Apparatus and method for detecting finger activity on a fingerprint sensor
View Patent ↗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.
1. A method comprising:
placing a fingerprint sensor in one of a wait-for-event and a wake-on-event mode;
transmitting a probing signal to a fingerprint sensing transmitting element, comprising one of a stand alone wake-up transmitting element and a fingerprint sensing wake-up transmitting element, selected from a plurality of fingerprint sensing transmitting elements and selectively kept active, while the remaining fingerprint sensing transmitting elements of the plurality of fingerprint sensing transmitting elements are in a non-active mode, to reduce power consumption by the fingerprint sensor;
receiving a response signal from one of the stand alone wake-up transmitting element and the fingerprint sensing wake-up transmitting element at a fingerprint sensing receiving element;
monitoring the response signal on the fingerprint sensing receiving element to determine if a finger is present in a fingerprint sensing area; and
removing the fingerprint sensor from the one of the wait-for-event and the wake-on-event mode in response to the response signal.
2. The method of claim 1 , further comprising determining whether a finger has been placed on the fingerprint sensing area based on the relation of peaks of the response signal to an upper reference signal.
3. The method of claim 2 , further comprising counting the number of peaks of the response signal that 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 peaks of the response signal that exceed the upper reference signal.
5. The method of claim 1 , further comprising establishing a lower reference signal and monitoring the peaks of the response signal in relation to 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 the relation of the peaks of the response signal to the lower reference signal.
7. The method of claim 6 , further comprising counting the number of peaks of the response signal that 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 peaks of the response signal that 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 transmitting element in bursts, separated by idle time.
11. A fingerprint detecting sensor, comprising:
a transmitter configured to transmit a probing signal to a fingerprint sensing transmitting element, comprising one of a stand alone wake-up transmitting element and a fingerprint sensing wake-up transmitting element, selected from a plurality of fingerprint sensing transmitting elements and selectively kept active while the remaining fingerprint sensing transmitting elements of the plurality of fingerprint sensing transmitting elements are placed in a non-active mode, to reduce power consumption by the fingerprint detecting sensor;
a fingerprint sensing receiving element configured to receive a response signal, from one of the stand alone wake-up transmitting element and the fingerprint scanner wake-up transmitting element at the receiving element;
a first signal generator configured to generate an upper reference signal; and
a detector configured to monitor the response signal in relation to the upper reference signal.
12. The sensor of claim 11 , further comprising detection logic configured to determine whether a finger has been placed on the fingerprint sensor based on the relation of peaks of the response signal to the upper reference signal.
13. The sensor of claim 12 , further comprising a counter configured to count the number of peaks of the response signal exceeding the upper reference signal.
14. The sensor of claim 13 , wherein the detection logic is further configured to determine whether a finger has been placed on the fingerprint sensor based on the number of peaks that exceed the upper reference signal.
15. The sensor of claim 11 , further comprising a second signal generator configured to generate a lower reference signal.
16. The sensor of claim 15 , wherein the detection logic is further configured to monitor the relation of peaks of the response signal to the lower reference signal.
17. The sensor of claim 16 , further comprising the detection logic is further configured to determine whether a finger has been removed from the fingerprint sensor based on the relation of the peaks to the lower reference signal.
18. The apparatus of claim 17 , further comprising a counter configured to count the number of peaks that 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 peaks that drop below the lower reference signal waves.
20. The apparatus of claim 11 , wherein the probing pulses are square waves.
21. The apparatus of claim 11 , wherein the transmitter is further configured to emit the probing pulses in bursts, separated by idle time.
22. An fingerprint sensor comprising:
probing signal transmitting means for transmitting a probing signal to a fingerprint sensing transmitting element, comprising one of a stand alone wake-up transmitting element and a fingerprint sensing wake-up transmitting element, selected from a plurality of fingerprint sensing transmitting elements and selectively kept active while the remaining fingerprint sensing transmitting elements of the plurality of fingerprint sensing transmitting elements are in a non-active mode, to reduce power consumption by the fingerprint sensor;
fingerprint sensing receiving means for receiving response signal from one of the stand alone wake-up transmitting element and the fingerprint scanner wake-up transmitting element at a fingerprint sensing receiving element;
reference generating means for establishing an upper reference signal; and
monitoring means for monitoring the response signal from the fingerprint sensing receiving element to determine if a finger is present in a fingerprint sensing area.
23. The fingerprint sensor of claim 22 , further comprising logic means for determining whether a finger has been placed on the fingerprint sensor based on the relation of the response signal to the upper reference signal.
24. The fingerprint sensor of claim 23 , further comprising counting means for counting a number of peaks in the response signal that exceed the upper reference signal.
25. The fingerprint sensor of claim 24 , further comprising logic means for determining whether a finger has been placed on the fingerprint sensor based on the number of peaks that exceed the upper reference signal.
26. The fingerprint sensor of claim 22 , further comprising generating means for generating a lower reference signal and monitoring means for monitoring the relation of the response signal to the lower reference signal.
27. The fingerprint sensor of claim 26 , further comprising logic means for determining whether a finger has been removed from the fingerprint sensing area based on the relation of the peaks to the lower reference signal.
28. The fingerprint sensor of claim 27 , further comprising counting means for counting the number of response signal that drop below the lower reference signal.
29. The fingerprint sensor of claim 28 , further comprising logic means for determining whether a finger has been removed from the fingerprint sensing area based on the number of peaks that drop below the lower reference signal.
30. A tangible machine readable medium storing instructions that, when executed by a computing device, cause the computing device to perform a method, the method comprising:
transmitting a probing signal to a fingerprint sensing transmitting element, comprising one of a stand alone wake-up transmitting element and a fingerprint sensor fingerprint sensing wake-up transmitting element, selected from a plurality of fingerprint sensing transmitting elements and selectively kept active, while the remaining fingerprint sensing transmitting elements of the plurality of fingerprint sensing transmitting elements are placed in a non-active mode, to reduce power consumption by the fingerprint sensor;
receiving a response signal from one of the stand alone wake-up transmitting element and the fingerprint scanner wake-up transmitting element at a fingerprint sensing receiving element;
and monitoring the signal from the fingerprint sensing receiving element to determine if a finger is present in a fingerprint sensing area.