CN105027038B - Device, method and system for correcting tail effect - Google Patents
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Abstract
The technology for correcting tail effect is described herein.In the exemplary embodiment, device includes the sensor coupled with processing logic.The sensor is configured multiple measurement results of the measurement from sensor array, wherein, the measurement result represents electric conductor and contacted with the sensor array or close to the sensor array.The sensor array is included in interlaced with each other without the RX electrodes and TX electrodes of intersection in the individual layer on the substrate of the sensor array.Processing logic is configured the measurement result after the set for the adjusted value for determining to correspond to the tail effect associated with the measurement result, and the set generation adjustment based on the adjusted value, wherein, the parasitic signal change of the measurement result correction tail effect after the adjustment.
Description
Priority
The present application claims priority and benefit of U.S. provisional patent application No. 61/785,131 filed on 3, 14, 2013, which is incorporated herein by reference in its entirety; this application is a partial continuation of us patent application No. 13/800,468 filed on 13.3.2013, claiming priority and benefit of us provisional patent application No. 61/754,028 filed on 18.1.2013, both of which are incorporated herein by reference; this application is also a continuation-in-part application of united states patent application No. 13/405,071 filed on 24/2/2012, which claims priority and benefit of united states provisional patent application No. 61/559,590 filed on 14/11/2011 and priority and benefit of united states provisional patent application No. 61/446,178 filed on 24/2/2011, all of which are incorporated herein by reference.
Technical Field
The present disclosure relates generally to the field of touch sensor devices, and more particularly to processing of touch sensor data.
Background
Computing devices, such as notebook computers, personal digital assistants, mobile communication devices, portable entertainment devices (e.g., handheld video game devices, multimedia players, etc.), and set-top boxes (e.g., digital cable boxes, Digital Video Disk (DVD) players, etc.), may include user interface devices that facilitate interaction between a user and the computing device. One type of user interface device that has become common is a touch sensor device or a touch input device that operates by means of capacitive sensing. The touch sensor device may be implemented as a touch screen, touch sensor pad, touch sensor slider, or touch sensor button, and may include a touch sensor having an array of capacitive sensor elements. Capacitive sensing typically includes a scanning operation that periodically measures changes in capacitance associated with a capacitive sensor element to determine the presence, position, and/or motion of a conductive object (e.g., a stylus, a user's finger, etc.) relative to a touch sensor.
Touch sensors are expensive components of a touch sensor device or its user interface system. One reason for the high manufacturing cost of touch sensors is that conventional sensors use multiple layers of electrode material formed on a multi-layer substrate or a single layer substrate with a series of "jumpers" to form electrical connections between individual electrode segments and to isolate them from other electrodes that cross them. One way to reduce the high cost of touch sensors is to route trace portions (or segments) of the electrodes close together over the active area of a single layer substrate without the use of "jumpers". However, this type of sensor configuration results in increased capacitive cross-coupling between electrodes (e.g., particularly in response to conductive object touches), thereby causing false touches, inaccuracies, and poor touch response linearity, all of which limit the functionality of the touch sensor device and/or result in a poor user experience.
Disclosure of Invention
The present application includes at least the following embodiments:
1) an apparatus for correcting tail end effects, comprising:
a sensor array including a plurality of receive RX electrodes and a plurality of transmit TX electrodes, wherein the plurality of RX electrodes and the plurality of TX electrodes are interleaved with each other without crossing in a touch sensitive area in a single layer on a substrate of the sensor array;
a sensor configured to measure a plurality of measurements from the sensor array, wherein the plurality of measurements are representative of an electrical conductor being in contact with or proximate to the sensor array; and
processing logic coupled with the sensor, wherein the processing logic is configured to perform at least the following:
determining a set of adjustment values corresponding to tail end effects associated with the conductive body represented by the plurality of measurements, wherein the adjustment value for a particular TX electrode is calculated based on a sum of indices of RX electrodes along the particular TX electrode; and
generating an adjusted measurement corresponding to the electrical conductor represented by the plurality of measurements based on the set of adjustment values, wherein the adjusted measurement corrects for the tail end effect.
2) The apparatus of claim 1), wherein the tail effect comprises an increase in or decrease in parasitic signals caused by parasitic coupling between a main trace of an RX electrode and a TX electrode affected by the conductive body, wherein the main trace of the RX electrode is routed adjacent to the TX electrode.
3) The apparatus of claim 2), wherein the main trace of the RX electrode and the shape of the RX electrode are arranged in the touch sensitive area of the sensor array, but the shape of the RX electrode is not affected by the conductive body.
4) The apparatus of claim 1), wherein the sensor array comprises a first non-sensing region and a second non-sensing region on opposite sides of the sensor array, wherein a first subset of the plurality of RX electrodes and a first subset of the plurality of TX electrodes are routed from the first non-sensing region and a second subset of the plurality of RX electrodes and a second subset of the plurality of TX electrodes are routed from the second non-sensing region.
5) The apparatus of claim 1), wherein the processing logic is further configured to determine location coordinates of the conductive object on the sensor array based on the adjusted measurements.
6) The apparatus of claim 1), wherein the plurality of measurements comprise signal values of sensor elements formed by the particular TX electrode of the sensor array, and wherein the adjusted measurement comprises an adjustment value corresponding to the signal values.
7) The apparatus of claim 6), wherein, to determine the adjustment value for the particular TX electrode, the processing logic is configured to:
calculating a sum of the indices of RX electrodes forming the sensor element along the particular TX electrode;
calculating a sum of the signal values of the sensor elements along the particular TX electrode;
calculating a parameter value based on a sum of the indices and a sum of the signal values; and
based on at least: each of the signal values, the parameter value, and an index of a corresponding RX electrode are adjusted to obtain a corresponding adjusted value.
8) The apparatus of claim 6), wherein the signal value of the sensor element formed by the particular TX electrode is less than a tail effect threshold value.
9) The apparatus of claim 6), wherein the RX electrodes forming the sensor elements along the particular TX electrode have an index greater than an index of RX electrodes forming sensor elements having a peak signal value.
10) A method for correcting for tail-end effects, comprising:
receiving a plurality of measurements measured from a sensor array, wherein the plurality of measurements are representative of an electrical conductor being in contact with or proximate to the sensor array;
wherein the sensor array comprises a plurality of receive RX electrodes and a plurality of transmit TX electrodes, wherein the plurality of RX electrodes and the plurality of TX electrodes are interleaved with each other without crossing in a touch sensitive area in a single layer on a substrate of the sensor array;
the processing device determines a set of adjustment values corresponding to tail end effects associated with the conductive body represented by the plurality of measurements, wherein the adjustment value for a particular TX electrode is calculated based on a sum of indices of RX electrodes along the particular TX electrode; and
generating an adjusted measurement corresponding to the electrical conductor represented by the plurality of measurements based on the set of adjustment values, wherein the adjusted measurement corrects for the tail end effect.
11) The method of claim 10), wherein the tail effect comprises a parasitic signal increase or a parasitic signal decrease caused by parasitic coupling between a main trace of an RX electrode and a TX electrode affected by the conductive body, and wherein the main trace of the RX electrode is routed adjacent to the TX electrode.
12) The method of claim 11), wherein the main trace of the RX electrode and the shape of the RX electrode are disposed in the touch sensitive area of the sensor array, but the shape of the RX electrode is not affected by the conductive body.
13) The method of claim 10), further comprising determining differential signals for sensor elements of the sensor array based on the received plurality of measurements.
14) The method of claim 10), wherein:
the plurality of measurements comprises signal values of sensor elements formed by the particular TX electrode of the sensor array; and is
The processing device determining the adjusted measurement results comprises:
calculating a sum of the indices of RX electrodes forming the sensor element along the particular TX electrode;
calculating a sum of the signal values of the sensor elements along the particular TX electrode;
calculating a parameter value based on a sum of the indices and the sum of the signal values; and
based on at least: each of the signal values, the parameter value, and an index of a corresponding RX electrode are adjusted to obtain a corresponding adjusted value.
15) The method of claim 14), wherein the processing device determining the adjusted measurement further comprises:
selecting the signal value of the sensor element formed by the particular TX electrode of the sensor array by comparing the plurality of measurements to a tail effect threshold value.
16) The method of claim 14), wherein the processing device determining the adjusted measurement further comprises:
determining a first index of the RX electrodes forming the sensor element having the peak signal value; and
selecting the signal values for the sensor elements formed by the particular TX electrode of the sensor array by selecting only those signal values that are less than a tail effect threshold value and have an index greater than the first index.
17) The method of claim 10), further comprising determining location coordinates of the conductive object on the sensor array based on the adjusted measurements.
18) A system for correcting for tail end effects, comprising:
a capacitive sensor array comprising a plurality of receive RX electrodes and a plurality of transmit TX electrodes, wherein the plurality of RX electrodes and the plurality of TX electrodes are interleaved with each other without crossing in a touch sensitive area in a single layer on a substrate of the capacitive sensor array;
a capacitive sensor coupled with the capacitive sensor array, the capacitive sensor configured to measure a plurality of measurements from the plurality of RX electrodes, wherein the plurality of measurements are representative of an electrical conductor being in contact with or proximate to the capacitive sensor array; and
processing logic coupled with the capacitive sensor, wherein the processing logic is configured to perform at least the following:
determining a set of adjustment values corresponding to tail end effects associated with the conductive body represented by the plurality of measurements, wherein the adjustment value for a particular TX electrode is calculated based on a sum of indices of RX electrodes along the particular TX electrode; and
generating an adjusted measurement corresponding to the electrical conductor represented by the plurality of measurements based on the set of adjustment values, wherein the adjusted measurement corrects for the tail end effect.
19) The system of 18), wherein:
the tail effect comprises an increase in or decrease in parasitic signals caused by parasitic capacitive coupling between a main trace of an RX electrode and a TX electrode affected by the conductive body, wherein the main trace of the RX electrode is routed adjacent to the TX electrode; and is
The main trace of the RX electrode and the shaped portion of the RX electrode are disposed in the touch sensitive area of the capacitive sensor array, but the shaped portion of the RX electrode is not affected by the conductive body.
20) The system of claim 18), wherein the capacitive sensor array includes a first non-sensing area and a second non-sensing area on opposite sides of the capacitive sensor array, wherein a first subset of the plurality of RX electrodes and a first subset of the plurality of TX electrodes are routed from the first non-sensing area and a second subset of the plurality of RX electrodes and a second subset of the plurality of TX electrodes are routed from the second non-sensing area.
Drawings
FIG. 1 is a block diagram illustrating an embodiment of an example electronic system including a touch sensor assembly.
FIG. 2 is a block diagram illustrating an embodiment of an example sensor system that processes touch sensor data.
Fig. 3A illustrates a simplified plan view of a touch sensor device, according to an example embodiment.
Fig. 3B illustrates a cross-sectional view of the touch sensor device in fig. 3A.
FIG. 3C illustrates a portion of a touch sensor according to an example embodiment.
Fig. 4A, 4B, 4C, 4D, and 4E illustrate alternative patterns of sensor electrodes on a single layer substrate, in accordance with various embodiments.
Fig. 5 illustrates a parasitic signal coupled in a portion of a touch sensor panel having a single layer of a SLIM electrode pattern, according to an example embodiment.
Fig. 6 illustrates a dual wire touch sensor panel having a SLIM electrode pattern according to an example embodiment.
Fig. 7A and 7B illustrate two example data structures storing signal values reflecting tail end effects caused by electrical conductors on each side of a dual-wired touch sensor panel, according to example embodiments.
FIG. 8 is a graph illustrating an example of tail effect correction on a dual wired touch sensor panel according to an example embodiment.
FIG. 9 is a graph illustrating a comparison of tail effect and correction signals for the dual wire touch sensor panel shown in accordance with the example embodiment of FIG. 8.
FIG. 10A illustrates a data structure storing measured signal values reflecting tail end effects caused by electrical conductors on a dual-wired touch sensor panel, according to an example embodiment.
Fig. 10B illustrates a data structure storing signal values adjusted by correction with respect to the tail end effect illustrated in fig. 10A.
FIG. 11 illustrates a method for correcting tail-end effects, according to an example embodiment.
Fig. 12 illustrates an example method for adjusting signal values for tail end effects, according to some embodiments (e.g., such as the example embodiment illustrated in fig. 11).
FIG. 13 shows an example method of correcting tail effects according to certain embodiments illustrating contact by a large conductive body (such as a fat finger, for example).
Detailed Description
The following description sets forth numerous specific details, such as examples of specific systems, components, methods, and so forth, in order to provide a good understanding of various embodiments of the techniques described herein for correcting tail effects in single-layer touch sensors (e.g., such as touch sensors having a SLIM electrode pattern). It will be apparent, however, to one skilled in the art that at least some embodiments may be practiced without these specific details. In other instances, well-known components or methods are not described in detail or are presented in simple block diagram form in order to avoid unnecessarily obscuring the techniques described herein. Accordingly, the specific details set forth below are merely exemplary. The specific implementations may vary from these exemplary details and still be contemplated to be within the spirit and scope of the present invention.
Reference in the specification to "an embodiment", "one embodiment", "an example embodiment", "certain embodiments", and "various embodiments" means that a particular feature, structure, or characteristic described in connection with the embodiment included in at least one embodiment of the present invention is included. Moreover, the appearances of the phrases "an embodiment," "one embodiment," "an example embodiment," "certain embodiments," and "various embodiments" in various places in the specification are not necessarily all referring to the same embodiment.
This specification includes reference to the accompanying drawings, which form a part hereof. The figures illustrate illustrations according to exemplary embodiments. These embodiments (also may be referred to herein as "examples") are described in sufficient detail to enable those skilled in the art to practice the embodiments of the claimed subject matter described herein. Various embodiments may be combined, other embodiments may be utilized, or structural, logical, and electrical changes may be made without departing from the scope and spirit of the claimed subject matter. It should be appreciated that the embodiments described herein are not intended to limit the scope of the present subject matter, but rather to enable one skilled in the art to practice, make and/or use the present subject matter.
SUMMARY
Described herein are various embodiments of techniques for correcting tail effects in a touch sensor having transmit electrodes (TX) and receive electrodes (RX) arranged in the same layer (e.g., a single layer) of a substrate of the touch sensor. Unless specifically noted, a "touch sensor" is also referred to herein as a "sensor array," "touch panel," "touch sensor panel," or the like.
As used herein, "contact" refers to physical contact of a conductive object (e.g., a stylus, a user's finger, etc.) on a touch surface of a touch sensor, and/or to hovering of a touch surface in which the conductive object is sufficiently proximate to affect a sensor element of the touch sensor without physically contacting the sensor. As used herein, "sensor element" refers to a discrete unit or location area (e.g., adjacent) of an electrode where measurements or signals are available that are independent and different from measurements/signals obtained from other units or location areas in the touch sensor.
In single layer touch sensors that use interleaved electrodes without the use of "jumpers," the conductive bodies can affect portions (also referred to as "segments") of the multiple electrodes, causing changes in the capacitance of the electrodes that are not even directly under contact by the conductive bodies and should not mark or otherwise detect contact. Such parasitic signals outside the area of the coupled actual touch sensor that are affected by the contact cause an increase in or decrease in the parasitic signals (e.g., depending on the type of sensing mechanism used by the touch sensor). The increase or decrease of such parasitic signals in one or more sensor elements of the touch sensor is referred to herein as a "tail effect.
In one example embodiment, an apparatus includes a sensor coupled with processing logic. The sensor is configured to measure a plurality of measurements from the sensor array during a scanning operation, wherein the plurality of measurements are representative of the electrical conductor contacting or proximate to the sensor array. The sensor array includes a plurality of RX electrodes and a plurality of TX electrodes, wherein the plurality of RX electrodes and the plurality of TX electrodes are interleaved with each other in a single layer on a substrate of the sensor array without crossing. The processing logic is configured to determine a set of adjustment values corresponding to a tail-end effect associated with the plurality of measurements, and generate an adjusted measurement corresponding to the plurality of measurements based on the set of adjustment values, wherein the adjusted measurement corrects for a parasitic signal variation of the tail-end effect. In certain aspects of this embodiment, the tail-end effect comprises an increase in or decrease in parasitic signals caused by parasitic coupling between a main trace of the RX electrode and the TX electrode affected by the conductive body, wherein the main trace of the RX electrode is routed adjacent to the TX electrode. The main trace of the RX electrode and the shaped portion of the RX electrode are arranged in the touch sensitive area of the sensor array, however, the shaped portion of the RX electrode is not affected by the conductive body.
In another example embodiment, a method for correcting tail-end effects includes the steps of: receiving a plurality of measurements measured from a sensor array, wherein the plurality of measurements are indicative of an electrical conductor being in contact with or proximate to the sensor array, and wherein the sensor array comprises a plurality of RX electrodes and a plurality of TX electrodes interleaved with each other without crossing in a single layer on a substrate of the sensor array; the processing device determines a set of adjustment values corresponding to a tail end effect associated with the plurality of measurements; and generating an adjusted measurement corresponding to the plurality of measurements based on the set of adjustment values, wherein the adjusted measurement corrects for tail-end effect parasitic signal variations. In some aspects of this embodiment, the plurality of measurements includes signal values for the sensor elements formed by particular TX electrodes of the sensor array, and determining the adjusted measurement includes the steps of: calculating a sum of indices of RX electrodes forming the sensor element along the specific TX electrode; calculating a sum of signal values for the sensor elements along a particular TX electrode; calculating a parameter value based on the sum of the indices and the signal value sum; and adjusting each of the signal values based at least on the each signal value, the parameter value, and the index of the corresponding RX electrode to obtain a corresponding adjusted value.
In another example embodiment, a system includes a capacitive sensor array coupled with a capacitive sensor and processing logic coupled with the capacitive sensor. The capacitive sensor array includes a plurality of RX electrodes and a plurality of TX electrodes, wherein the plurality of RX electrodes and the plurality of TX electrodes are interleaved in a single layer on a substrate of the capacitive sensor array without crossing each other. The capacitive sensor is configured to measure a plurality of measurements from a plurality of RX electrodes, wherein the plurality of measurements represent a conductive object contacting or approaching the capacitive sensor array. The processing logic is configured to determine a set of adjustment values corresponding to a tail-end effect associated with the plurality of measurements, and generate an adjusted measurement corresponding to the plurality of measurements based on the set of adjustment values, wherein the adjusted measurement corrects for a parasitic signal variation of the tail-end effect.
Example operational context
FIG. 1 illustrates a block diagram of one example embodiment of an electronic system 100, the electronic system 100 including a processing device 110 that may be configured to measure capacitance of a touch sensitive surface and generate adjustments for compensating and/or eliminating tail-out effects. The electronic system 100 includes a touch-sensitive surface 116 (e.g., a touch screen, a touch pad, etc.) coupled to the processing device 110 and a host 150. In some embodiments, the touch-sensitive surface 116 is a user interface that detects touches on the surface 116 using the touch sensor array 121.
In the example embodiment of fig. 1, the touch sensor 121 includes sensor electrodes 121(1) -121(N) (where N is a positive integer) that are staggered on a single layer of a substrate without crossing each other (e.g., in a SLIM type). Touch sensor 121 is coupled to pins 113(1) -113(N) of processing device 110 via one or more analog buses 115 that convey a plurality of signals. For convenience of explanation, in this embodiment, each of the electrodes 121(1) - (121 (N)) is represented as a capacitor. The self-capacitance of each electrode in the touch sensor 121 is measured by the capacitive sensor 101 in the processing device 110. In some embodiments, depending on the type of touch sensor, the capacitive sensor may be configured to detect the mutual capacitance of the electrodes when a conductive object (e.g., a stylus, a user's finger, etc.) is contacting one or more of the electrodes.
The capacitive sensor 101 (also referred to merely as a "sensor") may include a relaxation oscillator or other device that converts capacitance into a measurement. The capacitive sensor 101 may also include a counter or timer that measures the oscillator output. Capacitive sensor 101 may also include a software component that converts a count value (e.g., a capacitance value) into a detection decision (also referred to as a switch detection decision) or relative magnitude. In some embodiments, the measurement obtained by capacitive sensor 101 may be a signal value representing one or more characteristics of the signal; in some embodiments, the signal value may additionally or instead be a value derived from the measured value based on a signal characteristic (e.g., such as voltage and/or current magnitude, primary capacitance, etc.). It is noted that there are various known methods of measuring capacitance, such as current-to-voltage phase shift measurement, resistor-capacitor charging timing, capacitive bridge dividers, charge transfer, successive approximation, sigma-delta modulators, charge accumulation circuits, field effect, mutual capacitance, frequency shift, or other capacitance measurement algorithms. It is noted that instead of evaluating raw counts against a threshold, the capacitive sensor may evaluate other measurements to determine user interaction. For example, in a capacitive sensor with a sigma-delta modulator, the capacitive sensor may evaluate the ratio of the pulse widths of the outputs to replace the raw counts above or below a certain threshold.
In the example embodiment of fig. 1, processing device 110 also includes processing logic 102. The operations of processing logic 102 may be implemented in firmware; alternatively, they may be implemented in hardware or software. Processing logic 102 is configured to perform operations that implement techniques for correcting tail-end effects as described herein. For example, processing logic 102 may receive measurements from capacitive sensor 101, adjust the measurements to compensate/eliminate tail effects, and then use the adjusted measurements to determine a state of touch sensor 121, such as whether an object (e.g., a finger, a stylus, etc.) is detected on or near the touch sensor (e.g., to determine the presence of an object), where an object is detected on the touch sensor (e.g., to determine the location of an object), track the motion of an object, or other information related to the detected object at the touch sensor.
In another embodiment, instead of performing operations of processing logic in a processing device (e.g., such as processing device 110), the processing device may send raw data or partially processed data to a host (e.g., such as host 150). As shown in fig. 1, host 150 may include decision logic 151 that performs some or all of the operations described above for processing logic 102. The operations of decision logic 151 may be implemented in firmware, hardware, software, or a combination thereof. The host 150 may include a high-level Application Programming Interface (API) in the application 152 that executes routines for receiving data, such as compensating for sensitivity differences, other compensation algorithms, reference update routines, startup and/or initialization routines, interpolation operations, scaling operations, and/or operations that implement techniques for correcting tail end effects as described herein. The operations described with respect to the processing logic 102 may be implemented in the decision logic 151, the application 152, or in other hardware, software, and/or firmware external to the processing device 110. In certain other embodiments, the processing device 110 may be a host 150.
In another embodiment, the processing device 110 may also include a non-inductive action block 103. This block 103 may be used to process data and/or receive data from/transmit data to host 150. For example, additional components may be implemented to operate the processing device 110 (e.g., a keyboard, keypad, mouse, trackball, LED, display, or other peripheral device) in conjunction with the touch sensor 121.
The processing devices 110 may reside on a common carrier substrate, such as, for example, an Integrated Circuit (IC) die substrate or a multi-chip module substrate. Alternatively, the components of the processing device 110 may be one or more separate integrated circuits and/or discrete components. In one embodiment, processing device 110 may be a programmable system on a chip fabricated on a single IC chip, such as, for example, the programmable system on a chip processing device (PSoC) developed by Cypress semiconductor corporation of san Jose, CalifTM). Alternatively, the processing device 110 may be one or more other processing devices known to one of ordinary skill in the art, such as a microprocessor or central processing unitA controller, special purpose processor, Digital Signal Processor (DSP), Application Specific Integrated Circuit (ASIC), Field Programmable Gate Array (FPGA), or other programmable device. In an alternative embodiment, for example, the processing device 110 may be a network processor having a plurality of processors including a core unit and a plurality of microengines. In addition, processing device 110 may include any combination of general purpose processing devices and special purpose processing devices.
In one embodiment, electronic system 100 is implemented as a user interface in a device that includes touch sensitive surface 116, such as a handheld electronic device, a portable and/or smart phone, a cellular telephone, a notebook computer, a Personal Data Assistant (PDA), a kiosk, a keyboard, a television, a remote control, a monitor, a palm-top multimedia device, a palm-top video player, a gaming device, a home or industrial appliance control panel, or other computer peripheral or input device. Alternatively, electronic system 100 may be used in other types of devices. It is noted that the components of electronic system 100 may include all of the components described above. Alternatively, electronic system 100 may include only some of the above-described components, or additional components not listed here.
FIG. 2 is a block diagram illustrating one embodiment of a capacitive touch sensor array 121 (also referred to as a "touch sensor") and a capacitive sensor 101 (also referred to simply as a "sensor") that convert measured capacitances to coordinates. Each coordinate is calculated based on the measured capacitance. In one embodiment, touch sensor 121 and capacitive sensor 101 are implemented in a system, such as electronic system 100. Touch sensor 121 includes a matrix 225 having N receive electrodes and M transmit electrodes. For example, matrix 225 includes transmit electrodes (TX)222 and receive electrodes (RX) 223. Each electrode in the matrix 225 is connected to the capacitive sensing circuit 201 through a demultiplexer 212 and a multiplexer 213.
Capacitive sensor 101 includes multiplexer controller 211, demultiplexer 212 and multiplexer 213, clock generator 214, signal generator 215, demodulation circuit 216, and analog-to-digital converter (ADC) 217. The ADC 217 is further coupled to a touch coordinate converter 218. The touch coordinate converter 218 outputs a signal to the processing logic 102.
The transmit electrodes and receive electrodes in matrix 225 may be arranged such that each transmit electrode is interleaved with a receive electrode on the same substrate layer (e.g., a single layer), but does not cross over a receive electrode while maintaining their electrical (e.g., galvanic) isolation. Thus, each transmit electrode may be capacitively coupled with each of the receive electrodes. For example, the transmit electrode 222 is capacitively coupled to the receive electrode 223 at the sensor element area 226 of the matrix 225, wherein the "E" shaped portions of the receive electrode 223 are interleaved with the "comb" shaped portions of the transmit electrode 222. In the electrode pattern shown in matrix 225, the "E" shaped portions at the same horizontal plane are electrically coupled to each other in the outer circle (bezel) portion (not shown) of touch sensor 121 to form a single (horizontal) receive electrode, while each transmit electrode is "comb" shaped and runs from top to bottom (vertical) of matrix 225.
In certain embodiments, a capacitive sensor (e.g., such as sensor 101 in fig. 1) may be configured to use a mutual capacitance sensing technique according to which the mutual capacitance present at the sensor element area of two electrodes may be measured by a processing device (e.g., such as processing device 120 in fig. 1). This change in mutual capacitance at the area of one or more sensor elements allows processing logic to determine the location of a contact on the touch sensor. A set of electrodes (such as column electrodes, for example) are designated as Transmit (TX) electrodes by mutual capacitance sensing. The transmit electrodes are driven by TX signals applied to the transmit electrodes through a transmit multiplexer. Another set of electrodes (such as row electrodes, for example) is designated as Transmit (TX) electrodes. The mutual capacitance of the sensor elements formed in the areas where the row and column electrodes cross each other can be measured by sampling the signal on each receive electrode. In some embodiments, a receive multiplexer may be used to sample the signal on one or more receive electrodes and provide a receive measurement signal back to processing logic 102 (and/or to another component of the processing device).
Referring back to fig. 2, clock generator 214 provides a clock signal to signal generator 215, and signal generator 215 generates a Transmit (TX) signal 224 that is supplied to the transmit electrodes of touch sensor 121. In one embodiment, signal generator 215 includes a set of switches that operate according to a clock signal from clock generator 214. The switch may generate the TX signal 224 by periodically connecting the output of the signal generator 215 to a first voltage and then to a second voltage, where the first and second voltages are different.
The output of signal generator 215 is connected to demultiplexer 212, which allows TX signal 224 to be applied to any of the M transmit electrodes of touch sensor 121. In one embodiment, multiplexer controller 211 controls demultiplexer 212 such that TX signal 224 is applied to each transmit electrode 222 in a controlled sequence. The demultiplexer 212 may also be used to ground, float, or connect the alternate signal to other transmit electrodes to which the TX signal 224 is not currently applied.
The TX signal 224 applied to each transmit electrode induces a current within each receive electrode because of the capacitive coupling between the transmit and receive electrodes. For example, when TX signal 224 is applied to transmit electrode 222 through demultiplexer 212, TX signal 224 is a Receive (RX) signal 227 on the receive electrodes of the sense matrix 225. The RX signal 227 on each receive electrode may then be measured sequentially using a multiplexer 213 that sequentially connects each of the N receive electrodes to a demodulation circuit 216.
The mutual capacitance associated with each sensor element (e.g., the area where a given TX electrode crosses a given RX electrode) may be sensed using demultiplexer 212 and multiplexer 213 by selecting each available combination of TX and RX electrodes. To improve performance, multiplexer 213 may also be segmented to allow more than one receive electrode in matrix 225 to be routed to further demodulation circuit 216. In an example in which the example with receive electrode demodulation circuit 216 has an optimized configuration corresponding to 1, multiplexer 213 may not be present in the system.
As an object (such as a finger) approaches the electrode matrix 225, the object causes a reduction in the mutual capacitance between only certain electrodes. For example, if a finger is placed in proximity to the sensor element area 226 (the area where the transmit electrodes 222 and receive electrodes 223 are interleaved), the presence of the finger will reduce the reduction in the mutual capacitance between the electrodes 222 and 223. Thus, the location of the finger on touch sensor 121 can be determined by identifying one or more receive electrodes having a reduced mutual capacitance and the time at which the reduced mutual capacitance on the one or more receive electrodes is measured by identifying the transmit electrode to which TX signal 224 is applied.
By determining the mutual capacitance associated with each sensor element formed by the transmit and receive electrodes in matrix 225, the location of one or more touch contacts may be determined. This determination may be continuous, parallel, or may occur more frequently at common electrodes.
In some embodiments, other methods for detecting the presence of a finger or conductive object may be used where the finger or conductive object causes an increase in capacitance at one or more electrodes, which may be arranged in a particular staggered pattern. For example, a finger placed in proximity to an electrode of a touch sensor may introduce additional capacitance to ground that increases the total capacitance between the electrode and ground. The location of the finger may be determined from the location of the one or more electrodes where the increased capacitance is detected.
The induced current signal 227 is rectified by the demodulation circuit 216. The rectified current output by the demodulation circuit 216 may then be filtered and converted to a digital code by the ADC 217.
The digital code may then be converted into touch position coordinates indicating the position of the input of the touch sensor 121 by the touch coordinate converter 218. The touch location coordinates are communicated to processing logic 102 as input signals. In one embodiment, the input signal is received at an input of processing logic 102. In one embodiment, the input may be configured to receive capacitance measurements indicative of a plurality of row coordinates and a plurality of column coordinates. Alternatively, the input may be configured to receive row coordinates and column coordinates.
In some embodiments, processing logic 102 may be configured to generate (or receive, e.g., from touch coordinate receiver 218) capacitance measurements (also referred to herein as "differential signal values") that represent differential signals. For example, processing logic 102 may be configured to determine the differential signal for a given sensor element as the difference between the stable (e.g., expected or fully charged) capacitance of the sensor element (e.g., when the conductive object is not in contact with the touch sensor and the touch sensor is not being scanned) and the capacitance of the sensor element measured as part of the scanning operation (e.g., when the conductive object may or may not be in contact with the touch sensor). The capacitance used for calculating the differential signal of the sensor elements may be the self-capacitance and/or the mutual capacitance of the sensor elements.
In various embodiments, processing logic may calculate a differential signal for each sensor element in the touch sensor based on capacitance measurements representing the self-capacitance and/or the mutual capacitance of the sensor elements. For example, the self-capacitance of a given sensor element may include a capacitance formed between the sensor element and a reference voltage (e.g., such as a ground voltage). The mutual capacitance of a given sensor element may comprise a capacitance formed between a transmit electrode and a receive electrode forming the sensor element and/or one or more electrically conductive bodies (e.g., such as a stylus tip or a user's finger) electrically isolated from the capacitive sensor element.
Single-layer touch sensor
Attempts have been made in the past to reduce the number of layers and, therefore, the manufacturing cost of touch sensors. In some embodiments, a single-layer touch sensor is suitable for single touch reception only. These touch sensitive sensors typically use a series of electrodes whose width varies linearly from one end of the electrode to the other. Coordinates along the electrode axis are determined using the signal variation along the length of the electrode. The coordinates in the direction perpendicular to the electrode axis are determined by conventional digitization methods. In other embodiments, single-layer multi-touch sensors use an array of pads that fill the sensor area, and each pad (or electrode) is sensed individually in a self-capacitance sensing mode. Such embodiments typically require a large number of measurement channels and pins on the controller chip and separate traces for each sensing pad to achieve acceptable accuracy for even very small sized sensors.
In some embodiments, a touch sensor device includes a touch sensor having a single layer active area. In addition, touch sensors are provided with wiring diagrams that minimize the number of conductors and the traces required to detect multiple contacts (such as "touches," for example) simultaneously. As a result, the overall manufacturing cost of the touch sensor and the overall manufacturing cost of the corresponding touch sensor device may be reduced.
Fig. 3A and 3B are simplified diagrams of a touch sensor device 301 (e.g., such as a capacitive sensing device) according to an example embodiment. In this embodiment, the touch sensor 301 is a "touch screen" device that includes a touch sensor having an active area 302 and a non-active area 303. As used herein, the "active area" and "touch sensitive area" of a touch sensor refer to the area in which the sensor is capable of generating a signal, causing a change in capacitance, or otherwise detecting one or more contacts. The "inactive area" and "non-sensing area" of the touch sensor refer to areas where contact is not detected or otherwise responded to. Touch sensor device 301 includes a Liquid Crystal Display (LCD) panel 304 disposed below a touch sensor 305, such as a sensor array or assembly, for example. As a general understanding, the active area 302 may correspond to the size and shape of a transparent (e.g., visible) area of the touch sensor 305, while the non-active area 303 may correspond to a non-transparent (e.g., non-visible) area of the touch sensor 305, which may be covered by a case (not shown) or other means of preventing contact effects. The touch sensor 305 includes a laminate (or protective layer) 306 attached to the side opposite the LCD panel by an adhesive 307. The touch sensor device 301 also includes a Flexible Printed Circuit (FPC) tail 308 extending therefrom that can be used to route electrical signals to and from the touch sensor 305.
Fig. 3C illustrates a portion of a touch sensor 310 (e.g., such as a capacitive sensor array) according to an example embodiment. The touch sensor 310 includes a substrate 312 having an active area (or center portion) 314 and an inactive area (or outer perimeter portion) 316 proximate to an edge of the substrate 312. The central portion 314 of the substrate 312 can correspond to an active (e.g., touch sensitive) area of a touch sensor device (e.g., such as the area 302 of the touch sensor device 301 in fig. 3A). The outer rim portion 316 of the substrate 312 can correspond to a non-active (e.g., non-sensing) region of the touch sensor device (e.g., such as region 303 of touch sensor device 301 in fig. 3A). In certain embodiments, the substrate 312 is made of an electrically insulating material with high light transmittance, such as glass, polyethylene terephthalate (PET), or a combination thereof.
An electrode array is formed on the central portion 314 of the substrate 312, the electrode array including a first set (or plurality) of electrodes 318 (also referred to as "first electrodes") and a second set (or plurality) of electrodes 320 (also referred to as "second electrodes"). The first electrode 318 and the second electrode 320 are both formed on the same layer (e.g., a single layer) of the substrate 312, but do not cross each other and, at the same time, remain electrically (e.g., galvanically) isolated from each other. In some embodiments, to form the first and second electrodes, a layer of transparent conductive material, such as Indium Tin Oxide (ITO) or a silver nanoparticle film, may be deposited on (or over) the substrate 312. As will be described in more detail later, during a scanning operation performed on the touch sensor 310, the first electrode 318 may be used as a Transmission (TX) electrode, and the second electrode 320 may be used as a Reception (RX) electrode. However, it should be understood that these TX and RX roles are merely exemplary and may be switched in various other embodiments.
The first electrode 318 is substantially "comb-tooth" shaped with the comb-tooth member facing the left as shown in fig. 3C. In the portion of the touch sensor 310 shown in fig. 3C, three first electrodes 318 (e.g., 318a, 318b, and 318C) and two second electrodes 320 (e.g., 320a and 320b) are included. The three first electrodes are substantially vertical and extend substantially along the entire length of the central portion 314 of the substrate 312. It should be understood that while other embodiments may use a different number of first electrodes extending in a direction other than perpendicular, in other embodiments, one subset of the first electrodes may extend only around the lower half of the length of the central portion while another subset of the first electrodes extends upward from the outer perimeter portion of the substrate bottom.
According to the techniques for correcting tail effects described herein, the second electrode includes one or more shaping portions, one or more primary traces, and at least one secondary trace, wherein the primary traces and shaping portions are routed in an active (touch sensitive) area of the touch sensor. As used herein, a main trace is also referred to as a "line" or "trace line". The "shaped" portion of the electrode has a width greater than the width of the main trace and a geometry other than substantially straight. The shaped portions are electrically connected to respective primary traces, and each primary trace is electrically coupled to a secondary trace in a non-active (non-sensing) region of the touch sensor. The main trace of a given second electrode is routed in the active area of the touch sensor along at least a portion of one or more other main traces of one or more other second electrodes formed further away from the inactive area of the given second electrode (e.g., the outer loop portion of the touch sensor). Further, the main trace of a given second electrode is routed in the active area along at least a portion of a given first electrode. The secondary trace that is electrically coupled to the primary trace of a given second electrode is routed in a non-active area of the touch sensor (e.g., such as an outer loop portion). Thus, the main trace for a given second electrode may be affected by conductor contact (which may have an effect on the change in the signal measured from the given second electrode during a scanning operation) because the main trace is routed in the active, touch-sensitive area of the touch sensor. On the other hand, secondary traces are typically affected by such contacts because the secondary traces are routed in inactive, non-sensing areas of the touch sensor and therefore do not contribute to the signal measured from the second electrode during the scanning operation.
By way of illustration, in fig. 3C, the first electrodes 318 are arranged in columns 322 and the second electrodes 320 are arranged in rows 324, wherein each column 322 comprises one of the first electrodes 318 and each row 324 comprises one of the second electrodes 320. Each of the second electrodes 320 includes a substantially "E" shaped portion extending rightward as viewed in fig. 3C. Each "E" shaped portion of a given second electrode 320 is interleaved (e.g., in an interdigitated pattern) with a corresponding one of the first electrodes 318. Within each row 324, the "E" portions of a given second electrode 320 are electrically coupled to one another, and each "E" portion is interleaved (e.g., interdigitated) with the "comb" shaped members of a corresponding first electrode 318. For example, the second electrode 320b includes three "E" shaped portions (e.g., 320b-1, 320b-2, 320b-3), each of which is electrically connected to a respective primary trace (e.g., corresponding 326a, 326b, 326c), wherein all of the respective primary traces are electrically coupled to one another over a secondary trace (e.g., 330b) in the outer loop portion 316. It is noted that the designated electrode pattern shown in fig. 3C is merely exemplary, and thus, other electrode shapes and interdigitated patterns (which may not be interdigitated) are possible and within the scope of the techniques described herein.
In fig. 3C, the main traces 326 coupled to the shaped portions of the second electrode 320 are routed substantially parallel and adjacent to each other. The main trace of a second electrode further away from the outer loop portion 316 is longer than the main trace of a second electrode closer to the outer loop portion and routed adjacent to more formed portions of other second electrodes.
The first electrode 318, the second electrode 320, and the main trace 326 may be made of Indium Tin Oxide (ITO) and formed in a substantially planar manner on the same substrate layer (e.g., a single layer). That is, although not specifically shown in fig. 3C, the first electrode 318, the second electrode 320, and the main trace 326 may have substantially the same thickness (e.g., 300 angstroms (a)) and may lay down (lay) in substantially the same plane.
As shown in fig. 3C, an insulating material (body or layer) 328 is formed on or otherwise attached to the outer ring (outer) portion 316 of the substrate 312. The insulating material 328 covers the ends of the main traces 326 that extend onto the outer loop portions 316, but it is noted that the insulating material 328 does not extend over the central portion 314 of the substrate 312. The insulating material 328 may be made of, for example, an epoxy or resin material and have a thickness of, for example, between 5 and 25 micrometers (μm) deposited on the substrate 312. In certain embodiments, the insulating material 328 may be a flexible substrate, such as a Flexible Printed Circuit (FPC), attached to the substrate 312. The insulating material 328 electrically isolates a given secondary trace 330 from at least some of the primary traces 326. For example, in fig. 3C, the insulating material 328 insulates the secondary trace 330b from the main traces 326 connected to the second electrodes 320a and those of the second electrodes 320 that are different from the electrodes 320 b.
A secondary trace (or plurality of conductors) 330 is formed on the insulating material 328 in the outer ring portion 316 of the substrate 312. In one embodiment, the secondary traces 330 are made of silver. Of interest to the embodiment of fig. 3C, a given secondary trace 330 is electrically connected to all of the primary traces 326 associated with a given second electrode 320 in a given (and only one) of the rows 324. Further, in the embodiment of fig. 3C, the isolated secondary trace 330 is electrically coupled to a corresponding one of the first electrodes 318. For example, secondary trace 330a is coupled to first electrode 318 c. In some embodiments, to reduce the routing area in the outer turn 316, the trace width in the outer turn area and the spacing of the secondary traces 330 may be minimized. For example, metal trace lines having a width of 10-50 μm and a pitch of 10-50 μm may be used in the outer perimeter regions.
It should be understood that touch sensor 310 may include another set of traces that are not shown in FIG. 3C. For example, another set of ground traces can be formed in the active area of touch sensor 310 and can be routed substantially parallel to first electrode 318. Such ground traces may be used to provide a ground so as to electrically isolate a given first electrode 318 from an immediately adjacent main trace 326 connected to a second electrode 320. Thus, each ground trace may be electrically connected to at least one of the secondary traces 330 coupled to system ground.
In operation, the secondary traces 330 are coupled to (e.g., in operative communication with) an electronic system (e.g., such as the system shown in fig. 2) in order to perform a scan operation on the touch sensor 310. In a scanning operation, the touch sensor 310 operates by providing a signal to each of the first electrodes 318 (referred to as "driving" TX electrodes) in turn while grounding the remaining first electrodes 318. Signals are induced in these second electrodes 320(RX electrodes) with shaped portions interleaved with the driving TX electrodes due to the capacitance coupled between them. The signals induced in the RX electrodes are measured and/or recorded by processing logic in the electronic system. The measured/recorded signal may change (from a predetermined reference value) due to the presence of a conductive object (e.g., such a finger or stylus) in contact with a portion of the touch sensor 310. The signal change measured on the RX electrodes (e.g., from a reference value) represents a change in capacitance (e.g., in "mutual capacitance") between one or more of the RX electrodes and the driving TX electrode. After measuring the signal on an RX electrode, the scanning operation is continued by providing a signal to the next TX electrode and measuring the corresponding RX electrode in the same way.
Fig. 4A-E illustrate alternative shapes, patterns, and arrangements of the first electrode 318 and the second electrode 320, in accordance with various embodiments of the technology described herein. For example, the embodiment shown in fig. 4A includes a first electrode 318 and a second electrode 320 that include a "spiral" structure as opposed to the "comb" and "E" shaped structures, respectively, previously discussed with respect to the first and second electrodes. However, it should be understood that other shapes, patterns, and arrangements may be used (as shown in the various alternative embodiments shown in fig. 4B, 4C, 4D, and 4E).
In some embodiments, different materials may be used to form the sensor (e.g., first and second) electrodes, such as copper, aluminum, silver, or any suitable conductive material that may be formed in an appropriate pattern. Also, an FPC may be used to form the sensor electrodes. In such embodiments, the various conductive layers in the FPC may be properly configured to form the first and second electrode arrays as described above and to form the main traces thereof. Thus, it should be understood that the electrodes, traces and insulating material (or body) may all be formed from a single, properly configured FPC. As will be appreciated by those skilled in the art, such embodiments are particularly applicable to non-transparent devices such as mouse pads, trackpads, touch pads, and the like. Additionally, in certain embodiments, the substrate may be made of other materials, such as any suitable plastic including vinyl, polyamide, which may be opaque depending on the particular device.
In some embodiments, the touch sensor may be formed by laying down sensor electrodes using alternative conductive materials (such as metal mesh). In such embodiments, the sensor electrodes are formed by arranging metal mesh electrodes on a PET substrate. In an alternative embodiment, the metal mesh sensor electrodes may be arranged on a glass substrate. In other embodiments, the sensor electrodes may be formed on the PET with silver nanowires or on the glass substrate with silver nanowires. In other embodiments, the touch sensor can be formed by bonding a glass (or other transparent insulating) mirror to another glass on which the sensor electrode pattern is disposed. In still other embodiments, the touch sensor may be formed by bonding glass (or other transparent insulating material) to a piece of PET containing the sensor pattern.
Thus, embodiments described herein provide a touch sensor device having a single layer structure in the active area (or portion) of the touch sensor of the device, while a multi-layer structure can be used in the outer (or other non-sensing) portion of the touch sensor for routing traces. Such multi-layer routing allows for reuse of traces such that the touch sensor uses a minimum number of traces and a minimum number of pins on the electronic system driving the touch sensor device, thereby reducing associated manufacturing costs.
Tail end effect
The tail effect in a single-layer touch sensor may be an increase or decrease in parasitic signals in one or more sensor elements in response to a conductive object (e.g., a stylus, a user's finger, etc.) contacting the touch sensor. In some embodiments, the tail effect for a given sensor element is caused by parasitic signals coupled between the TX electrode and the main trace of the RX electrode, whose shape is outside the actual contact area and therefore unaffected by the contact.
The techniques described herein for correcting tail-end effects provide for analysis of a signal profile from a particular segment of a touch sensor. The analysis uses linear approximation (e.g., based on measured/derived signal values of sensor elements below certain tail effect thresholds) to calculate an adjustment value that corrects for parasitic signal variations of tail effects, and subtracts the adjustment value from the measured/derived signal values to calculate the location coordinates of the touch before performing the location calculation.
FIG. 5 illustrates parasitic signals coupled in a portion of a touch sensor panel having a single layer electrode pattern in a touch sensitive area of the touch sensor. According to an example embodiment, portion 510 of the touch sensor includes ground traces 512 and 514, TX electrodes 516 and 518 (arranged in vertical columns), and RX electrodes 520, 522, 524, 526, 528, and 530 (arranged in horizontal rows). Ground traces 512 and 514 are disposed in the touch sensitive area of touch sensor portion 510 and run substantially parallel and in close proximity to the TX electrodes. Ground traces (e.g., such as ground trace 514) are used to provide ground so as to electrically isolate a given TX electrode (e.g., such as TX electrode 516) from adjacent/adjacent portions of an RX electrode (e.g., such as RX electrode portions 530a-2 and 530b-2, 528a-2 and 528b-2, 526a-2 and 526b-2, etc.). Each of TX electrodes 516 and 518 is arranged substantially vertically and comprises a substantially "comb" shaped member interleaved with the shaped portions of RX electrodes 520 and 530. Each of RX electrodes 520, 522, 524, 526, 528, and 530 is arranged in its row and, as shown, includes at least two substantially "E" shaped portions, each "E" shaped portion being electrically connected to its own corresponding main trace, each main trace being in turn electrically connected to the other main traces of the RX electrodes by a secondary trace (not shown) in the non-sensing (e.g., outer circle) region of the touch sensor.
Specifically, RX electrode 520 includes a shaped portion 520a-1 electrically connected to main trace 520b-1 and a shaped portion 520a-2 electrically connected to main trace 520 b-2. Likewise, RX electrode 522 includes a shaped portion 522a-1 electrically connected to main trace 522b-1 and a shaped portion 522a-2 electrically connected to main trace 522 b-2. The RX electrode 524 includes a shaped portion 524a-1 electrically connected to the main trace 524b-1 and a shaped portion 524a-2 electrically connected to the main trace 524 b-2. RX electrode 526 includes a shaped portion 526a-1 electrically connected to main trace 526b-1 and a shaped portion 526a-2 electrically connected to main trace 526 b-2. The RX electrode 528 includes a shaped portion 528a-1 that is electrically connected to the main trace 528b-1 and a shaped portion 528a-2 that is electrically connected to the main trace 528 b-2. Finally, RX electrode 530 includes a shaped portion 530a-1 electrically connected to main trace 530b-1 and a shaped portion 530a-2 electrically connected to main trace 530 b-2.
Fig. 5 shows an operation in which the contact 540 of the conductive body is affected by the touch sensor portion 510. As shown, contact 540 is primarily positioned over shaped portion 520a-1 of RX electrode 520 and thus a small amount over shaped portion 522a-1 of RX electrode 522; in addition, contact 540 is positioned partially over the shaped portion 520a-2 of RX electrode 520 and a small amount over the shaped portion 522a-2 of RX electrode 522. Contacts 540 are also positioned over and affect TX electrodes 516 and 518. However, as shown, contact 540 also capacitively affects main traces 524b-1, 526b-1, 528b-1, and 530b-1 (corresponding to RX electrodes 524, 526, 528, and 530, respectively) in parasitic coupling region 542 a. Likewise, contact 540 capacitively affects main traces 524b-2, 526b-2, 528b-2, and 530b-2 (corresponding to RX electrodes 524, 526, 528, and 530, respectively) in parasitic coupling region 542 b. Because of the parasitic coupling of contacts 540 in regions 542a and 542b, the signal values read from RX electrodes 524, 526, 528, and 530 during a scanning operation will register a signal change (from their respective references) even if the contacts are not positioned over the shapes of RX electrodes 524, 526, 528, and 530, and therefore, the shapes of these RX electrodes are not affected by the contacts. These signal variations represent tail effects caused by parasitic coupling in regions 542a and 542 b. Thus, if the signal values read from RX electrodes 524, 526, 528, and 530 are not corrected for signal variations caused by tail effects of parasitic coupling in regions 542a and 542b, the position location of contact 540 on the touch sensor may be computationally incorrect (e.g., as offset from its actual location).
As shown in fig. 5, there is additional parasitic coupling on the main trace of the RX electrode where the shaped part is not actually covered by the contact. However, these (not affected by contact) shaped portions are interleaved with the shaped portions of the corresponding TX electrodes to form sensor elements whereby different signal values are obtained. Thus, the tail-end effect causes more sensor elements to misregister a contact because the main traces connected to these sensor elements are directly affected by the contact (even if the sensor elements themselves are not in the contact area). Furthermore, since the same main trace is adjacent/abutting each TX electrode wire, the more TX electrodes that are covered by a contact, the higher the tail effect will be.
As shown in fig. 5, when RX electrodes are routed from the top to the bottom of the touch sensor, tail end effects are "seen" (or recorded) by the downstream RX electrodes. If the RX electrodes are routed from the bottom to the top of the touch sensor, the opposite tail end effect will be "seen". In some embodiments, to minimize the total width of the area occupied by the primary traces of the RX electrodes (e.g., such as the width of parasitic coupling regions 542a and 542 b), a touch sensor (e.g., such as a SLIM touch panel) may be dual wired, for example, from the top outer perimeter/non-sensing region and from the bottom outer perimeter/non-sensing region of the touch sensor. This means that (about) half of the RX electrodes will have their main traces routed from the top outer perimeter (e.g., extending downward), and the remaining RX electrodes have their main traces routed from the bottom outer perimeter (e.g., extending upward) of the touch sensor.
An example of a dual-wired, single-layer touch sensor is shown in FIG. 6. In the example embodiment of FIG. 6, touch sensor 610 includes a top outer (non-sensing) area 616, a top active (touch-sensing) area 614a, a bottom active (touch-sensing) area 614b, and a bottom outer (non-sensing) area 626. The RX electrodes in the top active area 614a are routed from the top outer perimeter area 616, while the RX electrodes in the bottom active area 614b are routed from the bottom outer perimeter area 626. In the embodiment shown in fig. 6, TX electrodes in both the top active area 614a and the bottom active area 614b are routed from the top outer perimeter area 616. In other embodiments, similar to the RX electrodes, the TX electrodes may also be split and dual wired from the opposite non-sensing region, e.g., if there is a need to lower the RC constant of the sensor element.
In the case of a dual wire touch sensor panel (such as the panel in FIG. 6), contact of the electrical conductors will cause independent tail effects on each side of the panel. For example, a contact placed in the top active area 614a of the touch sensor 610 will create a tail effect in the sensor element from the contact area down and towards the middle line 615 where the routing changes to the bottom outer loop routing. Likewise, a contact placed in the bottom active area 614b of the touch sensor 610 will create a tail end effect in the sensor element up from the contact area and toward the middle line 615.
Examples of independent tail effects on each side of a dual-routed, single-layer touch sensor panel are shown in FIGS. 7A and 7B. In particular, fig. 7A and 7B illustrate example data structures storing signal values reflecting tail end effects caused by conductive bodies on each side of a dual-wired touch sensor panel according to example embodiments.
Fig. 7A and 7B illustrate a data structure 700 that stores differential signal values derived from multiple measurements measured from sensor elements of a sensor array during a particular scan operation (shown in fig. 7A) and a different scan operation (shown in fig. 7B). The sensor array includes an active touch sensitive area (logically indicated by reference numeral 714), a top non-sensitive area (logically indicated by reference numeral 716), and a bottom non-sensitive area (logically indicated by reference numeral 726).
In fig. 7A and 7B, the sensor elements of the sensor array are logically represented as boxes (boxes) formed by 11 TX electrodes and 19 RX electrodes. Operating the sensor or processing logic (not shown) of the sensor array to store/associate an individual index value for each individual TX electrode, wherein the index values are arranged in a sequence representing the physical arrangement of TX electrodes in the sensor array; likewise, the sensor or processing logic also stores/associates an individual index value for each individual RX electrode, where the index values are arranged in a sequence that represents the physical arrangement of RX electrodes in the sensor array.
For example, in fig. 7A and 7B, TX index 702 is a sequence of integer values ranging from 0 to 10 representing 11 TX electrodes; likewise, RX index 704 is a sequence of integer values ranging from 0 to 18 representing 19 RX electrodes. In the embodiment shown in fig. 7A and 7B, RX electrodes with index values "0" to "9" are routed from the top non-sensing region (716) to form the top portion of the sensor array, while the remaining RX electrodes with index values "10" to "18" are routed from the bottom non-sensing region (726) to form the bottom portion of the sensor array.
Fig. 7A and 7B also show the differential signals obtained by the corresponding scanning operation for each sensor element represented in data structure 700. For example, in the scanning operation of fig. 7A, a differential signal 701a (having a value of "19") is measured or otherwise obtained for a sensor element formed by shaping portions of a TX electrode having a TX index of "9" and an RX electrode having an RX index of "16". In the scanning operation of fig. 7B, a differential signal 701B (having a value of "1") is measured or otherwise obtained for the same sensor element (i.e., the sensor element is formed by the shaped portions of the TX electrode having a TX index of "9" and the RX electrode having an RX index of "16"). It is noted that the techniques described herein for correcting tail-end effects are not limited to a particular number of electrodes, as various embodiments may use sensor arrays having different numbers of transmit and receive electrodes and different coding schemes for corresponding TX and RX indices. Thus, the sensor array and its TX index and RX index corresponding to the data structure 700 shown in fig. 7A and 7B are to be considered in an illustrative, rather than a limiting, sense.
In fig. 7A, the differential values for the sensor elements represented in data structure 700 are obtained by a scanning operation at a given point in time. The differential value indicates that the contact 706a is present on the touch surface in the bottom portion of the sensor array. The differential value also indicates that the tail effect 708a is also present only in the bottom portion of the array. It is noted that this differential value represents the state of the sensor elements of the sensor array at the time the scanning operation is performed-thus, the contact 706a shown in fig. 7A may be a static contact (e.g., such as a tap) or may be part of a more complex gesture (e.g., such as a scroll gesture).
In fig. 7B, the differential values for the sensor elements represented in data structure 700 are obtained by a scanning operation that is different from the scanning operation reflected in fig. 7A (e.g., at a different point in time). Referring to FIG. 7B, the differential value indicates that a contact 706B is present on the touch surface in the top portion of the sensor array. The differential value also indicates that the tail effect 708b is also present only in the top portion of the sensor array. The contact 706B shown in fig. 7B may be a static contact (e.g., such as a tap) or may be part of a more complex gesture (e.g., such as a scroll gesture).
It should be noted that various sensor designs are prone to the parasitic tail effects described above, except that the degree to which the tail effects are manifested may vary from design to design. Thus, in various embodiments, the techniques for correcting the tail end effect described herein may be implemented for sensor arrays constructed according to various different design techniques. Such designs and techniques include, but are not limited to, single solid diamond designs, MH3, and metal mesh.
Example of processing Tail end Effect data
Assuming that the RX index value increases in a direction away from the face of the touch sensor through which the RX electrodes are routed, the tail effect in a single-layer touch sensor is proportional to the RX index of the RX electrode under contact. For example, the farther from the shaped portion of the RX electrode that actually contacts, the more tail effect signals it gets from parasitic coupling. Referring to fig. 5 as an example, when compared to the other illustrated RX electrodes, although the shaped portions 530a-1 and 530a-2 are further away from the contact 540, the RX electrode 530 derives the most signal from parasitic coupling, at least because: (1) the main traces 530b-1 and 530b-2 run longer lengths along the TX electrodes 516 and 518, respectively; and (2) when conductor 540 is present, it reduces the signal from all four formations of the RX electrode, which is directly proportionately affected relative to the reference of the corresponding sensor element (520a-1, 520a-2, 522a-1, 522a-2), and thus the bottom RX electrode 530 still gets the most signal from parasitic coupling. In other words, RX electrode 520 receives the least signal increase due to parasitic coupling under contact 540 because this RX electrode has the shortest main trace.
According to the techniques described herein for correcting tail-end effects, a given scanning operation (also referred to as scanning a "frame" or "cycle") obtains measurements of all sensor elements in the sensor array (e.g., by powering TX electrodes and reading signals on RX electrodes). In some embodiments, obtaining the measurement results may include multiplexing several or all RX electrodes simultaneously; when obtained, the set of measurements from all RX electrodes represents measurements for a single scanning operation. Processing logic determines differential signal values from measurements obtained by the scanning operation-e.g. by comparing the obtained measurements with reference values stored for the corresponding sensor elements. Subsequently, assuming that all sensor elements having signal strengths below certain thresholds are caused by the tail-end effect, the techniques described herein provide parameters to construct/determine an approximation line based on the determined differential signal values, calculate an adjustment value for each affected sensor element corresponding to the tail-end effect using the determined parameters, and subtract each calculated adjustment value from the signal value of the corresponding sensor element, thereby correcting the tail-end effect.
It is noted that in a dual wire touch sensor design (which provides a touch sensor with two independent wire segments), independent approximate lines with their own independent parameters can be used when correcting for tail effects in each of the two independent wire segments. Such independent parameters would indicate approximate lines with different angles starting at the edge of each portion of the touch sensor and ending in the middle of the touch sensor. An example of such a double approximation line is shown in fig. 8.
FIG. 8 is a graph illustrating an example of tail effect correction for a particular middle TX electrode on a dual-wire touch sensor panel. In graph 800, signal 806 is detected by a particular scanning operation from a dual wired touch sensor and plotted along an X-axis representing RX index value 804 and a Y-axis representing differential signal value 802. The tail effect threshold 803 defines a differential signal level (around about "55") that is likely to be a tail effect. The techniques described herein are used to determine parameters (e.g., angles or slopes) of a best fit line 808a for the top of the touch sensor and a best fit line 808b for the bottom of the touch sensor. As shown in fig. 8, line 808a has a different slope than line 808b, and both lines extend from their respective edges of the touch sensor to the middle thereof (with an RX index value of "10" around the RX electrode). Reference numeral 807 indicates a differential signal from the RX electrode group that is affected by a tail end effect in the bottom of the touch sensor.
In some embodiments, the tail effect threshold may depend on the touch sensor's contact threshold setting or the absolute peak signal as a certain percentage of that threshold setting. In some embodiments, it is more meaningful to make the tail effect threshold dependent on the absolute peak signal, because the tail effect is proportional to the value of the absolute peak signal. For example, in one particular embodiment, the tail effect threshold is set as a percentage of the touch sensor's contact determination threshold. In this particular embodiment, the determined contact threshold is adaptive and depends on the maximum peak detected by the potential scanning operation, and the typical setting of the tail-end effect threshold is two-thirds of the adaptive contact threshold value (2/3).
More generally, if the touch sensor is intended to operate with a small object (such as a little finger or a stylus, for example), then it is preferable to use a dynamic/adaptive type of threshold because the difference in scan operation measurements (e.g., raw counts) from actual touches and from tail end effects is not that large. For example, a contact from a 4mm finger may generate a signal that is about the same magnitude as a signal from a tail end effect of a larger finger (e.g., a 20mm finger). Thus, it is useful to use a dynamic/adaptive contact determination threshold — an initial very low detection threshold may be set to detect contact by a smaller finger, and thereafter, based on the value of the maximum peak signal (e.g., raw count) of the actual measured contact, the contact determination threshold may be dynamically adjusted specifically for this contact. In this example, the tail-effect threshold may be set to less than 50% of the maximum peak signal actually detected. In this manner, the tail-effect threshold is "adaptive" to each contact detected.
In some embodiments, if the touch sensor is intended to operate with larger objects (e.g., such as a normal or fat finger), then it is preferable to use a fixed tail effect threshold because the difference between the magnitude of the actual touch and the magnitude of the tail effect signal is significant (due to parasitic coupling). For example, threshold 803 in fig. 8 represents a fixed threshold of about "55" that may be used to determine a tail-effect signal — for example, a differential signal value above "0" and below "55" may be considered a tail-effect signal.
According to the techniques described herein for correcting for tail-end effects, the differential signals of sensor elements that are below (fixed or adaptive) the tail-end effect threshold are used for linear approximation calculations of a given TX electrode by which these sensor elements are formed.
In certain embodiments, equation 1 below is used to determine a linear approximation (e.g., such as a best fit line) of the correlation between the differential signal due to the tail end effect and the index values of the RX electrodes forming the sensor elements corresponding to the differential signal:
Si=a*rxIndex+b (1)
wherein:
b is an intercept (or offset) parameter equal (or approximately equal) to "0" because there is no tail effect signal (or negligible) at the edge of the touch sensor by which the RX electrodes are routed (e.g., because the RX electrodes at that edge do not have a significant main trace length exposed to contact),
rxIndex is the RX index value for one (e.g., ith) RX electrode that forms one (e.g., ith) individual sensor element along a given TX electrode,
a is a constant slope (or angle) parameter value that defines the skew rate (slope) of the near-best-fit line for a given TX electrode (note that if a dual-wired touch sensor design is used, the slope parameter value is unique for each TX electrode and for each portion of the touch sensor from which the RX electrodes are wired), and
Sian adjustment value for an (e.g., ith) individual sensor element is represented, where this adjustment value corresponds to the tail effect signal at the ith sensor element (as determined based on the approximate best fit line) and should be subtracted from the differential signal for that sensor element to correct for the tail effect.
In some embodiments, the slope parameter value (or coefficient) a may be determined by using equation 2 below:
wherein,
siis the differential signal value obtained along a given TX electrode from one (e.g., ith) individual sensor element formed by one (e.g., ith) RX electrode,
i is its differential signal value siThe RX index value (along a given TX electrode) of one (e.g., the ith) individual sensor element that is greater than "0" and less than the tail effect threshold being used,
n is the number of sensor elements along a given TX electrode having a differential signal value greater than "0" and less than the tail effect threshold,
is the sum of the differential signal values for sensor elements along a given TX electrode having a differential signal value greater than "0" and less than the tail effect threshold, and
Σ i is the sum of the RX index values of sensor elements along a given TX electrode that have differential signal values greater than "0" and less than the tail-effect threshold. Thus, according to equation 2, only the sensor elements having differential signals with values between "0" and "threshold" are used to determine the parameters of the approximate best fit line, the remaining sensor elements and their RX index values are skipped from calculation.
An example of an approximate best fit line for a two-wire touch sensor is shown in fig. 8 (e.g., such as best fit line 808 b). As shown in fig. 8, only the sensor elements corresponding to the differential signal values indicated by reference numeral 807 are used to determine the parameters of the best fit line 808 b.
In certain embodiments, after the slope parameter (or coefficient) a for a given TX electrode is determined (e.g., according to equation 2 above), the adjustment value S for the corresponding (e.g., ith) sensor elementiIs calculated (e.g., according to equation 1 above). The tail-end effect is then determined by the differential signal value s obtained from the corresponding (e.g., ith) sensor element using equation (3) belowiMinus the adjustment value SiTo correct for:
DiffrxIndex=srxIndex-a*rxIndex (3)
(which is equal to s)i-correction=si-Si)
Wherein,
a × rxIndex (e.g., S)i) Is an adjustment value corresponding to the tail effect of the sensor element (e.g., the ith sensor element) formed along a given TX electrode and an RX electrode having an RX index value of "rxIndex",
srxIndex(e.g., s)i) Is the value of the differential signal originally obtained for the sensor element formed along the given TX electrode and the RX electrode having an RX index value of "rxIndex" (e.g., the ith sensor element), an
DiffrxIndex(e.g., s)i-correction) Is the tail effect corrected differential signal value for a sensor element (e.g., the ith sensor element) formed along a given TX electrode and an RX electrode having an RX index value of "rxIndex".
In the example shown in FIG. 8, the left side (e.g., top) of the touch sensor receives little signal from the contact, and therefore, the tail effect correction for that side is minimal. On the right side (e.g., bottom) of the touch sensor, a tail effect from the contact is observed, and the signal from the tail effect needs to be subtracted based on the parameters of the best fit line 808b according to the techniques described herein. The resulting signals (as corrected for tail-end effects) are plotted on fig. 9.
FIG. 9 is a graph illustrating a comparison of a tail effect signal and a correction signal on the dual wire touch sensor panel of FIG. 8. In graph 900, a raw signal 906 (e.g., as detected by a particular scanning operation from a dual wired touch sensor) and a correction signal 916 are plotted along an X-axis representing an RX index value 804 and a Y-axis representing a differential signal value 802. As shown in fig. 9, the tail effect signal 907 is removed from the original signal 906 and no tail is revealed in the corrected signal 916. Sometimes, in some embodiments, the tail-effect correction may produce a negative signal value for the sensor element in which the tail-effect is detected; however, this is not important for position (e.g., position coordinates) calculation, as the position calculation algorithm in these embodiments excludes all negative differential signal values.
In some embodiments, the tail-effect correction is only applied to perform the position calculation of the detected contact, and the tail-effect correction should not be restored after the position calculation is completed. This is necessary in order to maintain a correct reference value for the sensor elements in the touch sensor with respect to the actual measurement signal from a given scanning operation and to ensure that the input data for the scanning operation will have the same visible tail effect.
In some embodiments, recovering tail effect correction may be performed by using equation 4 below:
DiffrxIndex=srxIndex+a*rxIndex (4)
(which is equal to s)i=si-correction+Si)
Wherein,
a × rxIndex (e.g., S)i) Is an adjustment value corresponding to the tail effect of the sensor element (e.g., the ith sensor element) formed along a given TX electrode and an RX electrode having an RX index value of "rxIndex",
srxIndex(e.g., s)i-correction) Is a currently stored tail effect corrected differential signal value for a sensor element (e.g., the ith sensor element) formed along a given TX electrode and an RX electrode having an RX index value of "rxIndex". an
DiffrxIndex(e.g., s)i) Is the recovered (e.g., raw) differential signal value for a sensor element (e.g., the ith sensor element) formed along a given TX electrode and an RX electrode having an RX index value of "rxIndex".
This recovery of tail effect correction is applied separately to each TX electrode and each portion of the touch sensor through which the RX electrode is routed (e.g., if a dual-routed touch sensor design is used).
Examples of trailing effect correction data are shown in fig. 10A and 10B, which data were obtained experimentally from certain embodiments. In particular, FIG. 10A shows a data structure 1000 that stores differential signal values that reflect tail end effects caused by electrical conductors on a dual-wired touch sensor. Fig. 10B shows the same data structure 1000 storing signal values adjusted for correction of tail-end effects. In fig. 10A and 10B, the sensor elements of the touch sensor are logically represented as boxes formed by 11 TX electrodes and 19 RX electrodes, where TX index 1002 is a sequence of integer values ranging from 0 to 10 for 11 TX electrodes, and RX index 1004 is a sequence of integer values ranging from 0 to 18 for 19 RX electrodes. In the embodiment shown in fig. 10A and 10B, RX electrodes having index values "0" to "9" are routed from the top non-sensing area to form the top portion of the touch sensor, and the remaining RX electrodes having index values "10" to "18" are routed from the bottom non-sensing area to form the bottom portion of the touch sensor.
In fig. 10A, differential signal values for sensor elements represented in data structure 1000 are obtained by a scanning operation at a given point in time. The differential signal value indicates that a contact is present in the contact area 1006a in the bottom portion of the touch sensor. The differential signal value also indicates that a tail effect is present in the tail effect region 1008. In fig. 10B, the differential values for the sensor elements represented in the data structure 1000 have been corrected for tail-end effects 1008 according to the techniques described herein. For example, adjustment values corresponding to the tail effect have been calculated for sensor elements in the touch sensor, and these adjustment values have been subtracted from corresponding differential signal values stored in data structure 1000. Thus, in FIG. 10B, data structure 1000 stores corrected differential signal values for each sensor element in contact region 1006B and corrected tail region 1018. Thus, fig. 10A shows an initial signal plot in which tail-end effects are present, while fig. 10B shows a corrected signal plot in which tail-end effects are eliminated in accordance with the techniques described herein. After applying the tail-effect correction, the position of the object in contact with the touch sensor is to the right of the middle of the contact area 1006B as shown in fig. 10B.
In embodiments using a dual wire touch sensor, the RX index value (e.g., such as the "rxIndex" value used in equations 1, 3, and 4 above) should always be "0" at the end of the touch sensor (even if this RX index value corresponds to the last RX electrode in the sequence), and the RX electrode (or sensor element) closest to the middle of the touch sensor should have an RX index value equal to the incremental number of this RX electrode from the edge of the touch sensor. In other words, for the purpose of tail-end effect correction calculation, the index of the RX electrode should start from "0" and increase from the side of the touch sensor through which the RX electrode is wired. Thus, in the case of a dual wire touch panel, remapping of the RX index values of the RX electrodes may be required for the purposes of tail effect correction calculations described herein (e.g., as equations 1, 3, and 4 above). For example, with respect to fig. 10A, RX index values "10" to "18" (for the bottom nine RX electrodes) should be mapped again to values of "9" to "0", respectively, before tail-end effect correction is calculated. This is one and only way that the techniques described herein can preserve the correlation that exists between the tail effect and the RX index value in a single-layer touch sensor-that is, the tail effect increases in proportion to the increase in the RX index value of the RX electrode under contact.
Example of method for correcting Tail end Effect
FIG. 11 illustrates an example method for correcting for tail-end effects. The method steps in fig. 11 are described hereinafter as being performed by processing logic (e.g., such as processing logic 102 in fig. 1). It is noted, however, that various implementations and embodiments may use a variety and possibly multiple components to perform the operations of the method of fig. 11. For example, in various embodiments, processing logic may be implemented in various ways, including but not limited to: as a set of stored software and/or firmware instructions that, when executed by one or more processors, are operable to perform one or more operations; one or more software components executable as one or more computing devices (e.g., software modules, libraries of functions, compiled and/or interpreted object-oriented classes, dynamically linked libraries, etc.); and as any combination of one or more software components and one or more hardware components (e.g., processors, microcontrollers, Application Specific Integrated Circuits (ASICs), etc.). In another example, the processing logic in various embodiments may be implemented in a single integrated component or its functionality may be distributed in two or more components that may perform certain additional operations and functions. Thus, the description of the method in FIG. 11 as performed by the processing logic is to be taken in an illustrative rather than a restrictive sense, as follows.
At blocks 1100 through 1170, processing logic performs a scan operation. At block 1100, as part of a scanning operation, processing logic receives a plurality of measurements measured from a sensor array. The measurement is affected by contact of the conductive body on a touch surface of the sensor array (e.g., such as a pen tip or a user's finger). In some embodiments, the measurements received by the processing logic may include differential signal values for all (or a portion) of the sensor elements in the sensor array; in other embodiments, processing logic may receive raw measurements (e.g., raw signal counts) from the sensor elements and may calculate corresponding differential signal values.
After receiving and/or calculating the differential signal values corresponding to the received measurements, processing logic performs an operation in block 1102 of initializing a variable ("txIndex") to zero, which represents the TX index value for the current TX electrode for which the calculation is being performed.
In block 1104, processing logic determines whether there are any remaining TX electrodes that need to be processed. For example, processing logic performs a comparison operation in which the value stored in the "txIndex" variable is compared to a variable or constant ("txLast") that represents the sum of TX electrodes that need to be processed as part of a scanning operation (e.g., such as the sum of TX electrodes in a sensor array). If the "txIndex" variable is less than the "txLast" variable, then at least the current TX electrode still needs to be processed and the processing logic continues to perform the operations in blocks 1112 through 1128. If the "txIndex" variable is not less than the "txLast" variable, then the differential signal values for the sensor elements of all TX electrodes have been processed and the processing logic continues to perform the operations in block 1130.
Block 1110 includes blocks 1112-1126, which include processing logic performing operations to calculate (e.g., according to equation 2 above) a slope parameter value a that approximates a best fit line for the tail effect signal (indicated by the "txIndex" variable) of the current TX electrode. If the sensor array is dual wired, then processing logic performs the operations in block 1110 (e.g., the operations in blocks 1112-1126) twice — i.e., once for each portion of the sensor array over which the RX electrodes are wired. It is noted that when performing these operations for the bottom portion of the sensor array, the RX index values of the RX electrodes wired from this portion may need to be mapped again as described above (e.g., to preserve the correlation that exists between the tail end effect and the RX index values).
In block 1112, processing logic performs an operation to initialize a variable ("rxIndex") to zero, which represents the RX index value for the current RX electrode (along the current TX electrode) for which the calculation is being performed.
In block 1114, processing logic performs an operation of initializing a variable ("snsSum") to zero, which represents the sum of RX index values of the sensor elements (formed along the current TX electrode) included in calculating the slope parameter (or coefficient) value a for the current TX electrode.
In block 1116, processing logic determines whether there are any remaining RX electrodes that need to be processed for the current TX electrode. For example, processing logic performs a comparison operation in which the value stored in the "rxIndex" variable is compared to a variable or constant ("txLast") that represents the total number of RX electrodes that need to be processed for the current TX electrode. If the "rxIndex" variable is less than the "rxLast" variable, then at least the current RX electrode still needs to be processed, and the processing logic continues to perform the operations in blocks 1118 through 1124. If the "rxIndex" variable is not less than the "rxLast" variable, then the differential signal values from all RX electrodes along the current TX electrode have been processed and processing logic continues to perform operations in block 1126 (which calculates the slope parameter value a for the current TX electrode).
In block 1118, processing logic determines whether the differential signal value for the current RX electrode is included in the calculation of the slope parameter value a for the current TX electrode. For example, if the differential signal value for the current RX electrode is greater than "0" and less than the tail-effect threshold, then processing logic includes this differential signal value in the calculation. Note that this differential signal value is actually the differential signal value of the "current" sensor element formed by the current RX electrode (as indicated by the variable "rxIndex") and the current TX electrode (as indicated by the variable "txIndex"). To make this determination, processing logic may perform the following operation (which is a boolean operation of the compare operation operands):
signal >0 and signal < threshold
Where "signal" is a variable that stores the differential signal value of the current sensor element and "threshold" is a variable that stores the (fixed or adaptive) tail effect threshold that is being used for the scanning operation being processed. If the "signal" variable is a variable between "0" and "threshold", then the current sensor element needs to be included in the calculation of the slope parameter value a for the current TX electrode, and processing logic continues to perform operations in blocks 1120 and 1122. If the "signal" variable is not a variable between "0" and "threshold", then the current sensor element needs to be skipped/excluded from the calculation and processing logic continues to perform the operations in block 1124.
In block 1120, processing logic determines a sum of the differential signal values of the sensor elements that are included in the calculation of the slope parameter value a for the current TX electrode. For example, processing logic adds the differential signal value of the current sensor element (formed by the current RX electrode indicated by the "rxIndex" variable and the current TX electrode indicated by the "txIndex" variable) to the current accumulated sum of differential signal values for the current TX electrode processed so far. To perform the addition, processing logic may perform the following operations
Total [ txIndex ] ═ total [ txIndex ] + signal
Where "sum [ txIndex ]" is a variable that stores the cumulative sum of differential signal values for the current TX electrode (e.g., the differential signal values of the sensor elements formed by the RX electrode for the current TX electrode that has been processed so far), and "signal" is a variable that stores the differential signal values of the current sensor element that is being processed.
In block 1122, processing logic determines the sum of the RX index values of the sensor elements included in the calculation (e.g., according to equation 2 above) for the current TX electrode. For example, processing logic adds the RX index value to a current accumulated sum of RX index values included in calculating slope parameter value a for the current TX electrode for sensor elements formed along the current TX electrode. To perform the addition, processing logic may perform the following operations
snsNum=snsNum+rxIndex
This operation adds the "rxIndex" variable to the "snsNum" variable, effectively adding the RX index value for the current electrode to the cumulative sum of the RX index values of the sensor elements that have been processed so far for the current TX electrode.
In block 1124, the processing logic sets the RX index value for the next RX electrode that needs to be processed and proceeds to perform the operations in block 1116. For example, processing logic performs operations
rxIndex++
This operation adds a "1" to the "rxIndex" variable to indicate that the next RX electrode now becomes the current RX electrode for processing; thereafter, processing logic continues with operations in block 1116.
After the differential signal values from all RX electrodes along the current TX electrode have been processed, processing logic determines in block 1116 that the current "rxIndex" variable is not less than the "rxLast" variable. Thus, processing logic continues with the operation in block 1126.
In block 1126, processing logic calculates a slope parameter value a for the current TX electrode and stores this parameter value associated with the current TX electrode. For example, processing logic performs operations
Coef [ txIndex ] ═ total [ txIndex ]/snsNum
Where "Coef [ txIndex ]" is a variable storing the slope parameter value a for the current TX electrode, "sum [ txIndex ]" is a variable storing the sum of the differential signal values of the sensor elements along the current TX electrode for correcting the tail effect, and "snsnsnsnsNum" is a variable storing the sum of the RX index values of the sensor elements for the current TX electrode for correcting the tail effect.
In block 1128, processing logic sets the TX index value for the next TX electrode that needs to be processed and continues with the operations in block 1104. For example, processing logic performs operations
txIndex++
This operation adds a "1" to the "txIndex" variable to indicate that the next TX electrode now becomes the current TX electrode for processing; thereafter, processing logic continues with operations in block 1104.
After the differential signal values for all TX electrodes have been processed, processing logic determines in block 1104 that the current "txIndex" variable is not less than the "txLast" variable. Thus, processing logic continues with the operation in block 1130.
In block 1130, processing logic determines adjustment values corresponding to the tail end effects of the sensor elements on each TX electrode and then corrects the differential signal values of the sensor elements on each TX electrode by subtracting their respective adjustment values from each such differential signal value. Two example methods for adjusting the differential signal values for the sensor element tail end effect are described below with respect to fig. 12 and 13.
In block 1150, processing logic performs a local/maximum search using the tail-end effect corrected signal values and calculates a location of the electrical conductor on the sensor array. For example, in some embodiments, processing logic may search a data structure storing trailing-effect corrected signal values for a single local maximum outside a particular local maximum threshold, where the single local maximum is a signal value in the data structure that is greater than the signal values surrounding it. Processing logic may compare each signal value to each of its neighbors and may determine that a given signal value is a local maximum when its neighbors have no higher values. Thereafter, processing logic uses (e.g., in a centroid location algorithm) information about the local maxima found in order to calculate a contact location (e.g., such as touch coordinates and/or a location centroid) of the conductive object on the sensor array.
In some embodiments, tail-end effect correction may only be required at the stage of calculating the location of the conductive body on the sensor array. Thus, after completing the position calculations in these embodiments, processing logic may perform the operations in block 1160 to recover the tail-end effect correction for each TX electrode. For example, in these embodiments, processing logic may perform the calculations described in equation 4 above to recover the original differential signal values received/obtained as part of the scan operation in block 1100 in the corresponding data structure. Such tail-effect recovery will ensure that any subsequent downstream processing based on the data stored in the data structure is performed correctly.
In certain embodiments, processing logic may (optionally) update stored baseline values for each sensor element of the sensor array in block 1170. Typically, such reference values are stored in firmware and maintained periodically in order to ensure accurate operation of the sensor array. For example, since conditions (e.g., temperature, humidity, etc.) under which the device operates may change, at least some scanning operations may be configured to periodically calculate a correction and apply the correction to a stored baseline value.
After recovering the tail-effect correction and/or updating the baseline value, processing logic returns to block 1100 and continues processing the next scan operation.
FIG. 12 illustrates an example method of adjusting signal values for tail end effects according to some embodiments. For example, the method of FIG. 12 may be performed as part of the operations in block 1130 of FIG. 11, as described above. The method steps in fig. 12 are described hereinafter as being performed by processing logic (e.g., such as processing logic 102 in fig. 1). It is noted, however, that various implementations and embodiments may use various and possibly multiple components to perform the operations of the method of fig. 12. For example, in various embodiments, processing logic may be implemented in various ways, including but not limited to: as a set of stored software and/or firmware instructions operable to perform one or more operations when executed by one or more processors; one or more software components executable as one or more computing devices; as any combination of one or more software components and one or more hardware components; as a single integrated component or as two or more components that may perform additional operations. Thus, the description of the method in FIG. 12 as performed by the processing logic is to be taken in an illustrative rather than a restrictive sense, as follows.
At block 1204, slope parameter (or coefficient) values a for the TX electrodes of the sensor array have been calculated and stored in association with their corresponding TX electrodes. For example, as part of any given scanning operation, processing logic may maintain (in memory or on firmware storage) an array storing parameter values calculated (e.g., according to blocks 1102 and 1128 in fig. 11) for TX electrodes of the sensor array.
Referring to fig. 12, in block 1132, processing logic performs an operation to initialize a variable ("txIndex") to zero, which represents the TX index value for the current TX electrode for which the calculation is being performed.
In block 1134, processing logic determines whether there are any remaining TX electrodes that need to be processed. For example, processing logic performs a comparison operation in which the value stored in the "txIndex" variable is compared to a variable or constant ("txLast") that represents the total number of TX electrodes that need to be processed for tail effect adjustment (e.g., such as the total number of TX electrodes in a sensor array). If the "txIndex" variable is less than the "txLast" variable, then at least the current TX electrode still needs to be processed and the processing logic continues to perform the operations in blocks 1136A through 1144. If the "txIndex" variable is not less than the "txLast" variable, then the differential signal values for the sensor elements for all TX electrodes have been processed and the processing logic continues with operation in block 1250.
In block 1136A, processing logic performs an operation to initialize a variable ("rxIndex") to zero, which represents the RX index value for the current RX electrode (along the current TX electrode) for which the calculation is being performed.
In block 1138, processing logic determines whether there are any remaining RX electrodes that need to be processed for the current TX electrode. For example, processing logic performs a comparison operation in which the value stored in the "rxIndex" variable is compared to a variable or constant ("txLast") that represents the total number of RX electrodes that need to be processed for the current TX electrode. If the "rxIndex" variable is less than the "rxLast" variable, then at least the current RX electrode still needs to be processed and the processing logic continues to perform operations in blocks 1140 and 1142. If the "rxIndex" variable is not less than the "rxLast" variable, then the differential signal values from the RX electrode along the current TX electrode have been processed and processing logic continues to perform operations in block 1144 (which sets the next TX electrode for processing).
In block 1140, processing logic adjusts the differential signal values for the tail effect for the current sensor element (which is formed by the current RX electrode indicated by the "rxIndex" variable and the current TX electrode indicated by the "txIndex" variable). For example, processing logic performs the following operations
SignalCorrection ofsignal-Coef [ txIndex ═]*rxIndex
Wherein, the signalCorrection of"is a variable that stores the differential signal value of the current sensor element as adjusted for tail end effects," signal "is a variable that stores the measured/obtained differential signal value of the current sensor element being processed, and" Coef txIndex]"is a variable that has been calculated and stored for the slope parameter value a of the current TX electrode. Note that the value (i.e., product) "Coef [ txIndex]rxIndex "represents an adjustment value to correct for tail effects of the current sensor element.
In block 1142, processing logic sets the RX index value for the next RX electrode that needs to be processed and continues operation in block 1138. For example, processing logic performs operations
rxIndex++
This operation adds a "1" to the "rxIndex" variable to indicate that the next RX electrode now becomes the current RX electrode for processing; thereafter, processing logic continues with operations in block 1138.
After the differential signal values from all RX electrodes along the current TX electrode have been processed, processing logic determines in block 1138 that the current "rxIndex" variable is not less than the "rxLast" variable. Thus, processing logic continues with the operation in block 1144.
In block 1144, processing logic sets the TX index value for the next TX electrode that needs to be processed and continues operation in block 1134. For example, processing logic performs operations
txIndex++
This operation adds a "1" to the "txIndex" variable to indicate that the next TX electrode now becomes the current TX electrode for processing; thereafter, processing logic continues with operations in block 1134.
After the differential signal values of the sensor elements of all TX electrodes are adjusted in the manner described above, processing logic determines in block 1134 that the current "txIndex" variable is not less than the "txLast" variable. Thus, processing logic continues with operations in block 1250.
In block 1250, processing logic performs the operations described in block 1150 of FIG. 11 (e.g., such as calculating a location position of a conductive object on a sensor array using the tail-end-effect corrected signal values).
Additional features and examples of alternative embodiments
In certain embodiments, the techniques for correcting tail-end effects described herein may provide for avoiding certain of the disadvantages that may be caused by signal inconsistencies under certain operating conditions.
For example, in the case of a poor signal ground under a large electrical conductor (such as a fat finger, for example), there may be dips that sequence the "donut" contact regions. Such "circular" contacts may cause certain internal sensor elements to be considered to have a tail effect (e.g., have a differential signal value below a tail effect threshold) when detected on the sensor array, while in fact they are in contact. In other words, these differential signal values may be low enough to be below the tail-end effect threshold for a best-fit linear approximation. Thus, when tail effect correction is applied as previously described, the dip in signal value caused by large electrical conductors ("ring" hole) will become larger and may increase the likelihood of contact area separation due to subtraction of tail effect adjustment from already low differential signal values. However, such contact region separation is generally undesirable because it may cause the detection (and position calculation) of two separate contacts rather than a single contact of an actual large electrical conductor (such as a fat finger, for example).
To address this shortcoming, in certain embodiments, the techniques described herein provide for correcting only tail end effects for those sensor elements downstream of the sensor element having the largest RX index value. (Note that in this context, downstream refers to a direction away from the edge of the sensor array where the RX electrodes are routed.)
Fig. 13 illustrates an example method of adjusting tail end effects and avoiding contact region separation that accounts for large conductive body (e.g., such as fat finger) contacts. The method in FIG. 13 includes the same blocks as the method in FIG. 12, except that block 1136B, by which a different element is selected, is as compared to block 1136A in FIG. 12.
The operations of the blocks in fig. 13 are described hereinafter as being performed by processing logic (e.g., such as processing logic 102 in fig. 1). It is noted, however, that various implementations and embodiments may use different and possibly multiple components to perform the method of fig. 13. Thus, the description of the method in FIG. 13 as performed by the processing logic is to be taken in an illustrative rather than a restrictive sense, as follows.
At block 1304, slope parameter (or coefficient) values a for the TX electrodes of the sensor array have been calculated and stored in association with their corresponding TX electrodes. In block 1132, processing logic performs an operation to initialize a "txIndex" variable to zero, which represents the TX index value for the current TX electrode. In block 1134, processing logic determines whether there are any remaining TX electrodes that need to be processed. For example, if the "txIndex" variable is less than the "txLast" variable, then at least the current TX electrode still needs to be processed and the processing logic continues to perform the operations in blocks 1136B through 1144. If the "txIndex" variable is not less than the "txLast" variable, then the differential signal values for the sensor elements of all TX electrodes have been processed and the processing logic continues with the operations in block 1350.
In block 1136B, processing logic selects tail effect adjustments only for those sensor elements whose RX electrodes are downstream of the RX electrode that is detected as part of the scan operation being processed to have the largest differential signal value. For example, processing logic initializes a "rxIndex" variable to a value that is higher than the value of a variable ("rxMax") that represents the RX index value of the RX electrode detected along the current TX electrode with the highest differential signal value. To perform this initialization, processing logic may perform the following operations
rxIndex=rxMax+1
For purposes of the above operations, the "rxMax" variable for each TX electrode may be found and saved in a manner associated with that TX electrode during linear approximation coefficient calculation (e.g., as part of the operations in blocks 1112 through 1124 in fig. 11). By setting the "rxlndex" variable in this manner, the techniques described herein provide differential signal values that will only be corrected for those sensor elements whose RX index values are outside of the range of "rxMax" index values for all TX electrodes. If the sensor array is dual wired, the operations in block 1136B may be applied separately to each side of the sensor array through which the RX electrodes are wired.
In block 1138, processing logic determines whether there are any remaining RX electrodes that need to be processed for the current TX electrode. For example, if the "rxIndex" variable is less than the "rxLast" variable, then at least the current RX electrode still needs to be processed and the processing logic continues to perform the operations in blocks 1140 and 1142. If the "rxIndex" variable is not less than the "rxLast" variable, then the differential signal values from the RX electrode along the current TX electrode have been processed and processing logic continues to perform operations in block 1144 (which sets the next TX electrode for processing).
In block 1140, processing logic adjusts the differential signal values for the tail effect for the current sensor element (which is formed by the current RX electrode indicated by the "rxIndex" variable and the current TX electrode indicated by the "txIndex" variable). For example, processing logic performs the following operations
SignalCorrection ofsignal-Coef [ txIndex ═]*rxIndex
Note that the value (i.e., product) "Coef txIndex" × rxIndex "represents an adjustment value that corrects for the tail effect of the current sensor element.
In block 1142, processing logic sets the RX index value for the next RX electrode that needs to be processed and continues operation in block 1138. After the differential signal values from the selected RX electrode along the current TX electrode have been processed, processing logic determines that the current "rxIndex" variable is not less than the "rxLast" variable in block 1138. Thus, processing logic continues with the operation in block 1144. Processing logic sets the TX index value for the next TX electrode that needs to be processed in block 1144 and continues operation in block 1134. After the differential signal values of the sensor elements of all TX electrodes are adjusted in the manner described above, processing logic determines that the current "txIndex" variable is not less than the "txLast" variable in block 1134. Thus, processing logic continues with operations in block 1350. In block 1350, the processing logic performs the operations described in block 1150 of fig. 11 (e.g., such as operations that calculate a location of a conductive object on the sensor array using the tail-effect corrected signal values).
In certain embodiments, a simple (e.g., faster) implementation of the techniques described herein may include calculating slope parameter values for only those TX electrodes in the middle of the contact region, and adjusting the tail end effect of those sensor elements formed by only those TX electrodes. In these embodiments, the methods for correcting for tail effects are similar to the methods shown in fig. 11 and 12, except that instead of cycling through all TX electrodes, these methods would provide for the operation of selecting only a subset of TX electrodes (e.g., such as only including those in the middle of the contact region).
In certain embodiments, the techniques described herein for correcting for tail end effects may be used not only for mutual capacitive sensor arrays, but also for sensor arrays having a self-capacitance design. Such applications of the techniques described herein are possible for self-capacitance sensor arrays because they also provide a plurality of sensors that can be activated and can produce a signal profile that can be analyzed. Further, the techniques described herein are not only associated with capacitive sensing applications, but may be used with other sensing techniques (e.g., removing shadows in optical sensing applications), as well as any other type of design that provides an array of sensor elements capable of receiving parasitic signals coupled with a linear profile.
Various embodiments of the techniques for correcting tail-end effects described herein may include various operations. These operations may be performed by hardware components, software, firmware, or a combination thereof. As used herein, the term "coupled to" may mean directly coupled to and indirectly coupled to through one or more intervening components. Any of the signals provided over the various buses described herein may be time division multiplexed with other signals and provided over one or more common buses. Additionally, the interconnections between circuit components or blocks may be shown as buses or as single signal lines. Each bus may alternatively be one or more single signal lines, and each single signal line may alternatively be a respective bus.
Particular embodiments may be implemented as a computer program product that may include storage on a non-transitory computer-readable medium (e.g., such as volatile and/or non-volatile storage). The instructions may be used to program one or more devices including one or more general-purpose or special-purpose processors (e.g., such as a central processing unit or CPU) or equivalents thereof (e.g., such as a processing core, processing engine, microcontroller, etc.), such that when the instructions are executed by the processor or equivalents thereof, the instructions cause the device to perform the operations described for correcting the tail end effects described herein. A computer-readable medium may also include one or more mechanisms for storing or transmitting information in a form (e.g., such as software, processing application) readable by a machine (e.g., such as a device or a computer). The non-transitory computer-readable storage medium may include, but is not limited to, an electromagnetic storage medium (e.g., floppy disks, hard disks, etc.), an optical storage medium (e.g., CD-ROMs), magneto-optical storage media, read-only memories (ROMs), Random Access Memories (RAMs), erasable programmable memories (e.g., EPROMs and EEPROMs), flash memory, or another type of media now known or later developed that is suitable for storing information.
Although the operations of the methods herein are shown and described in a particular order, the order of the operations of each method may be changed, such that certain operations may be performed in an inverse order, or such that certain operations may be performed at least partially in parallel with other operations. In other embodiments, instructions or sub-operations of different operations may be performed in an intermittent and/or alternating manner.
In the foregoing specification, the invention has been described with reference to specific exemplary embodiments thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the invention as set forth in the appended claims. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.
Claims (20)
1. An apparatus for correcting tail end effects, comprising:
a sensor array including a plurality of receive RX electrodes and a plurality of transmit TX electrodes, wherein the plurality of RX electrodes and the plurality of TX electrodes are interleaved with each other without crossing in a touch sensitive area in a single layer on a substrate of the sensor array;
a sensor configured to measure a plurality of measurements from the sensor array, wherein the plurality of measurements are representative of an electrical conductor being in contact with or proximate to the sensor array; and
processing logic coupled with the sensor, wherein the processing logic is configured to perform at least the following:
determining a set of adjustment values corresponding to tail end effects associated with the conductive body represented by the plurality of measurements, wherein the adjustment value for a particular TX electrode is calculated based on a sum of indices of RX electrodes along the particular TX electrode; and
generating an adjusted measurement corresponding to the electrical conductor represented by the plurality of measurements based on the set of adjustment values, wherein the adjusted measurement corrects for the tail end effect.
2. The apparatus of claim 1, wherein the tail effect comprises an increase in parasitic signals or a decrease in parasitic signals caused by parasitic coupling between a main trace of an RX electrode and a TX electrode affected by the conductive body, wherein the main trace of the RX electrode is routed adjacent to the TX electrode.
3. The apparatus of claim 2, wherein the main trace of the RX electrode and the shape of the RX electrode are arranged in the touch sensitive area of the sensor array, but the shape of the RX electrode is not affected by the conductive body.
4. The apparatus of claim 1, wherein the sensor array comprises first and second non-sensing regions on opposite sides of the sensor array, wherein a first subset of the plurality of RX electrodes and a first subset of the plurality of TX electrodes are routed from the first non-sensing region and a second subset of the plurality of RX electrodes and a second subset of the plurality of TX electrodes are routed from the second non-sensing region.
5. The apparatus of claim 1, wherein the processing logic is further configured to determine location coordinates of the conductive object on the sensor array based on the adjusted measurements.
6. The apparatus of claim 1, wherein the plurality of measurements comprise signal values of sensor elements formed by the particular TX electrodes of the sensor array, and wherein the adjusted measurements comprise adjustment values corresponding to the signal values.
7. The apparatus of claim 6, wherein, to determine the adjustment value for the particular TX electrode, the processing logic is configured to:
calculating a sum of the indices of RX electrodes forming the sensor element along the particular TX electrode;
calculating a sum of the signal values of the sensor elements along the particular TX electrode;
calculating a parameter value based on a sum of the indices and a sum of the signal values; and
based on at least: each of the signal values, the parameter value, and an index of a corresponding RX electrode are adjusted to obtain a corresponding adjusted value.
8. The apparatus of claim 6, wherein the signal value of the sensor element formed by the particular TX electrode is less than a tail-effect threshold value.
9. The apparatus of claim 6, wherein the RX electrodes forming the sensor elements along the particular TX electrode have an index greater than an index of RX electrodes forming sensor elements having a peak signal value.
10. A method for correcting for tail-end effects, comprising:
receiving a plurality of measurements measured from a sensor array, wherein the plurality of measurements are representative of electrical conductors in contact with or in proximity to the sensor array, wherein the sensor array comprises a plurality of receive RX electrodes and a plurality of transmit TX electrodes, wherein the plurality of RX electrodes and the plurality of TX electrodes are interleaved with each other without crossing in a touch sensitive area in a single layer on a substrate of the sensor array;
the processing device determines a set of adjustment values corresponding to tail end effects associated with the conductive body represented by the plurality of measurements, wherein the adjustment value for a particular TX electrode is calculated based on a sum of indices of RX electrodes along the particular TX electrode; and
generating an adjusted measurement corresponding to the electrical conductor represented by the plurality of measurements based on the set of adjustment values, wherein the adjusted measurement corrects for the tail end effect.
11. The method of claim 10, wherein the tail effect comprises an increase in parasitic signals or a decrease in parasitic signals caused by parasitic coupling between a main trace of an RX electrode and a TX electrode affected by the conductive body, and wherein the main trace of the RX electrode is routed adjacent to the TX electrode.
12. The method of claim 11, wherein the main trace of the RX electrode and a shaped portion of the RX electrode are disposed in the touch sensitive area of the sensor array, but the shaped portion of the RX electrode is not affected by the conductive body.
13. The method of claim 10, further comprising determining differential signals for sensor elements of the sensor array based on the received plurality of measurements.
14. The method of claim 10, wherein:
the plurality of measurements comprises signal values of sensor elements formed by the particular TX electrode of the sensor array; and is
The processing device determining the adjusted measurement results comprises:
calculating a sum of the indices of RX electrodes forming the sensor element along the particular TX electrode;
calculating a sum of the signal values of the sensor elements along the particular TX electrode;
calculating a parameter value based on a sum of the indices and the sum of the signal values; and
based on at least: each of the signal values, the parameter value, and an index of a corresponding RX electrode are adjusted to obtain a corresponding adjusted value.
15. The method of claim 14, wherein the processing device determining the adjusted measurement further comprises:
selecting the signal value of the sensor element formed by the particular TX electrode of the sensor array by comparing the plurality of measurements to a tail effect threshold value.
16. The method of claim 14, wherein the processing device determining the adjusted measurement further comprises:
determining a first index of the RX electrodes forming the sensor element having the peak signal value; and
selecting the signal values for the sensor elements formed by the particular TX electrode of the sensor array by selecting only those signal values that are less than a tail effect threshold value and have an index greater than the first index.
17. The method of claim 10, further comprising determining location coordinates of the conductive object on the sensor array based on the adjusted measurements.
18. A system for correcting for tail end effects, comprising:
a capacitive sensor array comprising a plurality of receive RX electrodes and a plurality of transmit TX electrodes, wherein the plurality of RX electrodes and the plurality of TX electrodes are interleaved with each other without crossing in a touch sensitive area in a single layer on a substrate of the capacitive sensor array;
a capacitive sensor coupled with the capacitive sensor array, the capacitive sensor configured to measure a plurality of measurements from the plurality of RX electrodes, wherein the plurality of measurements are representative of an electrical conductor being in contact with or proximate to the capacitive sensor array; and
processing logic coupled with the capacitive sensor, wherein the processing logic is configured to perform at least the following:
determining a set of adjustment values corresponding to tail end effects associated with the conductive body represented by the plurality of measurements, wherein the adjustment value for a particular TX electrode is calculated based on a sum of indices of RX electrodes along the particular TX electrode; and
generating an adjusted measurement corresponding to the electrical conductor represented by the plurality of measurements based on the set of adjustment values, wherein the adjusted measurement corrects for the tail end effect.
19. The system of claim 18, wherein:
the tail effect comprises an increase in or decrease in parasitic signals caused by parasitic capacitive coupling between a main trace of an RX electrode and a TX electrode affected by the conductive body, wherein the main trace of the RX electrode is routed adjacent to the TX electrode; and is
The main trace of the RX electrode and the shaped portion of the RX electrode are disposed in the touch sensitive area of the capacitive sensor array, but the shaped portion of the RX electrode is not affected by the conductive body.
20. The system of claim 18, wherein the capacitive sensor array includes a first non-sensing area and a second non-sensing area on opposite sides of the capacitive sensor array, wherein a first subset of the plurality of RX electrodes and a first subset of the plurality of TX electrodes are routed from the first non-sensing area and a second subset of the plurality of RX electrodes and a second subset of the plurality of TX electrodes are routed from the second non-sensing area.
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US13/800,468 US8866490B1 (en) | 2013-01-18 | 2013-03-13 | Method and apparatus for eliminating tail effect in touch applications |
US13/800,468 | 2013-03-13 | ||
US201361785131P | 2013-03-14 | 2013-03-14 | |
US61/785,131 | 2013-03-14 | ||
US14/038,423 US8866491B2 (en) | 2011-02-24 | 2013-09-26 | Tail effect correction for SLIM pattern touch panels |
US14/038,423 | 2013-09-26 | ||
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