Finger sensing device including differential measurement circuitry and related methods

• US 8,888,004 B2
• Filed: 10/07/2011
• Issued: 11/18/2014
• Est. Priority Date: 10/08/2010
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: AuthenTec Incorporated (Apple Inc.)
• Inventors: Setlak, Dale R., Landy, Patrick J., Straub, Albert M., Schenk, Roger Lee
• Primary Examiner(s): TRAIL, ALLYSON NEEL
• Application Number:
  US13/269,316
• Publication Number:
  US 20120085822A1
• Time in Patent Office: 1,138 Days
• Field of Search: 235/439, 345/175, 324/658
• US Class Current: 235/439
• CPC Class Codes: G06V 10/20 Image preprocessing
• CPC Class Codes: G06V 40/1306 non-optical, e.g. ultrasonic or capacitive sensing

Abstract

A finger sensing device may include an array of finger sensing pixels to receive a user'"'"'s finger adjacent thereto. Each finger sensing pixel may include a finger sensing electrode. The finger sensing device may include a finger drive electrode configured to couple a drive signal through the user'"'"'s finger to the array of finger sensing pixels. The finger sensing device may also include differential pixel measurement circuitry coupled to the array of finger sensing pixels and configured to generate a plurality of interpixel difference measurements for adjacent pairs of the finger sensing pixels.

Claims

1. A finger sensing device comprising:

an array of finger sensing pixels to receive a user'"'"'s finger adjacent thereto, each finger sensing pixel comprising a finger sensing electrode;

a finger drive electrode configured to cooperate with said array of finger sensing pixels to couple a drive signal through the user'"'"'s finger; and

differential pixel measurement circuitry coupled to said array of finger sensing pixels and configured to generate a plurality of interpixel difference measurements for adjacent pairs of said finger sensing pixels.

2. The finger sensing device of claim 1, further comprising a cover layer over said finger sensing pixels having a thickness in a range of 100-900 microns.

3. The finger sensing device of claim 1, wherein said differential pixel measurement circuitry comprises balanced differential pixel measurement circuitry.

4. The finger sensing device of claim 3, wherein said balanced differential pixel measurement circuitry comprises:

a respective differential amplifier stage coupled to each finger sensing electrode of each finger sensing pixel;

switching circuitry to selectively couple respective pairs of differential amplifier stages in a differential configuration for the adjacent pairs of said finger sensing pixels; and

an output stage coupled to said switching circuitry.

5. The finger sensing device of claim 1, wherein said array of finger sensing pixels comprises rows and columns of finger sensing pixels;

and wherein said differential pixel measurement circuitry comprises switching circuitry for generating the plurality of interpixel measurements for adjacent pairs of said finger sensing pixels along both rows and columns of said array of finger sensing pixels.

6. The finger sensing device of claim 5, further comprising image generating circuitry coupled to said differential measurement circuitry and configured to generate a composite finger image based upon the interpixel measurements for adjacent pairs of said finger sensing pixels along both rows and columns of said array of finger sensing pixels.

7. The finger sensing device of claim 6, wherein said image generating circuitry comprises kernel filtering circuitry coupled to said differential measurement circuitry.

8. The finger sensing device of claim 1, further comprising a semiconductor substrate;

and wherein said array of finger sensing pixels are on said semiconductor substrate.

9. The finger sensing device of claim 1, further comprising a radio frequency drive signal generator coupled to said finger drive electrode.

10. A finger sensing device comprising:

an array of finger sensing pixels to receive a user'"'"'s finger adjacent thereto, each finger sensing pixel comprising a finger sensing electrode;

a finger drive electrode configured to cooperate with said array of finger sensing pixels to couple a drive signal through the user'"'"'s finger;

balanced differential pixel measurement circuitry coupled to said array of finger sensing pixels and configured to generate a plurality of interpixel difference measurements for adjacent pairs of said finger sensing pixels; and

a cover layer over said finger sensing pixels having a thickness in a range of 100-900 microns.

11. The finger sensing device of claim 10, wherein said balanced differential pixel measurement circuitry comprises:

a respective differential amplifier stage coupled to each finger sensing electrode of each finger sensing pixel;

switching circuitry to selectively couple respective pairs of differential amplifier stages in a differential configuration for the adjacent pairs of said finger sensing pixels; and

an output stage coupled to said switching circuitry.

12. The finger sensing device of claim 10, wherein said array of finger sensing pixels comprises rows and columns of finger sensing pixels;

and wherein said balanced differential pixel measurement circuitry comprises switching circuitry for generating the plurality of interpixel measurements for adjacent pairs of said finger sensing pixels along both rows and columns of said array of finger sensing pixels.

13. The finger sensing device of claim 12, further comprising image generating circuitry coupled to said balanced differential pixel measurement circuitry and configured to generate a composite finger image based upon the interpixel measurements for adjacent pairs of said finger sensing pixels along both rows and columns of said array of finger sensing pixels.

14. The finger sensing device of claim 13, wherein said image generating circuitry comprises kernel filtering circuitry coupled to said balanced differential pixel measurement circuitry.

15. The finger sensing device of claim 10, further comprising a semiconductor substrate;

and wherein said array of finger sensing pixels are on said semiconductor substrate.

16. The finger sensing device of claim 10, further comprising a radio frequency drive signal generator coupled to said finger drive electrode.

17. A method of sensing a finger comprising:

receiving a user'"'"'s finger adjacent an array of finger sensing pixels, each finger sensing pixel comprising a finger sensing electrode;

cooperating with the array of finger sensing pixels to couple a drive signal through the user'"'"'s finger to the via a finger drive electrode; and

generating a plurality of interpixel difference measurements for adjacent pairs of the finger sensing pixels using differential pixel measurement circuitry coupled to the array of finger sensing pixels.

18. The method of claim 17, further comprising a cover layer over the finger sensing pixels having a thickness in a range of 100-900 microns.

19. The method sensing device of claim 17, wherein the differential pixel measurement circuitry comprises balanced differential pixel measurement circuitry.

20. The method of claim 19, wherein the balanced differential pixel measurement circuitry comprises:

a respective differential amplifier stage coupled to each finger sensing electrode of each finger sensing pixel;

switching circuitry to selectively couple respective pairs of differential amplifier stages in a differential configuration for the adjacent pairs of the finger sensing pixels; and

an output stage coupled to the switching circuitry.

21. The method of claim 17, wherein the array of finger sensing pixels comprises rows and columns of finger sensing pixels;

wherein the differential pixel measurement circuitry comprises switching circuitry; and

wherein the plurality of interpixel measurements are generated for adjacent pairs of the finger sensing pixels along both rows and columns of the array of finger sensing pixels using the switching circuitry.

22. The method of claim 21, further comprising generating a composite finger image based upon the interpixel measurements for adjacent pairs of the finger sensing pixels along both rows and columns of the array of finger sensing pixels via image generating circuitry coupled to the differential measurement circuitry.

23. The method of claim 22, wherein the composite finger image is generated via kernel filtering circuitry coupled to the differential measurement circuitry.