Apparatus and method for finger activity on a fingerprint sensor

• US 8,593,160 B2
• Filed: 09/13/2012
• Issued: 11/26/2013
• Est. Priority Date: 01/15/2009
• Status: Active Grant

• Current Assignee: Synaptics Incorporated
• Original Assignee: Validity Sensors Incorporated (Synaptics Incorporated)
• Inventors: Thompson, Erik Jonathon, Dean, Gregory Lewis, Jandu, Jaswinder, Erhart, Richard Alexander
• Primary Examiner(s): Vazquez, Arleen M
• Assistant Examiner(s): LE, SON T
• Application Number:
  US13/614,665
• Publication Number:
  US 20130021044A1
• Time in Patent Office: 439 Days
• Field of Search: 382/124, 345173-174, 324/658, 324/686
• US Class Current: 324/658
• 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 biometric object on or in the vicinity of a biometric object sensing area in a biometric object imaging apparatus, the method comprising:

transmitting a probing signal to the biometric object sensing area, comprising a capacitive gap between at least one of a plurality of transmitter electrodes and a single receiver electrode or at least one of a plurality of receiver electrodes and a single transmitter electrode, the probing signal comprising a burst of high frequency pulses, transmitted across the capacitive gap between the at least one of a transmitter electrode from the plurality of transmitter electrodes to the single receiver electrode or to the at least one of a plurality of receiver electrodes from the single transmitter electrode;

receiving a response signal on the respective receiver electrode in response to the probing signal, the response signal comprising a burst of high frequency pulses;

establishing an upper reference level for the amplitude of pulses in the burst of high frequency pulses comprising the response signal; and

monitoring whether the peaks of the response signal exceed the upper reference level to determine the presence of the biometric object in the biometric object sensing area due to the presence of the biometric object modifying the amplitude of the pulses in the burst of high frequency pulses in the response signal from the amplitude of the pulses in the probing signal.

2. The method of claim 1 further comprising:

the amplitude of each pulse in the response signal being determined at least in part by the modification of the high frequency capacitive impedance across the capacitive gap due to the presence of the finger in the vicinity of the capacitive gap.

3. The method of claim 1 further comprising:

establishing a lower reference signal; and

monitoring whether the peaks of the response signal are below the lower reference level to determine the absence of the biometric object in the biometric object sensing area due to the lack of presence of the biometric object modifying the amplitude of the pulses in the high frequency response signal.

4. The method of claim 1 further comprising:

the amplitude of each pulse in the response signal being determined at least in part by the modification of the high frequency capacitive impedance across the capacitive gap due to the lack of presence of the finger in the vicinity of the capacitive gap.

5. The method of claim 2 further comprising:

setting a power consumption mode of operation of the biometric object imaging apparatus at least in part based on the determination of the presence of the biometric object.

6. The method of claim 4 further comprising:

setting a power consumption mode of operation of the biometric object imaging apparatus at least in part based on the determination of the absence of the biometric object.

7. The method of claim 1 further comprising:

the capacitive gap comprises a respective one the gaps between each of the plurality of transmitter electrodes and the single receiver electrode defining a pixel location at the location of the respective one of the gaps.

8. The method of claim 1 further comprising:

the capacitive gap comprises a respective one the gaps between each of the plurality of receiver electrodes and the single transmitter electrode defining a pixel location at the location of the respective one of the gaps.

9. The method of claim 1 further comprising:

the burst of high frequency pulses comprising a burst of RF pulses, transmitted across the capacitive gap from a transmitter electrode to a receiver electrode defining a pixel location at the gap between the transmitter electrode and the receiver electrode.

10. The method of claim 1 further comprising:

the biometric object comprises a finger and the biometric object imaging apparatus comprises a fingerprint imaging apparatus.

11. A biometric object sensor in a biometric object imaging apparatus, comprising:

a probing signal generator configured to generate a probing signal and transmit the probing signal to a biometric object sensing area, comprising a capacitive gap between at least one of a plurality of transmitter electrodes and a single receiver electrode or at least one of a plurality of receiver electrodes and a single transmitter electrode, the probing signal comprising a burst of high frequency pulses, transmitted across the capacitive gap between the at least one of a transmitter electrode from the plurality of transmitter electrodes to the single receiver electrode or the at least one of a plurality of receiver electrodes from the single transmitter electrode;

a response signal receiver receiving a response signal on the respective receiver electrode in response to the probing signal, the response signal comprising a burst of high frequency pulses;

a reference signal generator generating an upper reference level signal for the amplitude of pulses in the burst of high frequency pulses comprising the response signal; and

a signal processor configured to monitor whether the peaks of the response signal exceed the upper reference level to determine the presence of the biometric object in the biometric object sensing area due to the presence of the biometric object modifying the amplitude of the pulses in the burst of high frequency pulses in the response signal from the amplitude of the pulses in the probing signal.

12. The sensor of claim 11 further comprising:

the amplitude of each pulse in the response signal being determined at least in part by the modification of the high frequency capacitive impedance across the capacitive gap due to the presence of the biometric object in the vicinity of the capacitive gap.

13. The sensor of claim 11 further comprising:

a reference signal generator generating a lower reference signal; and

the signal processor monitoring whether the peaks of the response signal are below the lower reference level to determine the absence of the biometric object from the biometric object sensing area due to the lack of presence of the biometric object modifying the amplitude of the pulses in the high frequency response signal.

14. The sensor of claim 11 further comprising:

the amplitude of each pulse in the response signal being determined at least in part by the modification of the high frequency capacitive impedance across the capacitive gap due to the lack of presence of the biometric object in the vicinity of the capacitive gap.

15. The sensor of claim 12 further comprising:

a computing device configured to set a power consumption mode of operation of the biometric object imaging apparatus at least in part based on the determination of the presence of the biometric object.

16. The sensor of claim 14 further comprising:

a computing device configured to set a power consumption mode of operation of the biometric object imaging apparatus at least in part based on the determination of the absence of the biometric object.

17. The sensor of claim 11 further comprising:

the capacitive gap comprises a respective one the gaps between each of the plurality of transmitter electrodes and the single receiver electrode defining a pixel location at the location of the respective one of the gaps.

18. The sensor of claim 11 further comprising:

the capacitive gap comprises a respective one the gaps between each of the plurality of receiver electrodes and the single transmitter electrode defining a pixel location at the location of the respective one of the gaps.

19. The sensor of claim 11 further comprising:

the burst of high frequency pulses comprising a burst of RF pulses, transmitted across the capacitive gap from a transmitter electrode to a receiver electrode defining a pixel location at the gap between the transmitter electrode and the receiver electrode.

20. 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:

transmit a probing signal to a biometric object sensing area, comprising a capacitive gap between at least one of a plurality of transmitter electrodes and a single receiver electrode or at least one of a plurality of receiver electrodes and a single transmitter electrode, the probing signal comprising a burst of high frequency pulses, transmitted across the capacitive gap between the transmitter electrode of the plurality of transmitter electrodes to the single receiver electrode or to the receiver electrode of the plurality of receiver electrodes from the single transmitter electrode;

receive a response signal on the respective receiver electrode in response to the probing signal, the response signal comprising a burst of high frequency pulses;

establish an upper reference level for the amplitude of pulses in the burst of high frequency pulses comprising the response signal; and

monitor whether the peaks of the response signal exceed the upper reference level to determine the presence of the biometric object in the biometric object sensing area due to the presence of the biometric object modifying the amplitude of the pulses in the burst of high frequency pulses in the response signal from the amplitude of the pulses in the probing signal.