Operating a fingerprint sensor comprised of ultrasonic transducers

• US 10,452,887 B2
• Filed: 11/17/2016
• Issued: 10/22/2019
• Est. Priority Date: 05/10/2016
• Status: Active Grant

• Current Assignee: Invensense Incorporated (TDK Corporation)
• Original Assignee: Invensense Incorporated (TDK Corporation)
• Inventors: Salvia, James Christian, Tang, Hao-Yen, Perrott, Michael H., Garlepp, Bruno W., De Foras, Etienne
• Primary Examiner(s): Tucker, Wesley J
• Application Number:
  US15/354,876
• Publication Number:
  US 20170330012A1
• Time in Patent Office: 1,069 Days
• CPC Class Codes: G06F 1/3231 Monitoring the presence, absence or movement of users
• CPC Class Codes: G06F 1/3287 by switching off individual functional units in the computer system
• CPC Class Codes: G06F 3/0436 in which generating transducers and detecting transducers are attached to a single acoustic waves transmission substrate
• CPC Class Codes: G06V 40/1306 non-optical, e.g. ultrasonic or capacitive sensing
• CPC Class Codes: G06V 40/1347 Preprocessing; Feature extraction

Abstract

In a method for operating a fingerprint sensor comprising a plurality of ultrasonic transducers, a first subset of ultrasonic transducers of the fingerprint sensor are activated, the first subset of ultrasonic transducers for detecting interaction between an object and the fingerprint sensor. Subsequent to detecting interaction between an object and the fingerprint sensor, a second subset of ultrasonic transducers of the fingerprint sensor are activated, the second subset of ultrasonic transducers for determining whether the object is a human finger, wherein the second subset of ultrasonic transducers comprises a greater number of ultrasonic transducers than the first subset of ultrasonic transducers.

Claims

1. A method for operating a fingerprint sensor comprising a plurality of ultrasonic transducers, the method comprising:

activating a first subset of ultrasonic transducers of the fingerprint sensor, the first subset of ultrasonic transducers for detecting interaction between an object and the fingerprint sensor; and

subsequent to detecting interaction between an object and the fingerprint sensor, activating a second subset of ultrasonic transducers of the fingerprint sensor, the second subset of ultrasonic transducers for determining whether the object is a human finger, wherein the second subset of ultrasonic transducers comprises a greater number of ultrasonic transducers than the first subset of ultrasonic transducers.

2. The method of claim 1, further comprising:

responsive to determining that the object is a human finger, capturing an image of a fingerprint of the finger.

3. The method of claim 2 further comprising:

transmitting the image of the fingerprint to a host processor.

4. The method of claim 3 further comprising:

responsive to transmitting the image of the fingerprint to the host processor, entering a sleep mode for a predetermined period; and

after the predetermined period, performing the activating the first subset of ultrasonic transducers of the fingerprint sensor.

5. The method of claim 1, wherein the ultrasonic transducers are Piezoelectric Micromachined Ultrasonic Transducer (PMUT) devices.

6. The method of claim 1, further comprising:

responsive to not detecting interaction between an object and the fingerprint sensor, entering a sleep mode for a predetermined period; and

after the predetermined period, performing the activating the first subset of ultrasonic transducers of the fingerprint sensor.

7. The method of claim 6, wherein the activating a first subset of ultrasonic transducers of the fingerprint sensor is performed periodically until interaction between an object and the fingerprint sensor is detected.

8. The method of claim 1, wherein the activating the first subset of ultrasonic transducers of the fingerprint sensor comprises:

capturing a pixel using the first subset of ultrasonic transducers;

comparing a signal of the pixel to a threshold; and

provided the signal is outside the threshold, determining that interaction between an object and the fingerprint sensor is detected.

9. The method of claim 8, wherein the plurality of ultrasonic transducers is arranged into a plurality of blocks, and wherein the capturing a pixel using the first subset of ultrasonic transducers comprises:

capturing a pixel for at least two blocks of the plurality of blocks.

10. The method of claim 8, wherein the threshold comprises an offset and a range.

11. The method of claim 10, further comprising:

responsive to determining that the object is not a human finger, updating the offset of the threshold with the signal.

12. The method of claim 1, wherein the activating the second subset of ultrasonic transducers of the fingerprint sensor comprises:

capturing a plurality of pixels arranged to detect characteristics of a fingerprint on the object;

determining whether the plurality of pixels comprises characteristics of a fingerprint; and

provided the plurality of pixels comprises characteristics of a fingerprint, determining that the object is a human finger.

13. The method of claim 12, wherein the plurality of pixels are arranged in orthogonal vectors.

14. The method of claim 12, wherein the plurality of ultrasonic transducers is arranged into a plurality of blocks, and wherein the capturing the plurality of pixels arranged to detect characteristics of a fingerprint on the object comprises:

capturing orthogonal vectors of pixels for at least one block of the plurality of blocks.

15. The method of claim 12, wherein the determining whether the plurality of pixels comprises characteristics of a fingerprint comprises:

determining whether the plurality of pixels is indicative of ridge/valley pattern.

16. A non-transitory computer-readable storage medium comprising instructions which when executed on one or more data processors, cause the one or more data processors to perform a method for operating a fingerprint sensor comprising a plurality of ultrasonic transducers, the method comprising:

activating a first subset of ultrasonic transducers of the fingerprint sensor, the first subset of ultrasonic transducers for detecting interaction between an object and the fingerprint sensor;

subsequent to detecting interaction between an object and the fingerprint sensor, activating a second subset of ultrasonic transducers of the fingerprint sensor, the second subset of ultrasonic transducers for determining whether the object is a human finger, wherein the second subset of ultrasonic transducers comprises a greater number of ultrasonic transducers than the first subset of ultrasonic transducers.

17. The non-transitory computer-readable storage medium of claim 16, the method further comprising:

responsive to determining that the object is a human finger, capturing an image of a fingerprint of the finger.

18. The non-transitory computer-readable storage medium of claim 16, the method further comprising:

responsive to transmitting the image of the fingerprint to a host processor, entering a sleep mode for a predetermined period; and

after the predetermined period, performing the activating the first subset of ultrasonic transducers of the fingerprint sensor.

19. The non-transitory computer-readable storage medium of claim 16, the method further comprising:

responsive to not detecting interaction between an object and the fingerprint sensor, entering a sleep mode for a predetermined period; and

after the predetermined period, performing the activating the first subset of ultrasonic transducers of the fingerprint sensor.

20. The non-transitory computer-readable storage medium of claim 16, wherein the activating the first subset of ultrasonic transducers of the fingerprint sensor comprises:

capturing a pixel using the first subset of ultrasonic transducers;

comparing a signal of the pixel to a threshold; and

provided the signal is outside the threshold, determining that interaction between an object and the fingerprint sensor is detected.

21. The non-transitory computer-readable storage medium of claim 20, the method further comprising:

responsive to determining that the object is not a human finger, updating the threshold based on the signal.

22. The non-transitory computer-readable storage medium of claim 16, wherein the activating the second subset of ultrasonic transducers of the fingerprint sensor comprises:

capturing a plurality of pixels arranged to detect characteristics of a fingerprint on the object, wherein the plurality of pixels are arranged in orthogonal vectors;

determining whether the plurality of pixels comprises characteristics of a fingerprint; and

provided the plurality of pixels comprises characteristics of a fingerprint, determining that the object is a human finger.

23. A fingerprint sensor comprising:

a plurality of ultrasonic transducers;

a memory; and

a processor coupled to the memory and the plurality of ultrasonic transducers, the processor configured to;

activate a first subset of ultrasonic transducers of the plurality of ultrasonic transducers, the first subset of ultrasonic transducers for detecting interaction between an object and the fingerprint sensor;

subsequent to detecting interaction between an object and the fingerprint sensor, activate a second subset of ultrasonic transducers of the plurality of ultrasonic transducers of the fingerprint sensor, the second subset of ultrasonic transducers for determining whether the object is a human finger, wherein the second subset of ultrasonic transducers comprises a greater number of ultrasonic transducers than the first subset of ultrasonic transducers; and

responsive to determining that the object is a human finger, capture an image of a fingerprint of the finger.