Capacitive sensing apparatus

Abstract

Described is a capacitive sensing apparatus for sensing an object touching or in proximity of the capacitive sensing apparatus and for sensing relative displacement of at least a part of the capacitive sensing apparatus. The capacitive sensing apparatus includes: a driver electrode array. The driver electrode array comprises a plurality of electrodes spaced apart from one another by a spacing distance in a direction perpendicular to a first direction. The spacing distance is set in dependence on the distance between the driver electrode array and the first receiver electrode array and / or at least one second receiver electrode in the first direction, such that the degree of crosstalk between measurements of the mutual capacitive coupling between the first receiver electrode array and the driver electrode array and measurements of the mutual capacitive coupling between the at least one second receiver electrode and the driver electrode array is such that the measurements of the mutual capacitive coupling between the first receiver electrode array and the driver electrode array are substantially independent of displacements of the at least a part of the driver electrode array relative to the at least one second receiver electrode and measurements of the mutual capacitive coupling between the at least one second receiver electrode and the driver electrode array are substantially independent of objects touching or in proximity of the touch- sensitive surface. Also described is a method for sensing.

Description

[0001] TITLE OF THE INVENTION

[0002] CAPACITIVE SENSING APPARATUS

[0003] BACKGROUND OF THE INVENTION

[0004] The present invention relates to a capacitive sensing apparatus, and in particular a capacitive sensing apparatus that provides combined touch and displacement sensing using capacitive sensing techniques.

[0005] Capacitive sensing techniques have become widespread for providing touch-sensitive inputs, for example in computer tablets, mobile phones, and in many other applications. Touch sensitive input devices are generally perceived to be more aesthetically pleasing than input devices that are based on mechanical switches. Nonetheless, the present inventors have recognised there are still situations in which a user-interface that is responsive to mechanical input may be desired. In particular, the inventors have recognised there are situations in which there is a desire to measure the physical displacement of a displacement element, for example to provide the equivalent of a "click" when navigating a cursor across a display screen using a touch sensor. Furthermore, the inventors have recognised it can be desirable to provide such functionality using capacitive sensing techniques rather than mechanical switching techniques. Not only can capacitive sensing techniques provide for more reliable sensors (as they are less prone to mechanical wear), there may be situations in which displacement sensing is desired in conjunction with other sensors based on capacitive sensing (for example to measure the displacement of a capacitive touch screen), and so it can be convenient to adopt the same sensing technologies for both touch position and displacement sensing aspects.

[0006] Such combined capacitive touch and displacement sensors often comprise a capacitive touch sensor element and a separate displacement sensor element. While this arrangement provides each of the abovementioned capacitive touch and capacitive displacement sensing, the combined capacitive touch and displacement sensors can be considered expensive and complex to manufacture and are often bulkier due to the presence of separate sensor elements. Such sensors may not be considered suitable for all applications, particularly those where there is a desire to minimise the thickness of such sensors (e.g., such as on thin screen displays or the like).

[0007] There is therefore a desire for apparatus and methods that can help to address these kinds of issues.SUMMARY OF THE INVENTION

[0008] According to a first aspect of certain embodiments there is provided a capacitive sensing apparatus for sensing an object touching or in proximity of the capacitive sensing apparatus and for sensing relative displacement of at least a part of the capacitive sensing apparatus. The capacitive sensing apparatus includes: a first receiver electrode array, the first receiver electrode array defining a touch-sensitive surface; a driver electrode array provided in a stacked arrangement with the first receiver electrode array in a first direction and separated by electrically insulating material; at least one second receiver electrode provided in a stacked arrangement with the driver electrode array in the first direction such that at least a part of the driver electrode array is capable of moving in a direction parallel to the first direction toward the at least one second receiver electrode upon application of a displacement load to the touch-sensitive surface; touch capacitance measurement circuitry configured to receive signals from the first receiver electrode array indicative of the mutual capacitive coupling between the first receiver electrode array and the driver electrode array and determine at least the presence of an object touching or in proximity of the touch-sensitive surface; and displacement capacitance measurement circuitry configured to receive signals from the at least one second receiver electrode indicative of the mutual capacitive coupling between the at least one second receiver electrode and the driver electrode array and determine a relative displacement between the at least a part of the driver electrode array and the at least one second receiver electrode. The driver electrode array comprises a plurality of electrodes spaced apart from one another by a spacing distance in a direction perpendicular to the first direction, wherein at least one of the plurality of electrodes is configured to receive a drive signal in use. The spacing distance is set in dependence on the distance between the driver electrode array and the first receiver electrode array and / or at least one second receiver electrode in the first direction, such that the degree of crosstalk between measurements of the mutual capacitive coupling between the first receiver electrode array and the driver electrode array and measurements of the mutual capacitive coupling between the at least one second receiver electrode and the driver electrode array is such that the measurements of the mutual capacitive coupling between the first receiver electrode array and the driver electrode array are substantially independent of displacements of the at least a part of the driver electrode array relative to the at least one second receiver electrode and measurements of the mutual capacitive coupling between the at least one second receiver electrode and the driver electrode array are substantially independent of objects touching or in proximity of the touch-sensitive surface.

[0009] According to a second aspect of certain embodiments there is provided a method for sensing an object touching or in proximity of a capacitive sensing apparatus of the first aspect and / orfor sensing relative displacement of at least a part of the capacitive sensing apparatus of the first aspect. The method includes applying a drive signal to the driver electrode array; receiving one or more signals from the first receiver electrode array and determining at least the presence of an object touching or in proximity of the touch-sensitive surface on the basis of the received one or more signals from the first receiver electrode array; and / or receiving one or more signals from the at least one second receiver electrode and determining a relative displacement between the at least a part of the driver electrode array and the at least one second receiver electrode on the basis of the received one or more signals from the at least one second electrode.

[0010] It will be appreciated that features and aspects of the invention described above in relation to the first and other aspects of the invention are equally applicable to, and may be combined with, embodiments of the invention according to other aspects of the invention as appropriate, and not just in the specific combinations described above.

[0011] BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The invention is now described by way of example only with reference to the following drawings in which:

[0013] Figure 1 schematically represents a capacitive sensor part and controller part of a capacitive sensing apparatus according to certain embodiments of the invention;

[0014] Figure 2 schematically shows, in cross-section, a portion of the capacitive sensing apparatus of Figure 1 in a non-displaced state;

[0015] Figure 3 schematically shows, in cross-section, a portion of the capacitive sensing apparatus of Figure 1 in a displaced state;

[0016] Figure 4 schematically shows, in plan view, an insulating substrate of the capacitive sensing apparatus of Figure 1 and a plurality of driver electrodes forming a driver electrode array provided on a surface of the insulating substrate in accordance with certain embodiments of the invention;

[0017] Figure 5 schematically shows a magnified portion of the insulating substrate and driver electrode array of Figure 4 to further explain some principles of the present disclosure;

[0018] Figure 6 highly schematically represents a part of a configuration of a driver electrode array to explain other aspects of the present disclosure;

[0019] Figure 7 is a flow chart explaining an example method of operating a capacitive sensing apparatus of Figure 1 in order to obtain measurements of the capacitive couplings betweenthe driver electrode array and a first receiver electrode array and between the driver electrode array and a second receiver electrode array using a time division approach in accordance with a first implementation; and

[0020] Figure 8 is a flow chart explaining an example method of operating a capacitive sensing apparatus of Figure 1 in order to obtain measurements of the capacitive couplings between the driver electrode array and a first receiver electrode array and between the driver electrode array and a second receiver electrode array using a simultaneous approach in accordance with a second implementation.

[0021] DETAILED DESCRIPTION

[0022] Aspects and features of certain examples and embodiments of the present invention are discussed I described herein. Some aspects and features of certain examples and embodiments may be implemented conventionally and these are not discussed I described in detail in the interests of brevity. It will thus be appreciated that aspects and features of apparatus and methods discussed herein which are not described in detail may be implemented in accordance with any conventional techniques for implementing such aspects and features.

[0023] Figures 1, 2 and 3 schematically represent various aspects of a capacitive sensing apparatus 1 in accordance with certain embodiments of the invention.

[0024] Overall the capacitive sensing apparatus 1 comprises two main functional parts, namely a sensor part 6, comprising a capacitive sensor element 3 that is mounted with respect to a frame element 2 and associated components used for capacitively measuring displacements associated with the capacitive sensor element 3, or parts thereof, relative to the frame element 2 and objects (e.g., a human finger) touching or in the vicinity the capacitive sensor element 3, and a controller part 4 (or control circuitry) comprising displacement capacitance measurement circuitry 4A and touch capacitance measurement circuitry 4B for measuring capacitances indicative of displacements and touches applied to the sensor part 6 respectively, and processor circuitry 4C for processing the obtained capacitance measurements.

[0025] The capacitive sensing apparatus 1 is operable to measure both a displacement associated with the capacitive sensor element 3 and the presence of an object over I touching the capacitive sensor element 3 using capacitive sensing techniques. As will be described in more detail below, the capacitive sensing apparatus 1 according to the present disclosure utilises a single driver electrode array to provide the drive signal for both the touch sensing functionality (i.e., whether an object is over or touches the capacitive sensor element 3) andthe displacement sensing functionality (i.e. , the displacement associated with the capacitive sensor element 3 towards or away from the frame element 2). In this way, the capacitive sensing apparatus 1 of the present disclosure avoids the necessity to implement separate driver electrode arrays for providing the touch sensing functionality and for providing the displacement sensing functionality. This can help reduce manufacturing costs and complexities. Moreover, as will be described in more detail below, by suitably configuring the driver electrode array, further reduction in components can be achieved while not exceeding an acceptable level of noise within the obtained signals from the capacitive sensor element 3.

[0026] Figure 1 schematically represents the sensor part 6 in plan view and the controller part 4 in highly schematic form (i.e. as a functional block). Figures 2 and 3 respectively show portions of the sensor part 6 of the capacitive sensing apparatus 1 in cross-section (taken on the line A-A represented in Figure 1), with Figure 2 showing the capacitive sensor element 3 in a non-displaced (rest) state and Figure 3 showing the capacitive sensor element 3 in a displaced state. Figures 2 and 3 show the capacitive sensor element 3 schematically and not to any particular scale.

[0027] The sensor part 6 comprises a capacitive sensor element 3 that is mounted with respect to a frame element 2.

[0028] The frame element 2 acts as a base on which the capacitive sensor element 3 is provided, such that together the frame element 2 and capacitive sensor element 3 form the sensor part 6. That is, the frame element 2 provides a structural support for the capacitive sensor element 3 and will typically be connected to, or comprise an integral part of, an apparatus in which the capacitive sensing apparatus 1 is provided. The frame element 2 may comprise any suitable structural material, for example it may be formed from metal or plastic. The frame element 2 in this example defines a recess I opening into which the capacitive sensor element 3 is received therein, such that the frame element 2 additionally extends around the perimeter of the capacitive sensor element 3. However, in other implementations, the capacitive sensor element 3 may be placed on a planar surface and protrude from the frame element 2.

[0029] The capacitive sensor element 3 itself is formed so as to allow for the measuring of both a displacement of at least a part of the capacitive sensor element 3 and the presence of an object over I touching the capacitive sensor element 3. The capacitive sensor element 3 in this example is in the form of a planar rectangle, but other shapes may be used as desired and depending upon the application at hand. The size of the capacitive sensor element 3 may also be chosen according to the implementation at hand to provide the desired areaover which sensing is to be provided. Purely for the sake of a specific example, it will be assumed here the capacitive sensor element 3 has a size of around 10 cm (width) x 5 cm (height) x 0.2 cm (thickness), which may be suitable for a laptop trackpad, for example. The capacitive sensor element 3 may be transparent or opaque according to the application at hand. For example, in some implementations a display screen or backlight may be provided below the sensor part 6 or between the frame element 2 and the capacitive sensor element 3. In this case the capacitive sensor element 3 (and any parts of the frame element 2 overlying the display screen) should be transparent, at least to some extent, to allow a user to see the display screen I light through the sensor part 6. In other cases, such as for a laptop trackpad, for example, there may be a desire from a design perspective to hide what is behind the capacitive sensor element 3 or within the capacitive sensor element 3 (for example because there is internal wiring or structural elements of an apparatus in which the sensor part 6 is mounted which are not intended to be visible to the user for aesthetic reasons). In such examples, the capacitive sensor element 3 and I or frame element 2 may be opaque.

[0030] The capacitive sensor element 3 comprises a cover 30, a first receiver electrode array 31 comprising a plurality of first receiver electrodes, an insulating substrate 32, a driver electrode array 33 comprising a plurality of driver electrodes, a compressible substrate 34, and at least one second receiver electrode 35 (which in the present example is a second receiver electrode array 35 comprising a plurality of second receiver electrodes). As seen in Figures 2 and 3, these components of the capacitive sensor element 3 are provided in a stacked arrangement in the Z-direction (see Figure 2 for the frame of reference), and specifically in the order listed starting from the cover 30 to the second receiver electrode array 35. The Z-direction may alternatively be referred to as the stacking direction herein, i.e., a direction in which the various layers constituting the capacitive sensor element 3 are stacked. In addition, while Figures 1, 2 and 3 show the capacitive sensor element 3 being substantially flat, it should be understood that the capacitive sensor element 3 (and in particular the frame element 2) may be curved in some implementations, and hence the stacking direction may also be defined relative to this curvature (if present). The dimensions and distances between the various stacked layers of the capacitive sensor element 3 are exaggerated for clarity in Figures 2 and 3. In practice, the various stacked layers of the capacitive sensor element 3 may be laminated or otherwise attached to one another such that there is no or a relatively minimal spacing between the stacked layers.

[0031] The cover 30 comprises a substrate, such as a dielectric substrate, e.g. formed from glass or plastic. The cover 30 may be on the order of 0.1 mm to 3 mm, although other thicknesses are contemplated. The cover 30 is, or forms part of, the surface of the capacitive sensingapparatus 1 that the user interacts with, and thus can be considered to provide a sensing or interaction surface, as well as acting to protect the other parts of the capacitive sensor element 3. When reference is made to a user interacting with the cover 30 or more generally the capacitive sensor element 3, it should be appreciated that interacting encompasses an object physically contacting the interaction or sensing surface (e.g., a user’s finger physically touching the cover 30), but also encompasses an object being in proximity of the capacitive sensor element 3 (e.g., a user’s finger hovering over the cover 30 within a certain detectable distance from the cover 30). The cover 30 may be formed of any material that is suitable for acting as this interface with the object. In the described implementation, the cover 30 is also formed from a material that exhibits some degree of flexibility, as will be described in more detail with respect to Figure 3, although it should be appreciated that this is not necessary and the cover 30 may instead be rigid in other implementations.

[0032] The insulating substrate 32 is formed from an electrically insulating material, for example such as glass, plastic or another insulating material. The insulating substrate 32 is similarly a planar rectangle, but may take other shapes depending on the implementation at hand. On a first surface of the insulating substrate 32, and in particular the surface facing the cover 30, the first receiver electrode array 31 is provided, while on a second, opposite surface of the insulating substrate 32 the driver electrode array 33 is provided. The first receiver electrode array 31 and the driver electrode array 33 may be laminated or otherwise formed on the insulating substrate 32. In some implementations, the insulating substrate 32 may be a printed circuit board, PCB. In some implementations, the insulating substrate 32 may be formed from a single substrate or a plurality of substrates, where the plurality of substrates may be laminated or otherwise attached together. The insulating substrate 32 acts as both as a supporting element for supporting the electrode arrays 31 , 33 and also as an electrical insulator ensuring that the first receiver electrode array 31 and the driver electrode array 33 do not make physical contact (and thus direct electrical connection) with each another. The insulating substrate 32 may be formed of any suitable material that provides both of these functions. In the described implementation, the insulating substrate 32 is also formed from a material that exhibits some degree of flexibility, as will be described in more detail with respect of Figure 3, but again in other implementations the insulating substrate 32 may be rigid.

[0033] The first receiver electrode array 31 comprises a plurality of electrically conductive electrodes. Additionally, the driver electrode array 33 also comprises a plurality of electrically conductive electrodes. As will be explained in more detail below, the electrically conductive electrodes of the first receiver electrode array 31 and the electrically conductive electrodes of the driver electrode array 33 define a sensing surface (or touch sensitive surface) of thecapacitive sensor element 3 and are configured to sense an electrically conductive object that capacitively couples to the first receiver electrode array 31. In some implementations, a location of the electrically conductive object on the sensing surface of the capacitive sensor element 3 may also be able to be determined. The sensing surface of the capacitive sensor element 3 is schematically shown in Figure 1 by the dashed rectangle.

[0034] In the described example, the first receiver electrode array 31 comprises multiple vertically extending parallel electrodes, sometimes referred to as column electrodes, while the driver electrode array 33 comprises multiple laterally extending parallel electrodes, sometimes referred to as row electrodes. To clarify the terminology, the row electrodes of the driver electrode array 33 are aligned parallel to the X-direction and the column electrodes of the first receiver electrode array 31 are aligned parallel to the Y-direction (see the Cartesian coordinates of Figures 1 and 2 for reference). Thus, the different laterally extending electrodes allow the position of an electrically conductive object to be determined at different positions along the Y-direction while the different parallel extending electrodes allow the position of a conductive object to be determined at different positions along the X-direction. It will however be appreciated these terms are simply used as a convenient way of distinguishing the groups of electrodes extending in the different directions. In particular, the terms are not intended to indicate any specific electrode orientation. In general the term "row" will be used to refer to electrodes extending in a horizontal direction for the orientations represented in the figures while the terms "column" will be used to refer to electrodes extending in a vertical direction in the orientations represented in the figures.

[0035] In the described implementation, the conductive electrodes of the first receiver electrode array 31 and the conductive electrodes of the driver electrode array 33 are arranged on an orthogonal grid, with the vertically-extending parallel electrodes of the first receiver electrode array 31 on one side (the first side) of the insulating substrate 32 and the laterally-extending parallel electrodes of the driver electrode array 33 on the opposite (second) side of the insulating substrate 32, and oriented at substantially 90° to the electrodes of the first receiver electrode array 31. However, it should be understood that in other implementations, the electrodes may be oriented differently, for example at a different angle (e.g., 30°) relative to one another. In the described example, each of the electrodes of the first receiver electrode array 31 and the driver electrode array 33 have what may be referred to as a “bar” structure, or more accurately, a cuboidal structure. Such structures have a length, a perpendicular width and a height or thickness. Typically, the length is significantly greater than the width and height of the electrodes. In such “bar” structures, the width and height of the electrodes is substantially uniform along the length of the electrode. However, in some implementations,each electrode may have a more detailed structure than the simple "bar" structures, but the operating principles are broadly the same.

[0036] The first receiver electrodes of the first receiver electrode array 31 are provided spaced apart from one another (as seen in Figures 2 and 3, for example) on the surface of the insulating substrate 32. In the described example, the “bar” structures of the first receiver electrodes are arranged such that the lengths thereof are parallel with the X-axis direction, and it can be seen that the first receiver electrodes each have a width in the Y-axis direction and are spaced apart from one another in the Y-axis direction. The width and spacing of the first receiver electrodes of the first receiver electrode array 31 are not particularly limited in accordance with the principles of the present disclosure, and suitable widths and spacings may be chosen as appropriate. Typically, the width and spacing will have an influence on the sensitivity and / or spatial resolution at which touches or objects adjacent the sensing surface can be sensed by the touch-sensitive apparatus 1. By way of an example, the width of the first receiver electrodes of the first receiver electrode array 31 may be between 0.1 mm to 1.5 mm, while the spacing may be in the range of 3 mm to 10 mm.

[0037] In accordance with aspects of the present disclosure, and as will be explained in more detail below, in particular with reference to Figure 4, the driver electrodes of the driver electrode array 33 are spaced apart from one another by a spacing distance, S. That is, the driver electrodes of the driver electrode array 33 are arranged on the insulating substrate 32 such that, in a direction that is perpendicular to the Z-axis or stacking direction, the driver electrodes are arranged such that there exists a space or gap between adjacent driver electrodes. In the described implementation, where the first receiver electrodes of the first receiver electrode array 31 and the driver electrodes of the driver electrode array 33 are shown as “bar” structures and are orientated at 90° to each other, the direction along which the driver electrodes are spaced is parallel to the length of the first receiver electrodes of the first receiver electrode array 31. In the described implementation, where the driver electrodes of the driver electrode array 33 are shown as “bar” structures that are orientated parallel to each other in the length direction, the spacing distance, S, is constant along the length of adjacent driver electrodes.

[0038] The electrodes of the first receiver electrode array 31 and the driver electrode array 33 are made of an electrically conductive material, such as copper or Indium Tin Oxide (ITO). The nature of the various materials used depends on the desired characteristics of the capacitive sensing apparatus 1. For example, the capacitive sensor element 3 may need to be transparent for use with an underlying display screen or source of illumination (such as one or more LEDs), in which case ITO electrodes and a plastic substrate may be employed.Alternatively, the capacitive sensor element 3 may be opaque, and hence can use lower cost copper electrodes and an epoxy-glass-fibre substrate (e.g. FR4). Note that it is not necessary for any electrically conductive object to make direct galvanic connection to the electrodes of the first receiver electrode array 31 and / or driver electrode array 33 in order to be sensed.

[0039] It should be appreciated that while Figures 2 and 3 show the first receiver electrode array 31 position on one side of the insulating substrate 32 and the driver electrode array 32 positioned on the other side of the insulating substrate 32, in other implementations, the first receiver electrode array 31 and / or the driver electrode array 33 may be embedded within the insulating substrate 32 (e.g., which may be formed through moulding techniques or the like). The exact configuration is not significant for the principles of the present disclosure, but what is significant is the provision of insulating material between, and hence separating, the first receiver electrode array 31 and the driver electrode array 33. Further, in implementations where the first receiver electrode array 31 is embedded within the insulating substrate 32, the cover 30 may be omitted with the exposed part of the insulating substrate 32 performing the function of the cover 30.

[0040] The capacitive sensor element 3 further comprises a compressible substrate 34 which is positioned between the driver electrode array 33 and the at least one second receiver electrode 35 (or second receiver electrode array 35, as will be used herein). The compressible substrate 34 acts both to separate the driver electrode array 33 from the second receiver electrode array 35 to prevent physical contact thereof, and to provide compression or deformation in response to application of a displacement load (such as the load of a user’s finger or a stylus pressing onto the cover 30). The compressible substrate 34 may be formed from any suitable material to provide a deformation, in the Z-direction or stacking direction, on the order of 10 pm to 500 pm under application of the displacement load. For example, the compressible substrate 34 may be formed polyurethane or silicone, or other suitable materials. The compressible substrate 34 may be at least 100 pm thick, and in some implementations, less than 1 mm thick. In some implementations, the compressible substrate 34 is between 100 pm to 500 pm thick. Additionally, the compressible substrate 34 may be electrically insulating or electrically conductive, but in the latter case, the capacitive sensor element 3 is further configured such that the compressible substrate 34 is galvanically isolated from the driver electrode array 33.

[0041] As shown in Figures 2 and 3, the second receiver electrode array 35 is provided between the compressible substrate 34 and the frame element 2. In this example, the second receiver electrode array 35 is provided on the frame element 2, such that the frame element 2 acts asa support for the second receiver electrode array 35. However, in other implementations, the capacitive sensor element 3 may comprise a further insulating substrate (not shown) on which, or within which, the second receiver electrode array 35 is provided (e.g., such as laminated on), with the further insulating substrate being arranged to couple to the frame element 2. This may be particularly suitable for applications where the capacitive sensor element 3 is to replace an existing capacitive sensor element, e.g., for replacement or retrofitting. The rear surface of frame element 2 and / or further insulating substrate, may be used as desired. For example, the controller part 4 and its wiring to the various electrode arrays described above may be mounted to rear surface of the frame element 2 and / or the further insulating substrate, if present. In some implementations, the further insulating substrate may be one substrate of a plurality of substrates making up a multi-layer circuit board.

[0042] The second receiver electrode array 35 together with the driver electrode array 33 is provided for the purposes of sensing displacements of at least a part of the driver electrode array 33 with respect to the second receiver electrode array 35 caused by application of a displacement load to the cover 30 I touch sensing surface of the capacitive sensing apparatus 1. In some implementations, the capacitive sensing apparatus 1 is configured to determine whether there is or has been displacement of at least a part of the driver electrode array 33 with respect to the second receiver electrode array (e.g., such as binary indication of displacement or no displacement). In other implementations, the capacitive sensing apparatus 1 is configured to determine the location, for example in the X-Y plane, of the displacement of at least a part of the driver electrode array 33 with respect to the second receiver electrode array 35.

[0043] The second receiver electrode array 35 may comprise one or more second receiver electrodes. The one or more second receiver electrodes are electrically conductive electrodes, and may be formed from the same materials as the conductive electrodes of the first receiver electrode array 31 and the driver electrode array 33, such as copper or Indium Tin Oxide (ITO). The nature of the various materials used depends on the desired characteristics of the capacitive sensing apparatus 1 , as discussed above.

[0044] The surface area of the frame element 2 in which the second receiver electrode array 35 is present, together with the areal extent of the driver electrode array 33, defines a displacement sensing area for the displacement sensing function. The conductive electrodes of the second receiver electrode array 35 are conductive traces arranged to occupy a proportionate amount of the sensing area I surface area of the frame element 2 (or further insulating substrate, if present) below the driver electrode array 33. For example, if there is asingle second receiver electrode, this single second receiver electrode is arranged to occupy around 100% of the displacement sensing area, or if there are two second receiver electrodes, each occupy approximately 50% of the displacement sensing area, etc. The smaller the proportion of the displacement sensing area that each electrode of the second receiver electrode array 35 occupies, the greater the spatial resolution for resolving the X-Y position of the displacement load applied to the capacitive sensing apparatus 1 using the capacitive measurement associated with the second receiver electrode array 35. It should be appreciated that the selected proportion of the displacement sensing area that is occupied by each of the discrete second receiver electrodes may be dependent on the application at hand.

[0045] Each of the second receiver electrodes of the second receiver electrode array 35 may take any suitable form. For example, in some implementations, the conductive electrodes may take a “bar” structure as discussed above in respect of the first receiver electrode array 31 and / or the driver electrode array 33. In the described example, the second receiver electrode array 35 comprises multiple vertically extending parallel electrodes, which are also arranged so as be broadly parallel with the conductive electrodes of the first receiver electrode array 31 (see e.g., Figure 2), and broadly perpendicular to the conductive electrodes of the driver electrode array 33. However, it should be appreciated that the second receiver electrodes may be arranged differently in other implementations. In the described implementation, ten multiple vertically extending parallel electrodes of the second receiver electrode array 35 are shown as discrete “bar” electrodes occupying a corresponding proportion of the total displacement sensing area (e.g., around 10% each, excluding the area between the discrete electrodes of the second receiver electrode array 35). In such implementations, the second receiver electrodes are typically formed as narrow stripes running at nominally 90° to the conductive electrodes of the drive electrode array 33.

[0046] In alternative configurations, it may be desirable to increase the area of extent of each second receiver electrode at the detriment of spatial resolution. This may be to help provide an improved signal to noise ratio in respect of the capacitance measurement relating to displacement sensing, and / or to reduce costs and complexity associated with the controller part 4 and / or the displacement capacitance measurement circuitry 4A. In such implementations, the conductive electrodes of the second receiver electrode array 35 may follow an “S-shaped” pathway or the like, whereby each conductive electrode comprises a series of parallel elongate sections with adjacent parallel elongate sections connected to one another via a curved or arced section. In this way, the areal extent of each conductive electrode of the second receiver electrode array 35 may be increased. Broadly, in such implementations, the second receiver electrodes are again typically formed as narrow stripesrunning at nominally 90° to the conductive electrodes of the drive electrode array 33 but now weaving back and forth to provide coverage of the corresponding proportion of the displacement sensing area. In some implementations, the discrete conductive electrodes may alternatively be provided as sheet or plate like elements providing coverage of the proportion of the displacement sensing area. However, this may not be optimal for the displacement capacitance measurement circuitry 4A, as this arrangement can cause the build-up of very large coupling capacitances. In such implementations, the displacement capacitance measurement circuitry 4A may be specifically adapted to handle such larger capacitances.

[0047] The capacitive sensing apparatus 1 is further provided with a controller part 4 (or control circuitry) comprising the displacement capacitance measurement circuitry 4A and the touch capacitance measurement circuitry 4B for measuring capacitances indicative of displacements and touches applied to the sensor part 6 respectively, along with processor circuitry 4C for processing the obtained capacitance measurements. In Figure 1, the displacement capacitance measurement circuitry 4A, the touch capacitance measurement circuitry 4B, and the processor circuitry 4C are shown highly schematically and as independent parts of the controller part 4. The displacement capacitance measurement circuitry 4A, the touch capacitance measurement circuitry 4B, and the processor circuitry 4C may each be provided by a (micro)controller, processor, ASIC or similar form of control chip. Although shown separately in Figure 1, in some implementations, the displacement capacitance measurement circuitry 4A, the touch capacitance measurement circuitry 4B, and the processor circuitry 4C may be provided by the same (micro)controller, processor, ASIC or similar form of control chip. Note also that the functionality provided by the displacement capacitance measurement circuitry 4A, the touch capacitance measurement circuitry 4B, and the processor circuitry 4C may be split across multiple circuit boards and I or across components which are not mounted to a PCB.

[0048] The displacement capacitance measurement circuitry 4A is configured to obtain measurements associated with the capacitive coupling between the driver electrode array 33 and the second receiver electrode array 35. When a user desires to press the cover 30, e.g., to perform a “click” function as described above, the cover 30 is the part of capacitive sensing apparatus 1 to which a load may be applied during normal use. The application of an example displacement load applied during use, e.g. corresponding to a user pressing a finger on the cover 30, is schematically shown in Figure 3 by the arrow labelled "LOAD". For ease of explanation, the side of the cover 30 to which the displacement load is applied in normal use may sometimes be referred to herein as the "upper" or "outer" side of the cover 30 (or similar terminology such as "top"), with the other side being referred to as "lower" or"inner" (or similar terminology, such as "bottom"). Thus, the surface of the cover 30 shown uppermost in the orientation of Figures 2 and 3 may sometimes be referred to as the upper I outer I top surface of the cover 30 or, more generally, the capacitive sensor element 3. Likewise, the lowermost surface of the cover 30 for the orientation of Figures 2 and 3 may sometimes be referred to as the bottom I lower I inner surface. Corresponding terms may similarly be used in respect of other parts of the capacitive sensing apparatus 1 , such as the various stacked layers described above, in accordance with the orientation shown in the relevant figures. However, it will be appreciated this terminology is used purely for convenience of explanation and is not intended to suggest a particular orientation of the capacitive sensing apparatus 1 should be adopted in normal use. For example, although in the orientation of Figures 2 and 3 the upper surface of the sensor part 6 is shown uppermost, the sensor part 6 could equally be used in a downward facing configuration, or facing outwards from a vertical surface, according to the implementation at hand. More generally, the capacitive sensing apparatus 1 may be incorporated in a portable device (such as a laptop, tablet computer or mobile telephone), and in that case the orientation in use will vary according to how a user happens to be holding the device.

[0049] As noted above, Figure 2 schematically represents the sensor part 6 in a rest state with no displacement load applied to the cover 30. In this example the gap between the upper surface of the second receiver electrode array 35 and a lower surface of the driver electrode array 33 is, as indicated in Figure 2, h. This gap, h, corresponds with the height of the compressible substrate 34 in its relaxed state.

[0050] Figure 3 schematically represents the sensor part 6 in a displaced state in which a displacement load is applied to the cover 30. The displacement load may, for example, be provided by a user's finger pressing on the outer surface of the cover 30 or by a user pressing a stylus on the outer surface of the cover 30. In the described example, the compressible substrate 34 is compressed under the action of the displacement load. This action causes parts of the capacitive sensor element 3, and in particular, at least a part of the driver electrode array 33 to move along a displacement direction towards the frame element 2 on which the second receiver electrode array 35 is arranged by an amount, d.

[0051] In the present example, the cover 30 and insulating substrate 32 are formed from flexible material. As shown in Figure 3, when the displacement load is applied to the top surface of the cover 30, the cover 30 flexes or deflects in the region local to the displacement load. This correspondingly causes the insulating substrate 32 to also flex or otherwise deflect in the region local to the displacement load, and consequently such deflection causes localised compression of the compressible substrate 34. By virtue of the fact that the driver electrodearray 33 is provided on (e.g., laminated on) the bottom surface of the insulating substrate 32, at least a part of the driver electrode array 33 moves towards the second receiver electrode array 35 by the amount, d, by virtue of the flexing of the insulating substrate 32 and the compressing of the compressible substrate 34 in response to the applied displacement load. The magnitude of the displacement, d, will be a function of the force (displacement load) applied and any resilience to compression and / or flexing of the cover 30, insulating substrate 32 and compressible substrate 34. Because the driver electrode array 33 is, at least in part, closer to the second receiver electrode array 35 in this situation, any capacitive coupling between the driver electrode array 33 and the second receiver electrode array 35 is changed (in proportion to at least the displacement, d) which can be sensed by the displacement capacitance measurement circuitry 4A.

[0052] In the implementation of Figure 3, the cover 30 and insulating substrate 32 are both formed from a flexible material and hence experience localised flexing or deflection in response to the applied displacement load. However, it should be appreciated that in other implementations, the cover 30 and / or insulating substrate 32 may be formed from rigid materials that do not experience localised flexing or deflection in response to the applied displacement load. In such implementations, the cover 30 and / or insulating substrate 32 may remain parallel to the frame element 2 when displaced (or potentially tilted depending on the exact location of the applied displacement load, i.e. the value of d may be different at different positions across the insulating substrate 32). In such examples, the cover 30 and / or insulating substrate 32 may be free to move with respect to parts of the frame element 2 (for example, as opposed to being attached at the edges thereof to the protruding part of the frame element 2 in which the capacitive sensor element 3 is located). In such implementations where the cover 30 and / or insulating substrate 32 are formed from a rigid material, the compressible substrate 34 may be more uniformly compressed when the displacement load is applied. This may result in a greater area of compression in the X-Y direction, but also a smaller degree of compression in the Z-direction. That is to say, for the same displacement load, the displacement, d, may be smaller when the cover 30 and / or insulating substrate 32 are formed from a rigid material. To compensate, in such implementations, the second receiver electrode array 35 may be provided with fewer discrete electrodes but with each electrode covering a relatively greater proportion of the displacement sensing area. Moreover, even if a greater number of second receiver electrodes are able to detect the displacement, d, with the required sensitivity, any spatial resolution gained by having a large number of discrete second receiver electrodes may be reduced by virtue of the non-localised compression of the compressible substrate 35. Accordingly, in such implementations where the cover 30 and / or insulating substrate 32 arerigid, it may be advantageous to provide a relatively lower number of second receiver electrodes in the second receiver electrode array 35.

[0053] The displacement capacitance measurement circuitry 4A is capable of capacitively detecting the displacement, d, of the compressible substrate 34 using the driver electrode array 33 and the second receiver electrode array 35 as will be explained herein. More particularly, the controller part 4 is configured to apply a drive signal to the driver electrode array 33 and cause the displacement capacitance measurement circuitry 4A to obtain a measurement of the mutual-capacitance between the driver electrode array 33 and the second receiver electrode array 35. In these implementations, the controller part 4, via suitable circuitry, is configured to cause a time-varying electrical stimulus (drive signal) to be applied to one or more of the conductive electrodes of the driver electrode array 33 that varies in time relative to system ground (or other reference potential) and to measure the extent to which the drive signal is capacitively coupled to the conductive electrode(s) of the second receiver electrode array 35. Any suitable drive signal may be used, such as a sinusoidal signal. Applying the drive signal to an electrode of the driver electrode array 33 causes an electric field to form around the driver electrode(s). The resulting electric field directly couples from the electrodes of the driver electrode array 33 to the electrodes of the second receiver electrode array 35. The magnitude of the mutual capacitive coupling between the driver electrode array 33 and the second receiver electrode array 35 depends, in part, on the separation between the different parts of the driver electrode array 33 and the second receiver electrode array 35. In some instances, the magnitude of the mutual capacitive coupling between the driver electrode array 33 and the second receiver electrode array 35 may also depend on the proximity of other conductive components. For example, if the frame element 2 is formed to be electrically conductive and grounded, which may well be the case in some implementations in order to reduce the influence of external noise, then the capacitive coupling between the driver electrode array 33 and the second receiver electrode array 35 may also depend on the distance between the driver electrode array 33 and the frame element 2. Thus, the mutual-capacitance between the driver electrode array 33 and the second receiver electrode array 35 changes when the driver electrode array 33 (or parts thereof) is brought toward the second receiver electrode array 35 and / or a grounded frame element 2 by virtue of the compression of the compressible substrate 34 under the application of a displacement load to the cover 30. Coupling the displacement capacitance measurement circuitry 4A to the conductive electrode(s) of the second receiver electrode array 35 allows for the displacement capacitance measurement circuitry 4A to measure the mutual capacitance between the driver electrode array 33 and the second receiver electrode array 35.The textbook "Capacitive Sensors: Design and Applications" by Larry K. Baxter, August 1996, Wiley-IEEE Press, ISBN: 978-0-7803-5351-0 [1] summarises some of the principles of conventional capacitive sensing techniques that may be used for measuring capacitance characteristics in accordance with various implementations.

[0054] The displacement capacitance measurement circuitry 4A is configured to sense the change in mutual capacitance resulting from a change in the relative distance between parts of the driver electrode array 33 and the second receiver electrode array 35. Accordingly, when a displacement load is applied to the cover 30, which causes compression of the compressible substrate 34 and part of the driver electrode array 33 to move towards the second receiver electrode array 35 and the frame element 2, the displacement capacitance measurement circuitry 4A is capable of outputting a measurement of the capacitance that is dependent on the displacement ‘d’ between the driver electrode array 33 and the second receiver electrode array 35.

[0055] The displacement capacitance measurement circuitry 4A outputs a measure of this capacitance to the processing circuitry 4C of the controller part 4. In some implementations, the processing circuitry 4C may be configured to determine an absolute value for a displacement, for example by converting an individual capacitance measurement (or average of several capacitance measurements) to a displacement ‘d’ based on a calibration function which relates capacitance measurements to displacements. The calibration function may, for example, be based on modelling or established in an initial setup procedure in accordance with conventional capacitance measurement techniques. In particular, a baseline value (corresponding to a measurement of the mutual capacitance characteristics between the driver electrode array 33 and the second receiver electrode array 35 when there is no displacement) may be established at various times, for example when the capacitive sensing apparatus 1 is initially turned on. The calibration function may then be used to convert differences in capacitance measurement from the baseline measurement to corresponding displacements ‘d’. In other implementations, the processing circuitry 4C may be configured to in effect provide a binary indication as to whether or not there has been a displacement greater than a threshold displacement. For example, the processing circuitry 4C may be configured to identify when there has been a change in measured mutual capacitance that is greater than a pre-defined trigger threshold, and to determine that this corresponds with a displacement by more than an amount corresponding to the pre-defined threshold displacement. An appropriate value for the pre-defined trigger threshold in any given implementation can be established empirically having regard to the extent of displacement which is desired to trigger a determination that displacement has occurred, and may be dynamically chosen to suit a given application.Accordingly, by configuring the capacitive sensor element 3 such that the distance between the driver electrode array 33 and the second receiver electrode array 35 is capable of changing (decreasing) in response to an applied displacement load to the cover 30 (or other external surface) of the capacitive sensor element 3, and by measuring the mutual capacitance between the driver electrode array 33 and the second receiver electrode array 35 resulting from an applied drive signal to the driver electrode array 33, the capacitive sensing apparatus 1 (in particular the controller part 4) is able to determine whether displacement has occurred, the magnitude of the displacement and / or the location of the displacement.

[0056] The touch capacitance measurement circuitry 4B is configured to obtain measurements associated with the capacitive coupling between the driver electrode array 33 and the first receiver electrode array 31 to determine the presence (and / or location) of an object adjacent or on the sensing surface of the capacitive sensor element 3.

[0057] In particular, the touch capacitance measurement circuitry 4B is configured to obtain measurements of the mutual capacitance(s) between conductive electrodes of the driver electrode array 33 and conductive electrodes of the first receiver electrode array 31. Similarly to the above, the controller part 4 is configured to apply a drive signal, sequentially or in parallel, to each of the conductive electrodes of the driver electrode array 33 and cause the touch capacitance measurement circuitry 4B to obtain a measurement of the mutualcapacitance between the driven electrodes of the driver electrode array 33 and coupled ones of receiver electrodes of the first receiver electrode array 31 that are coupled by virtue of their proximity to the driven electrodes. The area local to and centred on an intersection of a driver electrode of the driver electrode array 33 and a receiver electrode of the first receiver electrode array 31 is typically referred to as a “node”. Now, on application or approach of a conductive element such as a human finger, the generated electric field is partly diverted to the approaching or touching object. Because the conductive element acts to divert some of the electrical field, the amount of electric field coupled to the nearby receiver electrode of the first electrode array 31 decreases. The magnitude of a capacitance change is nominally proportional to the contact area of the object (although the change in capacitance does tend to saturate as the contact area increases beyond a certain size to completely cover the nodes directly under the object) and weakly proportional to the size of the touching body. The magnitude of the capacitance change also reduces as the distance between the first receiver electrode array 31 and the object increases.

[0058] Accordingly, coupling the touch capacitance measurement circuitry 4B to the conductive electrode(s) of the first receiver electrode array 31 allows for the touch capacitancemeasurement circuitry 4B to measure the mutual capacitance between the various driven electrodes of the driver electrode array 33 and the first receiver electrode array 31. Moreover, because each of the “nodes” corresponds to a particular X-Y position on the sensing surface of the capacitive sensor element 3, it is also possible to determine a location of the object based on determining which of the “nodes” experiences a change in capacitance. The touch capacitance measurement circuitry 4B is configured to sense the change in mutual capacitance resulting from the presence of a conductive object adjacent the first receiver electrode array 31. Accordingly, when an object is within a sufficient distance of the first receiver electrode array 31, the touch capacitance measurement circuitry 4B is capable of outputting a measurement of the capacitance that is dependent on the presence and / or location of the conductive object.

[0059] The touch capacitance measurement circuitry 4B outputs a measure of this capacitance to the processing circuitry 4C of the controller part 4. In some implementations, the processing circuitry 4C may be configured to determine an absolute value for the change in mutual capacitance caused by a conductive object, for example to determine the strength of a touch or the distance of an object from the sensing surface, by converting an individual capacitance measurement (or average of several capacitance measurements) to a corresponding measure of strength or distance based on a calibration function which relates capacitance measurements to strength or distance. The calibration function may, for example, be based on modelling or established in an initial setup procedure in accordance with conventional capacitance measurement techniques. In particular, a baseline value (corresponding to a measurement of the mutual capacitance characteristics between the driver electrode array 33 and the first receiver electrode array 31 when there is no object present in the vicinity of the first receiver electrode array 31) may be established at various times, for example when the capacitive sensing apparatus 1 is initially turned on. The calibration function may then be used to convert differences in capacitance measurement from the baseline measurement to corresponding strengths or distances. In other implementations, the processing circuitry 4C may be configured to in effect provide a binary indication as to whether or not an object is detected for any given “node” based on the change in mutual capacitance being greater than a threshold. For example, the processing circuitry 4C may be configured to identify when there has been a change in measured mutual capacitance that is greater than a pre-defined trigger threshold, and to determine that this corresponds with an object at or adjacent the “node” by more than an amount corresponding to the pre-defined trigger threshold. An appropriate value for the pre-defined trigger threshold in any given implementation can be established empirically having regard to the extent to which it is desired to trigger adetermination that an object is sensed, and may be dynamically chosen to suit a given application.

[0060] Accordingly, by configuring the capacitive sensor element 3 such that the driver electrode array 33 capacitively couples to conductive electrodes of the first receiver electrode array 31 , and by measuring the mutual capacitance between the electrodes of the driver electrode array 33 and the first receiver electrode array 31 resulting from an applied drive signal to the driver electrode array 33, the capacitive sensing apparatus 1 (in particular the controller part 4) is able to determine the presence of a conductive object adjacent or contacting the sensing surface and / or the location of the conductive object.

[0061] It should be appreciated from the above that the capacitive sensing apparatus 1, or more specifically the processing circuitry 4C, is capable of providing an output that corresponds to a displacement of the cover 30 I driver electrode array 33 and an output that corresponds to the presence of an object at or in the vicinity of the sensing surface of the cover 30. Broadly speaking, the processing circuitry 4C may be capable of providing either or both of these outputs as absolute values for displacements or extents of touches or as binary / ternary outputs which may be provided to an associated apparatus which the capacitive sensing apparatus 1 is provided in conjunction with (where the associated apparatus may utilise these outputs as appropriate depending on the application at hand).

[0062] In accordance with the principles of the present disclosure, the capacitive sensing apparatus 1 has a simplified construction that offers a cost effective and time efficient way to sense both the presence and / or position of an object and a displacement caused by an applied displacement load.

[0063] In particular, by suitably configuring the driver electrodes of the driver electrode array 33, and in particular the spacing distance between the drive electrodes of the driver electrode array 33, the capacitive coupling between the driver electrode array 33 and the first receiver electrode array 31 can be largely unaffected by the compression of the compressible substrate 34. For instance, when the compressible substrate 34 is compressed, the driver electrode array 33 (or a part thereof) moves closer to the frame element 2 I second receiver electrode array 35. If the driver electrode array 33 is not suitably configured, and in particular if the spacing distance is too large, then measurements of the mutual capacitive coupling between the first electrode array 31 and the driver electrode array 33 are influenced by displacements of at least a part of the driver electrode array 33 relative to the second receiver electrode array 35, and vice versa (i.e., measurements of the mutual capacitive coupling between the second receiver electrode array 35 and the driver electrode array 33 are influenced by objects touching or in proximity of the touch-sensitive surface). Forexample, when sensing a displacement (i.e., measuring the mutual capacitance between the driver electrode array 33 and the second receiver electrode array 35), if the spacing distance is too large between the driver electrodes in the driver electrode array 33, any electric field established between the second receiver electrode array 35 and the driven driver electrode(s) of the driver electrode array 33 can be influenced by (or interact with) objects adjacent or in the proximity of the touch-sensitive surface. Put another way, these objects can couple to the driver electrode array 33 by virtue of the larger spacing distance to such an extent that they influence mutual capacitance between the second receiver electrode array 35 and the driver electrode array 33 in a meaningful I detectable way, and hence it becomes difficult to establish whether the measured mutual capacitance is representative of displacement or of the presence of the object (or of both). A similar situation arises when measuring the mutual capacitance between the first receiver electrode array 31 and the driver electrode array 33, where due to the larger spacing distance, any displacement of the driver electrode array 33 can influence the mutual capacitance between the first receiver electrode array 31 and the driver electrode array 33 such that it becomes difficult to establish whether the measured mutual capacitance is representative of displacement or of the presence of the object (or of both). Furthermore, if the driver electrode array 33 is not suitably configured, and in particular if the spacing distance is too large, this can modulate any parasitic capacitive loading which this second receiver electrode array 35 may present to the driver electrode array 33 (potentially along with any additional circuitry or nearby grounded frame element 2, etc.). Hence, more generally, when the driver electrode array 33 is not suitably configured, capacitive loadings may lead to small but potentially significant changes in the capacitive couplings between the driver electrode array 33 and the first receiver electrode array 31 such that, it would become difficult, if not impossible, to determine if these changes in mutual capacitance as measured by the touch capacitance measurement circuitry 4B had been caused by a sensed conductive object or by a non-conductive object pressing on the cover 30. Equally, if the driver electrode array 33 is not suitably configured, conductive objects adjacent or contacting the cover 30 can influence the capacitive couplings between the driver electrode array 33 and the second receiver electrode array 35, thereby making it more difficult to accurately establish whether there is a displacement of the drive electrode array 33 corresponding to an applied displacement load or not.

[0064] In order to prevent or reduce this effect, the inventors have found that by configuring the driver electrode array 33 such that the spacing distance between adjacent electrodes is below a maximum value, the capacitive coupling between the driver electrode array 33 and the first receiver electrode array 31 can be largely unaffected by any displacements of thedriver electrode array 33 and the capacitive coupling between the driver electrode array 33 and the second receiver electrode array 35 can be largely unaffected by any conductive objects adjacent to or contacting the sensing surface of the capacitive sensor element 3. Hence, such a configuration allows the two sets of mutual capacitive measurements to remain substantially independent of each other, such that the presence of an object does not change or modulate displacement capacitance measurements and an applied displacement load does not modulate the object detection capacitance measurements.

[0065] Figure 4 schematically shows, in plan view, the bottom surface of the insulating substrate 32 of the capacitive sensor element 3 on which a plurality of driver electrodes, in particular twelve, of the driver electrode array 33 are arranged. Other features of the capacitive sensing apparatus 1 are omitted for the purposes of explaining the principles of the present disclosure.

[0066] In the example of Figure 4, the driver electrodes of the driver electrode array 33 have a “bar” structure, i.e., an elongated structure defining a length and a width W. Each of the driver electrodes are arranged parallel to one another and, in particular, such that their lengths are parallel to the X-axis. As discussed above, however, the structure and arrangement of the driver electrodes may be different in different implementations, and the driver electrodes need not be parallel to the X-axis or, in some implementations, even to one another.

[0067] The driver electrodes of the driver electrode array 33 are spaced apart from one another along a direction that is perpendicular to the Z-axis or staking direction. For example, in Figure 4, the driver electrodes are spaced apart in the width direction (or more generally a spacing direction). In other implementations, it should be appreciated that the driver electrodes may be spaced along a direction other than the width direction, provided that said direction is perpendicular to the Z-axis or stacking direction. In Figure 4, it can be seen that adjacent edges of two adjacent driver electrodes are spaced apart from one another by a gap or spacing distance, S.

[0068] In accordance with the principles of the present disclosure, the spacing distance, S, between adjacent driver electrodes is set such that the degree of crosstalk between measurements of the mutual capacitive coupling between the first electrode array 31 and the driver electrode array 33 and measurements of the mutual capacitive coupling between the second electrode array 35 and the driver electrode array 33 is below a certain level such that the measurements of the mutual capacitive coupling between the first receiver electrode array 31 and the driver electrode array 33 are (substantially) independent of displacements of at least a part of the driver electrode array 33 relative to the second receiver electrode array 35, and such that measurements of the mutual capacitive coupling between the second receiverelectrode array 35 and the driver electrode array 33 are (substantially) independent of objects touching or in proximity of the touch-sensitive surface.

[0069] The spacing distance, S, is set to be equal to or below a maximum value. That is, the distance between adjacent electrodes in the spacing distance can be any suitable value provided the distance is equal to or below the maximum value. This maximum value is dependent on the overall construction of the capacitive sensor element 3 and hence will vary in different implementations. However, the maximum value is dependent on the distance in the Z-axis or stacked direction of the capacitive sensor element 3 between the driver electrode array 33 and the first receiver electrode array 31 and / or the distance between the driver electrode array 33 and the second receiver electrode array 35 when the compressible substrate 34 is in the uncompressed or at rest state. In some implementations, the maximum value is set based on the smaller of the two distances between the driver electrode array 33 and the first receiver electrode array 31 and between the driver electrode array 33 and the second receiver electrode array 35. In principle, when the distance between the driver electrode array 33 and the first receiver electrode array 31 and / or between the driver electrode array 33 and the second receiver electrode array 35 increases, the maximum value for the spacing distance, S, between adjacent driver electrodes of the driver electrode array 33 can be set larger. Without wishing to be bound by theory, it has been found that with increasing distances the influence of any cross-coupling of the capacitive measurements is generally lower and hence the spacing distance, S, of the driver electrode array 33 can be made to be greater without compromising the ability to separate or isolate the mutual capacitive coupling between the first receiver electrode array 31 and the driver electrode array 33 (such that they are, substantially, independent of displacements of at least a part of the driver electrode array 33 relative to the second receiver electrode array 35), and measurements of the mutual capacitive coupling between the second receiver electrode array 35 and the driver electrode array 33 (such that they are, substantially, independent of objects touching or in proximity of the touch-sensitive surface).

[0070] In terms of what is meant by the degree of crosstalk between the two sets of capacitive measurements being such that the measurements of the mutual capacitive coupling between the first electrode array 31 and the driver electrode array 33 are (substantially) independent of displacements of the driver electrode array 33 relative to the second receiver electrode array 35 and measurements of the mutual capacitive coupling between the second receiver electrode array 35 and the driver electrode array 33 are (substantially) independent of objects touching or in proximity of the touch-sensitive surface, the degree of crosstalk should ideally be set such that it is less than 12 times, preferably less than 10 times, and more preferably less than 7 times than the measurement of interest. In other words, if themeasurement of the mutual capacitive coupling between the first electrode array 31 and the driver electrode array 33 (e.g., for sensing an object / touch at the sensing surface) is the measurement of interest, then any part of that measurement that is affected by the capacitive coupling between the driver electrode array 33 and the second receiver electrode array 35 is set to be 12, 10 or 7 times weaker (e.g., in amplitude) than the mutual capacitive coupling between the first electrode array 31 and the driver electrode array 33. Many factors may influence the capacitive couplings, such as the strength of the drive signal, the geometry of the first and second receiver electrode arrays 31, 35, etc. The maximum values of the spacing distance, S, for a given set of conditions can be found through modelling or empirically. For example, by obtaining a measurement of the capacitive coupling between the first receiver electrode array 31 and the driver electrode array 33 whilst modulating or compressing the compressible substrate 34 with a non-conductive object provides an indication of the degree of crosstalk in the capacitive coupling between the first receiver electrode array 31 and the driver electrode array 33. By changing the spacing distance, S, however, the Inventors have found that the degree of crosstalk can be reduced to the extent that the mutual capacitive coupling between the first electrode array 31 and the driver electrode array 33 is (substantially) independent of displacements of the driver electrode array 33 relative to the second receiver electrode array 35 and the mutual capacitive coupling between the second receiver electrode array 35 and the driver electrode array 33 is (substantially) independent of objects touching or in proximity of the touch-sensitive surface. With reference back to Figure 4, we can also define a pitch, P, at which the driver electrodes are spaced, which in this example is equal to the width, W, plus the spacing distance, S. The pitch, P, is the distance between centres or centre points of adjacent driver electrodes in the width direction (or more generally the spacing direction).

[0071] In the example of Figure 4, the driver electrodes of the driver electrode array 33 are provided with a uniform width, W, and are spaced at uniform spacing distance, S (and hence also are provided at a uniform pitch, P). In some implementations, the pitch, P, may be on the order of between 3 mm to 10 mm, although this may differ in different implementations. It should be appreciated that in other implementations, the different ones of the driver electrodes may have different widths, W, and / or be provided at different spacing distances, S. In such cases, the pitch, P, may vary between different pairs of adjacent electrodes, but in such a case, the pitch, P, can be broadly defined as the average of the widths, W, of the adjacent driver electrodes plus the spacing distance, S, therebetween.

[0072] As should be appreciated from the above, when the distances in the Z-axis or stacking direction between the driver electrode array 33 and the first receiver electrode array 31and / or the distance between the driver electrode array 33 and the second receiver electrode array 35 are relatively small, the maximum value of the spacing distance, S, is also set to be relatively small. This can mean that the driver electrodes of the driver electrode array 33 are configured in such a way as to occupy a large or significant proportion of an area within which the driver electrodes of the driver electrode array 33 are arranged. That is, the driver electrodes of the driver electrode array 33 is configured to be so-called “area-filling”, i.e., to occupy a large portion or substantially all of the area that is defined by the outermost perimeter of the driver electrode array 33 in its entirety. In particular, and as shown in Figure 4, the driver electrode array 33 is provided within a continuous area 33a that is defined by (or bound by) the outermost perimeter of the driver electrode array 33. This is shown in Figure 4 by the dashed rectangle that surrounds the outermost perimeter of the driver electrode array 33. In this regard, the outermost perimeter of the driver electrode array 33 is defined by the overall areal extent of the driver electrode array 33 in its entirety, including the driver electrodes and the spacings or gaps therebetween. Moreover, the outermost perimeter is contiguous with some of the outermost edges of the driver electrodes (e.g., the shorter edges of the driver electrodes and the two long edges of the outermost driver electrodes). The outermost perimeter defines a boundary or area that encompasses the gaps between adjacent driver electrodes as well as each of the plurality of driver electrodes.

[0073] The term “continuous area” refers to an area that is continuous, or in other words, is a single, discrete area. The term “continuous area” does not refer to a plurality of discrete areas that are otherwise not connected to one another or not contiguous with one another, i.e., sharing the same boarder. For example, the two areas occupied by each of two discrete driver electrodes and defined by the edges of said driver electrodes are not contiguous, as they are separated by a gap, and therefore do not constitute a “continuous area”. In addition, it should be appreciated that the “continuous area” has a normal that is parallel to the Z-axis direction (or more generally the stacking direction of the capacitive sensor element 3).

[0074] Hence, broadly speaking, the driver electrode array 33 in its entirety (which includes the driver electrodes and the spaces therebetween) is provided within a continuous area, the boundary of which is contiguous with at least the edges of the outermost driver electrodes of the driver electrode array 33. The continuous area 33a comprises the area of each of the driver electrodes of the driver electrode array 33 and the area of the spaces between the driver electrodes of the driver electrode array 33. That is, the summation of each of the areas of the individual driver electrodes and the summation of the areas of each of the gaps I spaces between the driver electrodes is equal to the area of the continuous area 33a.In accordance with an aspect of the present disclosure, when the distances in the Z-axis or stacking direction between the driver electrode array 33 and the first receiver electrode array 31 and / or the distance between the driver electrode array 33 and the second receiver electrode array 35 are relatively small, e.g., on the order of 100 pm to 500 pm, the percentage of the continuous area 33a defined by the outermost perimeter of the driver electrode array 33 that is actually occupied by plurality of driver electrodes is set to be large. In particular, the percentage of the continuous area 33a occupied by the plurality of driver electrodes of the driver electrode array 33 may be greater than or equal to 90%, or greater than or equal to 95%, or greater than or equal to 98%. That is to say, the spacing distance, S, along with the width W, of the driver electrodes of the driver electrode array 33 is set such that the percentage of the continuous area 33a occupied by the plurality of driver electrodes of the driver electrode array 33 may be greater than or equal to 90%, or greater than or equal to 95%, or greater than or equal to 98%.

[0075] The Inventors have found that when the proportion of the continuous area 33a occupied by the driver electrodes of the driver electrode array 33 is sufficiently high, i.e. , greater than or equal to 90%, 95% or 98%, for implementations where the distances in the Z-axis or stacking direction between the driver electrode array 33 and the first receiver electrode array 31 and / or the distance between the driver electrode array 33 and the second receiver electrode array 35 are relatively small, e.g., on the order of 100 pm to 500 pm, the driver electrodes of the driver electrode array 33 can, in effect, help decouple the capacitive couplings between the driver electrode array 33 and the first receiver electrode array 31 and between the driver electrode array 33 and the second receiver electrode array 35. Hence, by providing the driver electrodes of the driver electrode array 33 such that they occupy a large proportion of the continuous area 33a, e.g., 90% or greater, the capacitive sensor element 3 (along with the controller part 4) is capable of providing indications of the capacitive coupling between the driver electrode array 33 and the first receiver electrode array 31 that are indicative of a touch or objected sensed at or adjacent the sensing surface that are unaffected or substantially unaffected by any displacement of the cover 30 I driver electrode array 33 relative to the frame element 2 I second receiver electrode array 35, and is also capable of providing indications of the capacitive coupling between the driver electrode array 33 and the second receiver electrode array 35 that are indicative of a displacement of the cover 30 I driver electrode array 33 relative to the frame element 2 I second receiver electrode array 35 that are unaffected or substantially unaffected by any touch or objected sensed at or adjacent the sensing surface. Hence, the capacitive sensor element 3 described allows the two sets of capacitive couplings to be measured substantially independent of each other.Turning to an example, for the uniform arrangement of driver electrodes in Figure 4, the percentage of the continuous area 33a that is occupied by the driver electrodes, expressed as:

[0076]

[0077] where, n is the number of driver electrodes in the driver electrode array 33, W is the width of each driver electrode and S is the spacing distance between each pair of driver electrodes. By way of example only, taking the twelve driver electrodes of Figure 4 (i.e., n = 12) and assuming a uniform width, W, of 3 mm and a spacing distance, S, of 0.2 mm, the percentage area is equal to approximately 94%. Hence, 94% of the continuous area 33a, in this example, is occupied by the driver electrodes of the driver electrode array 33, and in use, the driver electrode array 33 having such a configuration allows for the capacitive coupling between the driver electrode array 33 and the first receiver electrode array 31 to be unaffected or substantially unaffected by any displacement of the cover 30 I driver electrode array 33 relative to the frame element 2 I second receiver electrode array 35, and the capacitive coupling between the driver electrode array 33 and the second receiver electrode array 35 to be unaffected or substantially unaffected by any touch or objected sensed at or adjacent the sensing surface.

[0078] In the example above, adjacent driver electrodes of the driver electrode array 33 are arranged at uniform pitch, P, or spacing distance, S, in the width direction. More generally, this can be described as adjacent driver electrodes of the driver electrode array 33 being spaced apart from one another along a separation direction that is perpendicular to the edge of at least one of the adjacent driver electrodes. Figure 5, which schematically shows a section, B-B, of the driver electrode array 33 of Figure 4 (see the dashed-dot box in Figure 4), depicts the separation direction, SD, between a first driver electrode 33-1 and a second driver electrode 33-2. As can be seen, the arrow extending from the first driver electrode 33-1 towards the second driver electrode 33-2 is perpendicular to the edge of the first driver electrode 33-1. In the case of two parallel driver electrodes, such as shown in Figure 5, the separation direction is perpendicular to the adjacent edges of both driver electrodes. Moreover, it should be appreciated that, in the example of Figure 4, the separation direction SD is also parallel to the width direction described above (see also the widths W1, W2 indicated in Figure 5 for the first and second driver electrodes respectively), and this width direction is perpendicular to the long edges of each of the driver electrodes. However, the same definition applies even instances where the edges of adjacent electrodes are not parallel to one another, which may be the case for some more complex arrangements of thedriver electrodes (e.g., such as one or more curved driver electrodes or electrodes with no linear edges).

[0079] In the example of Figure 4, the driver electrodes of the driver electrode array 33 are arranged, in the width direction, with a uniform pitch, P. Noting that also in the “bar structure” arrangement of the driver electrode array 33 of Figure 4, each of the driver electrodes also has a uniform width, then it is understood that the width, W, spacing distance, S, and pitch, P, are all uniform across the entire driver electrode array 33. In order to reduce or avoid any cross-coupling between the capacitive couplings between the driver electrode array 33 and the first receiver electrode array 31 with the capacitive couplings between the driver electrode array 33 and the second receiver electrode array 35, the spacing distance, S, should be set to be suitably small. In particular, for implementations where the distances in the Z-axis or stacking direction between the driver electrode array 33 and the first receiver electrode array 31 and / or the distance between the driver electrode array 33 and the second receiver electrode array 35 are relatively small, e.g., on the order of 100 pm to 500 pm, in relation to the pitch, P, it has been found that by setting the spacing distance, S, to be no greater than 10% of the pitch, P, the degree of cross-coupling, if present at all, is at a suitably small level that, in effect, the capacitive couplings between the driver electrode array 33 and the first receiver electrode array 31 and the capacitive couplings between the driver electrode array 33 and the second receiver electrode array 35 can be treated as substantially independent measurements by the controller part 4. In particular the capacitive couplings between the driver electrode array 33 and the first receiver electrode array 31 and the capacitive couplings between the driver electrode array 33 and the second receiver electrode array 35 can be treated as substantially independent measurements by the controller part 4 over the entire extent of the driver electrode array 33, i.e. , there are no regions within the continuous area 33a which experience cross-coupling to the extent that the capacitive couplings between the driver electrode array 33 and the first receiver electrode array 31 and the capacitive couplings between the driver electrode array 33 and the second receiver electrode array 35 cannot be treated as substantially independent measurements. In some implementations, adjacent driver electrodes of the driver electrode array 33 are spaced apart from one another in the width direction by a distance that is no greater than 10%, no greater than 5%, or no greater than 2% of the uniform pitch, P. It should be appreciated that in implementations where the distances in the Z-axis or stacking direction between the driver electrode array 33 and the first receiver electrode array 31 and / or the distance between the driver electrode array 33 and the second receiver electrode array 35 are larger small, e.g., greater than 500 pm, the spacing distance, S, may be set to be greater than 10% of the pitch, P. The requirement to be no greater than a certain percentage listed above isdependent on the distances in the Z-axis or stacking direction between the driver electrode array 33 and the first receiver electrode array 31 and / or the distance between the driver electrode array 33 and the second receiver electrode array 35. In other words, this may be set based on the maximum value for the spacing distance, S, noted above.

[0080] It should be appreciated that in the example of Figure 4, the driver electrodes of the driver electrode array 33 are provided at a uniform pitch, P. However, the same conditions apply when the driver electrodes are not provided at a uniform pitch, P. In such implementations, where the distances in the Z-axis or stacking direction between the driver electrode array 33 and the first receiver electrode array 31 and / or the distance between the driver electrode array 33 and the second receiver electrode array 35 are relatively small, e.g., on the order of 100 pm to 500 pm, the relevant criteria is the pitch between two adjacent driver electrodes, where the spacing distance, S, for that pair of driver electrodes should be no greater than 10% of the pitch, P, for that pair of driver electrodes. For an electrode array 33 that comprises driver electrodes provided at a non-uniform pitch, it should be understood that each of the spacing distances, S, for different pairs of driver electrodes may be different, but that each spacing distance should be no greater than 10%, 5% or 2% of the pitch for the relevant pair of driver electrodes separated by that space.

[0081] This condition of the spacing distance, S, being no greater than 10% of the pitch, P, can also be cast in terms of the width, W, where it is noted that, mathematically, the pitch, P, is equal to the average width, W, of the two adjacent driver electrodes plus the spacing distance, S, therebetween. For example, with reference to Figure 5, the pitch, P, can be considered the average of the widths W1, W2 (i.e., W1 plus W2 divided by two) plus the spacing distance, S. In the example of Figure 5, the widths W1 and W2 are equal, but the same principles apply where the widths are different. Substituting for the pitch P, under the condition that the spacing distance, S, is no greater than the 10% of the pitch, P, means that the spacing distance, S, is set to be no greater than 11.11% of the average width, W. In other implementations, the spacing distance, S, may be set to be no greater than 5.26% (equivalent to no greater than 5% of the pitch, P), or no greater than 2.04% (equivalent to no greater than 2% of the pitch, P). Accounting for rounding errors and manufacturing tolerances, this may more broadly be set as, the driver electrodes are separated or spaced apart from one another by a distance that is no greater than 12%, no greater than 6%, or no greater than 3% of the average of the extent of each of the adjacent driver electrodes along the separation direction (e.g., the average width).

[0082] It should also be understood that the condition on the spacing distance, S, applies to any configuration of the driver electrodes. In Figure 4, the driver electrodes are uniformly spaced(i.e. , provided at a uniform pitch), are arranged such that their lengths are parallel, each have a uniform width W and a width that does not vary with the position along the length of the driver electrode. However, as noted above, this may not be the case in other arrangements of driver electrodes. Accordingly, regardless of the actual arrangement of the driver electrodes in a given driver electrode array 33, for implementations where the distances in the Z-axis or stacking direction between the driver electrode array 33 and the first receiver electrode array 31 and / or the distance between the driver electrode array 33 and the second receiver electrode array 35 are relatively small, e.g., on the order of 100 pm to 500 pm, the spacing distance, S, between an edge of a given one of the driver electrodes (when taken along the separation direction, which is perpendicular to the edge of at least one of the adjacent driver electrodes) and another, adjacent driver electrode, at any point along the length of the given driver electrode is set to be no greater than 12%, no greater than 6%, or no greater than 3% of the average of the extent of each of the adjacent driver electrodes along the separation direction. In this regard, the term “average of the extent of each of the adjacent driver electrodes along the separation direction” is understood to be the extent of a given driver electrode as taken along the separation direction, SD. With reference to Figure 5, if one projects the separation direction SD (which recall is perpendicular to the edge of at least one of the driver electrodes, and in this example, actually both of the driver electrodes 33-1, 33-2), then the extent of the driver electrode is the distance from one edge of the driver electrode to the other edge of that driver electrode along the separation direction SD. In the example of Figure 5, this is simply the width W1 (for the first driver electrode 33-1), but it should be appreciated that this may not necessarily be the width of a given driver electrode depending on the orientation I shape I arrangement of the driver electrodes in different configurations. Hence, even in situations where the driver electrode array 33 takes a different configuration than the parallel, “bar” structure configuration shown in Figure 4, the effects of the present disclosure can still be realised by configuring the spaces between adjacent driver electrodes in accordance with the above criteria.

[0083] Figure 6 shows a schematic representation of a plurality of driver electrodes of a driver electrode array 33, for the purposes of explaining additional considerations or circumstances in respect of the present disclosure. It should be appreciated that the configuration of the driver electrodes in Figure 6 is not necessarily a configuration that meets all the requirements of the present disclosure, but is instead provided to highlight some additional constraints, particularly in the context of more complex driver electrodes arrays 33. Figure 6 in particular shows three driver electrodes, labelled a first driver electrode 33-1, a second driver electrode 33-2, and a third driver electrode 33-3. Other driver electrodes may be present in the overall driver electrode array 33 but are omitted herein for clarity.In some implementations, depending on the configuration of the driver electrodes, it may be that at different positions along the length of a given driver electrode, different ones of the driver electrodes of the electrode array 33 are the adjacent driver electrode to the given driver electrode. That is to say, for a given driver electrode there may be more than two adjacent driver electrodes. Figure 6 shows such an example. For instance, for the first driver electrode 33-1, the first driver electrode 33-1 is adjacent part of the second driver electrode 33-2 along some of the length of the first driver electrode 33-1 and is adjacent part of the third driver electrode 33-3 along a different part of the length of the first driver electrode 33-1. Regardless, provided that the separation between the first driver electrode 33-1 and either of the second driver electrode 33-2 (e.g., shown by the double-headed arrow labelled A) and the third driver electrode 33-3 (e.g., shown by the double-headed arrow labelled B) meet the criteria above in respect of the spacing distance, S, then decoupling of the capacitive couplings between the driver electrode array 33 and the first receiver electrode array 31 or between the driver electrode array 33 and the second receiver electrode array 35 can be achieved. In other words, in accordance with aspects of the present disclosure, for implementations where the distances in the Z-axis or stacking direction between the driver electrode array 33 and the first receiver electrode array 31 and / or the distance between the driver electrode array 33 and the second receiver electrode array 35 are relatively small, e.g., on the order of 100 pm to 500 pm, the distance A should be no greater than 12%, no greater than 6%, or no greater than 3% of the average of the extent of the first driver electrode 33-1 and the second driver electrode 33-2 along the separation direction, and the distance B should be no greater than 12%, no greater than 6%, or no greater than 3% of the average of the extent of the first driver electrode 33-1 and the third driver electrode 33-3 along the separation direction.

[0084] Hence, broadly speaking, in accordance with the principles of the present disclosure, the spacing distance, S, between two adjacent driver electrodes (i.e., the distance between the edges of two adjacent driver electrodes) along a separation direction that is perpendicular to the edge of at least one of the adjacent driver electrodes is set to be equal to or below a maximum value that is set in dependence on the distances in the Z-axis or stacking direction between the driver electrode array 33 and the first receiver electrode array 31 and / or the distance between the driver electrode array 33 and the second receiver electrode array 35. For implementations where the distances in the Z-axis or stacking direction between the driver electrode array 33 and the first receiver electrode array 31 and / or the distance between the driver electrode array 33 and the second receiver electrode array 35 are relatively small, e.g., on the order of 100 pm to 500 pm, the spacing distance, S, betweentwo adjacent driver electrodes along a separation direction that is perpendicular to the edge of at least one of the adjacent driver electrodes is set to be no greater than 12%, no greater than 6%, or no greater than 3% of the average of the extent of each of the adjacent driver electrodes along the separation direction, or are spaced apart from one another along the separation direction by a distance that is no greater than 10%, no greater than 5% or no greater than 2% of the pitch between the two adjacent driver electrodes. In this way, the capacitive couplings between the driver electrode array 33 and the first receiver electrode array 31 and the capacitive couplings between the driver electrode array 33 and the second receiver electrode array 35 can be treated as substantially independent measurements by the controller part 4 over the entire extent of the driver electrode array 33, i.e., there are no regions within the continuous area 33a which experience cross-coupling to the extent that the capacitive couplings between the driver electrode array 33 and the first receiver electrode array 31 and the capacitive couplings between the driver electrode array 33 and the second receiver electrode array 35 cannot be treated as substantially independent measurements. In principle, the spacing distance, S, may be set to any value below the maximum value, e.g., for implementations where the distances in the Z-axis or stacking direction between the driver electrode array 33 and the first receiver electrode array 31 and / or the distance between the driver electrode array 33 and the second receiver electrode array 35 are relatively small, e.g., on the order of 100 pm to 500 pm, the spacing distance S is set to any value no greater than 12%, no greater than 6%, or no greater than 3% of the average of the extent of each of the adjacent driver electrodes along the separation direction, or no greater than 10%, no greater than 5% or no greater than 2% of the pitch between the two adjacent driver electrodes. However, there may be some practical limits on the size of the spacing distance, S. For example, when the insulating substrate 32 is, or forms part of, a printed circuit board, PCB, the driver electrodes of the driver electrode array 33 may be spaced apart from one another by a distance that is equal to or greater than 0.1 mm. For instance, current PCBs may have a minimum size on any electrical traces or spacings between electrical traces of 0.1 mm, due to physical of manufacturing constraints. Therefore, in some implementations, minimum spacing distance, S, between the driver electrodes of the driver electrode array 33 is set to 0.1 mm.

[0085] In the above described implementations, the continuous area 33a of the driver electrode array 33 is broadly similar in size to the areal extent of the touch-sensitive surface defined by the first receiver electrode array 31 (i.e., the touch sensitive surface as shown in Figure 1), and the areal extent of the at second receiver electrode array 35 (i.e., forming the displacement sensing area, which is the area over which displacements of the cover 30 I driver electrode array 33 are able to be sensed). However, in principle, the continuous areain which the driver electrode array 33 is provided can be greater than or equal to at least one of: the areal extent of the touch-sensitive surface defined by the first receiver electrode array 31 , and the areal extent of the second receiver electrode array 35.

[0086] In the above described implementation, the first receiver electrode array 31 comprises a plurality of elongate conductive electrodes arranged such that their lengths are parallel to one another. The width of the elongate electrodes of the first receiver electrode array 31 may be in the range of 0.1 mm to 1.5 mm, although other sizes are contemplated. In a similar manner to the driver electrode array 33, the first receiver electrode array 31 may be configured such that the elongate conductive electrodes are uniformly spaced apart from one another (however, in this case in the X-axis direction) at a certain pitch, for example, in the range of 3 mm to 10 mm. As such, it should be appreciated that the first receiver electrode array 31 typically comprises spaces between adjacent electrodes that are much greater than those provided for in the driver electrode array 33. For example, if it is considered that the first receiver electrode array 31 occupies a continuous area, such as the touch sensitive region shown in Figure 1, when taking equation (1) above and assuming n is equal to 12, W is equal to 1.5 mm and S is also equal to 1.5 mm (where a pitch of 3 mm is equal to a width of 1.5 mm plus a spacing of 1.5 mm), then the percentage area occupied by the first receiver electrodes of the first receiver electrode array 31 can be calculated at around 52% (and this percentage is calculated using the extremes of the above ranges, this would be lower for other values within the ranges quoted). Hence, it should be appreciated that the first receiver electrode array 31 comprises substantially more “free space”, i.e. , a lower percentage of the area is occupied by electrodes) than as compared to the driver electrode array 33. In instances where the pitch of the first receiver electrode array 31 and pitch of the driver electrode array 33 are the same (e.g., within a range of 3 mm to 10 mm), then setting the width of the elongate electrodes of the first receiver electrode array 31 to be thinner I smaller than the plurality of elongate electrodes of the driver electrode array 33 (or conversely setting the width of the driver electrodes to be thicker) allows for the so-called “area-filling” configuration of the driver electrode array 33.

[0087] Accordingly, the capacitive sensor element 3 (along with the controller part 4) is capable of providing indications of the capacitive coupling between the driver electrode array 33 and the first receiver electrode array 31 that are indicative of a touch or objected sensed at or adjacent the sensing surface that are unaffected or substantially unaffected by any displacement of the cover 30 I driver electrode array 33 relative to the frame element 2 I second receiver electrode array 35, and is capable of providing indications of the capacitive coupling between the driver electrode array 33 and the second receiver electrode array 35 that are indicative of a displacement of the cover 30 / driver electrode array 33 relative to theframe element 2 I second receiver electrode array 35 that are unaffected or substantially unaffected by any touch or objected sensed at or adjacent the sensing surface. Hence, the capacitive sensor element 3 described allows the two sets of capacitive couplings to be measured substantially independent of each other.

[0088] Although it has been described above that the capacitive sensor element 3 comprises a compressible substrate 34 that is positioned between the driver electrode array 33 and the second receiver electrode array 35. However, it should be appreciated that in other implementations, the compressible substrate 35 may alternatively or additionally be provided between the second receiver electrode array 35 and the frame element 2 (or any other substrate layers additionally included between the second receiver electrode array 35 and the frame element 2). In this regard, although it has been described that changes in the mutual capacitance between the driver electrode array 33 and the second receiver electrode array 35 are influenced by the movement of at least a part of the driver electrode array 33 towards the second receiver electrode array 35, it should be understood that, particularly if the frame element 2 is conductive and grounded, the mutual capacitance between the driver electrode array 33 and the second receiver electrode array 35 may be influenced by the relative position of the driver electrode array 33 and the second receiver electrode array 35 to the frame element 2, even if the driver electrode array 33 is provided at a fixed position or spacing in the Z-axis or stacking direction with respect to the second receiver electrode array 35. Hence, provided that at least the driver electrode array 33 is capable of relative movement with respect to one of the second receiver electrode array 35 or the frame element 2, the mutual capacitance between the driver electrode array 33 and the second receiver electrode array 35 will be influenced by the application of a displacement load to the capacitive sensor element 3, and hence the touch-sensitive apparatus 1 is capable of sensing displacement. In addition, the described implementation provides a driver electrode array 33 positioned between the first and second receiver electrode arrays 31, 35. However, it should be appreciated that the driver electrode array 33 may comprise further electrodes that are not necessarily driven when obtaining the mutual capacitance measurements as described above. On the one hand, the driver electrode array 33 comprises a plurality of driver electrodes which may be all driven sequentially. When ones of the driver electrodes are not being driven, i.e., the drive signal is not being applied thereto, these non-driven driver electrodes may be connected to ground. These driver electrodes may still be driven at different points in time, however. Therefore, the driver electrode array 33 can be understood to comprise a plurality of driver electrodes, each of which are capable of being driven by a drive signal but not necessarily at the same time. On the other hand, the driver electrode array 33 may comprise electrodes that are never driven by the drive signal but that arepermanently coupled to ground or some other constant voltage. These non-driven electrodes may be interleaved with the drive electrodes in order to help fulfil the area-filling requirements of the drive electrode array 33, discussed above. In such implementations, these non-driven electrodes, if present, are considered to form a part of the driver electrode array 33 despite never having a drive signal applied. The spacing distance, S, requirements described above continue to apply whether the adjacent electrode of the driver electrode array 33 is a driven electrode or a non-driven electrode. Hence, broadly speaking, the driver electrode array 33 comprises a plurality of driver electrodes spaced apart from one another by a spacing distance, S, in a direction perpendicular to the Z-axis I stacking direction, wherein at least one of the plurality of electrodes is configured to receive a drive signal in use.

[0089] The capacitive sensing apparatus 1 can obtain the various capacitive measurements as described above in two broad ways.

[0090] Figure 7 depicts a flow chart for explaining a first implementation in which the capacitive sensing apparatus 1 is configured to obtain measurements indicative of the capacitive couplings between the driver electrode array 33 and the first receiver electrode array 31 and to obtain measurements indicative of the capacitive couplings between the driver electrode array 33 and the second receiver electrode array 35.

[0091] In accordance with a first implementation, the capacitive sensing apparatus 1, and more particularly the controller part 4, is configured to generate and apply a first drive signal to the driver electrode array 33 during a first time period. This is shown at step S1 of the method. The first drive signal may be any suitable drive signal, as described above, such as a timevarying sinusoidal drive signal.

[0092] At step S2, during the first time period, the touch capacitance measurement circuitry 4B is configured to receive signals from the first receiver electrode array 31 that result from the coupling of the first drive signal applied to the driver electrode array 33 during the first time period to the first receiver electrode array 31. In other words, during the first time period, the controller part 4, and in particular the touch capacitance measurement circuitry 4B, receives signals form the first electrode array 31 indicative of the presence or absence of a touch or object sensed at or adjacent the touch-sensitive surface.

[0093] The first drive signal is applied to the driver electrode array 33 for the duration of the first time period. The first drive signal may be applied sequentially to each drive electrode of the driver electrode array 33. In other implementations, the first drive signal may be applied to multiple driver electrodes simultaneously. Equally, the touch capacitance measurement circuitry 4Bmay be configured to receive signals sequentially from each of the receiver electrodes or simultaneously from multiple receiver electrodes.

[0094] At step S3, the processing circuitry 4C is configured to receive the signals from the touch capacitance measurement circuitry 4B and determine at least the presence (or absence) of an object touching or in proximity of the touch-sensitive surface based on the received signals from the first receiver electrode array 31. As described above, this may involve comparing the received signals to measures of the capacitive couplings obtained in advance (e.., at start-up or in a calibration process) and determining whether the measured capacitive coupling deviates or departs from the values obtained by a predetermined threshold in order to determine whether an object is present I detected. As also described above, the processing circuitry 4C may determine the presence I absence of an object, the location of the object on the two dimensional plane of the touch sensitive surface, and / or a distance from the touch sensitive surface.

[0095] At step S4, the capacitive sensing apparatus 1, and more particularly the controller part 4, is configured to generate and apply a second drive signal to the driver electrode array 33 during a second time period. This is shown at step S4 of the method. The second drive signal may be any suitable drive signal, as described above, such as a time-varying sinusoidal drive signal.

[0096] At step S5, during the first time period, the displacement capacitance measurement circuitry 4A is configured to receive signals from the second receiver electrode array 35 that result from the coupling of the second drive signal applied to the driver electrode array 33 during the second time period to the second receiver electrode array 35. In other words, during the second time period, the controller part 4, and in particular the displacement capacitance measurement circuitry 4B, receives signals form the second electrode array 35 indicative of displacement of at least the driver electrode array 35 relative to the frame element 21 second receiver electrode array 35.

[0097] The second drive signal is applied to the driver electrode array 33 for the duration of the second time period. The second drive signal may be applied sequentially to each drive electrode of the driver electrode array 33 in a similar manner to above. In other implementations, the second drive signal may be applied to multiple driver electrodes simultaneously. Equally, the displacement capacitance measurement circuitry 4A may be configured to receive signals sequentially from each of the receiver electrodes or simultaneously from multiple receiver electrodes.At step S6, the processing circuitry 4C is configured to receive the signals from the displacement capacitance measurement circuitry 4A and determine a relative displacement between at least a part of the driver electrode array 33 and the second receiver electrode array 35 based on the received signals from the at second receiver electrode array 35. As described above, this may involve comparing the received signals to measures of the capacitive couplings obtained in advance (e.., at start-up or in a calibration process) and determining whether the measured capacitive coupling deviates or departs from the values obtained by a predetermined threshold in order to determine whether displacement is detected and / or the magnitude of the displacement. As also described above, the processing circuitry 4C may also determine the location of the displacement relative to the two dimensional plane of the touch sensitive surface.

[0098] Once complete, the method may proceed back to step S1. The steps of the method may be continually repeated all the time the capacitive sensing apparatus 1 is operational. It should be appreciated that although step S3 is performed after step S2, it may be that steps S3 and S6 are performed in parallel, or sequentially one after the other.

[0099] While the implementation of Figure 7 may take a relatively longer time to complete, i.e., because there is a first time period dedicated to touch / object detection and a second time period dedicated to displacement detection, it does allow the controller part to adjust any measurement settings to provide more optimised measurements for each set of capacitive couplings. For example, the first and second drive signals may be chosen in order to provide manageable capacitive couplings for each of the displacement capacitance measurement circuitry 4A and touch capacitance measurement circuitry 4B, thereby offering a potentially improved accuracy of result. Alternatively, when the displacement capacitance measurement circuitry 4A and touch capacitance measurement circuitry 4B are embodied as single capacitance measurement circuitry configured to receive the signals at steps S2 and S5 of Figure 7, which may be beneficial for a reduce device footprint and / or costs, the single capacitive measurement circuitry may be configured to dynamically adjust its measurement settings, e.g., having first settings during the first time period and second settings during the second period, to thereby offer a potentially improved accuracy of result.

[0100] Figure 8 depicts a flow chart for explaining a second implementation in which the capacitive sensing apparatus 1 is configured to obtain measurements indicative of the capacitive couplings between the driver electrode array 33 and the first receiver electrode array 31 and to obtain measurements indicative of the capacitive couplings between the driver electrode array 33 and the second receiver electrode array 35.In accordance with a second implementation, the capacitive sensing apparatus 1, and more particularly the controller part 4, is configured to generate and apply a common drive signal to the driver electrode array 33. This is shown at step S11 of the method. The common drive signal may be any suitable drive signal, as described above, such as a time-varying sinusoidal drive signal.

[0101] At step S12, the touch capacitance measurement circuitry 4B is configured to receive signals from the first receiver electrode array 31 that result from the coupling of the common drive signal applied to the driver electrode array 33 to the first receiver electrode array 31. In other words, the controller part 4, and in particular the touch capacitance measurement circuitry 4B, receives signals form the first electrode array 31 indicative of the presence or absence of a touch or object sensed at or adjacent the touch-sensitive surface.

[0102] As above, the common drive signal may be applied sequentially to each drive electrode of the driver electrode array 33. In other implementations, the common drive signal may be applied to multiple driver electrodes simultaneously. Equally, the touch capacitance measurement circuitry 4B may be configured to receive signals sequentially from each of the receiver electrodes or simultaneously from multiple receiver electrodes.

[0103] At step S13, the displacement capacitance measurement circuitry 4A is configured to receive signals from the second receiver electrode array 35 that result from the coupling of the common drive signal applied to the driver electrode array 33 to the second receiver electrode array 35. In other words, the controller part 4, and in particular the displacement capacitance measurement circuitry 4B, receives signals form the second electrode array 35 indicative of displacement of at least the driver electrode array 35 relative to the frame element 21 second receiver electrode array 35. As above, the displacement capacitance measurement circuitry 4A may be configured to receive signals sequentially from each of the receiver electrodes or simultaneously from multiple receiver electrodes.

[0104] At step S14, the processing circuitry 4C is configured to receive the signals from the touch capacitance measurement circuitry 4B and determine at least the presence (or absence) of an object touching or in proximity of the touch-sensitive surface based on the received signals from the first receiver electrode array 31. As described above, this may involve comparing the received signals to measures of the capacitive couplings obtained in advance (e.., at start-up or in a calibration process) and determining whether the measured capacitive coupling deviates or departs from the values obtained by a predetermined threshold in order to determine whether an object is present I detected. As also described above, the processing circuitry 4C may determine the presence / absence of an object, the location ofthe object on the two dimensional plane of the touch sensitive surface, and / or a distance from the touch sensitive surface.

[0105] At step S15, the processing circuitry 4C is configured to receive the signals from the displacement capacitance measurement circuitry 4A and determine a relative displacement between at least a part of the driver electrode array 33 and the second receiver electrode array 35 based on the received signals from the at second receiver electrode array 35. As described above, this may involve comparing the received signals to measures of the capacitive couplings obtained in advance (e.., at start-up or in a calibration process) and determining whether the measured capacitive coupling deviates or departs from the values obtained by a predetermined threshold in order to determine whether displacement is detected and / or the magnitude of the displacement. As also described above, the processing circuitry 4C may also determine the location of the displacement relative to the two dimensional plane of the touch sensitive surface.

[0106] Once complete, the method may proceed back to step S11. The steps of the method may be continually repeated all the time the capacitive sensing apparatus 1 is operational. It should be appreciated that although step S14 is performed after step S13, it may be that steps S13 and S14 are performed in parallel, or in the reverse order.

[0107] In the implementation of Figure 8, the capacitive couplings between the driver electrode array 33 and the first electrode array 31 and between the driver electrode array 33 and the second electrode array 35 are obtained at the same time. Therefore, the second implementation of Figure 8 is capable of more quickly determining whether there are any objects and / or displacement detected as compared to the implementation of Figure 7. However, the second implementation of Figure 8 either requires separate dedicated measurement circuitry for receiving the indications of the capacitive couplings from the first and second receiver electrode arrays 31, 35 respectively, or it requires single measurement circuitry provided with settings that are a compromise for the different capacitances (and in particular the different magnitudes of the capacitances) that are received from each of the first and second receiver electrode arrays 31, 35.

[0108] Thus there has been described a capacitive sensing apparatus for sensing an object touching or in proximity of the capacitive sensing apparatus and for sensing relative displacement of at least a part of the capacitive sensing apparatus. The capacitive sensing apparatus includes: a driver electrode array. The driver electrode array comprises a plurality of electrodes spaced apart from one another by a spacing distance in a direction perpendicular to a first direction. The spacing distance is set in dependence on the distance between the driver electrode array and the first receiver electrode array and / or at least onesecond receiver electrode in the first direction, such that the degree of crosstalk between measurements of the mutual capacitive coupling between the first receiver electrode array and the driver electrode array and measurements of the mutual capacitive coupling between the at least one second receiver electrode and the driver electrode array is such that the measurements of the mutual capacitive coupling between the first receiver electrode array and the driver electrode array are substantially independent of displacements of the at least a part of the driver electrode array relative to the at least one second receiver electrode and measurements of the mutual capacitive coupling between the at least one second receiver electrode and the driver electrode array are substantially independent of objects touching or in proximity of the touch-sensitive surface. Also described is a method for sensing.

[0109] Further particular and preferred aspects of the present invention are set out in the accompanying independent and dependent claims. It will be appreciated that features of the dependent claims may be combined with features of the independent claims in combinations other than those explicitly set out in the claims.

[0110] REFERENCES

[0111] [1] Capacitive Sensors: Design and Applications by Larry K. Baxter, August 1996, Wiley-IEEE Press, ISBN: 978-0-7803-5351-0

Claims

CLAIMS1. A capacitive sensing apparatus for sensing an object touching or in proximity of the capacitive sensing apparatus and for sensing relative displacement of at least a part of the capacitive sensing apparatus, the capacitive sensing apparatus comprising:a first receiver electrode array, the first receiver electrode array defining a touch-sensitive surface;a driver electrode array provided in a stacked arrangement with the first receiver electrode array in a first direction and separated by electrically insulating material;at least one second receiver electrode provided in a stacked arrangement with the driver electrode array in the first direction such that at least a part of the driver electrode array is capable of moving in a direction parallel to the first direction toward the at least one second receiver electrode upon application of a displacement load to the touch-sensitive surface;touch capacitance measurement circuitry configured to receive signals from the first receiver electrode array indicative of the mutual capacitive coupling between the first receiver electrode array and the driver electrode array and determine at least the presence of an object touching or in proximity of the touch-sensitive surface; anddisplacement capacitance measurement circuitry configured to receive signals from the at least one second receiver electrode indicative of the mutual capacitive coupling between the at least one second receiver electrode and the driver electrode array and determine a relative displacement between the at least a part of the driver electrode array and the at least one second receiver electrode,wherein the driver electrode array comprises a plurality of electrodes spaced apart from one another by a spacing distance in a direction perpendicular to the first direction, wherein at least one of the plurality of electrodes is configured to receive a drive signal in use,wherein the spacing distance is set in dependence on the distance between the driver electrode array and the first receiver electrode array and / or at least one second receiver electrode in the first direction, such that the degree of crosstalk between measurements of the mutual capacitive coupling between the first receiver electrode array and the driver electrode array and measurements of the mutual capacitive coupling between the at least one second receiver electrode and the driver electrode array is such that the measurements of the mutual capacitive coupling between the first receiver electrode array and the driver electrode array are substantially independent of displacements of the at least a part of the driver electrode array relative to the at least one second receiver electrode and measurements of the mutual capacitive coupling between the at least one second receiverelectrode and the driver electrode array are substantially independent of objects touching or in proximity of the touch-sensitive surface.

2. The capacitive sensing apparatus of claim 1 , wherein the spacing distance is set such that the degree of crosstalk between signals indicative of the mutual capacitive coupling between the first receiver electrode array and the driver electrode array and signals indicative of the mutual capacitive coupling between the at least one second receiver electrode and the driver electrode array is less than 12 times, preferably less than 10 times, and more preferably less than 7 times of the other of the signals indicative of the mutual capacitive coupling between the first receiver electrode array and the driver electrode array and signals indicative of the mutual capacitive coupling between the at least one second receiver electrode and the driver electrode array.

3. The capacitive sensing apparatus of claim 1 or 2, wherein the distance between the driver electrode array and the first receiver electrode array and / or at least one second receiver electrode in the first direction is less than 500 pm, or between 100 pm to 500 pm.

4. The capacitive sensing apparatus of claim 3, wherein the driver electrode array is provided within a continuous area defined by the outermost perimeter of the driver electrode array, wherein the continuous area has a normal parallel to the first direction, and wherein the percentage of the continuous area defined by the outermost perimeter of the driver electrode array that is occupied by the plurality of driver electrodes is greater than or equal to 90%, or greater than or equal to 95%, or greater than or equal to 98%.

5. The capacitive sensing apparatus of claim 4, wherein the continuous area comprises the area of the driver electrodes of the driver electrode array and the area of the spaces between the driver electrodes of the driver electrode array.

6. The capacitive sensing apparatus of any of claims 3 to 5, wherein adjacent driver electrodes are spaced apart from one another along a separation direction that is perpendicular to the edge of at least one of the adjacent driver electrodes by a distance that is no greater than 12%, no greater than 6%, or no greater than 3% of the average of the extent of each of the adjacent driver electrodes along the separation direction.

7. The capacitive sensing apparatus of any of claims 3 to 6, wherein the driver electrodes are elongated in a length direction and have a width in a direction perpendicular tothe length direction, wherein the driver electrodes are arranged parallel to each other in the length direction.

8. The capacitive sensing apparatus of claim 7, wherein the driver electrodes are arranged, in the width direction, to have a uniform pitch, which is the distance between centres of adjacent driver electrodes in the width direction.

9. The capacitive sensing apparatus of claim 8, wherein adjacent driver electrodes are spaced apart from one another in the width direction by a distance that is no greater than 10%, no greater than 5% or no greater than 2% of the uniform pitch.

10. The capacitive sensing apparatus of any of the preceding claims, wherein the driver electrode array is provided on a printed circuit board, PCB, and wherein adjacent driver electrodes are spaced apart from one another by a distance equal to or greater than 0.1 mm.

11. The capacitive sensing apparatus of any of claims 3 to 9, and claim 10 when dependent on any of claims 3 to 9, wherein the continuous area in which the driver electrode array is provided is greater than or equal to at least one of: the areal extent of the touch-sensitive surface defined by the first receiver electrode array, and the areal extent of the at least one second receiver electrode.

12. The capacitive sensing apparatus of any of the preceding claims, wherein the electrically insulating material is a first insulating substrate having a first surface and a second, opposite surface, and wherein the first receiver electrode array is provided on the first surface of the first insulating substrate and the driver electrode array is provided on the second, opposite surface of the first insulating substrate.

13. The capacitive sensing apparatus of claim 12, wherein the first insulating substrate is formed from a flexible material that is capable of flexing upon application of a displacement load to the touch-sensitive surface, wherein optionally the capacitive sensing apparatus further comprises a cover layer provided such that the first receiver electrode array is positioned between the cover layer and the first insulating substrate, and wherein the cover layer is formed from a flexible material that is capable of flexing upon application of a displacement load to the touch-sensitive surface.

14. The capacitive sensing apparatus of any of the preceding claims, wherein the first receiver electrode array comprises a plurality of elongate electrodes arranged such that theirlengths are parallel to one another, and wherein the driver electrode array comprises a plurality of elongate electrodes arranged such that their lengths are parallel to one another and perpendicular to the lengths of the plurality of elongate electrodes of the first receiver electrode array.

15. The capacitive sensing apparatus of claim 14, wherein the elongate electrodes of the first receiver electrode array have a thinner width than the plurality of elongate electrodes of the driver electrode array.

16. The capacitive sensing apparatus of any of the preceding claims, further comprising a compressible layer positioned between the driver electrode array and the at least one second receiver electrode, wherein the compressible layer is configured so as to compress upon application of a displacement load to the touch-sensitive surface to cause the at least a part of the driver electrode array to move toward the at least one second receiver electrode in the direction parallel to the first direction.

17. The capacitive sensing apparatus of any of claims 1 to 15, further comprising a compressible layer positioned between the at least one second receiver electrode and a frame element on which the capacitive sensing element is provided, wherein the compressible layer is configured so as to compress upon application of a displacement load to the touch-sensitive surface to cause the at least a part of the driver electrode array to move toward the frame element in the direction parallel to the first direction.

18. The capacitive sensing apparatus of any of the preceding claims, wherein the driver electrode array comprises a plurality of elongate electrodes arranged such that their lengths are parallel to one another, and wherein the at least one second receiver electrode is elongated in a length direction and is arranged such that substantially the at least one second receiver electrode is perpendicular to the lengths of the plurality of elongate electrodes of the driver electrode array.

19. The capacitive sensing apparatus of any of the preceding claims, further comprising drive circuitry configured to generate and apply a first drive signal to the driver electrode array,wherein the touch capacitance measurement circuitry is configured to receive signals from the first receiver electrode array resulting from the coupling of the first drive signal applied to the driver electrode array to the first receiver electrode array and determine atleast the presence of an object touching or in proximity of the touch-sensitive surface based on the received signals from the first receiver electrode array, andwherein the displacement capacitance measurement circuitry is configured to receive signals from the at least one second receiver electrode resulting from the coupling of the first drive signal applied to the driver electrode array to the at least one second receiver electrode and determine a relative displacement between the at least a part of the driver electrode array and the at least one second receiver electrode based on the received signals from the at least one second receiver electrode.

20. The capacitive sensing apparatus of any of claims 1 to 18, further comprising drive circuitry configured to generate and apply a first drive signal to the driver electrode array during a first time period and to generate and apply a second drive signal to the driver electrode array during a second time period,wherein the touch capacitance measurement circuitry is configured to receive signals from the first receiver electrode array resulting from the coupling of the first drive signal applied to the driver electrode array during the first time period to the first receiver electrode array and determine at least the presence of an object touching or in proximity of the touch-sensitive surface based on the received signals from the first receiver electrode array, and wherein the displacement capacitance measurement circuitry is configured to receive signals from the at least one second receiver electrode resulting from the coupling of the second drive signal applied to the driver electrode array during the second time period to the at least one second receiver electrode and determine a relative displacement between the at least a part of the driver electrode array and the at least one second receiver electrode based on the received signals from the at least one second receiver electrode.

21. A method for sensing an object touching or in proximity of a capacitive sensing apparatus of any one of claims 1 to 20 and / or for sensing relative displacement of at least a part of the capacitive sensing apparatus of any one of claims 1 to 20, the method comprising:applying a drive signal to the driver electrode array;receiving one or more signals from the first receiver electrode array and determining at least the presence of an object touching or in proximity of the touch-sensitive surface on the basis of the received one or more signals from the first receiver electrode array; and / or receiving one or more signals from the at least one second receiver electrode and determining a relative displacement between the at least a part of the driver electrode array and the at least one second receiver electrode on the basis of the received one or more signals from the at least one second electrode.

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