JP2007086075A - Capacitive contact sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a capacitive contact sensor provided with a first resistive electrode on one side of a substrate, a second resistive electrode on the other side of the substrate, and a short-circuit connection connected between at least two positions on the first electrode. <P>SOLUTION: A capacitive sensor for determining the presence of an object, such as a finger of a user and a stylus, is provided with the substrate formed of a transparent plastic material, such as PET, and the electrodes are attached thereon. The resistive drive electrode formed of, for example, a transparent ITC is arranged in one face of the substrate, and the resistive perceptual electrode that is formed and maybe of the same transparent ITC is arranged in the other face of the substrate. A transparent sensor is thereby provided as a whole. The short circuit connection is provided to be connected between the two positions on the first electrode. The electrodes are connected, respectively, to a driving channel and a perceptual channel. A low-resistance connection is provided between the position on one of the electrodes and the drive channel or the perceptual channel corresponding thereto, by providing the short circuit connection between the two positions on the the other electrode (or both electrodes). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a capacitive contact sensor for detecting the presence of an object in a perceptual region.

  The use of touch sensitive sensors is becoming increasingly popular. Examples of the use of touch sensitive sensors include the use of touch sensors in place of mouse positioning devices in laptop computers, and as control panels for receiving user input and controlling both stationary and portable devices or equipment. There is use.

  Touch sensitive sensors are often preferred over mechanical devices because they provide a more robust interface, and aesthetics are often considered more preferred. Also, the touch sensitive sensor requires no moving parts that can be accessed by the user, so it wears less than a mechanical sensor with the same function and can be provided in a sealed external surface. . This makes the use of touch sensitive sensors particularly attractive when there is a risk of dust or fluid entering the controlled device. Also, unlike a mechanical interface, it is possible to construct a transparent touch sensitive sensor. Transparent sensors can be used on the display to provide a touch-sensitive screen that can display information to the user and respond to the user pointing out a specific area of the display. The desire to provide is increasing.

  A known two-dimensional position sensor is described in Patent Document 1 by the present inventor. This position sensor comprises an array of N × M touch keys. Each key corresponds to the intersection of a drive electrode and a sensory electrode. An electric drive signal is applied to the drive electrode. The degree of capacitive coupling of this drive signal to the sensory electrode is determined by measuring the amount of charge transferred to the sensory electrode in response to changes in the drive signal. Since the electric field pattern between electrodes changes depending on the object that exists in the vicinity of a specific key, the degree of capacitive coupling between the electrodes of a given key depends on the presence of the object in the vicinity of that key. It depends on. Certain objects, such as conductive water films, increase capacitive coupling. Humans with significantly greater capacitive coupling to other objects, such as ground, will reduce capacitive coupling. This is due to charge sinking to ground through an adjacent object, not through the sensory electrode.

An array of a plurality of keys described in Patent Document 1 is a matrix array. This means that a single drive electrode is associated with multiple keys in a given column, and a single sensory electrode is associated with multiple keys in a given row. Because a single drive channel drives all keys in a given column simultaneously and a single sensory channel perceives all keys in a given row, this matrix array requires the drive channels and The number of perceptual channels is reduced. Capacitive coupling between electrodes at different key positions can be determined by driving the appropriate column and perceiving the appropriate row. For example, column 2 while the sensory channel associated with the sensory electrode in row 3 is active to determine capacitive coupling between the electrodes coupled to the key at the intersection of column 2 and row 3. A drive signal is applied to the drive electrodes. The output from the active sensory channel reflects the capacitive coupling between the electrodes that are coupled to the key under investigation. Since the rows associated with the other keys in column 2 are not perceived, it is not a problem that drive signals are applied to these keys. Similarly, because the other keys in row 3 are not driven, it is not a problem that these keys in row 3 are perceived. This method allows different keys to be scanned sequentially through different combinations of drive and sensory channels.
International Publication No. WO00 / 44018 US Pat. No. 5,648,642 US Pat. No. 5,730,165 U.S. Pat. No. 4,879,461

  The two-dimensional position sensor described in Patent Document 1 is a robust and effective device. However, an important feature contributing to its good performance of this type of position sensor is that the sensory electrode must appear as a virtual ground while the charge is moving from the drive electrode to the sensory electrode. . Each of the sensory channels includes a charge detector for determining the amount of charge transferred in response to the changing drive signal (ie, the degree of AC capacitive coupling). The sensory electrode provides a low impedance node, which is important because it allows the charge detector to efficiently sink charge. If the sensory electrode does not provide a low input impedance, the charge flow induced in the sensory channel by the changing drive signal will appear at the sensory electrode as a voltage pulse. This voltage pulse appearing at the sensory electrode makes the sensor sensitive to “walk-by” interference by objects present in the vicinity of the wiring connection between the sensory electrode and the charge detector. This is because an object in the vicinity of the wiring absorbs a part of the signal from the wiring connection, so that a signal supplied to the charge detector is reduced. This may appear in the control circuit as a reduction in key capacitive coupling (ie, a detection event) even when the object is not in the vicinity of the sensory electrode but adjacent to the wire. Thus, an incorrect output will be provided by a hand reaching across one row of electrode wiring to activate another row of keys. Also, if the sensory channel has a significantly large input impedance, the length of the wiring used for the sensor is a factor that determines the gain of the circuit. This is due to the fact that part of the perceptual signal capacitively “bleeds off” to free space, adjacent wiring and ground by the wiring, thus forming a capacitive voltage divider circuit with capacitive coupling between keys. Is.

  The low impedance characteristic of the charge detection circuit used in Patent Document 1 means that the problem described above is reduced. However, most transparent electrical conductors (eg, indium tin oxide (ITO)) that can be used to form drive and sensor electrodes for position sensors of the type described in US Pat. The resistance is high compared to, which raises a problem in the context of transparent contact sensors. For example, an optimal transparent ITO film is typically 300 ohms per square. Unlike materials such as copper, this generally does not allow transparent conductors to be formed on electrodes and associated wiring where resistance can be ignored (at least with a thickness that remains substantially transparent) Is not possible). Thus, even though the charge detection circuit itself can provide a suitable low impedance, the materials that make up the drive electrode columns and sensory electrode rows themselves (and any associated wiring traces made of the same material) are low. Impedance cannot be provided. Therefore, the type of device described in Patent Document 1 in which electrodes must be formed using a resistive conductor (for example, a transparent conductor) is difficult to implement with high reliability.

  Also important in many touch panel designs is the similar ability to perceive capacitive touch keys adjacent to the touch screen area. These types of panel keys are substantially described in U.S. Patent No. 6,057,096, together with a dielectric surface contact button using copper or other metal low resistance wiring. The desire to incorporate both low resistance wiring and high resistance transparent conductor wiring usually results in circuit design problems that require the use of two different types of capacitive circuits or capacitive circuits with two different performances ing.

  According to the first aspect of the invention, the substrate, the first resistive electrode on one side of the substrate, the second resistive electrode on the other side of the substrate, and at least on the first electrode A capacitive sensor is provided with two locations and a short circuit connection adapted to connect between the locations.

  This sensor can be operated as an active sensor or a passive sensor. When operating this sensor as an active sensor, the provision of a short-circuit connection facilitates the reduction in impedance provided by the electrode that drives the signal applied to one of the first and second electrodes. . Thus, charge can be more effectively coupled through the sensor, thus reducing the voltage difference between the individual electrodes and the associated circuitry. This generally means that the effect of walk-by interference that occurs when the sensor does not provide a low impedance node in the drive signal can be suppressed. Therefore, when the substrate and the electrode are transparent, it is possible to provide a transparent sensor that is less sensitive to walk-by interference despite the electrode being resistive. When operating this sensor as a passive sensor (for example, a sensor with a sensory channel coupled to both the first and second electrodes), it is also possible to reduce the impedance of the walk-by interference by providing a shorted connection. The effect is suppressed.

  Usually, the first electrode (that is, the electrode coupled to the short-circuit connection) is the electrode having the largest total resistance. This is determined by the placement of the resistive material forming the individual electrodes. However, this sensor was adapted to connect between two locations on the other electrode as needed (ie, both the first electrode and the second electrode are provided with shorting electrodes). Like) Other short-circuit connections can be provided.

  The electrodes are in a pattern in which an array of open areas is provided on one side of the substrate and an array of fill areas arranged in alignment with the open areas on the other side of the substrate. Can be arranged. By arranging in this way, the electric field can overflow from the region between the electrodes. Thus, capacitive coupling between the electrodes can be changed to an object that changes the electrical properties of the region where the electric field overflows (eg, by providing a virtual ground), thus allowing detection.

  In the case of an active sensor, this sensor has a drive channel that can be operated to apply an electrical drive signal to either the first or second electrode (and thus this electrode can be referred to as the drive electrode). The associated circuitry provided and the electrical signal induced on the other of the first and second electrodes in response to the drive signal (thus, this electrode can be referred to as the sensory electrode) A sensory channel that can be operated as follows:

  The drive channel can comprise a switch element that can be operated to selectively connect the drive electrode to the voltage source and to selectively release the drive electrode from the voltage source. The sensory channel can comprise a charge transfer circuit.

  In the case of a passive sensor, the sensor can comprise an associated circuit with a sensory channel that can be operated to detect changes in the capacitance of individual electrodes relative to ground.

  The sensor can comprise a plurality of electrodes on the surface of the substrate having the first electrode and / or can comprise a plurality of electrodes on the surface of the substrate having the second electrode, and thus a plurality of sensor regions. (Key) can be provided.

If multiple electrodes are provided on either side of the substrate, these electrodes can be arranged in a matrix array so that circuit elements associated with these electrodes (eg, active sensor drive and sensor channels) ) Can serve multiple keys.

  According to a second aspect of the present invention there is provided a control panel comprising a sensor according to the first aspect of the present invention and a cover panel covering the sensor. Thus, the sensor can be protected during use.

  The control panel may further comprise at least one low resistance electrode for providing a conventional capacitive touch sensitive key, eg made from copper, in connection with the sensor according to the first aspect of the invention. . A single controller can be used to control the operation of the sensor according to the first aspect of the invention and the operation of a conventional capacitive touch sensitive key.

  The cover panel and sensor can be attached to each other using a refractive index matching adhesive. If the sensor and cover panel are transparent, maintaining using optical index transparency is facilitated by attaching using a refractive index matching adhesive.

  The control panel can also include a display screen covering under the sensor. Thus, a touch sensitive display screen can be provided. These display screens and sensors can also be attached to each other using a refractive index matching adhesive.

According to a third aspect of the present invention there is provided an apparatus comprising a control panel according to the second aspect of the present invention.
For a better understanding of the present invention and to illustrate the manner of carrying out the present invention, reference will now be made, by way of example, to the accompanying drawings in which:

  1A and 1B respectively show a schematic front view and a schematic rear plan view of a two-dimensional capacitive position sensor 2 according to an embodiment of the present invention. As used, the terms front and back refer to opposite surfaces of the sensor 2 for convenience and are not intended to imply any particular spatial orientation. The term front is generally used to identify the face of the sensor that faces the object to be perceived when the sensor is used in its normal state. However, it will be appreciated that in most cases the sensor is reversible.

The sensor 2 includes a substrate 4 on which both electrode patterns that together define a sensitive area of the sensor are arranged. This electrode pattern on the substrate can be obtained using conventional techniques. The substrate 4 is made of a transparent plastic material, in this case polyethylene terephthalate (PET). The electrode is made of a transparent conductive material, in this case ITO. The entire sensitive area is therefore transparent and can be used without blurring on the underlying display. The sensor further comprises a drive unit 6 for supplying drive signals to the electrodes on one side of the substrate 4, in this case the front side of the substrate 4 (FIG. 1A), and the other side of the substrate 4, in this case the substrate. A perception unit 8 is provided for perceiving signals from the electrodes on the back of the four (FIG. 1B). The sensor 2 further comprises a sensor controller 10 coupled to both the drive unit 6 and the sensory unit 8. The sensor controller 10 controls the operation of the drive unit and the sensory unit and processes the response from the sensory unit to determine the position of the object adjacent to the sensor. 1A and 1B, the drive unit 6, the sensory unit 8 and the sensor controller 10 are shown schematically as separate elements. In general, however, a single integrated circuit chip, such as a suitably programmed general purpose microprocessor or programmable gate
Arrays or dedicated integrated circuits can be used to provide the function of these elements.

  The electrode pattern on the front side of the substrate (FIG. 1A) comprises three “column” electrodes X1, X2 and X3. These columns run in the vertical direction and are spaced apart from each other in the horizontal direction with the orientation shown in FIG. 1A. (Terms such as vertical and horizontal, top and bottom as used herein indicate the orientation of sensor 2 shown in FIGS. 1A and 1B, unless otherwise required by context. These terms. Is not intended to indicate any particular orientation of the sensor when used in the normal state, and the terms column and row generally indicate vertical and horizontal alignment for convenience. Each of the column electrodes X1, X2 and X3 is formed from an electrically continuous ITO region. In this region, a plurality of rhombus open regions (that is, regions where ITO is not present on this surface of the substrate) are formed. The open areas in the individual column electrodes are arranged in the form of four horizontal bands displaced in the vertical direction, each band having 4 rows and 9 columns of openings. The electrode pattern on this surface of the substrate is provided with a ground shield 14. The ground shield 14 is formed from a continuous ITO region that extends in a horizontal direction along the top edge of the column electrode and extends in a region between the column electrodes. The ground shield is connected to system ground 18 (ie, system reference potential). The ground shield can assist in the suppression of crosstalk between different column electrodes during use, but can be omitted if necessary.

  The column electrodes X1, X2, and X3 are connected to drive channels D1, D2, and D3 in the drive unit 6 through drive wires 20, respectively. Therefore, the column electrode is sometimes called a driven electrode or a driving electrode. In this embodiment, a separate drive channel is provided for each column electrode. However, it is also possible to use a single drive channel with appropriate multiplexing. The drive channel is controlled by the controller 10 and applies a drive signal to the corresponding column electrode, as will be described further below. The drive wire comprises conventional copper wiring (eg, a ribbon connector) connected to the ITO column electrode via a carbon pad 26. Although drive wire 20 is shown schematically in FIG. 1A, typically the length of the drive wire associated with the different electrodes is similar, thereby minimizing performance differences between channels. Therefore, better performance can be obtained. In some embodiments, it is also possible to form drive wires from ITO traces on a substrate that are connected to drive channels via edge connectors. However, conventional wiring usually has the advantage of providing a drive wire with lower resistance.

  The electrode pattern on the back side of the substrate (FIG. 1B) comprises four “row” electrodes Y1, Y2, Y3 and Y4 that are horizontally spaced and spaced apart from each other in the vertical direction. Each of the row electrodes Y1, Y2, Y3, and Y4 is formed from an electrically continuous ITO region. The row electrodes Y1, Y2, Y3 and Y4 have a pattern in which each row electrode is repeated three times along its length in relation to the three column electrodes X1, X2 and X3 on the opposite side of the substrate 4 Is formed. This repeating pattern is aligned with the corresponding rows of the four rows of rhomboid open regions in the corresponding strips of the four strips of open regions in the ITO forming the column electrodes, respectively. It has two sub-ITO rows. Each of the four sub-rows includes nine filling areas, and ITO corresponds to and is aligned with the individual areas of the open area on the opposite side of the substrate. The rows are filled with diamonds. In this embodiment, the filling area from one sub-row will be in contact with the filling area from an adjacent sub-row, but this is not important. The ends of the individual row electrodes are connected together by a low resistance short-circuit connection 30 provided by wiring passing outside the sensitive area via carbon pads 27. In this embodiment, the short connection 30 comprises conventional copper wiring (eg, a ribbon connector) coupled to the ends of individual row electrodes via carbon pads 27.

  The row electrodes Y1, Y2, Y3 and Y4 are connected to the sensory channels S1, S2, S3 and S4 in the sensory unit 8 via sensory wires 32, respectively. Thus, the row electrodes are sometimes called sensory electrodes. In this embodiment, a separate sensory channel is provided for each row electrode, but as with the drive channel, it is also possible to use a single sensory channel with appropriate multiplexing. The sensory channel is controlled by the controller 10 to measure the response signal from the corresponding row electrode, as will be further described below. The sensory wire 32 comprises conventional copper wiring connected to the short-circuit connection 30. The sensory channels are therefore connected across the corresponding individual row electrodes via low resistance connections provided by a combination of sensory wires and short circuit connections.

  The particular configuration shown in FIG. 1B using a short circuit connection 30 between the end of each individual row electrode and the sensory wire 32 connecting the short circuit connection to the sensory channel, each sensor channel is associated with a corresponding row electrode. It will be appreciated that this is only one way to connect both ends. For example, the same result can be obtained using a connection going directly from an individual sensory channel to the two ends of the associated row electrode.

  As in the case of the drive wire 20 shown in FIG. 1A, the figure schematically shows a sensory wire 32, but typically the length of the wiring coupled to the different electrodes is similar, thereby Better performance is obtained if minimization of performance differences between channels is facilitated. In some embodiments, the connection between the sensory channel and the end of the row electrode can be formed in whole or in part from traces on the substrate. The formation of the connections from the traces on the substrate can be performed by forming the traces from ITO (in some cases they can be made thicker than the trace thickness in the transparent area of the sensor to reduce their resistance. However, it is generally advantageous to use silver ink printed traces because silver ink printed traces have lower resistance. However, in this embodiment, the perceptual channel and the row electrode are connected using conventional copper wiring. This connection also has the advantage of providing a lower resistance connection than is typically obtained using ITO.

FIG. 2 is a schematic plan view of the sensor 2 shown in FIGS. 1A and 1B, in which both front (FIG. 1A) and back (FIG. 1B) electrode patterns are shown together. The electrode pattern on the back of the substrate is shown at the top of the figure (ie, the figure is seen from the “back” of the substrate). This figure shows a method of superimposing the filled rhombus regions in the electrode rows on the back surface (FIG. 1B) and the openings facing each other in the column electrodes on the front surface (FIG. 1A). In FIG. 2, the drive unit 6, the sensory unit 8 and the sensor controller 10 are shown as subunits of a single microcontroller 50 that provides all the functions of these three elements. Also shown in FIG. 2 is a device coupled to the sensor by receiving position information from the sensor controller (ie, a signal P _xy representing the calculated position of the perceived object in the perceived region) and outputting a control signal C. A device controller 52 is shown that takes the appropriate action depending on the measured position to control.

  FIG. 3A is an enlarged schematic view of a part of the sensor shown in FIG. Specifically, a sensor region indicated by a dash line R in FIG. 2 is shown. FIG. 3A more clearly shows how to align the individual rhombus filling regions in the electrode rows on the back surface of the substrate (FIG. 1B) with the corresponding regions of the rhomboid open regions in the column electrodes on the front surface (FIG. 1A). ing. For clarity, the open area in the column electrode, whose outline is schematically indicated by a dashed line, is drawn slightly smaller than the diamond filled area in the row electrode. In practice, the filling area and the corresponding open area are arranged to have substantially the same extent so that they overlap more closely.

FIG. 3B is a schematic cross-sectional view of the same region of the sensor 2 shown in FIG. 3A taken along line AA ′. Also shown in this cross-sectional view are other elements in combination with the sensor 2 to provide a touch-sensitive display 60 and an object whose position is to be perceived (in this case a user's finger having a capacitance C _X to ground). It is shown. In the cross-sectional view of FIG. 3B, the uppermost front surface of the sensor 2 is shown.

FIG. 3B shows a touch-sensitive display 60 having a plurality of layers that are labeled L1 to L7 downward from the user side. The sensor element described above comprises layers L3, L4 and L5. Layer L4 is the substrate, and layers L3 and L5 are ITO deposits on the front and back of the substrate, respectively. Layer L5 (back side—FIG. 1B) shows a carbon pad 27 for connecting the row electrode to the short-circuit connection 30. Adjacent to this carbon pad 27 is a continuous cross section of ITO passing along the row electrode at the location of cross section AA ′. This continuous cross section of ITO is shown schematically with alternating black filled cross sections 68 and cross sections 70 with shaded shades. The cross-section 68 filled with black corresponds to the rhombus filling region, and the cross-section 70 with the shaded shade is the row electrode connecting the rhombus filling region and the rhombus filling region where the cross-section is taken. Corresponds to the sub-row part. Layer L3 shows the ITO deposition pattern on the front side of the substrate shown in FIG. 1A. The cross-sectional view shown in FIG. 3B shows an alternating cross section of the region 60 where the layer L3 is shaded and where the ITO is present, and a region where the ITO is not present on this side of the substrate which is not shaded. It passes through a number of rhombus open areas so that it can be seen that it has 62 alternating sections. From FIG. 3B, it can be clearly seen that the rhombus filled region on the back surface of the substrate 4 (layer L5) and the rhombus open region on the front surface are aligned.

  The layer L1 of the touch-sensitive display 60 is a cover panel made of, for example, glass or plastic material and protects the sensor during use. The cover panel can include a graphic decal if desired. Layer L2 is an adhesive layer that couples sensor 2 to the cover panel. Layer L7 is a display screen, for example a liquid crystal display panel. Layer L6 is an adhesive layer that couples the sensor (and the cover panel attached to the sensor) to the display screen. To improve transparency, it is advantageous to index match these adhesive layers with ITO and the cover panel / display screen cover.

  Each intersection of the row electrode and the column electrode can be regarded as corresponding to a discrete sensor region (key) of the position sensor 2. Therefore, the position sensor 2 includes 12 keys arranged in 4 rows and 3 columns. In use, the sensor can be operated in a manner similar to that described in US Pat. A given key is determined by examining the capacitive coupling between column and row electrodes that intersect to define the key, whether the object is adjacent or not adjacent Can do. Therefore, to determine whether the objects are adjacent, the top left key shown in FIG. 2, the drive channel D1 coupled to the column electrode X1 and the sensory channel S1 coupled to the row electrode Y1. Is activated.

When the drive channel D1 is activated, the drive channel D1 applies a drive signal that varies with time to the column electrode X1. The drive channel D1 may be a simple CMOS logic gate that is powered from a conventional regulated power supply and controlled by the sensor controller 10 to provide a plurality of periodic voltage pulses of a selected duration. Good (or in a simple implementation, it may be a single voltage change from low to high or from high to low). Alternatively, the drive channel may comprise a cycle voltage generator having a sine wave generator or other suitable waveform. Accordingly, a changing electric field is generated at the rising and falling edges of a series of voltage cycles applied to the driven column electrode X1. Column electrode X1 and row electrode Y1 act as opposing plates of a capacitor having capacitance _CE . Capacitance _CE is controlled primarily by the overlap region between column electrode X1 and row electrode Y1 (ie, the key position defined by the intersection of these electrodes). This is due to the closest approach of these electrodes in this region. Thus, the row electrode Y1 is capacitively coupled to the driven column electrode X1 and receives or sinks the changing electric field generated by the driven column electrode. As a result, a current induced on the driven column electrode X1 by a voltage that changes due to the capacitive differentiation of the changing electric field flows to the row electrode Y1. This current flows toward both ends of the row electrode Y1 (or from both ends of the row electrode Y1 depending on the polarity), and the perceptual channel in the perceptual unit 8 via the appropriate short-circuit connection 30 and the perceptual wire 32. Flows to (from) S1. The sensory channel comprises a charge measurement circuit adapted to measure the charge flowing into the sensory channel (or out of the sensory channel depending on the polarity) by the current induced in the row electrode Y1.

The capacitive derivative is an equation that controls the current flowing through the capacitor, that is,
_IE = _CE * dV / dt
Arises through. _IE is an instantaneous current flowing through the sensory wire 32, and dV / dt is a rate of change of the voltage applied to the driven column electrode X1. The amount of charge coupled to the row electrode Y1 during the edge change (and thus the amount of charge flowing into and out of the perceptual channel S1) is the integral over time in the above equation, ie
Q _E = C _E × V
It is.

The charge Q _E combined with each change is independent of the rise time of V (ie dV / dt), the voltage swinging at the driven column electrode (can be easily fixed), and the driven column It depends only on the magnitude of the coupling capacitance _CE between the electrode and the sensory row electrode. Accordingly, the determination of the charge coupled to / coupled from the charge detector with the perceptual channel S1 in response to changes in the drive signal applied to the column electrode X1 is determined by the driven column electrode X1 and the perceptual row. It is a measure of the coupling capacitance _CE between the electrodes Y1.

The capacitance of a conventional parallel plate capacitor is almost independent of the electrical properties of the area outside the space between the plates (at least for a plate whose extent is large compared to the distance separating the plates). However, the combination of the rhombic open area in the column electrode and the gap in the ITO between the different subrows in the row electrode is at least the electric field connecting between the column electrode X1 and the row electrode Y1. It means that a part "overflows" from the substrate. This is a region where capacitive coupling between driven column electrodes and perceptual row electrodes (ie, the magnitude of _CE ) develops an “overflowing” electric field near the intersection of these electrodes (ie, key position). This means that it is sensitive to some degree of electrical characteristics.

In the absence of any adjacent objects, the magnitude of _CE is mainly determined by their geometry in the region where the column and row electrodes overlap (considering their individual openings) and the thickness of the substrate 4. And the dielectric constant. However, if an object exists in a region where the electric field overflows through the gap in the ITO beyond the cover panel provided with the layer L1 shown in FIG. 3B, the electric field in this region varies depending on the electrical characteristics of the object. Will do. As a result, the capacitive coupling between these electrodes changes, which in turn changes the measured charge coupled to / coupled from the charge detector with the sensory channel. The user has a substantial capacitance to ground (or other structure in the vicinity where the path to the ground reference potential of the circuit controlling the sensory element is complete), for example, part of the overflow electric field When the user places his / her finger in the area of the space occupied by the electrode, the capacitive coupling of charges between the electrodes decreases. This reduction in capacitive capacitive coupling is caused by a change in the portion of the overflow electric field that is typically coupled between the driven column electrode and the sensory row electrode from the row electrode to ground. This is because the object adjacent to the sensor acts as a shunt that separates the electric field from the direct coupling between the electrodes.

3C and 3D show a region of the sensor 2 in a schematic cross-sectional view schematically showing the electric field lines connecting the drive electrode and the sensory electrode. These figures are similar to FIG. 3B and are therefore understood from FIG. 3B, but only a portion of layers L3 (front ITO), L4 (substrate) and L5 (rear ITO) are shown for clarity. Has been. FIG. 3C shows the electric field when there is no object adjacent to the sensor. FIG. 3D shows the electric field in the presence of an object adjacent to the sensor (ie, a user's finger having a capacitance C _X to ground). If there is no object adjacent to the sensor, all electric field lines connect between the two electrodes. However, if the user's finger is adjacent to the sensor, a portion of the electric field lines that pass outside the substrate are coupled to ground through the finger. For this reason, the electric field lines connecting the electrodes are reduced, and the capacitive coupling between them is reduced. This effect is similar to the effect described in Patent Document 2.

Thus, by monitoring the amount of charge coupled between the driven column electrode X1 and the sensory row electrode Y1, the change in the amount of charge coupled between them is identified and the change is used to It can be determined whether or not it is adjacent to the key (ie, it can be determined whether or not the electrical characteristics of the region where the overflow electric field has developed) have changed. For example, when the sensor 2 is initially started up, the sensor controller 10 can measure the electric charge moved between the column electrode and the row electrode in response to a given drive signal for each key position. The measured result can be used as the reference signal level S _ref for each key. During operation, the sensor controller can continuously determine (ie, scan) capacitive coupling for each key position by activating the appropriate column and row electrodes. Next, the moving charge amount S _meas measured for each key is compared with the reference signal level S _ref of the key, and whether or not the measured moving charge amount S _meas has changed greatly, for example, at least a predetermined threshold signal amount S _th You can only determine if it has changed. If the change is greater than _Sth , the sensor controller determines that the object is adjacent to the key and an appropriate signal representing the position of the object (ie, a signal representing the position of the key adjacent to the object). ) Instruct detection event to device controller 52 by outputting P _xy . In addition, the sensor controller can investigate the magnitude of the change in the amount of mobile charge in the vicinity of the key that indicates a change that exceeds the threshold, and therefore interpolates the touch position to a better resolution than the size of the individual keys. be able to.

  It will be understood that it is not necessary to sequentially scan the keys one by one. When individual perceptual channels are coupled to individual row electrodes, it is possible to perceive all rows simultaneously with driving a single column electrode so that all keys of a given column can be examined simultaneously. it can.

The sensitivity of the position sensor is determined by the degree of electric field overflowing from the region between the row electrode and the column electrode (that is, the region outside the substrate 4). This is to the extent that the electric field connecting the driven column electrode and the receiving row electrode varies with the electrical properties of the object placed adjacent to the substrate (possibly through a cover panel), By extension, the degree of capacitive coupling between them is defined by the electric field overflowing from the region between the row and column electrodes. In the case of the embodiment of the position sensor 2 described above, it is the driven column electrode side of the substrate that faces the user during normal use. Thus, the sensitivity of the sensor is determined by the amount of electric field starting from the rhomboid filling region in the row electrode, which overflows through the corresponding rhomboid open region in the column electrode, or terminates in the rhomboid filling region (polarity Is the amount of electric field. In order to improve the sensitivity, the electrode pattern on the user side of the substrate is ideally selected with a relatively narrow ITO area and a large area occupied by the open area. However, it is possible to select an ideal electrode pattern using a conventional non-transparent conductor, but an electrode structure that has only a sparse network of resistive conductor material becomes extremely resistive, In the case of a more resistive transparent conductor, it is impossible to select an ideal electrode pattern. As explained above, if the output of the drive channel “shows” an extremely large impedance, the reliability and response characteristics of the sensor will be significantly reduced. It is therefore important to find a balance between dense ITO patterns (providing low resistance electrodes) and open patterns (providing good sensitivity).

In the above example, it is the electric field that overflows through the rhombic open area in the column electrode that changes with adjacent objects, but it has the narrowest ITO trace that has the greatest resistance. Note that the row electrodes are on the opposite side of the substrate. Therefore, in this embodiment, it is the row electrode that makes the most effective use of the short-circuit connection. The column electrode itself has a relatively wide ITO cross section. However, the relatively large amount of ITO on the front side of the substrate limits the geometry of the ITO pattern that can be applied to the back side of the substrate (ie, the row electrodes). This is because it is important to reduce the area of the substrate having ITO at the same position on both sides. This is due to the fact that these regions of the electrode are strongly capacitively coupled to each other, thereby reducing the amount of electric field that can overflow through the open region. The need to minimize the area where ITO with driven and sensory electrodes is present on both sides of the substrate is at the core of the need to balance between dense and open patterns of resistive conductors. Yes. The effect of the row electrode resistance on the impedance provided to the drive channel is reduced by connecting the ends of the row electrode to the sensory channel using low resistance wiring, such as the shorting wire shown in FIG. 1B. If only one end of an individual row is connected to the sensory channel, the capacitive coupling measurement that couples with the key at the other end will be affected by all the electrical resistances of that electrode. However, by connecting both ends of the electrode to the sensory channel, the current that couples with the key at both ends of the electrode has a relatively direct connection to the sensory channel (ie, has a low resistance). . Furthermore, current flowing from the center key of the row electrode can flow to the sensory channel in both directions along the electrode. Therefore, the maximum contribution to the sensor impedance caused by the electrode itself is reduced to ¼ compared to the case where there is no short circuit connection. This is because the point with the highest resistance moves from one end of the electrode (and hence the electrode with the highest resistance) to the center, and both halves of the electrode parallel the center point to the measurement circuit. This is because the maximum resistance is further halved. Therefore, a position sensor based on resistive conductors (that is, typically transparent conductors) on both sides of the substrate can have a sufficiently small electrode resistance, and thus a highly reliable position sensor can be provided. (It will be understood that if necessary, similar short-circuit connection wires may be used between the ends of the driven column electrodes.)
The rhombus pattern is only one specific example of this type of electrode pattern, and similar patterns based on circular or square areas, for example as schematically shown in FIGS. 4A and 4B, can equally be used (these Is similar to FIG. 3A, and therefore will be understood from FIG. 3A), and it will be appreciated that many other configurations can be used equally well.

  5A and 5B schematically show a front electrode pattern and a back electrode pattern used in a sensor according to another embodiment of the present invention. These figures are similar to FIGS. 1A and 1B and will therefore be understood from FIGS. 1A and 1B. However, FIGS. 5A and 5B show sensors with different key arrangements. This sensor has two upper rows of three keys and a single lower row of four keys, rather than a 4 × 3 array of sensors shown in FIGS. 1A and 1B. These keys are based on a rhombus pattern similar to the keys described above. The electrode pattern associated with the key in the lower row is drawn on a smaller scale, but this is not important. This embodiment is an example showing how many degrees of freedom the designer of the control panel according to the present invention has when determining the key layout desired by the designer.

FIG. 6A schematically illustrates a circuit that can be used to measure the charge traveling from the column electrode 100 to the sensory row electrode 104. This type of circuit is described in more detail in US Pat. Capacitive coupling between the column electrode 100 and the row electrode 104 is shown schematically by a capacitor 105. This circuit is based, in part, on the charge transfer (“QT”) device and method disclosed by the present inventor in US Pat.

  The drive channel associated with the column electrode 100, the sensory channel associated with the sensory row electrode 104, and the sensor controller element are shown as an overall processing circuit 400. The processing circuit 400 comprises a sampling switch 401, a charge integrator 402 (shown here as a simple capacitor), an amplifier 403 and a reset switch 404, and optionally a charge cancellation means 405. It is also possible. FIG. 6B schematically shows the timing relationship between the column electrode drive signal from the drive channel 101 and the sample timing of the switch 401. The drive channel 101 and the sampling switch 401 are provided with suitable synchronization means. This synchronization means may be a microprocessor or other digital controller 408 to maintain this relationship. In the illustrated embodiment, the reset switch 404 is initially closed to reset the charge integrator 402 to a known initial state (eg, zero volts). The reset switch 404 is then opened, and after some time, the sampling switch 401 is connected to the charge integrator 402 via the sampling switch terminal 1 for a certain interval. During that interval, the drive channel 101 changes positive and then reconnects to terminal 0, which is electrical ground or other suitable reference potential. The drive channel 101 then returns to ground and the method is repeated again for a total of “n” cycles (n is 1 (ie, 0 iterations), 2 (1 iteration), 3 (2 iterations). And so on). It is important that the drive signal does not return to ground until the charge integrator is released from the row electrode, otherwise equal and opposite charge is applied to the sensory channel during positive and negative rises. Inflow / outflow from the sensory channel, and thus no net movement or charge to the charge detector will be provided. When the desired number of cycles is completed, the sampling switch 401 is held in position 0 and the voltage of the charge integrator 402 is measured by the measuring means 407. The measuring means 407 can comprise an amplifier, ADC or other circuit to suit the application at hand. When the measurement is complete, the reset switch 404 is closed again and the cycle is restarted, for example immediately after the next need, or after a delay appropriate to the device to be controlled. This method is referred to herein as a measurement “burst” of length “n”. “N” can range from 1 to any finite number. The sensitivity of the circuit is directly proportional to “n” and inversely proportional to the value of the charge integrator 402.

  The circuit element shown 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 shown at 402 Will be understood. It will also be apparent that an operational amplifier based integrator that integrates the charge flowing through the sensory circuit can be used for the charge integrator 402. A capacitor for accumulating electric charge is also used for such an integrator. Note that the integrators add complexity to the circuit, but these integrators provide a more ideal summing connection load for the perceptual current and provide a more dynamic range. When using a slow integrator, a separate capacitor is sometimes used at position 402 to temporarily store charge at high speed until the integrator can eventually absorb the charge. However, the value of such a capacitor is less important compared to the value of the integrating capacitor incorporated in the operational amplifier based integrator.

If the sensor's sensory row electrodes are not connected to the charge integrator 402 while the drive signal of the selected polarity (in this case, positive rising) is changing, the sampling switch 401 will connect these sensory row electrodes to ground. It is useful to connect. This can create a pseudo-ground plane by connecting the sensory row electrodes to ground, thus suppressing RF emissions and, as pointed out above, the polarity of the charge perceived by the charge integrator 402 Is due to the ability to appropriately dissipate and neutralize the binding charge of opposite polarity. It is also possible to obtain the same effect between changes of the drive channel 101 by using a resistance to ground on the row electrode line. It is also possible to use two independent switches as an alternative to a single SPDT switch 401 if timed in an appropriate manner.

  There are many possible signal processing options for manipulating and determining the detection or measurement of the magnitude of the signal, as described in US Pat. Patent Document 3 describes the gain relationship of the structure shown in FIG. 6A, although it is in the form of a single electrode system. The gain relationship in this case is the same. The usefulness of the signal canceling means 405 is described in Patent Document 4 and Patent Document 3 by the present inventor. The disclosure of Patent Document 4 is incorporated herein by reference. The purpose of signal cancellation is to suppress the voltage (ie, charge) stored in the charge integrator 402 at the same time as the generation of individual bursts (positive rising changes in the drive channel), thereby driving the column electrodes and receiving rows. To allow a stronger bond between the electrodes. One advantage of this approach is that it allows a large perceived area that is sensitive to small changes in the coupling between electrodes at a relatively low cost. Such strong sensory coupling is physically present in large electrodes typically used in human touch sensory pads. The linearity of the measurement is determined by the ability to sink the charge coupled from the driven column electrode 100 to the perceptual row electrode 104 to the “virtual ground” node while the burst is in progress, so by canceling the charge, The amount of binding can be measured with excellent linearity. If the voltage of the charge integrator 402 can be increased somewhat while the burst is in progress, this voltage will rise inversely. This exponential component has a detrimental effect on linearity and therefore has a detrimental effect on the available dynamic range.

  FIG. 7 shows a schematic plan view of a control panel 80 incorporating a touch-sensitive display 82 of the type described with reference to FIG. 3B. This control panel 80 is attached to the wall 84 of the device to be controlled, in this case attached to the washing machine. The cover panel 92 of the touch-sensitive display 82 extends over the entire area of the control panel, and the area occupied by the touch-sensitive display is located near the center of the control panel in this embodiment. The touch-sensitive display shown in FIG. 7 includes a number of menu buttons labeled A to F, for example corresponding to different selectable washing programs, and a slide for defining a variable parameter, for example washing temperature. A scale 94 and several lines of text 96 that provide information to the user. Thus, the user can select a laundry program by touching the control panel in the area of the menu button, for example labeled A to F. A sensor with a touch-sensitive display can be configured such that the position of the menu buttons AF corresponds to the position of the “key” in the sensor (ie, the area of intersection between the column and row electrodes). . Alternatively, the menu buttons A-F need not be directly associated with the key structure that underlies the sensor, but can be arbitrarily defined. In the latter case, the touch position in the sensitive area can be determined from interpolation of signals from a number of keys, and then the menu button is compared by comparing the determined position with the displayed menu button position. It can be determined whether or not is selected. Selection of the temperature from the slide temperature scale 94 displayed to the user can also be performed in the same manner.

In addition to the touch-sensitive display 82, the control panel further includes a number of additional buttons 86 and on / off switches 88. These may be touch sensitive keys or conventional mechanical button switches. In this embodiment, these are touch sensitive keys that maintain a flat and sealed exterior surface of the control panel. In this case, the additional buttons do not need to be transparent, so they need not be formed from ITO. Therefore, cheaper and less resistive copper electrodes can be used for these buttons. In addition, a single sensor controller integrated circuit chip can be conveniently used to control position sensors with transparent sensors and more conventional copper electrode touch sensitive buttons 86,88. This can be achieved, for example, by properly calibrating the different channels of a single controller chip and taking into account the different resistances and loading of the ITO film and copper electrode.

  Thus, designers have many degrees of freedom in designing control panels that incorporate transparent touch-sensitive position sensors, and the principles described above can be applied to many types of devices / equipment. It will be understood that it can be done. For example, oven, grill, washing machine, tumble dryer, dishwasher, microwave oven, food blender, bread maker, drink machine, computer, home audiovisual equipment, portable media player, PDA, cell phone, computer A similar sensor can be used for the above. For example, FIG. 8 schematically illustrates a washing machine 91 incorporating a sensor 93 according to one embodiment of the present invention, and FIG. 9 illustrates a cellular telephone 95 incorporating a sensor 99 according to one embodiment of the present invention. And schematically shows a screen 97. More generally, the present invention can be used with any device having a human-machine interface. It is also possible to provide sensors similar to these types described above, which can be used to control them, provided separately from devices / equipment, for example to upgrade existing equipment. Is possible. It is also possible to provide a general purpose sensor that can be configured to operate a series of different devices. For example, a sensor can be coupled to the functionality of the device as desired by the device / equipment supplier by appropriately configuring the controller, for example, by reprogramming the device / equipment supplier. Has a range of keys.

  10A and 10B schematically show a front view and a rear plan view of a two-dimensional capacitive position sensor 110 according to another embodiment of the present invention. This two-dimensional capacity position sensor can be used for a cooker control panel, for example. This sensor 110 is similar to the two-dimensional capacitive position sensor shown in FIGS. 5A and 5B in that it provides the same key structure. That is, sensor 110 has two upper rows of three keys and a lower single row of four keys. However, the key electrode pattern is different. The key of the sensor shown in FIGS. 5A and 5B is based on a rhombus pattern in which an open region and a filling region are superimposed, and individual row electrodes are formed from four sub-rows of conductive material. However, the key of the sensor 110 shown in FIGS. 10A and 10B is based on a pattern with areas in the form of round slots, and the individual row electrodes comprise a single row of conductive material. Moreover, in this embodiment, a region 111 of conductive material is included in the opening in the column electrode. These regions are electrically isolated from the surrounding electrode material and thus do not affect the manner of operation of the sensor. However, from an aesthetic point of view, the more uniform covering facilitates the construction of a layer of conductive material with electrodes that are likely to be less visible to the user's eyes, and in some cases these of conductive material It is better to include the region 111 in the transparent sensor. The two ends of each individual row electrode are connected together by a short circuit connection 130. These short-circuit connections 130 are similar to the short-circuit connections described above and will therefore be understood from those short-circuit connections.

Despite the specific pattern differences in the conductive material forming the electrodes, the sensor 110 shown in FIGS. 10A and 10B operates in the same general manner, and its operation is understood from the sensors shown in FIGS. 1A and 1B. Like. Accordingly, FIG. 10A also shows the drive unit 116 and the sensor controller 110. The drive unit 116 differs from the drive unit 6 shown in FIG. 1A in that it comprises four (rather than three) drive channels D1, D2, D3 and D4. This is because one of the multiple rows of keys of the sensor 110 (ie, the bottom row in the orientation shown in FIG. 10A) has four key regions, and in order to service this row This is because four drive channels are required. Apart from this difference, the drive unit 116 operates in the same way as the drive unit shown in FIG. 1A, and its operation will be understood from the drive unit shown in FIG. 1A. Similarly, in FIG. 10B, a perception unit 118 and also a sensor controller 110 are shown. This perception unit operates in the same manner as the perception unit 8 shown in FIG. 1B, so that its operation will be understood from the perception unit shown in FIG. 1B.

  The sensor controller 110 operates in a broad sense similar to the sensor controller 10 shown in FIGS. 1A and 1B. However, the related key structure differences mean that different logic is required to determine which key is being touched. For the sensor 110 shown in FIGS. 10A and 10B, when a signal is detected by the perceptual channel S1 or S2 (upper two rows), the selected key region is active in the drive channel D1, D3 or D4. It depends on a certain drive channel. (Because the column electrodes connected to drive channel D2 do not overlap with the row electrodes connected to sensory channels S1 and S2, drive channel D2 cannot provide a sensory signal to sensory channel S1 or S2. On the other hand, when a signal is detected by the perceptual channel S3 (bottom row), the selected key region is the drive channel that is active of the drive channels D1, D2, D3 or D4. Will depend on.

  11A and 11B schematically show a front view and a back plan view of a two-dimensional capacitive position sensor 210 according to another embodiment of the present invention. The sensor shown in FIGS. 11A and 11B is again operating in the same manner as the sensor shown in FIGS. 1A and 1B, but again based on a different key configuration. In this case, a 6 row and 8 column key array (a total of 48 key regions) is provided. Accordingly, a corresponding drive unit (not shown) has 8 drive channels coupled to 8 column electrodes, and a corresponding sensory unit (not shown) is coupled to 6 row electrodes. There are six sensory channels. As in the case of the embodiment described above, the contact position is determined from the intersection of the column electrode connected to the active drive channel and the sensory electrode connected to the sensory channel from which the signal is output.

  In addition to the increased number of rows and columns, the electrode pattern of sensor 210 shown in FIGS. 11A and 11B is similar to the electrode pattern of sensor 2 shown in FIGS. 1A and 1B in that the column electrodes are not separated by a ground shield. Is different. Also, the sensor keys shown in FIGS. 1A and 1B are based on a rhombus pattern of open and filled regions, with individual row electrodes formed from four sub-rows of conductive material. However, the key of the sensor 210 shown in FIGS. 11A and 11B is based on connected open and filled areas of rectangular shape, and each row electrode is only a single row of conductive material (multiple sub-rows). Not).

  The two ends of the individual row electrodes shown in FIG. 11B are connected together by a short circuit connection 230. These short-circuit connections 230 are again similar to the short-circuit connections described above and will therefore be understood from their short-circuit connections. Each end of each column electrode shown in FIG. 11A is also connected together by a column short-circuit connection 240. These short-circuit connections are used to reduce the electrical impedance provided to the drive channel, and methods for reducing the electrical impedance are used to reduce the electrical impedance provided to the sensory channel. Same as short circuit connection 230 between the ends of the electrodes. This is particularly useful for sensors with a relatively large area or a narrow key area, since the resistance of the column electrodes and the resistance of the row electrodes can be significantly increased. Therefore, the sensor 210 shown in FIGS. 11A and 11B is particularly suitable for a wider touch screen, such as on the order of 16 cm × 12 cm, used at a point on the sales terminal.

  While the sensor according to the present invention has been described in the form of driven column electrodes and sensory row electrodes, it will be understood that these electrodes can be reversed without changing the underlying operating principle. . For example, the sensor 2 shown in FIG. 2 can be operated in the same way by connecting the row electrodes to the drive channel and connecting the column electrodes to the sensory channel. The substrate 4 can also be reversed so that during normal use, the surface referenced above as the back is the surface facing the user of the substrate. However, it will be understood that the extent to which the electric field overflows is usually determined by the electrode patterns on both sides of the substrate and is not necessarily the same on both sides of the substrate. Therefore, during normal use, it is advantageous to place an electrode pattern with the greatest degree of electric field overflow on the surface of the substrate opposite the object to be perceived (eg, the user's finger or stylus). Experiments have also shown that excellent sensitivity is obtained when the sensory electrode is placed on the surface of the substrate opposite the object to be perceived during normal use. For example, compared to the case where an object facing the driven electrode is detected, twice the measurement signal intensity can be obtained.

  Also, instead of utilizing a transmit-receive structure (ie instead of using drive and sensor electrodes), it is also possible to use the substrate, electrode pattern and short-circuit connection structure described above in a passive configuration. That is, instead of having a drive channel that applies a drive signal to the drive electrode and a sensory channel that detects the sensory signal induced by the drive signal to the sensory electrode, individual electrodes can be connected to a single electrode capacitive sensory channel. (For example, as described in Patent Document 3). With this structure, each individual row and column of electrodes will independently sense the position of the object along two corresponding directions. For example, referring to the embodiment shown in FIGS. 5A and 5B, each of the three column electrodes of FIG. 5A and the three row electrodes of FIG. 5B can be connected to the exact same single electrode capacitive sensing channel. Thus, the signal coupled to the column electrode of FIG. 5A can be used to identify the horizontal contact position (in the case of the orientation shown in FIG. 5A), while coupled to the row electrode of FIG. 5B. The signal can be used to identify the position of the object in the vertical direction.

Finally, while the term “contact” is frequently used in the above description, a sensor of the type described above is sensitive enough that it does not require physical contact and does not require physical contact. Note also that the position of other objects) such as a stylus can be indicated. Therefore, the term “contact” as used herein should be interpreted accordingly.
(References)
[1] WO 00/44018 (Harald Philip)
[2] US 5,730,165 (Harald Philip)
[3] US 4,879,461 (Harald Philip)
[4] US 5,648,642 (Synaptics)

1 is a schematic front view of a two-dimensional capacitive position sensor according to an embodiment of the present invention. 1 is a schematic rear plan view of a two-dimensional capacitive position sensor according to an embodiment of the present invention. FIG. 1 is a schematic view collectively showing a front view and a rear plan view of the sensor shown in FIGS. 1A and 1B. FIG. FIG. 3 is a schematic plan view showing an area where the sensor shown in FIG. 2 is located on an enlarged scale. FIG. 3B is a schematic cross-sectional view of the same portion of the sensor shown in FIG. 3A. FIG. 3B is a schematic cross-sectional view in which electric field lines are superimposed on a part of the sensor shown in FIG. 3B. FIG. 3B is a schematic cross-sectional view in which electric field lines are superimposed on a part of the sensor shown in FIG. 3B. The schematic plan view which shows a part of sensor by other embodiment of this invention. The schematic plan view which shows a part of sensor by other embodiment of this invention. FIG. 6 is a schematic front view of a two-dimensional capacitive position sensor according to another embodiment of the present invention. FIG. 6 is a schematic rear plan view of a two-dimensional capacitive position sensor according to another embodiment of the present invention. 1 is a schematic diagram illustrating an electrical circuit for use with a sensor according to an embodiment of the present invention. 6B is a schematic diagram showing the timing relationship between several elements of the circuit shown in FIG. 6A. 1 is a schematic diagram illustrating a touch-sensitive display screen incorporating a sensor according to one embodiment of the present invention. 1 is a schematic diagram illustrating a washing machine incorporating a sensor according to an embodiment of the present invention. 1 is a schematic diagram illustrating a cellular telephone incorporating a sensor according to an embodiment of the present invention. FIG. 6 is a schematic front view of a two-dimensional capacitive position sensor according to another embodiment of the present invention. FIG. 6 is a schematic rear plan view of a two-dimensional capacitive position sensor according to another embodiment of the present invention. The schematic front view of the two-dimensional capacitive position sensor by further another embodiment of this invention. FIG. 6 is a schematic rear plan view of a two-dimensional capacitive position sensor according to still another embodiment of the present invention.

Claims (20)

A substrate,
A first resistive electrode on one side of the substrate;
A second resistive electrode on the other side of the substrate;
A capacitive sensor comprising a short-circuit connection adapted to connect between at least two positions on the first electrode.   The sensor of claim 1, comprising another short circuit connection adapted to connect between at least two locations on the second electrode.   One electrode of the first and second electrodes is disposed in a pattern having an array of a plurality of open regions, and the other electrode of the first and second electrodes is the open region. 3. A sensor according to claim 1 or 2, arranged in a pattern having an array of a plurality of fill areas adapted to align with the sensor.   The sensor according to claim 3, further comprising a region formed of the same material as that of the electrode disposed in the open region and electrically separated from the electrode.   The sensor according to claim 1, wherein the electrode is transparent.   The sensor according to claim 1, wherein the substrate is transparent.   The sensor according to claim 1, further comprising at least one other electrode on the same surface as the first electrode of the substrate.   The sensor of claim 7, comprising a ground electrode disposed between the first electrode and the at least one other electrode.   The sensor according to claim 1, further comprising at least one other electrode on the same surface as the second electrode of the substrate.   The sensor of claim 9, comprising a ground electrode disposed between the second electrode and the at least one other electrode.   At least one other electrode on the same side of the substrate as the first electrode, and at least one other electrode on the same side of the substrate as the second electrode, the electrode being a matrix array 11. The sensor according to any one of claims 1 to 10, which is arranged as described above.   A drive channel operable to apply an electrical drive signal to one of the first and second electrodes, and one of the first and second electrodes in response to the drive signal 12. A sensor according to any of claims 1 to 11, comprising a sensory channel operable to detect an electrical sensory signal induced on the other electrode.   13. The drive channel comprises a switch element that can be operated to selectively connect an associated electrode to a voltage source and selectively release the associated electrode from the voltage source. Sensor.   14. A sensor according to claim 12 or 13, wherein the sensory channel comprises a charge transfer circuit.   15. A sensor according to any of claims 12 to 14, wherein the sensory channel is coupled to the electrode on the surface of the substrate facing the object to be perceived during normal use.   A control panel comprising the sensor according to claim 1 and a cover panel covering the sensor.   The control panel of claim 16, wherein the cover panel and the sensor are attached to each other using a refractive index matching adhesive.   18. The control panel according to claim 16 or 17, further comprising a display screen covering under the sensor.   The control panel of claim 18, wherein the display screen and the sensor are attached to each other using a refractive index matching adhesive.   An apparatus comprising the control panel according to claim 16.

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