Texture-biometrics sensor

1. A method of performing a biometric function, the method comprising:

illuminating a purported skin site of an individual with illumination light having a plurality of wavelengths, wherein the purported skin site is in contact with a surface;

receiving light scattered from the purported skin site, wherein the light is received substantially in a plane that includes the surface;

using a processor to carry out the steps of:

forming a plurality of images corresponding to different of the plurality of wavelengths from the received light;

generating an image-texture measure from the plurality of images; and

analyzing the generated image-texture measure to perform the biometric function.

2. The method recited in claim 1 wherein the biometric function comprises an antispoofing function and analyzing the generated image-texture measure comprises determining whether the purported skin site comprises living tissue from the generated image-texture measure.

3. The method recited in claim 1 wherein the biometric function comprises an identity function and analyzing the generated image-texture measure comprises determining an identity of the individual from the generated image-texture measure.

4. The method recited in claim 1 wherein the biometric function comprises a demographic or anthropometric function and analyzing the generated image-texture measure comprises estimating a demographic or anthropometric characteristic of the individual from the generated image-texture measure.

5. The method recited in claim 1 wherein:

the surface is a surface of an imaging detector; and

receiving light scattered from the purported skin site comprises receiving light scattered from the purported skin site at the imaging detector.

6. The method recited in claim 1 wherein receiving light scattered from the purported skin site comprises:

translating a pattern of light from the plane to an imaging detector disposed outside the plane without substantial degradation or attenuation of the pattern; and

receiving the translated pattern at the imaging detector.

7. The method recited in claim 1 wherein the illumination light is white light.

8. The method recited in claim wherein

generating the image-texture measure comprises performing a spatial moving-window analysis of each of the plurality of images.

9. The method recited in claim 8 wherein performing the spatial moving-window analysis comprises calculating moving-window Fourier transforms on the plurality of images.

10. The method recited in claim 8 wherein performing the spatial moving-window analysis comprises calculating a moving-window centrality measure and a moving-window variability measure of the plurality of images.

11. The method recited in claim 1 wherein receiving light scattered from the purported skin site comprises receiving light scattered from the purported skin site at a monochromatic imaging detector.

12. The method recited in claim 1 wherein receiving light scattered from the purported skin site comprises receiving light scattered from the purported skin site at a color imaging detector.

13. The method recited in claim 1 wherein:

analyzing the generated image-texture measure to perform the biometric function comprises comparing the generated image-texture measure with a reference image-texture measure;

the reference image-texture measure was generated from a reference image formed from light scattered from a reference skin site; and

the purported skin site is substantially different from the reference skin site.

14. The method recited in claim 1 further comprising:

comparing spectral features of the received light with reference spectral features in performing the biometric function.

15. A biometric sensor comprising:

a surface adapted for contact with a purported skin site of an individual;

an illumination subsystem disposed to illuminate the purported skin site with illumination light having a plurality of wavelengths when the purported skin site is in contact with the surface;

a detection subsystem disposed to receive light scattered from the purported skin site, wherein the light is received substantially in a plane that includes the surface; and

a computational unit interfaced with the detection subsystem and having:

instructions for forming a plurality of images corresponding to different of the plurality of wavelengths from the received light;

instructions for generating an image-texture measure from the plurality of images; and

instructions for analyzing the generated image-texture measure to perform the biometric function.

16. The biometric sensor recited in claim 15 wherein:

the biometric function comprises an antispoofing function; and

the instructions for analyzing the generated image-texture measure comprise instructions for determining whether the purported skin site comprises living tissue from the generated image-texture measure.

17. The biometric sensor recited in claim 15 wherein:

the biometric function comprises an identity function; and

the instructions for analyzing the generated image-texture measure comprise instructions for determining an identity of the individual from the generated image-texture measure.

18. The biometric sensor recited in claim 15 wherein:

the biometric function comprises a demographic or anthropometric function; and

the instructions for analyzing the generated image-texture measure comprise instructions for estimating a demographic or anthropometric characteristic of the individual from the generated image-texture measure.

19. The biometric sensor recited in claim 15 further comprising an imaging detector, wherein:

the surface is a surface of the imaging detector; and

the detection subsystem comprises the imaging detector and is configured to receive light scattered from the purported skin site at the imaging detector.

20. The biometric sensor recited in claim 15 further comprising:

an imaging detector disposed outside the plane; and

an optical arrangement configured to translate a pattern of light from the plane to the imaging detector without substantial degradation or attenuation of the pattern,

wherein the detection subsystem comprises the imaging detector and is configured to receive the translated pattern at the imaging detector.

21. The biometric sensor recited in claim 15 wherein the illumination subsystem is configured to illuminate the purported skin site with white light.

22. The biometric sensor recited in claim 15 wherein

the instructions for generating the image-texture measure comprise instructions for performing a spatial moving-window analysis of each of the plurality of images.

23. The biometric sensor recited in claim 22 wherein the instructions for performing the spatial moving-window analysis comprise instructions for calculating moving-window Fourier transforms on the plurality of images.

24. The biometric sensor recited in claim 22 wherein the instructions for performing the spatial moving-window analysis comprise instructions for calculating a moving-window centrality measure and a moving-window variability measure of the plurality of images.

25. The biometric sensor recited in claim 15 wherein the detection subsystem comprises a monochromatic imaging detector and is configured to the light scattered from the purported skin site at the monochromatic imaging detector.

26. The biometric sensor recited in claim 15 wherein the detection subsystem comprises a color imaging detector and is configured to the light scattered from the purported skin site at the color imaging detector.

27. The biometric sensor recited in claim 15 wherein

the instructions for analyzing the generated image-texture measure to perform the biometric function comprise instructions for comparing the generated image-texture measure with a reference image-texture measure;

the reference image-texture measure was generated from a reference image formed from light scattered from a reference skin site; and

the purported skin site is substantially different from the reference skin site.

28. The biometric sensor recited in claim 15 wherein the computational unit further has instructions for comparing spectral features of the received light with reference spectral features in performing the biometric function.