Swiped aperture capacitive fingerprint sensing systems and methods

• US 7,099,496 B2
• Filed: 12/05/2001
• Issued: 08/29/2006
• Est. Priority Date: 12/05/2000
• Status: Expired due to Term

• Current Assignee: Synaptics Incorporated
• Original Assignee: Validity Sensors Incorporated (Synaptics Incorporated)
• Inventors: Benkley, Fred G. III
• Primary Examiner(s): Wu, Jingge
• Assistant Examiner(s): CARTER, AARON W
• Application Number:
  US10/005,643
• Publication Number:
  US 20030035570A1
• Time in Patent Office: 1,728 Days
• Field of Search: 382/106, 382/107, 382/122, 382124-127, 356 3- 22, 356 27- 285, 356/71, 735/143.2, 361280-330, 324/686, 324/666, 324/662
• US Class Current: 382/124
• CPC Class Codes: G06V 40/1306 non-optical, e.g. ultrasonic or capacitive sensing
• CPC Class Codes: G06V 40/1335 Combining adjacent partial images (e.g. slices) to create a composite input or reference pattern; Tracking a sweeping finger movement

Abstract

A fingerprint sensing system includes an image sensor, a rate sensor and a sensor circuit. The image sensor includes a linear array of capacitive sensors for capacitive sensing of ridge peaks and ridge valleys of a fingerprint on a swiped finger. The rate sensor senses the speed of the finger as it is swiped across the image sensor. The sensor circuit supplies image drive signals to the image sensor and detects image signals in response to the drive signals. The sensor circuit supplies rate drive signals to the rate sensor and detects rate signals in response to the rate drive signals. The sensor circuit further coordinates the image signals and the rate signals to provide a fingerprint image. The image sensor may be configured as an image pickup plate and multiple image drive plates formed on a substrate, such as a flexible printed circuit board or other flexible substrate which may conform to the shape of the finger.

Claims

1. Image sensing apparatus comprising:

an image pickup plate disposed generally laterally with respect to a direction of movement of a finger; and

a plurality of image drive plates in spaced relation to said image pickup plate to define a plurality of sensor gaps between respective image drive plates and said image pickup plate, wherein features of a fingerprint on the finger passing over said sensor gaps produce a change in capacitance between respective image drive plates and said image pickup plate.

2. Image sensing apparatus as defined in claim 1, wherein said image pickup plate and said plurality of image drive plates are dimensioned and spaced for sensing the fingerprint.

3. Image sensing apparatus as defined in claim 2, wherein a spacing between each of said image drive plates and said image pickup plate is less than about one half of the ridge spacing on a typical fingerprint.

4. Image sensing apparatus as defined in claim 2, wherein a spacing between adjacent ones of said image drive plates is less than about one half of the ridge spacing on a typical fingerprint.

5. Image sensing apparatus as defined in claim 1, wherein said image drive plates comprise parallel conductors disposed perpendicular to said image pickup plate and spaced from said image pickup plate by respective sensor gaps.

6. Image sensing apparatus as defined in claim 1, wherein said image pickup plate comprises two or more image pickup plates disposed generally laterally with respect to the direction of movement of the object.

7. Image sensing apparatus as defined in claim 2, including at least about 250 image drive plates.

8. Image sensing apparatus as defined in claim 1, further comprising a substrate, wherein said image pickup plate and said plurality of image drive plates comprise conductive traces on said substrate.

9. Image sensing apparatus as defined in claim 8, wherein said substrate comprises a printed circuit board.

10. Image sensing apparatus as defined in claim 8, wherein said substrate comprises a flexible substrate.

11. Image sensing apparatus as defined in claim 10, further comprising a substrate support, wherein said flexible substrate is affixed to said substrate support and wherein said substrate support has a contour selected to substantially match the contour of a typical finger.

12. Image sensing apparatus as defined in claim 1, further comprising:

an excitation circuit for sequentially energizing said image drive plates with drive signals, and

a detection circuit for detecting the drive signals capacitively coupled from said image drive plates to said image pickup plate to provide image signals.

13. Image sensing apparatus as defined in claim 12, wherein said drive signals comprise sequential signal bursts applied to respective ones of said image drive plates.

14. Image sensing apparatus as defined in claim 13, wherein said excitation circuit includes circuitry for coupling non-energized image drive plates to a reference potential.

15. Image sensing apparatus as defined in claim 13, wherein said signal bursts comprise bursts of a clock signal.

16. Image sensing apparatus as defined in claim 13, wherein said detection circuit comprises a synchronous detector for providing pulses in response to the detected signal bursts.

17. Image sensing apparatus as defined in claim 16, further comprising an analog-to-digital converter for converting said pulses to digital values, a memory and a processor for storing the digital values in said memory.

18. Image sensing apparatus as defined in claim 17, wherein said processor initiates a plurality of sequential line scans of said image drive plates to provide a plurality of line scans along lines of the moving object.

19. Image sensing apparatus as defined in claim 12, wherein said detection circuit includes an amplifier for receiving the capacitively coupled drive signals, said amplifier having a gain that is an inverse function of the amplitude of the capacitively coupled drive signals.

53. Image sensing apparatus as defined in claim 1, wherein said image pickup plate and said plurality of image drive plates are substantially coplanar.

20. A fingerprint sensing system comprising:

an image sensor comprising an array of capacitive sensors for capacitive sensing of ridge peaks and ridge valleys of a fingerprint on a moving finger, said image sensor comprising;

an image pickup plate disposed generally laterally with respect to a direction of movement of the finger; and

a plurality of image drive plates in spaced relation to said image pickup plate to define a plurality of sensor gaps between respective image drive plates and said image pickup plate, wherein ridge peaks and ridge valleys of the fingerprint passing over said sensor gaps produce a change in capacitance between respective image drive plates and said image pickup plate;

a finger sensor for sensing a speed of the finger as it moves across said image sensor; and

a sensor circuit for excitation of said image sensor with image drive signals and for detection of image signals in response to said image drive signals, for excitation of said finger sensor with finger drive signals and for detection of finger signals in response to said finger drive signals, and for coordinating said image signals and said finger signals to provide a fingerprint image.

21. A fingerprint sensing system as defined in claim 20, wherein a spacing between each of said image drive plates and said image pickup plate is less than about one half of the ridge spacing on a typical fingerprint.

22. A fingerprint sensing system as defined in claim 20, wherein a spacing between adjacent ones of said image drive plates is less than about one half of the ridge spacing on a typical fingerprint.

23. A fingerprint sensing system as defined in claim 20, wherein said image drive plates comprise parallel conductors disposed perpendicular to said image pickup plate and spaced from said image pickup plate by respective sensor gaps.

24. A fingerprint sensing system as defined in claim 20, wherein said at least one image pickup plate comprises two or more image pickup plates disposed generally laterally with respect to the direction of movement of the finger.

25. A fingerprint sensing system as defined in claim 20, including at least about 250 image drive plates.

26. A fingerprint sensing system as defined in claim 20, further comprising a substrate, wherein said at least one image pickup plate and said plurality of image drive plates comprise conductive traces on said substrate.

27. A fingerprint sensing system as defined in claim 26, wherein said substrate comprises a flexible substrate.

28. A fingerprint sensing system as defined in claim 27, further comprising a substrate support, wherein said flexible substrate is affixed to said substrate support and wherein said substrate support has a contour selected to substantially match the contour of a typical finger.

29. A fingerprint sensing system as defined in claim 20, wherein said sensor circuit comprises:

an excitation circuit for sequentially energizing said image drive plates with said image drive signals, and

a detection circuit for detecting the image drive signals capacitively coupled from said image drive plates to said image pickup plate to provide said image signals.

30. A fingerprint sensing system as defined in claim 29, wherein said image drive signals comprise sequential signal bursts applied to respective ones of said image drive plates.

31. A fingerprint sensing system as defined in claim 30, wherein said excitation circuit includes circuitry for coupling non-energized image drive plates to a reference potential.

32. A fingerprint sensing system as defined in claim 30, wherein said detection circuit comprises a synchronous detector for providing pulsed image signals.

33. A fingerprint sensing system as defined in claim 32, wherein said sensor circuit further comprises an analog-to-digital converter for converting said pulsed image signals to digital values, a memory and a processor for storing the digital values in said memory.

34. A fingerprint sensing system as defined in claim 33, wherein said processor initiates a plurality of sequential line scans of said image drive plates to provide a plurality of line scans along lines of the moving finger.

35. A fingerprint sensing system as defined in claim 29, wherein said detection circuit includes an amplifier for receiving the capacitively coupled image drive signals, said amplifier having a gain that is an inverse function of the amplitude of the capacitively coupled image drive signals.

36. A fingerprint sensing system as defined in claim 20, wherein said finger sensor comprises:

two or more finger detectors spaced apart along a direction of movement of the finger, each of said finger detectors including at least one finger drive plate and at least one finger pickup plate, wherein an end of the finger passing over each of said finger detectors produces a change in capacitance between respective finger drive plates and finger pickup plates.

37. A fingerprint sensing system as defined in claim 36, wherein the finger drive plate and the finger pickup plate of each of said finger detectors are disposed generally laterally with respect to the direction of movement of the finger.

38. A fingerprint sensing system as defined in claim 36, wherein the finger pickup plates of said finger detectors are commonly connected.

39. A fingerprint sensing system as defined in claim 36, wherein each of said finger detectors includes first and second finger pickup plates disposed on opposite sides of the finger drive, plate to form a differential capacitive sensor.

40. A fingerprint sensing system as defined in claim 39, wherein the finger drive plates of said finger detectors are commonly connected.

41. A fingerprint sensing system as defined in claim 36, wherein the finger drive plates and the finger pickup plates of said finger detectors are curved to substantially match the curve of a typical finger end.

42. A fingerprint sensing system as defined in claim 36, further comprising a substrate, wherein said finger drive plates and said finger pickup plates comprise conductive traces on said substrate.

43. A fingerprint sensing system as defined in claim 36, further comprising a flexible substrate, wherein said finger drive plates and said finger pickup plates comprise conductive traces on said flexible substrate.

44. A fingerprint sensing system as defined in claim 36, wherein said sensor circuit comprises:

an excitation circuit for energizing the finger drive plates of said finger detectors with said finger drive signals, and

a detection circuit for detecting the finger drive signals capacitively coupled from the finger drive plate to the finger pickup plate of each of said finger detectors to provide said finger signals.

45. A fingerprint sensing system as defined in claim 44, wherein said finger drive signals comprise signal bursts.

46. A fingerprint sensing system as defined in claim 45, wherein said detection circuit comprises a synchronous detector.

47. A fingerprint sensing system as defined in claim 44, wherein said sensor circuit further comprises a processing circuit for detecting a time delay between said finger signals from said finger detectors, wherein said time delay between said finger signals is representative of the speed of the finger.

48. A fingerprint sensing system as defined in claim 20, further comprising a substrate, wherein said image sensor and said finger sensor are fabricated on said substrate.

49. A fingerprint sensing system as defined in claim 48, wherein said substrate comprises a flexible substrate.

50. A fingerprint sensing system as defined in claim 48, wherein said sensor circuit is mounted on said substrate.

54. A fingerprint sensing system as defined in claim 20, wherein said image pickup plate and said plurality of drive plates are substantially coplanar.

55. A fingerprint sensing system as defined in claim 36, wherein the finger drive plate and the finger pickup plate of each of said finger detectors are substantially coplanar.

51. A fingerprint sensing method, comprising the steps of:

capacitively sensing ridge peaks and ridge valleys of a fingerprint on a swiped finger with an array of capacitive sensors and providing image signals representative of a line of the fingerprint, the array of capacitive sensors comprising an image pickup plate and a plurality of image drive plates in spaced relation to the image pickup plate to define a plurality of sensor gaps between respective image drive plates and the image pickup plate; and

acquiring from the array of capacitive sensors image signals representative of multiple lines of the fingerprint to provide a fingerprint image.

52. A fingerprint sensing method as defined in claim 51, further comprising:

sensing a speed of the finger as it is swiped across the array of capacitive sensors and providing finger signals; and

coordinating the image signals and the finger signals to provide a fingerprint image.

56. A capacitive sensor comprising:

a pickup plate; and

a plurality of drive plates in spaced relation to said pickup plate to define an array of sensor gaps between respective drive plates and said pickup plate, said pickup plate and said plurality of drive plates being substantially coplanar, wherein a finger passing above said array of sensor gaps produces a change in capacitance between respective drive plates and said pickup plate.

57. A capacitive sensor as defined in claim 56, wherein said pickup plate and said plurality of drive plates comprise conductive traces on a substrate.

58. A capacitive sensor as defined in claim 57, wherein said substrate comprises a flexible substrate.

59. A capacitive sensor as defined in claim 56, wherein said pickup plate and said plurality of drive plates are dimensioned and spaced for sensing a fingerprint on the finger.

60. A capacitive sensor as defined in claim 56, wherein said array of sensor gaps comprises a linear array.

61. A capacitive sensor as defined in claim 58, wherein said sensor gaps have dimensions of about 5 to 50 micrometers.

62. A fingerprint sensing system comprising:

an image sensor comprising an array of capacitive sensors for capacitive sensing of ridge peaks and ridge valleys of a fingerprint on a moving finger;

a finger sensor for sensing the speed of a finger as it moves across said image sensor, wherein said image sensor and said finger sensor are fabricated on a single substrate;

a sensor circuit, separate from said substrate, for operating said image sensor and said finger sensor to provide fingerprint data; and

wherein said image sensor further comprises;

an image pickup plate disposed generally laterally with respect to a direction of movement of the finger; and

a plurality of image drive plates in spaced relation to said imaae pickup plate to define a plurality of sensor gaps between respective image drive plates and image pickup plate.

63. A fingerprint sensing system as defined in claim 62, wherein said image pickup plate and said plurality of drive plates are substantially coplanar on said substrate.

64. Fingerprint sensing apparatus comprising:

an image sensor comprising an image pickup plate disposed generally laterally with respect to a direction of movement of a finger; and

a plurality of image drive plates in spaced relation to said image pickup plate to define a plurality of sensor gaps between respective image drive plates and said image pickup plate, wherein said image pickup plate and said plurality of image drive plates are fabricated on a substrate; and

a sensor circuit, separate from said substrate, for excitation of said image sensor with image drive signals and for detection of image signals generated by said image sensor in response to said image drive signals.

65. Fingerprint sensing apparatus as defined in claim 64, wherein said image pickup plate and said plurality of image drive plates are substantially coplanar on said substrate.

66. A fingerprint sensor comprising:

a substrate;

an image pickup plate fabricated on said substrate and disposed generally laterally with respect to a direction of movement of a finger; and

a plurality of image drive plates fabricated on said substrate in spaced relation to said image pickup plate to define a plurality of sensor gaps between respective image drive plates and said image pickup plate.

67. A fingerprint sensor as defined in claim 66, wherein said plurality of sensor gaps comprises a linear array of sensor gaps.

68. A fingerprint sensor as defined in claim 66, wherein said image pickup plate and said plurality of image drive plates are substantially coplanar on said substrate.

69. A fingerprint sensor as defined in claim 66, further comprising a finger sensor, fabricated on said substrate, for sensing the speed of the finger as it moves across the sensor gaps.