claim 1 , wherein the further matching attempt comprises:

determining an order of the templates based on the matching metrics; and

comparing the non-highest ranked image to the templates in the determined order.

5. The method of any of claim 1 , wherein the first matching attempt comprises:

determining a first matching attempt sub-set of the templates; and

comparing the highest ranked image to templates of the first matching attempt sub-set only.

6. The method of claim 1 , further comprising dynamically adapting the matching threshold value for the further matching attempt based on the matching metric.

7. The method of any of claim 1 , further comprising:

comparing, in an updating attempt for a template of the plurality of pre-stored biometric object templates, a first number—greater than one—of the plurality of images to the template, wherein a matching metric is determined for each of the compared images;

determining whether at least a second number—greater than one and less than, or equal to, the first number—of the matching metrics exceed an updating threshold value;

updating the template based on the plurality of images when at least the second number of the matching metrics exceed the updating threshold value; and

preventing update of the template when less than the second number of the matching metrics exceed the updating threshold value.

8. A computer program product comprising a non-transitory computer readable medium, having thereon a computer program comprising program instructions, the computer program being loadable into a data processing unit and configured to cause execution of the method according to claim 1 , when the computer program is run by the data processing unit.

9. A biometric object matching arrangement comprising a controller configured to cause:

capturing, by an image capturing device, of a plurality of images of a single biometric object during a single activation of a biometric sensor associated with the image capturing device, each image comprising a plurality of pixels;

determination of a ranking metric value of each image of the plurality of images based on analysis of each individual pixel in at least a subset of the plurality of pixels in each image;

ranking of the plurality of images based on the ranking metric value of each image of the plurality of images to determine a highest ranked image and at least one non-highest ranked image;

comparison, in a first matching attempt for the biometric object, of the highest ranked image to templates of a plurality of pre-stored biometric object templates, including determination of a matching metric for each compared template;

determination of whether at least one of the matching metrics exceeds a matching threshold value;

generation of a match indicating signal when at least one of the matching metrics exceeds the matching threshold value;

when none of the matching metrics exceed the matching threshold value, comparison, in a further matching attempt for the biometric object, of one or more of the non-highest ranked images to templates of the plurality of templates based on the matching metrics, including determination of a further matching metric for each compared template;

determination of whether at least one of the further matching metrics exceeds the matching threshold value;

generation of the match indicating signal when at least one of the further matching metrics exceeds the matching threshold value; and

when none of the further matching metrics exceed the matching threshold value, comparison, in a yet further matching attempt for the biometric object, of another one of the non-highest ranked images to templates of the plurality of templates based on the matching metrics, wherein a yet further matching metric is determined for each compared template.

10. The arrangement of claim 9 wherein the controller is configured to cause the further matching attempt by causing:

determination of a further matching attempt sub-set of the templates based on the matching metrics; and

comparison of the non-highest ranked image to templates of the further matching attempt sub-set only.

11. The arrangement of claim 9 , wherein the controller is configured to cause the further matching attempt by causing:

determination of an order of the templates based on the matching metrics; and

comparison of the non-highest ranked image to the templates in the determined order.

12. The arrangement of claim 9 , wherein the controller is configured to cause the first matching attempt by causing:

determination of a first matching attempt sub-set of the templates; and

comparison of the highest ranked image to templates of the first matching attempt sub-set only.

13. The arrangement of claim 9 , wherein the controller is further configured to cause dynamic adaption of the matching threshold value for the further matching attempt based on the matching metric.

14. The arrangement of claim 9 , wherein the controller is further configured to cause:

comparison, in an updating attempt for a template of the plurality of pre-stored biometric object templates, of a first number—greater than one—of the plurality of images to the template, including determination of a matching metric for each of the compared images;

determination of whether at least a second number—greater than one and less than, or equal to, the first number—of the matching metrics exceed an updating threshold value;

update of the template based on the plurality of images when at least the second number of the matching metrics exceed the updating threshold value; and

prevention of update of the template when less than the second number of the matching metrics exceed the updating threshold value.

15. A system for biometric object matching comprising:

a biometric sensor associated with an image capturing device, the image capturing device configured to capture a plurality of images of a single biometric object during a single activation of the biometric sensor, each image comprising a plurality of pixels;

a memory configured to pre-store a plurality of biometric object templates;

circuitry configured to:

determine a ranking metric value of each image of the plurality of images based on analysis of each individual pixel in at least a subset of the plurality of pixels in each image;

rank the plurality of images based on the ranking metric value of each of the plurality of images to determine a highest ranked image and at least one non-highest ranked image;

compare, in a first matching attempt for the biometric object, the highest ranked image to templates of the plurality of templates, including determination of a matching metric for each compared template;

determine whether at least one of the matching metrics exceeds a matching threshold value;

generate a match indicating signal when at least one of the matching metrics exceeds the matching threshold value; and

when none of the matching metrics exceed the matching threshold value, compare, in a further matching attempt for the biometric object, one of the non-highest ranked images to templates of the plurality of templates based on the matching metrics, wherein a further matching metric is determined for each compared template,

determine whether at least one of the further matching metrics exceeds the matching threshold value;

generate the match indicating signal when at least one of the further matching metrics exceeds the matching threshold value; and

when none of the further matching metrics exceed the matching threshold value, comparing, in a yet further matching attempt for the biometric object, another one of the non-highest ranked images to templates of the plurality of templates based on the matching metrics, wherein a yet further matching metric is determined for each compared template; and

an interface for receiving the match indicating signal.