Dynamic finger detection mechanism for a fingerprint sensor

• US 7,831,070 B1
• Filed: 02/18/2005
• Issued: 11/09/2010
• Est. Priority Date: 02/18/2005
• Status: Expired due to Fees

• Current Assignee: Apple Inc.
• Original Assignee: AuthenTec Incorporated (Apple Inc.)
• Inventors: Pradenas, Ricardo Dario, Cheng, Ericson W., Russo, Anthony P., Weigand, David L.
• Primary Examiner(s): Mariam; Daniel G
• Assistant Examiner(s): WOLDEMARIAM, AKILILU K
• Application Number:
  US11/060,846
• Time in Patent Office: 2,090 Days
• Field of Search: 382/124, 382/218, 382/228, 324/727, 713/186, 713/202, 345/157, 709/219, 250/221, 455/414.1, 340/5.52, 340/5.535, 340/5.82, 340/5.83, 902/3
• US Class Current: 382/124
• CPC Class Codes: G06V 40/13 Sensors therefor

Abstract

The present invention discloses an apparatus for determining the presence of a patterned object on the surface of a sensor. The apparatus comprises a sensor system coupled to a means for generating a control signal. The sensor system is configured to sense an image corresponding to the patterned object and to translate the image into image data. The means for generating a control signal generates a control signal if statistics of the image data exceed a pre-determined number of threshold levels. In a preferred embodiment, the patterned object is finger with a fingerprint on its surface and the sensor is fingerprint swipe sensor. Preferably, the threshold levels are software programmable.

Claims

1. An apparatus for determining a presence of a patterned biometric object, the apparatus comprising:

a biometric sensor system configured to detect a presence of the patterned biometric object, to sense an image corresponding to the patterned biometric object and to translate the image into image data;

logic configured to be enabled based upon detecting the presence of the patterned biometric object, and to determine multiple values corresponding to multiple different statistical properties of the image data the logic comprising a plurality of statistical engines for the corresponding multiple values, and a plurality of comparators coupled to said plurality of statistical engines for generating output signals, the output signals indicating when the multiple values exceed a corresponding number of threshold levels; and

a signal generator configured to receive the output signals generate a wake up signal in the event a predetermined combination of the multiple values exceed a corresponding number of threshold levels.

2. The apparatus of claim 1, wherein the biometric sensor system comprises:

a biometric image sensor; and

a signal converter coupled to the biometric image sensor.

3. The apparatus of claim 2, further comprising:

a memory coupled to the signal converter, the memory containing one or more output lines for coupling to a host system; and

a processor coupled to the biometric image sensor, the signal converter, the memory, and the logic.

4. The apparatus of claim 3, wherein the signal converter comprises an analog-to-digital converter.

5. The apparatus of claim 4, wherein the biometric image sensor is a fingerprint image sensor.

6. The apparatus of claim 5, wherein the fingerprint image sensor is a swipe sensor.

7. The apparatus of claim 5, wherein the fingerprint image sensor is a placement sensor.

8. The apparatus of claim 6, wherein the swipe sensor is a capacitive sensor.

9. The apparatus of claim 6, wherein the swipe sensor is one of thermal sensor and an optical sensor.

10. The apparatus of claim 5, wherein the logic comprises:

a first statistical engine coupled to the analog-to-digital converter and the processor;

a second statistical engine coupled to the memory, the first statistical engine, and the processor; and

an ac-energy-estimation engine coupled to the memory and the processor.

11. The apparatus of claim 10, wherein the logic further comprises:

a first comparator coupled to the first statistical engine and the processor, the first comparator configured to generate a first output when the output of the first statistical engine exceeds a first threshold value;

a second comparator coupled to the second statistical engine and the processor, the second comparator configured to generate a second output when the output of the second statistical engine exceeds a second threshold value; and

a third comparator coupled to the ac-energy-estimation engine and the processor, the third comparator for generating a third output when the output of the threshold crossing engine exceeds a third threshold value.

12. The apparatus of claim 11, wherein the biometric sensor system comprises a software programmable detection engine coupled to and configured to enable the analog-to-digital converter, the first statistical engine, the second statistical engine, and the ac-energy-estimation engine.

13. The apparatus of claim 12, wherein the software programmable detection engine comprises a software programmable capacitive bridge.

14. The apparatus of claim 13, wherein the software programmable capacitive bridge comprises one or more capacitors configured to be programmed to a detection threshold level.

15. The apparatus of claim 11, wherein the first statistical engine is a mean engine and the first comparator is a mean comparator.

16. The apparatus of claim 11, wherein the second statistical engine is a variance engine and the second comparator is a variance comparator.

17. The apparatus of claim 11, wherein the third statistical engine is a ac-energy-estimation engine and the third comparator is an ac-energy-estimation comparator.

18. The apparatus of claim 11, wherein the first threshold value is related to a mean of the image data, the second threshold value is related to a variance of the image data, the third threshold value is related to an ac-energy-estimation of the image data and the fourth threshold value is related to the software programmable capacitance detection.

19. The apparatus of claim 11, wherein at least one of the first comparator is configured to be programmed with the first threshold value, the second comparator is configured to be programmed with the second threshold value, and the third comparator is configured to be programmed with the third threshold value.

20. The apparatus of claim 11, further comprising a host platform coupled to the logic.

21. The apparatus of claim 20, wherein the one or more output lines are coupled to the host platform.

22. The apparatus of claim 21, wherein the host platform comprises an interrupt signal line coupled to at least one of the first comparator, the second comparator, and the third comparator.

23. The apparatus of claim 22, wherein the signal generator comprises a voter circuit comprising the interrupt signal line, the voter circuit coupled to the first comparator, the second comparator, and the third comparator.

24. The apparatus of claim 20, wherein the host platform comprises a personal computer.

25. The apparatus of claim 20, wherein the host platform comprises a portable device.

26. The apparatus of claim 25, wherein the portable device comprises a device selected from the group consisting of a telephone, a personal digital assistant, a personal music player, and a camera.

27. The apparatus of claim 22, wherein the host platform is configured to receive at least one of the output from the first comparator, the output from the second comparator, and the output from the third comparator and use each of the outputs to set at least one of the first threshold value, the second threshold value, and the third threshold value.

28. The apparatus of claim 5, wherein the fingerprint image sensor is logically divided into a plurality of regions.

29. An apparatus comprising:

a biometric sensor system configured to detect a presence of a biometric object, sense an image corresponding to the biometric object, and translate the image into image data;

logic configured to be powered on based upon detecting the presence of the biometric object, and determine multiple values corresponding to multiple different statistical properties of the image data the logic comprising a plurality of statistical engines for the corresponding multiple values, and a plurality of comparators coupled to said plurality of statistical engines for generating output signals, the output signals indicating when the multiple values exceed a corresponding number of threshold levels; and

a signal generator configured to receive the output signals generate a wake up signal based upon a combination of the multiple values.

30. The apparatus of claim 29, wherein the biometric sensor system comprises:

a biometric image sensor; and

a signal converter coupled to the biometric image sensor.

31. The apparatus of claim 30, further comprising:

a memory coupled to the signal converter, the memory containing one or more output lines for coupling to a host system; and

a processor coupled to the biometric image sensor, the signal converter, the memory, and the logic.

32. The apparatus of claim 31, wherein the logic comprises:

a first statistical engine coupled to the analog-to-digital converter and the processor;

a second statistical engine coupled to the memory, the first statistical engine, and the processor; and

an ac-energy-estimation engine coupled to the memory and the processor.

33. The apparatus of claim 32, wherein the logic further comprises:

a first comparator coupled to the first statistical engine and the processor, the first comparator configured to generate a first output when the output of the first statistical engine exceeds a first threshold value;

a second comparator coupled to the second statistical engine and the processor, the second comparator configured to generate a second output when the output of the second statistical engine exceeds a second threshold value; and

a third comparator coupled to the ac-energy-estimation engine and the processor, the third comparator for generating a third output when the output of the threshold crossing engine exceeds a third threshold value.

34. The apparatus of claim 33, wherein the first statistical engine is a mean engine and the first comparator is a mean comparator;

wherein the second statistical engine is a variance engine and the second comparator is a variance comparator; and

wherein the third statistical engine is a ac-energy-estimation engine and the third comparator is an ac-energy-estimation comparator.

35. The apparatus of claim 29, further comprising a host platform coupled to the logic.

36. The apparatus of claim 29, wherein the fingerprint image sensor is logically divided into a plurality of regions.