Live finger detection

• US 8,374,407 B2
• Filed: 01/28/2009
• Issued: 02/12/2013
• Est. Priority Date: 01/28/2009
• Status: Active Grant

• Current Assignee: Synaptics Incorporated
• Original Assignee: Validity Sensors Incorporated (Synaptics Incorporated)
• Inventors: Benkley, Fred George, Geoffroy, David Joseph
• Primary Examiner(s): Liew, Alex
• Application Number:
  US12/361,408
• Publication Number:
  US 20100189314A1
• Time in Patent Office: 1,476 Days
• Field of Search: 382115-118, 382124-127
• US Class Current: 382/124
• CPC Class Codes: G06V 40/1394 using acquisition arrangements

Abstract

A live finger detection system and method includes a drive plate configured to inject radio frequency signals into an object proximate the drive plate. The injected radio frequency energy causes the object to radiate an electric field. A pickup plate is configured to detect an intensity associated with the electric field radiated by the object. A sensor coupled to the pickup plate is configured to determine whether the object is a live finger based on the detected intensity of the electric field radiated by the object.

Claims

1. A detection apparatus comprising:

a plurality of drive plates configured to transmit radio frequency energy to a respective one of a plurality of drive plate contact points formed by an array of the plurality of drive plates;

a pickup plate, separated from each respective drive plate contact point by an injection gap, each respective drive plate and the pickup plate configured to transform the radio frequency energy into an electromagnetic field extending between the respective drive plate and the pickup plate extending across the respective injection gap, and the pickup plate configured to receive a modified electromagnetic field, modified by passing through an object spanning the respective injection gap; and

a sensor coupled to the pickup plate and configured to determine whether the object is a live finger based on the detected intensity of the electromagnetic field passing through the object and received at the pickup plate.

2. The detection apparatus of claim 1, wherein the object is in physical contact with the respective drive plate when the electromagnetic field passes through the object.

3. The detection apparatus of claim 1, wherein the pickup plate is positioned approximately one millimeter from the respective drive plate.

4. The detection apparatus of claim 1, wherein one side of each respective drive plate is formed with a contoured arc that substantially corresponds to the shape of a human finger tip.

5. The detection apparatus of claim 1, wherein the pickup plate is formed with a contoured arc that substantially corresponds to the shape of a human finger tip.

6. The detection apparatus of claim 1, wherein the pickup plate is positioned proximate the object without contacting the object.

7. The detection apparatus of claim 1, wherein the respective drive plate is disposed on a substrate and the pickup plate extends substantially perpendicular to the substrate.

8. The detection apparatus of claim 7, wherein the substrate is a printed circuit board.

9. The detection apparatus of claim 7, wherein the substrate is a flexible substrate.

10. The detection apparatus of claim 1, wherein the respective drive plate receives a drive signal from a signal generator, the drive signal having a frequency in the range of 10-30 MHz.

11. The detection apparatus of claim 1, wherein the respective drive plate receives a drive signal from a signal generator, the drive signal having a magnitude of approximately 2.5 volts.

12. The detection apparatus of claim 1, wherein the sensor includes a verification module configured to analyze the electromagnetic field passed through the object to determine whether characteristics of the electromagnetic field passed through the object are associated with a live finger.

13. The detection apparatus of claim 12, wherein the verification module is further configured to retrieve and compare electromagnetic field characteristics associated with a known user'"'"'s fingerprint.

14. The detection apparatus of claim 1, wherein the object comprises a finger and further comprising a fingerprint sensor configured to read a fingerprint pattern associated with the finger, and wherein live finger detection and fingerprint sensing are performed at the same time.

15. A detection apparatus comprising:

a plurality of drive plates disposed on a substrate and configured to transmit radio frequency energy to a plurality of drive plate contact points formed by an array of the plurality of drive plates;

a first pickup plate disposed on the substrate separated from each respective drive plate contact point by an injection gap, each respective drive plate and the pickup plate configured to transform the radio frequency energy into an electromagnetic field extending between the respective drive plate contact point and the first pickup plate extending across the respective injection gap, and the pickup plate and configured to receive a modified electromagnetic field, modified by passing through an object spanning the respective injection gap;

a second pickup plate disposed on the substrate separated from each respective drive plate contact point by an injection gap, each respective drive plate and the pickup plate configured to transform the radio frequency energy into an electromagnetic field extending between the respective drive plate and the second pickup plate extending across the respective injection gap, and the pickup plate and configured to receive a modified electromagnetic field modified by passing through the object spanning the respective injection gap; and

a sensor coupled to the first pickup plate and the second pickup plate, the sensor configured to determine whether the object is a live finger based on the detected first and second intensities of the electromagnetic field passing through the object and received at the pickup plate.

16. The detection apparatus of claim 15, further comprising a differential receiver coupled to the first pickup plate and the second pickup plate, the differential receiver configured to determine a difference between the first intensity and the second intensity.

17. The detection apparatus of claim 15, wherein the sensor includes a verification module configured to analyze the first intensity and the second intensity to determine whether at least one characteristic of the electromagnetic field passing through the object is associated with a live finger.

18. The detection apparatus of claim 15, wherein the object comprises a finger and further comprising a fingerprint sensor configured to read a fingerprint pattern associated with the finger, wherein live finger detection and fingerprint sensing are performed at the same time.

19. An apparatus comprising:

a plurality of radio frequency energy sources configured to transmit radio frequency energy to a respective one of a plurality of drive plate contact points in an array of drive plate contact points; and

at least one pickup plate separated from each respective radio frequency energy source at each drive plate contact point by an injection gap, each respective radio frequency energy source and the respective pickup plate configured to transform the radio frequency energy into an electromagnetic field extending between the respective radio frequency energy source and pickup plate extending across the respective injection gap, and the pickup plate configured to receive a modified electromagnetic field, modified by passing through an object spanning the respective injection gap a live finger sensor proximate at least one injection gap, the live finger sensor configured to detect a characteristic associated with the electromagnetic field passing through the object and to determine whether the object is a live finger based on the at least one characteristic of the electromagnetic field passing through the object.

20. The apparatus of claim 19, wherein the radio frequency energy source is a drive plate.

21. The apparatus of claim 19, wherein the live finger sensor includes a pickup plate proximate the radio frequency energy source and an RF sensor coupled to the pickup plate.

22. The apparatus of claim 21, further comprising a verification module coupled to the RF sensor and configured to analyze the electromagnetic field passing through the object to determine whether the at least one characteristic of the electromagnetic field passing through the object is associated with a live finger.

23. The apparatus of claim 19, wherein the live finger sensor includes a first pickup plate configured to detect a first intensity associated with the electromagnetic field, and a second pickup plate configured to detect a second intensity associated with the electromagnetic field.

24. The apparatus of claim 19, wherein the object comprises a finger and further comprising a fingerprint sensor configured to read a fingerprint pattern associated with the object, wherein live finger detection and fingerprint sensing are performed at the same time.

25. A method comprising:

injecting a radio frequency signal into a plurality of drive plates configured to transmit radio frequency energy to a respective one of a plurality of drive plate contact points in an array of drive plate contact points;

detecting with a pickup plate, separated from each respective drive plate contact point by an injection gap, each respective drive plate and the pickup plate configured to transform the radio frequency energy into an electromagnetic field extending between the respective drive plate and the pickup plate across the respective injection gap, and the pickup plate configured to receive a modified-electromagnetic field, modified by passing through an object spanning the respective injection gap; and

determining with a sensor coupled to the pickup plate whether the object is a live finger based on at least one characteristic of the electromagnetic field passing through the object and received at the pickup plate.

26. The method of claim 25, wherein an intensity of the electromagnetic field is detected at a predetermined distance from a surface of the object.

27. The method of claim 25, further comprising generating a signal indicating whether the object is a live finger.

28. The method of claim 25, wherein the radio frequency signal has a frequency in the range of 10-30 MHz.

29. A non-transitory machine readable medium storing instructions that, when executed by a computing device, cause the computing device to perform a method, the method comprising:

injecting a radio frequency signal into a plurality of drive plates configured to transmit radio frequency energy to a respective one of a plurality of drive plate contact points in an array of drive plate contact points;

detecting from a pickup plate, separated from each respective drive plate contact point by an injection gap, each respective drive plate and the pickup plate configured to transform the radio frequency energy into an electromagnetic field extending between the respective drive plate and the pickup plate extending across the respective injection gap, a modified electromagnetic field, modified by passing through an object spanning the respective pixel gap; and

determining whether the object is a live finger based on at least one characteristic of the electromagnetic field passing through the object received from a sensor coupled to the pickup plate.