Efficient method and system for the acquisition of scene imagery and iris imagery using a single sensor

• US 9,280,706 B2
• Filed: 02/16/2012
• Issued: 03/08/2016
• Est. Priority Date: 02/17/2011
• Status: Expired due to Fees

• Current Assignee: EyeLock LLC (VOXX International Corporation)
• Original Assignee: EyeLock LLC (VOXX International Corporation)
• Inventors: Hanna, Keith J.
• Primary Examiner(s): Li, Tracy
• Assistant Examiner(s): Rahman, Mohammad J
• Application Number:
  US13/398,562
• Publication Number:
  US 20120212597A1
• Time in Patent Office: 1,482 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: G06F 3/013 Eye tracking input arrangements G06F3/015 takes precedence
• CPC Class Codes: G06V 40/19 Sensors therefor
• CPC Class Codes: H04N 25/20 for transforming only infrared radiation into image signals
• CPC Class Codes: H04N 25/60 Noise processing, e.g. detecting, correcting, reducing or removing noise
• CPC Class Codes: H04N 25/76 Addressed sensors, e.g. MOS or CMOS sensors
• CPC Class Codes: H04N 5/33 Transforming infrared radiation cameras or camera modules for generating image signals from infrared radiation H04N23/20; circuitry of SSIS for transforming infrared radiation into image signals H04N25/20
• CPC Class Codes: H04N 7/18 Closed-circuit television [CCTV] systems, i.e. systems in which the video signal is not broadcast

Abstract

The present disclosure is directed towards methods and systems for capturing images of an iris and a scene using a single image sensor. An image sensor may capture a view of a scene and a view of an iris in at least one image. An image processing module may apply a level of noise reduction to a first portion of the at least one image to produce an image of the scene. The image processing module may apply a reduced level of noise reduction to a second portion of the at least one image to produce an image of the iris for use in biometric identification.

Claims

1. A method of processing images acquired using a single image sensor, comprising:

acquiring, by an image sensor, a first image of an object of a predetermined size and at a predetermined distance with respect to the image sensor, the first image including a time-invariant signal component corresponding to the object, and a random time-varying signal component introduced by at least one of shot noise, sensor noise or amplifier noise; and

processing the first image according to a selection from a first mode and a second mode, comprising;

if the first mode is selected, processing the first image by retaining signals from the time-invariant and time-varying signal components with spatial frequencies at and below a threshold spatial frequency predetermined for iris recognition, wherein the object comprises an iris, and performing iris matching that detects statistical dependence between the retained signals and signals from an enrolled image; and

if the second mode is selected, processing the first image by reducing at least a portion of the signals from the time-invariant and time-varying signal components with spatial frequencies at or below the threshold spatial frequency.

2. The method of claim 1, wherein if the second mode is selected, processing the first image with a frequency-based signal reduction process.

3. The method of claim 1, further comprising acquiring the first image while illuminating the object with infra-red illumination.

4. The method of claim 1, wherein if the second mode is selected, applying an averaging or median function to the first image.

5. The method of claim 1, wherein the predetermined threshold is the equivalent of 2 line pairs/mm for a modulation transfer function of 60% for the object of the predetermined size and at the predetermined distance with respect to the image sensor.

6. The method of claim 1, further comprising subtracting systematic noise from the first image.

7. The method of claim 1, further comprising reducing ambient noise in the first image.

8. The method of claim 1, further comprising reducing ambient noise from the first image acquired in the presence of infra-red illumination, using ambient noise from another image acquired without infra-red illumination.

9. The method of claim 1, further comprising determining to deactivate an infra-red-cut (IR-cut) filter for the image sensor when acquiring the first image if the first mode is selected, and to activate the IR-cut filter when acquiring the first image if the second mode is selected.

10. The method of claim 1, wherein acquiring the first image comprises activating a plurality of sensor nodes of the image sensor, a first subset of the sensor nodes configured primarily for capturing an image of the iris suitable for biometric identification, a second subset of the sensor nodes configured primarily for capturing a non-iris image.

11. An apparatus for capturing images of an iris and a scene, comprising:

an image sensor,

configured to acquire a first image of an object of a predetermined size and at a predetermined distance with respect to the image sensor, the first image including a time-invariant signal component corresponding to the object, and a random time-varying signal component introduced by at least one of shot noise, sensor noise or amplifier noise; and

an image processing module,

configured to process the first image according to a selection from a first mode and a second mode, the image processing module configured to;

if the first mode is selected and the object comprises an iris, process the first image by retaining signals from the time-invariant and time-varying signal components with spatial frequencies at and below a threshold spatial frequency predetermined for iris recognition, wherein iris matching is performed to detect statistical dependence between the retained signals and signals from an enrolled image, and

if the second mode is selected, process the first image by reducing at least a portion of the signals from the time-invariant and time-varying signal components with spatial frequencies at or below the threshold spatial frequency.

12. The apparatus of claim 11, wherein the image processing module is configured to process the first image with a frequency-based signal reduction process if the second mode is selected.

13. The apparatus of claim 11, further comprising an illuminator configured for illuminating the object with infra-red illumination during acquisition of the first image.

14. The apparatus of claim 11, wherein the image processing module is configured to perform noise reduction comprising application of an averaging or median function to the first image if the second mode is selected.

15. The apparatus of claim 11, wherein the predetermined threshold is the equivalent of 2 line pairs/mm for a modulation transfer function of 60% for the object of the predetermined size and at the predetermined distance with respect to the image sensor.

16. The apparatus of claim 11, wherein the image processing module is configured to subtract systemic noise from the first image.

17. The apparatus of claim 11, wherein the image sensor comprises a Complementary Metal Oxide Semiconductor (CMOS) sensor.

18. The apparatus of claim 11, wherein the image processing module is configured to reduce ambient noise from the first image acquired in the presence of infra-red illumination, using ambient noise from another image acquired without infra-red illumination.

19. The apparatus of claim 11, further comprising an infra-red-cut (IR-cut) filter that is deactivated for the image sensor when acquiring the first image if the first mode is selected, and activated when acquiring the first image if the second mode is selected.

20. The apparatus of claim 11, wherein the image sensor comprises a plurality of sensor nodes, a first subset of the sensor nodes configured primarily for capturing an image of the iris suitable for biometric identification, a second subset of the sensor nodes configured primarily for capturing a non-iris image.

21. A method of processing images acquired using a single image sensor, comprising:

acquiring, by an image sensor having a visible imaging component and an infra-red imaging component, a first image of an object of a predetermined size and at a predetermined distance with respect to the image sensor, the first image including a time-invariant signal component corresponding to the object and acquired by the infra-red imaging component, and a random time-varying signal component introduced by at least one of shot noise, sensor noise or amplifier noise, and acquired by the visible imaging component;

processing the first image according to a selection from a first mode and a second mode, comprising;

if the first mode is selected, processing the first image by retaining signals from the time-invariant and time-varying signal components with spatial frequencies at and below a threshold spatial frequency predetermined for iris recognition, wherein the object comprises an iris, and performing iris matching that detects statistical dependence between the retained signals and signals from an enrolled; and

if the second mode is selected, processing the first image by reducing at least a portion of the signals from the time-invariant and time-varying signal components with spatial frequencies at or below the threshold spatial frequency.

22. The method of claim 21, wherein the first image has a similar signal level in the random time-varying signal component for the first portion and the second portion.