Fingerprint sensor employing an integrated noise rejection structure
First Claim
1. A fingerprint sensor system, comprising:
- a plurality of substantially parallel drive lines;
a plurality of substantially parallel pickup lines oriented transversely to the plurality of drive lines;
an insulating layer separating the plurality of pickup lines from the plurality of drive lines;
a plurality of electrode pairs, each electrode pair being defined at a location where a pickup line crosses a drive line, wherein each electrode pair has an impedance that is sensitive to an object contacting or in close proximity to the electrode pair;
one or more reference pickup line(s) oriented substantially parallel with the plurality of pickup lines;
one or more compensation drive line(s) oriented substantially parallel with the drive lines and crossing the pickup lines and the reference pickup line(s) to capacitively couple the compensation drive line(s) into the pickup lines and the reference pickup line(s);
a reference pickup drive line crossing the reference pickup line to capacitively couple the reference pickup line and the reference pickup drive line;
wherein each electrode pair has a first impedance when no object is contacting or in close proximity to the electrode pair and wherein the drive lines, the pickup lines, the reference pickup line, the compensation drive line, and the reference pickup drive line are configured such that a second impedance between the compensation drive line and a crossing pickup line, a third impedance between the reference pickup line and a crossing reference pickup drive line, and a fourth impedance between the compensation drive line and the reference pickup line are equal to the first impedance;
a signal source configured to provide a first signal to one of the drive lines and the reference pickup drive line and to provide a second signal to the compensation drive line, where the second signal is a fixed reference amplitude phase inverted relative to the first signal; and
a differential amplifier having a first input, a second input, and an output, wherein the first input is connected to a pickup line, the second input is connected to one or more of the reference pickup line(s), and the output of the differential amplifier is indicative of the presence of ridge and valley features of a finger contacting or in close proximity to one or more of the electrode pairs.
2 Assignments
0 Petitions
Accused Products
Abstract
A sensor has drive lines and transverse pickup lines to define an electrode pair where each pickup line crosses a drive line. A reference pickup line is arranged parallel to the pickup lines and a compensation drive line is arranged parallel to the drive lines. A signal source provides a first signal to the drive lines and a second signal that is the inverse of the first signal to the compensation drive line. An amplifier has a first input connected to a pickup line, a second input connected to a reference pickup line, and a output indicative of an object in contact with the electrode pair(s). Each impedance between the compensation drive line and a pickup line, between the reference pickup line and a reference drive line, and between the compensation drive line and the reference pickup line is equal to the impedance at the electrode pair when no object is contact with the electrode pair.
59 Citations
46 Claims
-
1. A fingerprint sensor system, comprising:
a plurality of substantially parallel drive lines; a plurality of substantially parallel pickup lines oriented transversely to the plurality of drive lines; an insulating layer separating the plurality of pickup lines from the plurality of drive lines; a plurality of electrode pairs, each electrode pair being defined at a location where a pickup line crosses a drive line, wherein each electrode pair has an impedance that is sensitive to an object contacting or in close proximity to the electrode pair; one or more reference pickup line(s) oriented substantially parallel with the plurality of pickup lines; one or more compensation drive line(s) oriented substantially parallel with the drive lines and crossing the pickup lines and the reference pickup line(s) to capacitively couple the compensation drive line(s) into the pickup lines and the reference pickup line(s); a reference pickup drive line crossing the reference pickup line to capacitively couple the reference pickup line and the reference pickup drive line; wherein each electrode pair has a first impedance when no object is contacting or in close proximity to the electrode pair and wherein the drive lines, the pickup lines, the reference pickup line, the compensation drive line, and the reference pickup drive line are configured such that a second impedance between the compensation drive line and a crossing pickup line, a third impedance between the reference pickup line and a crossing reference pickup drive line, and a fourth impedance between the compensation drive line and the reference pickup line are equal to the first impedance; a signal source configured to provide a first signal to one of the drive lines and the reference pickup drive line and to provide a second signal to the compensation drive line, where the second signal is a fixed reference amplitude phase inverted relative to the first signal; and a differential amplifier having a first input, a second input, and an output, wherein the first input is connected to a pickup line, the second input is connected to one or more of the reference pickup line(s), and the output of the differential amplifier is indicative of the presence of ridge and valley features of a finger contacting or in close proximity to one or more of the electrode pairs. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25)
-
26. A fingerprint sensor system, comprising:
-
a plurality of substantially parallel drive lines; a plurality of substantially parallel pickup lines oriented transversely to the plurality of drive lines to capacitively couple each pickup line to a drive line at each location where a pickup line crosses a drive line; an insulating layer separating the plurality of pickup lines from the plurality of drive lines; a reference pickup line oriented substantially parallel with the pickup lines; a compensation drive line oriented substantially parallel with the drive lines and crossing the pickup lines and the reference pickup line to capacitively couple the compensation drive line with the pickup lines and the reference pickup line; a reference pickup drive line crossing the reference pickup line to capacitively couple the reference pickup line and the reference pickup drive line; a signal source configured to provide a first signal to one of the drive lines and the reference pickup drive line and to provide a second signal to the compensation drive line, where the second signal is the inverse of the first signal; and a differential amplifier having a first input, a second input, and an output, wherein the first input is connected to a pickup line, thereby coupling (a) the first signal to the first input via the pickup line and a capacitively-coupled drive line and (b) the second signal to the first input via the pickup line and the capacitively-coupled compensation drive line, and wherein the second input is connected to the reference pickup line, thereby coupling (a) the first signal to the second input via reference pickup line and the capacitively-coupled reference pickup drive line and (b) the second signal to the second input via the reference pickup line and the capacitively-coupled compensation drive line, and the output of the differential amplifier is substantially free of common mode noise. - View Dependent Claims (27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46)
-
Specification