WO2013153609A1

WO2013153609A1 - Location detection device and method for controlling same, and system comprising same

Info

Publication number: WO2013153609A1
Application number: PCT/JP2012/059722
Authority: WO
Inventors: 大塚寛治; 秋山豊; 佐藤陽一; 目黒弘一
Original assignee: 株式会社ＪＪｔｅｃｈ
Priority date: 2012-04-09
Filing date: 2012-04-09
Publication date: 2013-10-17
Also published as: JPWO2013153609A1; JP5776917B2

Abstract

An electrostatic capacitance-type touch panel (10) comprises, for example: a substrate (12) having a conductive film (14) formed on the surface thereof; nodes (A) and (B) on the X-axis of the conductive film (14), and nodes (A) and (D) on the Y-axis thereof; a reference clock generating circuit (20) for applying a clock signal to the nodes (A-D) by way of corresponding load resistors (R0); a location information extraction unit (30) for generating a differential voltage signal between the nodes (A) and (B), and between the nodes (A) and (D), for example; and a location detection unit (40) for detecting the X-axis and Y-axis coordinates on the basis of the location information generated.

Description

POSITION DETECTION DEVICE, ITS CONTROL METHOD, AND ITS SYSTEM

The present invention relates to an electrostatic capacitance type position detection device, for example, an apparatus for extracting coordinates by contact or non-contact of an object (for example, a finger) to a panel, a control method system thereof, and a system thereof. In the present specification, devices for extracting the coordinates are collectively referred to as a “touch panel”, which includes the extraction of coordinates by non-contact means.

In recent years, touch panels have been used as input interfaces for mobile devices such as smartphones, liquid crystal display devices, electronic boards, and the like. As a touch panel technology, a capacitive type (surface-capacitive) type and a resistive film type are known. In general, the electrostatic capacity type method coats a transparent conductive film on the surface of a transparent substrate such as glass or plastic, and forms a capacitance (capacitor) by touching the transparent substrate with a finger. The position (coordinates) is detected by detecting the amount of change in the weak current passed through. The capacitive type method does not require a two-layer conductive film unlike the resistive film type, and can be composed of a single glass substrate on which a transparent conductive film is formed. It has the advantage of low score and high transmittance.

A liquid crystal module having a capacitively coupled touch panel function is configured by sandwiching liquid crystal between the first substrate and the second substrate and forming a transparent conductive film on the surface of the second substrate. (Patent Documents 1 and 2). In this touch panel, when a pulse voltage is applied to the four nodes at each corner of the transparent conductive film and the finger is touched, the voltage waveform appearing at the node at each corner varies depending on the finger contact position. A waveform is obtained, and the contact position (coordinate position) is detected based on these voltage waveforms. Also, the rise time of the pulse voltage that appears at the other corner when the pulse voltage is applied to one corner of the touch panel is measured, and then one corner when the pulse voltage is applied to the other corner There is also a technique that measures the rise time of the pulse voltage appearing at, and detects the finger contact position using the time difference between the two measurement times (Patent Document 3).

On the other hand, Patent Document 4 discloses a memory-logic conjugate system (MLCS). The MLCS is, for example, a system in which a plurality of cluster memory chips each including a cluster memory in which basic cells having memory circuits are arranged in a cluster are three-dimensionally stacked, and each of the plurality of cluster memory chips has a through via. Is provided, and the arbitrary basic cell is switched to the logic circuit by directly accessing the arbitrary basic cell through the multi-bus including the through via and writing the truth value data.

JP 2008-134522 A JP 2009-1116090 A JP 2009-015492 A JP 2010-015328 A (US Patent Publication No. 2011-0255323) In addition, each of Patent Documents 1 to 4 is incorporated in the present invention, and the contents disclosed by each of Patent Documents 1 to 4 are disclosed in the present specification. Part.

The present invention relates to a capacitance type position detection apparatus capable of accurately (highly) detecting a position where an object is in contact with a substrate or a position where an object is close to a substrate without contact, and its control. A method (position detection method) and a system including a position detection device are desired.

The position detection device according to the present invention is connected to at least two points on the conductive film, the insulating film formed on the conductive film, and at least one of the X axis and the Y axis of the conductive film. First and second nodes, a first circuit (application circuit) for applying a clock signal to the first and second nodes, and first and second nodes obtained from the first and second nodes, respectively. A second circuit (extraction circuit) that generates a first differential signal indicating a voltage difference between the second output signals, and at least one of the objects approaching or contacting the insulating film based on the first differential signal And a third circuit (detection circuit) for deriving the coordinate position of one of the axes.

The position detection method of the present invention applies a common clock signal to the first and second nodes on the X axis of the conductive film and the third and fourth nodes on the Y axis of the conductive film, Generating a first difference signal indicating a difference voltage between the first and second nodes on the axis, generating a second difference signal indicating a difference voltage between the third and fourth nodes on the Y axis, and Based on the first and second difference signals, the coordinates of the position at which the object approaches or contacts the XY plane of the insulating film formed on the conductive film is derived.

According to the present invention, the position where the object approaches or contacts the XY plane of the insulating film formed on the conductive film by generating the differential signal indicating the voltage difference between the plurality of signals respectively corresponding to the plurality of nodes. Can be detected accurately and at high speed.

FIG. 1A is a cross-sectional view illustrating the configuration of the substrate of the touch panel, and FIG. 1B is a diagram illustrating the overall configuration of the touch panel of this embodiment. It is a figure explaining the differential voltage between the nodes of the touch panel which concerns on the Example of this invention. It is a figure explaining the measurement principle of the differential voltage between the nodes A and B of a touch panel. It is a figure explaining the measurement principle of the differential voltage between nodes A and B of a touch panel, and the differential voltage between nodes A and D. It is the simulation waveform of the differential voltage seen from nodes A and B and nodes A and D. 6A shows the sensitivity characteristics of the differential voltages of the nodes A and B, and FIG. 6B shows the sensitivity characteristics of the differential voltages of the nodes A and D. It is a block diagram which shows the structure of the positional information extraction part of the touchscreen which concerns on the Example of this invention. It is a figure which shows the circuit structural example of the positional information extraction part shown in FIG. It is a block diagram which shows the structural example of the position detection part of the Example of this invention. It is a figure explaining the detection method of the rough coordinate area | region at the time of the 1-point contact by the Example of this invention. It is a figure explaining the detection method of the detailed coordinate position by the Example of this invention. It is a figure explaining the data amount required for the coordinate detection by the look-up table by the Example of this invention. It is a figure explaining the structure of the look-up table by the Example of this invention. It is a figure explaining the detection principle of two-point contact by the Example of this invention. It is a figure which shows the measurement result of two representative points between nodes A and B. It is a figure which shows the measurement result of two representative points between nodes A and D. It is a detection result when changing the distance between two points. It is a detection result when changing the distance between two points. It is a detection result when changing the distance between two points. This is a detection result when the distance between two points near the corner is moved. It is a figure explaining the detection principle of the three-point contact by the Example of this invention. It is a differential voltage waveform of 1-point contact, 2-point contact, and 3-point contact (Method A). It is a differential voltage waveform of 1 point contact, 2 point contact, 3 point contact (B method). It is a graph which shows the relationship between a differential voltage and load resistance R0. It is a graph which shows the coordinate dependence of a differential signal voltage. 6 is a graph showing the capacity dependency of a differential signal voltage viewed from nodes A and B. It is a graph which shows the relationship between capacitance coefficient (alpha) and touch capacitance. It is a figure explaining the normalized signal voltage by the Example of this invention. It is a graph which shows the coordinate dependence of the differential signal voltage of node A and B. FIG. It is a graph which shows the coordinate dependence of the normalization signal voltage of nodes A and B. It is a graph which shows the coordinate dependence of the differential signal voltage of nodes A and D. It is a graph which shows the coordinate dependence of the normalized signal voltage of node A, D. It is a graph which shows the capacity | capacitance dependence of the normalized signal voltage of node A and B. FIG. It is a graph which shows the capacity | capacitance dependence of the normalized signal voltage of node A and B. FIG. It is a figure explaining the calculation flow of the touch capacitance by the Example of this invention. 4 is a flow of a touch detection algorithm according to an embodiment of the present invention. It is a figure which shows the measurement result of the hovering touch by the Example of this invention.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. It should be noted that the scale of the drawings is emphasized for easy understanding of the features of the invention and is not necessarily the same as the scale of an actual device.

FIG. 1A is a cross-sectional view illustrating a schematic configuration of a substrate included in a capacitive touch panel according to the present embodiment. The touch panel 10 includes a transparent substrate 12 made of glass, plastic, or other material, and a transparent conductive film 14 made of ITO (Indium Tin Oxide) or other material formed on the entire surface of the substrate 12. The The conductive film 14 may be covered with a thin sheet-like transparent insulating protective film 16, such as a polyester sheet. Typically, the touch panel 10 is modularized or integrated with a display display (for example, a liquid crystal panel, an organic electroluminescence panel, or an electronic board) to constitute a display device having an input function. For example, the substrate 12 is configured to transmit image information generated by a liquid crystal panel or the like. In the present specification, the “touch panel” is not limited to the case where the object touches the panel (touching), and includes a case where the object and the panel do not contact each other through a predetermined distance. An example of non-contact includes a case where an object (for example, a finger) moves while hovering over the panel. Further, the substrate 12 may be rigid or flexible. That is, the touch panel 10 may be rigid or flexible corresponding to the composition characteristics of the display. Furthermore, when the touch panel 10 is integrated with a display, the substrate 12 as the touch panel 10 may be omitted.

FIG. 1B is a diagram showing an overall schematic configuration of the touch panel 10. Nodes A, B, C, and D are formed at the X-axis and Y-axis corners on the conductive film 14, and the nodes A to D are connected to the common node N of the reference potential generation circuit 20 through the resistor R0. Connected. The reference potential generation circuit 20 preferably generates a reference pulse signal having a constant frequency, for example, 1 MHz, and may further add a constant DC bias to the reference pulse signal. Thus, the reference clock signals having the same phase and the same potential are simultaneously supplied to the nodes A, B, C, and D through the resistor R0.

In a capacitive touch panel, when a finger comes into contact with the conductive film 14 or approaches the conductive film 14 through the protective film 16 (hereinafter referred to as contact including such approach), the contact position P The electrostatic capacitance Cs is formed (see FIG. 1B), and a weak current flows from the nodes A to D to the contact position P. Since the resistors Ra and Rb are formed according to the distance from the node A to the contact position P and the distance from the node B to the contact position P, each of the nodes A to D is determined by the time constant of the resistance and the capacitance. A current having a voltage waveform flows.

Signals flowing through the nodes A, B, C, and D are provided to the position information extraction unit 30. The position information extraction unit 30 extracts a differential voltage between the nodes A and B on the X axis, as will be described later. In addition, a process for extracting a differential voltage between the nodes A and D on the Y axis is performed. The information extracted by the position information extraction unit 30 is provided to the position detection unit 40, and position detection for specifying the contact position P is performed based on the extracted position information. The position information detection unit 30 and the position detection unit 40 may be configured in any form, and may be configured using hardware, software, or both hardware and software. In a preferred embodiment, the position information detection unit 30 is configured by a circuit or the like that processes an analog signal, and the position detection unit 40 is configured by a circuit or software that processes a digital signal. The output of the position detection unit 40 is provided to a display device or a system that controls the display device.

Next, the principle of detecting the position of the touch panel according to this embodiment will be described. In this embodiment, as shown in FIG. 1B, in the capacitive touch panel, two nodes A and B on the X axis and two nodes A and D on the Y axis are differential signals. The contact position is detected using.

As shown in FIG. 2A, when the position P on the touch panel is touched, the nodes A and B on the X axis are connected to the resistors Ra and Rb and the capacitance Cxy as shown in FIG. The voltage signals Va and Vb determined by the time constant are generated. V _A −V _B is the difference between the voltage signals Va and Vb, and the peak value of the difference between the voltage signals Va and Vb is illustrated in the example in the figure. Although not shown here, the voltage signals Va and Vd determined by the time constants of the resistors Ra and Rd are generated in the nodes A and D on the Y axis, and the differential voltages of the voltages Va and Vd are extracted. .

FIG. 3 is a diagram for explaining the principle of differential voltage measurement. If the contact position P is close to the node A and away from the node B with respect to the nodes A, B, C, and D, the resistance between the contact position P and the node A is small. The influence of the contact position P appears strongly (the voltage drop is large), and conversely, the influence of the contact position P appears weakly at the node B because the resistance between the contact position P and the node B is large (the voltage drop is small). ). Therefore, when the voltage change from the node A to the node B is seen, a positive voltage change can be observed. That is, the voltage between the nodes A and B is a difference between the distance a and the distance b from the nodes A and B to the contact position P as a voltage difference. Further, since the voltage difference between the two points is observed, the GND fluctuation and the common mode noise are removed, and the difference voltage becomes 0 V at the point where the distance to the contact position P is equal, that is, on the center line.

Next, a differential voltage measurement model between two nodes when a clock signal is simultaneously applied to the four nodes A, B, C, and D of the touch panel via the resistor R0 will be examined. As shown in FIG. 4, P is a contact position, and a, b, c, and d are distances from the contact position P to each node. At this time, the voltages appearing at the terminals are V (A), V (B), V (C), and V (D).

The differential voltage measurable here is defined as follows.
V _BA = V (B) -V (A), V _AB = V (A) -V (B),
V _CA = V (C) −V (A), V _AC = V (A) −V (C),
V _DA = V (D) −V (A), V _AD = V (A) −V (D),
V _CB = V (C) −V (B), V _BC = V (B) −V (C),
V _DB = V (D) −V (B), V _BD = V (B) −V (D),
V _DC = V (D) −V (C), V _CD = V (C) −V (D)

In addition, the following relationship is established between them.
V _BA = −V _AB , V _CA = −V _AC , V _DA = −V _AD ,
V _CB = −V _BC , V _DB = −V _BD , V _DC = −V _CD
Also,
Since V _CB = V _CA −V _BA , V _DB = V _DA −V _BA , and V _DC = V _DA −V _CA , it cannot be obtained from other differential voltages among measurable differential voltages. The differential voltage can be aggregated into two, V _BA and V _DA . That is, if these two differential voltages are known, the other differential voltages can be obtained by an arithmetic operation.

FIG. 5 shows a simulation waveform of the differential voltage viewed from the nodes AB and AD. When the X and Y coordinates of the touch panel are (0, 0) to (32, 32), the distance from node D to (2, 30) is equal to the distance from node B to (30, 2). However, the voltage difference occurs because the distances to the node A are different. The greater the distance to the node A, the smaller the influence of the node A and the larger the signal amount.

The position detection algorithm using differential measurement according to the present embodiment is organized as follows.
Reference pulse signals are simultaneously input to the four nodes A to D, and among them, the differential output between the two nodes of the X axis and the Y axis is measured.
In order to measure the differential voltage, the maximum value is obtained by the magnitude relation between the resistance drawn between the two nodes and the resistance drawn.
The strobe time of the maximum value of the difference voltage is different, and the maximum value has good detection sensitivity, and this is extracted.
However, in order to avoid the influence of noise superimposed on the maximum value, the two-point measured values of the nodes A and B on the X axis and the nodes C and D, and the two-point measured values of the nodes A and D on the Y axis and the nodes B and C are used. It is desirable to cancel noise.
The sampling interval is set at a level of 0.01 s, and noise cancellation is performed from two-point measurement and two-time measurement on the time axis. In this sampling operation, two-point measurement of nodes A and B on the X axis and nodes C and D on the X axis and two points measurement on the nodes A and D on the Y axis and nodes B and C in accordance with, for example, a 1 MHz reference clock signal. Is repeated as many times as necessary to achieve noise cancellation.

Next, when the differential voltages V _BA and V _DA are measured, positive and negative boundary lines (0 V line) of signal amounts peculiar to the respective measurement modes as shown in FIGS. _6A and 6B appear. That is, when the differential voltage _VBA between the nodes A and B on the X axis is measured, the line passing through the center O in the direction perpendicular to the X axis is 0 V, and the region close to the node A on the left side with this 0 V as a boundary Then, the sign of the differential voltage V _BA is positive (+), and in the region close to the right node B, the sign of the differential voltage V _BA is negative (−). Similar characteristics occur when the differential voltage _VDA between nodes A and D on the Y axis is measured.

Next, a preferred configuration of the touch panel of this embodiment will be described. FIG. 7 is a block diagram showing a preferred configuration of the position information extraction unit. The position information extraction unit 30 receives the output signals of the four nodes A to D, and selects the output signal of the two nodes selected by the selector 100 and the selector 100 that selects two output signals from among the output signals. Dynamic amplifier 102, filter 104 for removing noise of the differential signal output from differential amplifier 102, peak value hold circuit 106 for extracting the peak value of the differential signal from which noise has been removed, and peak hold circuit 106 An A / D converter 108 that performs analog / digital conversion of the output signal, a third circuit (detection circuit) 110 that detects that a finger has been touched in response to a current flowing through each node, A flip-flop circuit 112 that switches the selection by the selector 100 when contact is detected by the circuit 3 (detection circuit) 110, and a reference voltage It receives the reference clock signal from the generating circuit 20, configured to include a supply controller 114 to each part of the various clock signals via the signal bus BUS.

The third circuit (detection circuit) 110 detects the presence or absence of a finger touch at a timing synchronized with the rising edge of the clock signal supplied from the controller 114. When the contact of the finger is detected, the third circuit (detection circuit) 110 supplies an enable signal to the flip-flop circuit 112 to make the flip-flop circuit 112 operable. The controller 114 supplies a clock signal having a constant frequency to the flip-flop circuit 112 via the signal bus BUS, and the flip-flop circuit 112 is a signal that holds the detection state of the third circuit (detection circuit) in response to the clock signal. Is output to the selector 100. The controller 114 also outputs a switching clock signal corresponding to the selected state to the selector 100 in response to the clock signal. The selector 100 selects an output signal of a pair of nodes according to the selection state. For example, in the first selection state, the output signals of the nodes A and B on the X axis are selected, in the next state, the output signals of the nodes A and D on the Y axis are selected, and so on. These output combinations are repeated by selecting the correct output signal. The selection cycle is appropriately selected according to the frequency of the clock signal from the controller 114. Preferably, the finger contact time is typically about 0.1 seconds, so that the selector 100 is at least 100 times in the meantime. It is possible to sample about a certain number of nodes.

The differential amplifier 102 extracts a difference voltage signal between the output signals of the two nodes (A and B or A and D) selected by the selector 100. The filter 104 is preferably configured using a low-pass filter, and removes high frequency component noise superimposed on the differential voltage signal. In response to the clock signal from the controller 114, the peak value hold circuit 106 holds the peak value of the differential voltage signal during the period from the rising edge to the falling edge of the clock. The A / D converter 108 receives the peak value of the difference voltage held by the peak value hold circuit 106, converts it into a digital value having a predetermined number of bits, and provides it to the position detection unit 40. The position detection unit 40 detects the contact position by processing the received digital signal as described later.

FIG. 8 shows a specific circuit configuration of the position information extraction unit 30 shown in FIG. The position information extraction unit 30 includes a differential amplifier 120, a noise filter 130, an absolute value amplifier 140, and a peak value hold circuit 150. Here, the A / D converter is not shown.

The differential amplifier circuit 120 receives the output signals from the two nodes selected by the selector 100, indicates the differential voltage, and outputs the differential signal. The differential amplifier circuit 120 is configured using, for example, AD620 manufactured by Analog Devices. The noise filter 130 receives the differential signal from the differential amplifier 120 and removes high-frequency component noise superimposed thereon. The noise filter 130 is configured using, for example, a low-pass filter of LTC1063 manufactured by Linear Technology.

As is known, the absolute value amplifier 140 includes two

operational amplifiers

140A and 140B that function as a normal amplifier or an inverting amplifier according to the polarity of the input signal. When the input voltage of the output signal VOUT from the noise filter 140 is positive, the two operational amplifiers function as normal amplifiers that amplify the input signal, and when the input voltage is negative, the two operational amplifiers are input. Functions as an inverting amplifier that inverts the signal. As described with reference to FIGS. 6A and 6B, the differential signal (differential voltage) has a positive or negative sensitivity characteristic depending on the contact position P, but the differential signal passes through the absolute value amplifier 140. By doing so, all signals are converted to a positive voltage signal.

The peak value hold circuit 150 is charged to the comparator 150A for inputting the output signal from the absolute value amplifier 140 and the negative feedback reference voltage of the operational amplifier 150B, the diode D connected to the output of the comparator 150A, the capacitor C, and the capacitor. And a reset circuit that discharges the charged charges. The comparator 150A supplies a power supply potential when the output signal from the absolute value amplifier 140 is higher than the reference voltage, so that the capacitor is charged via the diode D1. On the other hand, when the output signal becomes smaller than the reference potential, the comparator 150A supplies a negative power supply potential, so that the current is cut off by the diode D, and thus the peak voltage is held by the capacitor C. The reset circuit includes a transistor Tr and an FET, and a reset pulse signal is applied to the base of the transistor Tr. For example, the pulse width of the reset pulse signal is smaller than 10 μS. When the reset pulse signal becomes low active, the transistor Tr is turned on, and the FET is turned on, so that the capacitor C is discharged. Thus, the peak value held by the peak value hold circuit 150 is provided to the A / D converter. Note that the circuit shown in FIG. 8 is an example, and other configurations may be used.

Next, the position detection unit of this embodiment will be described. The position detection unit 40 shown in FIG. 1 (B) determines one-point contact (single touch) or multiple points contact (multi-touch) based on the data extracted by the position information extraction unit 30, and displays the determination result. Coordinate information corresponding to the detected contact position is output.

FIG. 9 shows a preferred configuration example of the position detection unit 40. The position detection unit 40 receives the position information extracted by the position information extraction unit 30 or outputs the coordinate information of the detected contact position, and an input / output unit (I / O) 200 for performing position detection. A program memory 210 storing various programs, a data memory 220 storing various data such as a look-up table for position detection, and a central processing unit 230 performing various arithmetic processes by executing the programs It is comprised including.

A position detection method for one-point contact (single touch) will be described.
In one-point contact, a method for specifying the coarsest coordinate region is sign determination. As described in the sensitivity characteristics of FIG. 6, when the differential voltage between nodes AB, CD, AD, and CB is measured, the differential voltage varies depending on the contact position. The sign polarity is different. However, between AB here is a differential voltage based on node A. If this property is used, it can be determined from the two measurement data between AB and AD that the contact position is in one quadrant, two quadrants, three quadrants or four quadrants as shown in FIG. Can be determined. Each quadrant is an area with the center line of the X axis and Y axis of the touch panel as a boundary. As shown in the figure, the signs of the differential voltages V _BA and V _DA are both positive in the first quadrant, the differential voltage V _BA is negative and the V _DA is positive in the second quadrant, and the differential voltages V _BA and V _{DA are} positive in the third quadrant. The signs of voltages V _BA and V _DA are both negative, and in four quadrants, differential voltage V _BA is positive and V _DA is negative. In the case where the detection accuracy may be rough, the position detection unit 40 is based on the fact that the contact position belongs to one of the quadrants 1 to 4 based on the differential signals obtained from the two differential voltages V _BA and V _DA. To detect.

Next, a method in which the position detection unit 40 detects a contact position with higher accuracy by referring to a lookup table will be described. As shown in FIG. 10, when there is a contact point in one quadrant, the sign of the signal amount is all positive and the signal amount also shows the maximum value. Due to the symmetry of the substrate, if the reference is shifted to a region where the contact position is, the signal amount always becomes a positive value and the signal amount is also maximized. Further, by utilizing this property, the profile to be prepared (capacity of the lookup table LUT) may be prepared in 1/4 of the area of the entire touch panel, that is, in one quadrant.

When assuming touch with a finger, the resolution of the coordinate specification area is limited by the touch area of the finger, and the number of coordinate points must be determined according to the size of the panel. Therefore, here, a touch panel having a 65 × 65 seat that can be handled even when a considerably large panel is considered is assumed. In this case, since the size of the coordinate profile necessary for specifying the coordinate area is only a quarter area as described above, the coordinate area is 33 × 33 as shown in FIG.

The coordinate area is treated as an 8-coordinate interval, and (1) the coordinate value of the coordinates (00, 16) and the extracted position data (extracted by the position information extraction unit) are the same as in the code determination method. The relationship is compared, and then (2) the size relationship between the coordinate value of the coordinate (16,000) and the extracted position data is compared. The look-up table stores coordinate values at predetermined coordinates, and the coordinate values are values corresponding to the signal amount of the differential voltage at the coordinates. If both of the above determinations (1) and (2) have large extraction position data, the area indicated by the circle shown in FIG. 11 is obtained.

In order to further improve the accuracy of detection of the contact position, after specifying the coarse coordinate area shown in FIG. 11, using a double precision lookup table corresponding to that area, further specify the coordinate area in detail, When this area has been identified, a coordinate area is further identified using a double-precision lookup table. By repeating such determination, the final coordinates can be obtained. The example of FIG. 11 shows an example in which the coordinate values (21, 29) are finally calculated.

Next, the necessary data prepared in the lookup table for coordinate determination will be described. As shown in FIG. 12A, consider an 8 × 8 region that can be represented by 9 × 9 lattice points. The grid required for comparison is represented by black circles and white circles. Black circles are data used for comparison in the Y direction, and white circles are data used for comparison in the X direction. When all of these are combined into one, it is as shown in FIG. 12B, and can be expressed by 8 × 8 by the number of these data.

Next, the configuration of the lookup table will be described. The data required for the area comparison represented by the 33 × 33 grid points that are 1/4 of 65 × 65 only needs to be able to represent 32 × 32 grid points, and requires a 2 ⁵ × ²⁵ , 10-bit address space. It becomes. As shown in FIG. 13A, the address bits are configured such that the X address has 5 bits and the Y address has 5 bits. The distinction between the four areas of the first quadrant to the fourth quadrant is managed using a register.

The address setting when specifying a coarse coordinate area of 8 × 8 is as shown in FIG. Here, xxx is an arbitrary numerical value. The detailed coordinate area is set to x from the left of the 0 part of the XY address.

Since the bit structure of the lookup table uses a differential method, the signal change value is in the range of −2V to 2V. If the resolution is set to 1 mV and the accuracy is set to about 2 mV, 4K resolution is required, and the number of bits of the A / D converter is 12 bits.

Next, a method for detecting the position of multi-point contact (multi-touch) will be described.
The position detection of the multipoint contact can be obtained from the superposition of the single point contacts.
As shown in FIG. 14, the case where the contact point T2 overlaps the contact store T1 is considered. However, the signal amount is a value viewed from the node AB. In this case, since the electrostatic capacitance due to the contact is almost doubled, the signal amount is increased. However, the magnitude of the signal amount is not doubled and is about 1.3 to 1.8 at the time of one-point contact. When the contact point T2 moves away from the contact point T1, the resistance change of b2 is small in the example in the figure, but the resistance of a2 changes greatly. Since the distance a1 of the contact point T1 is in the vicinity of the node A and b1 is away from the node B, the signal voltage is almost determined by a1. When the contact point T2 moves away from the contact point T1, the distance a2 increases, the signal amount due to a2 decreases, and the signal amount decreases as the contact point T2 moves. As a2 gets closer to node A, the amount of signal increases. This change in the signal amount becomes a value corresponding to the moving distance between the two points. This is the detection principle of two-point contact. The two-point contact has a relatively high sensitivity because the amount of signal increases as the capacitance increases due to the contact. On the other hand, even if the sensitivity of the X-axis node AB decreases, it can be detected because the Y-axis node AD complements it.

Next, the representative two-point measurement results of multi-point contact are shown in FIGS. FIG. 15 shows differential voltage waveforms when three positions in the X-axis direction, that is, a touch between 66-12, a touch between 68-14, and a touch between 70-16 are touched. FIG. 16 shows differential signal waveforms at three positions in the Y-axis direction, that is, when touching between 65-71, touching between 38-44, and touching between 11-17. The distance between the two touch points is the same distance in all measurements, and the number on the coordinate axis indicates a value in the vicinity thereof. Even in the case of two-point touch, the signal level is higher than that in the case of one-point touch, but a signal waveform having the same sensitivity characteristic as that of the one-point touch appears. For example, in the case of touch between 66-12, the peak position of this signal waveform is the ratio of the signal amount that increases when the touch capacitance is almost doubled to the average value of the peak position of the one-point touch that touches the

points

66 and 12. It is equal to the product of the two and is represented by the center coordinates of 66 and 12 in the coordinate position. In this way, the two-point touch positioned in the horizontal direction between AB and AD is viewed as a one-point touch positioned almost at the center of the two points in terms of coordinates.

Next, detection of moving coordinates between two points will be described. 17, 18, and 19 show detection results when the distance between two points is changed in

coordinates

1, 2, and 3. FIG. These are phenomena that appear when moving in the direction perpendicular to AB, and the same result can be obtained when moving vertically to AD.
At coordinate 1, the interval is widened to be (28-46), (19-55), (10-64).
At coordinate 2, the interval is widened to be (29-47), (20-56), (11-65).
At coordinate 3, the interval is widened to be (30-48), (21-57), and (12-66).
As can be seen from these graphs, the level of the differential signal increases as the moving distance between the two points increases. This is a property that appears only in the direction perpendicular to the AB plane and represents the average rate of change of the differential signal level with respect to the moving distance. This shows the gradient of the increase in the differential signal level with respect to the coordinate change in the direction perpendicular to the AB plane. When the slope of the increase in the differential signal level is convex downward with respect to the coordinate change, a positive value is indicated, and when the slope is upward, a negative value is indicated. In the example, since it is convex downward, it becomes a positive value and indicates a spread, but at an upward convex location, it becomes a negative value and indicates reduction. This indicates that if the unevenness of the change in the differential signal level depending on the location is grasped, the enlargement / reduction can be detected by the change in the measured differential signal level.

FIG. 20 shows the detection result when the coordinates between two points near the corner are moved. Here, the distance on the Y axis is changed while the X axis is the same coordinate between the two points near the corner of the node A (the distance between the two points is 27, 81, 135). Only in this case, as described above, it can be seen that the level of the differential signal increases as the moving distance increases.

The position detection unit 40 compares the voltage level of the differential signal with the first threshold value, and determines that it is a two-point contact when it is greater than the first threshold value. The first threshold value is set in advance to a value larger than the voltage level that would be obtained at the time of one-point contact. Further, the position detection unit 40 prepares a look-up table as in the case of one-point contact, and by referring to this, it is possible to obtain the two contact positions and the unevenness of the differential signal level. Furthermore, the position detection unit 40 can detect that the two-point contact is moving due to a change in the level of the differential signal. The change in the level of the differential signal can be determined from the amount of change in the sampled peak value.

Next, the position detection method at the time of three-point contact will be described. Even in the case of three-point contact, the principle is basically the same as in the case of two-point contact, and it is detected that the capacitance increases and the level of the differential signal increases when the three-point contact is made. . When three points are touched, as shown in FIG. 21, the position information extracted from the position information extraction unit 30 represents a one-point contact that becomes the center of gravity of the triangle formed by the three contact points. 3 point contact is a combination of 1A and 2A contact, then 3A 1 point contact (Method A), or 1B and 2B contact, then 3B 1 point contact. It can be seen as the combination to be performed (Method B).

FIG. 22 shows a measurement result when the three-point contact shown in FIG. 21 is operated by the A method. It can be seen that the three-point touch has a higher voltage level than the one-point touch and the two-point touch. FIG. 23 shows a measurement result when the three-point contact is operated by the B method. Also in this case, it is understood that the voltage level is higher in the three-point touch than in the one-point touch and the two-point touch.

The position detection unit 40 compares the voltage level of the differential signal with the second threshold value, and determines that it is a two-point contact when it is greater than the second threshold value. The second threshold value is preset to a value that is greater than the voltage level that would be obtained during a two-point contact. Further, the position detection unit 40 prepares a lookup table as in the case of one-point contact, and can obtain the position of three-point contact by referring to this.

Next, optimization of the additional resistor R0 shown in FIG. The resistance R on the diagonal line of the conductive film 14 of the touch panel is constant, for example, 6 to 7 kΩ. As shown in FIG. 24, the voltage waveform of the differential voltage V _AB when the load resistance R0 is 1 kΩ, 3 kΩ, 5 kΩ, and 10 kΩ is shown. From these graphs, when the resistance is 5 kΩ, which is the same as the substrate resistance, impedance matching is performed and the maximum amplitude is obtained. For this reason, in order to improve the measurement sensitivity, it is desirable to use an additional resistance comparable to the substrate resistance.

Next, the touch panel calibration method will be described. FIG. 25 shows the coordinate value dependency (distance dependency in the Y-axis direction) of the differential signal voltage as viewed from the nodes A and B of the touch panel using the X coordinate as a parameter. As is apparent from the figure, the distance dependency of the differential signal voltage has the following characteristics.

(1) If the capacitance coefficient α for the touch capacitance is obtained such that a value obtained by multiplying the distance dependency of the touch capacitance of 20 pF by α is equal to the dependency of 40 pF, the dependency on the arbitrary capacitance can be obtained.
(2) The voltage change from the nodes A and B to the center is large, and the voltage change beyond the center is small.
This feature is also true for the nodes AD, BC, and CD. Therefore, the normalized signal voltage that does not depend on the touch capacitance can be obtained by actively utilizing this property.

FIG. 26 shows the capacity dependency of the differential signal voltage at the representative point as seen from the node AB plane. With respect to the capacitance dependency of the differential signal voltage, the touch capacitance is 40 pF (there is no problem whether the capacitance when calculating α is set to 20 pF or 60 pF, but it is set to 40 pF that seems to have the highest appearance frequency. When the capacity coefficient α at the time of the standard capacity is obtained, it is as shown in FIG.

As for the coordinate value dependency of the differential signal voltage viewed from each side of the touch panel, the coordinate dependency on an arbitrary touch capacitance value can be calculated by obtaining the touch capacitance coefficient α. However, it is not easy to obtain this α. Therefore, a normalized signal voltage that does not depend on the touch capacitance value is introduced.

When determining the touch position, the signal voltage for each side of the touch panel is measured. At this time, for example, when viewing the node AB side and the CD side, as shown by circles T1 and T2 in FIG. 28A, measurement values at two points symmetrical with respect to the center of the panel are always obtained. When the T1 signal voltage viewed from the AB side is V1, the point symmetrical to the center line of the touch panel is T2, and the T2 signal voltage viewed from the AB side is V2, the following relationship holds from the symmetry of the panel.
T1 signal voltage viewed from the DC side = V2,
T2 signal voltage viewed from the DC side = V1
When the value obtained by dividing the measured value of the two points by the smaller value and the larger value is defined as the normalized signal voltage, the capacitance coefficient α disappears and depends on the touch capacitance as shown in the equation of FIG. It is a value that does not.

The coordinate dependency of the normalized signal voltage obtained from the dependency of the differential signal voltage on the coordinate side as seen from the AB side and AD side of the touch panel is:
(1) The linearity is improved, and a sufficient signal amount change can be secured even near the center.
(2) There is no area that cannot be used to calculate coordinates with a small signal amount from the center of the panel.
FIG. 29 shows the coordinate dependency of the differential signal voltage at the node AB, which is converted into the coordinate dependency of the normalized signal voltage as shown in FIG. FIG. 31 shows the coordinate dependency of the difference signal voltage of the node AD, and FIG. 32 shows the coordinate dependency of the converted normalized signal voltage.

The capacity dependency of the normalized signal voltage viewed from the AB side is extremely small as shown in FIGS. For this reason, although it is convenient for calculation of touch coordinates, it is not possible to calculate touch capacitance, and it is necessary to use another method for calculation of touch capacitance. In order to calculate the touch capacitance, it is necessary to pay attention to a voltage change due to the capacitance. Therefore, the procedure shown in FIG. 35 is effective for calculating the touch capacitance.
(1) The differential signal voltage at the touch point is measured for the four sides of the node AB, the node CD, the node BC, and the node AD (S101).
(2) A normalized signal voltage is calculated from the measured differential signal voltage (S102).
(3) The coordinates of the touch point are calculated using the normalized signal voltage of the touch point and a lookup table of the normalized signal voltage (S103, S104).
(4) Next, the differential signal voltage V0 at the touch point is obtained from the lookup table of the differential signal voltage when the touch capacitance is the standard capacitance (S105, S106).
(5) The capacity coefficient α is calculated using the differential signal voltage V0. The capacity coefficient α is a value obtained by dividing the measured voltage Vm by V0.
(6) The touch capacitance is calculated from the obtained capacitance coefficient α using a lookup table that associates α with a capacitance value (S107, S108).

Next, FIG. 36 shows a flow of the touch detection algorithm of the touch panel of this embodiment. This algorithm is preferably controlled by a program sequence stored in program memory 210 (see FIG. 9). First, all parameters included in the position information extraction unit 30 and the position detection unit 40 are in an initial set state (S201). Next, when the power to the touch panel is turned on, the position information extraction unit 30 and the position detection unit 40 acquire correction data and set parameters based on this (S202). The correction data here is data necessary for calibration and the like, and is stored in advance in a nonvolatile memory or the like.

Next, when a touch state occurs (S203), position information is extracted by the position information extraction unit 30, and this information is A / D converted and then output to the position detection unit 40 as a digital signal (S204). . Upon receiving the data, the position detection unit 40 performs preprocessing necessary for position detection (S205). The preprocessing includes, for example, averaging processing, calculation of the normalized signal voltage, calculation of touch capacitance, and the like in order to reduce measurement errors.

Next, the position detection unit 40 determines whether or not the touch capacitance is twice or more, in other words, whether or not the peak value of the differential voltage is larger than the first threshold value (S206). If it is less than the first threshold value, it is determined that the contact is a single point, and a calculation process for calculating coordinates is performed (S207). In this calculation, as described above, sign determination based on the sensitivity characteristic of the differential voltage is performed, and in addition, detailed coordinate calculation is performed with reference to a lookup table. On the other hand, if the value is equal to or greater than the first threshold value, the position detection unit 40 determines that the contact is a multipoint contact, and further compares it with the second threshold value, thereby making a two-point contact or three-point contact You may make it determine. The position detection unit 40 refers to a lookup table corresponding to 2-point contact or 3-point contact, and calculates a coordinate position (S208).

Next, the position detection unit 40 outputs the calculated coordinate information and sets the movement flag to “1” (S209). Next, the movement detection unit 40 determines whether or not the contact point has moved (S2210). Whether or not the contact point is moved is compared with the previous coordinate output. In the case of two-point contact, since the level of the differential signal changes when the distance changes, determination may be made based on this change amount. If there is no movement, the movement flag is set to “0” (S211), and the state before the touch state occurs is returned. If it is determined that there is a movement, the processing from step S204 is continued again.

Next, the measurement result of the hovering touch is shown in FIG. The touch panel of this patent has high detection sensitivity and can detect a contact point even when a finger is removed from the panel. Operationally, it is on the extension line of one-point touch and is recognized as a one-point touch with a small capacitance coefficient α. Therefore, except for the point where the measurement limit is determined by the sensitivity of the third circuit (detection circuit), the one-point touch method can be applied as it is for the detection of coordinates and the like. In the measurement of the figure, it was confirmed that detection was possible even when separated from the panel by about 5 cm, but the distance from the panel can be increased by increasing the sensitivity of the third circuit (detection circuit).

The preferred embodiment of the present invention has been described in detail above, but the present invention is not limited to the specific embodiment, and various modifications can be made within the scope of the present invention described in the claims. Deformation / change is possible. For example, if the position detection unit 40 (FIG. 9) is realized by a memory-logic conjugate system (MLCS), a cluster memory capable of dynamic reconfiguration is configured as a lookup table (data memory 220). In addition, the arithmetic processing realized by the central processing unit 230 in a plurality of steps can be shortened. This realizes speeding up of the central processing unit 230 and size reduction of the central processing unit 230 and the data memory 220, and is more cost-effective than an FPGA (Field-Programmable Gate Array) or a microcontroller (micro controller). improves.

10: Touch panel 12: Substrate 14: Conductive film 16: Protective film 20: Reference potential generation circuit 30: Position information extraction unit 40: Position detection unit 100: Selector 102: Differential amplification circuit 104: Filter 106: Peak value hold circuit 108 : A / D converter 110: Touch third circuit (detection circuit)
112: flip-flop circuit 114: controllers P, T1, T2: contact positions A, B, C, D: nodes

Claims

A conductive film;
An insulating film formed on the conductive film;
First and second nodes connected to at least two points on at least one of the X-axis and Y-axis of the conductive film;
A first circuit (application circuit) for applying a clock signal to the first and second nodes;
A second circuit (extraction circuit) that generates a first difference signal indicating a voltage difference between the first and second output signals obtained from the first and second nodes, respectively;
A third circuit (detection circuit) for deriving a coordinate position of the at least one axis where an object approaches or contacts the insulating film based on the first differential signal;
A position detecting device.
The position detecting device is further connected to at least two points on at least one other axis of the X axis or the Y axis different from the first and second nodes, and the third and second to which the clock signal is applied. Contains 4 nodes,
The second circuit (extraction circuit) generates a second difference signal indicating a voltage difference between the third and fourth output signals obtained from the third and fourth nodes, respectively.
The position detection device according to claim 1, wherein the third circuit (detection circuit) derives a coordinate position on an XY plane where an object approaches or contacts the insulating film based on the first and second difference signals. .
The third circuit (detection circuit) compares the first difference signal with a first threshold value, and approaches or touches when the first difference signal is equal to or less than the first threshold value. 2. The determination unit according to claim 1, further comprising: a determination unit that determines that the number of approaching or touching positions is at least two when the first difference signal is greater than a first threshold value. Position detection device.
When the determination unit determines that there are at least two approaches or contact positions, the two contact positions are widened or narrowed corresponding to an increase or decrease in the first difference signal within a certain period. The position detection device according to claim 3, wherein the position detection device determines that the
The determination unit determines that the approach or contact position is at least three when the first differential signal is equal to or greater than a second threshold value that is greater than a first threshold value. The position detection apparatus described in 1.
The third circuit (detection circuit) has the approach or contact position based on a combination of a first code represented by the first difference signal and a second code represented by the second difference signal. The position detection device according to claim 2, wherein the coordinates are derived.
The third circuit (detection circuit) further defines a relationship between the coordinates of the region specified by the first and second codes and the signal value corresponding to the first and second difference signals. The third circuit (detection circuit) includes a table, and refers to the table, and compares the generated first and second difference signals with the signal value to determine the coordinates of the approach or contact position. The position detection device according to claim 6 which guides.
The position detection device according to claim 2, wherein the second circuit (extraction circuit) includes a selection circuit that selects the first and second output signals or the third and fourth output signals.
The second circuit (extraction circuit) receives the first and second output signals and outputs the first differential signal, and a first output from the differential amplifier circuit A peak hold circuit that holds a peak value of the difference signal of the signal, and an analog / digital conversion circuit that converts the peak value held by the peak hold circuit into a digital signal and supplies the digital signal to the third circuit (detection circuit). The position detection device according to claim 1, further comprising:
The position detection device according to claim 9, wherein the second circuit (extraction circuit) includes a filter that removes noise of a signal output from the differential amplification circuit.
The third circuit (detection circuit) includes a processing unit that averages digital signals corresponding to a plurality of the first difference signals within a certain period provided from the second circuit (extraction circuit). The position detection device according to claim 1.
The position detection apparatus according to claim 2, further comprising a normalization unit that normalizes the first and second difference signals.
The normalizing unit has a ratio between a third difference signal and a first difference signal at a position where the approach or contact position is symmetric with respect to a center line in the X-axis direction of the plane of the X-axis and the Y-axis. A first difference signal normalized based on the second difference signal normalized based on a ratio of the fourth difference signal and the second difference signal at a target position with respect to the center line in the Y-axis direction The position detection device according to claim 12, wherein:
A display device comprising the position detection device according to claim 1.
Applying a common clock signal to the first and second nodes on the X axis of the conductive film and the third and fourth nodes on the Y axis of the conductive film;
Generating a first differential signal indicative of a voltage difference between the first and second nodes on the X axis;
Generating a second differential signal indicative of the differential voltage of the third and fourth nodes on the Y axis;
A position detection method for deriving coordinates of a position where an object approaches or contacts an XY plane of an insulating film formed on the conductive film based on the first and second differential signals.
The position detection method
Comparing at least one of the first and second difference signals with a first threshold;
The approach or contact position is determined to be one when it is less than or equal to the first threshold value, and the approach or contact position is determined to be at least two when greater than the first threshold value. Item 16. The position detection method according to Item 15.
When it is determined that there are two approach or contact positions, the two approach or contact positions are widened or narrowed corresponding to an increase or decrease in the first differential signal within a certain period. The position detection method according to claim 15, wherein the position detection method is determined.
The position detection according to claim 15, wherein when the first difference signal is equal to or greater than a second threshold value that is greater than the first threshold value, the approach or contact position is determined to be at least three. Method.
The position detection method according to claim 15, wherein the position is detected based on a combination of a code represented by the first difference signal and a code represented by the second difference signal.
The coordinate table defining the relationship between the coordinates in the region specified by the first and second codes and the signal values corresponding to the first and second difference signals is referred to. Position detection method.