KR20070032924A - Capacitive touch sensor - Google Patents

Abstract

According to the invention, there is provided a capacitive sensor 2 for determining the presence of an object such as a user's finger or a needle. The sensor has a substrate 4 made of a transparent plastic material, for example PET, on which electrodes are deposited. For example, resistance driving electrodes 60 formed of transparent ITO are arranged on one side of the substrate, and resistance sensing electrodes 68 and 70, which may be formed of transparent ITO, are arranged on the other side of the substrate. Thus, an overall transparent sensor can be formed. A short circuit connection 30 is formed which is configured to connect two positions in one of the electrodes. The electrodes are connected to the respective drive channel 6 and the sense channel 8. By providing a short circuit connection between two locations at one or the other (or both) of the electrodes, a low resistance connection is provided between the other location on the electrode and the corresponding drive or sense channel.

Capacitive touch sensor, driving channel, sensing channel

Description

Capacitive Touch Sensors {CAPACITIVE TOUCH SENSOR}

1A and 1B schematically illustrate a front view and a rear view of a two-dimensional capacitive position sensor according to an embodiment of the present invention.

FIG. 2 schematically shows the front and back views of the sensor shown in FIGS. 1A and 1B together.

FIG. 3A schematically illustrates the area of the sensor shown in FIG. 2 in an enlarged scale.

FIG. 3B is a schematic cross-sectional view of a portion of the sensor shown in FIG. 3A.

3C and 3D schematically illustrate cross-sectional views of a portion of the sensor shown in FIG. 3B with the electric field lines resting thereon.

4A and 4B schematically illustrate a front view of a portion of a sensor according to another embodiment of the present invention.

5A and 5B schematically show a front view and a rear view of a two-dimensional capacitive position sensor according to another embodiment of the present invention, respectively.

6a schematically illustrates an electrical circuit for use with a sensor according to an embodiment of the invention.

FIG. 6B schematically illustrates the timing relationship between some elements of the circuit shown in FIG. 6A.

7 schematically illustrates a touch display screen including a sensor according to an embodiment of the present invention.

8 schematically shows a washing machine including a sensor according to an embodiment of the present invention.

9 schematically illustrates a mobile phone including a sensor according to an embodiment of the present invention.

10A and 10B schematically illustrate front and rear views of a two-dimensional capacitive position sensor according to another embodiment of the present invention, respectively.

11A and 11B schematically illustrate a front view and a rear view of a two-dimensional capacitive position sensor according to another embodiment of the present invention, respectively.

* Brief description of the major reference marks *

2: capacitive position sensor 4: board

6: drive unit 8: detection unit

10: sensor controller 14: ground shield

18: ground portion 20: drive wire

26,27: carbon pad

30: shorting connections 32: sensing wire

50: microcontroller 52: device controller

60: touch display 100: column electrode

101: driving channel 104: row electrode

105: capacitor 400: processing circuit

401: switch circuit 402: charge integrator

403: amplifier 404: reset switch

405: charge erasing means 407: measuring means

S1, S2, S3, and S4: Sense Channels

D1, D2, and D3: Drive Channels

The present invention relates to a capacitive touch sensor for detecting the presence of an object in a sensing area.

The use of capacitive touch sensors is becoming more and more common. Examples include the use of a touch sensor in a laptop computer instead of mouse pointing devices and as a control panel that receives user input for controlling both home and portable devices or home appliances.

Touch sensors are desirable for mechanical devices because they provide a more robust interface and are often considered aesthetically pleasing. In addition, since the touch sensor does not require any moving parts to allow the user to connect, it can be formed in the outer surface which is less wearable and sealed than the mechanical counterpart. It is especially used where there is a risk of dust or liquid entering the attractively controlled devices. Moreover, unlike the mechanical interface, the touch sensor can be transparent. The need for providing transparent sensors is increasing because transparent sensors can be used to provide a touch sensor that can display information to the user on the display and respond to the user pointing to a particular display area.

Known two-dimensional position sensors are described by the inventors of the present application in WO 00/44018 [1]. This position sensor has an array of N × M touch keys. Each key corresponds to the intersection between the drive electrode and the sensing electrode. An electric drive signal is applied to the drive electrode. The degree of capacitive coupling of the driving signal to the sensing electrode is determined by measuring the amount of change transmitted to the sensing electrode in response to the change in the driving signal. The degree of capacitive coupling between the electrodes at a given key depends on whether there are objects in the vicinity of the key, since the objects change the electric field pattern between the electrodes. Some objects, such as conductive water films, result in increased capacitive coupling. Other objects, such as those with significant capacitive coupling with the ground, allow to reduce capacitive coupling. This is because charge can be sucked into the ground through adjacent objects rather than through sensor electrodes.

The key array described in WO 00/44018 is a matrix array. This means that one driving electrode is combined with keys in a given column and one sensing electrode is combined with keys in a given row. This reduces the number of drive channels and sense channels needed, since one drive channel drives all keys in a given column simultaneously and one sense channel detects all keys in a given row. Capacitive coupling between electrodes at different key positions can be determined by driving the appropriate column and sensing the appropriate row. For example, in order to determine capacitive coupling between the electrodes coupled with the keys at the intersection of three rows and two columns, a driving signal is applied to the driving electrodes in two columns and the sensing channel coupled with the sensing electrodes in three rows is activated. . The output from the active sense channel reflects the capacitive coupling between the electrodes coupled with the key under test. It does not matter whether the drive signal is also applied to the other keys in the second column, since the rows associated with these keys are not detected. Similarly, it does not matter whether other keys in line 3 are detected, because these keys are not driven. In this way, other keys can also be scanned by sequencing through different combinations of drive and sense channels.

The two-dimensional position sensor described in WO 00/44018 is a robust and efficient device. However, an important feature of this type of position sensor that contributes to good performance is that during the transfer of charge from the driven electrode to the sensing electrode, the sensing electrode must appear as virtual ground. Each sense channel includes a charge detector to determine the amount of charge delivered in response to varying drive signals (ie, the degree of AC capacitive coupling). It is important for the sensing electrode to exhibit a low impedance node because the charge is efficiently sucked into the charge detector. When the sensing electrode does not exhibit a low input impedance, the charge flow induced in the sensing channel by the changing drive signal appears as a voltage pulse on the sensing electrode. This allows the sensor to sense "walk-by" interference from an object in the vicinity of the wiring connection between the sensing electrode and the charge detector. This is because an object near the wiring can absorb a portion of the signal from the wiring connection, reducing the signal supplied to the charge detector. This may appear in the control circuit as a reduction in capacitive coupling (ie, a detection event) in the key, even if the object is closer to the connection than near the sensor electrode. Thus, a hand reaching across the connection of one row of electrodes to activate another row of keys may result in an error output. Moreover, when the sense channel has significant input impedance, the length of the wiring used in the sensor is a factor in determining the circuit gain. This is because the wiring capacitively "bleed off" part of the sense signal to free space, adjacent wires and ground to form a capacitance drive circuit with capacitive coupling between the keys.

The low impedance characteristic of the charge detection circuit used in WO 00/44018 indicates that the problem noted above is reduced. However, the most transparent electrical conductors (eg, indium tin oxide (ITO)) that can be used to form drive electrodes and sensing electrodes in position sensors of the type described in WO 00/44018 are transparent touch sensors because they have a higher resistance than copper wires. Problems arise with For example, 300 ohms per area is typical for optimal transparent ITO films. This means that unlike materials such as copper, transparent conductors generally cannot be formed from a bonded connection with an electrode and negligible resistance (for a thickness that remains at least substantially transparent). Thus, even if the charge detection circuitry itself exhibits an appropriately low impedance, the material itself (and any combined wiring traces made of the same material), which is itself a row of drive electrodes and rows of sensing electrodes, may not have a low impedance. Thus, a device of the type described in WO 00/44018 in which the electrodes are formed by resistive conductors (eg transparent conductors) is difficult to implement easily.

Moreover, in many touch panel designs, the parallel ability to sense capacitive touch keys adjacent to the touch screen area is of considerable importance. Panel keys of this kind are described in WO 00/44018, which substantially combines touch buttons on the dielectric surface using copper or other materials, low resistance connections. The desire to include both low resistance connections with high resistance transparent conductor connections usually requires the performance of two different types of use or capacitive circuits, which can lead to circuit design problems.

The present invention is to solve the above problems, an object of the present invention is to provide a touch sensor excellent in the performance of the capacitive circuit while using a high resistance transparent electric conductor.

In order to achieve the above object, according to the first aspect of the invention embodied and broadly described herein, a substrate, a first resistance electrode on one side of the substrate, and a second resistance electrode on the other side of the substrate And a shorting connection configured to connect between at least two positions on the first electrode.

The sensor can be operated as an active sensor or a passive sensor. When the sensor is operated as an active sensor, provision of a shorting connection is shown by the electrodes to drive a signal applied to one or the other of the first and second electrodes to help reduce the impedance. This allows charge to be coupled more efficiently through the sensor, reducing the voltage difference between each electrode and the coupled circuit. This means that the effect of walk-by interference, which can occur normally if the sensor does not represent a low impedance node as a drive signal, can be reduced. Therefore, when the substrate and the electrode are transparent, the reduced sensitivity of the walk-by interference can be provided to the transparent sensor even though the electrodes are resistive. When the sensor is operated as a passive sensor (eg using a sensor channel coupled to both the first and second electrodes), the reduction in resistance of the electrodes due to the provision of a shorting connection equally reduces the effect of work-by interference Let's do it.

In general, the first electrode (i.e., one electrode combined with the short-circuit connection) becomes an electrode having the largest total resistance. This depends on the arrangement of the resistive material forming each electrode. However, the sensor may have another shorting connection configured as necessary to connect between two positions on the other electrode (i.e., a shorting connection is provided for both the first and second electrodes).

The electrodes may be arranged in a pattern to provide an array of opening regions on one side of the substrate and an array of filling regions on the other side, the filling regions arranged to align with the opening regions. This causes the electric field to spread in all directions from the region between the electrodes. This allows an object that changes the electrical properties in the region of the electric field to spread in all directions (eg by providing a virtual ground) to be detected by changing the capacitive coupling between the electrodes.

In the case of an active sensor, a drive channel operable to apply an electric drive signal to the sensor to one of the first or second electrodes (hence referred to as a drive electrode) and the other of the first and second electrodes There can be provided a combined circuit having a sensing channel operable to detect (detect) an electrical signal induced in (also referred to as a sensing electrode).

The drive channel can include a switch element that can be operable to selectively connect and disconnect the drive electrode from a voltage source. The sensing channel may have a charge transfer circuit.

In the case of a passive sensor, the sensor may be provided with a combined circuit having a sensing channel operable to detect charges in the capacitance of each electrode with respect to ground.

The sensor may have one or more electrodes on the face of the substrate with the first electrode and / or one or more electrodes on the face of the substrate with the second electrode, thereby forming a plurality of sensor regions (keys).

When one or more electrodes are formed on one or the other side of the substrate, the electrodes may be arranged in a matrix array such that circuit elements coupled to the electrodes (eg, drive and sense channels of an active sensor) are provided on one or more keys. To be.

According to a second aspect of the invention, there is provided a control panel comprising a sensor of the first aspect of the invention and a cover panel overlying the sensor. This allows the sensor to be protected during use.

The control panel may further comprise at least one low resistance electrode formed of copper, for example, to provide a conventional capacitive touch key coupled to the sensor of the first aspect of the invention. A single controller can be used to control the operation of the sensors of the first aspect of the present invention and conventional capacitive touch keys.

The cover panel and the sensor may be attached to each other by an adhesive having the same refractive index. This allows the sensor and cover panel to maintain transparent optical transparency.

Moreover, the control panel may have a display screen under the sensor. Thus, a touch type display can be formed. The display screen and the sensor may also be attached to each other by an adhesive with a matched refractive index.

According to a third aspect of the invention, there is provided an apparatus comprising the control panel of the second aspect of the invention.

Reference is made to the accompanying drawings by way of example to show a better understanding of the invention and how the invention can be achieved.

1A and 1B schematically show a front view and a rear view of a two-dimensional capacitive position sensor 2 according to an embodiment of the present invention. The terms front and back are used for reference to facing surfaces of the sensor 2 for convenience and are not intended to indicate any particular spatial direction. The term front is generally used to identify the sensor surface facing the object being sensed when the sensor is in normal use. However, it is recognized that in many cases the sensor can write on both sides.

The sensor 2 has a substrate 4 on which patterns of electrodes are deposited on both sides forming together the sensing area of the sensor. Patterning of the electrodes on the substrate can be accomplished using the prior art. The substrate 4 is a transparent plastic material, in this case polyethylene terephthalate (PET). The electrode is a transparent conductive material, in this case ITO. Thus the overall sensing area is transparent and can be used on the underlying display without blurring. The sensor is further provided on one side, in this case a drive unit 6 for supplying a drive signal to the electrode on the front side (FIG. 1A) of the substrate 4, and on the other side of the substrate 4, in this case the back side ( And a sensing unit 8 for sensing signals from the electrodes in FIG. 1 b). The sensor 2 further includes a sensor controller 10 coupled to both the drive unit 6 and the sensing unit 8. The sensor controller 10 processes the response from the sensing unit to control the operation of the drive unit and the sensing unit and to determine the position of the object adjacent to the sensor. The drive unit 6, the sensing unit 8 and the sensor controller 10 are shown schematically in FIGS. 1A and 1B as separate elements. However, the functionality of these devices is generally provided by a single integrated circuit chip, such as a suitably programmed general purpose microprocessor or field programmable gate array (FPGA), or application specific integrated circuit.

The electrode patterning of the substrate front side (FIG. 1A) has three “column” electrodes X1, X2, and X3. These electrodes run vertically with respect to the direction shown in FIG. 1A and are spaced horizontally from each other (the terms vertical and horizontal, top and bottom, etc., as used herein, unless otherwise noted, are used in the sensor shown in FIGS. 1A and 1B). The terms are not intended to indicate any particular orientation of the sensor when in normal use, and the terms rows and columns are generally used to refer to vertical and horizontal alignment for convenience). Each of the column electrodes X1, X2, and X3 is formed of an electrically continuous region of ITO in which a plurality of diamond-shaped opening regions (i.e., regions without any ITO in front of the substrate) are formed on the substrate. The opening area of each electrode of the column electrodes is arranged in four vertically arranged horizontal bands in which each band has openings of four rows and nine columns. Electrode patterning on the front of the substrate also includes a ground shield 14. It is formed as a region of continuous ITO that extends horizontally along the top edge of the column electrodes and extends to the region between the column electrodes. The ground shield is connected to the system ground 18 (ie, system reference potential). The ground shield may help to reduce crosstalk between different column electrodes during use, but may be omitted as needed.

The column electrodes X1, X2, and X3 are connected to the respective drive channels D1, D2, and D3 in the drive unit 6 via the drive wires 20. Thus, the column electrodes are sometimes referred to as driven electrodes or drive electrodes. In this example, each drive channel is provided to each column electrode. However, a single drive channel may also be used using appropriate multiplexing. The drive channel is controlled by the controller 10 to apply a drive signal to each column electrode of the column electrodes as described in further detail below. The drive wire includes a conventional copper wire (eg, ribbon connectors) connected to the ITO column electrodes via a carbon pad 26. The drive wire 20 is shown schematically in FIG. 1A and generally good performance can be achieved when drive wires combined with other electrodes are the same length, as this can help minimize the performance difference between channels. to be. In some examples, the drive wires may be formed with ITO traces on the substrate connected to the drive channel through an edge connector. However, conventional wiring has the advantage of providing a lower resistance drive wire.

The electrode patterning on the back side of the substrate (FIG. 1B) has four rows of electrodes Y1, Y2, Y3 and Y4 running horizontally and spaced vertically from each other. Each row electrode Y1, Y2, Y3 and Y4 is formed of an electric continuous region made of ITO. The row electrodes Y1, Y2, Y3 and Y4 are each formed to have a pattern repeated three times along the length in combination with three column electrodes X1, X2 and X3 on opposite sides of the substrate 4. The repeating pattern has four subrows of ITO aligned with each one of the four rows of diamond shaped openings in the corresponding one of the four bands of the openings in the ITO forming the column electrode. Each of the subrows includes nine filled regions in which the ITO forming the row is filled in a diamond shape corresponding to and aligned with each one of the opening regions on opposite sides of the substrate. In this case, the filling region in one subrow is only in contact with the filling region in a neighboring subrow, but this is not important. The ends of each row electrode are connected together by low-resistance shorting connections 30 formed by a connection running out of the sensing area through the carbon pad 27. In this example, the disconnect connection 30 includes a conventional copper wire (eg, ribbon connector) connected to the end of each row electrode via a carbon pad 27.

The row electrodes Y1, Y2, Y3 and Y4 are connected to the respective sensing channels S1, S2, S3, and S4 in the sensing unit 8 via the sensing wire 32. Thus, the row electrode is sometimes called the sensing electrode. Although each sense channel is formed for each electrode in this example, it can also be used as a single sense channel using the appropriate multiplexing with the drive channel. The sense channel is controlled by the controller 10 to measure the response signal from each one of the row electrodes as described in more detail below. The sensing wire 32 has a conventional copper wire connected to the short circuit connection 30. Therefore, the sensing channel is connected to both ends of the respective column electrodes through the low resistance connection formed by the combination of the sensing wire and the shorting connection.

The particular configuration shown in FIG. 1B, which uses a shorting connection 30 between the sensing wire 32 and each column electrode end connecting the shorting connection to the sensing channel, merely connects the sensing channel to both ends of each column electrode. It can be seen that one way to connect to. For example, the same result can be achieved using a connection that extends directly from each sensing channel to the two ends of the combined row electrodes.

Along with the drive wire 20 shown in FIG. 1A, the sense wire 30 is schematically shown and is generally better when the connection combined with other electrodes is the same length to help minimize the performance difference between the channels. Performance can be achieved. In some embodiments, the connection between the sense channel and the row electrode ends may be formed in whole or in part through traces on the substrate. You can do this by forming traces of the ITO (probably made thicker than in the transparent area of the sensor to reduce resistance), but it is generally this point to use silver ink traces, which is a silver ink. This is because the trace generally has a lower resistance. However, in this case conventional copper wire is used to connect the sensing channel to the row electrode, which also has the advantage of providing a lower resistance connection than can be achieved in general using ITO.

FIG. 2 schematically shows a plan view of the sensor 2 shown in FIGS. 1A and 1B, with the electrode patterning on both the front (FIG. 1A) and the back (FIG. 1B) shown together. The electrode patterning on the back side of the substrate is shown as being at the top in FIG. 2 (ie, looking behind the substrate). FIG. 2 shows written diamond shaped regions in the row electrodes on the back side (FIG. 1B) over opposing openings in the column electrodes on the front side (FIG. 1A). In FIG. 2, the drive unit 6, the sensor unit 8 and the sensor controller 10 are shown as subunits of a single microcontroller 50 providing the functionality of all three of these elements. In addition, the sensor controller receives position information (that is, a signal P _xy indicating the calculated position of the detected object in the sensing area) and takes appropriate action in response to the measured position to output the control signal C. A device controller 52 is shown to control the device.

3a schematically illustrates an enlarged portion of the sensor shown in FIG. 2. In particular, the sensor region shown by dashed line R in FIG. 2 is shown. FIG. 3A further illustrates how each diamond-shaped region in the row electrode on the back side of the substrate (FIG. 1B) is aligned with a corresponding one of the diamond-shaped opening regions in the column electrode on the front side (FIG. 1A). It is clearly shown. The opening regions in the column electrode are schematically shown in dotted lines, slightly smaller than the regions filled in diamond form in the row electrode so that the opening regions are more clearly seen in the figures. In particular, the areas to be filled and corresponding opening areas can be arranged to be substantially the same to overlap more closely.

FIG. 3B schematically shows a cross-sectional view of the area of the sensor 2 taken along the line AA ′ shown in FIG. 3A. The cross-sectional view also shows other elements coupled with the sensor 2 to form the touch display 60 and an object whose position is sensed (in this case, a user's finger with capacitance C _x relative to ground). Doing. 3b shows a front view of the sensor 2 at the top.

3B shows a touch display 60 with multiple layers, which are labeled L1 through L7 downward from the user side. The sensor element described above comprises layers L3, L4, and L5. Layer L4 is a substrate and layers L3 and L5 are ITO deposits on the front and back sides of the substrate, respectively. Layer L5 (rear-FIG. 1B) shows a carbon pad 27 connecting the row electrode to the short-circuit connecting portion 30. Adjacent to this carbon pad is a continuous portion of ITO running along the column electrode at a location taken through section AA '. The continuous portion of this ITO is schematically shown as alternating dark line portion 68 and crosshair portion 70. The dark line portion 68 corresponds to the regions filled in diamond form and the crosshairs portion 70 corresponds to the portions of the sub-row of the row electrode in which the cross section is connected between the regions filled in diamond form. Layer L3 shows the ITO deposition pattern on the front of the substrate shown in FIG. 1A. The cross-sectional view shown in FIG. 3B passes through many diamond shaped openings and layer L3 has cross sections with alternating crosshair regions 60 with ITO and non-hatched regions 62 without any ITO on the surface of the substrate. It is shown. It can be clearly seen from FIG. 3b that the areas filled with diamonds on the back of the substrate 4 (layer L5) are aligned with the diamond shaped openings on the front.

Layer L1 of touch display 60 is, for example, a cover panel of glass or plastic material that protects the sensor during use. The cover panel may include graphic decals as necessary. Layer L2 is an adhesive layer for bonding the sensor 2 to the cover panel. Layer L7 is a display screen, such as a liquid crystal display panel. Layer L6 is an adhesive layer that bonds the sensor (and attached cover panel) to the display screen. It may be beneficial to match the refractive indices of the ITO and cover panel / display screen cover for each adhesive layer to improve transparency.

Each intersection point between the row electrode and the column electrode can be considered to correspond to the individual sensor area (key) of the position sensor 2. Thus, the position sensor 2 has twelve keys arranged in four rows and three columns. In use, the sensor can be operated in the same manner as described in WO 00/44018, the content of which is incorporated herein by reference. Whether the object is adjacent or not, the given height is determined by examining the capacitive coupling between the row and column electrodes that intersect to define the key. Therefore, in order to determine whether an object is adjacent to the upper left key shown in FIG. 2, the driving channel D1 coupled to the column electrode X1 and the sensing channel S1 coupled to the row electrode Y1 are activated.

In operation, the drive channel D1 applies a time variable drive signal to the column electrode X1. The drive channel D1 is powered from the conventionally regulated power source and supplied to the sensor controller 10 to provide a plurality of periodic voltage pulses of a selected period (or one transition from low-high voltage or high-low voltage in simple implementation). It can be a simple CMOS logic gate controlled by. Alternatively, the drive channel may comprise a sine generator or a periodic voltage generator with another suitable waveform. Thus, a changing electric field is generated at the rising and falling boundaries of the series of voltage cycles applied to the driving column electrode X1. Column electrode X1 and row electrode Y1 operate as opposite plates of a capacitor with capacitance C _E. The capacitance C _E is mainly determined by the overlapping region between the column electrode X1 and the row electrode Y1 (that is, at the position of the key formed by the insertion of these electrodes). This is because the electrodes are closest to each other. Thus, the row electrode Y1 is capacitively coupled to the driven column electrode X1 to receive or suck in the changing electric field generated by the driven column electrode. This causes a current flow in the row electrode Y1 generated by the changing voltage on the column electrode X1 driven through the capacitance difference of the changing electric fields. The current flows to both ends of the row electrode Y1 (or from both ends depending on the polarity) and through the appropriate short circuit connection 30 and the sensing wire 32 to the sensing channel S1 of the sensing unit 8. The sense channel has a charge measuring circuit configured to measure the amount of charge to / from the sense channel (according to polarity) caused by the current induced in the row electrode Y1.

The capacitance difference is caused by the equation that determines the amount of current through the capacitor:

Where I _E is the instantaneous current in the sense wire 32 and dV / dt is the rate of change of the voltage applied to the driving column electrode X1. The amount of charge coupled (and to / from sense channel S1) to row electrode Y1 during the boundary transition is the integral of the equation over time. In other words,

The combined charge Q _E at each transition is independent of the rise time of V (i.e. dV / dt), and the voltage swing at the driven column electrode (which can be easily fixed) and the driven column electrode It only depends on the magnitude of the coupling capacitance C _E between the sensing row electrode and the sensing row electrode. Thus, the measurement of the combined charge to / from the detector with a charge detector having a sense channel S1 in response to a change in the drive signal applied to the column electrode X1 results in a coupling between the driven column electrode X1 and the sense row electrode Y1. It is a measurement of capacitance C _E.

The capacitance of a conventional parallel capacitor is almost independent of the electrical properties of the region out of the space between the plates (at least for plates somewhat larger than the spacing). However, the coupling of the gaps in the ITO between the diamond-shaped openings in the column electrode and the other subrows in the row electrode results in at least a portion of the electric field connecting between the column electrode X1 and the row electrode Y1 "spread in all directions" from the substrate. Means that. This is due to the electrical properties of the region near the point of intersection of the electrodes (ie the location of the key) where the electric field in which the capacitive coupling (i.e., the magnitude of C _E ) between the driven column electrode and the sense row electrode is "spread in all directions" is expanded. To be sensitive enough.

In the absence of adjacent objects, the size of C _E is mainly determined by the geometry of the column and row electrodes in the overlapping region (with respect to the respective openings), the thickness of the substrate 4 and the dielectric constant. However, if the object is in an area in which the electric field spreads in all directions past the cover panel with layer L1 in FIG. 3B through the gap in the ITO, the electric field in this area can be altered by the electrical properties of the object. This changes the capacitive coupling between the electrodes and thus changes the combined charge to / from the charge detector with the sense channel. For example, if a user places a finger on a space area occupied by a portion of the electric field spread in all directions, the user may have a significant outage to the ground (or another adjacent structure whose path terminates at the ground reference potential of the circuit controlling the sensing element). Having a capacitance reduces the capacitive coupling of charge between the electrodes. This reduced coupling occurs because an electric field spreading in all directions, normally coupled between the driven column electrode and the sense row electrode, is in the portion that radiates from the column electrode to the ground. This is because the object adjacent to the sensor acts to repel the electric field from the direct coupling between the electrodes.

3C and 3D schematically show cross-sectional views of the sensor 2 area, in which electric field lines connecting the driving electrode and the sensing electrode are schematically shown. This figure is similar to FIG. 3B and can be seen from FIG. 3B, but only parts of layers L3 (front ITO), L4 (substrate) and L5 (back ITO) are shown for simplicity. 3C shows the electric field when no object is adjacent to the sensor. FIG. 3d shows the electric field when there is an object adjacent to the sensor (ie, the finger of the user with capacitance C _E with respect to ground). If no object is adjacent to the sensor, all electric field lines are connected between the two electrodes. However, when the user's finger is adjacent to the sensor, a portion of the electric line of force passing out of the substrate is coupled to the ground plane through the finger. Thus, few electric field lines are connected between the electrodes and capacitive coupling between the electrodes is reduced. The effect is the same as that used in US 5,648,642 [4].

Thus, by monitoring the amount of charge coupled between the driving column electrode X1 and the sensing row electrode Y1, a change in the amount of charge coupled between the electrodes can be identified and the object is adjacent to the key (i.e., the electric field spreading in all directions). Are used to determine whether the electrical properties of the region in which they extend vary. For example, upon initial driving of the sensor 2, the sensor controller 10 can measure the charge transferred between the column electrode and the row electrode at each key position for a given drive signal. This can be taken to be the reference signal level S _ref for each key. During operation, the sensor controller can subsequently determine (scan) the capacitive coupling at each key position by activating the appropriate column and row electrodes. The measured amount of charge delivered to each key S _meas is then compared with the reference signal level S _ref for that key to determine whether it has changed significantly, for example, by at least the stunned threshold signal amount S _th . Can be. If the charge is greater than S _th , the sensor controller determines that the object is adjacent to the associated key and outputs a detection event by outputting the appropriate signal P _xy indicating the position of the object (ie, adjacent to any key located). 52). The sensor controller can also examine the magnitude of the change in the amount of charge delivered to the keys near the key displaying a change above the threshold such that the touch position can be interpolated at a better resolution than the size of the individual keys.

You will notice that you do not need to scan the keys one by one. When each sensing channel is associated with each row electrode, all rows can be sensed simultaneously when one column electrode is driven so that all keys in a given column can be examined simultaneously.

The sensitivity of the position sensor depends on the extent to which the electric field spreads in all directions from the region between the row and column electrodes (i.e., outside of the substrate 4). This can alter the electrical properties of the object adjacent to the substrate (possibly through the cover panel) to change the electric field connecting between the drive row electrode and the receive row electrode and thus the capacitive coupling between the electrodes. In the example, the position sensor 2 described above is the driven row electrode surface of the substrate which faces the user during normal use. Thus, the amount of electric field starting or ending (depending on polarity) in the diamond-filled areas of the row electrode spreads in all directions through the corresponding diamond-shaped openings in the column electrode that determine the sensitivity of the sensor. In order to improve the sensitivity, it is possible to ideally select the electrode pattern on the user side of the substrate having a relatively small ITO area where most of the area is taken as the opening area. However, this is possible with conventional opaque conductors, but not with transparent conductors of higher resistance because the electrode structures with sparse networks of resistive conductor materials are too resistive. As described above, if the output of the drive channel "sees" too large an impedance, the reliability and response characteristics of the sensor may be significantly degraded. Thus, it is important to find a balance between the dense pattern of ITO (which provides a low resistance electrode) and the aperture pattern (which provides good sensitivity).

In this example, the electric field spreading in all directions through the diamond-shaped openings in the column electrode is altered by an adjacent object, but the row electrodes on opposite sides of the substrate have narrower traces of the row electrodes of ITO. Note that it has the greatest resistance. Therefore, in this example, the row electrodes are most benefited by the short circuit connection. The column electrode itself has a relatively large portion of ITO. However, a relatively large amount of ITO on the front of the substrate limits the geometry of the ITO patterning (ie, row electrode) that can be used on the back side of the substrate. This is because it is important to reduce the substrate area having ITO at the same position on the opposite face. This is because these areas of the electrode are capacitively coupled to each other to reduce the amount of electric field that can spread in all directions through the opening area. The need for the ITO with drive and sense electrodes to minimize the areas on both sides of the substrate is at the heart of the need to balance the tight pattern of the resistive conductor with the opening pattern. The effect of the resistance of the row electrodes on the impedance seen in the drive channel can be reduced by connecting both ends of the row electrodes to the sense channel using a low resistance connection, for example using the shorting wire shown in FIG. If only one end of each row is connected to the sense channel, the measurement of the capacitive coupling coupled to the keys at the other end may be affected by the total electrical resistance of the electrode. However, by connecting both ends of the electrode to the sense channel, the amount of current coupled with the keys at both ends of the electrode has a relatively direct (ie low resistance) connection to the sense channel. Moreover, the amount of current from the keys in the middle of the row electrode can flow in both directions along the electrode to the sense channel. Thus, the maximum contribution to the impedance of the sensor generated by the electrode itself is reduced by four factors compared to the case without any short circuit connection. This means that the point with the largest resistance moves from one end of the electrode to the middle (and thus the largest resistance is halved), and the two halves of the electrode connect the intermediate point in parallel to the measurement circuit, thus again This is because it has a large resistance. This allows position sensors based on resistive conductors (ie generally transparent conductors) on opposite sides of the substrate to be provided with sufficiently low electrode resistances that a reliable position sensor can be formed (if considered necessary, It is appreciated that connecting wires can be used between both ends of the driving column electrodes).

The diamond shaped pattern is a combination of electrode patterning of this type and similar patterns based on circular or rectangular regions, for example, as schematically illustrated in FIGS. 4A and 4B (similar to FIG. 3A and known from FIG. 3A). One particular example, and it will be appreciated that many other configurations can be used equally.

5A and 5B schematically illustrate front and rear electrode patterns used in a sensor according to another embodiment of the present invention. These figures are similar to FIGS. 1A and 1B and are understood from FIGS. 1A and 1B. However, FIGS. 5A and 5B show sensors with different configurations of keys. Rather than the four-row, three-column array sensor shown in Figures 1A and 1B, the sensor has three keys in the upper two rows and four keys in the lower one row. The keys are based on the same diamond shaped pattern as the pattern described above. The electrode patterning coupled to the keys in the bottom row is smaller in size but this is not critical. This embodiment shows an example of how the designer of the control pad according to the invention has considerable freedom in determining how much he wishes to arrange the keys.

6A schematically illustrates a circuit that can be used to measure the charge transferred from the column electrode 100 to the sensing row electrode 104. Circuits of this type are described in more detail in WO 00/44018. The capacitive coupling between column electrode 100 and row electrode 104 is schematically illustrated as capacitor 105. The circuit is based in part on the charge transfer ("QT") apparatus and method disclosed by the inventor in US Pat. No. 5,730,165 [2], the contents of which are incorporated herein by reference.

The driving channel coupled with the column electrode 100, the sensing channel coupled with the sensing row electrode 104, and the elements of the sensor controller are illustrated as a processing circuit 400. The processing circuit 400 includes a sampling switch 401, a charge integrator 402 (shown here as a simple capacitor), an amplifier 403 and a reset switch 404, and also an optional charge erasing means 405. It may be provided. The timing relationship between the column electrode drive signal from the drive channel 101 and the sample timing of the switch 401 is schematically illustrated in FIG. 6B. The drive channel 101 and the sampling switch 401 are provided with suitable synchronization means, which may be a microprocessor or other digital controller 408 to maintain this relationship. In the implementation shown, reset switch 404 is initially closed to reset charge integrator 402 to a known initial state (eg, 0 volts). Then, the reset switch 404 is opened, and after a while, the sampling switch 401 passes through the terminal 1 of the switch during the time interval during which the drive channel 101 indicates a positive transition. It is connected to charge integrator 402 and then reconnected to terminal 0, which is an electrical ground or other suitable reference potential. At this time, the drive channel 101 returns to ground, and the process is repeated again for a total of 'n' cycles, where n is 1 (i.e., 0 iterations), 2 (1 iterations), 3 (2 times) Repeat), etc.). It is important that the drive signal does not return to ground before the charge integrator is disconnected from the row electrode, otherwise the same charge and the opposite charge may flow into / out of the sense channel during the positive and negative traveling boundaries, thus providing This is because no net transfer or net charge can occur. Following a predetermined number of cycles, the sampling switch 401 is held at the zero position, while the voltage for the charge integrator 402 is measured by the measuring means 407, which is measured at the amplifier, ADC or at any time in the application. Other circuits may be provided that may be appropriate. After the measurement has been made, the reset switch 404 is closed again and the cycle is then restarted if necessary, for example momentarily or after a delay suitable for the controlled device. The process is referred to herein as the measurement 'burst' of length 'n', where 'n' can range from 1 to any infinite number. The sensitivity of the circuit is directly proportional to 'n' and inversely proportional to the value of the charge integrator 402.

It will be appreciated that the circuitry indicated at 402 provides a charge integration function that can also be achieved by other means, and the present invention is not limited to the use of a ground reference capacitor as shown at 402. It is also apparent that the charge integrator 402 may be an integrator of an operational amplification series for integrating the charge flowing in the sensing circuit. This integrator also uses a capacitor to store the charge. It can be noted that the integrator adds to the complexity of the circuit but provides a more ideal summing junction load and more dynamic range for the sense current. If a slow summer is used, it may be necessary to use each capacitor at position 402 to temporarily store charge at high speed until the integrator can absorb within the time limit, Compared to the value of the integrating capacitor, the value of such a capacitor becomes relatively insignificant.

If the row electrode is not connected to the charge integrator 402 during the change of the drive signal for the selected polarity (in this case, the positive polarity), the sampling switch 401 causes the sensor's sensing row electrode to connect to ground. Is useful. This can create an artificial ground plane, thereby reducing RF emissions and also allowing the combined charge of the polarity opposite to the polarity sensed by the charge integrator 402, as mentioned above, to be properly distributed and neutralized. In addition, a resistor can be used to ground to the row electrode lines to achieve the same effect between switching of drive channel 101. As an alternative to a single SPDT switch 401, two separate switches may be used if timed in an appropriate manner.

As described by the inventors in US Pat. No. 5,730,165, there are many signal processing options that may be present for manipulation and determination of detection or measurement of signal amplitude. US 5,730,165 also describes the gain relationship of the device shown in FIG. 6A, although for a single electrode system. In this case, the gain relationship is the same. The use of the signal erasing means 405 is described by the inventor in US 5,730,165 as well as US 4,879,461 [3]. The disclosure of US 4,879,461 is incorporated herein by reference. The purpose of signal cancellation is to reduce the voltage (i.e., charge) buildup on the charge integrator 402, which occurs simultaneously with the occurrence of each burst, thereby making the coupling between the driving column electrode and the receiving row electrode larger. One advantage of this approach is to enable a large sensing area that is sensitive to small variations in coupling between electrodes at a relatively low cost. This large sense coupling appears on the physically large electrodes commonly used in human touch sensing pads. Charge erasing allows the measurement of the amount of coupling with greater linearity, which causes the charge coupled to the sense row electrode 104 from the driving column electrode 100 to be sucked into the 'virtual ground' node through a burst process. It is because of the ability to enter. If the voltage on the charge integrator 402 is to be increased significantly during the burst process, the voltage may increase in an inverted exponential form. This exponential component adversely affects linearity and thus the available dynamic range.

FIG. 7 schematically shows, in plan view, a control panel 80 comprising a touch type display 82 of the type described in FIG. 3B. The control panel 80 is mounted to the controlled device, in this case the wall 84 of the washing machine. The cover panel 92 of the touch display 82 extends over the entire area of the control panel with the area occupied by the positioned touch display, in this example near the middle of the control panel. The touch display, for example, has a number of menu buttons labeled A to F corresponding to different washing programs that can be selected, variable parameters such as sliding scale 94 defining the washing temperature, and information. It is shown in FIG. 7 with a display showing several lines of characters 96 displayed to the user. Thus, the user can select the washing program by touching the control panel in the menu button area labeled A to F, for example. A sensor with a touch display can be configured such that the position of the menu buttons A through F corresponds to the "key" position (ie, the intersection area between the column and row electrodes) in the sensor. Alternatively, the menu buttons A to F may not be directly related to the arrangement of the keys underneath the sensor and may be arbitrarily defined. If arbitrarily defined, the touch position in the sensing area can be determined by interpolation of signals from many keys, and then the position is compared with the position of the displayed menu button to determine whether one has been selected. The selection of the temperature from the sliding temperature scale 82 displayed to the user can also be done in the same way.

In addition to the touch display 82, the control panel also includes many additional buttons 86 and on / off switches 88. These may be touch keys or conventional mechanical button switches. In this example, they are touch keys that preserve the flat, sealed outer surface of the control panel. In this case, since the additional button does not need to be transparent, the button does not need to be formed of ITO. Thus, inexpensive and low resistance coins can be used for these buttons. Moreover, a single sensor controller integrated circuit chip can be used to control the position sensor with a transparent sensor and more conventional coin touch buttons 86,88. This can be achieved, for example, by making appropriate adjustments to the different channels of a single controller chip taking into account the different resistances and loads of the ITO thin film and the coin electrode.

Accordingly, designers will have considerable freedom in designing a control panel that includes a transparent touch position sensor and will recognize that the principles described above can be applied to many types of devices / devices. For example, similar sensors include ovens, grills, washing machines, tumble dryers, dishwashers, microwave ovens, food blenders, bread makers, beverage vending machines, computers, and home audiovisuals. It can be used with equipment, portable media players, PDAs, mobile phones, computers and the like. For example, FIG. 8 schematically shows a washing machine 91 including a sensor 93 according to an embodiment of the invention, and FIG. 9 shows a sensor 99 and a screen 97 according to an embodiment of the invention. A schematic illustration of a mobile phone 95 is included. More generally, the present invention can be used in conjunction with any device having a human-machine interface. It is also possible to provide sensors similar to the above kind provided separately from the device / apparatus which can be used for control. For example, upgrades can be provided to existing devices. It is also possible to provide a comprehensive sensor that can be configured to operate devices in other areas. For example, the sensor has a given range of keys that allow the device / device provider to properly configure the controller, such as by reprogramming the functions of the desired device.

10A and 10B schematically illustrate front and rear views of respective two-dimensional capacitive position sensors 110 according to another embodiment of the present invention. This can be used for example in a cooker control panel. The sensor 110 is similar to the sensor shown in FIGS. 5A and 5B in that it forms the same array of keys. That is, the sensor 110 has three keys in the upper two rows and four keys in the lower one row. However, electrode patterning for keys is different. The keys of the sensor shown in Figs. 5A and 5B are based on the overlapping opening area and the filling area of the diamond pattern, and each row electrode is formed of four sub-rows of conductive material. However, the keys of the sensor 110 shown in FIGS. 10A and 10B are based on a pattern having a slot-shaped area with rounded ends, and each row electrode has a single row of conductive material. Also in this embodiment, the openings in the column electrode comprise a region of conductive material 11. These areas are electrically insulated from the surrounding electrode material and do not affect the way the sensor operates. However, from an aesthetic point of view, it may be better to include the area of the conductive material 111 in the transparent sensor because it may help make the conductive material layer with the electrode less visible to the user due to more uniform covering. . Both ends of each row electrode are connected together by a short-circuit connecting portion 130 similar to the above-described short-circuit connecting portion.

Despite the differences in the specific patterns of conductive materials forming the electrodes, the sensors 110 shown in FIGS. 10A and 10B generally operate in the same manner and can be seen from the sensors shown in FIGS. 1A and 1B. . Accordingly, drive unit 116 and sensor controller 110 are also shown in FIG. 10A. The drive unit 116 differs from the drive unit 6 shown in FIG. 1A in that it has four drive channels D1, D2, D3, and D4 (as opposed to three). This is because one of the rows of keys of the sensor 110 (i.e., the bottom row for the direction shown in FIG. 10A) has four key areas and four drive channels are required to provide this row. Likewise, FIG. 10B shows the sensing unit 118 and also the sensor controller 110. The sensor unit operates in the same way and is understood from the sensor unit 8 shown in FIG. 1B.

The sensor controller 110 operates in a broadly identical manner as the sensor controller 10 shown in FIGS. 1A and 1B. However, the difference in the combined key arrangement means that other logic is needed to determine if the key is in contact. For the sensor 110 shown in Figs. 10A and 10B, if a signal is detected by the sensing channel S1 or S2 (upper two rows), the selected key region determines which of the driving channels D1, D3, and D4 is activated. (Drive channel D2 cannot generate a supervisory signal on sense channel S1 or S2 because the column electrode connected to drive channel D2 does not overlap with the row electrode connected to these sense channels). On the other hand, if a signal is detected by the sense channel S3 (lower row), the selected key region depends on which of the drive channels D1, D2, D3, and D4 is activated.

11A and 11B schematically illustrate front and rear views of the two-dimensional capacitive position sensor 210 according to another embodiment of the present invention, respectively. The sensors shown in FIGS. 11A and 11B operate in the same manner as the sensors shown in FIGS. 1A and 1B but are based on different key configurations. In this case, six rows and eight columns of key arrays (48 key areas in total) are formed. Accordingly, the corresponding drive unit (not shown) has eight row drive channels coupled to eight column electrodes and the corresponding sense unit (not shown) has six sense channels coupled to six row electrodes. As in the above-described embodiment, the touch position is determined from the intersection of the column electrode connected to the active drive channel and the sensing electrode connected to the sensing channel for recognizing the signal.

In addition to the increased number of rows, the electrode pattern for the sensor 210 shown in FIGS. 11A and 11B is characterized by the sensor 2 shown in FIGS. 1A and 1B in that the column electrodes are not insulated by ground shielding. Is different from the electrode pattern. Further, the keys of the sensor shown in FIGS. 1A and 1B are based on the opening area and the filling area of the diamond-shaped pattern, each row electrode formed of three sub-rows of conductive material. However, the keys of the sensor 210 shown in FIGS. 11A and 11B are based on connected rectangular shaped openings and filling regions, each row electrode being only one (in contrast to many sub-rows) of conductive material. It has only rows of.

Both ends of each row electrode shown in FIG. 11B are connected together by a shorting connection 230 similar to and understood from the shorting connection described above. In addition, the end of each column electrode shown in FIG. 11A is also connected together by a short circuit connecting portion 240. These are used to reduce the electrical impedance appearing in the drive channel in the same way that the shorting connection 230 between the two ends of the two electrodes is used to reduce the electrical impedance appearing in the sense channel. This is particularly useful for relatively large area sensors or sensors with narrow key areas, since the resistance of the row electrodes as well as the column electrodes can be quite large. Thus, the sensor 210 shown in FIGS. 11A and 11B may be particularly suitable for touch sensors that may be used in larger touch sensors, for example, point of sale terminals measuring on the order of 16 cm x 12 cm. Can be.

While the above describes sensors in terms of driving column electrodes and sensing row electrodes, they can be reversed without changing the basic principles of operation. For example, the sensor 2 shown in FIG. 2 can be operated equally by connecting a row electrode to a drive channel and a column electrode to a sense channel. Moreover, the substrate 4 can be changed such that the side referred to above is arranged on the side facing the user of the substrate during normal use. However, it will be appreciated that the degree of spread of the electric field cannot be the same on either side of the substrate, as it is generally due to electrode patterning on either side. Thus, an electrode pattern with the largest degree of spread that would be on the surface of the substrate facing an object (eg, a user's finger or piercing needle) sensed during normal use may be beneficial. It has also been found experimentally that improved sensitivity can be achieved when the sensing electrode is positioned on the surface of the substrate facing the object being sensed during normal use. For example, the measured signal intensity doubled compared to the case where the driving electrodes faced the detected object.

Moreover, rather than depending on the transmitting and receiving device (i.e., the device using the driving electrode and the sensing electrode), the above-described substrate, electrode patterning and short-circuit connection arrangements can also be used in passive configuration. That is, rather than having a drive channel for applying a drive signal to the drive electrode and a sense channel for detecting a detection signal induced by the drive signal by the drive signal, each electrode (eg, as described in US Pat. No. 5,730,165). It can be connected to a single electrode capacitive sensing channel. In this arrangement, each row electrode and column electrode separately senses the position of the object along two corresponding directions. For example, referring to the embodiment illustrated in FIGS. 5A and 5B, the three column electrodes of FIG. 5A and the three row electrodes of FIG. 5B may be connected to the same single electrode capacitive sensing channel. Thus, the signal connected to the column electrode of FIG. 5A can be used to identify the touch position in the horizontal direction, while the signal connected to the row electrode of FIG. 5B can be used to identify the object position in the vertical direction.

Finally, although the term “touch” is frequently used in the above description, the sensor of the type described above is such that it can record the position of an adjacent finger (or other object such as a needle) without requiring physical contact. It may be sensitive enough. Therefore, the term "touch" as used herein should be interpreted accordingly.

Reference

[1] WO 00/44018 (Harald Philipp)

[2] US 5,730,165 (Harold Philip)

[3] US 4,879,461 (Harold Phillips)

[4] US 5,648,642 (Synaptics Inc.)

The effect of the capacitive touch sensor according to the present invention described above is as follows:

First, the capacitive touch sensor of the present invention is provided with a transparent substrate and a transparent electrode, and although the transparent electrodes are high resistance, the effect of the work-by interference is reduced by the reduction in the resistance of the electrodes due to the provision of the short-circuit connection. There is an advantage to reducing.

Second, the electrodes of the present invention may be arranged in a pattern to provide an array of opening regions on one side of the substrate and an array of filling regions on the other side, the filling regions arranged to align with the opening regions so that the electric field is It spreads in all directions from the area between them, and when the object is adjacent, there is an advantage of accurately measuring the position of the object due to the capacitance difference between the electrodes.

Claims (20)

Substrate, A first resistance electrode on one side of the substrate, A second resistance electrode on the other side of the substrate, And a shorting connection configured to connect between at least two positions on the first resistance electrode. The method of claim 1, And a short circuit connection portion configured to connect between at least two positions on the second resistance electrode. The method according to claim 1 or 2, One of the first and second resistive electrodes is arranged in a pattern with an array of opening regions, and the other of the first and second resistive electrodes is configured to be aligned with the opening regions. Capacitive sensors arranged in a pattern with an array of. The method of claim 3, wherein And a region disposed in the opening regions and formed of the same material as the electrodes electrically insulated from the resistance electrodes. The method according to any one of claims 1 to 4, The resistive electrodes are transparent capacitive sensor. The method according to any one of claims 1 to 5, A capacitive sensor wherein the substrate is transparent. The method according to any one of claims 1 to 6, And at least one further electrode on the same substrate surface as the first resistance electrode. The method of claim 7, wherein And a ground electrode disposed between the first resistance electrode and the at least one other electrode. The method according to any one of claims 1 to 8, And at least one further electrode on the same substrate surface as the second resistance electrode. The method of claim 9, And a ground electrode disposed between the second resistance electrode and the at least one other electrode. The method according to any one of claims 1 to 10, And at least one further electrode on the same substrate surface as the first resistive electrode and at least one other electrode on the same substrate surface as the second resistive electrode, wherein the electrodes are arranged in a matrix array. The method according to any one of claims 1 to 11, A driving channel operable to apply an electrical drive signal to one of the first or second resistance electrodes and an electrical sensing signal to the other of the first or second resistance electrodes in response to the drive signal. Capacitive sensor with a sensing channel capable of. The method of claim 12, And the drive channel comprises a switch element operable to selectively connect and disconnect the coupled electrodes to the voltage source. The method according to claim 12 or 13, The sensing channel has a charge transfer circuit. The method according to any one of claims 12 to 14, The sensing channel is connected to an electrode on the side of the substrate facing the object being sensed during normal use. A control panel comprising a sensor according to any one of claims 1 to 15 and a cover panel overlying the sensor. The method of claim 16, The cover panel and the sensor is a control panel attached to each other by the adhesive with the same refractive index. The method according to claim 16 or 17, And a display screen under the sensor. The method of claim 18, And the display screen and the sensor are attached to each other by an adhesive having a matching refractive index. 20. An apparatus comprising a control panel according to claim 16.

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