FRONTAL VIEW RECONSTRUCTION FOR IRIS RECOGNITION

• US 20140355841A1
• Filed: 06/04/2013
• Published: 12/04/2014
• Est. Priority Date: 06/04/2013
• Status: Active Grant

• Current Assignee: UT-Battelle LLC
• Original Assignee: UT-Battelle LLC
• Inventors: Santos-Villalobos, Hector J., Bolme, David S., Boehnen, Chris Bensing
• Granted Patent: US 8,958,608 B2
• Time in Patent Office: Days
• US Class Current: 382/117
• CPC Class Codes: G06V 40/193 Preprocessing; Feature extraction

Abstract

Iris recognition can be accomplished for a wide variety of eye images by correcting input images with an off-angle gaze. A variety of techniques, from limbus modeling, corneal refraction modeling, optical flows, and genetic algorithms can be used. A variety of techniques, including aspherical eye modeling, corneal refraction modeling, ray tracing, and the like can be employed. Precomputed transforms can enhance performance for use in commercial applications. With application of the technologies, images with significantly unfavorable gaze angles can be successfully recognized.

Claims

1. A method implemented at least in part by a computer, the method comprising:

receiving an off-angle iris image depicting an iris with an off-angle gaze; and

from the off-angle iris image, reconstructing a frontal view image of the iris;

wherein the reconstructing accounts for limbus effect.

2. One or more computer-readable devices comprising computer-executable instructions causing a computing system to perform the method of claim 1.

3. The method of claim 1 wherein:

the reconstructing is performed as image preprocessing before submission to iris recognition logic.

4. The method of claim 1 wherein:

the reconstructing comprises removing a portion of the off-angle iris image occluded by a limbus due to a frontal view.

5. The method of claim 4 further comprising:

modeling a physical location of the limbus.

6. The method of claim 1 further comprising:

indicating that a portion of the frontal view image of the iris is to be masked from consideration during iris recognition, due to limbus occlusion.

7. The method of claim 1 further comprising:

performing segmentation of the iris, wherein the segmentation is based on modeled occlusion by the limbus.

8. The method of claim 7 further comprising:

unwrapping an image of the iris based on the segmented iris.

9. The method of claim 1 wherein:

the off-angle gaze is more than 30 degrees off-angle away from frontal.

10. The method of claim 1 wherein:

the reconstructing comprises applying a transform to the off-angle iris image.

11. The method of claim 10 wherein:

the transform maps pixels from the off-angle iris image to an image of a frontal view of the iris.

12. The method of claim 10 wherein:

the transform comprises a precomputed transform; and

the method further comprises;

choosing the precomputed transform based on a gaze angle of the off-angle gaze.

13. The method of claim 10 wherein:

the transform comprises a transform computed from modeling anatomy of an eye and is computed via ray tracing.

14. The method of claim 10 wherein:

the transform comprises a transform computed from measured optical flow between pairs of off-angle and frontal iris images.

15. The method of claim 10 wherein:

the transform comprises a transform computed via a genetic algorithm producing a look-up table.

16. The method of claim 10 wherein:

the transform is composed from a mapping between the off-angle iris image and an unrefracted iris.

17. The method of claim 10 wherein:

the transform is composed from a mapping between an unrefracted iris and a reconstructed frontal image.

18. The method of claim 10 wherein:

the transform is based on an aspherical eye model.

19. The method of claim 10 wherein:

the transform models corneal refraction.

20. The method of claim 1 further comprising:

modeling corneal refraction in the frontal view image of the iris.

21. The method of claim 1 wherein:

the reconstructing comprises applying a distortion map based on an angle for the off-angle gaze.

22. The method of claim 21 further comprising:

generating the distortion map based on image pairs of respective irises at off-angle and frontal perspectives.

23. The method of claim 21 further comprising:

generating the distortion map based on a genetic algorithm operating on affine-corrected off-angle images.

24. One or more computer-readable devices comprising computer-executable instructions causing a computing system to perform a method of converting an off-angle iris image to an estimated frontal view iris image, the method comprising:

receiving the off-angle iris image, wherein the off-angle iris image comprises a depiction of an iris having an off-angle gaze;

aligning the depiction of the iris with a location and shape of an eye model;

scaling the depiction of the iris according to the eye model; and

applying a transform to the off-angle iris image, wherein the transform is composed from mappings comprising;

(1) a mapping between the off-angle iris image and an unrefracted iris based on the eye model; and

(2) a mapping between an unrefracted iris and a reconstructed frontal image based on the eye model;

wherein the eye model has an aspherical shape, models effects of limbus occlusion, and models effects of corneal refraction.

25. One or more computer-readable devices comprising computer-executable instructions causing a computing system to perform a method of converting an off-angle iris image to an estimated frontal view iris image, the method comprising:

receiving the off-angle iris image, wherein the off-angle iris image comprises a depiction of an iris observed at an off-angle perspective;

constructing a synthetic iris estimating the observed iris, wherein the constructing is based at least on the off-angle iris image, an estimation of an off angle, and an aspherical eye model modeling effects of limbus occlusion; and

generating an estimated frontal view iris image, wherein the generating comprises observing the synthetic iris with a synthetic camera placed at a frontal view position with respect to the synthetic iris, and modeling effects of corneal refraction.