JP2013250642A - Position detection device and its control method and its system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a capacitance type position detection device capable of accurately (highly precisely) and quickly detecting a position where an object has come in contact with a substrate or a position where the object has approached the substrate in a non-contact state and its control method (position detection method) and a position detection device.SOLUTION: A capacitance type touch panel 10 includes: a substrate 12 having a conductive film 14 formed on the surface; nodes A and B on an X axis and nodes A and D on a Y axis of the conductive film 14; a reference clock generation circuit 20 for applying a clock signal via corresponding load resistances R0 to the nodes A to D; a position information extraction part 30 for generating, for example, a logarithmic signal ratio between the nodes A and B and a logarithmic signal ratio between the nodes A and D; and a position detection part 40 for detecting X axial and Y axial coordinates on the basis of position information generated by the position information extraction part 30.

Description

  The present invention relates to a capacitance type position detection apparatus, and relates to an apparatus for extracting coordinates thereof by contact or non-contact of an object (for example, a finger) to a panel, a control method system thereof, and the 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). Further, there is a display device that applies an AC signal to connection points at the four corners of the resistive film and calculates coordinates based on a difference between currents flowing at two of the four corners. (Patent Document 4).

Patent Document 1: Japanese Patent Application Laid-Open No. 2008-134522 Patent Document 2: Japanese Patent Application Laid-Open No. 2009-116090 Patent Document 3: Japanese Patent Application Laid-Open No. 2009-015492 Patent Document 4: Japanese Patent Application Laid-Open No. 2007-207124 Each of 3 is included in the present invention, and the contents disclosed in Patent Documents 1 to 4 are part of the disclosure of this specification.

  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. Further, the method of calculating coordinates based on current disclosed in Patent Document 4 discloses converting current to voltage, but is calculated based on average current. It takes a long time to calculate the coordinates.

  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 log signal ratio indicating a log signal ratio of the second output voltage, and an object approaches or contacts the insulating film based on the first log signal ratio And a third circuit (detection circuit) for deriving the coordinate position of at least 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 log signal ratio indicative of the log signal ratio associated with the voltage at the first and second nodes on the axis, and calculating the log signal ratio associated with the voltage at the third and fourth nodes on the Y axis. A second logarithmic signal ratio is generated, and coordinates of an object approaching or contacting the XY plane of the insulating film formed on the conductive film are derived based on the first and second logarithmic signal ratios. .

  According to the present invention, by generating a plurality of log signal ratios respectively corresponding to a plurality of nodes, for example, the coordinates of the position where an object approaches or contacts the XY plane of the insulating film formed on the conductive film can be obtained. It can be detected accurately and at high speed.

FIG. 1A is a cross-sectional view illustrating a configuration of a substrate of a touch panel, and FIG. 1B is a diagram illustrating an overall configuration of a touch panel according to an embodiment of the present invention. FIG. 2A is a diagram showing the resistance from the nodes A and B to the contact position and the capacitance at the contact position of the touch panel according to the embodiment of the present invention, and FIG. 2B is for the Step waveform at the nodes A and B. It is a response curve. It is a figure which shows the capacity | capacitance in the resistance and distance from the nodes A and B of the touchscreen which concern on the Example of this invention to a touch position, and a contact position. Time transition of output waveform at nodes A and B on the touch panel. It is a figure which shows the difference outputs V (alpha) and V (beta) from a saturation output. It is a figure which shows numerical formula expansion which took the numerical expression of difference output V (alpha), V (beta) from the saturated output in the nodes A and B of a touch panel, the logarithm display of V (alpha), V (beta), and ratio of both. It is a figure explaining the measurement principle of the voltage between the nodes A and B of a touch panel. It is a figure explaining the measurement principle of the voltage between the nodes A and B of the touch panel, and the voltage between 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 explaining the detection principle of two-point contact 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 the 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 is a thin sheet-like transparent insulating protective film 16, for example, a resin sheet such as a polyester sheet, or a higher elastic modulus and rigidity than a resin such as glass (preferably tempered glass, multilayer glass, multilayer glass). It may be covered with a hardness sheet having Typically, the touch panel 10 is modularized or integrated with a display display (for example, a liquid crystal panel, an organic electro-luminescence 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 illustrating 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 generates a reference pulse signal (a square wave shown in FIG. 2B, which will be described later), preferably at a constant frequency, for example, 1 MHz. The DC bias may be added. 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 in (see FIG. 1B), and a weak current flows from each node 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 log signal ratio between the nodes A and B on the X axis as described later. , And a process of extracting the log signal ratio between the nodes A and D on the Y axis. 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 the present embodiment will be described. In this embodiment, as shown in FIG. 1B, in a capacitive touch panel, logarithmic signal ratios of two nodes A and B on the X axis and two nodes A and D on the Y axis. The contact position is detected using.

  As shown in FIG. 2A, when the contact position P on the touch panel is touched, the nodes A and B on the X axis have resistances Ra and Rb, capacitances as shown in FIG. Voltage signals Va and Vb determined by a time constant by Cxy are generated. Although not shown here, the voltage signals Va and Vd determined by the time constants of the resistors Ra and Rd are similarly generated at the nodes A and D on the Y axis. Each transition of the voltage signals Va and Vd is a potential for a predetermined time in a transient area due to a CR time constant. 2B indicates a reference pulse signal (common node N in FIG. 1B) that the reference potential generation circuit 20 supplies to each of the nodes A to D. The upper side of the rectangular wave is the saturation output potential (5v). The bottom side (lower side) of the rectangular wave is 0v. The transition period of the potential between 0v and 5v is the non-saturated output potential.

  As shown in FIG. 3, when the touch position P1 on the touch panel is a touch location, resistances Ra and Rb and a capacitance Cxy are generated between the nodes A, B and P1 on the X axis as shown in the figure. The resistors Ra and Rb are uniquely proportional to the distances Da and Db between the nodes A and B and P1, and have a substantially proportional relationship. This proportionality coefficient depends on the position of P1. This proportionality coefficient becomes almost constant when P1 is not in the peripheral portion of the panel.

  As shown in FIG. 4, step waveform response voltage signals Va and Vb at nodes A and B have waveforms determined by the time constants of capacitance Cxy and resistors Ra and Rb. Is shown in FIG. 4 as Vα and Vβ. Here, Vα and Vβ take outputs after a certain time (t0) from the rising edge of the pulse.

  FIG. 5 shows mathematical expressions of differential outputs Vα and Vβ from saturated outputs at nodes A and B of the touch panel, logarithmic display of Vα and Vβ, and a ratio of the two. k is a constant, and by taking the logarithmic ratio, this constant disappears, becomes the ratio of resistances Ra and Rb between P1 and nodes A and B, and becomes the ratio of distances Da and Db. Thereby, the distance ratio is obtained from the nodes A and B of the contact position P1 by taking the logarithmic signal ratio of the difference outputs Vα and Vβ.

  FIG. 6 is a diagram for explaining the principle of 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 viewed as a logarithmic ratio, the ratio of the distance a and the distance b from the nodes A and B to the contact position P is obtained.

  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 considered. As shown in FIG. 7, 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 difference outputs from the saturated outputs corresponding to these are denoted as Vα, Vβ, Vγ, and Vζ, respectively. By calculating these logarithms and taking their ratios, the X coordinate and Y coordinate of the contact position can be obtained.

  The position detection algorithm using the logarithmic ratio according to the present embodiment is organized as follows. Reference pulse signals are simultaneously input to the four nodes A to D, and the output waveforms of the two nodes of the X axis and the Y axis are measured. The difference output from the saturation output after a certain time (t0) from the rising edge of the pulse is taken. Next, by taking the logarithm of this and taking the logarithmic ratio of the two nodes with respect to the X axis and Y axis, the ratio of the distances is obtained with respect to the X axis and Y axis. Thereby, the position of the contact position with respect to the X axis and the Y axis is obtained. The sampling interval is performed at a level of 0.01 s (seconds), and noise cancellation is performed from two-point measurement and two-point 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, a preferable configuration of the touch panel of this embodiment will be described. FIG. 8 is a block diagram showing a preferred configuration of the position information extraction unit. In FIG. 8, the position information extraction unit 30 in FIG. 1 receives the output signals of the four nodes A to D and selects two output signals from among them, and the two selected by the selector 100. A log ratio circuit 102 to which an output signal of the node is input, a filter 104 for removing noise of the signal output from the log ratio circuit 102, and an analog / digital conversion of the output signal of the log ratio signal from which the noise has been removed. Contact is detected by the D converter 108, the third circuit (detection circuit) 110 that detects that a finger touches in response to the current flowing through each node, and the third circuit (detection circuit) 110. When detected, the flip-flop circuit 112 that performs selection switching by the selector 100 and the reference clock signal from the reference potential generation circuit 20 are received, Through the scan BUS configured to include a controller 114 are supplied to each section of the various clock signals.

  The third circuit (detection circuit) 110 detects the presence or absence of a finger contact 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 log ratio circuit 102 extracts the log ratio signal of the output signals of the two nodes (A and B or A and D) selected by the selector 100. The output value of the A / D converter 108 that performs analog / digital conversion on the output signal of the logarithmic ratio signal from which noise has been removed is received, converted into a digital value of a predetermined number of bits, and sent to the position detector 40 shown in FIG. provide. The position detection unit 40 detects the contact position by processing the received digital signal as described later.

  Next, the position detection part of a present Example is demonstrated. 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. For example, when the logarithmic signal ratio (data extracted by the position information extraction unit 30) is equal to or less than a first threshold value, the position detection unit 40 determines that there is one approach or contact position, and the first When the log signal ratio is greater than the first threshold value, it is determined that there are at least two approach or contact positions.

  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. Consider the case where the contact point T2 overlaps the contact point T1, as shown in FIG. 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 node A-B on the X axis decreases, the node A-D on the Y axis complements it, so that it can be detected. Similarly, the coordinates of the two contact points can be obtained by detecting also at the nodes BC and CD.

  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.

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: Logarithmic ratio circuit 104: Filter 108: A / D converter 110 : Touch third circuit (detection circuit)
112: flip-flop circuit 114: controllers P1, T1, T2: contact positions A, B, C, D: nodes

Claims (10)

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) for generating a first log signal ratio indicating the log signal ratio of the first and second output voltages 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 log signal ratio;
A position detecting device. The clock signal is a rectangular wave;
The position detection device according to claim 1, wherein each of the first and second output voltages is a voltage corresponding to the clock signal and related to a time constant. 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 log signal ratio indicating a log signal ratio of the third and fourth output voltages obtained from the third and fourth nodes, respectively;
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 log signal ratios. Position detection device. The third circuit (detection circuit) compares the first logarithmic signal ratio with a first threshold value, and approaches when the first logarithmic signal ratio is equal to or less than the first threshold value. 2. A determination unit that determines that the number of contact positions is one and that determines that there are at least two approaches or contact positions when the first log signal ratio is greater than a first threshold value. Or the position detection apparatus of 2. The position detection device according to claim 1, wherein the second circuit (extraction circuit) includes a filter that removes noise of the first log signal ratio. The third circuit (detection circuit) includes a processing unit that averages digital signals corresponding to the plurality of first log signal ratios within a certain period provided from the second circuit (extraction circuit). The position detection device according to claim 1 or 2. The position detection apparatus according to claim 3, further comprising a normalization unit that normalizes the first and second log signal ratios. 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 log signal ratio indicative of a log signal ratio associated with the voltage at the first and second nodes on the X axis, and a log signal ratio associated with the voltage at the third and fourth nodes on the Y axis; Generate a second log signal ratio indicative of
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 log signal ratios. The clock signal is a rectangular wave;
9. The position detection device according to claim 8, wherein each of the first and second log signal ratios is a ratio corresponding to the clock signal and related to a time constant. The position detection method further compares at least one of the first and second logarithmic signal ratios with a first threshold value, and when the ratio is equal to or less than the first threshold value, the approach or contact position is one. The position detection method according to claim 8 or 9, wherein it is determined that the approach or contact position is at least two when it is greater than a first threshold value.

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