Multispectral biometric sensors

1. A portable electronic device comprising:

a body;

a platen adapted for placement of a purported skin site by an individual and integrated within the body;

an illumination source;

an imaging system; and

a controller interfaced with the illumination source and the imaging system, the controller including:

instructions to illuminate the purported skin site under a plurality of distinct optical conditions during a single illumination session;

instructions to derive a multispectral image of the purported skin site from light received by the imaging system after scattering from the purported skin site for each of multiple of the plurality of distinct optical conditions;

instructions to perform a biometric function using the multispectral image; and

instructions to perform a nonbiometric function with the imaging system.

2. The portable electronic device recited in claim 1 wherein the illumination source comprises a white-light source.

3. The portable electronic device recited in claim 1 wherein the instructions to derive the multispectral image of the purported skin site comprise instructions to derive a plurality of images of different portions of the skin site as the skin site is moved over the platen.

4. The portable electronic device recited in claim 3 wherein the instructions to derive the multispectral image further comprise instructions to generate a composite of the plurality of images of different portions of the skin site.

5. The portable electronic device recited in claim 3 wherein the platen comprises a roller with which a position of the skin site relative to the imaging system is moved.

6. The portable electronic device recited in claim 5 wherein the platen is optically clear.

7. The portable electronic device recited in claim 1 wherein the illumination source comprises a first source disposed to illuminate the platen under total internal reflectance conditions.

8. The portable electronic device recited in claim 7 wherein the instructions to illuminate the purported skin site comprise instructions to illuminate the platen with the first source such that the skin site is illuminated indirectly.

9. The portable electronic device recited in claim 8 wherein:

the illumination source further comprises a second source disposed to illuminate the skin site directly; and

the instructions to illuminate the purported skin site further comprise instructions to illuminate the skin site directly with the second source.

10. The portable electronic device recited in claim 7 further comprising a lightpipe adapted to guide light from the illumination source to the platen.

11. The portable electronic device recited in claim 1 wherein:

the imaging system comprises a color imager configured to provide a plurality of subimages, each subimage corresponding to a different illumination wavelength or range of illumination wavelengths; and

the multispectral image comprises the plurality of subimages.

12. The portable electronic device recited in claim 11 wherein the illumination source comprises a plurality of illumination sources at different wavelengths.

13. The portable electronic device recited in claim 1 wherein the instructions to perform the nonbiometric function comprise instructions to perform a nonbiometric function with both the illumination source and the imaging system.

14. A biometric measurement system comprising:

a platen;

an illumination source;

a light detector; and

a controller interfaced with the illumination source and the light detector, the controller including:

instructions to illuminate a purported skin site of an individual under a plurality of distinct optical conditions during a single illumination session while the purported skin site is moved over the platen;

instructions to derive a multispectral image of the purported skin site from light received by the light detector after scattering from the purported skin site for each of multiple of the plurality of distinct optical conditions while the purported skin site is moved over the platen; and

instructions to perform a biometric function with multispectral image.

15. The biometric measurement system recited in claim 14 wherein the instructions to derive the multispectral image of the purported skin site comprise instructions to generate a composite of a plurality of images derived for different portions of the purported skin site as the purported skin site is moved over the platen.

16. The biometric measurement system recited in claim 14 wherein the platen comprises a roller with which a position of the skin site relative to the light detector is moved.

17. The biometric measurement system recited in claim 16 wherein the platen is optically clear.

18. The biometric system recited in claim 14 wherein:

the illumination source comprises a first source disposed to illuminate the platen under total internal reflectance conditions; and

the instructions to illuminate the purported skin site comprise instructions to illuminate the platen with the first source such that the skin site is illuminated indirectly.

19. The biometric measurement system recited in claim 18 wherein:

the illumination source further comprises a second source disposed to illuminate the skin site directly; and

the instructions to illuminate the purported skin site further comprise instructions to illuminate the skin site directly with the second source.

20. The biometric measurement system recited in claim 14 wherein:

the light detector comprises a color imager configured to provide a plurality of subimages, each subimage corresponding to a different illumination wavelength or range of illumination wavelengths; and

the multispectral image comprises the plurality of subimages.

21. The biometric measurement system recited in claim 20 wherein the illumination source comprises a plurality of illumination sources at different wavelengths.

22. A method of performing a biometric measurement on an individual, the method comprising:

illuminating a purported skin site of the individual under a plurality of distinct optical conditions during a single illumination session while the purported skin site is moved over a platen;

receiving light scattered from the purported skin site separately for each of multiple of the plurality of distinct optical conditions while the purported skin site is moved over the platen to derive a multispectral image of the purported skin site; and

performing a biometric function with the multispectral image.

23. The method recited in claim 22 further comprising generating a composite of a plurality of images derived for different portions of the purported skin site as the purported skin site is moved over the platen to derive the multispectral image.

24. The method recited in claim 22 wherein the purported skin site is moved over the platen by rolling the purported skin site over a roller comprised by the platen.

25. The method recited in claim 22 wherein illuminating the purported skin site comprises illuminating the platen with a first source under total internal reflectance conditions to illuminate the skin site indirectly.

26. The method recited in claim 25 wherein illuminating the purported skin site further comprises illuminating the skin site directly with a second source.

27. The method recited in claim 22 wherein the purported skin site is in contact with the platen.

28. The method recited in claim 22 wherein the purported skin site is not in contact with the platen.