Pulse-Rate Detection Using a Fingerprint Sensor

• US 20110170750A1
• Filed: 12/13/2010
• Published: 07/14/2011
• Est. Priority Date: 12/11/2009
• Status: Active Grant

• Current Assignee: Sonavation, Inc.
• Original Assignee: Sonovation, Inc.
• Inventors: Schmitt, Rainer M., Irving, Richard, Kropp, Ronald A.
• Granted Patent: US 8,433,110 B2
• Time in Patent Office: Days
• US Class Current: 382/124
• CPC Class Codes: A61B 5/02444 Details of sensor A61B5/02427 takes precedence
• CPC Class Codes: A61B 5/1172 using fingerprinting
• CPC Class Codes: G06V 40/1382 Detecting the live character of the finger, i.e. distinguishing from a fake or cadaver finger

Abstract

Provided is a fingerprint sensor configured for detecting a pulse of a human or other mammal. A time series of fingerprint images is analyzed to identify time-based variations in spatial location and/or pressure from ridges of a finger, where the variations result from time-based variations in the flow of blood. Based on the analysis, a determination is made if the time-based variations are indicative of a pulse in a digit of the person, and if so, a determination is made as to the pulse rate based on the variations. Imaging sensitivity of the digit at the fingerprint sensor is optimized for determination of the pulse. The time series of fingerprint images is also analyzed to determine if there is bulk motion of the digit, in which case pulse rate analysis is temporarily suspended.

Claims

1. A method of biometric sensing comprising:

capturing at a biometric sensing element a time series of impressions of at least a portion of a fingerprint;

receiving at a processor coupled to the biometric sensing element the time series of impressions of the at least the portion of the fingerprint;

detecting in the time series a variation over time in the impressions of the at least the portion of the fingerprint; and

determining a pulse of a mammal associated with the fingerprint based on the variation over time.

2. The method of claim 1, wherein;

the time series of impressions comprises a series of images of the at least the portion of the fingerprint; and

detecting the variation over time in the time series comprises comparing a second image in the time series to a first image in the time series, wherein the first image and the second image are from different times in the time series.

3. The method of claim 2, wherein comparing the second image to the first image yields a data value representative of fluctuations in the at least the portion of the fingerprint from the first image to the second image.

4. The method of claim 2, wherein comparing the second image to the first image comprises subtracting the first image from the second image.

5. The method of claim 2, wherein determining based on the variation over time in the time series the pulse of the mammal comprises:

comparing a second plurality of images from the time series to a first plurality of images from the time series, wherein each respective image from the second plurality is compared to a respective earlier image from the first plurality;

obtaining from the comparing a plurality data values representative of fluctuations in the fingerprint over time; and

analyzing the plurality of data values representative of fluctuations to determine the pulse of the mammal.

6. The method of claim 5, wherein determining based on the variation over time the pulse of the mammal comprises determining a peak in the pulse based on the plurality of data values representative of the fluctuations.

7. The method of claim 6, wherein determining based on the variation over time a pulse of the mammal further comprises:

calculating a pulse based on a time interval between a first peak in the pulse and a second peak in the pulse.

8. The method of claim 1, wherein:

the time series of impressions comprises a series of images of the at least the portion of the fingerprint; and

capturing at the biometric sensing element the time series of impressions of at least a portion of a fingerprint comprises at least one of;

setting at the biometric sensing element an image capture sensitivity substantially higher than an image capture sensitivity used for fingerprint identification; and

setting at the biometric sensing element an image contrast substantially higher than an image contrast used for fingerprint identification.

9. The method of claim 1, further comprising determining that a digit associated with said at least the portion of the fingerprint is, in bulk aspect, substantially stationary relative to the biometric sensing element.

10. The method of claim 9, wherein:

the time series of impressions comprises a series of images of the at least the portion of the fingerprint; and

determining that the digit of the mammal is, in bulk aspect, substantially stationary relative to the biometric sensing element comprises comparison of at least a first image and a second image from the time series.

11. A biometric sensor, comprising:

a biometric sensing element configured to capture a time series of impressions of at least a portion of a fingerprint; and

a processor coupled to the biometric sensing element, the processor configured to;

receive from the biometric sensing element the time series of impressions of the at least the portion of the fingerprint;

detect in the time series a variation over time in the impressions of the at least the portion of the fingerprint; and

determine based on the variation over time a pulse of a mammal associated with the fingerprint.

12. The biometric sensor of claim 11, wherein:

the biometric sensing element is configured to capture a time series of images of the at least the portion of the fingerprint; and

the processor is configured to detect in the time series of images the variation over time by comparing a second image in the time series to a first image in the time series, wherein the first image and the second image are from different times in the time series.

13. The biometric sensor of claim 12, wherein the processor is further configured to compare the second image to the first image to obtain a data value representative of fluctuations in the at least the portion of the fingerprint from the first image to the second image.

14. The biometric sensor of claim 12, wherein the processor is configured to compare the second image to the first image by subtracting the first image from the second image.

15. The biometric sensor of claim 12, wherein the processor is further configured to:

compare a second plurality of images from the time series to a first plurality of images from the time series, wherein each respective image from the second plurality is compared to a respective earlier image from the first plurality;

obtain from the comparing a plurality data values representative of fluctuations in the fingerprint over time; and

analyze the plurality of data values representative of fluctuations to determine the pulse of the mammal.

16. The biometric sensor of claim 15, wherein the processor is further configured to determine a peak in the pulse based on the plurality of data values representative of the fluctuations.

17. The biometric sensor of claim 16, wherein the processor is further configured to calculate a pulse based on a time interval between a first peak in the pulse and a second peak in the pulse.

18. The biometric sensor of claim 11, wherein:

the biometric sensing element is configured to capture a time series of images of the at least the portion of the fingerprint; and

the biometric sensing element and/or the processor are configured for at least one of;

an image capture sensitivity substantially higher than an image capture sensitivity used for fingerprint identification; and

an image contrast substantially higher than an image contrast used for fingerprint identification.

19. The biometric sensor of claim 11, wherein the processor is further configured to determine that a digit associated with said at least the portion of the fingerprint is, in bulk aspect, substantially stationary relative to the biometric sensing element.

20. The biometric sensor of claim 19, wherein:

the biometric sensing element is configured to capture a time series of images of the at least the portion of the fingerprint; and

the processor is configured to determine that the digit of the mammal is, in bulk aspect, substantially stationary relative to the biometric sensing element by comparing at least a first image and a second image from the time series.

21. A computer readable physical storage medium having control logic stored thereon, the control logic comprising machine executable code which when executed by a processor causes the processor to:

receive from a biometric sensing element a time series of impressions of at least a portion of a fingerprint;

detect in the time series a variation over time in the impressions of the at least the portion of the fingerprint; and

determine based on the variation over time a pulse of a mammal associated with the fingerprint.

22. The computer readable physical storage medium of claim 21, further comprising machine executable code which when executed by the processor causes the processor to:

receive from the biometric sensing element a time series of images of the at least the portion of the fingerprint; and

detect the variation over time in the time series by comparing a second image in the time series to a first image in the time series, wherein the first image and the second image are from different times in the time series.

23. The computer readable physical storage medium of claim 22, further comprising machine executable code which when executed by the processor causes the processor to:

compare the second image to the first image to obtain a data value representative of fluctuations in the at least the portion of the fingerprint from the first image to the second image.

24. The computer readable physical storage medium of claim 22, further comprising machine executable code which when executed by the processor causes the processor to:

compare the second image to the first image by subtracting the first image from the second image.

25. The computer readable physical storage medium of claim 22, further comprising machine executable code which when executed by the processor causes the processor to:

compare a second plurality of images from the time series to a first plurality of images from the time series, wherein each respective image from the second plurality is compared to a respective earlier image from the first plurality;

obtain from the comparing a plurality data values representative of fluctuations in the fingerprint over time; and

analyze the plurality of data values representative of fluctuations to determine the pulse of the mammal.

26. The computer readable physical storage medium of claim 25, further comprising machine executable code which when executed by the processor causes the processor to:

determine a peak in the pulse based on the plurality of data values representative of the fluctuations.

27. The computer readable physical storage medium of claim 26, further comprising machine executable code which when executed by the processor causes the processor to:

calculate a pulse based on a time interval between a first peak in the pulse and a second peak in the pulse.

28. The computer readable physical storage medium of claim 21, further comprising machine executable code which when executed by the processor causes the processor to establish in a time series of images of the fingerprint obtained via the biometric sensing element at least one of:

an image capture sensitivity substantially higher than an image capture sensitivity used for fingerprint identification; and

an image contrast substantially higher than an image contrast used for fingerprint identification.

29. The computer readable physical storage medium of claim 21, further comprising machine executable code which when executed by the processor causes the processor to:

determine that a digit associated with the at least the portion of the fingerprint is, in bulk aspect, substantially stationary relative to the biometric sensing element.

30. The computer readable physical storage medium of claim 29, further comprising machine executable code which when executed by the processor causes the processor to:

determine that the digit of the mammal is, in bulk aspect, substantially stationary relative to the biometric sensing element by comparing at least a first image and a second image from a time series of images of the least the portion of the fingerprint received from the biometric sensing element.