Method and system for fingerprint image enhancement
The present disclosure relates a method for fingerprint image enhancement comprising applying a first low pass filter and a first weight to raw fingerprint image data to produce a first filtered fingerprint image data set. Applying a second low pass filter and a second weight to the raw fingerprint image data to produce a second filtered fingerprint image data set. Filter coefficients of the second filter are different from filter coefficients of the first filter. The first filtered fingerprint image data set and the second filtered fingerprint image data set are combined to produce a final enhanced fingerprint image. The disclosure also relates to a fingerprint sensing system and to an electronic device comprising a fingerprint sensing system.
1. A method for fingerprint image enhancement, the method comprising:
retrieving raw fingerprint image data captured by a fingerprint sensor device;
applying a first two-dimensional low pass filter and a first weight to the raw fingerprint image data to produce a first filtered fingerprint image data set, the first two-dimensional low pass filter comprising at least one set of filter coefficients,
applying a second two-dimensional low pass filter and a second weight to the raw fingerprint image data to produce a second filtered fingerprint image data set, the second two-dimensional low pass filter comprising at least one set of filter coefficients, wherein the set of filter coefficients of the second filter is different from the set of filter coefficients of the first filter,
combining the first filtered fingerprint image data set and the second filtered fingerprint image data set to produce a final enhanced fingerprint image.
2. The method according to claim 1 , wherein the first weight is different from the second weight.
3. The method according to claim 1 , comprising:
applying a plurality of two-dimensional low pass filters and weights to the raw fingerprint image data to produce a plurality of filtered fingerprint image data sets, wherein the plurality of filtered fingerprint data sets are combined to produce the final enhanced fingerprint image.
4. The method according to claim 1 , comprising:
iteratively producing an updated final enhanced fingerprint image by repeating, for a multiple number of iterations, the applying of two-dimensional low pass filters and weights to the final enhanced fingerprint image produced in the respective previous iteration.
5. The method according to claim 4 , wherein at least one of the sets of filter coefficients is varied between two iterations.
6. The method according to claim 4 , wherein at least one of the weights is varied between two iterations.
7. The method according to claim 1 , comprising:
selecting the two-dimensional low pass filter coefficients based on properties of the retrieved fingerprint image data.
8. The method according to claim 1 , comprising:
selecting the weights for the filters based on the retrieved fingerprint image data.
9. The method according to claim 8 , wherein the weights are selected for obtaining the final enhanced fingerprint image with improved sharpness.
10. The method according to claim 1 , wherein each of the two-dimensional low pass filters is a respective Gaussian filter.
11. The method according to claim 10 , wherein standard deviations of the Gaussian filters are different from each other, whereby the filter coefficients for the Gaussian filters are different from each other.
12. A fingerprint sensing system comprising:
a fingerprint sensor device for acquiring fingerprint image data; and
a control unit configured to perform the steps of claim 1 .
13. The fingerprint sensing system according to claim 12 , wherein the fingerprint sensor device is a capacitive fingerprint sensor.
14. An electronic device, comprising:
a fingerprint sensing system according to claim 12 ; wherein the control unit is configured to:
provide an authentication request for a finger to the fingerprint sensing device;
receive an authentication signal from the fingerprint sensing device; and
perform at least one action if the authentication signal indicates authentication success.
15. The electronic device according to claim 14 , wherein the electronic device is a mobile device or a smart card.
16. Computer program product comprising a non-transitory computer readable medium having stored thereon computer program means for controlling an electronic device, the electronic device comprising a fingerprint sensor configured to acquire raw fingerprint image data, and a control unit configured to receive the raw fingerprint image data captured by the fingerprint sensor, wherein the computer program product comprises:
code for applying a first two-dimensional low pass filter and a first weight to the raw fingerprint image data to produce a first filtered fingerprint image data set, the first two-dimensional low pass filter comprising at least one set of filter coefficients;
code for applying a second two-dimensional low pass filter and a second weight to the raw fingerprint image data to produce a second filtered fingerprint image data set, the second two-dimensional low pass filter comprising at least one set of filter coefficients, wherein the set of filter coefficients of the second filter is different from the set of filter coefficients of the first filter, and
code for combining the first filtered fingerprint image data set and the second filtered fingerprint image data set to produce a final enhanced fingerprint image.