System and method for improving sensor image quality

Abstract

Systems and methods for detecting a user's finger or other element may be provided. In some embodiments, the system may include a plurality of electrode groups, and each electrode group may include a corresponding reference electrode whose true signal value is a predetermined value. In some embodiments, the system may process the signal received by the electrode group in the following manner: (a) modulating the signal received from each electrode in the corresponding electrode group according to a modulation mode; (b) demodulating the signal received from each electrode in the corresponding electrode group or the value derived from the signal according to a demodulation mode, thereby determining a set of demodulated values ​​of the corresponding electrode group; and / or (c) using the predetermined value of the reference electrode of the corresponding electrode group, restoring the average value to the signal received from each electrode in the corresponding electrode group or the value derived from the signal.

Description

[0001] Related Applications

[0002] This application claims priority to U.S. Patent Application No. 16 / 108,875 and U.S. Patent Application No. 16 / 547,802, the contents of which are incorporated herein by reference as if set forth in their entirety.

[0003] Public domain

[0004] The present disclosure relates to sensors for electronically sensing the position of an object (eg, a finger or feature thereof) located near or around the sensor.

[0005] background

[0006] The sensor can be used to detect the presence of an object located near or around the sensor. Such a sensor can be configured to sense electrical properties of an object, to sense the presence or location of an object near or around the sensor, physical properties of an object, shape, texture, material composition, biological information on the surface of an object, and other features and characteristics of the sensed object. For example, the sensor can be configured to detect the presence or location of a user's finger, or in the case of a fingerprint sensor example, to detect one or more features (e.g., ridges) of a user's finger.

[0007] For some sensors, a body part (e.g., a finger) may be positioned near the sensor or in contact with the sensor in order to perform a measurement. In some cases, the sensor may apply a carrier signal that may be modulated when the body part is placed near the sensor. The sensor may then receive the modulated carrier signal. Because the modulation—rather than the carrier itself—contains the information of interest, this may be beneficial to cancel or compensate for the carrier. For example, this may allow the dynamic range of the sensor to be better used to detect the modulation applied by the body part, thereby improving the accuracy of the sensor.

[0008] However, certain challenges may arise when the carrier is eliminated or compensated. In particular, when reconstructing a digital image for analysis, it may be necessary to recover the common mode portion of the signal. In addition, electrical coupling between adjacent electrodes may produce blurring in the reconstructed digital image. Therefore, there is a need for systems and methods that address these and other challenges as described more fully below.

[0009] Overview

[0010] A brief summary is presented below in order to provide a basic understanding of some aspects described herein. This summary is not an extensive overview of the claimed subject matter. It is neither intended to identify the key or critical elements of the claimed subject matter nor to delineate its scope. Its sole purpose is to present some concepts in a simple form as a prelude to a more detailed description that is presented later.

[0011] In some embodiments, a system for detecting a user's finger or other element may be provided. The system may include a memory, a sensor area, and a processor. The sensor area may include a receiving electrode set, and the receiving electrode set may include multiple electrode groups. The system may be configured to process a signal received by an electrode group, wherein, for each corresponding electrode group, the step of processing the signal includes: (a) modulating the signal received from each electrode in the corresponding electrode group according to a modulation mode, and (b) demodulating the signal received from each electrode in the corresponding electrode group or the value derived from the signal according to a demodulation mode, thereby determining a set of demodulated values ​​of the corresponding electrode group. The modulation mode and the demodulation mode may be selected so that steps (a) and (b) remove the average value from the signal received by the electrode in each corresponding electrode group. The system may also be configured to add a global recovery value to the demodulated value. In some embodiments, a recovery value may be selected to compensate for the removed average value. For each electrode in a plurality of electrode groups, the recovery value may be the same.

[0012] In some embodiments, the sensor area may be defined by a frame. The first electrode group may include a first electrode and a second electrode, and the first electrode and the second electrode are arranged in the sensor area so that no electrode in the first electrode group is disposed between the first electrode and the second electrode. In some embodiments, a plurality of electrode groups may be at least partially staggered so that one or more electrodes in the electrode set are disposed between the first electrode and the second electrode. In some embodiments, the value Y may represent the number of electrodes in the receiving electrode set. The value N may represent the number of electrodes in the first electrode group. The value Z may be one greater than the number of electrodes disposed between the first electrode and the second electrode, and Y may be less than or equal to 2NZ. In some embodiments, Z may be less than or equal to 6. In some embodiments, N is greater than or equal to 23. In some embodiments, Y may be less than or equal to 1.1NZ.

[0013] In some embodiments, a system for detecting a user's finger or other element may be provided. The system may include a memory, a sensor area, and a processor. The sensor area may be defined by a frame and may include a set of receiving electrodes. The set of receiving electrodes may include all receiving electrodes of the sensor area. The receiving electrodes in the set may be divided between a plurality of electrode groups including at least a first electrode group and a second electrode group. The system may be configured to process signals received by the electrode groups. For each corresponding electrode group, the step of processing the signal may include: (a) modulating the signal received from each electrode in the corresponding electrode group according to a modulation mode, and (b) demodulating the signal received from each electrode in the corresponding electrode group or a value derived from the signal according to a demodulation mode, thereby determining a set of demodulated values ​​of the corresponding electrode group.

[0014] In some embodiments, the first electrode group may include a first electrode and a second electrode, and the first electrode and the second electrode may be arranged in the sensor area so that no electrode in the first electrode group is disposed between the first electrode and the second electrode. Multiple electrode groups may be at least partially staggered so that one or more electrodes in the electrode set are disposed between the first electrode and the second electrode. The value Y may represent the number of electrodes in the receiving electrode set, the value N may represent the number of electrodes in the first electrode group, and the value Z may be one greater than the number of electrodes disposed between the first electrode and the second electrode. These values ​​may be selected so that Y is less than or equal to 2NZ. In some embodiments, Z may be less than or equal to 6. In some embodiments, N may be greater than or equal to 23. In some embodiments, Y may be less than or equal to 1.1NZ.

[0015] In some embodiments, a method for detecting a user's finger or other element may be provided. The method may be performed by a system including a memory, a processor, and a sensor area defined by a frame. The sensor area may include a set of receiving electrodes, the receiving electrode set including all receiving electrodes of the sensor area. The receiving electrode set may include a plurality of electrode groups, the plurality of electrode groups including at least a first electrode group and a second electrode group. The method may include, for each electrode group in the plurality of electrode groups, (a) modulating a signal received from each electrode in the corresponding electrode group according to a modulation mode, and (b) demodulating a signal received from each electrode in the corresponding electrode group or a value derived from the signal according to a demodulation mode, thereby determining a set of demodulated values ​​of the corresponding electrode group.

[0016] In some embodiments, the first electrode group may include a first electrode and a second electrode. The first electrode and the second electrode may be arranged in the sensor area so that no electrode in the first electrode group is disposed between the first electrode and the second electrode. A plurality of electrode groups may be at least partially staggered so that one or more electrodes in the electrode set are disposed between the first electrode and the second electrode. In some embodiments, the value Y may represent the number of electrodes in the receiving electrode set. The value N may represent the number of electrodes in the first electrode group. The value Z may be one greater than the number of electrodes disposed between the first electrode and the second electrode. In some embodiments, these values ​​may be selected so that Y is less than or equal to 2NZ. In some embodiments, Z may be less than or equal to 6. In some embodiments, N may be greater than or equal to 23. In some embodiments, these values ​​may be selected so that Y is less than or equal to 1.1NZ. In some embodiments, performing steps (a) and (b) with respect to the first electrode group may result in data being collected about two pixels of at least ninety percent of the length of the spaced pixel row.

[0017] In some embodiments, a system for detecting a user's finger or other element may be provided. The system may include a memory, a processor, and a plurality of electrode groups. In some embodiments, each electrode group may include a corresponding reference electrode, and the true signal value of the corresponding reference electrode is a predetermined value. The system may be configured to process the signal received by the electrode group. In some embodiments, for each corresponding electrode group, the step of processing the signal may include: (a) modulating the signal received from each electrode in the corresponding electrode group according to the modulation mode; (b) demodulating the signal received from each electrode in the corresponding electrode group or the value derived from the signal according to the demodulation mode, thereby determining the set of demodulated values ​​of the corresponding electrode group; and (c) using the predetermined value of the reference electrode of the corresponding electrode group, restoring the average value to the signal received from each electrode in the corresponding electrode group or the value derived from the signal. In some embodiments, the modulation mode and the demodulation mode may be selected so that steps (a) and (b) remove the average value from the signal received by the electrode in each corresponding electrode group.

[0018] In some embodiments, a method for detecting a user's finger or other element may be provided. In some embodiments, the method may be performed at least in part by any system described herein. For example, the system may include a plurality of electrode groups, and each electrode group in the plurality of electrode groups may include a corresponding reference electrode, the true signal value of the corresponding reference electrode being a predetermined value. In some embodiments, the method may include processing a signal received by each electrode in the corresponding electrode group by at least the following steps: (a) modulating a signal received from each electrode in the corresponding electrode group according to a modulation mode; (b) demodulating a signal received from each electrode in the corresponding electrode group or a value derived from the signal according to a demodulation mode, thereby determining a set of demodulated values ​​of the corresponding electrode group; and (c) using a predetermined value of a reference electrode in the corresponding electrode group, restoring the average value to a signal received from each electrode in the corresponding electrode group or a value derived from the signal. In some embodiments, the modulation mode and the demodulation mode may be selected so that steps (a) and (b) remove the average value from the signal received by the electrode in each corresponding electrode group.

[0019] Additional variations included in the systems and methods are described below in the detailed description of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings, which are incorporated herein and form a part of the specification, illustrate various non-limiting embodiments of the present invention. In the drawings, like reference numerals indicate identical or functionally similar elements.

[0022] Figure 1 An exemplary embodiment of a sensor area defined by a frame is depicted.

[0023] Figure 2 A schematic diagram of an exemplary sensor grid is depicted.

[0024] Figures 3A-3C Exemplary embodiments for receiving signals and processing signals are shown.

[0025] Figure 4A and Figure 4B Exemplary modulation and demodulation modes are shown.

[0026] Figures 5A-5C An exemplary electrode staggered arrangement is shown.

[0027] Figure 6 An exemplary method for obtaining data from a set of receive electrodes is shown.

[0028] Figure 7 An exemplary technique for determining respective restoration values ​​for electrode groups is shown.

[0029] Figures 8A-8B An exemplary image containing an error pattern visible in the non-contact area is shown.

[0030] Fig. 9 Exemplary techniques for generating and using segmentation masks are shown.

[0031] Figures 10A-10C An exemplary technique for isolating a region of interest using a segmentation mask is shown.

[0032] Fig.11 An exemplary technique is depicted in which grayscale clipping is used to remove non-contact regions from an image.

[0033] Figures 12A-12B An exemplary image is shown in which grayscale clipping is used to remove non-contact areas.

[0034] Fig.13 A schematic diagram of an exemplary sensor system is shown.

[0035] Fig.14 Exemplary methods for collecting data and analyzing data in a sensor system are shown.

[0036] Fig.15 An exemplary sensor arrangement with a reference electrode is shown.

[0037] Figures 16A-16B Shows the reflection Fig.15 Exemplary cross-sectional view of the arrangement shown.

[0038] Fig.17 Another exemplary sensor arrangement with a reference electrode is shown.

[0039] Fig.18 Exemplary methods for obtaining data from one or more sets of electrodes are shown.

[0040] Detailed Description

[0041] Although various aspects of the subject matter of the present disclosure can be embodied in various forms, the following description and drawings are intended to disclose only some of these forms as specific examples of the subject matter. Therefore, the subject matter of the present disclosure is not intended to be limited to the forms or embodiments described and shown as such.

[0042] Unless otherwise defined, all terms, symbols and other technical terms or special terms in the art used herein have the same meaning as those of ordinary skill in the field to which the present disclosure belongs. All patents, applications, disclosed applications and other publications cited herein are incorporated herein by reference in their entirety. If the definition set forth in this section is contrary to or inconsistent with the definition set forth in the patents, applications, disclosed applications and other publications incorporated herein by reference, the definition set forth in this section takes precedence over the definition incorporated herein by reference.

[0043] As used herein, "a" or "an" means "at least one" or "one or more" unless indicated otherwise or the context suggests otherwise.

[0044] This specification may use relative spatial and / or directional terms to describe the position and / or orientation of a component, device, position, feature, or portion thereof. Unless otherwise stated or indicated by the context of the specification, such terms (including but not limited to top, bottom, above, below, under, on top of, upper, lower, on the left side of, on the right side of, front, back, next to, adjacent, between, horizontal, vertical, diagonal, longitudinal, transverse, radial, axial, etc.) are used for the convenience of referring to such components, devices, positions, features, or portions thereof in the drawings and are not intended to be limiting.

[0045] Furthermore, unless otherwise stated, any specific dimensions mentioned in this specification merely represent exemplary embodiments of devices embodying aspects of the present disclosure and are not intended to be limiting.

[0046] As used herein, the terms "substantially" and "substantial" refer to a considerable degree or extent. When used in conjunction with, for example, an event, circumstance, characteristic, or property, the terms may refer to instances in which the event, circumstance, characteristic, or property properly occurs as well as instances in which the event, circumstance, characteristic, or property occurs very nearly, for example taking into account representative tolerance levels or variability of the embodiments described herein.

[0047] As used herein, the terms “optional” and “optionally” mean that the subsequently described components, structures, elements, events, situations, characteristics, properties, etc. may or may not be included or may or may not occur, and that the description includes instances in which components, structures, elements, events, situations, characteristics, properties, etc. are included or occur and instances in which components, structures, elements, events, situations, characteristics, properties, etc. are not included or do not occur.

[0048] As used herein, the term "noise" broadly includes interference generated by any of a variety of random processes (e.g., flicker noise, shot noise), and also includes interference that is substantially unrelated to the signal being acquired and substantially unrelated to the acquisition method.

[0049] As used herein, the term "array" broadly includes structured or unstructured data that may be defined along any number of dimensions without restriction.

[0050] As will be appreciated by those skilled in the art, the present disclosure may be incorporated into any suitable sensor. Such exemplary sensors may include a touch screen, a fingerprint sensor, or other sensors configured to detect the position of an object or feature thereof. For purposes of illustration and not limitation, the following disclosure discusses embodiments of a two-dimensional sensor configured to detect the position of a user's finger or a portion thereof. In some embodiments, an exemplary sensor may include the general structure described in U.S. Pat. No. 8,421,890, which is incorporated herein by reference in its entirety.

[0051] In sensors such as touch screens and fingerprint sensors, noise may interfere with measurement accuracy. Therefore, it is desirable to minimize noise to the extent possible. For example, in U.S. Pat. No. 9,779,280 (which is incorporated herein by reference in its entirety), a system combining a reference electrode and a compensation electrode with a differential amplifier is used to improve the suppression of typical conducted and radiated noise sources found in sensors such as fingerprint sensors. Another strategy for minimizing noise is disclosed in U.S. Patent Application Publication No. 2019 / 0220141, which is incorporated herein by reference in its entirety. As disclosed in U.S. Patent Application Publication No. 2019 / 0220141, signals corresponding to pixel groups can be modulated and demodulated according to a mode to compensate for common-mode noise. The present application discloses techniques for improving data capture rate, signal-to-noise ratio (SNR) and / or signal-to-interference ratio (SIR). The techniques disclosed herein can be combined with the noise compensation strategies discussed in U.S. Pat. No. 9,779,280 and U.S. Patent Application Publication No. 2019 / 0220141.

[0052] Figure 1 An exemplary embodiment of a sensor region 100 is depicted. The sensor region 100 may include a plurality of receiving (i.e., RX) electrodes and a plurality of transmitting (i.e., TX) electrodes. The sensor region 100 may generally be bounded by a frame 50. The term "frame" should be broadly understood to include any area disposed around the sensor region, whether or not such area defines a separate structure. In some embodiments, the sensor region 100 may be configured to detect the presence of a finger or other object (e.g., a fingerprint ridge). For example, the sensor region 100 may have capacitive touch sensing functionality. In contrast, the frame may be less responsive to touch, and the frame may lack touch sensing functionality altogether. For example, the sensor region 100 may include transmitting electrodes and receiving electrodes, while the frame may lack such electrodes. In some embodiments, a receiving electrode set may include all receiving electrodes within the sensor region. The set may also optionally include one or more receiving electrodes disposed within the frame 50. Such receiving electrodes within the frame 50 may optionally be isolated so that they do not respond to the presence of a finger or other object. As discussed in more detail below, disposing one or more electrodes within the frame 50 may be useful in some embodiments, and such electrodes may be used in conjunction with other electrodes included in an electrode set to improve measurement accuracy.

[0053] Figure 2 An exemplary grid of receiving electrodes 102 (ie, RX electrodes) and transmitting electrodes 106 (ie, TX electrodes) disposed along opposing surfaces of insulating layer 104 is depicted. Such a grid may be disposed Figure 1 The sensor area 100 shown is arranged within or partially within Figure 1 100. In some embodiments, the insulating layer may include a dielectric substrate. The transmitting electrodes 106 may be arranged to intersect one or more of the receiving electrodes 102. In some embodiments, the transmitting electrodes 106 may be oriented perpendicularly relative to the receiving electrodes. Each transmitting electrode 106 may be operably connected to a power source 116 and configured to apply an electrical signal in an area around the corresponding transmitting electrode 106. For example, Figure 2 As shown, the transmitting electrode may be configured to apply an electric field including electric field lines 108. In some embodiments, power source 116 may be a battery, a capacitor, an inductor, a generator, or other element capable of applying electrical power.

[0054] In some embodiments, one or more electrodes (or each electrode) in the receive electrodes 102 may be configured to receive an electrical signal and transmit the received signal to a circuit near the corresponding receive electrode 102. In some embodiments, the receive electrodes 102 may be configured to receive the electromagnetic field applied by the transmit electrode 106, subject to any modification of the electric field due to, for example, the presence of an object placed within the range of the electric field. In this way, the receive electrodes 102 may be configured to receive an electrical signal containing an indication of whether an object or a part thereof is within the range of the electric field received by the corresponding receive electrode 102.

[0055] In some embodiments, the transmit electrodes 106 and the receive electrodes 102 may be arranged in a grid, whereby each intersection (also referred to herein as a pixel) of a corresponding transmit electrode and a receive electrode may function as a conversion circuit configured to output a signal containing an indication of whether an object is within the range of the electric field received by the corresponding receive electrode. As discussed in more detail below, information from each intersection may be collected and processed to determine the location of an object or a feature thereof on the two-dimensional sensor surface.

[0056] Note that other sensor embodiments may be equivalently used and combined with the disclosure herein, and the above description should not be construed as limiting in any way. For example, self-capacitance or absolute capacitance sensors and mutual capacitance or self-capacitance sensors may be equivalently used with the processing techniques and technical methods discussed herein.

[0057] Exemplary use scenarios of sensor area 100 are described herein. Objects to be sensed (e.g., fingers, styluses, etc.) may be placed in the vicinity of the electrodes. Overlap capacitances may vary depending on their proximity to the object to be sensed. Thus, each overlap capacitance may provide information about the topography of the nearby object being sensed. In this way, the position of a finger or stylus or fingerprint details may be determined by measuring the overlap capacitances. The overlap capacitances, and therefore the received signal, may be modulated due to the topography of nearby objects. For example, in the case where a fingerprint sensor measures the ridges and valleys of a user's fingerprint, a typical modulation depth may be in the range of 5%.

[0058] Overlap capacitance can be determined by driving one transmit electrode with a transmit signal. The signal can be coupled to each of the overlapping receive electrodes through overlap capacitance. Each receive electrode can receive a transmit signal proportional to the overlap capacitance of the receive electrode and the driven transmit electrode. By measuring the signal strength of each receive electrode, the overlap capacitance along the driven transmit electrode can be determined and used to determine a pixel value corresponding to the topography of an object near the electrode. This process can be repeated for each transmit electrode in any desired order, so that a complete set of 2D pixel values ​​corresponding to any one of the position, size, orientation, and topography of a nearby object can be determined.

[0059] The overlap capacitance can also be determined by driving multiple transmit electrodes simultaneously according to a predetermined pattern (rather than driving one transmit electrode at a time). For example, a suitable activation pattern may include a completely orthogonal or substantially orthogonal signal set (e.g., code division multiplexing / CDM). Examples of such signal sets include, but are not limited to, rows or columns of a Hadamard matrix, a cyclic Legendre sequence matrix, a cyclic Barker code sequence matrix, etc. By using such a substantially orthogonal signal set, the signal-to-noise ratio and signal-to-interference ratio of the system can be improved.

[0060] The CDM code set can be represented by a coding matrix, where each column of the matrix corresponds to an electrode state during a given time slot, and each row of the matrix corresponds to an electrode. (Alternatively, each column of the matrix can correspond to an electrode, and each row of the matrix can correspond to an electrode state during a given time slot.) There are many suitable CDM code sets, such as Hadamard matrices, truncated Hadamard matrices, cyclic Legendre matrices, or cyclic Barker code matrices, etc. Suitable modes and suitable CDM code sets are not limited to these sets; these sets are included as examples.

[0061] In some embodiments, the activation mode can be applied to the transmitting electrode. However, driving multiple transmitting electrodes simultaneously may exceed the available system power. In certain applications of capacitive fingerprint sensors (for example, when embedded in contactless smart cards), power is a particularly important consideration. Contactless smart cards do not have on-board batteries, but must obtain power for the fingerprint sensor from the wireless field. In some cases, the power obtained must be shared with other devices on the card, thereby reducing the amount of power available to drive the transmitting electrode on the sensor. In addition, in some cases, the sensor may only operate within a specific time window so that the card remains compatible with the ISO standard for contactless payment. In order to save power, while taking advantage of the signal-to-noise ratio improvement provided by CDM and other exemplary modes, it may be more desirable to apply the mode to the receiving electrode rather than the transmitting electrode. The disclosure of this article provides an effective technique for using multi-channel modes for receiving electrodes in an effective manner, which is ideal for power-constrained environments (such as capacitive fingerprint sensors embedded in smart cards).

[0062] As an example, the Nth order Legendre sequence 410 contains a single zero, (N-1) / 2 negative ones, and (N-1) / 2 positive ones (see Figure 4A ). For simplicity, the sequence order used in the drawings of this specification is intentionally kept low, however, as will be explained later, sequences with higher order may be preferred in practice. During the first time slot (e.g. corresponding to Figure 4A ), the (N-1) / 2 receiving electrodes corresponding to negative 1 in the sequence are connected together to the negative input terminal of the differential amplifier in the receiver circuit, and the (N-1) / 2 receiving electrodes corresponding to positive 1 in the sequence are connected together to the positive input terminal of the differential amplifier. (See Figure 3A and Figure 3B ). During a given time slot, the differential output of the amplifier may then be proportional to the dot product of the Legendre sequence corresponding to that time slot and the received signal value of the individual receiver electrodes. This value may then be saved as the first element of an N-element vector. During the next time slot (e.g., corresponding to Figure 4A The Legendre sequence can be cyclically shifted by 1, and the newly obtained dot product can be saved as the second element of the N-element vector. This process is repeated for a total of N time slots, resulting in a received vector containing N elements. The n-th order decoding matrix 420 (see Figure 4B ) can then be multiplied by the received vector to reconstruct the desired pixel value.

[0063] A set of CDM codes in which the sum of each sequence is zero (e.g., a set of truncated Hadamard sequences or a set of cyclically shifted Legendre sequences) can be said to be "balanced." By using a balanced set of codes, common-mode interference connected to the receiver electrodes can be eliminated by the differential amplifier. In addition, the common-mode portion of the received signal (e.g., a carrier) can also be eliminated. This can advantageously allow the entire dynamic range of the differential amplifier (and any subsequent circuitry) to be used for the modulated portion of the received signal.

[0064] Figures 3A-3C An exemplary system for receiving and processing signals using a multi-channel mode is shown. In some embodiments, multiple transmit electrodes 106 can be driven by a sequencer 202. Multiple receive electrodes 102 can receive the electrical signals generated by the transmit electrodes 106 and any modulated signals generated due to the presence of an object near the intersection between a corresponding pair of transmit electrodes and receive electrodes. The signal received by a given receive electrode 102 can be alternatively connected to ground, a positive input terminal of a differential receiver 206, and a negative input terminal of the differential receiver 206. In some embodiments, the analog front end can include a differential receiver 206 connected to the sensor electrodes. As shown in reference Figure 3B As described in more detail, selective coupling from a given receive electrode may be implemented by the switch unit 204. In some embodiments, the channel connected to a given receive electrode 102 is selected according to a modulation mode 410. For example, the mode may be, for example Figure 4A An encoding matrix 410 is shown.

[0065] The differential output from the receiver 206 may be converted to a digital value using, for example, an analog-to-digital converter 208. The digital output value in a given time slot may then be proportional to the signal from the receiver electrode during that time slot (e.g., modulated according to the parameters specified by the modulation pattern 410 for that time slot). This value may then be saved as the first element of an N-element vector. During the next time slot, the modulation pattern 410 may specify new parameters by which the received signal may be modulated, and the new output value may be saved as the second element of the N-element vector. This process is repeated for a total of N time slots, resulting in a receive vector containing N elements. For example, an n-th order decoding matrix 420 (see Figure 4B ) can then be multiplied (e.g., by calculating the dot product in step 212) by the received vector to reconstruct the desired pixel value. In step 214, the demodulated pixel values ​​can be stored in a memory. In step 216, a digital image can be constructed based on the demodulated pixel values. This step can optionally include one or more image processing steps, such as those described in reference to Fig. 9 , Figures 10A-10C , Fig.11 and Figures 12A-12BIn step 220, a matching algorithm may be used to compare the digital image to one or more enrolled templates 218 to determine a biometric parameter. For example, in the case of a fingerprint sensor, the matching algorithm may compare the digital image to the template image to determine whether the finger disposed on the fingerprint sensor is likely the same as the finger used to create one or more template images. In this case, the biometric parameter may be the identity of the user, for example.

[0066] Figure 3B An exemplary set of switch cells 204 connected to an exemplary differential receiver 208 is shown. Figure 3B As shown, a given receive electrode (e.g., RX_1) can be alternatively connected (e.g., by using a switch) to ground, a positive input terminal (SUM_P) of a differential receiver, or a negative input terminal (SUM_N) of a differential receiver. Each switch unit 204 can be connected to a multiplexing unit that can determine which available switches within a given switch unit 204 are connected in a given time slot. In some embodiments, each switch unit 204 can be arranged so that the receive signal from each receive electrode in the sensor area can be selectively connected to any one of the positive input terminal of the receiver 208, the negative input terminal of the receiver 208, or ground.

[0067] Due to the coupling between adjacent receive electrodes, it is desirable to place at least one ground electrode between each receive electrode connected to the receiver circuit during a time slot. This keeps the electric field coupling the transmit electrode to the receive electrode more localized, resulting in less blurring of the reconstructed image. To provide ground electrodes, multiple groups of receive electrodes can be staggered. Then, when one such set of electrodes is connected to the receiver circuit, the adjacent staggered set of receive electrodes can be grounded. Any unused electrodes are also grounded. Figure 3B A switch tree in (which can be controlled by the RX encoder) enables the receive electrodes to be connected in this way.

[0068] Figure 3C Depicted with Figure 3BAn embodiment similar to the embodiment of the present invention is different in that a plurality of differential receivers (or analog front ends) are provided. One or more groups of electrodes can be connected to a first differential receiver 208a via a corresponding switch unit 204a. Electrodes belonging to other groups can be connected to a second differential receiver 208b via a corresponding switch unit 204b. The electrodes connected to a given receiver 208a (or 208b) can belong to a single group, or they can belong to multiple groups. Providing a plurality of differential receivers allows data to be collected from a plurality of electrode groups simultaneously. For example, during a first time interval, a first differential receiver 208a can receive a signal from an electrode connected to the first differential receiver 208a, and a second differential receiver 208b receives a signal from an electrode connected to the second differential receiver 208b. Although two receivers are shown in the exemplary drawings, any number of differential receivers can be used to further increase the rate at which the system collects data.

[0069] To reduce electrical coupling between active electrodes, electrodes connected to one differential receiver can be interleaved with electrodes connected to other differential receivers so that the electrodes active in a given time slot will always have at least one ground electrode between them. For example, the electrodes to be activated during a given time slot can define a superset (typically consisting of multiple groups in a multi-differential receiver embodiment), and the superset can be interleaved with electrodes that are not in the superset so that for any pair of two electrodes selected from the superset, at least one electrode that is not in the superset is disposed between the selected pair. In a dual receiver embodiment, one way to achieve this is to assign two groups of electrodes to each receiver: a first group and a second group to the first receiver, and a third group and a fourth group to the second receiver. The first group and the third group can define a first superset that will be active at the same time, and the second group and the fourth group can define a second superset that will be active at the same time. In this case, regularly interleaving the electrodes of each group (first, second, third, fourth, first, and so on) will ensure that no two electrodes in the same superset are adjacent to each other.

[0070] Figures 5A-5C An example of RX electrode interleaving is shown. Figure 5A In the example shown, the sensor area includes a set of twenty-eight receive electrodes organized into four electrode groups 502, 504, 506, 508, each electrode group having seven electrodes. Figure 5A As indicated, electrode group 502 includes receiving electrodes 0, 4, 8, 12, 16, 20, and 24. Each corresponding electrode group can be sampled in sequence. For example, measurements from electrode group 502 are received in time slots 1-7, measurements from electrode group 504 are received in time slots 8-14, and so on. Figure 5AAs shown, the electrodes in the corresponding electrode groups are interleaved. That is, a first electrode and a second electrode (e.g., electrodes 8 and 12) are taken from group 502, where no other electrode in the same group 502 is between the selected first electrode and the second electrode, and three electrodes from other groups (here, one electrode from group 504, one electrode from group 506, and one electrode from group 508) are observed to be disposed between the first electrode and the second electrode. In this example, the interleaving factor Z (defined as one plus the number of electrodes between adjacent electrodes of a given group) is equal to four.

[0071] exist Figure 5A In an embodiment, the electrode groups are of the same size and the electrodes are regularly spaced apart in a repeating pattern of four electrodes, with one electrode being taken from each electrode group in turn. That is, electrode number 0 is in group 502, electrode number 1 is in group 504, electrode number 2 is in group 506, electrode number 3 is in group 508, electrode number 4 is in group 502, and so on. In such an arrangement, any two adjacent electrodes in a single group are selected and at least one electrode in each other group will be disposed between the two selected electrodes. Regular interleaving in this manner is advantageous because it maximizes the distance between electrodes that will be active in a given time slot, thereby minimizing coupling noise. In addition, in Figure 5A In an embodiment, the number of electrodes Y in the sensor area is equal to the interleaving factor Z multiplied by the number of electrodes in each group N. This is advantageous because (i) each electrode group extends across the entire sensor area (e.g., Figure 5A Each column in substantially spans the sensor), and (ii) ensures that by iterating through the electrode groups, all data can be accurately collected from each receiving electrode in the sensor at one time. This reduces noise and improves scan time. Although these conditions (regular interleaving and Y=NZ) are advantageous, it is possible to deviate from these conditions while still achieving the expected benefits to some extent. For example, the interleaving can be irregular so that electrodes in the same group are spaced different distances on the sensor. In such a case, Z can be determined by referring to the largest such spacing between electrodes in the group. Similarly, electrode groups of different sizes can be used. In such a case, N can be determined by referring to the largest electrode group. Regarding the relationship between Y, N and Z, particularly advantageous arrangements include those where Y≤3NZ, Y≤2NZ, Y≤1.5NZ, Y≤1.1NZ and Y≤NZ.

[0072] although Figure 5AThe interleaved embodiment shown reflects a single differential receiver embodiment, but the concept can be extended to multiple differential receiver embodiments. For example, group 502 and group 504 can be connected to one differential receiver, while group 506 and group 508 can be connected to another differential receiver. Data can then be collected from group 502 and group 506 at the same time (e.g., in time slots 1-7), and data can be collected from group 504 and group 508 at the same time (e.g., in time slots 8-14). By interleaving in this manner, no two adjacent electrodes will be active in the same time slot.

[0073] exist Figure 5B In the example shown, the interleaving factor Z is 2. Here, each receive electrode is separated by a grounded "interleaved" electrode. The size of the electrode group is 7. In the first time slot, 14 of the 26 available receive electrodes are in use, leaving 12 electrodes unused and therefore grounded. Note that in this example, data is captured twice from electrodes 12 and 13. Although as with Figure 5A This reduces the scan speed slightly compared to the embodiment of , but it is still a relatively efficient embodiment and if additional data capture is required for some receive electrodes, it is relatively Figure 5A This may have advantages in embodiments of the present invention.

[0074] exist Figure 5C In the example shown, the interleaving factor is 3. Here, each receive electrode is separated by two grounded "interleaved" electrodes. In addition, the size of the electrode group is 7. In the first time slot, 21 of the 26 available receive electrodes are in use, leaving 5 electrodes unused and therefore grounded.

[0075] Figure 6 An exemplary method 600 for obtaining data from a set of receive electrodes in a sensor is shown. In step 602, a group of receive electrodes may be selected. As described above, this may be the group of receive electrodes to which a modulation pattern will be applied. In step 604, electrodes not selected in step 602 may be grounded. The unselected electrodes may belong to a group of electrodes that will be selected for data collection in a subsequent cycle. In step 606, parameters specified by the modulation pattern may be applied to the group selected for the first time slot. For example, a modulation pattern may be applied. Figure 4AThe first column value in the matrix of is assigned so that the electrode with the matrix assigned value of "0" can be grounded, the electrode with the assigned value of "1" can be connected to the positive input terminal of the receiver, and the electrode with the assigned value of "-1" can be connected to the negative input terminal of the receiver. In step 608, the data about the time slot can be stored. In step 610, the system can determine whether the parameters specified for each time slot in the modulation pattern have been applied. If not, the system can return to step 606 and apply the parameters for the next time slot in the pattern. In step 612, the system can determine whether data has been obtained from all desired receiving electrodes. If data has not been collected from all desired electrodes, the system can return to step 602 and continue to collect data from the next group of electrodes. If data has been collected from all desired electrodes, the system can proceed to step 614 and end the data collection process.

[0076] As described above, there is an optimal combination of encoding order N, number of electrodes Y, and interleaving Z to keep the time spent scanning all RX electrodes to a minimum using the above process. Ideally, Y is equal to an integer multiple of N times Z (e.g., Figure 5A ). If this is the case, the system can proceed through method 600 to collect data from the same size electrode group exactly once without repeating. However, if this is not the case (e.g., as in Figure 3B and Figure 3C ), for example due to design limitations on the sensor that fixes the number of electrodes to another value, the previously scanned electrodes can be overlapped again to include the remaining electrodes, or electrode groups with different sizes can be used to collect data from the remaining electrodes. For modulation matrices that are short compared to the number of electrodes, overlapping does not result in significant scan time overhead. However, for matrices that are long compared to the number of electrodes, the increased scan time overhead may be significant.

[0077] As mentioned above, there are many different selections for the suitable mode that can be used for modulating receiving electrodes.A kind of particularly advantageous mode category is Legendre sequence.These sequences provide many benefits.Legendre sequence is balanced, and this allows the dynamic range of larger part (fraction) to be used to obtain useful data, thereby improves measurement sensitivity.In Legendre sequence, each parameter set of given time slot is the cyclic shift of the parameter about the first time slot, allows to define the large NxN matrix that comprises N order Legendre sequence only using N memory storage locations.Legendre sequence is applicable to any odd prime number (i.e. any prime number except 1 or 2) order.In addition, except polarity (for some order), decoding matrix is ​​identical with coding matrix, therefore does not need additional memory storage location for decoding matrix.In addition, coding matrix and decoding matrix all only comprise the value from set {-1,0,+1}, therefore encoding and decoding all do not need multiplication or division.

[0078] Hadamard sequences have also been found to be particularly advantageous. The Hadamard sequence can be truncated to remove the last column of all 1s, resulting in a set of balanced columns. The decoding matrix of the truncated Hadamard encoding matrix is ​​the transpose of the encoding matrix, which means that the decoding matrix can be derived efficiently. In addition, for N pixels, only (N-1) time slots are required, which means that scanning efficiency is improved. Both the encoding matrix and the decoding matrix only contain values ​​from the set {-1, +1}, so no multiplication and division are required for both encoding and decoding.

[0079] As mentioned above, the received vector can be multiplied by the n-th order decoding matrix (see Figure 3A Decoding is achieved by reconstructing the desired pixel value using steps 420 and 212 in . In the case where a balanced code is used for encoding, the common mode portion of the received signal is removed, so the average value of the demodulated pixel values ​​of a given group will be zero. If a high-order balanced sequence (N is large) is used, the average value of the original pixel value will be approximately constant between electrode groups due to the law of large numbers. Therefore, the approximate average value can be appropriately restored by adding a global recovery value to each reconstructed pixel of each reconstruction group of N pixels. In some embodiments, the value may be equal to or approximately equal to the midpoint of the available grayscale range. In other cases, it may be desirable to use a slightly larger value. For example, for a sensor capable of producing an 8-bit image, the minimum possible grayscale value is 0 (corresponding to black), and the maximum possible grayscale value is 255 (corresponding to white). For such a grayscale range, the midpoint and therefore the appropriate corresponding global recovery value is 128.

[0080] Of course, it is also possible to use an unbalanced sequence. In such a case, the modulation mode can remove a portion of the common mode portion of the received signal, but not all. The term "removal" should therefore be broadly understood to include complete and partial removal of the common mode signal portion. In the case of removing all common mode portions, it is particularly advantageous to use a global recovery value because this ensures that the average value between the electrode groups will be the same. In other cases where some (but not all) of the common mode portions are removed, it may still be acceptable to use a global recovery value. In other cases, a global recovery value is not used.

[0081] Figure 7 An exemplary embodiment is shown in which a corresponding recovery value can be determined for each electrode group. In this embodiment, the receiving electrodes of the sensor area can be assigned to groups as described above. Figure 7, three groups 706a, 706b, and 706c are shown. For simplicity, these groups are shown in small (N=4) groups without interleaving, but in practice, as described throughout this disclosure, these groups will preferably be larger and interleaved. Each of the exemplary receiving electrode groups 706a, 706b, and 706c of the sensor area can share a common electrode 702. Each electrode group can also include their own receiving electrodes that are not shared by other groups. For example, group 706a can include one or more electrodes 704a, group 706b can include one or more electrodes 704b, and group 706c can include one or more electrodes 704c. As described above, the receiving electrodes can also intersect with multiple transmitting electrodes to form multiple pixels 710. The pixels formed by the common electrode 702 can be considered to be common pixels 708. For simplicity, Figure 7 A single row of pixels arranged along a single transmitting electrode 712 is shown, but these rows can extend along each transmitting electrode in the sensor area. In some embodiments, the common electrode 702 can be placed in a position that is substantially unresponsive to capacitive modulation generated by the presence of an object (e.g., a finger or fingerprint feature). For example, the common electrode can be arranged within the frame and substantially isolated from the sensor surface. Isolation can help ensure that the true signal value obtained for the common electrode is the same between electrode groups.

[0082] In the case where the balanced mode is used to modulate the signal received from each electrode group, the average value of the demodulated value obtained from each group will be zero. However, the true average value may be slightly different between groups (especially when using low-order modes). Providing a common electrode allows these differences to be determined. Specifically, because the true signal value received for the common electrode 702 can be assumed to be equal between groups (within a given scanning cycle), the difference in the demodulated value can be assumed to be an artifact introduced by the modulation process and the demodulation process. These differences can be calculated, and the corresponding recovery value can be determined for each group. The corresponding recovery value of a given group can be a value as follows: when the value is added to the demodulated value obtained for the group, the adjustment value obtained about the common electrode as determined for the group is equal to the adjustment value obtained about the common electrode as determined for each group in the other groups of the sensor. This technology and other technologies for recovering common-mode signals between electrode groups are described in U.S. patent applications with publication number 2019 / 0220141. The technology described therein can also be combined with the embodiments presented in the present disclosure.

[0083] For example, refer to Fig.15 , 16A-16B and 17, in some embodiments, by terminating one or more of the transmit electrodes so that they are not close to and do not apply an electrical signal to one or more reference electrodes, the one or more reference electrodes can be isolated from the carrier signal applied by the transmit electrodes. In some embodiments, the reference electrode can be coupled to a user's finger (or other object detected by the sensor). In such an embodiment, the reference electrode may not receive a signal from the drive line and therefore will have a known value of substantially zero, but will still receive interference from the coupled finger, allowing the interference to be eliminated as described above.

[0084] By isolating one or more pixels from the stimulus applied by the drive line, a "known" reference pixel can be established. For example, an isolated pixel can be assumed to have a true value of zero. By using these known true values ​​in conjunction with the demodulated values ​​obtained for non-isolated pixels as described above, the true value of the non-isolated pixel can be determined. For example, a restored value can be selected for a group of adjacent pixels so that the calculated value of the known reference pixel is equal to the expected value of the known reference pixel (e.g., zero or a carrier-based value). For example, one or more common pixels can be selected as known reference pixels. In another example, the sensor can be divided into regions, each of which has a known reference pixel relative to which adjacent pixel values ​​can be determined.

[0085] In any of the above methods, one or more lines of the sensor may be set outside the area of ​​the sensor that the user may touch. This may have the effect of shielding the pixels on these lines from the influence of measurement signals and / or noise. In this way, pixels with known values ​​can be established. In some embodiments, these known values ​​can be zero or substantially zero. In some embodiments, these known values ​​can be substantially equal to the signal (e.g., carrier signal) applied by one or more drive lines. In some embodiments, lines can be set at one or more edges of the sensor so that the lines are outside the area of ​​the sensor that the user can touch. In other embodiments, pick-up lines can be set at one or more edges of the sensor so that the pick-up lines are outside the area where the drive lines apply signals, so that these pick-up lines receive finger coupled noise but no measurement signal. As described above, the pixels on these lines can be used as known reference pixels and / or common pixels.

[0086] Fig.15 and Figures 16A-16BAn exemplary arrangement is shown in which reference electrodes 1512a, 1512b are located within or adjacent to the sensor grid. By arranging the reference electrodes 1512a, 1512b within the sensor grid, the reference electrodes 1512a, 1512b may be exposed to finger coupled noise, which may cause the finger coupled noise to be common to the reference electrode and any other electrode in the sampling group. This can help to remove common mode noise via signal processing (e.g., by applying a balanced encoding pattern). In some embodiments, the reference electrodes 1512a, 1512b may be arranged at or near the edge of the sensor grid. In other embodiments, one or more reference electrodes may be arranged inside the sensor grid. In such a case, one or more reference electrodes may be isolated from the transmitting electrode (so that they do not generate a measurement signal) via a shielding layer or by separating one or more transmitting electrodes so that they approach from either side but do not intersect with the reference electrode. In some embodiments, the geometry of the reference electrodes 1512a, 1512b may be the same (or substantially the same) as the geometry of the receiving electrodes in the sensor grid. In this way, the reference electrode may receive a similar level of noise as the receive electrode.

[0087] In some embodiments, the transmitting electrodes 1506a, 1506b can be arranged in the sensor grid so that the transmitting electrode 1506a can extend from the power connector 1522a on the west side of the grid, and the transmitting electrode 1506b can extend from the power connector 1522b on the east side of the grid. (Note that directional terms such as east, west, north, and south are used in a relative sense and are only for the purpose of simplifying the description and not for the purpose of limitation. In practice, the orientation of these directional terms can be determined arbitrarily and do not require a specific orientation or angular relationship). The power connectors 1522a, 1522b can be connected to one or more power supplies that can selectively apply one or more carrier signals to the transmitting electrodes 1506a, 1506b. The transmitting electrodes 1506a originating from the west side can be staggered with the transmitting electrodes 1506b originating from the east side. In some embodiments, staggering the electrodes in this way can reduce coupling between the transmitting electrodes that are active in a given time slot.

[0088] The sensor grid may include a ground electrode 1520a, which may be placed on either or both sides of the reference electrode 1512a. The sensor grid may also include a ground electrode 1520b, which may be placed on either or both sides of the reference electrode 1512b. In some embodiments, the reference electrode 1512a may be arranged so that the reference electrode 1512a does not intersect with the transmitting electrode 1506b. The ground electrode 1520a may also be arranged so that the ground electrode 1520a does not intersect with the transmitting electrode 1506b. In some embodiments, the reference electrode 1512b may be arranged so that the reference electrode 1512b does not intersect with the transmitting electrode 1506a. The ground electrode 1520b may also be arranged so that the ground electrode 1520b does not intersect with the transmitting electrode 1506a. The receiving electrode 1502( Fig.15 Not shown; see Figures 16A-16B ) can be set between the reference electrodes.

[0089] In use, one or more of the transmitting electrodes 1506a may apply a carrier signal in a first time slot. During this first time slot, the transmitting electrode 1506b may be inactive. Because the reference electrode 1512b is isolated from the transmitting electrode 1506a, there will be no mutual capacitance signal on the reference electrode 1512b during the first time slot. Therefore, although a finger (or other body part) may be close to the reference electrode 1512b, so that body-coupled noise may be picked up by the reference electrode 1512b, it is known that the mutual capacitance value on the reference electrode 1512b is zero during the first time slot.

[0090] During the second time slot, one or more of the transmit electrodes 1506b may apply a carrier signal. During this second time slot, the transmit electrode 1506a may be inactive. Because the reference electrode 1512a is isolated from the transmit electrode 1506b, there is no mutual capacitance signal on the reference electrode 1512a during the second time slot. Therefore, although a finger (or other body part) may be close to the reference electrode 1512a, so that body-coupled noise may be picked up by the reference electrode 1512a, it is known that the mutual capacitance value on the reference electrode 1512a is zero during the second time slot. As shown below with reference to Fig.18 As discussed, the process may be repeated by sampling additional electrodes in additional time slots until, for example, all pixels in the sensor grid have been sampled.

[0091] Fig.16A and Fig. 16B It is a reflection Fig.15 Exemplary cross-sectional view of the arrangement shown. Fig.16A shows a cross section in which the transmitting electrode 1506b from the east side is provided, and Fig. 16BFIG. 1 shows a cross section in which the transmitting electrode 1506a is arranged from the west side. Figures 16A-16B As reflected, the reference electrode 1512a can be isolated from the transmitting electrode 1506b originating from the east (e.g., by one or more ground electrodes 1520a), and the reference electrode 1512b can be isolated from the transmitting electrode 1506a originating from the west (e.g., by one or more ground electrodes 1520b). At the same time, the receiving electrode 1502 is exposed to the electrode 1506a originating from the west and the electrode 1506b originating from the east. Fig.16A and Fig. 16B The unmarked solid elements depicted in the figure may be polymer layers. One or more of these elements may optionally be made of metal in whole or in part to provide additional shielding as needed. In some embodiments, the metal shielding layer may be grounded.

[0092] Fig.16A and Fig. 16B Also shown are optional carrier injection nodes 1518a, 1518b. Fig.16A and Fig. 16B Two carrier injection nodes are shown in FIG, but any desired number of carrier injection nodes may be used. For example, each group of electrodes to be processed in a modulation group may have its own reference electrode with an injection node. In other embodiments, a single carrier injection node may be used for all reference electrodes in the system.

[0093] In some embodiments, it may be desirable to receive a signal from a reference electrode that includes (i) body-coupled noise and (ii) a carrier signal transmitted from a drive electrode without modulation due to the presence of a finger (or other body part). For example, where a reference electrode is included in an electrode group to which a balanced coding pattern is applied, it may be advantageous for the reference electrode to be exposed to body-coupled noise so that the noise will be common to all electrodes in the coding group. Similarly, it may be advantageous for the reference electrode to be exposed to a carrier signal so that the transmitted carrier signal will be (substantially) common to all electrodes in the coding group. In this way, common-mode noise and common-mode portions of the carrier may be removed by applying a balanced coding pattern. However, if a carrier is applied to a reference electrode near a finger, however, the presence of the finger may modulate the mutual capacitance between the transmitting electrode and the reference electrode, which means that the reference electrode may generate a non-zero measurement signal and can no longer be used as a reference electrode.

[0094] The carrier injection nodes 1518a, 1518b allow the carrier signal to be applied to the reference carrier electrodes 1514a, 1514b at a position isolated from the finger, and therefore no measurement signal will be generated. One or more carrier injection nodes may be located at a position isolated from the sensing area of ​​the sensor. In some embodiments, the carrier injection node may be located behind the shielding layer so that the presence of a finger or other object will not modulate the capacitance across the carrier injection node. The carrier injection node may also be located, for example, on the reverse side of the sensor grid, where the material of the sensor (or the object into which the sensor is incorporated) may provide shielding and / or may prevent the finger (or other object) from becoming close enough to the carrier injection node to affect the mutual capacitance. In some embodiments, the carrier injection node may be located near the reference electrode so as to short the carrier injection node to the associated reference electrode. In some embodiments, the carrier injection node may be located outside the sensor grid area. In some embodiments, the carrier injection node may be arranged within or integrated into the circuit element of the sensor system. For example, one or more carrier injection nodes may be arranged within an analog front end, which is configured to receive signals from one or more electrode groups in the sensor area.

[0095] In some embodiments, the carrier injection node 1518a may include a carrier injection transmitting electrode 1516a and a reference carrier electrode 1514a. In some embodiments, the carrier injection transmitting electrode 1516a may be activated with one, more, or all transmitting electrodes 1506b originating from the east side. As described above, although Fig.16A and Fig. 16B Two carrier injection nodes are shown in this exemplary embodiment of , but any desired number of carrier injection nodes may be used. For example, each group of electrodes to be processed in the modulation group can have its own reference electrode with an injection node. In other embodiments, a single carrier injection node can be used for all reference electrodes in the system. In some embodiments, carrier injection node 1518a can be the only carrier injection node set in the system. In some embodiments, carrier injection node 1518a can be activated with one, some or all transmitting electrodes in the sensing system during their corresponding activation cycles.

[0096] The carrier injection node 1518b may include a carrier injection transmitting electrode 1516b and a reference carrier electrode 1514b. In some embodiments, the carrier injection transmitting electrode 1516b may be activated with one, more, or all transmitting electrodes 1506a originating from the west. The composition and geometry of the carrier injection nodes 1518a, 1518b may mimic the composition and geometry of the intersection between the transmitting electrodes 1506a, 1506b and the receiving electrode 1502, so that a mutual capacitance similar to that occurring between the transmitting electrodes 1506a, 1506b and the receiving electrode 1502 occurs between the carrier injection transmitting electrodes 1516a, 1516b and the reference carrier electrodes 1514a, 1514b. Optionally, a ground electrode or shield may be provided on either or both sides of the carrier injection transmitting electrodes 1516a, 1516b and / or the reference carrier electrodes 1514a, 1514b. Shielding layers may also be placed above or below the carrier injection nodes 1518a, 1518b to prevent the user's fingers (or other body parts) from modulating the mutual capacitance between the carrier injection transmission electrodes 1516a, 1516b and the reference carrier electrodes 1514a, 1514b. In some embodiments, the orientation of the carrier transmission electrode 1516a and the reference carrier electrode 1514a may be reversed so that the reference carrier electrode 1514a is located below the carrier transmission electrode 1516a (in FIGS. 16a and 16b). Fig. 16B Place the reference carrier electrode toward the center of the sensor structure (e.g. Fig.16A and Fig. 16B However, the reverse orientation may allow the reference carrier electrode to be manufactured in the same step as the receive electrode 1502, which may promote uniformity in the structure and geometry of the reference carrier electrode and the receive electrode.

[0097] When activated, the signal from the reference carrier electrodes 1514a, 1514b can thus mimic the portion of the carrier signal transmitted from the transmitting electrodes 1506a, 1506b to the receiving electrode 1502 when there is no finger. During the first time slot, when the transmitting electrode 1506a originating from the west and the carrier injection transmitting electrode 1516b are active, the reference electrode 1512b can capture the body coupled noise, and the reference carrier electrode 1514b can capture the transmitted carrier signal. These signals can be combined (e.g., by summing the signals or by shorting the electrodes 1512b, 1514b together) and processed in the first electrode group in the first time slot. During the second time slot, when the transmitting electrode 1506b originating from the east and the carrier injection transmitting electrode 1516a are active, the reference electrode 1512a can capture the body coupled noise, and the reference carrier electrode 1514a can capture the transmitted carrier signal. These signals can be combined (e.g., by summing the signals or by shorting electrodes 1512a, 1514a together) and processed in a second time slot in a second electrode group. Although two time slots are discussed here by way of explanation, the process can be repeated so that additional electrodes can be sampled in additional time slots until, for example, all pixels in the sensor grid are sampled.

[0098] In some embodiments, physical carrier injection nodes 1518a, 1518b can be replaced with virtual carrier injection, wherein the carrier signal of the transmission received by the assumed reference carrier electrodes 1514a, 1514b is determined by calculation. For example, the transfer parameter can be determined empirically via testing during manufacture and multiplied by the known value of the carrier signal. In other embodiments, the transmission parameter can be adjusted based on, for example, temperature, humidity, age or other variables related to the sensor. In some embodiments, the transmission carrier signal determined by calculation can be electronically synthesized and injected into one or more reference electrodes. In other embodiments, before the decoding mode is applied to the value obtained from the corresponding electrode group, the value representing the virtual transmission carrier signal can be added to the signal value received from the reference electrode.

[0099] In some embodiments, a balanced coding pattern can be applied to one or both of these first and second electrode groups. In this way, common-mode finger-coupled noise and common-mode carrier signals can be removed. Removing finger-coupled noise and carrier signals can improve the signal-to-noise ratio and signal-to-interference ratio, and can allow the dynamic range of the system to be dedicated to the measurement signal.

[0100] After applying the balanced coding mode, the corresponding decoding mode can be used to decode the result value. As described above, applying the balanced coding mode removes the common mode portion (i.e., the average value) from the measured value. In the case where the coding group includes a reference electrode with a known (e.g., zero) measured value, the exact value of the measured value of the electrode group can be restored by adding a recovery value to each measured value, and the recovery value is selected so that the result measurement value of the reference electrode will be equal to its expected measurement value (e.g., zero). For example, given an input vector [a, b, c, d, e], the vector encoded and then decoded will be equal to [am, bm, cm, dm, em], where m = the average value of the elements of the input vector. If element e is a reference, its measured value may be known to be zero. Therefore, the reference value encoded and then decoded is (em) = (0–m) = (-m). If (-m) is then subtracted from each element of the modulated and then demodulated vector, [a, b, c, d, 0] is obtained. This results in the correct values ​​of elements a, b, c, and d.

[0101] Fig.17 Another exemplary arrangement of reference electrodes is shown. This arrangement is in principle exactly like Fig.15 and Figures 16A-16B The embodiment shown in Figure 17 is operated in the same manner. By placing reference electrodes 1712a, 1712b outside the sensor grid 1700, the capacitance between the transmitting electrode and the reference electrode is avoided. The reference electrodes 1712a, 1712b can be arranged so that when the sensor grid 1700 is used, they are exposed to body coupling noise. For example, multiple reference electrodes can be arranged so that the user's finger will pass through at least one reference electrode in all expected use orientations. Depending on the usage scenario of a given sensor, this can be done using one, two, three, four or more reference electrodes. In an embodiment in which more than one reference electrode is arranged, the sensor system can select and use the best positioned reference electrode to pick up body coupling noise. For example, the system can measure the body coupling noise received by each available reference electrode and select the available electrode with the largest measurement noise received from the user's finger or other element. The selected reference node can then be used in one, some or all electrode groups during the sampling process.

[0102] In some embodiments where the sensor is disposed on a known substrate (e.g., a credit card), it may be expected that a user's finger will always approach the sensor grid from a particular side 1750 of the substrate. In such a case, a single reference electrode 1712b may be placed between the sensor grid 1700 and the side 1750 of the substrate. In this manner, under use conditions, a finger will be more likely to pass by the single reference electrode 1712b, causing the reference electrode 1712b to pick up the desired body-coupled noise. In some embodiments, the reference electrode 1712b (and / or other reference electrodes) may be arranged parallel to or transverse to the receive electrodes in the sensor grid 1700. The physical and virtual carrier injection methods and signal processing methods discussed above may be applied to Fig.17 Embodiment of the invention.

[0103] Fig.18 An exemplary method 1800 for using the reference electrode system described above is shown. In some embodiments, the method can be used with any of the structures described above (particularly with respect to Figure 15-17 ) together. For example, the system can be performed in a system including a plurality of electrode groups, wherein each electrode group in the plurality of electrode groups includes a corresponding reference electrode whose true signal value is a predetermined value. In some embodiments, the predetermined true signal value can be zero (for example, when the reference electrode is isolated so that no measurement signal is expected). As described above, the measured value can be obtained by sampling the pixels in the group (for example, the intersection of the transmitting electrode and the driving electrode). In step 1802, the first group in the electrode group can be sampled by modulating the signal received from each electrode in the corresponding electrode group according to the modulation mode. The modulation mode can be balanced so that the average value of the signal received in any given time slot is zero. In step 1804, the received signal or the value derived from the signal can be demodulated. The output can be a set of demodulated values ​​of the corresponding electrode group. These demodulated values ​​can accurately reflect the relative value of each sampled pixel, but in the case of using a balanced modulation mode, the average value may have been removed.

[0104] In step 1806, the average value can be restored using the predetermined value of the reference electrode in the corresponding electrode group. For example, the set of demodulated values ​​of the electrode group may include the demodulated value (K-M) of the reference electrode, where K represents the true signal value of the reference electrode included in the group, and M represents the average value of the true signal value of each electrode included in the group. In this case, the true value of the sampled pixel can be restored by adding the offset value to each demodulated value in the set of demodulated values. In some embodiments, the offset value can be selected so that the sum of the offset value and the demodulated value of the reference electrode is equal to K. In the case where the predetermined value of the reference electrode is zero, for example, the true value of the sampled pixel in the corresponding group can be restored by simply subtracting the demodulated value obtained for the reference electrode.

[0105] At step 1808, the system can determine whether data has been obtained from all desired electrode groups in the sensor grid. If data has been obtained for all desired electrode groups, method 1800 can be completed. If additional electrode groups need to be sampled, the process can return to step 1802 to sample another electrode group.

[0106] Optionally, different transmit electrode groups may be used to sample different electrode groups, as described above. For example, a first set of transmit electrodes may be used for a first iteration of steps 1802, 1804, 1806, and a second set of transmit electrodes may be used for a second iteration of steps 1802, 1804, 1806. For additional iterations, additional transmit electrode groups may be used, or the system may alternate between the first set of transmit electrodes and the second set of transmit electrodes. In some embodiments (which may include but are not limited to Fig.15 In some embodiments, the system may be configured to receive a signal from the first electrode group at a first time, during which the second set of transmitting electrodes applies a carrier signal, while the first set of transmitting electrodes does not apply a carrier signal. The system may also be configured to receive a signal from the second electrode group at a second time, during which the first set of transmitting electrodes applies a carrier signal, while the second set of transmitting electrodes does not apply a carrier signal.

[0107] Theory shows that increasing the order of the modulation matrix improves the possible signal-to-noise ratio. When higher-order sets of receive electrodes are also interleaved, the variation in the mean values ​​of these sets (before and during encoding) is further reduced because the correlation between the sets is high (i.e., the pixel values ​​in each set are similar). In addition, interleaving forces each set to more fully span the width (or height) of the sensor, which reduces the variation in the mean value due to local variations in image content.

[0108] However, the error introduced by applying a global recovery value will span each row in a pattern that is cyclic and has a period equal to the interleaving factor. If the interleaving is too large, (a) the period of the pattern may be similar to the ridge spacing of a fingerprint, and (b) using a larger interleaving forces the matrix order to be lower (assuming a constant number of receive electrodes). Then, the true average signal value will vary more from electrode group to electrode group, increasing the magnitude of the recovery error.

[0109] An example of this is Figures 8A-8B Shown in. Fig. 8AThe first (left) image in is a simulated test image and contains a fingerprint and a blank portion. This test image simulates a "partial touch" where the finger covers only a portion of the sensor, i.e., there are contact areas and non-contact areas. Fig. 8A The second (middle) image in shows the result of encoding a test image with a low order pattern (e.g., Legendre order 7) with a large interleave (28) for the 196 receive electrodes, then decoding the result and applying a global recovery value of 128. Periodic patterns after DC recovery are visible in the non-contact portion of the image, and it is apparent that these patterns can be interpreted by the matching engine as fingerprint ridges, resulting in false acceptance or false rejection of the sensed fingerprint compared to the recorded template. Fig. 8A The third (right) image in Figure 1 shows the result of encoding the 172 RX electrodes with a high order pattern (Legendre order 43) together with a low interleave (4), then decoding the image and applying a DC restored common value of 128. The high order encoding in the third image improves the theoretical SNR compared to the second image. In addition, the periodic pattern after DC restoration, while still present, is shorter in period and lower in amplitude, thus reducing the possibility of false acceptance and false rejection rates when sending this image to the matcher.

[0110] Figure 8B The two images in the figure show Fig. 8A Although the restoration error exists in the second and third images of Fig. 8A The human eye may not notice it, but Figure 8B The error is shown in Fig. 8A The error may exist in the contact area as well as the non-contact area. However, since the high-order Legendre coding improves the SNR, the desired fingerprint signal in the contact area is much stronger than the error.

[0111] It has been determined that for capacitive fingerprint sensors, a Legendre order above 23 used in combination with an interleaving factor between 2 and 6 gives the best results, particularly in the cases Y≤3NZ, Y≤2NZ, Y≤1.5NZ, Y≤1.1NZ or Y≤NZ.

[0112] In a system with regularly interleaved, equally sized electrode groups (and in which data for each pixel will be collected exactly once), Y=NZ is a particularly favorable condition. In such a case, a larger mode order will increase the maximum SIR. At the same time, due to functional considerations, the number of receiving electrodes to be set in the sensor area can be limited to a certain range. At the same time, a larger interleaving factor tends to reduce the coupling between electrodes active in a given time slot. Taking these factors into account, suitable conditions for a given sensor can be determined. For example, a 53rd order Legendre sequence can be combined with an interleaving factor of 2 to produce a sensor with 106 receiving electrodes. In another example, a 43rd order Legendre sequence can be combined with an interleaving factor of 3 to produce a sensor with 129 receiving electrodes. Other suitable combinations can be determined in this way, as shown in the following table.

[0113]

[0114] In systems where data for pixels on a common electrode is collected more than once (e.g., data can be collected from a common electrode each time an electrode group is scanned), Y=(N-1)Z+1 is a particularly advantageous condition. For example, a 53rd order Legendre sequence can be combined with an interleaving factor of 2 to produce a sensor having 105 receiving electrodes. Compared to the 106-electrode embodiment described above, the total number of electrodes is reduced by 1 because both electrode groups include a common electrode. In another example, a 43rd order Legendre sequence can be combined with an interleaving factor of 3 to produce a sensor having 127 receiving electrodes. Compared to the 129-electrode embodiment described above, the total number of electrodes is reduced by 2 because all three electrode groups include a common electrode. Other exemplary conditions that satisfy Y=(N-1)Z+1 are shown in the table below.

[0115]

[0116] In the table above, the preferred number of AFEs refers to the number of analog front ends (or differential receivers) that can preferably be provided so that a regular interleaving can be used on the sensor so that no two adjacent receive electrodes will be active in the same time slot. These are considered to be favorable conditions, but should not be construed as limiting in any way.

[0117] In some embodiments, it may be advantageous to generate a segmentation mask that is configured to segment portions of an image that have useful data from portions of the image that do not have useful data. For example, in a fingerprint sensor, it may be advantageous to remove non-contact areas from an image so that the image can be more accurately compared to a stored template image to verify the identity of a user.

[0118] Fig. 9Depicted are exemplary techniques for generating and using segmentation masks. These techniques can enhance the suitability of analyzing the resulting image using a matching algorithm (e.g., a matching algorithm for determining whether a fingerprint matches stored data). Block 902 shows the above reference Figure 1-2 , Figures 3A-3C , Figure 4A-4B , Figures 5A-5C , Figure 6-7 and Figures 8A-8B The obtained digital image. In block 904, the grayscale of the image can be inverted. In block 906, a Laplacian-like filter can be applied to the original image 902 and the inverted image 904 to produce two filtered images 908 (inverted and then filtered) and 910 (filtered). Using a Laplacian filter can help determine areas with high energy in the image (e.g., within a contact patch).

[0119] An exemplary Laplace filter is reproduced below.

[0120] -1 -1 -1 -1 -1 -1 0 0 0 -1 -1 0 16 0 -1 -1 0 0 0 -1 -1 -1 -1 -1 -1

[0121] Then, the pixel values ​​from the two Laplacian images 908, 910 can be added to produce image 912. Preferably, before adding the images 908, 910 to produce image 912, the negative pixel values ​​in the two images 908, 910 are clipped to zero. Image 912 can therefore represent the size (absolute value) of the Laplacian filtered image. In block 914, image 912 can be processed by blurring with a 3×3 boxcar averaging filter (i.e., a 3×3 identity matrix). In block 916, the blurred image can be thresholded to a value generally equal to the midpoint of the available grayscale. In block 918, the grayscale can be inverted. In block 920, the white area can be extended by 1 pixel in each direction. The resulting image 920 can be viewed as a segmentation mask 920. The segmentation mask 920 can be configured to indicate areas in the original image that contain information that can be used to most accurately determine whether the fingerprint captured in the original image matches the stored template. For example, black areas of the segmentation mask 920 may indicate areas in the original image 902 where fingerprint features are most clearly resolved.

[0122] In block 922, a segmentation mask 920 may be applied to the image 910. For example, pixels in the image 910 that overlap with black areas in the segmentation mask 920 may be retained, and pixels in the image 910 that overlap with white areas in the segmentation mask 920 may be removed. The image 922 may therefore contain portions of the original image 908 where fingerprint features are most clearly resolved, and other portions of the original image 908 (e.g., non-contact areas) may be removed. In block 924, the image 922 may be output to a matching algorithm or other processing technique to further enhance the image for analysis. Optionally, the segmentation mask may be applied after the image is analyzed. This may advantageously prevent the analysis from producing unwanted edge effects at the boundaries of the segmentation mask. Note that Fig. 9 The techniques shown in are merely exemplary, and other techniques for generating and using segmentation masks may be used.

[0123] Fig. 10A -C shows an exemplary technique for isolating regions of interest using segmentation masks. Fig. 10A Depicted are exemplary digital images interpreted using the modulation and demodulation techniques described herein.It was observed that periodic error patterns were visible in the image, particularly in the non-contact areas. Fig. 10B Shown by processing Fig. 10A An exemplary segmentation mask created for the image shown. Fig. 10C The result of applying the segmentation mask to the original image is shown. Observe that the non-contact regions have been removed from the image. Because these non-contact regions - and especially periodic error patterns in non-contact regions - can be problematic for matching algorithms, removing these regions from the image can improve matching accuracy. Fig. 10B The segmentation mask shown in can alternatively be used with reference Fig. 9 Describe the technique to create.

[0124] Fig.11 An exemplary method 1100 is depicted in which non-contact areas are removed by using grayscale clipping (optionally in conjunction with a segmentation mask). In step 1102, demodulated values ​​for pixels of a sensor area are obtained. This can be performed according to any of the methods described above. In step 1104, grayscale clipping is performed to remove pixels having values ​​above or below a threshold. Exemplary techniques for performing this step are described in more detail below. In step 1106, recovery values ​​are applied as described above. In some embodiments, global recovery values ​​can be used, and in other embodiments, corresponding recovery values ​​for each electrode group can be used. In some embodiments, recovery values ​​are applied before grayscale clipping is performed. In step 1108a, image processing techniques can be used to extract features of interest from the image. For example, the features of interest can be extracted as described above. Fig. 9A Laplacian filter may be applied as described above. At step 1108b, a segmentation mask may be created. At step 1110, the segmentation mask may be applied to the image. At step 1112, a matching algorithm may be used to match the resulting image to the recorded template. Optionally, grayscale cropping may be applied without using a segmentation mask. In such a case, steps 1106, 1108a, 1108b, and 1110 are omitted.

[0125] Fig. 12A and Fig. 12B It shows how grayscale clipping can be used to remove non-contact areas from an image. Fig. 12A shows an image constructed from the demodulated values ​​as described above, and Fig. 12B The same image after grayscale cropping has been applied is shown. A method for applying grayscale cropping is described herein. In the case of using a balanced modulation mode, the pixel values ​​of any given row will average to zero after modulation and demodulation. In addition, if a global recovery value is used for all pixels, the average value of each row will be equal after applying the global recovery value. Because contact areas generally return lower grayscale values ​​than non-contact areas, contact areas can be segmented from non-contact areas by removing pixel values ​​above or below a threshold from the image. For example, consider the case of using a balanced sequence. Before applying the recovery value, the average value of each row is zero, and the contact area is expected to have pixel values ​​below the average level, while the non-contact area is expected to have pixel values ​​above the average level. Therefore, it is possible to remove non-contact areas by removing all pixels with values ​​greater than a threshold (equal to zero) from the image. Optionally, the threshold can be set slightly higher or lower than zero to retain more data or further isolate the area of ​​interest. For example, the threshold can be set to 0.1, 0.5, 1.0, or 1.5 standard deviations above or below the average value of the pixel values ​​in the image. In embodiments using a global restoration value, grayscale clipping may be used alternatively or additionally after the global restoration value is applied. In some embodiments, pixels having values ​​higher than the global restoration value may be removed. In some embodiments, pixels having values ​​higher than a threshold value (the threshold value is defined as slightly higher or slightly lower than the global restoration value) may be removed. For example, in an image where the available grayscale range is from 0 to 255, a global restoration value of 128 (the midpoint between 0 and 255) may be used, and pixels having values ​​greater than or equal to 150, 170, 190, or 210 may be removed from the image. Note that the grayscale range may be arbitrarily defined, and the terms "higher" and "lower" are used with reference to exemplary embodiments where contact areas tend to produce lower pixel values. In embodiments where the grayscale range is defined differently, vice versa, and pixel values ​​below the threshold value may be removed to isolate areas of interest.

[0126] Another method of grayscale clipping is to multiply each image value by the highest possible image value divided by a defined threshold level, and then if the resulting image value exceeds the defined threshold, then the image value is set to the highest possible value. For example, for image values ​​ranging from 0 to 255 and a defined threshold of 191, each image value is multiplied by 255 / 191, and then if the resulting image value exceeds 255, then the image value is set equal to 255. Other methods of grayscale clipping may also be used.

[0127] Selecting an appropriate threshold can improve processing accuracy. In some embodiments, a threshold set to 75% of the maximum grayscale works well. For example, for an 8-bit grayscale image (range = [0, 255], threshold set to 192), all pixels above 192 can be forced to 255, and all remaining pixels (which are within the range [0, 192]) can be remapped to fill the range [0, 255]. Such remapping can be done by multiplication, lookup table, or any other suitable method. If the threshold is set too high, fewer unwanted non-contact pixels may be forced to white, which may be undesirable. However, if the threshold is set too low, more desired contact pixels may be forced to white, which may also be undesirable. Therefore, the choice of threshold may be important (especially when other mechanisms cause the grayscale range of contact pixels to overlap with the grayscale range of non-contact pixels). In such a case, thresholding can advantageously precede additional image processing steps (such as creating and using segmentation masks to prevent this problem).

[0128] Fig.13 A schematic diagram of an exemplary system 1300 for detecting a user's finger or other element is shown. System 1300 may include a sensor area, a memory 1310, a processor 1320, a transducer 1330, and a power supply 1340. In some embodiments, transducer 1330 may be embodied as a two-dimensional grid of receiving electrodes and transmitting electrodes as described above. In some embodiments, transducer 1330 may define a sensor area defined by a frame. In some embodiments, transducer 1330 may include multiple transducer circuits. Memory 1310 may store instructions or results of any processing steps, calculations, and / or determinations described herein. For example, memory may store one or more parameters from which modulation and / or demodulation modes may be derived. Processor 1320 may be configured to perform any of these processing steps, calculations, and / or determinations. In some embodiments, power supply 1340 may be a battery, a capacitor, an inductor, a generator, or other element capable of applying power. For example, power supply 1340 may include an inductor configured to harvest energy from a wireless field. For example, in a smart card, the power source may include a card terminal and / or a secure element configured to harvest energy.

[0129] Fig.14 An exemplary method 1400 for detecting a user's finger or other element is shown. The method may be performed by, for example, referring to Fig.13 The method can be performed by a system as described in the embodiment of the present invention. For example, the method can be performed by a system including a memory, a processor and a sensor area defined by a framework. The sensor area can include a receiving electrode set, and the receiving electrode set can include all receiving electrodes of the sensor area. The receiving electrode set can be divided into a plurality of electrode groups, and the plurality of electrode groups can include at least a first electrode group and a second electrode group. In step 1402, the signal received from each electrode in the corresponding electrode group can be modulated according to a modulation mode. In step 1404, a demodulation mode can be used to demodulate the signal received from each electrode in the corresponding electrode group or a value derived from the signal. In this way, a set of demodulation values ​​of the corresponding electrode group can be determined. In step 1406, the system determines whether data has been obtained from all desired electrode groups. If not, the process can return to step 1402 to collect data from the next electrode group. If data has been collected from all desired groups, the data collection process for the sensor line can be completed. The modulation mode and demodulation mode for each group can be the same, or they can be different. Optionally, the modulation mode and / or demodulation mode can be derived from the modulation parameters stored in the memory.

[0130] In some embodiments, the first electrode group may include a first electrode and a second electrode, and the first electrode and the second electrode are arranged in the sensor area such that no electrode in the first electrode group is disposed between the first electrode and the second electrode. Multiple electrode groups may be at least partially staggered such that one or more electrodes in the electrode set are disposed between the first electrode and the second electrode. As described above, the value Y may represent the number of electrodes in the receiving electrode set, the value N may represent the number of electrodes in the first electrode group, and the value Z may be one greater than the number of electrodes disposed between the first electrode and the second electrode. The system may be arranged such that Y≤2NZ. The system may alternatively be arranged such that any other preferred condition described above is satisfied. In some embodiments, multiple electrode groups may form a row of pixels defined along a transmitting electrode (e.g., see Figure 2 , Figure 3A and Figure 7 ). Executing steps 1402 and 1404 may result in data being collected for two pixels that are spaced apart by at least one-third, one-half, or ninety percent of the length of the pixel row. When determining the spacing between two pixels, the terms "one-third," "one-half," and "ninety percent" are meant to be inclusive. For example, pixel numbers 1 and 50 of a 100-pixel row are considered to be spaced apart by at least one-half of the length of the row.

[0131] In some embodiments, the modulation mode and demodulation mode can be selected so that steps 1402 and 1404 remove the average value from the signal received by the electrodes of each corresponding electrode group. In optional step 1408, a recovery value can be added to compensate for the removed average value. In some embodiments, the recovery value can be a global recovery value that is the same for each electrode of the plurality of electrode groups. In other embodiments, a corresponding recovery value can be applied to each electrode group. For example, as described above with respect to Figure 7 As described above, the corresponding restoration value can be determined by using the common electrode.

[0132] In optional step 1410, the region of interest of the image constructed from the data collected in steps 1402-1406 can be segmented from other regions of the image. For example, as described above, the contact area can be isolated from the non-contact area. In some embodiments, this can be performed by determining a segmentation mask based on the signals received from the plurality of electrode sets, and constructing a digital image based on the signals received from the plurality of electrode sets and the segmentation mask. In some embodiments, this can be performed as described with respect to Fig. 9 In optional step 1412, biometric parameters may be determined by analyzing the digital image. In embodiments using a segmentation mask, constructing the digital image using the segmentation mask may facilitate determining the biometric parameters by removing portions of the digital image that would otherwise be characterized by an error pattern having a spatial period substantially equal to the average distance between adjacent receive electrodes in the sensor area multiplied by Z.

[0133] In some embodiments, data capture performed via steps 1402-1406 can be accelerated by using multiple differential receivers. For example, the system can include at least a first differential receiver and a second differential receiver, the first differential receiver can be arranged to receive signals from electrodes in the first electrode group, and the second differential receiver can be arranged to receive signals from electrodes in the second electrode group. In a first interval, the first differential receiver can receive signals from electrodes in the first electrode group during the first time interval, while the second differential receiver receives signals from electrodes in the second electrode group. In some embodiments, the electrodes in the first electrode group and the second electrode group together define a superset, and the superset of electrodes can be interleaved with electrodes that are not in the superset, so that for any pair of two electrodes selected from the superset, at least one electrode that is not in the superset is disposed between the selected pair.

[0134] Although the subject matter of the present disclosure has been described and illustrated in considerable detail with reference to specific illustrative embodiments including various combinations and subcombinations of features, those skilled in the art will readily appreciate other embodiments as included within the scope of the present disclosure and variations and modifications of these other embodiments. Furthermore, the description of such embodiments, combinations, and subcombinations is not intended to convey that the claimed subject matter requires features or combinations of features other than those expressly recited in the claims. Accordingly, the scope of the present disclosure is intended to include all modifications and variations included within the spirit and scope of the appended claims.

[0135]

[0013] Various aspects of the disclosure may be implemented in one or more embodiments hereinafter.

[0136] 1) A system for detecting a user's finger or other element, the system comprising:

[0137] Memory;

[0138] A sensor area, wherein the sensor area includes a receiving electrode set, the receiving electrode set includes all receiving electrodes of the sensor area, the receiving electrode set includes a plurality of electrode groups, and the plurality of electrode groups includes at least a first electrode group;

[0139] processor, wherein the system is configured to:

[0140] Processing signals received by the plurality of electrode sets, wherein the step of processing the signals comprises, for each respective electrode set:

[0141] (a) modulating the signal received from each electrode in the corresponding electrode group according to a modulation pattern; and

[0142] (b) demodulating the signal received from each electrode in the corresponding electrode group or a value derived from the signal according to a demodulation mode, thereby determining a set of demodulated values ​​for the corresponding electrode group;

[0143] wherein the modulation mode and the demodulation mode are selected so that steps (a) and (b) remove an average value from the signals received by the electrodes in each corresponding electrode group;

[0144] The system is also configured to add a global restoration value to the demodulated value, the global restoration value being selected to compensate for the removed mean value, the global restoration value being the same for each electrode in the plurality of electrode groups.

[0145] 2) The system according to 1), wherein the sensor area is defined by a frame, the first electrode group includes a first electrode and a second electrode, the first electrode and the second electrode are arranged in the sensor area such that no electrode in the first electrode group is disposed between the first electrode and the second electrode;

[0146] wherein the plurality of electrode groups are at least partially staggered such that one or more electrodes in the set of receiving electrodes are disposed between the first electrode and the second electrode;

[0147] The value Y represents the number of electrodes in the receiving electrode set, the value N represents the number of electrodes in the first electrode group, the value Z is one greater than the number of electrodes arranged between the first electrode and the second electrode, and Y≤2NZ.

[0148] 3) The system according to 2), wherein:

[0149] All electrodes of the receiving electrode set are included in one or more electrode groups of the plurality of electrode groups;

[0150] At least one electrode in at least one electrode group in each of the plurality of electrode groups except the first electrode group is disposed between the first electrode and the second electrode.

[0151] 4) The system according to any one of 2) and 3), wherein Z is less than or equal to 6, N is greater than or equal to 23, and Y≤1.1×NZ.

[0152] 5) The system according to any one of 2)-4), wherein the modulation mode used for each electrode group is the same.

[0153] 6) The system according to any one of 1) to 5), wherein the system is further configured to:

[0154] determining a segmentation mask based on the signals received from the plurality of electrode sets;

[0155] constructing a digital image based on the signals received from the plurality of electrode sets and the segmentation mask; and

[0156] Based on the digital image, a biometric parameter is determined, wherein constructing the digital image using the segmentation mask facilitates determining the biometric parameter by removing image portions from the digital image that would otherwise be characterized by a periodic error pattern.

[0157] 7) The system according to any one of 1) to 6), wherein the system further comprises at least a first differential receiver and a second differential receiver, and the plurality of electrode groups comprises a second electrode group;

[0158] The first differential receiver is arranged to receive signals from electrodes in the first electrode set;

[0159] the second differential receiver being arranged to receive signals from electrodes in the second electrode set;

[0160] wherein the system is arranged such that during a first time interval, the first differential receiver receives signals from electrodes in the first electrode set and the second differential receiver receives signals from electrodes in the second electrode set; and

[0161] The electrodes in the first electrode group and the second electrode group together define a superset, and the superset of electrodes is interleaved with electrodes not in the superset so that for any pair of two electrodes selected from the superset, at least one electrode not in the superset is disposed between the selected pair.

[0162] 8) A system according to any one of 1)-7), wherein modulation parameters are stored in the memory, the modulation pattern is a matrix and includes a plurality of vectors arranged along a common dimension of the matrix, each of the plurality of vectors being derived from the modulation parameters.

[0163] 9) The system according to 8), wherein the demodulation mode is derived from the modulation parameters.

[0164] 10) The system of any one of 1)-9), wherein the global restoration value is approximately equal to a midpoint of a grayscale range used to construct a digital image based on the signals received from the plurality of electrode groups.

[0165] 11) A method for detecting a user's finger or other element, the method being executed by a system including a memory, a processor, and a sensor area, wherein the sensor area includes a receiving electrode set, the receiving electrode set includes all receiving electrodes of the sensor area, the receiving electrode set includes a plurality of electrode groups, the plurality of electrode groups includes at least a first electrode group, the method comprising:

[0166] For each respective electrode set in the plurality of electrode sets:

[0167] (a) modulating the signal received from each electrode in the corresponding electrode group according to a modulation pattern; and

[0168] (b) demodulating the signal received from each electrode in the corresponding electrode group or a value derived from the signal according to a demodulation mode, thereby determining a set of demodulated values ​​for the corresponding electrode group;

[0169] wherein the modulation mode and the demodulation mode are selected so that steps (a) and (b) remove an average value from the signal received by the electrodes in each corresponding electrode group; and

[0170] A global restoration value is added to the demodulated value, the global restoration value being selected to compensate for the removed mean value, the global restoration value being the same for each electrode in the plurality of electrode groups.

[0171] 12) The method according to 11), wherein the sensor area is defined by a frame, the first electrode group comprises a first electrode and a second electrode, the first electrode and the second electrode are arranged in the sensor area such that no electrode in the first electrode group is arranged between the first electrode and the second electrode;

[0172] The plurality of electrode groups are at least partially staggered such that one or more electrodes of the receive electrode set are disposed between the first electrode and the second electrode, the plurality of electrode groups forming a pixel row defined along the transmit electrode, the pixel row having a length;

[0173] A value Y represents the number of electrodes in the receiving electrode set, a value N represents the number of electrodes in the first electrode group, a value Z is one greater than the number of electrodes disposed between the first electrode and the second electrode, and Y≤2NZ; and

[0174] Performing steps (a) and (b) with respect to the first electrode set results in data being collected for two pixels spaced apart by at least half of the length of the row of pixels.

[0175] 13) The method according to 12), wherein:

[0176] All electrodes in the receiving electrode set are included in one or more electrode groups of the plurality of electrode groups;

[0177] At least one electrode in at least one electrode group in each of the plurality of electrode groups except the first electrode group is disposed between the first electrode and the second electrode.

[0178] 14) A method according to any one of 12) and 13), wherein Z is less than or equal to 6, N is greater than or equal to 23, Y≤1.1×NZ, and performing steps (a) and (b) with respect to the first electrode group results in data being collected for two pixels separated by at least ninety percent of the length of the pixel row.

[0179] 15) The method according to any one of 12)-14), wherein the modulation mode used for each electrode group is the same.

[0180] 16) The method according to any one of 11) to 15), further comprising:

[0181] determining a segmentation mask based on the signals received from the plurality of electrode sets;

[0182] constructing a digital image based on the signals received from the plurality of electrode sets and the segmentation mask, wherein constructing the digital image using the segmentation mask removes portions of the image containing periodic error patterns from the digital image; and

[0183] Based on the digital image, a biometric parameter is determined.

[0184] 17) The method according to any one of 11) to 16), wherein the system further comprises at least a first differential receiver and a second differential receiver, the plurality of electrode groups comprises a second electrode group, the first differential receiver is arranged to receive signals from electrodes in the first electrode group, and the second differential receiver is arranged to receive signals from electrodes in the second electrode group, and the method further comprises:

[0185] receiving, by the first differential receiver, signals from electrodes in the first electrode set during a first time interval; and

[0186] receiving, by the second differential receiver, signals from electrodes in the second electrode set during the first time interval, while the first differential receiver receives signals from electrodes in the first electrode set;

[0187] wherein the electrodes in the first electrode group and the second electrode group together define a superset, and the superset of electrodes is interleaved with electrodes not in the superset so that for any pair of two electrodes selected from the superset, at least one electrode not in the superset is disposed between the selected pair.

[0188] 18) The method according to any one of 11) to 17), further comprising:

[0189] A plurality of vectors are derived from the modulation parameters stored in the memory, the plurality of vectors together defining the modulation mode.

[0190] 19) The method according to 18) also includes deriving the demodulation mode from the modulation parameters.

[0191] 20) The method according to any one of 11)-19), wherein the global recovery value is approximately equal to the midpoint of the grayscale range used to construct a digital image based on the signals received from the multiple electrode groups.

[0192] 21) A system for detecting a user's finger or other element, the system comprising:

[0193] Memory;

[0194] a sensor area, the sensor area being defined by a frame, wherein the sensor area comprises a receiving electrode set, the receiving electrode set comprising all receiving electrodes of the sensor area, the receiving electrode set comprising a plurality of electrode groups, the plurality of electrode groups comprising at least a first electrode group and a second electrode group;

[0195] processor, wherein the system is configured to:

[0196] Processing signals received by the plurality of electrode sets, wherein the step of processing the signals comprises, for each respective electrode set:

[0197] (a) modulating the signal received from each electrode in the corresponding electrode group according to a modulation pattern; and

[0198] (b) demodulating the signal received from each electrode in the corresponding electrode group or a value derived from the signal according to a demodulation mode, thereby determining a set of demodulated values ​​for the corresponding electrode group;

[0199] wherein the first electrode group comprises a first electrode and a second electrode, the first electrode and the second electrode being arranged in the sensor region such that no electrode in the first electrode group is arranged between the first electrode and the second electrode;

[0200] The plurality of electrode groups are at least partially staggered such that one or more electrodes of the set of receive electrodes are disposed between the first electrode and the second electrode;

[0201] The value Y represents the number of electrodes in the receiving electrode set, the value N represents the number of electrodes in the first electrode group, the value Z is one greater than the number of electrodes arranged between the first electrode and the second electrode, and Y≤2NZ.

[0202] 22) The system according to 21), further wherein:

[0203] Substantially all electrodes of the receive electrode set are included in one or more of the plurality of electrode groups;

[0204] At least one electrode in at least one electrode group in each of the plurality of electrode groups except the first electrode group is disposed between the first electrode and the second electrode.

[0205] 23) The system according to any one of 21) and 22), wherein Z is less than or equal to 6, and N is greater than or equal to 23, and Y≤1.1×NZ.

[0206] 24) A system according to any one of 21)-23), wherein the modulation mode and the demodulation mode are selected so that steps (a) and (b) remove the average value from the signal received by the electrodes in each corresponding electrode group; and

[0207] The system is also configured to add a global restoration value to the demodulated value, the global restoration value being selected to compensate for the removed mean value, the global restoration value being the same for each electrode in the plurality of electrode groups.

[0208] 25) A system according to any one of 21)-23), wherein the modulation mode and the demodulation mode are selected so that steps (a) and (b) remove the average value from the signal received by the electrodes in each corresponding electrode group; and

[0209] Each electrode group of the plurality of electrode groups shares a common electrode; and

[0210] The system is configured to add, for each electrode group, a corresponding restored value to the demodulated value, the corresponding restored value being the same for electrodes within a given group, the corresponding restored value for a given electrode group being based on at least one demodulated value obtained for a pixel defined for the common electrode.

[0211] 26) A system according to any one of 21) to 25), wherein the system is further configured to:

[0212] determining a segmentation mask based on the signals received from the plurality of electrode sets;

[0213] constructing a digital image based on the signals received from the plurality of electrode sets and the segmentation mask; and

[0214] Determining biometric parameters based on the digital image, wherein constructing the digital image using the segmentation mask facilitates determining the biometric parameters by removing image portions from the digital image that would otherwise be characterized by an error pattern having a spatial period substantially equal to an average distance between adjacent receive electrodes in the sensor area multiplied by Z.

[0215] 27) A system according to any one of 21)-26), wherein the system further comprises at least a first differential receiver and a second differential receiver, and the plurality of electrode groups comprises a second electrode group;

[0216] The first differential receiver is arranged to receive signals from electrodes in the first electrode set;

[0217] the second differential receiver being arranged to receive signals from electrodes in the second electrode set;

[0218] wherein the system is arranged such that during a first time interval, the first differential receiver receives signals from electrodes in the first electrode set and the second differential receiver receives signals from electrodes in the second electrode set; and

[0219] The electrodes in the first electrode group and the second electrode group together define a superset, and the superset of electrodes is interleaved with electrodes not in the superset so that for any pair of two electrodes selected from the superset, at least one electrode not in the superset is disposed between the selected pair.

[0220] 28) A system according to any one of 21)-27), wherein modulation parameters are stored in the memory, the modulation pattern is a matrix and includes a plurality of vectors arranged along a common dimension of the matrix, each of the plurality of vectors being derived from the modulation parameters.

[0221] 29) A system according to 28), wherein the demodulation mode is derived from the modulation parameters.

[0222] 30) A system according to any one of 21)-29), wherein the modulation mode used for each electrode group is the same.

[0223] 31) A method for detecting a user's finger or other element, the method being performed by a system including a memory, a processor, and a sensor area defined by a frame, wherein the sensor area includes a receiving electrode set, the receiving electrode set includes all receiving electrodes of the sensor area, the receiving electrode set includes a plurality of electrode groups, the plurality of electrode groups include at least a first electrode group and a second electrode group, the method comprising:

[0224] For each electrode set in the plurality of electrode sets:

[0225] (a) modulating the signal received from each electrode in the corresponding electrode group according to a modulation pattern; and

[0226] (b) demodulating the signal received from each electrode in the corresponding electrode group or a value derived from the signal according to a demodulation mode, thereby determining a set of demodulated values ​​for the corresponding electrode group;

[0227] wherein the first electrode group comprises a first electrode and a second electrode, the first electrode and the second electrode being arranged in the sensor region such that no electrode in the first electrode group is arranged between the first electrode and the second electrode;

[0228] The plurality of electrode groups are at least partially staggered such that one or more electrodes of the receive electrode set are disposed between the first electrode and the second electrode; and

[0229] The value Y represents the number of electrodes in the receiving electrode set, the value N represents the number of electrodes in the first electrode group, the value Z is one greater than the number of electrodes arranged between the first electrode and the second electrode, and Y≤2NZ.

[0230] 32) The method according to 31), further wherein:

[0231] All electrodes of the receiving electrode set are included in one or more electrode groups of the plurality of electrode groups;

[0232] At least one electrode in at least one electrode group in each of the plurality of electrode groups except the first electrode group is disposed between the first electrode and the second electrode.

[0233] 33) A method according to any one of 31) and 32), wherein Z is less than or equal to 6, and N is greater than or equal to 23, Y≤1.1×NZ, and performing steps (a) and (b) with respect to the first electrode group results in data being collected for two pixels separated by at least ninety percent of the length of the pixel row.

[0234] 34) A method according to any one of 31) to 33), wherein the modulation mode and the demodulation mode are selected so that steps (a) and (b) remove the average value from the signal received by the electrodes in each corresponding electrode group, the method further comprising:

[0235] A global restored value is added to the demodulated value, the restored value being selected to compensate for the removed mean value, the restored value being the same for each electrode in the plurality of electrode groups.

[0236] 35) A method according to any one of 31)-33), wherein the modulation mode and the demodulation mode are selected so that steps (a) and (b) remove the average value from the signal received by the electrodes in each corresponding electrode group, and each electrode group in the plurality of electrode groups shares a common electrode, the method further comprising:

[0237] A respective restored value is added to the demodulated value for each electrode group, the respective restored value being the same for the electrodes within a given group, the respective restored value for a given electrode group being based on at least one demodulated value obtained for a pixel defined for the common electrode.

[0238] 36) The method according to any one of 31) to 35), further comprising:

[0239] determining a segmentation mask based on the signals received from the plurality of electrode sets;

[0240] constructing a digital image based on the signals received from the plurality of electrode sets and the segmentation mask; and

[0241] Based on the digital image, biometric parameters are determined, wherein constructing the digital image using the segmentation mask facilitates determining the biometric parameters by removing image portions from the digital image that would otherwise be characterized by an error pattern having a spatial period substantially equal to an average distance between adjacent receive electrodes in the sensor area multiplied by Z.

[0242] 37) The method according to any one of 31) to 36), wherein the system further comprises at least a first differential receiver and a second differential receiver, the plurality of electrode groups comprises a second electrode group, the first differential receiver is arranged to receive signals from electrodes in the first electrode group, and the second differential receiver is arranged to receive signals from electrodes in the second electrode group, and the method further comprises:

[0243] receiving, by the first differential receiver, signals from electrodes in the first electrode set during a first time interval; and

[0244] receiving, by the second differential receiver, signals from electrodes in the second electrode set during the first time interval, while the first differential receiver receives signals from electrodes in the first electrode set;

[0245] wherein the electrodes in the first electrode group and the second electrode group together define a superset, and the superset of electrodes is interleaved with electrodes not in the superset so that for any pair of two electrodes selected from the superset, at least one electrode not in the superset is disposed between the selected pair.

[0246] 38) The method according to any one of 31) to 37), further comprising:

[0247] A plurality of vectors are derived from the modulation parameters stored in the memory, the plurality of vectors together defining the modulation mode.

[0248] 39) The method according to 38) also includes deriving the demodulation mode from the modulation parameters.

[0249] 40) The method according to any one of 31)-39), wherein the modulation mode used for each electrode group is the same.

[0250] 41) A system for detecting a user's finger or other element, the system comprising:

[0251] Memory;

[0252] A plurality of electrode groups, each of the plurality of electrode groups comprising a corresponding reference electrode whose real signal value is a predetermined value, the plurality of electrode groups comprising at least a first electrode group;

[0253] processor, wherein the system is configured to:

[0254] Processing signals received by the plurality of electrode sets, wherein the step of processing the signals comprises, for each respective electrode set:

[0255] (a) modulating the signal received from each electrode in the corresponding electrode group according to a modulation pattern;

[0256] (b) demodulating the signal received from each electrode in the corresponding electrode group or a value derived from the signal according to a demodulation mode, thereby determining a set of demodulated values ​​for the corresponding electrode group;

[0257] wherein the modulation mode and the demodulation mode are selected so that steps (a) and (b) remove an average value from the signal received by the electrodes in each corresponding electrode group; and

[0258] (c) restoring the average value to the signal received from each electrode in the corresponding electrode group or a value derived from the signal using the predetermined value of the reference electrode in the corresponding electrode group.

[0259] 42) The system according to 41), further wherein:

[0260] the set of demodulated values ​​of the first electrode group comprises a demodulated value (K–M) of the reference electrode, wherein K=the true signal value of the reference electrode included in the first electrode group, and M=the average of the true signal values ​​of each electrode included in the group; and

[0261] Step (c) is performed by adding an offset value to each demodulated value in the set of demodulated values, wherein the offset value is selected such that a sum of the offset value and the demodulated value of the reference electrode is equal to K.

[0262] 43) A system according to any one of 41)-42), wherein each signal received from an electrode in the first electrode group includes a signal received from the reference electrode of the first electrode group, including a corresponding carrier component;

[0263] Therein, the modulation pattern is selected such that the respective carrier components of the electrodes in the first electrode group sum to substantially zero in any given time slot of the modulation pattern.

[0264] 44) The system according to any one of 41)-43) further comprises a carrier injection node, wherein the carrier injection node comprises a carrier injection transmitting electrode and a reference carrier electrode;

[0265] Wherein, the reference electrode of the first electrode group is coupled to the reference carrier electrode, so that the signal received from the reference electrode of the first electrode group includes the carrier component applied to the reference carrier electrode by the injection transmitting electrode.

[0266] 45) The system of 44) wherein the carrier injection node is electrically isolated from an area of ​​the system configured to detect the user's finger or other element.

[0267] 46) A system according to any one of 44)-45), wherein the carrier injection node is located within an analog front end, and the analog front end is configured to receive the signal from the multiple electrode groups.

[0268] 47) A system according to 43), wherein the carrier component of the reference electrode of the first electrode group is computationally determined and synthesized.

[0269] 48) A system according to any one of 41)-47), wherein the reference electrode of the first electrode group is arranged so that when the system detects a user's finger or other element, the reference electrode is exposed to noise received from the user's finger or other element.

[0270] 49) The system according to 48), wherein the system is further configured to select the reference electrode of the first electrode group from a plurality of available reference electrodes;

[0271] Wherein, the step of selecting the reference electrode comprises:

[0272] (a) measuring noise received from a finger or other element of the user via each of the plurality of available reference electrodes; and

[0273] (b) Selecting the available electrode for which the measured noise received from the user's finger or other element is greatest.

[0274] 50) The system according to any one of 41)-48) further includes:

[0275] a first transmit electrode set comprising one or more electrodes configured to apply a first carrier signal;

[0276] a second transmit electrode set comprising one or more electrodes configured to apply a second carrier signal;

[0277] wherein the reference electrode of the first electrode group intersects with the first emitting electrode set but does not intersect with the second emitting electrode set; and

[0278] Wherein, the reference electrode of the second electrode group among the plurality of electrode groups intersects with the second transmitting electrode set but does not intersect with the first transmitting electrode set.

[0279] 51) The system according to 50), further wherein:

[0280] The system is configured to receive a signal from the first electrode set at a first time, during which the second set of transmit electrodes applies the second carrier signal and the first set of transmit electrodes does not apply the first carrier signal; and

[0281] The system is configured to receive a signal from the second electrode set at a second time, during which the first set of transmit electrodes applies the first carrier signal and the second set of transmit electrodes does not apply the second carrier signal.

[0282] 52) A system according to any one of 41)-51), wherein a common reference electrode is included in each electrode group of the plurality of electrode groups.

[0283] 53) A method for detecting a user's finger or other element, the method being performed at least in part by a system comprising a plurality of electrode groups, each of the plurality of electrode groups comprising a corresponding reference electrode whose true signal value is a predetermined value, the plurality of electrode groups comprising at least a first electrode group, the method comprising:

[0284] For each corresponding electrode group in the plurality of electrode groups, processing a signal received by the corresponding electrode group is performed at least by the following steps:

[0285] (a) modulating the signal received from each electrode in the corresponding electrode group according to a modulation pattern;

[0286] (b) demodulating the signal received from each electrode in the corresponding electrode group or a value derived from the signal according to a demodulation mode, thereby determining a set of demodulated values ​​for the corresponding electrode group;

[0287] wherein the modulation mode and the demodulation mode are selected so that steps (a) and (b) remove an average value from the signal received by the electrodes in each corresponding electrode group; and

[0288] (c) restoring the average value to the signal received from each electrode in the corresponding electrode group or a value derived from the signal using the predetermined value of the reference electrode of the corresponding electrode group.

[0289] 54) The method according to 53), further wherein:

[0290] the set of demodulated values ​​of the first electrode group comprises a demodulated value (K–M) of the reference electrode, wherein K=the true signal value of the reference electrode included in the first electrode group, and M=the average of the true signal values ​​of each electrode included in the group; and

[0291] Step (c) is performed by adding an offset value to each demodulated value in the set of demodulated values, wherein the offset value is selected such that a sum of the offset value and the demodulated value of the reference electrode is equal to K.

[0292] 55) The method according to any one of 53)-54), wherein each signal received from an electrode in the first electrode group includes a signal received from the reference electrode of the first electrode group, including a corresponding carrier component;

[0293] Therein, the modulation pattern is selected such that the respective carrier components of the electrodes in the first electrode group sum to substantially zero in any given time slot of the modulation pattern.

[0294] 56) The method according to any one of 53)-55), wherein the system further comprises a carrier injection node, the carrier injection node comprising a carrier injection transmitting electrode and a reference carrier electrode coupled to the reference electrode of the first electrode group, the method further comprising:

[0295] A signal including a carrier component applied to the reference carrier electrode by the injection transmit electrode is received from the reference electrode of the first electrode set.

[0296] 57) A method according to 56), wherein the carrier injection node is electrically isolated from an area of ​​the system that detects the user's finger or other element.

[0297] 58) A method according to any one of 56)-57), wherein the carrier injection node is located within an analog front end, and the analog front end is configured to receive the signal from the multiple electrode groups.

[0298] 59) The method according to 55) also includes computationally determining and synthesizing the carrier component of the reference electrode.

[0299] 60) The method according to any one of 53)-59) also includes receiving a signal from the reference electrode of the first electrode group including noise received from the user's finger or other elements.

[0300] 61) The method according to 60) further includes:

[0301] selecting a reference electrode of the first electrode set from a plurality of available reference electrodes;

[0302] Wherein, the step of selecting the reference electrode comprises:

[0303] (a) measuring noise received from a finger or other element of the user via each of the plurality of available reference electrodes; and

[0304] (b) Selecting the available electrode for which the measured noise received from the user's finger or other element is greatest.

[0305] 62) The method according to any one of 53) to 61), wherein the system for executing the method further comprises:

[0306] a first transmit electrode set comprising one or more electrodes configured to apply a first carrier signal;

[0307] a second transmit electrode set comprising one or more electrodes configured to apply a second carrier signal;

[0308] wherein the reference electrode of the first electrode group intersects with the first emitting electrode set but does not intersect with the second emitting electrode set; and

[0309] Wherein, the reference electrode of the second electrode group among the plurality of electrode groups intersects with the second transmitting electrode set but does not intersect with the first transmitting electrode set.

[0310] 63) The method according to 62) further includes:

[0311] receiving a signal from the first electrode set at a first time, during which the second transmitting electrode set applies the second carrier signal and the first transmitting electrode set does not apply the first carrier signal; and

[0312] A signal is received from the second electrode group at a second time, during which the first set of transmitting electrodes applies the first carrier signal and the second set of transmitting electrodes does not apply the second carrier signal.

[0313] 64) A method according to any one of 53)-63), wherein a common reference electrode is included in each electrode group of the plurality of electrode groups.

Claims

1. A system for detecting a user's finger or other element, the system comprising: Memory; A sensor area, wherein the sensor area includes a receiving electrode set, the receiving electrode set includes all receiving electrodes of the sensor area, the receiving electrode set includes a plurality of electrode groups, and the plurality of electrode groups includes at least a first electrode group; processor, wherein the system is configured to: Processing signals received by the plurality of electrode sets, wherein the step of processing the signals comprises, for each respective electrode set: (a) modulating the signal received from each electrode in the corresponding electrode group according to a modulation pattern; and (b) demodulating the signal received from each electrode in the corresponding electrode group or a value derived from the signal according to a demodulation mode, thereby determining a set of demodulated values ​​for the corresponding electrode group; wherein the modulation mode and the demodulation mode are selected so that steps (a) and (b) remove an average value from the signals received by the electrodes in each corresponding electrode group; The system is also configured to add a global restoration value to the demodulated value, the global restoration value being selected to compensate for the removed mean value, the global restoration value being the same for each electrode in the plurality of electrode groups.

2. The system according to claim 1, wherein: The sensor area is defined by a frame, the first electrode group includes a first electrode and a second electrode, the first electrode and the second electrode are arranged in the sensor area such that no electrode of the first electrode group is disposed between the first electrode and the second electrode; wherein the plurality of electrode groups are at least partially staggered such that one or more electrodes in the set of receiving electrodes are disposed between the first electrode and the second electrode; The value Y represents the number of electrodes in the receiving electrode set, the value N represents the number of electrodes in the first electrode group, the value Z is one greater than the number of electrodes arranged between the first electrode and the second electrode, and Y≤2NZ.

3. The system of claim 2, wherein: All electrodes of the receiving electrode set are included in one or more electrode groups of the plurality of electrode groups; At least one electrode in at least one electrode group in each of the plurality of electrode groups except the first electrode group is disposed between the first electrode and the second electrode.

4. A system according to any one of claims 2 and 3, wherein: Z is less than or equal to 6, N is greater than or equal to 23, and Y≤1.1×NZ.

5. The system according to any one of claims 2 and 3, wherein: The modulation pattern is the same for each electrode group.

6. The system according to any one of claims 1 to 3, wherein: The system is also configured to: determining a segmentation mask based on the signals received from the plurality of electrode sets; constructing a digital image based on the signals received from the plurality of electrode sets and the segmentation mask; and Based on the digital image, a biometric parameter is determined, wherein constructing the digital image using the segmentation mask facilitates determining the biometric parameter by removing image portions from the digital image that would otherwise be characterized by a periodic error pattern.

7. The system according to any one of claims 1 to 3, wherein: The system also includes at least a first differential receiver and a second differential receiver, and the plurality of electrode sets includes a second electrode set; The first differential receiver is arranged to receive signals from electrodes in the first electrode set; the second differential receiver being arranged to receive signals from electrodes in the second electrode set; wherein the system is arranged such that during a first time interval, the first differential receiver receives signals from electrodes in the first electrode set and the second differential receiver receives signals from electrodes in the second electrode set; and The electrodes in the first electrode group and the second electrode group together define a superset, and the superset of electrodes is interleaved with electrodes not in the superset so that for any pair of two electrodes selected from the superset, at least one electrode not in the superset is disposed between the selected pair.

8. The system according to any one of claims 1 to 3, wherein: Modulation parameters are stored in the memory, the modulation pattern is a matrix and comprises a plurality of vectors arranged along a common dimension of the matrix, each vector of the plurality of vectors being derived from the modulation parameters.

9. The system according to claim 8, wherein: The demodulation mode is derived from the modulation parameters.

10. The system according to any one of claims 1 to 3, wherein: The global restoration value is equal to a midpoint of a grayscale range used to construct a digital image based on the signals received from the plurality of electrode sets.

11. A method for detecting a user's finger or other element, the method being performed by a system comprising a memory, a processor, and a sensor area, wherein: The sensor area includes a receiving electrode set, the receiving electrode set includes all receiving electrodes of the sensor area, the receiving electrode set includes a plurality of electrode groups, the plurality of electrode groups includes at least a first electrode group, and the method includes: For each respective electrode set in the plurality of electrode sets: (a) modulating a signal received from each electrode in the corresponding electrode group according to a modulation pattern; and (b) demodulating the signal received from each electrode in the corresponding electrode group or a value derived from the signal according to a demodulation mode, thereby determining a set of demodulated values ​​for the corresponding electrode group; wherein the modulation mode and the demodulation mode are selected so that steps (a) and (b) remove an average value from the signal received by the electrodes in each corresponding electrode group; and A global restoration value is added to the demodulated value, the global restoration value being selected to compensate for the removed mean value, the global restoration value being the same for each electrode in the plurality of electrode groups.

12. The method according to claim 11, wherein: The sensor area is defined by a frame, the first electrode group includes a first electrode and a second electrode, the first electrode and the second electrode are arranged in the sensor area such that no electrode of the first electrode group is disposed between the first electrode and the second electrode; The plurality of electrode groups are at least partially staggered such that one or more electrodes of the receive electrode set are disposed between the first electrode and the second electrode, the plurality of electrode groups forming a pixel row defined along the transmit electrode, the pixel row having a length; The value Y represents the number of electrodes in the receiving electrode set, the value N represents the number of electrodes in the first electrode group, the value Z is one greater than the number of electrodes arranged between the first electrode and the second electrode, and Y≤2NZ; and Performing steps (a) and (b) with respect to the first electrode set results in data being collected for two pixels spaced apart by at least half of the length of the row of pixels.

13. The method according to claim 12, wherein: All electrodes in the receiving electrode set are included in one or more electrode groups of the plurality of electrode groups; At least one electrode in at least one electrode group in each of the plurality of electrode groups except the first electrode group is disposed between the first electrode and the second electrode.

14. The method according to any one of claims 12 and 13, wherein: Z is less than or equal to 6, N is greater than or equal to 23, Y≤1.1×NZ, and performing steps (a) and (b) with respect to the first electrode group results in data being collected for two pixels separated by at least ninety percent of the length of the pixel row.

15. The method according to any one of claims 12 and 13, wherein: The modulation pattern is the same for each electrode group.

16. The method according to any one of claims 11 to 13, further comprising: determining a segmentation mask based on the signals received from the plurality of electrode sets; constructing a digital image based on the signals received from the plurality of electrode sets and the segmentation mask, wherein constructing the digital image using the segmentation mask removes image portions containing periodic error patterns from the digital image; and Based on the digital image, a biometric parameter is determined.

17. The method according to any one of claims 11 to 13, wherein: The system further comprises at least a first differential receiver and a second differential receiver, the plurality of electrode groups comprising a second electrode group, the first differential receiver being arranged to receive signals from electrodes in the first electrode group, and the second differential receiver being arranged to receive signals from electrodes in the second electrode group, the method further comprising: receiving, by the first differential receiver, signals from electrodes in the first electrode set during a first time interval; and receiving, by the second differential receiver, signals from electrodes in the second electrode set during the first time interval, while the first differential receiver receives signals from electrodes in the first electrode set; wherein the electrodes in the first electrode group and the second electrode group together define a superset, and the superset of electrodes is interleaved with electrodes not in the superset such that for any pair of two electrodes selected from the superset, at least one electrode not in the superset is disposed between the selected pair.

18. The method according to any one of claims 11 to 13, further comprising: A plurality of vectors are derived from the modulation parameters stored in the memory, the plurality of vectors together defining the modulation mode.

19. The method of claim 18, further comprising deriving the demodulation mode from the modulation parameters.

20. The method according to any one of claims 11 to 13, wherein: The global restoration value is equal to a midpoint of a grayscale range used to construct a digital image based on the signals received from the plurality of electrode sets.

21. A system for detecting a user's finger or other element, the system comprising: Memory; a sensor area, the sensor area being defined by a frame, wherein the sensor area comprises a receiving electrode set, the receiving electrode set comprising all receiving electrodes of the sensor area, the receiving electrode set comprising a plurality of electrode groups, the plurality of electrode groups comprising at least a first electrode group and a second electrode group; processor, wherein the system is configured to: Processing signals received by the plurality of electrode sets, wherein the step of processing the signals comprises, for each respective electrode set: (a) modulating the signal received from each electrode in the corresponding electrode group according to a modulation pattern; and (b) demodulating the signal received from each electrode in the corresponding electrode group or a value derived from the signal according to a demodulation mode, thereby determining a set of demodulated values ​​for the corresponding electrode group; wherein the first electrode group comprises a first electrode and a second electrode, the first electrode and the second electrode being arranged in the sensor region such that no electrode in the first electrode group is arranged between the first electrode and the second electrode; The plurality of electrode groups are at least partially staggered such that one or more electrodes of the set of receive electrodes are disposed between the first electrode and the second electrode; The value Y represents the number of electrodes in the receiving electrode set, the value N represents the number of electrodes in the first electrode group, the value Z is one greater than the number of electrodes arranged between the first electrode and the second electrode, and Y≤2NZ.

22. The system of claim 21, further wherein: All electrodes of the receiving electrode set are included in one or more electrode groups of the plurality of electrode groups; At least one electrode in at least one electrode group in each of the plurality of electrode groups except the first electrode group is disposed between the first electrode and the second electrode.

23. The system according to any one of claims 21 and 22, wherein: Z is less than or equal to 6, and N is greater than or equal to 23, and Y≤1.1×NZ.

24. The system according to any one of claims 21 and 22, wherein: The modulation mode and the demodulation mode are selected so that steps (a) and (b) remove an average value from the signals received by the electrodes in each respective electrode group; and The system is also configured to add a global restoration value to the demodulated value, the global restoration value being selected to compensate for the removed mean value, the global restoration value being the same for each electrode in the plurality of electrode groups.

25. The system according to any one of claims 21 and 22, wherein: The modulation mode and the demodulation mode are selected so that steps (a) and (b) remove an average value from the signals received by the electrodes in each respective electrode group; and Each electrode group in the plurality of electrode groups shares a common electrode; and The system is configured to add, for each electrode group, a corresponding restored value to the demodulated value, the corresponding restored value being the same for electrodes within a given group, the corresponding restored value for a given electrode group being based on at least one demodulated value obtained for a pixel defined for the common electrode.

26. The system according to any one of claims 21 and 22, wherein: The system is also configured to: determining a segmentation mask based on the signals received from the plurality of electrode sets; constructing a digital image based on the signals received from the plurality of electrode sets and the segmentation mask; and Determining biometric parameters based on the digital image, wherein constructing the digital image using the segmentation mask facilitates determining the biometric parameters by removing image portions from the digital image that would otherwise be characterized by an error pattern having a spatial period equal to an average distance between adjacent receive electrodes in the sensor area multiplied by Z.

27. The system according to any one of claims 21 and 22, wherein: The system also includes at least a first differential receiver and a second differential receiver, and the plurality of electrode sets includes a second electrode set; The first differential receiver is arranged to receive signals from electrodes in the first electrode set; the second differential receiver being arranged to receive signals from electrodes in the second electrode set; wherein the system is arranged such that during a first time interval, the first differential receiver receives signals from electrodes in the first electrode set and the second differential receiver receives signals from electrodes in the second electrode set; and The electrodes in the first electrode group and the second electrode group together define a superset, and the superset of electrodes is interleaved with electrodes not in the superset so that for any pair of two electrodes selected from the superset, at least one electrode not in the superset is disposed between the selected pair.

28. The system according to any one of claims 21 and 22, wherein: Modulation parameters are stored in the memory, the modulation pattern is a matrix and comprises a plurality of vectors arranged along a common dimension of the matrix, each vector of the plurality of vectors being derived from the modulation parameters.

29. The system of claim 28, wherein: The demodulation mode is derived from the modulation parameters.

30. The system according to any one of claims 21 and 22, wherein: The modulation pattern is the same for each electrode group.

31. A method for detecting a user's finger or other element, the method being performed by a system comprising a memory, a processor, and a sensor area defined by a frame, wherein: The sensor area includes a receiving electrode set, the receiving electrode set includes all receiving electrodes of the sensor area, the receiving electrode set includes a plurality of electrode groups, the plurality of electrode groups include at least a first electrode group and a second electrode group, and the method includes: For each respective electrode set in the plurality of electrode sets: (a) modulating a signal received from each electrode in the corresponding electrode group according to a modulation pattern; and (b) demodulating the signal received from each electrode in the corresponding electrode group or a value derived from the signal according to a demodulation mode, thereby determining a set of demodulated values ​​for the corresponding electrode group; wherein the first electrode group comprises a first electrode and a second electrode, the first electrode and the second electrode being arranged in the sensor region such that no electrode in the first electrode group is arranged between the first electrode and the second electrode; The plurality of electrode groups are at least partially staggered such that one or more electrodes of the receive electrode set are disposed between the first electrode and the second electrode; and The value Y represents the number of electrodes in the receiving electrode set, the value N represents the number of electrodes in the first electrode group, the value Z is one greater than the number of electrodes arranged between the first electrode and the second electrode, and Y≤2NZ.

32. The method according to claim 31, further wherein: All electrodes of the receiving electrode set are included in one or more electrode groups of the plurality of electrode groups; At least one electrode in at least one electrode group in each of the plurality of electrode groups except the first electrode group is disposed between the first electrode and the second electrode.

33. The method according to any one of claims 31 and 32, wherein: Z is less than or equal to 6, and N is greater than or equal to 23, Y≤1.1×NZ, and performing steps (a) and (b) with respect to the first electrode group results in data being collected for two pixels spaced apart by at least ninety percent of the length of the pixel row.

34. The method according to any one of claims 31 and 32, wherein: The modulation mode and the demodulation mode are selected so that steps (a) and (b) remove an average value from the signal received by the electrodes in each respective electrode group, the method further comprising: A global restored value is added to the demodulated value, the restored value being selected to compensate for the removed mean value, the restored value being the same for each electrode in the plurality of electrode groups.

35. The method according to any one of claims 31 and 32, wherein: The modulation mode and the demodulation mode are selected so that steps (a) and (b) remove an average value from the signal received by the electrodes in each respective electrode group, and each electrode group in the plurality of electrode groups shares a common electrode, the method further comprising: A respective restored value is added to the demodulated value for each electrode group, the respective restored value being the same for the electrodes within a given group, the respective restored value for a given electrode group being based on at least one demodulated value obtained for a pixel defined for the common electrode.

36. The method according to any one of claims 31 and 32, further comprising: determining a segmentation mask based on the signals received from the plurality of electrode sets; constructing a digital image based on the signals received from the plurality of electrode sets and the segmentation mask; and Based on the digital image, biometric parameters are determined, wherein constructing the digital image using the segmentation mask facilitates determining the biometric parameters by removing image portions from the digital image that would otherwise be characterized by an error pattern having a spatial period equal to an average distance between adjacent receive electrodes in the sensor area multiplied by Z.

37. The method according to any one of claims 31 and 32, wherein: The system further comprises at least a first differential receiver and a second differential receiver, the plurality of electrode groups comprising a second electrode group, the first differential receiver being arranged to receive signals from electrodes in the first electrode group, and the second differential receiver being arranged to receive signals from electrodes in the second electrode group, the method further comprising: receiving, by the first differential receiver, signals from electrodes in the first electrode set during a first time interval; and receiving, by the second differential receiver, signals from electrodes in the second electrode set during the first time interval, while the first differential receiver receives signals from electrodes in the first electrode set; wherein the electrodes in the first electrode group and the second electrode group together define a superset, and the superset of electrodes is interleaved with electrodes not in the superset such that for any pair of two electrodes selected from the superset, at least one electrode not in the superset is disposed between the selected pair.

38. The method according to any one of claims 31 and 32, further comprising: A plurality of vectors are derived from the modulation parameters stored in the memory, the plurality of vectors together defining the modulation mode.

39. The method of claim 38, further comprising deriving the demodulation mode from the modulation parameters.

40. The method according to any one of claims 31 and 32, wherein: The modulation pattern is the same for each electrode group.

41. A system for detecting a user's finger or other element, the system comprising: Memory; A plurality of electrode groups, each of the plurality of electrode groups comprising a corresponding reference electrode whose real signal value is a predetermined value, the plurality of electrode groups comprising at least a first electrode group; processor, wherein the system is configured to: Processing signals received by the plurality of electrode sets, wherein the step of processing the signals comprises, for each respective electrode set: (a) modulating the signal received from each electrode in the corresponding electrode group according to a modulation pattern; (b) demodulating the signal received from each electrode in the corresponding electrode group or a value derived from the signal according to a demodulation mode, thereby determining a set of demodulated values ​​for the corresponding electrode group; wherein the modulation mode and the demodulation mode are selected so that steps (a) and (b) remove an average value from the signal received by the electrodes in each corresponding electrode group; and (c) restoring the average value to the signal received from each electrode in the corresponding electrode group or a value derived from the signal using the predetermined value of the reference electrode in the corresponding electrode group.

42. The system of claim 41, further wherein: the set of demodulated values ​​of the first electrode group comprises a demodulated value (K-M) of the reference electrode, wherein K=the true signal value of the reference electrode included in the first electrode group, and M=the average of the true signal values ​​of each electrode included in the group; and Step (c) is performed by adding an offset value to each demodulated value in the set of demodulated values, wherein the offset value is selected such that a sum of the offset value and the demodulated value of the reference electrode is equal to K.

43. The system according to any one of claims 41-42, wherein: each signal received from an electrode in the first electrode set, including a signal received from the reference electrode of the first electrode set, comprises a corresponding carrier component; Therein, the modulation pattern is selected so that the corresponding carrier components of the electrodes in the first electrode group sum to zero in any given time slot of the modulation pattern.

44. The system according to any one of claims 41-42, further comprising a carrier injection node, the carrier injection node comprising a carrier injection transmission electrode and a reference carrier electrode; in, The reference electrode of the first electrode set is coupled to the reference carrier electrode such that a signal received from the reference electrode of the first electrode set includes a carrier component applied to the reference carrier electrode by the injection transmit electrode.

45. The system of claim 44, wherein: The carrier injection node is electrically isolated from an area of ​​the system configured to detect the user's finger or other element.

46. ​​The system of claim 44, wherein: The carrier injection node is located within an analog front end configured to receive the signals from the plurality of electrode groups.

47. The system of claim 43, wherein: The carrier component of the reference electrode of the first electrode group is computationally determined and synthesized.

48. The system of any one of claims 41-42, wherein: The reference electrode of the first electrode group is arranged such that when the system detects a user's finger or other element, the reference electrode is exposed to noise received from the user's finger or other element.

49. The system of claim 48, wherein: The system is further configured to select the reference electrode of the first electrode set from a plurality of available reference electrodes; Wherein, the step of selecting the reference electrode comprises: (a) measuring noise received from a finger or other element of the user via each of the plurality of available reference electrodes; and (b) Selecting the available electrode for which the measured noise received from the user's finger or other element is greatest.

50. The system of any one of claims 41-42, further comprising: a first transmit electrode set comprising one or more electrodes configured to apply a first carrier signal; a second transmit electrode set comprising one or more electrodes configured to apply a second carrier signal; wherein the reference electrode of the first electrode group intersects with the first emitting electrode set but does not intersect with the second emitting electrode set; and Wherein, the reference electrode of the second electrode group among the plurality of electrode groups intersects with the second transmitting electrode set but does not intersect with the first transmitting electrode set.

51. The system of claim 50, further wherein: The system is configured to receive a signal from the first electrode set at a first time, during which the second set of transmit electrodes applies the second carrier signal and the first set of transmit electrodes does not apply the first carrier signal; and The system is configured to receive a signal from the second electrode set at a second time, during which the first set of transmit electrodes applies the first carrier signal and the second set of transmit electrodes does not apply the second carrier signal.

52. The system of any one of claims 41-42, wherein: A common reference electrode is included in each of the plurality of electrode sets.

53. A method for detecting a user's finger or other element, the method being performed at least in part by a system comprising a plurality of electrode groups, each of the plurality of electrode groups comprising a corresponding reference electrode whose true signal value is a predetermined value, the plurality of electrode groups comprising at least a first electrode group, the method comprising: For each corresponding electrode group in the plurality of electrode groups, processing a signal received by the corresponding electrode group is performed at least by the following steps: (a) modulating the signal received from each electrode in the corresponding electrode group according to a modulation pattern; (b) demodulating the signal received from each electrode in the corresponding electrode group or a value derived from the signal according to a demodulation mode, thereby determining a set of demodulated values ​​for the corresponding electrode group; wherein the modulation mode and the demodulation mode are selected so that steps (a) and (b) remove an average value from the signals received by the electrodes in each corresponding electrode group; and (c) restoring the average value to the signal received from each electrode in the corresponding electrode group or a value derived from the signal using the predetermined value of the reference electrode of the corresponding electrode group.

54. The method of claim 53, further wherein: the set of demodulated values ​​of the first electrode group comprises a demodulated value (K-M) of the reference electrode, wherein K=the true signal value of the reference electrode included in the first electrode group, and M=the average of the true signal values ​​of each electrode included in the group; and Step (c) is performed by adding an offset value to each demodulated value in the set of demodulated values, wherein the offset value is selected such that a sum of the offset value and the demodulated value of the reference electrode is equal to K.

55. The method according to any one of claims 53-54, wherein: each signal received from an electrode in the first electrode set, including a signal received from the reference electrode of the first electrode set, comprises a corresponding carrier component; Therein, the modulation pattern is selected so that the corresponding carrier components of the electrodes in the first electrode group sum to zero in any given time slot of the modulation pattern.

56. The method according to any one of claims 53-54, wherein: The system further comprises a carrier injection node comprising a carrier injection transmit electrode and a reference carrier electrode coupled to the reference electrode of the first electrode group, the method further comprising: A signal including a carrier component applied to the reference carrier electrode by the injection transmit electrode is received from the reference electrode of the first electrode set.

57. The method of claim 56, wherein: The carrier injection node is electrically isolated from the area of ​​the system that detects the user's finger or other element.

58. The method of claim 56, wherein: The carrier injection node is located within an analog front end configured to receive the signals from the plurality of electrode groups.

59. The method of claim 55 further comprising computationally determining and synthesizing a carrier component of the reference electrode.

60. The method of any one of claims 53-54, further comprising receiving a signal from the reference electrode of the first electrode group that includes noise received from a finger or other element of the user.

61. The method of claim 60, further comprising: selecting a reference electrode of the first electrode set from a plurality of available reference electrodes; Wherein, the step of selecting the reference electrode comprises: (a) measuring noise received from a finger or other element of the user via each of the plurality of available reference electrodes; and (b) Selecting the available electrode for which the measured noise received from the user's finger or other element is greatest.

62. The method according to any one of claims 53-54, wherein: The system for executing the method further comprises: a first transmit electrode set comprising one or more electrodes configured to apply a first carrier signal; a second transmit electrode set comprising one or more electrodes configured to apply a second carrier signal; wherein the reference electrode of the first electrode group intersects with the first emitting electrode set but does not intersect with the second emitting electrode set; and Wherein, the reference electrode of the second electrode group among the plurality of electrode groups intersects with the second transmitting electrode set but does not intersect with the first transmitting electrode set.

63. The method of claim 62, further comprising: receiving a signal from the first electrode set at a first time, during which the second transmitting electrode set applies the second carrier signal and the first transmitting electrode set does not apply the first carrier signal; and A signal is received from the second electrode group at a second time, during which the first set of transmitting electrodes applies the first carrier signal and the second set of transmitting electrodes does not apply the second carrier signal.

64. The method according to any one of claims 53-54, wherein: A common reference electrode is included in each of the plurality of electrode groups.

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