System for and method of determining pressure on a finger sensor

• US 7,280,679 B2
• Filed: 04/07/2005
• Issued: 10/09/2007
• Est. Priority Date: 10/08/2004
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Atrua Technologies Incorporated (Apple Inc.)
• Inventors: Russo, Anthony P.
• Primary Examiner(s): Mehta; Bhavesh M.
• Assistant Examiner(s): Strege; John B
• Application Number:
  US11/102,227
• Publication Number:
  US 20060078174A1
• Time in Patent Office: 915 Days
• Field of Search: 382/124, 382/115, 340/5.53, 340/5.83
• US Class Current: 382/124
• CPC Class Codes: G06F 2203/0338 Fingerprint track pad, i.e. fingerprint sensor used as pointing device tracking the fingertip image
• CPC Class Codes: G06F 3/03547 Touch pads, in which fingers can move on a surface
• CPC Class Codes: G06F 3/0414 using force sensing means to determine a position

Abstract

The present invention discloses a system for and method of calculating pressure differences using a finger sensor. A finger sensor system in accordance with the present invention comprises a finger sensor for capturing first and second of sets of image data by contacting the finger sensor and means for providing a statistical comparison between the first and second sets of image data to determine a total pressure difference. The means for providing a statistical comparison comprises a means for generating first histogram data from the first set of image data and second histogram data from the second set of image data. The means for providing statistical data correlates peaks of the first and second histogram data and also determines differences between variances of the first and second sets of image data.

Claims

1. A system comprising:

a finger sensor for capturing first and second of sets of image data by contacting the finger sensor; and

means for comparing statistical distributions of the first and second sets of image data to determine a total pressure difference, wherein the means for comparing comprises a coarse comparator and a fine comparator.

2. The system of claim 1, wherein the means for comparing statistical distributions further comprises a means for generating first histogram data from the first set of image data and second histogram data from the second set of image data.

3. The system of claim 2, wherein the coarse comparator is configured to determine a translation between the first histogram data and the second histogram data.

4. The system of claim 3, wherein the translation is determined by correlating the first histogram data to the second histogram data.

5. The system of claim 4, wherein correlating the first histogram data to the second histogram data comprises comparing a first peak of the first histogram data to a second peak of the second histogram data.

6. The system of claim 5, wherein a difference between the first peak and the second peak corresponds to an automatic gain control value for the finger sensor.

7. The system of claim 3, wherein the fine comparator is configured to determine a difference between a variance value of the first set of image data and a variance value of the second set of image data.

8. The system of claim 1, wherein the means for comparing statistical distributions is configured to determine a first automatic gain control state based on the first set of image data and a second automatic gain control state based on the second set of image data.

9. The system of claim 8, wherein the means for comparing statistical distributions comprises a host computer executing an application program that receives the total pressure difference.

10. The system of claim 9, wherein the host computer is configured to receive the first and second sets of image data and to determine therefrom the first automatic gain control state and the second gain control state, the host computer further configured to determine the total pressure difference from a difference between the first automatic gain control state and the second automatic gain control state.

11. The system of claim 9, wherein the host computer is configured to receive the first automatic gain control state and the second automatic gain control state and to determine therefrom the total pressure difference.

12. The system of claim 8, wherein the first automatic gain control state is related to a median of the first set of image data and the second automatic gain control state is related to a median of the second set of image data.

13. The system of claim 1, wherein the finger sensor comprises first and second logical segments, wherein the means for comparing statistical distributions is configured to determine a first pressure difference related to the first logical segment and a second pressure difference related to the second logical segment.

14. The system of claim 13, wherein the first pressure difference and the second pressure difference are weighted values of the total pressure difference.

15. The system of claim 1, further comprising a host computer executing an application program that receives the total pressure difference, the host computer comprising a device selected from the group consisting of a personal computer, a personal digital assistant, a digital camera, and a portable gaming device.

16. The system of claim 1, wherein the finger sensor forms part of a finger swipe sensor.

17. The system of claim 16, wherein the finger sensor comprises a capacitive sensor.

18. The system of claim 16, wherein the finger swipe sensor comprises one of an optical sensor and a thermal sensor.

19. The system of claim 1, wherein the finger sensor forms part of a finger placement sensor.

20. The system of claim 9, wherein the finger sensor, the means for comparing statistical distributions, and the host computer form an integrated unit.

21. A method of determining a pressure difference comprising:

capturing first and second of sets of image data by contacting a finger sensor; and

comparing statistical distributions of the first and second sets of image data to determine a total pressure difference by performing a coarse comparison and a fine comparison.

22. The method claim 21, wherein comparing statistical distributions comprises generating first histogram data from the first set of image data and second histogram data from the second set of image data.

23. The method of claim 22, wherein comparing statistical distributions further comprises determining a translation between the first histogram data and the second histogram data.

24. The method of claim 23, wherein determining a translation comprises correlating the first histogram data to the second histogram data.

25. The method of claim 24, wherein correlating the first histogram data to the second histogram data comprises comparing a first peak of the first histogram data to a second peak of the second histogram data.

26. The method of claim 25, wherein a difference between the first peak and the second peak corresponds to an automatic gain control value for the finger sensor.

27. The method of claim 23, wherein comparing statistical distributions further comprises determining a difference between a variance value of the first set of image data and a variance value of the second set of image data.

28. The method of claim 21, wherein comparing statistical distributions comprises determining a first automatic gain control state based on the first set of image data and a second automatic gain control state based on the second set of image data.

29. The method of claim 28, further comprising executing on a host computer an application program that receives the total pressure difference.

30. The method of claim 29, wherein the host computer is configured to receive the first and second sets of image data and to determine therefrom the first automatic gain control state and the second automatic gain control state, the host computer further configured to determine the total pressure difference from a difference between the first automatic gain control state and the second automatic gain control state.

31. The method of claim 29, wherein the host computer is configured to receive the first automatic gain control state and the second automatic gain control state and to determine therefrom the total pressure difference.

32. The method of claim 28, wherein the first automatic gain control state is related to a median of the first set of image data and the second automatic gain control state is related to a median of the second set of image data.

33. The method of claim 21, wherein the finger sensor comprises first and second logical segments, and further wherein comparing statistical distributions comprises determining a first pressure difference related to the first logical segment and a second pressure difference related to the second logical segment.

34. The method of claim 33, wherein the first pressure difference and the second pressure difference are weighted values of the total pressure difference.

35. The method of claim 21, further comprising executing on a host computer an application for receiving the total pressure difference, wherein the host computer comprises a device selected from the group consisting of a personal computer, a personal digital assistant, a digital camera, and a portable gaming device.

36. The method of claim 21, wherein the finger sensor forms part of a finger swipe sensor.

37. The method of claim 36, wherein the finger sensor comprises a capacitive sensor.

38. The method of claim 36, wherein the finger swipe sensor comprises one of an optical sensor and a thermal sensor.

39. The method of claim 21, wherein the finger sensor forms part of a finger placement sensor.

40. A system for determining a pressure difference comprising:

a finger sensor for capturing first and second sets of finger image data for a finger on the finger sensor; and

a pressure calculator coupled to the finger sensor, wherein the pressure calculator is configured to compare a first statistical distribution of the first set of finger image data to a second statistical distribution of the second set of finger image data by performing a coarse comparison and a fine comparison to determine whether more or less pressure is applied by the finger on the finger sensor.