Method and apparatus for providing strobed image capture

• US 7,542,628 B2
• Filed: 01/19/2006
• Issued: 06/02/2009
• Est. Priority Date: 04/11/2005
• Status: Active Grant

• Current Assignee: Princeton Identity Inc.
• Original Assignee: Sarnoff Corporation (SRI International, Inc.)
• Inventors: Naroditsky, Oleg, Tinker, Michael, Lolacono, Dominick, Matey, James R., Zappia, Thomas
• Primary Examiner(s): Do; Anh Hong
• Application Number:
  US11/334,968
• Publication Number:
  US 20060245623A1
• Time in Patent Office: 1,230 Days
• Field of Search: 382/312, 382/313, 382/318, 382/321, 382/118, 378/108, 378/116, 351/221
• US Class Current: 382/312
• CPC Class Codes: A61B 3/112 for measuring diameter of pupils
• CPC Class Codes: A61B 5/1171 based on the shapes or appearances of their bodies or parts thereof
• CPC Class Codes: G06V 10/141 Control of illumination
• CPC Class Codes: G06V 40/19 Sensors therefor

Abstract

A method and apparatus for strobed image capture includes stroboscopic illumination synchronized with one or more cameras to improve a signal to noise ratio, reduce motion blur and avoid object damage in sensor systems used to analyze illumination sensitive objects.

Claims

1. A method for providing strobed image capture, comprising:

controlling, with a controller, at least one strobed illumination source to limit an amount of radiation from the illumination source that is applied to an illumination sensitive object;

synchronizing, with the controller, at least one camera with the strobed illumination source; and

capturing at least one image of the illumination sensitive object with the at least one camera, the object being illuminated at least in part by a plurality of photons from the strobed illumination source;

wherein the illumination sensitive object is an iris; and

wherein a light intensity of the strobed illumination source is increased during a strobe, while an average irradiance of the strobed illumination source remains below a safety threshold.

2. The method of claim 1, wherein a subject having the iris is moving.

3. The method of claim 1 further comprising processing the at least one image with a processor to identify a subject.

4. The method of claim 1 further comprising processing the at least one image with a processor to provide pupillometry.

5. The method of claim 1 wherein the controlling step further comprises:

controlling, with the controller, a second illumination source that continuously illuminates the illumination sensitive object.

6. The method of claim 1 wherein the at least one image is a video stream.

7. The method of claim 1, wherein the at least one image of the iris is suitable for biometric purposes.

8. The method of claim 3 wherein the biometric purpose is at least one of iris recognition or pupillometry.

9. The method of claim 1, wherein a processor controls the strobed illumination source and an eye finder provides a plurality of iris images.

10. A system for providing strobed image capture, comprising:

at least one camera

at least one illumination controller for synchronizing with the at least one camera at least one illumination source for illuminating an illumination sensitive object with a plurality of photons;

wherein the at least one camera captures at least one image of the illumination sensitive object at least in part from the plurality of photons reflected from the illumination sensitive object;

wherein the illumination sensitive object is an iris; and

wherein a light intensity of the strobed illumination source is increased during a strobe, while an average irradiance of the strobed illumination source remains below a safety threshold.

11. The system of claim 10, wherein a subject having the iris is moving.

12. The system of claim 10, wherein the at least one image is suitable for biometric purposes.

13. The system of claim 10 further comprising processing the at least one image to identify a subject.

14. The system of claim 10 further comprising processing the at least one image to provide pupillometry.

15. The system of claim 10 wherein the controlling step further comprises:

controlling a second illumination source that continuously illuminates the illumination sensitive object.

16. The system of claim 10 wherein the at least one image is a video stream.

17. An apparatus for performing iris recognition, comprising:

at least one camera arranged to define an image capture volume and configured to capture a plurality of images of a subject moving through the image capture volume, wherein at least one of the plurality of images contains at least a portion of an iris;

an illumination source;

a controller coupled to the illumination source and the at least one camera, the controller configured to provide illumination of the subject during operation of the at least one camera; and

a processor for processing at least one of the plurality of images containing at least a portion of an iris to perform iris recognition;

wherein the controller is configured to strobe the illumination source; and

wherein the controller is configured to strobe the illumination source for a series of short pulses over a period of time having an intensity that is greater than a threshold limit value for a continuous wave output of the illumination source over the period of time.

18. The apparatus of claim 17, further comprising a plurality of cameras arranged to define the image capture volume and configured to capture a plurality of images of the subject moving through the image capture volume.

19. The apparatus of claim 18, wherein the plurality of cameras are configured to synchronously capture the plurality of images of the subject.

20. The apparatus of claim 18, wherein the plurality of cameras are configured to capture the plurality of images of the subject substantially simultaneously.

21. The apparatus of claim 17, wherein the controller is configured to strobe the illumination source in synchronization with shuttering of the at least one camera.

22. The apparatus of claim 17, wherein the illumination source creates illumination that does not damage the subject.

23. The apparatus of claim 17, wherein an illumination level provided by the source generates sufficient reflected photons from the subject moving through the image capture volume captured by the at least one camera o produce an iris image suitable for iris biometric analysis when a distance between the at least one camera and the subject is large.

24. The apparatus of claim 17, wherein at least part of the plurality of images of the subject is provided by the at least one camera in the form of a video stream.

25. The apparatus of claim 17, wherein the image capture volume is greater than about 22.5 cm³.

26. The apparatus of claim 17, wherein the plurality of images of the subject are captured by the at least one camera without stopping the subject.

27. The apparatus of claim 17, wherein the image capture volume is configured to allow movement of the subject.

28. A method of performing iris recognition from at least one image, comprising:

capturing, with at least one camera, a plurality of images of a subject moving through an image capture volume, at least one of the plurality of images containing at least a portion of an iris;

synchronizing, with a controller, illumination from an illumination source with the operation of the at least one camera, wherein an illumination level provided by the illumination source generates sufficient reflected photons from the subject moving through the image capture volume captured by the at least one camera to produce a clear iris image while using a large distance between the at least one camera and the subject;

processing, with a processor, at least one of the plurality of images containing at least a portion of an iris to perform iris recognition; and

strobing, with the controller, the illumination provided by the illumination source;

wherein a light intensity of the illumination source is increased during a strobe, while an average irradiance of the illumination source remains below a safety threshold.

29. The method of claim 28, further comprising:

strobing, with the controller, the illumination source for a series of short pulses over a period of time having an intensity that is greater than a threshold limit value for a continuous wave output of the illumination source over the period of time.

30. The method of claim 28, wherein the illumination source creates illumination that does not damage the subject.

31. The method of claim 28, further comprising:

controlling the illumination source to limit an amount of radiation from the illumination source that is applied to an illumination sensitive object.

32. The method of claim 28, wherein an illumination level provided by the source generates sufficient reflected photons from the subject moving through the image capture volume captured by the at least one camera to produce an iris image suitable for iris biometric analysis when a distance between the at least one camera and the subject is large.

33. The method of claim 28, wherein the plurality of images is a video stream.