Air/object determination for biometric sensors

• US 9,911,184 B2
• Filed: 10/30/2015
• Issued: 03/06/2018
• Est. Priority Date: 08/31/2014
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Du, Eliza Yingzi, Chen, Ming Yu, Vural, Esra, Chan, Kwokleung, Ganti, Suryaprakash, Schneider, John Keith, Burns, David William
• Primary Examiner(s): BHATNAGAR, ANAND P
• Application Number:
  US14/928,898
• Publication Number:
  US 20160063296A1
• Time in Patent Office: 858 Days
• CPC Class Codes: G06T 5/20 using local operators
• CPC Class Codes: G06V 40/1306 non-optical, e.g. ultrasonic or capacitive sensing
• CPC Class Codes: G06V 40/1347 Preprocessing; Feature extraction
• CPC Class Codes: G06V 40/50 Maintenance of biometric data or enrolment thereof

Abstract

A fingerprint sensing apparatus may include a fingerprint sensor system and a control system capable of receiving fingerprint sensor data from the fingerprint sensor system. The control system may be capable of determining fingerprint sensor data blocks for at least a portion of the fingerprint sensor data and of calculating statistical variance values for fingerprint sensor data corresponding to each of the fingerprint sensor data blocks. The control system may be capable of determining, based at least in part the statistical variance values, whether an object is positioned proximate a portion of the fingerprint sensor system.

Claims

1. A fingerprint sensing apparatus, comprising:

a fingerprint sensor system; and

a control system of configured for;

receiving fingerprint sensor data from the fingerprint sensor system, wherein the fingerprint sensor data are data received from fingerprint sensor pixels of the fingerprint sensor system;

determining fingerprint sensor data blocks for at least a portion of the fingerprint sensor data, wherein the fingerprint sensor data blocks correspond to blocks of fingerprint sensor pixels of the fingerprint sensor system;

calculating characteristics of variability for fingerprint sensor data corresponding to each of the fingerprint sensor data blocks;

determining, according to the characteristics of variability, whether an object is positioned proximate a portion of the fingerprint sensor system, wherein determining whether an object is positioned proximate a portion of the fingerprint sensor system involves determining whether the characteristics of variability are above or below a threshold value; and

determining, according to whether an object is positioned proximate a portion of the fingerprint sensor system, whether to terminate processing of the fingerprint sensor data.

2. The apparatus of claim 1, wherein the control system is of configured for providing an object output signal indicating whether an object is positioned proximate a portion of the fingerprint sensor system.

3. The apparatus of claim 1, wherein the control system is further of configured for determining whether an object that is positioned proximate the portion of the fingerprint sensor system is a stylus.

4. The apparatus of claim 1, wherein the blocks of fingerprint sensor pixels are contiguous.

5. The apparatus of claim 1, wherein the blocks of fingerprint sensor pixels include substantially all fingerprint sensor pixels of the fingerprint sensor system.

6. The apparatus of claim 1, wherein the blocks of fingerprint sensor pixels have at least two different sizes.

7. The apparatus of claim 1, wherein the control system is further of configured for applying one or more filters to the fingerprint sensor data before calculating the characteristics of variability.

8. The apparatus of claim 7, wherein the one or more filters pass a range of spatial frequencies corresponding to fingerprint features.

9. The apparatus of claim 1, wherein the control system is further of configured for determining whether an object is a finger.

10. The apparatus of claim 9, wherein the control system is further of configured for extracting fingerprint features from the fingerprint sensor data if the control system determines that the object is a finger.

11. The apparatus of claim 1, wherein the fingerprint sensor system includes an ultrasonic sensor array.

12. The apparatus of claim 11, wherein the control system is of configured for assessing an acoustic impedance of one or more objects proximate the fingerprint sensor system.

13. The apparatus of claim 12, wherein the control system is of configured for determining whether an object has an acoustic impedance that is within an acoustic impedance range corresponding to that of skin.

14. The apparatus of claim 13, wherein the acoustic impedance range is from 1.3 MRayls to 2.1 MRayls.

15. The apparatus of claim 13, wherein the control system is of configured for determining whether a skin-covered object is a finger or another body part.

16. The apparatus of claim 1, wherein the characteristics of variability are based, at least in part, on a fingerprint sensor signal value or a fingerprint sensor signal gradient.

17. The apparatus of claim 1, wherein the control system is capable of pre-processing the fingerprint sensor data prior to calculating the characteristics of variability.

18. The apparatus of claim 17, wherein the pre-processing involves at least one process selected from a group of processes consisting of filtering, gain compensation, offset adjustment, background subtraction, a de-noise operation, contrast enhancement, scaling, linearization and clipping.

19. The apparatus of claim 17, wherein the pre-processing involves:

identifying malfunctioning sensor pixels, the malfunctioning sensor pixels including at least one of dead sensor pixels or low-performing sensor pixels; and

excluding fingerprint sensor data from the malfunctioning sensor pixels.

20. A fingerprint sensing method, comprising:

receiving fingerprint sensor data from a fingerprint sensor system, wherein the fingerprint sensor data are data received from fingerprint sensor pixels of the fingerprint sensor system;

determining fingerprint sensor data blocks for at least a portion of the fingerprint sensor data wherein the fingerprint sensor data blocks correspond to blocks of fingerprint sensor pixels of the fingerprint sensor system;

calculating characteristics of variability for fingerprint sensor data corresponding to each of the fingerprint sensor data blocks;

determining, according to the characteristics of variability, whether an object is positioned proximate a portion of the fingerprint sensor system, wherein determining whether an object is positioned proximate a portion of the fingerprint sensor system involves determining whether the characteristics of variability are above or below a threshold value; and

determining, according to whether an object is positioned proximate a portion of the fingerprint sensor system, whether to terminate processing of the fingerprint sensor data.

21. The method of claim 20, further comprising determining whether an object is a finger.

22. The method of claim 20, further comprising assessing an acoustic impedance of one or more objects proximate the fingerprint sensor system.

23. A non-transitory medium having software stored thereon, the software including instructions for controlling a fingerprint sensing apparatus to:

receive fingerprint sensor data from a fingerprint sensor system, wherein the fingerprint sensor data are data received from fingerprint sensor pixels of the fingerprint sensor system;

determine fingerprint sensor data blocks for at least a portion of the fingerprint sensor data, wherein the fingerprint sensor data blocks correspond to blocks of fingerprint sensor pixels of the fingerprint sensor system;

calculate characteristics of variability for fingerprint sensor data corresponding to each of the fingerprint sensor data blocks;

determine, according to the characteristics of variability, whether an object is positioned proximate a portion of the fingerprint sensor system, wherein determining whether an object is positioned proximate a portion of the fingerprint sensor system involves determining whether the characteristics of variability are above or below a threshold value; and

determine, according to whether an object is positioned proximate a portion of the fingerprint sensor system, whether to terminate processing of the fingerprint sensor data.

24. The non-transitory medium of claim 23, wherein the software includes instructions for controlling the fingerprint sensing apparatus to assess an acoustic impedance of one or more objects proximate the fingerprint sensor system.

25. A fingerprint sensing apparatus, comprising:

a fingerprint sensor system; and

control means for;

receiving fingerprint sensor data from the fingerprint sensor system, wherein the fingerprint sensor data are data received from fingerprint sensor pixels of the fingerprint sensor system;

determining fingerprint sensor data blocks for at least a portion of the fingerprint sensor data, wherein the fingerprint sensor data blocks correspond to blocks of fingerprint sensor pixels of the fingerprint sensor system;

calculating characteristics of variability for fingerprint sensor data corresponding to each of the fingerprint sensor data blocks;

determining, according to the characteristics of variability, whether an object is positioned proximate a portion of the fingerprint sensor system, wherein determining whether an object is positioned proximate a portion of the fingerprint sensor system involves determining whether the characteristics of variability are above or below a threshold value; and

determining, according to whether an object is positioned proximate a portion of the fingerprint sensor system, whether to terminate processing of the fingerprint sensor data.

26. The apparatus of claim 25, wherein the control means includes means for determining whether an object that is positioned proximate the portion of the fingerprint sensor system is a stylus.

27. The apparatus of claim 25, wherein the blocks of fingerprint sensor pixels are contiguous.