HIGH RESOLUTION FINGERPRINT IMAGING DEVICE
First Claim
1. A fingerprint sensor pixel comprising:
- a capacitive sensor, wherein a capacitance of the capacitive sensor changes in response to contact with the valley or the ridge a fingerprint; and
a readout circuit comprising;
a first thin film transistor (TFT) having a gate terminal, a drain terminal, and a source terminal, wherein the gate terminal of the first TFT is coupled to the capacitive sensor; and
a coupling capacitor having a first terminal and a second terminal, wherein the first terminal of the coupling capacitor is coupled to the gate terminal of the first TFT,wherein the readout circuit is configured to generate, in response to a voltage applied to the second terminal of the coupling capacitor, a current flow between the drain terminal of the first TFT and the source terminal of the first TFT representative of the capacitance of the capacitive sensor.
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Accused Products
Abstract
A fingerprint sensor pixel and fingerprint imaging device are disclosed. A fingerprint sensor pixel includes a capacitive sensor and a readout circuit. The capacitance of the capacitive sensor changes in response to contact with a fingerprint. The readout circuit includes a first thin film transistor (TFT) used to convert the capacitance of the capacitive sensor to a representative current, a coupling capacitor used to capacitively couple a readout pulse to the gate of the said second TFT sharing the connection with the capacitive sensor pixel, and a second TFT used to reset the voltage of the capacitive sensor. Multiple fingerprint sensor pixels can be arranged in an array to form a fingerprint imaging device.
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Citations
21 Claims
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1. A fingerprint sensor pixel comprising:
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a capacitive sensor, wherein a capacitance of the capacitive sensor changes in response to contact with the valley or the ridge a fingerprint; and a readout circuit comprising; a first thin film transistor (TFT) having a gate terminal, a drain terminal, and a source terminal, wherein the gate terminal of the first TFT is coupled to the capacitive sensor; and a coupling capacitor having a first terminal and a second terminal, wherein the first terminal of the coupling capacitor is coupled to the gate terminal of the first TFT, wherein the readout circuit is configured to generate, in response to a voltage applied to the second terminal of the coupling capacitor, a current flow between the drain terminal of the first TFT and the source terminal of the first TFT representative of the capacitance of the capacitive sensor. - View Dependent Claims (2, 3, 4)
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5. A fingerprint imaging device comprising:
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a plurality of fingerprint sensor pixels forming a two-dimensional fingerprint sensor array, each fingerprint sensor pixel of the plurality of fingerprint sensor pixels comprising; a capacitive sensor, wherein the capacitance of the capacitive sensor changes in response to contact with a fingerprint; and a readout circuit comprising; a first thin film transistor (TFT) having a gate terminal, a drain terminal, and a source terminal, wherein the gate terminal of the first TFT is coupled to the capacitive sensor; and a coupling capacitor having a first terminal and a second terminal, wherein the first terminal of the coupling capacitor is coupled to the gate terminal of the first TFT, wherein the readout circuit is configured to generate, in response to a voltage applied to the second terminal of the coupling capacitor, a current flow between the drain terminal of the first TFT and the source terminal of the first TFT representative of the capacitance of the capacitive sensor. - View Dependent Claims (6, 7, 8, 9, 10, 11, 12)
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13. A fingerprint imaging device comprising:
a plurality of fingerprint sensor pixels forming a two-dimensional fingerprint sensor array, each sensor pixel including; a capacitive sensor, wherein the capacitance of the capacitive sensor changes in response to contact with a fingerprint; a first transistor coupled to the capacitive sensor at a first node, said first transistor for amplifying the change in capacitance of the capacitive sensor; a coupling capacitor coupled to the first node, said coupling capacitor being responsive to a scan signal which causes the first transistor to generate an output proportional to the change in capacitance of the capacitive sensor; and a reset transistor coupled to the first node and responsive to a reset signal for resetting the voltage of the first node. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21)
Specification