JP2016033698A - Coordinate input system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coordinate input system using plural frequency without decreasing of responsibility for an indication of a finger or a coordinate indicator by measuring standard values for plural frequencies.SOLUTION: In a coordinate input system, when it is distinguished that a measurement result of current of four detection electrodes satisfies a requirement to switch frequency, if it is judged that a touch with a finger or a coordinate indicator is not carried out, a frequency of an alternating current signal source is changed to a different frequency, and if it is judged that the touch is carried out, the frequency of the alternating current signal source is changed to the different frequency after judging that the touch is finished.SELECTED DRAWING: Figure 1

Description

The present invention relates to a coordinate input system that detects a position touched by a finger or a coordinate indicator, a so-called touch panel.

First, a surface-type electrostatic coupling type coordinate input system will be described. FIG. 4 shows a coordinate input panel 1 having a rectangular coordinate input area 8, and a resistive surrounding surrounding the surface resistor 2 so as to be electrically connected to the surface resistor 2. An electrode 3 is disposed, and detection electrodes 4, 5, 6, and 7 are provided at four vertices. The detection electrodes 4, 5, 6, and 7 are electrically connected to the resistive surrounding electrode 3. The coordinate input area 8 is on the surface resistor 2 and inside the resistive surrounding electrode 3.

As a coordinate detection method of the coordinate input system using the coordinate input panel 1, the position of the point indicated by the finger or the coordinate indicator is caused by voltage oscillation of the entire surface resistor 2 and capacitive coupling or direct contact. Is known on the input panel side. For example, an A / D converter (analog / digital converter) is converted into a direct current by converting an alternating current flowing in and out of one point of the surface resistor 2 to four apexes (4, 5, 6, and 7). ) And the like, and the coordinates are calculated based on those current values (see Japanese Patent No. 3237629 (Patent Document 1)). A coordinate input system using such a method is called a surface-type touch panel.
In addition, as one type of surface-type touch panel, four vertices are divided into two pairs with two diagonals as one set, and two sets are alternately selected to supply current to the two vertices of those diagonals. A diagonal system that distributes is known (see Japanese Patent No. 4168537 (Patent Document 2)).
“Instructing” a “point” with a finger or a coordinate indicator means that the user touches a point corresponding to a certain position coordinate in the coordinate input area 8 with the finger or the coordinate indicator held by the user. Means that. The finger or coordinate indicator includes not only the fingertip but also a hand or other human body part, a touch pen having a tip formed of a conductive material, and the like.

In a surface-type touch panel, generally, a display device such as a liquid crystal is often installed below the coordinate input panel 1. Even when the finger or the coordinate indicator does not indicate one point of the surface resistor 2 due to electrostatic coupling between the surface resistor 2 and the display device, current flows through the four apexes. The same phenomenon occurs when metal is used for the housing of the apparatus incorporating the coordinate input system. Under such conditions, for example, when the finger indicates one point of the surface resistor 2, the current caused by the finger is distributed to the four apexes in addition to the current. When obtaining the coordinates designated by the finger, it is necessary to exclude from the calculation the current value when the finger is not designated. For this reason, when the finger or the coordinate indicator does not indicate one point of the surface resistor 2, a method of measuring the current value flowing at the four apexes and holding it as a reference value is known.

In the surface-type touch panel, an independent detection for detecting that the finger has physically touched the surface of the surface resistor 2 (or any coating formed on the surface resistor 2) inside the coordinate input area 8 itself. In many cases, this means is not provided. Instead, a touch detection unit is provided that uses the current value flowing in the detection electrodes 4 to 7 to measure the coordinates indicated by the finger. The touch detection means is such that the total value of the net current value obtained by subtracting the reference value of each vertex from the current value flowing through the four vertices does not change so much depending on the position indicated by the finger within the coordinate input area 8. When the total value of the net current becomes larger than a predetermined threshold value by using the fact that the distance between the finger and the surface resistor 2 changes greatly, and the distance between the finger and the surface resistor 2 increases. Then, it is determined that the finger has touched the surface resistor 2.

When the finger or the coordinate indicator does not indicate one point of the surface resistor 2, the magnitude of the current flowing through the four vertices varies depending on, for example, a change in ambient temperature. Accordingly, the reference value is not measured only when the coordinate input system is activated, for example, and is repeatedly measured and updated almost regularly when the finger or the coordinate indicator does not indicate one point of the surface resistor 2. It is necessary to continue.

On the other hand, depending on the installation environment of the apparatus incorporating the coordinate input system, various noises can be mixed in the coordinate input system. In general, it is possible to cope with such noise by using a band-pass filter that passes the frequency that causes the surface resistor 2 to vibrate, but the frequency is close to the frequency that causes the surface resistor 2 to vibrate. If there is a noise, the measured value of the current flowing at the four vertices is affected by the noise, and accurate coordinates may not be calculated. In such a case, a method of switching the frequency that causes the surface resistor 2 to vibrate to another frequency is known (see Japanese Patent Laid-Open No. 2006-108553 (Patent Document 3)).

When a method of switching a plurality of frequencies according to the situation is used, the reference value of the current flowing at the four vertices when the finger or the coordinate indicator does not indicate one point of the surface resistor 2 is also a plurality of frequencies. Everything needs to be updated. This is because the reference values are generally not equal to each other for a plurality of frequencies. When the finger or the coordinate indicator does not indicate one point of the surface resistor 2, the coordinate input system switches to all of a plurality of frequencies in addition to the currently used frequency almost regularly. Measure the value.

Japanese Patent No. 3237629 Japanese Patent No. 4168537 JP 2006-104853 A

When measuring the reference value, it takes a certain time to measure all of the plurality of frequencies. In addition, when sequentially switching to all of a plurality of frequencies, it may be necessary to wait until the output of the bandpass filter and the rectifier circuit that converts to DC becomes stable. When the finger or the coordinate indicator does not indicate one point of the surface resistor 2, the measurement is performed almost regularly. On the way, for example, when the finger comes close to the surface resistor 2, It is necessary to stop the measurement of the reference value and restart the coordinate detection. However, at this time, if you are trying to measure a reference value of a frequency that is not currently used, you must wait for a certain amount of time before switching to the current frequency and stabilizing the circuit output. In some cases, responsiveness to finger instructions may be reduced.
The present invention has been made in consideration of such points, and in a coordinate input system using a plurality of frequencies, the response to a finger instruction is not lowered by measuring the reference values for the plurality of frequencies. An object of the present invention is to provide such a coordinate input system.

According to the present invention, at least a rectangular coordinate input area having a single surface resistor formed thereon and a rectangular coordinate input area and four sides constituting the outer edge of the rectangular coordinate input area are in electrical contact with the surface resistor. A linear resistive peripheral electrode provided with a constant resistance value per unit length and at least equal resistance values per unit length between opposing sides, and four rectangular coordinate input areas A detection electrode provided at the apex so as to be in electrical contact with the resistive surrounding electrode; an AC signal source capable of switching to a plurality of different frequencies that vibrates the four detection electrodes; It is determined whether the current measurement means for measuring the current flowing through the four detection electrodes and the measurement result of the current flowing through the four detection electrodes are affected by disturbance noise and satisfy the frequency switching condition. Touch for discriminating whether the finger of the user or the coordinate indicator touches the surface of the coordinate input area based on the change in the total value of the measurement results of the currents flowing through the four detection electrodes. When the position in the coordinate input area is indicated by a finger or a coordinate indicator, the coordinate input area indicated by the finger or the coordinate indicator is obtained from the measurement result of the current flowing through the four detection electrodes. A coordinate calculation means for calculating the position in the position, a smoothing means for smoothing the measurement result of the current measured by the current measurement means or the position coordinates calculated by the coordinate calculation means in time series, and the coordinate calculation means Coordinate output means for outputting the position coordinates calculated by the above to the host device, and the frequency switching condition discriminating means is an electric current flowing through the four detection electrodes. If it is determined that the measurement result satisfies the condition for switching the frequency, the frequency of the AC signal source is set to a different frequency if the touch detection unit determines that the touch is not performed by the finger or the coordinate indicator. If it is determined that switching or touching is being performed, it is determined that the touch is no longer performed, and then the frequency of the AC signal source is switched to a different frequency.

According to the coordinate input system of the present invention, in the coordinate input system using a plurality of frequencies, it is possible to prevent a decrease in responsiveness to an instruction from a finger or a coordinate indicator.
In addition, when a certain amount of noise needs to be switched while touching, it is possible to temporarily increase the degree of smoothing so as not to degrade the coordinate quality.

Schematic diagram showing the embodiment Flowchart representing the operation of the first embodiment Flowchart representing the operation of the second embodiment Schematic diagram showing a rectangular coordinate input panel

Hereinafter, preferred embodiments of a coordinate input system according to the present invention will be described in detail with reference to the accompanying drawings.

<First Embodiment>
FIG. 1 is a schematic diagram illustrating an example of a coordinate input system according to the first embodiment. 1 is a configuration diagram of a coordinate input system that detects a position ((X, Y) coordinates) indicated by a finger 21 or a coordinate indicator (hereinafter referred to as a finger 21) in a coordinate input area 18 of a coordinate input panel 11. FIG. The surface resistor 12 is uniformly formed on one surface of transparent glass, resin, or opaque insulating base material by coating, vapor deposition, or the like. The surface of the surface resistor 12 may be insulated so that the finger 21 does not directly touch the surface resistor 12, thereby transmitting a signal by capacitive coupling between the finger 21 and the surface resistor 12. However, the signal may be transmitted by direct electrical contact between the finger 21 and the surface resistor 12 without performing an insulation process.

A rectangular resistive surrounding electrode 13 with each side being a straight line is disposed in close contact with or around the uniform surface resistor 12, and the inside of the resistive surrounding electrode 13 is defined as a rectangular coordinate input region 18. On the resistive surrounding electrode 13, the positions corresponding to the four vertices of the rectangular coordinate input region 18 are set as the detection electrodes 14 to 17, and lead lines 22 to 25 are connected to the detection electrodes 14 to 17 respectively. The lead lines 22 to 25 generally include external resistance components 26 to 29, respectively. The lead wires 22 to 25 are connected to the oscillating voltage application circuit 31 in the analog signal processing unit 30.

When detecting the coordinates, an oscillating voltage generator 32 serving as an AC signal source applies an oscillating voltage to the oscillating voltage applying circuit 31, and the oscillating voltage applying circuit 31 causes the detection electrodes 14 to 17 to vibrate with low impedance, and The current flowing from the detection electrodes 14 to 17 to the analog multiplexer 33 is output. As a simple example, the transistor base is vibrated by an AC signal, the emitter is connected to a detection electrode, and current is output from the collector.

The entire surface of the sheet resistor 12 is vibrated by the oscillating voltage generator 32 as an AC signal source. As is known in the art, the human body has a grounding effect on the AC signal. When the human finger 21 contacts or approaches the surface resistor 12, the surface resistor is passed through the fingertip by capacitive coupling. AC current flows between The detection electrodes 14 to 17 include an analog multiplexer 33 that passes the signal of one of the detection electrodes, a band-pass filter 34 corresponding to the frequency of the AC signal generated by the oscillating voltage generator 32, and a rectifier circuit 35. In this way, a voltage proportional to the amount of current flowing through each detection electrode is applied to the A / D converter 36. For this reason, the value of the current flowing from the fingertip through the surface resistor 12 and distributed to the detection electrodes 14 to 17 can be obtained as a digital value as a digital value.
The oscillating voltage generator 32 has a function of generating oscillating voltages having a plurality of frequencies by switching between them. The band-pass filter 34 has a function of similarly switching to a filter having parameters corresponding to a plurality of frequencies generated by the vibration generator 32.

The CPU 37 sequentially switches the analog multiplexer 33, inputs the digital value output from the A / D converter 36, and calculates the coordinates of the indicated position of the finger 21 by a method as described later. The CPU 37 outputs the result of touch detection and coordinate calculation to a subsequent device. Further, lower-level data such as a digital value output from the A / D converter 36 may be output to a subsequent apparatus so that touch detection and coordinate calculation may be performed by the subsequent apparatus.

The surface resistor 12 is made of an opaque carbon film, a transparent ITO (indium tin oxide) film formed by sputtering, a NESA (tin oxide) film formed by CVD, or the like uniformly on a substrate. The film is formed, and the sheet resistance is preferably about 1 kΩ / □. For example, soda glass can be used as the substrate, but the material is not particularly limited, and any glass material or a transparent resin material such as an acrylic resin or a polyethylene resin can be used. Depending on the application, an opaque insulating substrate may be used.

A rectangular resistive surrounding electrode 13 whose sides are straight is provided around or inside the single-connected sheet resistor 12 so that all sides are in electrical contact with the sheet resistor 12. Here, the single connection means that the surface resistor 12 has a shape such that there is no isolated hole in the interior, and is connected to one another. However, as long as it does not hinder the macroscopic flow of current inside the surface resistor 12, such as a hole about the size of a pinhole generated on the surface resistor 12 according to the film formation method, It doesn't matter at all. Further, when a larger hole is generated due to an injury or the like, the coordinates are distorted according to the size of the hole at least around the hole, but the influence on the coordinate calculation of the indicated position of the finger 21 is small as the distance from the hole is increased. Therefore, if the hole is small, there is no practical problem.

The resistive surrounding electrode 13 surrounding the surface resistor 12 is formed by closely arranging carbon, silver carbon, silver, or the like. For example, a technique such as screen printing and baking of conductive ink such as silver ink is used. Create with. Each side of the resistive surrounding electrode 13 may be a straight line having a width, or low resistance conductive elements are arranged separately from each other and formed by utilizing the resistance of the surface resistor 12. But you can. The resistive surrounding electrode 13 makes the resistance value per length constant for each side, and at least equals the resistance value per length of the upper and lower sides of the rectangle and the resistance value per length of the left and right sides.
Further, the resistance value of the resistive surrounding electrode 13 is preferably lower than the resistance value of the sheet resistor 12. When the sheet resistance value of the sheet resistor 12 is about 1 kΩ / □, The resistance value between adjacent vertices is preferably about 20 to 200Ω.

The detection electrodes 14 to 17 at the respective apexes are for connecting lead wires, and are formed by printing and baking a solderable conductive ink. When the same conductive ink as the resistive surrounding electrode 13 can be used as the conductive ink for forming the detecting electrodes 14 to 17, the detecting electrodes 14 to 17 and the resistive surrounding electrode 13 are It is possible to form by printing and baking by processing.

The external resistance components 26 to 29 are the total of the resistance components included in elements such as the resistances of the lead wires 22 to 25 and the oscillating voltage application circuit 31 for each path emanating from each of the detection electrodes 14 to 17. Generally, the resistance inherent in the lead lines 22 to 25 occupies a large portion of them.
In the case of using sufficiently low resistance lead wires or the like as the lead wires 22 to 25, the external resistance components 26 to 29 are extremely smaller than the resistance value of the resistive surrounding electrode 13, and in calculating the coordinates, It will not be necessary to consider it independently. On the other hand, for example, when the extension of the lead wires 22 to 25 is long or the resistance is relatively high depending on the material and shape of the lead wires 22 to 25, the external resistance components 26 to 29 become large. If the resistance value of the resistive surrounding electrode 13 or the external resistance components 26 to 29 is not sufficiently lower than the resistance value of the surface resistor 12, it is necessary to correct the coordinates according to the magnitude of the resistance value. is there.

The resistive surrounding electrode 13 has a finite width because it needs to be formed by a technique such as printing and to connect the lead wires 22 to 25 to the detection electrodes 14 to 17. At this time, at least at the boundary line between the resistive surrounding electrode 13 and the sheet resistor 12, the resistive surrounding electrode 13 and the sheet resistor 12 need to be in electrical contact. Usually, the resistive surrounding electrode 13 is formed after the surface resistor 12 is formed. However, the surface resistor 12 may protrude outside the resistive surrounding electrode 13. Also in this case, the coordinate input area 18 is inside the area surrounded by the resistive surrounding electrode 13.

The shape of the resistive surrounding electrode 13 and the surface resistor 12 may be any shape as long as it can be accommodated in the substrate, and the shape of the resistive ambient electrode 13 and the sheet resistor 12 and the substrate need not be substantially matched. It is preferable that the shape of the base electrode is the same as the shape of the surrounding electrode 13 and the surface resistor 12 because the degree of freedom in designing the incorporated product is increased when the coordinate input system is incorporated into any product. When a conductive pattern is formed outside the resistive surrounding electrode 13 as a part of the lead wires 22 to 25, it is necessary to prevent the sheet resistor 12 from overlapping the conductive pattern.

Next, a method for calculating the coordinates of the designated position of the finger 21 will be described. For convenience, names are given to the four vertices of the rectangular coordinate input area 18, and the vertices corresponding to the detection electrodes 14 to 17 are called vertices A to D, respectively. Now, when the finger 21 is touching the coordinate input area 18 of the coordinate input panel 11, the current flowing to the detection electrode 14 (vertex A) among the current flowing from the fingertip to the coordinate input panel 11 through the surface resistor 12 is calculated. A value measured by the A / D converter 36 is measured value A, a value obtained by measuring the current flowing through the detection electrode 15 (vertex B) is measured value B, and a value obtained by measuring the current flowing through the detection electrode 16 (vertex C) is measured. A measured value D is a value obtained by measuring the current flowing through C and the detection electrode 17 (vertex D).

The CPU 37 stores the current values flowing through the detection electrodes 14 to 17 as reference values in a state where the finger 21 does not touch the coordinate input area 18 of the coordinate input panel 11, and measures and updates the current values almost regularly. . The reference value of the detection electrode 14 is Ab, the reference value of the detection electrode 15 is Bb, the reference value of the detection electrode 16 is Cb, and the reference value of the detection electrode 17 is Db. The net current value resulting from the touch of the finger 21 is an increment from the reference value for each of the detection electrodes 14 to 17, An = A−Ab, Bn = B−Bb, Cn = C−Cb, Dn = It can be calculated as D-Db.
The CPU 37 compares the total net current value (An + Bn + Cn + Dn) with a predetermined threshold value. If the total net current value is equal to or greater than the threshold value, an instruction by the finger 21 or the coordinate indicator, that is, touch is performed. It is determined that

At this time, the coordinates (X, Y) of the position indicated by the finger 21 are X = a × (−An + Bn + Cn−Dn) / (An + Bn + Cn + Dn), Y = b × (−An−Bn + Cn + Dn) / in the orthogonal coordinate system XY. It is known that it is obtained by (An + Bn + Cn + Dn). However, in the orthogonal coordinate system XY, the center of the coordinate input area 18 is the origin, the X axis is positive in the direction from the detection electrode 14 to the detection electrode 15, and the Y axis is positive in the direction from the detection electrode 14 to the detection electrode 17. And a and b indicate distances from the origin to the boundary of the coordinate input area 18 in the X direction and the Y direction, respectively.

The coordinates of the position indicated by the finger 21 as a calculation result are affected by electrical noise or the like. Even when the noise is small enough not to satisfy the frequency switching condition described later, the coordinate calculation result may be affected. For this reason, the coordinates of the finger 21 that are continuously detected include fine fluctuations in addition to the actual movement of the finger 21. In addition, small fluctuations in coordinates also occur due to tremors and motion blurs that are not intended by the user. A series of coordinate sequences measured and calculated until the coordinates of the finger 21 become smaller than the threshold after the sum of the net current values is equal to or greater than the threshold include the above-described fine variations. . The coordinate input system includes a coordinate smoothing means that removes these fine variations almost instantaneously. Specifically, a moving average, an infinite impulse response type digital low-pass filter, or the like can be used as a smoothing means for a discrete series of numerical values. The smoothing means may be applied to the measurement values A to D, or may be applied to the coordinates X and Y that are the calculation results.

The operation related to the update of the reference value will be described with reference to FIG.
After starting, the coordinate input system selects a predetermined frequency and performs an initial measurement of a reference value (S101). Thereafter, touch / coordinate detection (S102) is performed, and it is evaluated whether or not the measurement values A to D are affected by noise and satisfy a condition for switching frequencies (S103). This evaluation is performed by, for example, performing several measurements to obtain one measurement value A, evaluating the magnitude of variation between these numerical values, and if the variation is greater than a predetermined threshold, Is affected by noise and satisfies the condition for switching frequencies.

If the condition for switching the frequency is not satisfied, the result of touch / coordinate detection is output to the subsequent apparatus (S104). This output may be performed only when a touch with the finger 21 is detected, or information indicating that it has not been detected may be output when it is not detected. While a predetermined time (for example, several seconds to several tens of seconds) determined as a reference value update period to be performed almost regularly has not elapsed (S105), touch / coordinate detection (S102), noise evaluation (S103), and results (S104) is repeated. When the specified time has elapsed (S105), the measurement of the elapsed time is reset and the reference value is measured (S106). Whether or not this measurement value also satisfies the condition for switching the frequency is evaluated (S107).

If the condition is not satisfied, the net current values An to Dn are obtained by subtracting the reference values Ab to Db held at that time for the measurement values A to D of the detection electrodes 14 to 17. The total of the net current values (An + Bn + Cn + Dn) is compared with a predetermined threshold. If the total of the net current values is smaller than the threshold, the finger 21 is not touched when measuring the reference value, and the reference It is determined that the value can be updated properly (S108), the held reference values Ab to Db are updated with the measured values A to D (S109), and the process returns to touch / coordinate detection (S102).
If the sum of the net current values is equal to or greater than a predetermined threshold, it is determined that the touch with the finger 21 is being performed (S108). In this case, the reference value is not updated, and the process proceeds to a result output (S104). Since the value measured for updating the reference value can be used to calculate the coordinates touched by the finger 21, it is possible to prevent the responsiveness from being lowered due to the measurement of the reference value.

In the noise evaluation (S103) after the touch / coordinate detection (S102) and the noise evaluation (S107) after the reference value measurement (S106), the conditions for switching the frequency are affected by the noise. If it is determined that the total current value is satisfied, it is checked whether or not the total net current value is equal to or greater than a predetermined threshold (S111), and the frequency is not changed as long as the total net current value exceeds the threshold. The touch / coordinate detection (S110) and the evaluation (S111) of whether the sum of the net current values is equal to or greater than the threshold value are repeated. At this time, the coordinates are not calculated and the result is not output to a subsequent device, but if the subsequent device needs information that the touch is completed, such information is output. You may do it. In this case, if coordinate information is required, the latest coordinate information that has been established so far may be used.

When evaluating whether or not the sum of the net current values is equal to or greater than the threshold value (S111), the measured value of the net current is influenced by noise, and it seems that the degree of total vertical movement is large. In evaluating whether or not the sum of the net current values is smaller than the threshold value, it is necessary to consider such a condition, for example, if it is smaller than the threshold value several times in succession, or the like. When it is determined that the sum of the net current values is smaller than the threshold value and the finger 21 is separated from the surface resistor 12, the frequency is switched to another frequency other than the current frequency considered to be affected by noise (S112). . Thereafter, after the circuit is stabilized, the reference value of the newly selected frequency is measured, the reference value is updated (S113), and the process returns to touch / coordinate detection (S102).

As a result, frequency switching is not performed unless it is determined that the currently used frequency is affected by noise. Therefore, the frequency switching at the time of measuring the reference value and the touch of the finger 21 when batting is performed. There is no reduction in responsiveness. On the other hand, when it is determined that the condition for switching the frequency is satisfied under the influence of noise while the finger 21 is touching, the calculation is performed using the measured value whose reliability is reduced due to the influence of the noise. Since the coordinates are not output to the subsequent apparatus, it is possible to avoid outputting erroneous information.

When the user performs an operation of touching the finger 21 and releasing it relatively quickly, such as a tap, and the condition for switching the frequency is satisfied in the middle of the operation, the feeling of operation is such that the user notices it. It is thought that it does not change. When a long touch on a point or an operation called “drag to move the finger 21 while touching” is satisfied, and the condition for switching the frequency is satisfied in the middle of the operation, the user touches the device in the middle of the user's operation. Input will be interrupted. Since it is considered that the interruption of the input is transmitted to the user by visual or other sensory feedback by the subsequent device, the user may perform the operation again. However, this embodiment is more suitable for use mainly for tap operation than for use mainly for operation such as long press or drag in this respect.

<Second Embodiment>
Details of the second embodiment will be described below with reference to FIGS. In the second embodiment, when it is determined that the condition for switching the frequency is satisfied under the influence of noise while the finger 21 is touching, the total of the net current values becomes smaller than the threshold value. Until it is determined that the finger 21 has moved away from the surface resistor 12, the frequency is not changed and additional processing is performed, and the output of the result is continued. FIG. 3 is a flowchart showing the operation of the present embodiment. Components that are essentially the same as those in the first embodiment are denoted by the same reference numerals as in FIG.

In the noise evaluation (S103) after the touch / coordinate detection (S102) and the noise evaluation (S107) after the reference value measurement (S106), the conditions for switching the frequency are affected by the noise. If it is determined that the total current value is satisfied, it is checked whether or not the total net current value is equal to or greater than a predetermined threshold (S111), and the frequency is not changed as long as the total net current value exceeds the threshold. The touch / coordinate detection (S110) and the evaluation (S111) of whether the sum of the net current values is equal to or greater than the threshold value are repeated.

At this time, the coordinates are calculated by smoothing to a degree stronger than usual, and the result is output to the subsequent apparatus (S114). To increase the degree of smoothing, for example, if the smoothing means is a moving average, the number of averaging processing is increased from that point, or if it is a digital low-pass filter, the cutoff frequency is changed lower. It means changing to a filter. Further, the smoothing for increasing the degree may be applied to the measurement values A to D, or may be applied to the coordinates X and Y that are the calculation results.
When it is determined that the sum of the net current values is smaller than the threshold value and the finger 21 is separated from the surface resistor 12, the frequency is switched to another frequency other than the current frequency considered to be affected by noise (S112). . Thereafter, after the circuit is stabilized, the reference value of the newly selected frequency is measured, the reference value is updated (S113), and the process returns to touch / coordinate detection (S102). At this time, the smoothing level of the smoothing means is restored.

As a result, frequency switching is not performed unless it is determined that the currently used frequency is affected by noise. Therefore, the frequency switching at the time of measuring the reference value and the touch of the finger 21 when batting is performed. There is no reduction in responsiveness. On the other hand, when it is determined that the condition for switching the frequency is satisfied under the influence of noise while the finger 21 is touching, a smoothing process stronger than usual is applied until the frequency is switched. The effect of noise can be reduced. By applying a strong smoothing process, when the user performs a drag operation, there is a possibility that the temporal followability with respect to the dragged trajectory is somewhat deteriorated rather than the responsiveness at the time of touch. In addition, when a curved drag operation is performed, there is a possibility that the curvature radius of the curve constituting the locus is calculated to be smaller than the curvature radius of the locus actually traced by the finger 21. However, if the user completes the touch and switches the frequency to another one, the smoothing process is also restored, so both are temporary.

(Example)
Hereinafter, the present invention will be described by way of examples. The present invention is not limited to the following examples, and includes various modifications within the technical scope of the present invention.

Example 1
The coordinate input panel 11 was created as follows. As a glass substrate, soda glass (thickness 3 mm) cut into a size of about 469 × 375 mm is used, and an ITO (indium oxide) film is formed on the surface of the glass substrate by sputtering. A resistor 12 was obtained. Next, the resistive surrounding electrode 13 and part of the lead wires 22 to 25 are screen-printed with heat-cured paste obtained by mixing carbon in silver paste LS-504 (resin binder) manufactured by Asahi Chemical Research Co., Ltd. It was formed by letting. At this time, the shape of the coordinate input area 18 was a rectangle of 2a = 378 mm and 2b = 303 mm. The width of the resistive surrounding electrode 13 is adjusted so that the resistance value between the vertices AB of the resistive surrounding electrode 13 is about 68Ω and the resistance value between the vertices BC is about 52Ω, and 378/303 = 1.25≈68 / By setting 52 = 1.31, the resistance values per length of all sides of the resistive surrounding electrode 13 were made substantially equal.

Detection electrodes 14 to 17 were formed on the resistive surrounding electrode 13 corresponding to the four vertices of the rectangular coordinate input region 18 by using silver paste. The lead wires 22 to 25 are low resistance lead wires that can ignore the external resistance components 26 to 29.
Further, a transparent insulating base material was formed on the surface resistor 12. In order to form a transparent insulating substrate, a glass paste was printed on the surface resistor 12 and the resistive surrounding electrode 13, heat treated to melt the powdered glass, and sintered. Finally, the lead wires 22 to 25 were connected to the detection electrodes 14 to 17 by soldering. At this time, the sheet resistance of the surface resistor 12 was set to 500Ω / □.

The coordinate input panel 11 created in this way was connected to the hardware created as shown in the block diagram of FIG. In addition, for the configuration of this example, the conditions for switching the frequency were set as follows. For the measurement values A to D corresponding to 16 bits obtained by processing the output value of the A / D converter 36 by the CPU 37, four measurements are carried out to obtain one measurement value, and the maximum value and the minimum value among those values are obtained. If the state where the difference from the value exceeds 200 is measured five times in either the touch / coordinate detection (S102) or the reference value measurement (S106), it is determined that the condition for switching the frequency is satisfied (S103). , S107).

Further, the coordinate data output from the CPU 37 (S104) is taken into a personal computer as a host device by serial communication. If the finger is touched with the finger 21 when the frequency switching condition is satisfied, the CPU 37 stops the output to the host device and determines that the finger 21 has moved away from the surface resistor 12 (S111). (S112), wait for the circuit to stabilize, measure the reference value of the newly selected frequency, update the reference value (S113), and resume output to the host device .

Using a signal generator that generates radio waves of the same frequency as that used when starting the system, noise is placed on the human body and a tap operation into the coordinate input area 18 is detected. I was able to. When the user is not touching, the reference value is not measured by switching to a frequency that is not used at that time, so even if a touch operation is started while switching to a frequency that is not used at that time The responsiveness to it did not decrease.
As a result, it was possible to realize a coordinate input system in which the responsiveness to a finger instruction does not deteriorate.

(Example 2)
Using the coordinate input panel 11 and hardware created in the first embodiment, the operation of the CPU 37 when the finger 21 is touched when the frequency switching condition is satisfied was changed. If the finger is touched with the finger 21 when the frequency switching condition is satisfied, the CPU 37 does not change the frequency and applies a smoothing unit that increases the degree of coordinates to the calculation result to the host device. Output (S114). When it is determined that the finger 21 has moved away from the surface resistor 12 (S111), switching to another frequency (S112), waiting for the circuit to stabilize, measuring the reference value of the newly selected frequency, and updating the reference value (S113) to restore the level of smoothing.

For smoothing, a moving average is used, and during normal operation (S102, S104), M _i = (R _i + R _i-1 +... + R _{i− (N−1)} ) / N is used, With N = 4, the X and Y coordinates were each smoothed. When the coordinates became undetectable from the undetectable state, all the terms were initialized with the current values. If the finger 21 is touched when the frequency switching condition is satisfied, the frequency is changed to N = 8, and the oldest value held at that time, R _i−3, is not discarded. Replicate to _i-4 , R _i-5 , R _i-6 , and R _i-7 . Thereafter, until it is determined that the finger 21 has moved away from the surface resistor 12 (S111), smoothing with N = 8 and increasing the degree is performed.

While the user is dragging into the coordinate input area 18, noise is generated on the surface resistor 12 using a signal generator that generates a radio wave having the same frequency as that used when the system is started. I was able to continue to detect drag operations. When the user is not touching, the reference value is not measured by switching to a frequency that is not used at that time, so even if a touch operation is started while switching to a frequency that is not used at that time The responsiveness to it did not decrease.
As a result, it was possible to realize a coordinate input system in which the responsiveness to a finger instruction does not deteriorate.

DESCRIPTION OF SYMBOLS 1 Coordinate input panel 2 Surface resistor 3 Resistive surrounding electrode 4, 5, 6, 7 Detection electrode 8 Coordinate input area 11 Coordinate input panel 12 Surface resistor 13 Resistive surrounding electrode 14, 15, 16, 17 Detection electrode 18 Coordinate Input region 21 Fingers 22, 23, 24, 25 Lead lines 26, 27, 28, 29 External resistance component 30 Analog signal processing unit 31 Oscillating voltage application circuit 32 Oscillating voltage generator 33 Analog multiplexer 34 Band pass filter 35 Rectifier circuit 36 A / D converter 37 CPU

Claims (3)

A rectangular coordinate input region that is at least a single connection with a surface resistor formed thereon, and provided on the four sides constituting the outer edge of the rectangular coordinate input region so as to be in electrical contact with the surface resistor. A linear resistive peripheral electrode having a constant resistance value per unit length and at least equal resistance values per unit length between opposing sides, and the resistance at four vertices of the rectangular coordinate input region A detection electrode provided in electrical contact with the surrounding electrode, a plurality of AC signal sources capable of switching the frequency of the four detection electrodes to different frequencies, and the four detection electrodes Current measuring means for measuring the current flowing through
Frequency switching condition determining means for determining whether the measurement result of the current flowing through the four detection electrodes is affected by disturbance noise and satisfies the condition for switching the frequency;
Touch detection means for determining whether a finger of a user or a coordinate indicator touches the surface of the coordinate input area according to a change in a total value of measurement results of currents flowing through the four detection electrodes;
When the position in the coordinate input area is indicated by a finger or a coordinate indicator, the position in the coordinate input area indicated by the finger or the coordinate indicator is determined from the measurement result of the current flowing through the four detection electrodes. Coordinate calculation means for calculating,
Smoothing means for smoothing the measurement result of the current measured by the current measuring means, or the position coordinates calculated by the coordinate calculating means, in chronological order;
Coordinate output means for outputting the position coordinates calculated by the coordinate calculation means to the host device;
Have
When the frequency switching condition determination unit determines that the measurement result of the current flowing through the four detection electrodes satisfies the frequency switching condition, the touch detection unit is touched by the finger or the coordinate indicator. If not, the frequency of the AC signal source is switched to a different frequency. If it is determined that the touch is being performed, the frequency of the AC signal source is switched to a different frequency after it is determined that the touch has been stopped. Coordinate input system characterized by that. If the frequency switching condition determining means determines that the measurement result of the current flowing in the four detection electrodes satisfies the condition for switching the frequency, and if it is determined that the touch is performed, the coordinate output means 2. The coordinate input system according to claim 1, wherein the output is stopped and the output by the coordinate output unit is restarted after determining that the touch is stopped. When the frequency switching condition determining unit determines that the measurement result of the current flowing through the four detection electrodes satisfies the condition for switching the frequency, and determines that the touch is performed, the smoothing unit The coordinate input system according to claim 1, wherein the degree of smoothing is strengthened and the degree of smoothing by the smoothing unit is restored after it is determined that the touch has been stopped.

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