Input device based on voltage gradients

An input device is disclosed, including a first drive electrode comprising a resistive material and a first sense electrode disposed proximate to the first drive electrode. The input device further includes a processing system which is coupled with the first drive electrode and the first sense electrode. In one embodiment, the processing system is configured for electrically driving a first end of the first drive electrode and electrically driving a second end of the first drive electrode to cause a change in a voltage gradient along a length of the first drive electrode. In such an embodiment, the change in the voltage gradient generates a first electrical signal in the first sense electrode. The processing system also acquires a first measurement of the first electrical signal and determines positional information along the length of the first drive electrode based upon the first measurement, wherein the positional information is related to an input object.

This Application is related to U.S. patent application Ser. No. 12/815,662, entitled “SINGLE LAYER CAPACITIVE IMAGE SENSING,” by Hargreaves et al., with filing date Jun. 15, 2010, and assigned to the assignee of the present invention.

This Application is related to U.S. patent application Ser. No. 12/847,598, entitled “SINGLE LAYER TRANSCAPACITIVE SENSING,” by Badaye, with filing date Jul. 30, 2010, and assigned to the assignee of the present invention.

BACKGROUND

Capacitive sensing is a key technology in the implementation of sophisticated modern human-machine interfaces. Capacitive sensing can involve sensing the proximity, contact, and/or position of an input object such as a human finger, a stylus, or some other object. Often, capacitive sensing devices are based on the measurement of mutual capacitance, which is also sometimes known as transcapacitance.

DESCRIPTION OF EMBODIMENTS

Reference will now be made in detail to various embodiments of the subject matter, examples of which are illustrated in the accompanying drawings. While various embodiments are discussed herein, it will be understood that the scope of the invention is not intended to be limited to these embodiments. On the contrary, the scope of the invention is intended to cover alternatives, modifications and equivalents that may be included within the spirit and scope of the various embodiments. Furthermore, in this Description of Embodiments, numerous specific details are set forth in order to provide a thorough understanding of embodiments of the present subject matter. However, embodiments may be practiced without these specific details. In other instances, well known methods, procedures, components, and circuits have not been described in detail in order to avoid unnecessarily obscuring aspects of the described embodiments.

Overview of Discussion

The discussion will begin with a description of an example input device. The input device includes a sensor, which itself includes one or more sensor electrodes. Several non-inclusive example configurations of sensors and their corresponding sensor electrode arrangements will be described. As will be explained herein, operation of the input device is based upon the establishment of a voltage gradient along or across one or more sensor electrodes. Operation of the input device will be described in detail in conjunction with descriptions of some example methods of position sensing, according to various embodiments.

Example Input Device

FIG. 1is a block diagram of an input device100representing an example embodiment of the present invention. The input device100may be configured to provide input to an electronic system (not shown). As used in this document, “electronic system” (also “electronic device”) broadly refers to any system capable of electronically processing information. Some non-limiting examples of electronic systems include personal computers of all sizes and shapes, such as desktop computers, laptop computers, tablets, web browsers, book readers, and personal digital assistants (PDAs). Additional example electronic systems include composite input devices, such as physical keyboards that include input device100and separate joysticks or key switches. Further example electronic systems include peripherals such as data input devices (including remote controls and mice), and data output devices (including display screens and printers). Other examples include remote terminals, kiosks, and video game machines. Other examples include communication devices (including cellular phones such as smart phones), and media devices (including recorders, editors, and players such as televisions, set top boxes, music players, digital photo frames, and digital cameras). Additionally, the electronic system could be a host or a slave to the input device.

Input device100comprises substrate102, sensor108, conductive routing traces104, and processing system110. Sensor108further comprises sensor electrodes (not shown), and the conductive routing traces104serve to electrically couple the processing system110with the sensor electrodes. In some of the following embodiments, conductive routing traces104may also be referred to as routing traces104, or routing traces104may be referred to as composing a communicative coupling between processing system110and sensor108. In embodiments described herein, conductive routing traces104comprise various combinations of conductive routing traces DL0, DL1, DL2, etc., conductive routing traces DR0, DR1, DR2, etc., conductive routing traces SX0, SX1, SX2, etc. and conductive routing traces DRCOMand DLCOM. The particular combination of conductive routing traces composing a particular embodiment will be described in conjunction with that embodiment. Further, in some of the following embodiments, conductive routing traces104may be referred to as composing a communicative coupling between processing system110and sensor108.

InFIG. 1, a processing system (or “processor”)110is shown as part of the input device100. The processing system110is configured to operate the hardware of the input device100to detect input objects in a sensing region of sensor108. The processing system110may comprise parts of or all of one or more integrated circuits (ICs) or other hardware; and, in some embodiments, the processing system110also comprises firmware code, software code, and/or the like. In some embodiments, components comprising the processing system110are located together, such as near the sensor108of the input device100. In other embodiments, components of processing system110are physically separated, with one or more components close to sensor108of input device100and one or more components elsewhere. For example, the input device100may be peripheral to a desktop computer, and the processing system110may comprise software configured to run on a central processing unit of the desktop computer and one or more ICs (perhaps with associated firmware) separate from the central processing unit. As another example, the input device100may be physically integrated in a phone, and the processing system110may comprise circuits and firmware that are part of a main processor of the phone. In some embodiments, the processing system110is dedicated to implementing the input device100. In other embodiments, the processing system110also performs other functions, such as operating display screens, driving haptic actuators, etc.

In some embodiments, the processing system110responds to input objects (or lack of input objects) in the sensing region directly by causing actions. Example actions include changing operation modes, as well as GUI actions such as cursor movement, selection, menu navigation, and other functions. In some embodiments, the processing system110provides information about the input objects (or lack of input objects) to some part of the electronic system (e.g. to a central processing system of the electronic system that is separate from the processing system110, if such a separate central processing system exists). In some embodiments, some part of the electronic system processes information received from the processing system110to act on user input, such as to facilitate a full range of actions, including mode changing actions and GUI actions.

For example, in some embodiments, the processing system110operates the sensor108of the input device100to produce electrical signals indicative of input objects (or lack of input objects) in the sensing region. The processing system110may perform any appropriate amount of processing on the electrical signals in producing the information provided to the electronic system. For example, the processing system110may merely digitize the electrical signals. As another example, the processing system110may perform filtering or other signal conditioning. As yet another example, the processing system110may subtract or otherwise account for a baseline, such that the information reflects a difference between the electrical signals and the baseline. As yet further examples, the processing system110may determine “positional information,” recognize motion of input objects as commands, recognize handwriting, and the like.

In operation, sensor108defines a sensing region for sensing input objects. The term “sensing region” as used herein is intended to broadly encompass any space above, around, in and/or near the sensor wherein the sensor is able to detect an input object. In a conventional embodiment, a sensing region extends from a surface of the sensor in one or more directions into space until the distance between the object and the sensor prevents accurate detection. This distance may be on the order of less than a millimeter, millimeters, centimeters, or more, and may vary significantly with the type of position sensing technology used and the accuracy desired. Accordingly, the planarity, size, shape and exact locations of the particular sensing regions can vary widely from embodiment to embodiment.

Sensing regions with a generally rectangular projected shape are common, although many other shapes are possible. For example, depending on the design of the sensor electrodes and surrounding components, sensing regions can be made to have two-dimensional projections of other shapes. Similar approaches can be used to define the three-dimensional shape of the sensing region. For example, any combination of sensor design, shielding, signal manipulation, and the like can effectively define a three-dimensional sensing region. Although sensor108is depicted as rectangular, other shapes, such as circular, are anticipated.

InFIG. 1, a capacitive sensing reference surface or “cover layer” is not illustrated over sensor108, so as not to obscure other portions which are being discussed. However, it is appreciated that such a capacitive sensing reference surface, which may be made of a clear material, typically prevents input objects from coming into direct contact with the sensor electrodes composing sensor108.

In operation, processing system110acquires one or more capacitance measurements related to the sensor electrodes composing sensor108. These capacitance measurements enable the sensing of input objects with respect to the sensing region formed by sensor108. In some embodiments, such measurements can be utilized by processing system110to determine input object positional information relative to the sensing region formed by sensor108.

The positional information determined by processing system110can be any suitable indicia of object presence. For example, the processing system can be implemented to determine “zero-dimensional” positional information (e.g. near/far or contact/no contact) or “one-dimensional” positional information as a scalar (e.g. position or motion along a sensing region). Processing system110can also be implemented to determine multi-dimensional positional information as a combination of values (e.g. two-dimensional horizontal/vertical axes, three-dimensional horizontal/vertical/depth axes, angular/radial axes, or any other combination of axes that span multiple dimensions), and the like. Processing system110can also be implemented to determine information about time or history.

Furthermore, the term “positional information” as used herein is intended to broadly encompass absolute and relative position-type information, and also other types of spatial-domain information such as velocity, acceleration, and the like, including measurement of motion in one or more directions. Various forms of positional information may also include time history components, as in the case of gesture recognition and the like. The positional information from the processing system110facilitates a full range of interface inputs, including use of the input device as a pointing device for cursor control, scrolling, and other functions.

In some embodiments, the input device100is implemented with additional input components that are operated by the processing system110or by some other processing system. These additional input components may provide redundant functionality for input in the sensing region, or to provide some other functionality. Buttons are one example of additional input components that can be used to facilitate selection of items using the input device100. Other types of additional input components include sliders, balls, wheels, switches, and the like. Conversely, in some embodiments, the input device100may be implemented with no other input components.

It should be understood that while many embodiments of the invention are to be described here in the context of a fully functioning apparatus, some mechanisms of the present invention are capable of being distributed as a program product (e.g., software) in a variety of forms. For example, some mechanisms of the present invention may be implemented and distributed as a software program on information bearing media that is readable by electronic processors (e.g., non-transitory computer-readable and/or recordable/writable information bearing media that is readable by the processing system110). Additionally, the embodiments of the present invention apply equally regardless of the particular type of medium used to carry out the distribution. Examples of non-transitory, electronically readable media include various discs, memory sticks, memory cards, memory modules, and the like. Electronically readable media may be based on flash, optical, magnetic, holographic, or any other storage technology.

It is noted that some example embodiments of sensor electrode patterns composing sensor108are described herein and shown inFIGS. 2A-8. It is appreciated that these descriptions andFIGS. 2A-8are provided by way of example and not of limitation. In general, other zero-dimensional, one-dimensional, or two-dimensional capacitive sensor electrode patterns that follow the principles described herein can also be used. These include sensors comprising single layer or multi-layer sensor electrode patterns.

EXAMPLE SENSOR DESIGNS

FIG. 2Aillustrates a top view of a sensor108A, according to an embodiment. Sensor108A represents an example of a sensor108in input device100ofFIG. 1. As illustrated, sensor108A includes two sensor electrodes (D0and S0), one of which is designated as a drive electrode (D0) and the other of which is designated as a sense electrode (S0). The drive electrode D0is electrically conductive, but has a non-zero resistivity. During operation, the non-zero resistivity allows a voltage gradient to be established along the length of the drive electrode. In one embodiment, the non-zero resistivity is substantially uniform along the length of the drive electrode. Conductive routing trace DL0couples processing system110to the left end of drive electrode D0, and conductive routing trace DR0couples processing system110to the right end of drive electrode D0. Conductive routing trace SX0couples processing system110to sense electrode S0. It is appreciated that other embodiments of sensor108A can include a greater number of sensor electrodes. For example,FIG. 2Billustrates an embodiment with a greater number of drive electrodes, andFIG. 3Aillustrates an embodiment with a greater number of drive electrodes and a greater number of sense electrodes.

As illustrated inFIG. 2A, drive electrode D0of sensor108A is elongated along axis201(e.g., an X-axis of a Cartesian coordinate system). Sense electrode S0of sensor108A is disposed proximate to drive electrode D0. In the illustrated embodiment, sense electrode S0is disposed substantially parallel to drive electrode D0. It is appreciated that while the following description may refer to methods for determining the position of an input object along an X-axis and Y-axis of a Cartesian coordinate system, the axes are used only as examples and the axes may be reversed, or other coordinate systems may be used.

Even though the sensor electrodes are illustrated as being substantially rectilinear, many other shapes are possible. For example, nonlinear shapes may be used. Further, in some embodiments, the width of a sensor electrode may vary along its length. In other embodiments, one or more sides of a sensor electrode may be curved. In further embodiments, the sensor electrodes may be shaped to affect the capacitive coupling between pairs of drive and sense electrodes. In yet other embodiments, the resistivity, width, depth or thickness of a sensor electrode may also be varied to change its conductance. In various embodiments, the sensor electrodes may be shaped based on the desired shape of sensor108. In some embodiments any two sensor electrodes may extend for different lengths along a common axis. In further embodiments, the sensor electrodes may be shaped based on one or more of the characteristics of input device100.

In some embodiments, sensor108A is constructed as a single-layer sensor, meaning that drive electrode D0and sense electrode S0are disposed in the same layer on substrate102. In other embodiments, drive electrode D0and sense electrode S0may be disposed in different layers on substrate102without altering the general operation of sensor108A. In various embodiments, manufacturing costs related to a single-layer sensor design may be lower than manufacturing costs related to a sensor design having more layers. In other embodiments, drive electrode D0and sense electrode S0may be disposed on different substrates. In one embodiment, processing system110may be configured to operate as a one-dimensional input device when coupled with sensor108A. In other embodiments, sensor108A may be part of a larger sensor, such as sensor108E ofFIG. 3A.

In one embodiment, the sensor electrodes D0and S0in sensor108A can be constructed from transparent conductive material, such as patterned ITO, ATO, carbon fiber nanotubes or other substantially transparent materials disposed on a transparent substrate (e.g., substrate102). In such an embodiment, the transparent electrodes and substrate result in a transparent touch sensor that may be used in touch screen applications. In one embodiment, drive electrode D0is further constructed from a conductive material of substantially uniform resistivity, so that uniform left-to-right voltage gradients can be imposed on it by the driving methods described below. In some embodiments, in sensor108A (and other sensors108described herein) the conductive material may have non-uniform resistivity, such as having a higher or lower resistivity on the distal ends than in the middle portion. Other forms of non-uniform resistivity can also be accommodated.

In general, a voltage gradient may be defined as the amount of change in voltage as a function of a small change in position along a resistive electrode such as D0. For a drive electrode driven by voltages at two points, the voltage will be monotonic along the length of the electrode between those two points. Therefore, the voltage gradient will be either positive along the length of the electrode between the two points, negative along the length of the electrode between the two points, or zero along the length of the electrode between the two points. With continued reference toFIG. 2A, in various embodiments processing system110can create voltage gradients along the drive electrode D0by driving a current through it, or by driving voltages onto DL0and DR0. In one embodiment, when drive electrode D0comprises a substantially uniform width, thickness, and resistivity along its length, the voltage gradient will be a constant value along the length of the drive electrode D0. In such a case, the voltage gradient can be defined as the difference in voltage between DL0and DR0, divided by the length of the drive electrode. Note that in this case the voltage gradient is a signed value, and it can be positive, negative, or zero. Changing each of the voltages on DL0and DR0by substantially the same amount changes the absolute voltage on drive electrode D0with respect to an external reference such as the voltage on sense electrode S0, but it does not substantially change the voltage gradient since the difference between the voltages remains substantially constant.

In one embodiment, processing system110drives a voltage VL0onto DL0and a voltage VR0onto DR0. When drive electrode D0has substantially uniform width, thickness, and resistivity, then the voltage at any point along its length will be given by equation 1:
V(x)=VL0+(VR0−VL0)xEquation 1

In equation 1, x represents the position along drive electrode D0, with x=0 representing its left end and x=1 representing its right end, and V(x) represents the voltage on drive electrode D0at position x, thus defining a first voltage gradient along drive electrode D0.

Subsequently, processing system110can drive potentially different voltages V′L0onto DL0and VR0onto DR0. The voltage at any point along the drive electrode D0will then be given by equation 2:
V′(x)=V′L0+(V′R0−V′L0)xEquation 2

In equation 2, x is defined as above and V′(x) represents the new voltage on drive electrode D0at position x, thus defining a second voltage gradient along-drive electrode D0.

As a result of this change in drive voltages, from VL0to V′L0on DL0and from VROto V′R0on DR0, the change in voltage along drive electrode D0will be given by δV(x) as shown in equation 3:
δV(x)=V′(x)−V(x)=δVL0+(δVR0-δVL0)xEquation 3

In equation 3, x is defined as above, δVL0is the change in voltage driven by processing system110onto DL0(i.e. V′L0-VL0), and δVR0is the change in voltage driven by processing system110onto DR0(i.e. V′R0-VR0).

In response to the changing voltage δV(x) along the length of drive electrode D0, an electrical signal (i.e. sense signal) will be generated on sense electrode S0due to capacitive coupling (or transcapacitance) between the drive electrode D0and the sense electrode S0. Herein, the terms “generate” and “generated” are applied in their common usage, meaning “to bring into being” and “brought into being”, as opposed to any more specific electrical engineering definitions. The sign and magnitude of the sense signal depends on δV(x) along the length of D0, and on the distributed capacitive coupling between D0and S0along their lengths. Further, in various embodiments, the sense signal can be measured by processing system110.

In one embodiment, when no finger or other input object is present in the sensing region of sensor108A, the measurement S of the sense signal on sense electrode S0is proportional to the integral along the length of the electrode of the distributed capacitive coupling C(x) multiplied by the distributed change in voltage δV(x). In some embodiments, when the spacing between the drive and sense electrodes is substantially uniform along their lengths, then the distributed capacitive coupling between them will also be substantially uniform along their lengths. In such embodiments, the measurement S of the sense signal is approximated by:
S=K C(δVR0+δVL0)/2  Equation 4
where K is a proportionality constant and C represents the total capacitive coupling between the drive and sense electrodes along their lengths.

In various embodiments, the measurement S may represent a baseline measurement with no input object present. When a finger or other input object approaches the sensor, it changes the capacitive coupling between D0and S0in the region near the input object and a second measurement S′ of the sense signal can be acquired as described above, driving the drive electrode in the same way. The total change in capacitive coupling due to the input object can be represented by ΔC, and the change ΔS in the measurement of the sense signal with respect to the baseline measurement is given by:
ΔS=S′−S=K ΔCδV(x0)  Equation 5
where x0represents the centroid (i.e. the representative X-position along axis201) of the capacitive influence of the input object, and δV(xL0) is given by equation 3. Substituting equation 3 into equation 5 gives equation 6:
ΔS=K ΔC[δVL0+(δVR0−δVL0)x0]  Equation 6

By controlling δVL0and δVR0to take two independent measurements of ΔS, both the position of the input object (x0) and the magnitude of its influence (ΔC) can be determined by processing system110.

In the embodiment described above, the baseline value S is determined from a measurement of a sense signal when no input object is present in the sensing region. In other embodiments, the baseline value may be a predetermined value.

In one embodiment, a first measurement can be obtained by driving both ends of drive electrode D0(i.e. DL0and DR0) with the same voltage change δV0so that equation 6 simplifies to equation 7:
ΔS1=K ΔC δV0Equation 7

Equation 7 yields ΔC from known or measured quantities. In one embodiment, driving both ends of drive electrode D0with the same voltage change can be accomplished by driving both DL0and DR0with the same voltage waveform. In another embodiment, driving both ends of drive electrode D0with the same voltage change can be accomplished by driving one end with a voltage waveform and leaving the other end electrically disconnected or in a high impedance state.

In one embodiment, once ΔC is known, the first and second routing traces (i.e. DLOand DR0) can be driven with differing voltage changes to generate a second sense signal in the sense electrode. A measurement ΔS2of the second sense signal can be acquired, and positional information x0for an input object can be determined from equation 5 using ΔS2and the previously measured value ΔC. Alternatively, in another embodiment, processing system110can drive one conductive routing trace (e.g. DL0) with a constant voltage (e.g. 0 volts or ground) while driving the second conductive routing trace (e.g. DR0) with a changing voltage. If the changing voltage is equal in magnitude to the voltage change δV0used to take the first measurement, then equation 6 reduces to equation 8:
ΔS2=K x0δC δV0Equation 8

Equation 8 gives x0from known or measured quantities by rearranging and substituting terms:
x0=ΔS2/ΔS1Equation 9

In yet another embodiment, a first measurement ΔS1can be obtained by holding DL0at a fixed voltage (e.g. 0 volts or ground) and driving DR0through a voltage change δV0. Then a second measurement ΔS2can be obtained by driving DL0through the same voltage change δV0, and holding DR0at a fixed voltage (e.g. 0 volts or ground). In this case, the position information x0for the input object is given by equation 9:
x0=ΔS1/(ΔS1+ΔS2)  Equation 10

And the total change in measured capacitance ΔC due to the presence of the input object is given by equation 10:
ΔC=K(ΔS1+ΔS2)/δV0Equation 11

In the description given above, the driven voltages can in general be static voltages, step voltages, time-varying voltages, or other types of voltage waveforms. Note that these are only example methods of determining an input object's presence and position. The same information can be obtained by driving the voltages on DL0and DR0in many other ways in accordance with the general formulation described above. Further, in many of the described embodiments, while a sensor electrode may be described as being driven by processing system110or processing system110may be described as driving a sensor electrode, the sensor electrode may also be described as being electrically driven by processing system110or processing system110may be described as electrically driving a sensor electrode.

FIG. 2Bshows another embodiment of sensor108of input device100ofFIG. 1. Sensor108B contains a second drive electrode D1, coupled to processing system110via routing traces DL1and DR1. In one embodiment drive electrode D0and drive electrode D1comprise a substantially similar resistive material. In another embodiment, drive electrode D0and drive electrode D1comprise substantially different resistive materials. In the embodiment ofFIG. 2B, drive electrode D1can be driven with the same voltage waveforms and at the same time as drive electrode D0, as described above with reference toFIG. 2A. Alternatively, each drive electrode can be driven independently and/or at different times.

Compared to the embodiment ofFIG. 2A, in the embodiment shown inFIG. 2Bthe additional drive electrode may result in a stronger signal generated on sense electrode S0due to the addition of the capacitive coupling between the second drive electrode and the sense electrode. Further, the additional drive electrode D1may help to shield the sense electrode S0from nearby sources of electrical interference. Furthermore, if drive electrode D1is driven at a different time from drive electrode D0, then the resulting two independent measurements on sense electrode S0may provide information indicative of the input object's location along axis202.

FIG. 2Cshows another embodiment of sensor108in input device100ofFIG. 1. Sensor108C contains a second drive electrode D1, coupled to processing system110via routing trace DL1. In this embodiment, conductive element230, represented by the vertical bar on the right side of sensor108C, electrically couples together one end of each drive electrode D0and D1such that the coupled ends of the drive electrodes may be commonly coupled to processing system110via the common routing trace DRCOM. In some embodiments, where sensor108C is substantially transparent, conductive element230might not be transparent since it may be located outside the sensor active area and would not be visibly obstructive to a display located beneath the sensor. In such an embodiment, conductive element230may be implemented with an opaque conductive material such as a screen-printed silver ink. In other embodiments, conductive element230is a set of routing traces that are coupled together (as is illustrated inFIG. 5) or may be made of the same or different resistive material as drive electrodes D0and D1. Further, in some embodiments, conductive element230may be constructed from a transparent conductive material.

During operation, the embodiment ofFIG. 2Cputs a constraint on the ability of processing system110to drive each of the drive electrodes independently. In this case, since the right ends of both drive electrodes are coupled together, the rights ends will both be driven with the same voltage waveform via routing trace DRCOM. Processing system110may still drive the left ends of each drive electrode independently. In this embodiment, the presence and position of an input object can be determined in the same way as described above with reference toFIGS. 2A and 2B. Compared with the embodiment ofFIG. 2B, the embodiment ofFIG. 2Creduces the number of conductive routing traces between the sensor and processing system110.

FIG. 2Dshows yet another embodiment of sensor108of input device100ofFIG. 1. In sensor108D, two drive electrodes D0and D1are electrically coupled together at each end via conductive elements231and230. The common ends of the drive electrodes are further coupled to processing system110via the common routing traces DLCOMand DRCOM. Since both ends of each drive electrode are coupled together, each drive electrode will be driven with the same voltage waveforms. In this embodiment, the presence and position of an input object can be determined in the same way as described above with reference toFIGS. 2A and 2B. Compared with the embodiment ofFIG. 2C, the embodiment ofFIG. 2Dfurther reduces the number of conductive routing traces between the sensor and processing system110.

FIG. 3Aillustrates a top view of a sensor108E, according to an embodiment. Sensor108E represents an example of a sensor108, composed in input device100ofFIG. 1. Sensor108E can be viewed as an extension of sensors108A or108B, having additional drive and sense electrodes arrayed along a second axis202. These additional electrodes allow the input device to determine two-dimensional positional information for input objects. In one embodiment, two-dimensional positional information may be determined along axis201and axis202. As shown, sensor108E includes a plurality of sensor electrodes (D0-D5and S0-S4), some of which are designated as drive electrodes (D0-D5) and others of which are designated as sense electrodes (S0-S4). It is appreciated that other embodiments of sensor108E can include a greater or lesser number of sensor electrodes. In one embodiment, conductive routing traces DL0-DL5couple processing system110with the left ends of drive electrodes D0-D5, respectively, and conductive routing traces DR0-DR5couple processing system110with the right ends of drive electrodes D0-D5, respectively. Further, conductive routing traces Sx0-Sx4couple processing system110with sense electrodes S0-S4, respectively. In one embodiment, each conductive routing trace is coupled to an end of an associated drive electrode. For example, in one embodiment, conductive routing trace DR0is coupled to the right end of associated drive electrode D0. In another embodiment, conductive routing trace DL0is coupled to the left end of associated drive electrode D0. In a further embodiment, conductive routing traces DL1is coupled to the left end of associated drive electrode D1.

As is illustrated, drive electrodes such as D1of sensor108E are elongated along axis201(e.g., an X-axis of a Cartesian coordinate system). Sense electrodes such as S1of sensor108E are disposed proximate to the drive electrodes. In one embodiment, sense electrodes such as S1are disposed substantially parallel to the drive electrodes. For example, sense electrodes S0-S1are parallel with drive electrodes D0-D5.

In some embodiments, sensor108E is constructed as a single-layer sensor, meaning that drive electrodes D0-D5and sense electrodes S0-S4are disposed in the same layer on substrate102. In other embodiments, drive. electrodes D0-D5and sense electrodes S0-S4may be disposed in different layers on substrate102, or on different substrates, without altering the general operation of sensor108E.

Sensor108E can be operated as an extension of sensors108A or108B, following the same principles described above with reference toFIG. 2A, and as further described below, and in conjunction with flow diagram900(FIGS. 9A and 9B). Drive electrodes D0-D5can be driven one-at-a-time, in various groupings, or all at the same time. Likewise, the sense signals on sense electrodes S0-S4can be measured one-at-time, in various groupings, or all together. As described with reference toFIG. 2Aabove, the measurement of the sense signal on any sense electrode (e.g. S1) can be used to determine the presence of an input object in proximity to it, as well as the position of the input object along its length (along axis201).

Furthermore, the position of an input object along the second axis202can be determined from the measurements of the sense signals on a plurality of the sense electrodes S0-S4. For example, the sense electrode nearest the input object may have a correspondingly large change in its measured sense signal, while sense electrodes far away from the input object may have little or no change in their measured sense signals. In one embodiment, the position of an input object along axis202can be determined by finding which sense electrode has the largest measured sense signal change. In other embodiments, the position of an input object along axis202may be determined from the set of measured changes in capacitive coupling by using a peak detection algorithm, or a peak fitting algorithm, or something similar.

FIG. 3Billustrates a top view of a sensor108F, according to an embodiment. Sensor108F represents an example of a sensor108, composed in input device100ofFIG. 1. As in the embodiment ofFIG. 2C, conductive element230electrically couples together the right ends of each drive electrode D0-D5such that the right ends of the drive electrodes may be commonly coupled to processing system110via the common conductive routing trace DRCOM.

During operation, since the right ends of all drive electrodes are coupled together, the rights ends will all be driven with the same voltage waveform via routing trace DRCOM. However, the sense electrodes S0-S4are not coupled together, and therefore the sense signals are independent and can be independently measured by processing system110. Therefore, in this embodiment, positional information, including the presence and position of an input object, can be determined in the same way as described above with reference toFIG. 3A(and with further reference toFIGS. 2A and 2B). Compared with the embodiment ofFIG. 3A, the embodiment ofFIG. 3Breduces the number of conductive routing traces between the sensor and processing system110.

FIG. 3Cillustrates a top view of a sensor108G, according to another embodiment. Sensor108G represents an example of a sensor108, composed in input device100ofFIG. 1. As in the embodiment ofFIG. 2D, conductive element230electrically couples together the right ends of each drive electrode D0-D5such that the right ends of the drive electrodes may be commonly coupled to processing system110via the common routing trace DRCOM. Further, conductive element231electrically couples together the left ends of each drive electrode D0-D5such that the left ends of the drive electrodes may be commonly coupled to processing system110via the common routing trace DLCOM.

During operation, since both ends of each drive electrode are coupled together, all the drive electrodes will be driven with the same voltage waveforms via routing traces DLCOMand DRCOM. However, the sense electrodes S0-S4are not coupled together, and therefore the sense signals will be independent and can be independently measured. Positional information, including the presence and position of an input object, can be determined in the same way as described above with reference toFIG. 3A(and with further reference toFIGS. 2A and 2B). Compared with the embodiment ofFIG. 3B, the embodiment ofFIG. 3Cfurther reduces the number of conductive routing traces between the sensor and processing system110.

FIG. 4Ashows the outline340of an input object on sensor108E, according to one embodiment. As can be seen, the input object is approximately centered over sense electrode S1along axis202, at a distance x from the left edge of the sensor108E along axis201. The outline340represents the region over which the input object influences the capacitive couplings between the drive electrodes and the sense electrodes. Shaded area341shows the region in which the input object influences the capacitive coupling between sense electrode S1and drive electrodes D1and D2. The outline of the input object is widest in this area, and therefore the largest change in the capacitive coupling will be measured on sense electrode S1. Smaller changes in capacitive coupling will be measured on sense electrodes S0and S2, and substantially no changes will be measured on the remaining sense electrodes. As described above, in one embodiment, the position along axis202of an input object (e.g., the Y-component of the position) can be computed from the set of measured changes in capacitive coupling by using a peak detection algorithm, or a peak fitting algorithm, or something similar.

In some embodiments, one or more techniques can be employed to enhance position resolution along axis202. For example,FIG. 4Bshows how, in one embodiment, the region of influence441measured by sense electrode S1can be reduced, as compared to region341, by driving only drive electrode D1. Subsequently, the other portion of region341can be measured by driving only drive electrode D2. In this manner, two separate measurements can be taken on sense electrode S1, each representing a different region of influence. The result can be an approximate doubling of the position resolution along axis202.

It is appreciated that, while driving with one drive electrode, the electrical signal on the two sense electrodes on either side of it can be measured simultaneously by processing system110. Moreover, in other embodiments, since it may already known from earlier measurements which sense electrodes are influenced by input object340, a high-resolution measurement can be restricted to just the relevant drive and sense electrodes near input object340to save time and power. In one embodiment, the effective resolution along axis202is effectively doubled. In another embodiment, this enhanced resolution allows a reduction in the number of sensor electrodes by about half, and thus a reduction in the number of conductive routing traces104between the sensor and processing system110. In yet another embodiment, this enhanced resolution allows for an increased sensor pitch and thus a larger sensor, without increasing the number of sensor electrodes or conductive routing traces104.

FIG. 5illustrates a top view of a sensor108H that is an alternative design, in accordance with another embodiment. As illustrated inFIG. 5, in sensor108H conductive element230of sensor108F (inFIG. 3B) has been replaced by conductive element530, comprising a set of conductive traces that couple together the right ends of drive electrodes D0-D5. Sensor108H operates in the manner previously described in conjunction with sensor108F. In various embodiments, the conductive element530can couple the drive electrode ends together near the sensor, near the processing system110, or anywhere in between.

FIG. 6illustrates a top view of a sensor108I that is an alternative design, in accordance with another embodiment. In sensor108I the DRCOMtrace is routed along the edges of the sensor so that all of the conductive routing traces come off a single side (the left side as illustrated) of sensor108I. Routing the conductive routing traces off a single side can simplify system integration and reduce cost by decreasing the number and/or length of cables between the sensor and processing system110.FIG. 6shows DRCOMrouted along both the top and bottom edges of the sensor, however, in some embodiments a single conductive routing trace along either the top or the bottom edge would be sufficient. In the embodiment ofFIG. 6there is a small inactive border region along the top and/or bottom edges of the sensor where the DRCOMtraces are routed. In one embodiment, the alternative constructions108H and108I may be combined.

FIG. 7Aillustrates a top view of a sensor108J, which is a further embodiment of sensor108in input device100. As illustrated, sensor108J includes a plurality of sensor electrodes (D0-D7and S0-S6), some of which are designated as drive electrodes (D0-D7) and others of which are designated as sense electrodes (S0-S6). It is appreciated that other embodiments of sensor108J can included a greater or lesser number of sensor electrodes. InFIG. 7A, conductive routing traces DL0-DL7couple processing system110with drive electrodes D0-D7, respectively, and conductive routing traces Sx0-Sx6couple processing system110with sense electrodes S0-S6, respectively.

As is illustrated, drive electrodes such as D1of sensor108J are elongated along axis201(e.g., an X-axis of a Cartesian coordinate system). Sense electrodes such as S1of sensor108J are disposed proximate to and substantially parallel to the drive electrodes. For example, sense electrodes S0-S6are parallel to drive electrodes D0-D7. Furthermore, conductive element730electrically couples together the right ends of each drive electrode D0-D7. Sensor108J has similarity to sensor108F inFIG. 3B. However, some differences in construction between sensor108J and sensor108F are described with respect toFIGS. 7A-7Cand8. Namely, in sensor108J there is no common routing trace DRCOMcoupling the right ends of the drive electrodes or conductive element730with processing system110. Thus, the design illustrated inFIG. 7Aeliminates the need for any border wires while still allowing the conductive routing traces to come off a single side of the sensor. In general, sensor108J operates in the same manner as sensors108F and108H, except that processing system110may employ different driving sequences to the drive electrodes of sensor108J, and may apply different computations to the measured sense signals. It is appreciated that the sensor electrodes (D0-D7and S0-S6) and conductive element730may all be disposed in the same layer on a substrate, such as substrate102, however this is not required. In some embodiments, conductive element730and drive electrodes D0-D7form a comb-shaped electrode, where conductive element730is the spine of the comb-shaped electrode and the drive electrodes D0-D7are the tangs.

FIG. 8shows the outline of an input object840on sensor108J, according to one embodiment. Shaded area841shows the region in which input object840influences the capacitive coupling between sense electrode S1and drive electrodes D1and D2.

In some embodiments, to detect the presence of input object840on the sensor108J and/or its position along axis202, processing system110drives all the routing traces DL0-DL7with a common voltage waveform. Processing system110can then measure the sense signal on each sense electrode to determine a change in the capacitive coupling between each sense electrode and nearby drive electrodes. In one embodiment, from these measurements the presence of an input object and its position along axis202(e.g., the Y-component of the position) can be determined using a peak detection algorithm, or a peak fitting algorithm, or something similar.

In some embodiments, to measure the position of input object840along axis201, processing system110acquires at least two sets of measurements. To obtain the first set of measurements, processing system110drives a voltage waveform on conductive routing traces DL0, DL1, DL2, DL3and drives a constant voltage or a different voltage waveform on conductive routing traces DL4, DL5, DL6and DL7. This will create changing voltage gradients on the drive electrodes from left to right along axis201. For example, the voltage gradient from left to right on drive electrodes D0, D1, D2and D3might decrease, while the voltage gradient from left to right on the drive electrodes D4, D5, D6and D7might increase. In this embodiment, the changes in voltage gradient along each of the two sets of drive electrodes are opposite in sign because the current flow through the two sets of drive electrodes will be opposite in direction. The changes in voltage gradient generate first sense signals on each sense electrode, which can be measured by processing system110. Next, processing system110drives the same two groups of conductive routing traces (DL0, DL1, DL2, DL3and DL4, DL5, DL6and DL7) with differing voltage changes, generating second sense signals on each sense electrode, which can also be measured by processing system110. Since the changes in voltage gradient are known for each drive electrode, position information for an input object can be determined as described above with reference toFIG. 3A(and with further reference toFIGS. 2A and 2B).

With the first set of measurements described above, and in relation toFIG. 8, sense electrode S3lies along a boundary between two sets of drive electrodes having changing voltage gradients of opposite sign. An input object in this area may not be reliably detected because the effects of the opposing changes in voltage gradient will tend to cancel. To reliably detect input objects in this area, the boundary between opposing changes in voltage gradient can be shifted by taking a second set of measurements with a different grouping of drive electrodes. For example, conductive routing traces DL0, DL1, DL6, DL7may be driven with one voltage waveform, and conductive routing traces DL2, DL3, DL4, DL5may be driven, with a constant voltage or a second voltage waveform. This grouping of conductive routing traces creates voltage gradient boundaries along sense electrodes S1and S5. Since sense electrode S3no longer lies along a voltage gradient boundary, an input object near sense electrode S3can be reliably detected. In other embodiments, the conductive routing traces can be driven in other groupings. In yet other embodiments, the groupings may have differing numbers of conductive routing traces.

In another embodiment, a measurement acquired by processing system110with all drive electrodes driven with a common voltage waveform may be used for both detection of the presence of an input object and for determination of the position of the input object along axis202. Once the position of the input object along axis202is known, then the drive electrodes can be grouped so that there is no voltage gradient boundary near the input object, and the position of the input object along axis201can be determined with a single set of measurements.

In other embodiments, the voltage gradient boundary may be shifted across sensor108J. For example, in one embodiment the voltage gradient boundary may be cyclically shifted from sense electrode S0to sense electrode S6. In this case, the first grouping of conductive routing traces comprises a first group consisting of DL0and a second group consisting of DL1-DL7, thereby placing the voltage gradient boundary along sense electrode S0. To cyclically shift the voltage gradient boundary through sensor108J, the second grouping comprises a first group consisting of DL0, DL1and a second group consisting of DL2-DL7, thereby placing the voltage gradient boundary along sense electrode S1. The shifting of the groupings continues through a seventh grouping, where the seventh grouping comprises a first group consisting of DL0-DL6and a second group consisting of DL7, thereby placing the voltage gradient boundary along sense electrode S6. In another embodiment, the voltage gradient boundary may be cyclically shifted in the opposite direction from sense electrode S6to sense electrode S0. Further, other methods of cyclically shifting the voltage gradient boundary through sensor108J are also possible. By shifting the voltage gradient boundary using any of the above described methods, input objects can be reliably detected at any location on the sensor.

Turning now toFIG. 7B, a top view of a sensor108K is illustrated, according to another embodiment. Sensor108K represents an example of a sensor108, composed in input device100ofFIG. 1. As in the embodiment ofFIG. 7A, the right ends of each drive electrode of sensor108K are electrically coupled together. However, conductive element730is replaced with conductive element740, comprising a plurality of conductive traces.

FIG. 7Cillustrates a top view of a sensor108L, according to another embodiment. Sensor108L represents an example of a sensor108, composed in input device100ofFIG. 1. As in the embodiment ofFIG. 7A, the right ends of each drive electrode of sensor108L are electrically coupled together. However, conductive element730ofFIG. 7Ais replaced with conductive element750inFIG. 7C. Conductive element750may be constructed from the same material as drive electrodes D0-D7or from a different material. In any case, if conductive element750has significant resistivity, it will create voltage drops between the right ends of the drive electrodes when they are driven as described above. Based on the known geometry and resistivity of the drive electrodes and conductive element750, these voltage drops can be calculated using well-known circuit theory. Based on the calculated voltage drops, the perturbations in the voltage gradient changes due the resistance of conductive element750can be computed, and the desired positional information for input objects can still be easily determined. If the resistivity of the drive electrodes and conductive element750is not known in advance, then the voltage drops can be measured directly.

It is appreciated, that the above embodiments are meant to be non-limiting and that in other embodiments, alternate sequences of driving sensor electrodes may be used with sensor108J. Further, in various embodiments, there may be more than two groups of drive electrodes during operation. In other embodiments, a drive electrode can be absent from the groups in a grouping. In yet further embodiments, the drive electrodes within the groups of a grouping may be determined using a random or pseudo random method.

EXAMPLE METHODS OF OPERATION

The following discussion sets forth in detail example methods of operation of embodiments of the present invention. With reference toFIGS. 9A and 9B, flow diagrams900A and900B illustrate example procedures used by various embodiments. Flow diagrams900A and900B include some procedures that, in various embodiments, can be carried out by a processor under the control of computer-readable and computer-executable instructions as described above. In this fashion, all or part of flow diagrams900A and900B can be implemented using a computer or processing system, such as processing system110, in various embodiments. Although specific procedures are disclosed in flow diagrams900A and900B, such procedures are examples. That is, some embodiments are well suited to performing various other procedures or variations of the procedures recited in flow diagrams900A and900B and described below. Likewise, in some embodiments, the procedures in flow diagrams900A and900B (along with those described below) may be performed in an order different than presented and/or not all of the procedures described in flow diagrams900A and900B may be performed.

FIGS. 9A and 9Billustrate flow diagrams for some example methods of position sensing, according to various embodiments of the present invention. Flow diagrams900A and900B also describe methods of using input device100and processing system110with one or more of the sensors108that are described herein, according to various embodiments. Procedures of flow diagrams900A and900B are described below, with reference to elements ofFIGS. 1-8.

At910of flow diagram900A, first and second ends of a drive electrode are electrically driven to cause a change in a voltage gradient along a length of the drive electrode, thus generating a first electrical signal in a sense electrode. In some embodiments, the first end is driven with a varying voltage, while the second end is held at a constant voltage or driven with a different varying voltage. In some embodiments, the varying voltages may be different in amplitude or polarity. With reference to sensor108E inFIG. 3A, in one embodiment, flow diagram step910can comprise processing system110driving the right end of D1with a voltage waveform and driving the left end of D1with a different voltage waveform or a constant voltage. Techniques for accomplishing this have been described with reference at least toFIGS. 1-8. Further, the methods described above generate a first electrical signal in a sense electrode.

At920of flow diagram900A, in some embodiments, a first measurement of the first electrical signal is acquired. In some embodiments, processing system110acquires this measurement. Following the previous example centered on sensor108E, processing system110can acquire the first measurement from sense electrode S1in the manner previously described herein.

At930of flow diagram900A, in some embodiments positional information is determined along the length of the first drive electrode based upon the first measurement. The positional information is related to an input object. Following the previous example that is centered on sensor108E, in some embodiments processing system110determines an X-position along the length of drive electrode D1in the manner described in conjunction with one or more of Equations 1-11. Other techniques for determining such positional information have also been discussed herein, and in the interest of brevity and clarity, reference is made thereto. In some embodiments, processing system110can determine positional information in two dimensions, at least partially based upon the first measurement, the positional information again being related to an input object. Determination of two-dimensional position information has been previously described with reference toFIG. 3A(and with further reference toFIGS. 2A and 2B).

Referring now to flow diagram900B, flow diagram900B comprises910and920of flow diagram900A and as such,910and920are described above in relation toFIG. 9A. At940of flow diagram9006, in some embodiments the method further comprises electrically driving at least one of the first and second ends of the drive electrode to generate a second electrical signal in the sense electrode. In some embodiments, one end is driven with a voltage waveform while the other end is electrically floating (i.e. at a high impendence). In other embodiments, one end is held at a constant voltage, while the other end is driven with a voltage waveform. In yet other embodiments, the first end is driven with a voltage waveform and the second end is driven with a different voltage waveform. It is appreciated that step940of flow diagram900B might not cause a change in the voltage gradient along the length of the drive electrode, or it may cause a different change in the voltage gradient from the change in voltage gradient caused by step910of flow diagram9006.

With continued reference toFIG. 9B, at950of flow diagram900B, in some embodiments a second measurement is acquired, the second measurement being of the second electrical signal. In some embodiments, processing system110measures the second electrical signal in the manner previously described herein.

At960of flow diagram900B, in some embodiments positional information along the length of the drive electrode is determined based upon the first and second measurements. The positional information is related to an input object. Following the previous example that is centered on sensor108E, in some embodiments processing system110determines an X-position along the length of drive electrode D1in the manner described in conjunction with one or more of Equations 1-11. Other techniques for determining such positional information have also been discussed herein, and in the interest of brevity and clarity, reference is made thereto. In some embodiments, processing system110can determine positional information in two dimensions, at least partially based upon the first and second measurements, the positional information again being related to an input object. Determination of two-dimensional position information has been previously described with reference toFIG. 3A(and with further reference toFIGS. 2A and 2B).

For matters of convenience only, in any of the previous descriptions a first drive electrode, a second drive electrode, and a first sense electrode may be referred to as drive electrode D0, drive electrode D1, and sense electrode S0, respectively. Further, a plurality of drive electrodes, a plurality of sense electrodes, and a plurality of conductive routing traces may be referred to as drive electrodes D0-D5, sense electrodes S0-S4, and conductive routing traces DL0-DL5or DR0-DR5, respectively. It is understood that in some embodiments the plurality of drive electrodes, plurality of sense electrodes and plurality of conductive routing traces may comprise more or fewer drive electrodes, sense electrodes, and conductive routing traces, respectively. In the preceding embodiments, where two drive electrodes are described, the terms “first drive electrode” and “second drive electrode” may refer to any two separate drive electrodes. Furthermore, where more than one sense electrode is described, the term “first sense electrode” may refer to any sense electrode.

The foregoing descriptions of specific embodiments have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the presented technology to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the presented technology and its practical application, to thereby enable others skilled in the art to best utilize the presented technology and various embodiments with various modifications as are suited to the particular use contemplated.