System and method for robust fingerprint acquisition

• US 20070116331A1
• Filed: 11/28/2006
• Published: 05/24/2007
• Est. Priority Date: 06/01/2004
• Status: Active Grant

• Current Assignee: HID Global Corporation (Assa Abloy AB)
• Original Assignee: Lumidigm Incorporated (Assa Abloy AB)
• Inventors: Martin, Ryan, Rowe, Robert
• Granted Patent: US 7,508,965 B2
• Time in Patent Office: Days
• US Class Current: 382/127
• CPC Class Codes: G06V 40/1324 by using geometrical optics, e.g. using prisms G06V40/1312 takes precedence

Abstract

Combined multispectral and total-internal-reflectance biometric imaging systems are disclosed. A platen has multiple facets, at least one of which has a surface adapted for placement of a purported skin site by an individual and another facet may include an optical absorber. An illumination source and an optical arrangement are disposed to illuminate the purported skin site with light from the illumination source along distinct illumination paths, including paths at angles less than the critical angle and paths at angles greater than the critical angle. Both multispectral and total-internal-reflectance illumination are received by an imaging system. The imaging system may include first and second imaging locations adapted to record images from separate illumination paths. The platen may also include non parallel exits facets.

Claims

1. A combined multispectral and total-internal-reflectance biometric system, wherein the combined multispectral and total-internal-reflectance biometric system comprises:

a platen having a plurality of facets, wherein at least one facet comprises a surface target facet;

a first illumination source disposed to illuminate the surface target facet along a first illumination path that encounters the surface target facet at a first angle measured from a normal to the surface facet that is less than a critical angle, the critical angle defining a smallest angle measured from the normal at which light incident on the surface target facet substantially undergoes total-internal-reflectance;

a second illumination source disposed to illuminate the surface target facet along a second illumination path that encounters the surface target facet at a second angle measured from the normal that is greater than the critical angle; and

an imaging system comprising a first imaging location and a second imaging location;

wherein;

the imaging system is disposed to receive light propagated from the first illumination source after scattering at the surface target facet at the first imaging location; and

the imaging system is disposed to receive light propagated from the second illumination source when total-internal-reflectance is substantially frustrated by the presence of the purported skin site on the surface target facet at the second imaging location.

2. The combined multispectral and total-internal-reflectance biometric imaging system recited in claim 1, further comprising a control mechanism configured to illuminate the first illumination source and the second illumination source simultaneously.

3. The combined multispectral and total-internal-reflectance biometric imaging system recited in claim 1, wherein at least one facet of the platen comprises an optical absorber.

4. The combined multispectral and total-internal-reflectance biometric imaging system recited in claim 3, wherein light propagated along the second illumination path substantially undergoes total-internal-reflectance at the surface target facet and encounters the optical absorber.

5. The combined multispectral and total-internal-reflectance biometric imaging system recited in claim 1, wherein the imager is configured to correct for ambient lighting effects by collecting a dark image at a time when the first illumination source and the second illumination source are not illuminated.

6. The combined multispectral and total-internal-reflectance biometric imaging system recited in claim 1, wherein the first illumination source comprises an illumination source selected from the group consisting of:

a plurality of illumination sources, a broad-band illumination source, a plurality of illumination sources of different wavelengths, an illumination source that provides substantially uniform illumination intensity at the surface target, and an illumination source that provides substantially uniform illumination of the surface target.

7. The combined multispectral and total-internal-reflectance biometric imaging system recited in claim 1, wherein the second illumination source comprises an illumination source selected from the group consisting of:

a plurality of illumination sources, a broad-band illumination source, a plurality of illumination sources of different wavelengths, an illumination source that provides substantially uniform illumination intensity at the surface target, and an illumination source that provides substantially uniform illumination of the surface target.

8. The combined multispectral and total-internal-reflectance biometric imaging system recited in claim 1, wherein the imager further comprises at least one first polarizer.

9. The combined multispectral and total-internal-reflectance biometric imaging system recited in claim 8, wherein the first illumination source comprises at least one second polarizer and the axis of the at least one second polarizer is substantially orthogonal to the axis of the at least one first polarizer.

10. The combined multispectral and total-internal-reflectance biometric imaging system recited in claim 8, wherein the first illumination source comprises at least one second polarizer and the axis of the at least one second polarizer is substantially parallel to the axis of the at least one first polarizer.

11. The combined multispectral and total-internal-reflectance biometric imaging system recited in claim 1, wherein light scattered from the surface target from the first illumination path exits the platen through a first exit facet, light scattered from the surface target from the second illumination path exits the platen through a second exit facet, and the first exit facet and the second exit facet are not parallel.

12. The combined multispectral and total-internal-reflectance biometric imaging system recited in claim 1, further comprising a mechanism adapted to move the first illumination source or the second illumination source into a plurality of positions.

13. A combined multispectral and total-internal-reflectance biometric imaging system comprising:

a platen having a plurality of facets, at least one of the facets comprising a surface target facet;

an illumination source;

an optical arrangement disposed to illuminate the purported skin site with light from the illumination source along a plurality of distinct illumination paths, wherein a first illumination path encounters the surface target facet at a first angle measured from a normal to the surface target facet and is less than a critical angle, and a second illumination path encounters the surface target facet at a second angle measured from the normal to the surface target facet and is greater than the critical angle, the critical angle defining a smallest angle measured from the normal at which light incident on the surface target facet substantially undergoes total-internal-reflectance; and

an imaging system disposed to receive light from the surface target facet and comprising a first imaging location and a second imaging location;

wherein;

light propagated from the illumination source along the first illumination path is received by the imaging system at the first imaging location after scattering at the surface target facet; and

light propagated from the illumination source along the second illumination path is received by the imaging system at the second imaging location when total-internal-reflectance is substantially frustrated by the presence of a biometric feature on the surface target facet.

14. The combined multispectral and total-internal-reflectance biometric imaging system recited in claim 13, wherein light propagated from the illumination source along the second illumination encounters at least one facet of the platen that comprises an optical absorber.

15. The combined multispectral and total-internal-reflectance biometric imaging system recited in claim 13, wherein the illumination source comprises a plurality of illumination sources, a first of the illumination sources being disposed to provide light along the first illumination path and a second of the illumination sources being disposed to provide light along the second illumination path.

16. The combined multispectral and total-internal-reflectance biometric imaging system recited in claim 15, wherein at least one of the first and second of the illumination sources is substantially monochromatic.

17. The combined multispectral and total-internal-reflectance biometric imaging system recited in claim 15, wherein at least one of the first and second illumination sources comprises a broad-band illumination source.

18. The combined multispectral and total-internal-reflectance biometric imaging system recited in claim 13, wherein the optical arrangement comprises at least one polarizer.

19. The combined multispectral and total-internal-reflectance biometric imaging system recited in claim 18, wherein the at least one polarizer comprises a polarizer arrangement selected from the group consisting of:

a polarizer arrangement that provides for substantially parallel-polarization imaging by the imaging system; and

a polarizer arrangement that provides for substantially crossed-polarization imaging by the imaging system.

20. The combined multispectral and total-internal-reflectance biometric imaging system recited in claim 13, wherein light from the first illumination path exits the platen through a first exit facet, light from the second illumination path exits the platen through a second exit facet, and the first exit facet and the second exit facet are not parallel.

21. A method of capturing multispectral and total-internal-reflectance biometric images, wherein the method comprises the steps of:

propagating light from an illumination source along a first illumination path and encounters a surface target facet of a platen at a first angle measured from a normal to the surface target facet that is less than the critical angle, the critical angle being defined as the smallest angle measured from the normal at which light incident on the surface target platen is substantially totally reflected;

collecting light propagated from the illumination source along the first illumination path with an imaging system at a first imaging location;

propagating light from an illumination source along a second illumination path that encounters the surface target platen at a second angle measured from the normal to the surface target facet that is greater than then critical angle; and

collecting light propagated from the illumination source along the second illumination path with the imaging system at a second imaging location;

wherein;

light propagated along the first illumination path is collected by the imaging system after scattering by the surface target; and

light propagated along the second illumination path is collected by the imaging system when total-internal-reflectance is frustrated by the presence of a purported skin site at the surface target.

22. The method of capturing multispectral and total-internal-reflectance biometric images as recited in claim 21, wherein the steps propagating light from an illumination source along a first illumination path and propagating light from an illumination source along a second illumination path occur simultaneously.

23. A biometric imaging system, wherein the biometric imaging system comprises:

a platen with a plurality of facets;

an illumination source; and

an imaging system;

wherein;

at least one facet of the platen comprises a surface target adapted to receive a purported skin site;

the imaging system is disposed to receive light scattered from the surface target facet along a first illumination path and a second illumination path;

light scattered from the surface target facet along the first illumination path exits the platen through a first exit facet;

light scattered from the surface target facet along the second illumination path exits the platen through a second exit facet; and

the first exit facet and the second exit facet are not parallel.

24. The combined multispectral and total-internal-reflectance biometric imaging system recited in claim 23, wherein at least one facet of the platen comprising an optical absorber.

25. The combined multispectral and total-internal-reflectance biometric imaging system recited in claim 24, wherein light propagated along the second illumination path substantially undergoes total-internal-reflectance at the surface target facet and encounters the optical absorber.