as) United States
`a2) Patent Application Publication co) Pub. No.: US 2010/0045632 Al
`
`(43) Pub. Date: Feb. 25, 2010
`Yilmazet al.
`
`US 20100045632A1
`
`(54) CAPACITIVE POSITION SENSOR
`
`Publication Classification
`
`(75)
`
`Inventors:
`
`Esat Yilmaz, Southhampton (GB);
`Peter Sleeman, Atmel (GB);
`Samuel Brunet, Cowes (GB);
`Matthew Trend, Atmel (GB);
`Harald Philipp, Hamble (GB)
`
`(51)
`
`Int. Cl.
`(2006.01)
`GO6F 3/044
`(2006.01)
`GO6F 3/045
`(52) US. C0e coecccccsssccssssssssssssreeseeseee 345/174; 178/18.06
`(57)
`ABSTRACT
`
`A capacitive position sensor has a two-layer electrode struc-
`ture. Drive electrodes extending inafirst direction on a first
`Correspondence Address:
`plane on oneside of a substrate. Sense electrodes extend in a
`SCHWEGMAN, LUNDBERG & WOESSNER/
`second direction on a second plane on the other side of the
`ATMEL
`substrate so that the sense electrodes cross the drive elec-
`P.O. BOX 2938
`trodesat a plurality of intersections which collectively form a
`MINNEAPOLIS, MN 55402 (US)
`position sensing array. The sense electrodes are provided with
`branches extending in the first direction part of the way
`towards each adjacent sense electrode so that end portions of
`the branches ofadjacent sense electrodes co-extend with each
`other in the first direction separated by a distance sufficiently
`smallthat capacitive coupling to the drive electrode adjacent
`to the co-extending portion is reduced. Providing sense elec-
`trode branches allow a sensor to be made which hasa greater
`extentin the first direction for a given numberof sense chan-
`nels, since the co-extending portions provide an interpolating
`effect. The number of sense electrode branches per drive
`electrode can be increased which allowsa sensor to be made
`which has ever greater extent in the first direction without
`having to increase the numberof sense channels.
`
`(73) Assignee:
`
`ATMEL CORPORATION,San
`Jose, CA (US)
`
`(21) Appl. No.:
`
`12/421,713
`
`(22)
`
`Filed:
`
`Apr. 10, 2009
`
`Related U.S. Application Data
`
`(60) Provisional application No. 61/044,038, filed on Apr.
`10, 2008.
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`Figure 1C
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`CAPACITIVE POSITION SENSOR
`
`BACKGROUND OF THE INVENTION
`
`[0001] The inventionrelates to capacitive position sensors.
`More particularly the invention relates to 2-dimensional
`capacitive position sensors of the type based on capacitive
`proximity sensing techniques. Such sensors maybereferred
`to as 2-dimensional capacitive transducing (2DCT)sensors.
`2DCT sensors are based on detecting a disturbance in a
`capacitive coupling of sensor electrodes caused by the prox-
`imity of a pointing object. A measured location for the dis-
`turbance corresponds to a measuredposition for the pointing
`object.
`[0002] U.S. Pat. No. 6,452,514, U.S. Pat. No. 7,148,704
`and U.S. Pat. No. 5,730,165 disclose prior art capacitive
`touch sensors.
`
`2DCT sensors are typically actuated by a human
`[0003]
`finger, or a stylus. Example devices include touch screen and
`touch sensitive keyboards/keypads, e.g. as used for control-
`ling consumer electronic devices/domestic appliances, and
`possibly in conjunction with an underlying display, such as a
`liquid crystal display (LCD), or cathode ray tube (CRT).
`Other devices which may incorporate 2DCTsensors include
`pen-input tablets and encoders used in machinery for feed-
`back control purposes,
`for example. 2DCT sensors are
`capable of reporting at least a 2-dimensional coordinate, Car-
`tesian or otherwise, related to the location of an object or
`human bodypart, by meansof a capacitance sensing mecha-
`nism.
`
`[0004] Devices employing 2DCT sensors have become
`increasingly popular and common, not only in conjunction
`with personal computers, but also in all manner of other
`appliances suchaspersonaldigital assistants (PDAs), point of
`sale (POS) terminals, electronic information and ticketing
`kiosks, kitchen appliances and the like. 2DCT sensors are
`frequently preferred to mechanical switches for a numberof
`reasons. For example, 2DCT sensors require no movingparts
`and so are less prone to wear than their mechanical counter-
`parts. 2DCTsensors can also be madein relatively small sizes
`so that correspondingly small, and tightly packed keypad
`arrays can be provided. Furthermore, 2DCT sensors can be
`provided beneath an environmentally sealed outer surface/
`cover panel. This makes their use in wet environments, or
`wherethere is a dangerofdirt or fluids entering a device being
`controlled attractive. Furthermorestill, manufacturers often
`prefer to employ interfaces based on 2DCT sensors in their
`products because such interfaces are often considered by
`consumers to be more aesthetically pleasing than conven-
`tional mechanical input mechanisms(e.g. push-buttons).
`[0005] WO 2009/027629, published on 5 Mar. 2009,
`describes a capacitive touch sensor comprising a dielectric
`panel overlying a drive electrode with two sense electrodes.
`Oneofthe sense electrodes is positioned to be shielded from
`the drive electrode bythefirst sense electrode, so that the first
`sense electrode receives the majority of the charge coupled
`from the drive electrode and the second sense electrodepri-
`marily registers noise. A sensing circuit including two detec-
`tor channels is connected to the first (coupled) and second
`(noise) sense electrodes to receive signal samples respec-
`tively. The sensing circuit is operable to outputa final signal
`obtained by subtracting the second signal sample from the
`first signal sample to cancel noise.
`[0006] However, the methods described above increase the
`size and thickness, and may decrease the resolution of a
`
`device incorporating a display screen with a 2DCT sensor
`whenit is more fashionable and desirable to produce smaller
`devices. Furthermore, additional steps are required during
`manufacture and as a result there is an increased cost due to
`
`further components being needed.
`[0007] European patent EP 1821175 describes an alterna-
`tive solution to reduce the noise collected on a 2DCT touch
`
`sensor. EP 1821175 discloses a display device with a touch
`sensor which is arranged so that the two dimensional touch
`sensor is overlaid upon a display device to form a touch
`sensitive display screen. The display device uses an LCD
`arrangement with vertical and horizontal switching of the
`LCDpixels. The touch sensing circuit includes a current
`detection circuit, a noise elimination circuit as well as a
`sampling circuit for each of a plurality of sensors, which are
`arranged to form the two-dimensional sensor array. The cur-
`rent detection circuit receives a strobe signal, which is gen-
`erated from the horizontal and vertical switching signals of
`the LCD screen. Thestrobesignalis used to trigger a blanking
`of the current detection circuit during a period in which the
`horizontal switching voltage signal may affect the measure-
`ments performed bythe detection circuit.
`[0008] WO 2009/016382, published on 5 Feb. 2009,
`describes a sensor used to form a two dimensional touch
`
`sensor, which can be overlaid on a liquid crystal display
`(LCD)screen. As such,the effects of switching noise on the
`detection of an object caused by a commonvoltage signal of
`the LCD screen can be reduced. The sensor comprises a
`capacitance measurement circuit operable to measure the
`capacitance of the sensing element and a controller circuit to
`control charging cycles of the capacitance measurementcir-
`cuit. The controller circuit is configured to produce charging
`cycles at a predetermined time and in a synchronous manner
`with a noise signal. For example, the charge-transfer cycles or
`‘bursts’ may be performed during certain stages of the noise
`output signal from the display screen, i.e. at stages where
`noise does not significantly affect the capacitance measure-
`ments performed. Thus, the sensor can be arrangedto effec-
`tively pick up the noise output from a display screen and
`automatically synchronize the charge-transfer bursts to occur
`during stages of the noise output cycle.
`[0009]
`FIG. 21 of the accompanying drawingsillustrates
`schematically a representative portion of the prior art elec-
`trode pattern of U.S. Pat. No. 6,452,514 or its equivalent WO
`00/44018, published on 27 Jul. 2000. A plurality of drive
`electrodes X1, X2, X3 and X4 extending rowwise are
`arranged with a plurality of sense electrodes Y1, Y2, Y3 and
`Y4 extending columnwise,
`the intersections or crossings
`between X and Y electrodes forming a matrix or grid of
`sensing points or areas 220. It will be understood the X and Y
`electrodes do notliterally intersect, but are offset in the ver-
`tical or Z direction, orthogonal to the plane of the drawing,
`being separated by a dielectric layer—typically a substrate
`panel which bears the X electrodes on one side and the Y
`electrodes on the other side. Each crossed electrode area 220
`acts as a key so that the presence of a body such as a user’s
`finger is detected as a result of a change in an amount of
`charge whichis transferred between the two electrodesat the
`key location. With this arrangement, each of the electrodes
`X1, X2, X3 and X4 are driven with a drive circuit 118 via
`connections 105 andthe other electrodes Y1, Y2, Y3 and Y4
`are connected to a charge measurementcircuit 118 via sense
`channels 116 which detects an amount of charge presentat
`each of the sensing areas 220. It will be appreciated that for
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`surface. However, it will be appreciated that the drive elec-
`trodes showninthe figure could also be used for two-layer or
`dual layer designs.
`[0013]
`It would therefore be desirable to provide an elec-
`trode pattern for a mutual capacitive or active type 2DCT
`sensor that can be usedto allow the size of the overall sensi-
`
`tive area to be increased without needing to introduce more
`sense channels.
`
`SUMMARY OF THE INVENTION
`
`simplicity all of the control circuitry has been included in a
`single circuit 118. Such two dimensionalcapacitive transduc-
`ing (2DCT) sensors are typically used with devices which
`include touch sensitive screens or touch sensitive keyboards/
`keypads which are used in for example in consumer elec-
`tronic devices and domestic appliances. The 2DCTis of the
`so-called “active”or “mutual”type, in which proximity of an
`object is sensed by the changes inducedin coupling between
`a drive electrode and one or more adjacent sense electrodes.
`[0010]
`In the above 2DCTsensor, interpolation is used to
`[0014] According toafirst aspect of the invention there is
`determine the location of an object or finger adjacent the
`provided a capacitive position sensor comprising: a plurality
`sensor. This is done by using the signals from the sense area
`of drive electrodes extending in a first direction on a first
`being touched and the neighboring sense areas in a linear
`plane; a plurality of sense electrodes extending in a second
`interpolation algorithm. However, for an interpolation to be
`direction on a secondplaneoffset from the first plane so that
`accurate the electric field between adjacent drive electrodes
`the sense electrodes cross the drive electrodesat a plurality of
`should be linearor at least known.Ifthe electrodes are placed
`intersections which collectively form a position sensing
`close together it can be assumedthat the electric filed between
`array; wherein the sense electrodes have branches extending
`twoelectrodesis linear. That is to say that as you move away
`in the first direction part of the way towards each adjacent
`from an electrode, the field reduces in a linear fashion.
`sense electrode so that end portions of the branches of adja-
`cent sense electrodes co-extend with each other in the first
`[0011] As the size of devices that use 2DCT sensors is
`increased, larger area 2DCTsensors are required. To increase
`direction separated by a distance sufficiently small
`that
`the area of the 2DCT sensor while keeping the same resolu-
`capacitive coupling to the drive electrode adjacent to the
`tion and accuracy(i.e. avoid using a non-linearinterpolation
`co-extending portion is reduced.
`method) the number of drive and sense electrodes could be
`[0015]
`Inone embodiment, for each drive electrode there is
`increased. However, this means that the number of connec-
`one set of sense electrode branches providing co-extending
`tions required from the control circuits is increased which in
`portions that occupy a region in between adjacentsense elec-
`turn results in more expensive control circuits and increased
`trodes in the first direction. Providing sense electrode
`acquisition times, since the acquisition of signals from each
`branchesallow a sensor to be made whichhasa greater extent
`of the sensing areas typically needsto be carried outat least
`in the first direction for a given numberof sense channels.
`partially in series, since not all sensing areas can be polled
`[0016]
`Inother embodiments, for each drive electrode there
`simultaneously owing to restrictions on the numberof drive
`are multiple sets of sense electrode branchesthat are offset
`and sense lines, and controller channels, i.e. chip pins.
`from each other in the second direction, the multiple sets
`providing respective co-extending portions extending over
`[0012]
`FIG. 22 of the accompanying drawings illustrates
`different respective regions in the first direction. Increasing
`schematically a representative portion of the prior art elec-
`the numberof sense electrode branches per drive electrode
`trode pattern US 2008/0246496, published on 9 Oct. 2008.
`allows a sensor to be made whichhasevergreater extent in the
`Thefigure illustrates a pattern of electrodes comprising lon-
`first direction without having to increase the numberof sense
`gitudinal(bar) drive electrodes 152. The drive electrodes 152
`channels.
`are coupledvia drive channels 158 and 160 to a controller (not
`shownin the figure). Each drive channel supplies drive sig-
`nals to the group of four drive electrodes 152. The drive
`electrodes 152 are each connected to one another by a chain or
`row ofresistors 170 having the same value. Alternatively, a
`single resistive strip could be used (not shown in figure).
`When operated the grouped drive electrodes will receive a
`different value drive signal. For example, when drive channel
`160 is connected to a drive signal and drive channel 158 is
`connected to ground, the electrode connected directly to drive
`channel 160 will receive the applied signal value, the drive
`electrode below will receive two thirds of the applied signal
`value andthedrive electrode belowthat will receive a third of
`
`[0017] The sense electrodes are separated from each other
`in thefirst direction by a distance P,.,,,, and the drive elec-
`trodes are separated from each other in the seconddirection
`by a distance P,,,,.. wherein: P,.,,,¢/P#iye=2 M+1, where ‘m’
`is the numberof sets of sense electrode branches per drive
`electrode. The drive electrode pitch P,,,,. 1s preferably of
`comparable dimension, or smaller, to the touch size of the
`touching object for which the sensor is designed. The touch-
`ing object for which the sensor is designed may bea finger,
`e.g. of touch size 8-10 mm diameter. A stylus could also be
`used.
`
`Inplan view each drive electrode covers an area that
`[0018]
`fully encloses its associated sense electrode branches. In
`other words the ‘footprint’ of the sense electrodes lie within
`their associate drive electrode, or the periphery of the drive
`electrode lies outwardly beyondthe sense electrodes associ-
`ated therewith in at least the second direction and preferably
`also the first direction.
`
`electrodes preferably substantially
`[0019] The drive
`entirely coverthefirst plane with individual ones of the drive
`electrodes being separated from neighboring drive electrodes
`by small gaps, wherein the gaps are preferably dimensioned
`to be sufficiently smallto be invisible or almost invisible. The
`gaps are preferably less than around 100 micrometers, for
`example with ITO drive electrodes. Gap values of less than
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`the applied signal value. In the example described above, the
`fourth electrode connected directly to the drive channel 158 in
`the figure will be connected to ground. However, the above
`method can be repeated with drive channel 158 being con-
`nected to a drive signal and drive channel 160 being con-
`nected to ground. This effectively, allows four drive elec-
`trodes to be driven using only two drive channels. The
`arrangement shown in the figure can be repeated, and
`expandedto include moreintermediate drive electrodes with
`respective resistors. However, the method described aboveis
`only suitable for the drive electrodes andis not transferable to
`the sense electrodes. The sense electrodes shownin thefigure
`are interleaved with adjacent drive electrodes on a single
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`90, 80, 70, 60 or 50 micrometers mayalso be preferred. With
`some electrode materials, such as PET, it may be difficult to
`fabricate such small gaps, so in someinstances the gaps are
`preferably less than around 250, 200 or 150 micrometers
`[0020] The drive and sense electrodes may be the only
`electrode layers provided, a two-layer electrode construction
`leading to improved optical
`transmission for transparent
`embodiments such as used for touch-sensitive displays, thin-
`ner overall construction, and lower cost.
`[0021] An important combination is the above-defined
`capacitive touch sensor with a display module. The display
`module, for example an LCD or OLED display panel, will
`typically by arranged below thefirst layer and distal the touch
`surface so that from top to bottom, or outside to inside the
`device, the components will be—dielectric layer the upper
`surface of which will be the touch surface—layer 2—sub-
`strate—layer 1—display panel, with the display panel being
`inside the device housing or outer shell. In a display applica-
`tion, the electrodes will likely be made of ITO.
`[0022]
`Insome embodiments, each drive and/orsenseelec-
`trode is made of a continuoussheetof electrically conductive
`material, such as ITO or a metal. In other embodiments, each
`drive and/or sense electrode is made of a meshorfiligree
`pattern of interconnectedlines of highly conductive material
`which collectively define each electrode. Still
`further
`embodiments use continuous sheets for one of the electrode
`
`types and meshesfor the other electrode type. In the mesh
`approach, the interconnected lines preferably have a suffi-
`ciently small width so as to be invisible or almostinvisible.
`They can then be made of material that is not inherently
`invisible, e.g. a metal such as copper, butstill remain practi-
`cally invisible.
`[0023] The invention can be implemented to form a Carte-
`sian ‘xy’ grid oftouch sensor locations. In particular, the drive
`electrodes can extendin a first linear direction and the sense
`electrodes in a second linear direction transverse to thefirst
`
`linear direction so that the plurality of intersections form a
`grid pattern, for example a square, diamondor rectangular
`grid. The invention can also be implemented to form a polar
`‘r0’ grid, wherein the drive electrodes extend arcuately and
`the sense electrodes extend radially so that the plurality of
`intersections lie on one or more arcuate paths.
`[0024] A further aspect of the invention relates to a touch
`sensitive panel for a capacitive touch sensor, the touch sensi-
`tive panel having a plurality of drive electrodes arranged on
`one side of a substrate in a first layer and a plurality of sense
`electrodes arranged on the other side of the substrate in a
`second layer so that the sense electrodes cross the drive elec-
`trodesat a plurality of intersections offset from each other by
`the thickness of the substrate, wherein the drive electrodes
`substantially entirely coverthe first layer with individual ones
`of the drive electrodes being separated from neighboring
`drive electrodes by small gaps.
`[0025] According to a second aspectof the invention there
`is provided a touch sensitive panel for a capacitive touch
`sensor, the touch sensitive panel having a plurality of drive
`electrodes arranged on oneside of a substrate in a first layer
`and a plurality of sense electrodes arranged on the other side
`of the substrate in a secondlayer so that the sense electrodes
`cross the drive electrodes ata plurality of intersections offset
`from each other by the thickness ofthe substrate, wherein the
`sense electrodes have branches extendinginthefirst direction
`part of the way towards each adjacent sense electrode so that
`end portions of the branches of adjacent sense electrodes
`
`co-extend with each otherin thefirst direction separated by a
`distance sufficiently small that capacitive coupling to the
`drive electrode adjacent
`to the co-extending portion is
`reduced.
`
`[0026] According to a third aspect of the invention there is
`provided a methodof sensing position of an actuation on a
`two-dimensionalposition sensor accordingto the first aspect
`of the invention, the method comprising:
`applying drive signals to each of the plurality of drive elec-
`trodes;
`measuring sense signals received from eachofthe plurality of
`sense electrodes representing a degree of capacitive coupling
`of the drive signals between the drive electrodes and each
`group ofthe sense electrodes;
`determining the position in thefirst direction by an interpo-
`lation between sense signals obtained from each of the plu-
`rality of sense electrodes; and
`determining the position in the second direction by an inter-
`polation between sense signals obtained by sequentially driv-
`ing each of the plurality of drive electrodes with respective
`drive signals.
`[0027] According to an alternative formulation of the
`invention, there is provided a capacitive sensor having an
`electrode pattern comprising a plurality of sense electrodes
`generally extending ina y direction across a sensing area and
`spaced apart in an x direction; wherein the extent in the y
`direction of each of the sense electrodes is herein referred to
`a spine; wherein each of the sense electrodes further com-
`prises a plurality of extents spaced apart in the y direction
`herein referred to as first-branches that extend from the spine
`in the x direction and a —x direction opposingthe x direction,
`whose extent from the spine in the second and —x direction is
`not more than the spacing between adjacent spines; and
`wherein the first-branches of each of the sense electrodes
`coextend over the same portion of the sensitive area as the
`first-branches of adjacent spines.
`[0028] The electrode pattern may further comprise a plu-
`rality of drive electrodes extending in the x direction and
`interleaved in the y direction; wherein each of the drive elec-
`trodes extends in the first and x direction over the same
`
`portion of the sensing area asthefirst-branches of each ofthe
`sense electrodes.
`
`[0029] The drive and sense electrodes may be disposed on
`opposing surfaces of a substrate.
`[0030] The drive and sense electrodes may be disposed on
`a surface of different substrates.
`
`[0031] The electrode pattern may further comprise a plu-
`rality of second-, third- or fourth-branches interleaved with
`the first-branches, wherein the coextension of branches from
`adjacent spines is offset from each other.
`[0032] According to another aspect ofthe present invention
`there is provided a two-dimensional sensor comprising the
`electrode pattern, wherein the sensor may further comprise a
`controller comprising a drive unit for applying drive signals to
`the drive electrodes, and a sense unit for measuring sense
`signals received from eachof the respective sense electrodes
`representing a degree of capacitive coupling of the drive
`signals between the drive electrodes and each of the sense
`electrodes.
`
`[0033] The controller may further comprise a processing
`unit for calculating a position of an interaction with the sen-
`sitive area from an analysis of the sense signals obtained by
`applying drive signals to the drive electrodes.
`
`PETITIONERS
`
`Exhibit 1009, Page 27
`
`PETITIONERS
`Exhibit 1009, Page 27
`
`

`

`US 2010/0045632 Al
`
`Feb. 25, 2010
`
`[0034] The processing unit may be operable to determine
`position in the x direction by an interpolation between sense
`signals obtained from each of the plurality of sense elec-
`trodes.
`
`[0035] The processing unit may be operable to determine
`position in the y direction by an interpolation between sense
`signals obtained by sequentially driving each of the plurality
`of drive electrodes with respective drive signals.
`[0036] According to another aspect ofthe present invention
`there is provided a methodofsensing position of an actuation
`on a two-dimensional position sensor comprising: an elec-
`trode pattern comprising a plurality of sense electrodes gen-
`erally extending in a y direction across a sensing area and
`spaced apart in an x direction, wherein the extent in the y
`direction of each of the sense electrodes is herein referred to
`
`a spine, wherein each of the sense electrodes further com-
`prises a plurality of extents spaced apart in the y direction
`herein referred to as first-branches that extend from the spine
`in the x direction and a —x direction opposingthe x direction,
`whose extent from the spine in the second and —x direction is
`not more than the spacing between adjacent spines, and
`wherein the first-branches of each of the sense electrodes
`
`coextend over the same portion of the sensitive area as the
`first-branches of adjacent spines; a plurality of drive elec-
`trodes extending in the x direction and interleaved in the y
`direction; wherein each of the drive electrodes extends in the
`first and x direction over the same portion of the sensing area
`as the first-branches of each of the sense electrodes; the
`method comprising: applying drive signals to each of the
`plurality of drive electrodes; measuring sense signals
`received from each ofthe plurality of sense electrodes repre-
`senting a degree of capacitive coupling of the drive signals
`between the drive electrodes and each group of the sense
`electrodes; determining the position in the x direction by an
`interpolation betweensense signals obtained from each ofthe
`plurality of sense electrodes; and determining the position in
`the y direction by an interpolation between sense signals
`obtained by sequentially driving each oftheplurality of drive
`electrodes with respective drive signals.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`For a better understanding of the invention and to
`[0037]
`show how the same may becarried into effect reference is
`now madeby wayof example to the accompanying drawings.
`[0038] FIG.1A showsa side view of a two-electrode layer
`capacitive touch screen according to an embodimentof the
`present invention;
`[0039]
`FIG. 1B shows a perspective view of a two-elec-
`trode layer capacitive touch screen according to an embodi-
`mentof the present invention;
`[0040]
`FIG. 1C showsa side view of a two-electrode layer
`capacitive touch screen according to another embodimentof
`the present invention;
`[0041]
`FIG. 1D showsa side view of a two-electrode layer
`capacitive touch screen according to another embodimentof
`the present invention;
`[0042]
`FIG. 1E showsa side view of a two-electrode layer
`capacitive touch screen according to an embodimentof the
`present invention;
`[0043]
`FIG. 2A showsan electrode pattern of drive elec-
`trodes with resistive elements according to an embodimentof
`the invention;
`
`FIG. 2B showsa portion of the electrode pattern
`[0044]
`shown in FIG. 2A with a meanderpattern of electrode mate-
`rial;
`FIG. 2C showsa portion of the electrode pattern
`[0045]
`shownin FIG. 2A with screen printed resistors;
`[0046]
`FIG. 2D showsa portion of the electrode pattern
`shown in FIG. 2A with discrete resistors;
`[0047]
`FIG. 3 shows a portion of the electrode pattern
`shown in FIG. 2B.
`
`FIG. 4 shows a portion of the electrode pattern of
`[0048]
`drive electrodes according to an embodimentofthe invention;
`[0049]
`FIG. 5A showsa portion of the electrode pattern
`shown in FIG. 2A;
`[0050]
`FIG. 5B showsa typicalfingertip;
`[0051]
`FIG. 6 showsan electrode pattern ofdrive electrodes
`according to an embodimentofthe invention;
`[0052]
`FIG. 7A showsan electrode pattern of sense elec-
`trodes according to an embodimentofthe invention;
`[0053]
`FIG. 7B shows a two-electrode layer capacitive
`touch screen according to an embodiment of the present
`invention with drive and sense units connected via channels to
`a controller;
`[0054]
`FIG. 8A shows schematically in plan view a portion
`of the electrode pattern shown in FIG. 7A with infilling elec-
`trodes;
`FIG. 8B is a cross-section through a part of FIG. 8A
`[0055]
`illustrating capacitive paths betwe