Apparatus and Method for Detecting Finger Activity on a Fingerprint Sensor

• US 20100176823A1
• Filed: 01/15/2009
• Published: 07/15/2010
• Est. Priority Date: 01/15/2009
• Status: Active Grant

• Current Assignee: Synaptics Incorporated
• Original Assignee: Validity Sensors Incorporated (Synaptics Incorporated)
• Inventors: Dean, Gregory Lewis, Jandu, Jaswinder, Thompson, Erik Jonathon, Erhart, Richard Alexander
• Granted Patent: US 8,278,946 B2
• Time in Patent Office: Days
• US Class Current: 324/676
• CPC Class Codes: G06F 1/1684 Constructional details or arrangements related to integrated I/O peripherals not covered by groups G06F1/1635 - G06F1/1675
• CPC Class Codes: G06F 1/325 Power saving in peripheral device
• 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

An apparatus and method for detecting the presence of a finger on a fingerprint sensor is disclosed in one embodiment of the invention as including transmitting a probing signal, comprising a series of probing pulses, to a fingerprint sensing area. A response signal, comprising a series of response pulses, is received from the fingerprint sensing area in response to the probing signal. An upper reference signal is generated and finger activity is detected on the fingerprint sensing area by monitoring whether the peaks of the response pulses exceed the reference signal.

Claims

1. A method for detecting the presence of a finger on a fingerprint sensor, the method comprising:

transmitting a probing signal to a fingerprint sensing area, the probing signal comprising a series of probing pulses;

receiving a response signal from the fingerprint sensing area in response to the probing signal, the response signal comprising a series of response pulses;

establishing an upper reference signal; and

monitoring whether the peaks of the response pulses exceed the upper reference signal.

2. The method of claim 1, further comprising determining whether a finger has been placed on the fingerprint sensing area based on whether the peaks exceed the upper reference signal.

3. The method of claim 2, further comprising counting the number of times the peaks exceed the upper reference signal.

4. The method of claim 3, further comprising determining whether a finger has been placed on the fingerprint sensing area based on the number of times the peaks exceed the upper reference signal.

5. The method of claim 1, further comprising establishing a lower reference signal below the peaks and monitoring whether the peaks drop below the lower reference signal.

6. The method of claim 5, further comprising determining whether a finger has been removed from the fingerprint sensing area based on whether the peaks drop below the lower reference signal.

7. The method of claim 6, further comprising counting the number of times the peaks drop below the lower reference signal.

8. The method of claim 7, further comprising determining whether a finger has been removed from the fingerprint sensing area based on the number of times the peaks drop below the lower reference signal.

9. The method of claim 1, wherein the probing pulses are square waves.

10. The method of claim 1, wherein the probing pulses are transmitted to the fingerprint sensing area in bursts, separated by idle time.

11. An apparatus for detecting the presence of a finger on a fingerprint sensor, the apparatus comprising:

a transmitter element to emit a probing signal at a fingerprint sensing area, the probing signal comprising a series of probing pulses;

a receiving element to receive a response signal from the fingerprint sensing area in response to the probing signal, the response signal comprising a series of response pulses;

a first signal generator to generate an upper reference signal; and

a detector to monitor whether the peaks of the response pulses exceed the upper reference signal.

12. The apparatus of claim 11, further comprising detection logic to determine whether a finger has been placed on the fingerprint sensing area based on whether the peaks exceed the upper reference signal.

13. The apparatus of claim 12, further comprising a counter to count the number of times the peaks exceed the upper reference signal.

14. The apparatus of claim 13, wherein the detection logic is further configured to determine whether a finger has been placed on the fingerprint sensing area based on the number of times the peaks exceed the upper reference signal.

15. The apparatus of claim 11, further comprising a second signal generator to generate a lower reference signal.

16. The apparatus of claim 15, wherein the detector is further configured to monitor whether the peaks drop below the lower reference signal.

17. The apparatus of claim 16, further comprising detection logic to determine whether a finger has been removed from the fingerprint sensing area based on whether the peaks drop below the lower reference signal.

18. The apparatus of claim 17, further comprising a counter to count the number of times the peaks drop below the lower reference signal.

19. The apparatus of claim 18, wherein the detection logic is further configured to determine whether a finger has been removed from the fingerprint sensing area based on the number of times the peaks drop below the lower reference signal.

20. The apparatus of claim 11, wherein the probing pulses are square waves.

21. The apparatus of claim 11, wherein the transmitter element emits the probing pulses in bursts, separated by idle time.

22. An apparatus for detecting the presence of a finger on a fingerprint sensor, the apparatus comprising:

means for transmitting a probing signal to a fingerprint sensing area, the probing signal comprising a series of probing pulses;

means for receiving a response signal from the fingerprint sensing area in response to the probing signal, the response signal comprising a series of response pulses;

means for establishing an upper reference signal; and

means for monitoring whether the peaks of the response pulses exceed the upper reference signal.

23. The apparatus of claim 22, further comprising means for determining whether a finger has been placed on the fingerprint sensing area based on whether the peaks exceed the upper reference signal.

24. The apparatus of claim 23, further comprising means for counting the number of times the peaks exceed the upper reference signal.

25. The apparatus of claim 24, further comprising means for determining whether a finger has been placed on the fingerprint sensing area based on the number of times the peaks exceed the upper reference signal.

26. The apparatus of claim 22, further comprising means for generating a lower reference signal and means for monitoring whether the peaks drop below the lower reference signal.

27. The apparatus of claim 26, further comprising means for determining whether a finger has been removed from the fingerprint sensing area based on whether the peaks drop below the lower reference signal.

28. The apparatus of claim 27, further comprising means for counting the number of times the peaks drop below the lower reference signal.

29. The apparatus of claim 28, further comprising means for determining whether a finger has been removed from the fingerprint sensing area based on the number of times the peaks drop below the lower reference signal.