JP2014106836A - Coordinate input system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coordinate input system having coordinate smoothing means excellent in followability and fluctuation removability.SOLUTION: First smoothing means such as a low-pass filter and second smoothing means such as moving average are provided, the first and second smoothing means are initialized at a time point when a transition is made from a state where a coordinate of coordinate indication means such as an input pen or a finger cannot be detected in a coordinate input area to a state where it can be detected, and thereafter, while the coordinate of the coordinate indication means can be detected, the first smoothing means and the second smoothing means are applied in turn to the coordinate of the coordinate indication means.

Description

The present invention relates to a coordinate input system that detects the position and touch state of a finger or an input pen.

Conventionally, a pen tablet and a touch panel are known as devices for inputting a user's writing operation. For example, FIG. 6 shows a coordinate input panel 1 having a rectangular coordinate input surface 8, and a resistive surrounding surrounding the surface resistor 2 so as to be electrically connected to the uniform 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 surface 8 is on the surface resistor 2 and is a two-dimensional plane inside the resistive surrounding electrode 3.
As a coordinate detection method of the coordinate input system using the coordinate input panel 1, a signal is transmitted from an input pen which is a coordinate instruction means such as the coordinate input panel 1 being a receiving side, and capacitive coupling or direct contact is performed. The method in which the surface resistor 2 receives a signal transmitted from the input pen via the contact point, and further, the position of the point indicated by the finger or the conductor as the coordinate indicating means by vibrating the entire surface resistor 2 with voltage. Is detected on the input panel side, and the direction of signal transmission is opposite to this, and the coordinate input panel 1 is on the transmission side. There is a method of receiving with an input pen.
In any case, even if the coordinate designating means is not in contact with the coordinate input surface 8 and is floating, the coordinates of the coordinate designating means are up to a certain distance as long as they are floating inside the coordinate input surface 8. Can be detected. The greater the distance from the coordinate input surface 8 of the coordinate indicating means, the smaller the signal and the more difficult the coordinate detection will be. Here, the coordinate input surface 8 and a space on which the coordinates can be detected on the coordinate input surface 8 are referred to as a coordinate input region. The position in the vertical direction from the coordinate input surface 8 of the coordinate instruction means can be obtained to some extent by using the magnitude of the signal as an alternative characteristic, but here, in the case of the coordinates of the coordinate instruction means in the coordinate input area, The two-dimensional coordinates in the coordinate input surface 8 are limited. Further, the size of the coordinate input area in the vertical direction from the coordinate input surface 8 is determined by a limit due to a measurement method, a limit due to required coordinate accuracy, or the like.
When the coordinate input panel 1 is the receiving side, it is known to measure the current value distributed to the four vertices (4, 5, 6, and 7) of the current that enters and exits one point of the surface resistor 2. (See Japanese Patent No. 3237629 (Patent Document 1)). On the other hand, when the coordinate input panel 1 is the transmission side, a potential gradient is given from the outside by connecting the detection electrodes 4, 5, 6, and 7 to the surface resistor 2 by distributing them to a constant potential or ground. A device that detects the voltage level of a designated coordinate point with an input pen as a pointing means is known. The coordinates of the position in the coordinate input area designated by the finger or the input pen which is the coordinate designating means are the distribution values of the current flowing into and out of the surface resistor 2 to the four vertices, or the coordinate designating means when driving the four vertices. It is calculated using the voltage measured with an input pen.
As a method of allocating current to the four vertices or driving the four vertices, a method is known in which current is distributed to all four vertices or all four vertices are distributed to either a constant potential or ground. . Also, the four vertices are divided into two pairs with two at the diagonal as one set, and the two sets are alternately selected to distribute the current to the two vertices of the diagonal, or the two sets are alternately A diagonal method is known in which two vertices of these diagonals are selected and connected to a constant potential and ground to give a potential gradient in the diagonal direction (Japanese Patent No. 4168537 (Patent Document 2)).
When the coordinate input panel 1 is the receiving side and the coordinate indicating means is a finger, the physical surface of the surface resistor 2 (or any coating formed on the surface resistor 2) inside the coordinate input surface 8 is physically Often there is no independent means for detecting the touch itself. Instead, a touch detection unit that uses the current value flowing in the detection electrodes 4 to 7 to measure the coordinates indicated by the finger is provided. The touch detection means is such that the total value of the current does not change so much depending on the position indicated by the finger within the coordinate input surface 8, and changes greatly depending on the distance between the finger and the surface resistor 2. Using the fact that the smaller the distance from the body 2 is, the larger the current is larger than a predetermined threshold value, it is determined that the finger has touched the surface resistor 2. Here, whether or not the finger is touching the surface resistor 2 is expressed by the word “on / off state”. The state that is determined to be touching is referred to as the “on state”, and the other state is referred to as the “off state”. I will decide.
On the other hand, when the coordinate instruction means is an input pen, a switch is provided at the pen tip of the input pen, the coordinates of the input pen are detected within the coordinate input area, and it is determined that the pen tip is in contact with the coordinate input surface 8. The state that is performed is referred to as an on state, and the state that is not is referred to as an off state. For this determination, a mechanical switch may be provided at the pen tip, and it may be recognized as an on state when the switch is pushed in, or a pressure sensor is provided, and an on state is detected when a pressure exceeding a predetermined level is detected. You may make it recognize.
The coordinate input system measures the coordinates of the coordinate designating means and the on / off state of the coordinate designating means several tens of times per second, and the detected coordinates and the on / off status of the coordinate designating means are transmitted to the subsequent apparatus using them. Send.
The detected coordinates of the coordinate indicating means are affected by electrical noise or the like. For this reason, the coordinates of the coordinate instruction means that are continuously detected include fine fluctuations in addition to the actual movement of the coordinate instruction means. In addition, small fluctuations in coordinates occur due to tremors and camera shakes that are not intended by the user. A series of coordinate sequences until the coordinates of the coordinate designating means are detected within the coordinate input area and are no longer detected again include such fine fluctuations. The coordinate input system is required to have good followability with respect to the movement of the coordinate pointing means, and therefore it is necessary to include a coordinate smoothing means for removing these fine fluctuations almost immediately.
Conventionally, the following methods are known for such purposes. For example, Patent Document 3 proposes an apparatus that stores a predetermined number of past coordinate data and removes fine fluctuations by performing a moving average process. Patent Document 4 proposes an apparatus that can smooth a filter and change filter parameters during operation. Further, Patent Document 5 proposes an apparatus capable of switching between two types of averaging means in preparation for the case where the coordinate pointing means moves at high speed.
However, a simple moving average depends on the magnitude of fine fluctuations due to noise, etc., but if the number of average processing is small, the fluctuation cannot be removed sufficiently, while the number of average processing is increased. In some cases, the followability may deteriorate, or even a part of the locus of coordinates that the user intentionally moves may disappear. The devices proposed in Patent Documents 4 and 5 can cope with the above problem by changing the parameters of the filter or switching between two types of smoothing means. Switching is to be performed manually, and it is necessary for the user to set in advance what kind of trajectory to draw using the coordinate designating means.

Japanese Patent No. 3237629 Japanese Patent No. 4168537 JP-A-8-272534 JP-A-8-137608 JP-A-6-214708

The present invention has been made in consideration of such points, and an object of the present invention is to provide a coordinate input system having a coordinate smoothing means excellent in followability and fluctuation elimination.

The present invention relates to a coordinate detection means for detecting the coordinates of a coordinate input means in a coordinate input area composed of a two-dimensional planar coordinate input surface and a space on the coordinate input surface and an on / off state of the coordinate indication means, Coordinate smoothing means for smoothing continuously detected coordinates and transmission means for transmitting the smoothed coordinates and the on / off state to the outside. The coordinate smoothing means includes a first smoothing means and a second smoothing means. The first and second smoothing means are initialized at a time when the coordinate input area is detected from a state in which the coordinates of the coordinate indicating means cannot be detected in the coordinate input area, and thereafter A coordinate input system that applies the first smoothing means to the coordinates of the coordinate indicating means and then the second smoothing means while the coordinates of the coordinate indicating means can be detected is a first gist.

According to the coordinate input system of the present invention, the advantages of both can be utilized by applying the two smoothing means successively. For example, while removing high-speed fluctuations with a low-pass filter, it is possible to remove low-speed and fine fluctuations that cannot be removed with a low-pass filter by further performing moving average processing. By first applying the low-pass filter, a sufficient effect can be obtained without increasing the number of averaging processes so much during the next moving average.
Also, by initializing the smoothing means when the on / off state of the coordinate indicating means changes from off to on, for example, when the trajectory changes particularly rapidly at the start of writing, the on / off state is not considered. In other words, a false trajectory caused by smoothing, which may occur when smoothing is performed, is eliminated.

Schematic diagram showing the first embodiment Schematic diagram showing the second embodiment The figure which shows the coordinate data of a 1st Example and a comparative example (at the time of high-speed drawing) The figure which shows the coordinate data of a 1st Example and a comparative example (at the time of low speed drawing). The figure which shows the coordinate data of 2nd Example Conventional 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, in which the input panel is a receiving side. 2 is a configuration diagram of a coordinate input system that detects a position ((X, Y) coordinates) designated by a finger 21 in a coordinate input area 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 surface 18. On the resistive surrounding electrode 13, the positions corresponding to the four vertices of the rectangular coordinate input surface 18 are set as the detection electrodes 14 to 17, and the 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, the oscillating voltage generator 32 as an AC signal source applies an oscillating voltage to the oscillating voltage application circuit 31, and the oscillating voltage application 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, a transistor base is vibrated by an AC signal, an emitter is connected to a detection electrode, and a current is output from a collector.
The entire surface of the surface resistor 12 is vibrated by the vibration voltage generator 32 serving 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 signal current flows between The detection electrodes 14 to 17 are connected to an A / D converter (analog / digital converter) 34 through an analog multiplexer 33, and a voltage proportional to the current flowing through each detection electrode is applied to the A / D converter 34. 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 CPU 35 includes a ROM and a RAM (not shown) inside, and stores a program in which the procedures of the coordinate detection unit and the coordinate smoothing unit are installed in the ROM. The CPU 35 sequentially switches the analog multiplexer 33, inputs the digital value output from the A / D converter 34, and calculates the coordinates of the indicated position of the finger 21 by a method as described later. Further, the CPU 35 detects the on / off state based on the magnitude of the total value of the digital values output from the A / D converter 34 and the temporal changes thereof.
Further, the CPU 35 smoothes the coordinate calculation result, and transmits the smoothed coordinates and the detected on / off state to the subsequent apparatus. At this time, the CPU 35 may output the coordinates only when the coordinate designating unit is in the on state, or may output the coordinates even in the off state by pairing the on / off state and the coordinates. May be. Further, a configuration may be adopted in which lower-level data such as a digital value output from the A / D converter 34 is output to a subsequent device, and coordinate calculation and on / off state detection are performed by the subsequent device. . RS-232C, USB, or the like can be used as a transmission means to 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 surface 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. Further, in order to collect the cables connecting the coordinate input panel 11 and the analog signal processing unit 30, the coordinate input panel 11 is connected to the outside of the resistive surrounding electrode 13 on the coordinate input panel 11 from each of the detection electrodes 14 to 17. Even when a conductive pattern is formed up to an arbitrary position on the outer periphery, the external resistance components 26 to 29 increase depending on the conductive ink to be used, the thickness of the pattern, etc. The pattern is regarded as a part of the lead lines 22 to 25). 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 surface 18 is inside the region 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 surface 18 of the coordinate input panel 11 or when the finger 21 is above the coordinate input surface 18, the current flowing from the fingertip to the coordinate input panel 11 through the surface resistor 12. Among these, a value obtained by measuring the current flowing through the detection electrode 14 (vertex A) by the A / D converter 34 is measured value A, a value obtained by measuring the current flowing through the detection electrode 15 (vertex B) is measured value B, and the detection electrode 16 A value obtained by measuring the current flowing through (vertex C) is defined as a measured value C, and a value obtained by measuring the current flowing through the detection electrode 17 (vertex D) is defined as a measured value D. The CPU 35 does not touch anything in the coordinate input surface 18 of the coordinate input panel 11 and stores the current values flowing through the detection electrodes 14 to 17 in a state where there is nothing in the vicinity of the coordinate input surface 18 in the vertical direction. In addition, the measurement values A to D are calculated as increments from the state where the touch is not performed.
The CPU 35 sets a state where the coordinates cannot be detected as an initial state, continuously monitors the total value (A + B + C + D) of the current flowing through the detection electrodes 14 to 17, and the total value of the current is higher than a predetermined detection threshold value set in advance. When it becomes larger, it is determined that the state is changed from the state where the coordinates cannot be detected to the state where the coordinates can be detected. Further, in a state where the coordinates can be detected, if the total current value becomes smaller than a predetermined non-detection threshold, it is determined that the state where the coordinates can be detected has changed to a state where the coordinates cannot be detected.
However, regarding the determination that the total value of the current is larger than the detection threshold or smaller than the non-detection threshold, in order to prevent an erroneous determination due to mixing of noise or the like and excessive reaction to fine fluctuations, for example, It is desirable to perform a process for confirming that the same state has continued for a plurality of consecutive measurements, or to set a non-detection threshold value to a value slightly smaller than the detection threshold value to provide hysteresis.
At this time, the coordinates (X, Y) of the position indicated by the finger 21 are X = a × (−A + B + C−D) / (A + B + C + D), Y = b × (−A−B + C + D) / in the orthogonal coordinate system XY. It is known that it can be obtained by (A + B + C + D). 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 are distances from the origin to the boundary of the coordinate input surface 18 in the X direction and Y direction, respectively. When the resistance values of the external resistance components 26 to 29 cannot be ignored, the measured values A to D are corrected or the calculation results (X, Y) are corrected according to the resistance values.
The detection threshold is determined based on the total value of currents measured in a state where the finger 21 is lifted from the coordinate input surface 18 and is stationary in the coordinate input surface 18. At this time, there are individual differences in the thickness of the finger and the size of the human body following the finger, and the further away from the coordinate input surface 18, the smaller the total current value becomes, and the calculated coordinates are also accurate. In view of these conditions, it is preferable that the coordinates are set to a value desired to be detected. At this time, the surface of the coordinate input surface 18 in which the coordinates can be detected and the range above the vertical direction are set as the coordinate input region.
Next, detection of the on / off state will be described. The CPU 35 starts from the OFF state when the coordinates cannot be detected, and continuously monitors the total value (A + B + C + D) of the current flowing through the detection electrodes 14 to 17 so that the total current value is obtained. When the predetermined ON threshold value is exceeded, it is determined that the state has changed from the OFF state to the ON state. Further, when the total value of the current is smaller than a predetermined off threshold value in the on state, it is determined that the on state is changed to the off state.
The on threshold is set to be equal to or higher than the detection threshold.
However, similarly, regarding the determination that the total value of the current has become larger than the on threshold or smaller than the off threshold, the same state has continued for a plurality of consecutive measurements as in the detection threshold. It is desirable to perform processing for confirming the above, or to set the off threshold value to a value slightly smaller than the on threshold value to provide hysteresis.
The on-threshold value is the total value of the current measured in a state where a finger is brought into contact with the arbitrary position on the surface in the coordinate input area 18 and the finger is touched at an arbitrary position on the surface in the coordinate input area 18. It is determined based on the maximum value of the total current value when At this time, since there are individual differences in the thickness and surface state of the finger, the size of the human body that follows the finger, etc., in consideration of the conditions used, conditions related to the user, etc. It is preferable to match the finger with a small total value. Create a substitute for a finger using conductive rubber, etc., which has almost the same electrical characteristics as the finger, and place it in contact with the touch panel with a constant load of, for example, 0.1 N, and measure the total current. Then, the ON threshold value may be determined based on this.
Next, coordinate smoothing means will be described. Here, an infinite impulse response type digital low-pass filter is used as the first smoothing means, and a moving average is used as the second smoothing means.
The low-pass filter that is the first smoothing means uses a recurrence formula as shown in Formula 1 so that it can be applied immediately. Here, _Pi is the X coordinate or Y coordinate detected by the coordinate detection means, and _Ri is the result of applying a low-pass filter. The subscript i is an index that is incremented by 1 each time the coordinate smoothing means is executed. Here, the time point at which the coordinates can be detected is set as the starting point of the recurrence formula, and is initialized as i = 0 each time. Further, _{f s} is the sampling frequency, _{f c} is the cutoff frequency. Here, the sampling frequency is the reciprocal of the period on the program in which the coordinate smoothing means is executed, and the upper limit is determined by the configuration of the coordinate detection means and the performance of the CPU 35. The cut-off frequency is a numerical value that is determined based on the temporal fluctuation speed of fine fluctuations to be removed.

例えば、サンプリング周波数が１００Ｈｚであるとし、遮断周波数を１０Ｈｚとする。ＣＰＵ３５の性能を考慮して、演算を整数のみで行うこととし、座標を１６ビット整数の範囲で表現し、演算を３２ビットで行うこととすると、数式１は、Ｒ_ｉ＝（６７Ｐ_ｉ＋１３５Ｐ_ｉ−１＋６７Ｐ_ｉ−２＋１１４３Ｒ_ｉ−１−４１３Ｒ_ｉ−２）／１０００となる。
第２の平滑化手段である移動平均は、移動平均を適用した結果をＭ_ｉ、平均処理をする数をＮとして、Ｍ_ｉ＝（Ｒ_ｉ＋Ｒ_ｉ−１＋…＋Ｒ_{ｉ−Ｎ＋１}）／Ｎという式を用いる。Ｒ_ｉは、第１の平滑化手段を適用した結果である。添え字ｉは、第１の平滑化手段におけると同じく、座標平滑化手段が実行されるたびに１ずつ増分するインデックスである。やはり同様に、座標が検出できる状態になった時点を起点とし、そのたびにｉ＝０として初期化する。第２の平滑化手段としては、例えば、指数移動平均、修正移動平均といった平均処理を用いてもよい。
〈第２の実施の形態〉
図２は、第２の実施の形態になる座標入力システムの一例を示す構成図であり、入力パネルが発信側である場合である。第１の実施の形態と同じ内容については、説明を適宜省略する。入力ペン（座標指示器）６１が座標入力パネル５１の座標入力領域内で指示した位置（Ｘ，Ｙ座標）を検出する座標入力システムの構成図である。均一な面抵抗体５２の周囲又は内部に、各辺が直線である長方形の抵抗性周囲電極５３を密着配設し、抵抗性周囲電極５３の内部を長方形の座標入力面５８とする。ここでも第１の実施の形態と同様、面抵抗体５２の表面に絶縁処理をした場合を説明する。抵抗性周囲電極５３上の、平行四辺形の座標入力面５８の各頂点に当たる位置に駆動電極５４〜５７を形成し、そこにそれぞれ１本ずつ引き出し線６２〜６５を接続する。引き出し線６２〜６５は、それぞれ外部抵抗成分６６〜６９を含む。引き出し線６２〜６５を、駆動電極切り替えスイッチ７０に接続する。
抵抗性周囲電極５３は、座標計算を簡単にするために、各辺毎の両端で測った抵抗値を一定にする。
座標を検出するには、電位出力手段である信号発生器７１によって面抵抗体５２にＡＣ電位勾配を与える。電位勾配は、駆動電極切り替えスイッチ７０によって、平行四辺形の座標入力領域５８の対角を同時に接続する組み合わせで与えるようにする。即ち、次の４つの組み合わせが存在する。一つめ、駆動電極５４を信号発生器７１の出力側に接続し、駆動電極５６を接地側に接続し、駆動電極５５及び５７を非接続にする。二つめ、駆動電極５５及び５７を非接続のまま、駆動電極５４と５６の、信号発生器７１に対する出力側と接地側の接続を入れ替える。三つめ、駆動電極５５を信号発生器７１の出力側に接続し、駆動電極５７を接地側に接続し、駆動電極５４及び５６を非接続にする。四つめ、駆動電極５４及び５６を非接続のまま、駆動電極５５と５７の、信号発生器７１に対する出力側と接地側の接続を入れ替える。
これらのそれぞれの接続状態において、面抵抗体５２の、入力ペン６１の先端に近い位置のＡＣ信号レベルは、静電容量結合を介して入力ペン６１に伝達され、更にケーブル７２を通じてアナログ信号処理部７３に伝達される。アナログ信号処理部７３は、図示しないが、増幅器、帯域通過フィルタ、ＡＣ／ＤＣ変換器（ＡＭ検波器）等を含み、入力したＡＣ信号レベルに比例したＤＣ信号レベルを出力する。ＣＰＵ７５は、Ａ／Ｄコンバータ７４が出力するデジタル値を入力し、入力ペン６１の指示位置を計算する。
今、入力ペン６１の先端に近い位置の電位を測定した値のうち、駆動電極切り替えスイッチ７０によって駆動電極５４（頂点Ａ）が信号発生器７１の出力側に、駆動電極５６が接地側に接続され、駆動電極５５と５７が非接続のときの測定値を測定値Ａ、駆動電極５５（頂点Ｂ）が信号発生器７１の出力側に、駆動電極５７が接地側に接続され、駆動電極５４と５６が非接続のときの測定値を測定値Ｂ、駆動電極５６（頂点Ｃ）が信号発生器７１の出力側に、駆動電極５４が接地側に接続され、駆動電極５５と５７が非接続のときの測定値を測定値Ｃ、駆動電極５７（頂点Ｄ）が信号発生器７１の出力側に、駆動電極５５が接地側に接続され、駆動電極５４と５６が非接続のときの測定値を測定値Ｄとする。
このとき、入力ペン６１が指示する位置の座標（Ｘ，Ｙ）は、直交座標系ＸＹにおいて、Ｘ＝２ａ×（−Ａ＋Ｂ＋Ｃ−Ｄ）／（Ａ＋Ｂ＋Ｃ＋Ｄ）、Ｙ＝２ｂ×（−Ａ−Ｂ＋Ｃ＋Ｄ）／（Ａ＋Ｂ＋Ｃ＋Ｄ）によって求めることができることが知られている。ただし、直交座標系ＸＹは、座標入力面５８の中心を原点とし、Ｘ軸は検出電極５４から検出電極５５に向かう方向を正とし、Ｙ軸は検出電極５４から検出電極５７に向かう方向を正とする。ａ及びｂは、原点から、それぞれＸ方向及びＹ方向の座標入力面５８の境界までの距離を示す。外部抵抗成分６６〜６９の抵抗値を無視できない場合は、それらの抵抗値に応じて、測定値Ａ〜Ｄを補正するか、計算結果（Ｘ，Ｙ）を補正する。
ＣＰＵ７５は、第１の実施の形態と同じように、座標を検出できない状態を初期状態とし、測定値の合計値（Ａ＋Ｂ＋Ｃ＋Ｄ）を継続的に監視して、測定値の合計値が、予め定めた所定の検出閾値よりも大きくなった場合に、座標を検出できない状態から座標を検出できる状態に変化したと判別する。
検出閾値は、座標入力面５８内において、入力ペン６１を座標入力面５８から浮かせて静止させた状態で測定した測定値の合計値を基に、決定する。この際、座標入力面５８から離れれば離れるほど測定値の合計値は小さくなり、計算結果である座標も正確でなくなるため、これらの条件を鑑みて、座標を検出できる状態としたい数値に合わせるのが好ましい。このとき、座標を検出できる状態になることができる、座標入力面５８の表面、及びその鉛直方向上方の範囲内を、座標入力領域とする。
一方、オンオフ状態の検出については、入力ペン６１の先端にスイッチ（図示せず）を設け、入力ペンが座標入力面５８に当接して圧力がかかったら、スイッチが押し込まれるようにする。ＣＰＵ７５は、スイッチの状態を監視し、スイッチが押し込まれていない状態から押し込まれた状態に変化したら、オン状態に変化したと判別する。前記測定値の合計値（Ａ＋Ｂ＋Ｃ＋Ｄ）が検出閾値よりも小さい場合には、スイッチが押し込まれていると判断できる状況でも、入力ペン６１の先端が座標入力面５８に当接しておらず、別の原因で押し込まれていると判断し、オフ状態であると判別するようにしてもよい。もしくは、測定値の合計値に関して、検出閾値よりも大きな、別の閾値を設け、測定値の合計値がそれより小さい場合には、入力ペン６１の先端は座標入力領域内にあるものの、座標入力面５８に当接していないと判断し、オフ状態であると判別するようにしてもよい。
座標平滑化手段については、第１の平滑化手段として、無限インパルス応答型のデジタルローパスフィルタを用い、第２の平滑化手段として、移動平均を用いる点は、第１の実施の形態と同様である。
本実施の形態では、第１の平滑化手段及び第２の平滑化手段を、座標が検出できない状態から検出できる状態になった時に、式のインデックスｉ＝０として初期化するだけでなく、オンオフ状態がオフ状態からオン状態に変化した時にも、同じように初期化する。オン状態からオフ状態に変化した時には初期化しない。

For example, assume that the sampling frequency is 100 Hz and the cutoff frequency is 10 Hz. Considering the performance of the CPU 35, if the calculation is performed only with integers, the coordinates are expressed in the range of 16-bit integers, and the calculation is performed with 32 bits, Equation 1 can be expressed as R _i = (67P _i + 135P _{i -1} + 67P _i-2 + 1143R _i-1 413R _i-2 ) / 1000.
The moving average which is the second smoothing means is M _i = (R _i + R _i−1 +... + R _{i−N + 1} ) / N, where M _{i is} the result of applying the moving average, and N is the number of average processing. The following formula is used. R _i is the result of applying the first smoothing means. The subscript i is an index that is incremented by 1 each time the coordinate smoothing means is executed, as in the first smoothing means. Similarly, the time when the coordinates can be detected is set as a starting point, and is initialized as i = 0 each time. As the second smoothing means, for example, an averaging process such as an exponential moving average or a modified moving average may be used.
<Second Embodiment>
FIG. 2 is a configuration diagram illustrating an example of a coordinate input system according to the second embodiment, in which the input panel is a transmission side. The description of the same contents as in the first embodiment will be omitted as appropriate. 2 is a configuration diagram of a coordinate input system that detects a position (X, Y coordinates) designated by an input pen (coordinate indicator) 61 in a coordinate input area of a coordinate input panel 51. FIG. A rectangular resistive surrounding electrode 53 with each side being a straight line is disposed in close contact with or around the uniform surface resistor 52, and the inside of the resistive surrounding electrode 53 is defined as a rectangular coordinate input surface 58. Here, as in the first embodiment, the case where the surface of the sheet resistor 52 is insulated will be described. Drive electrodes 54 to 57 are formed on the resistive surrounding electrode 53 at positions corresponding to the apexes of the parallelogram coordinate input surface 58, and lead lines 62 to 65 are connected to the drive electrodes 54 to 65, respectively. The lead lines 62 to 65 include external resistance components 66 to 69, respectively. The lead lines 62 to 65 are connected to the drive electrode changeover switch 70.
The resistive surrounding electrode 53 makes the resistance value measured at both ends of each side constant in order to simplify the coordinate calculation.
In order to detect the coordinates, an AC potential gradient is applied to the surface resistor 52 by the signal generator 71 which is a potential output means. The potential gradient is given by a combination in which the diagonals of the parallelogram coordinate input area 58 are simultaneously connected by the drive electrode switch 70. That is, the following four combinations exist. First, the drive electrode 54 is connected to the output side of the signal generator 71, the drive electrode 56 is connected to the ground side, and the drive electrodes 55 and 57 are disconnected. Second, the connection of the output side and the ground side of the drive electrodes 54 and 56 with respect to the signal generator 71 is switched while the drive electrodes 55 and 57 are not connected. Third, the drive electrode 55 is connected to the output side of the signal generator 71, the drive electrode 57 is connected to the ground side, and the drive electrodes 54 and 56 are disconnected. Fourth, the connection between the output side and the ground side of the drive electrodes 55 and 57 with respect to the signal generator 71 is switched while the drive electrodes 54 and 56 are not connected.
In each of these connection states, the AC signal level of the surface resistor 52 at a position close to the tip of the input pen 61 is transmitted to the input pen 61 through the capacitive coupling, and further, the analog signal processing unit through the cable 72. 73. Although not shown, the analog signal processing unit 73 includes an amplifier, a band pass filter, an AC / DC converter (AM detector), and the like, and outputs a DC signal level proportional to the input AC signal level. The CPU 75 inputs the digital value output from the A / D converter 74 and calculates the indicated position of the input pen 61.
Of the values measured at the position near the tip of the input pen 61, the drive electrode 54 (vertex A) is connected to the output side of the signal generator 71 and the drive electrode 56 is connected to the ground side by the drive electrode changeover switch 70. The measured value when the drive electrodes 55 and 57 are not connected is the measured value A, the drive electrode 55 (vertex B) is connected to the output side of the signal generator 71, the drive electrode 57 is connected to the ground side, and the drive electrode 54 Measured value B when the first and second electrodes 56 are disconnected, the measured value B, the drive electrode 56 (vertex C) is connected to the output side of the signal generator 71, the drive electrode 54 is connected to the ground side, and the drive electrodes 55 and 57 are disconnected Measured value when Measured value C, Measured value when drive electrode 57 (vertex D) is connected to the output side of signal generator 71, drive electrode 55 is connected to the ground side, and drive electrodes 54 and 56 are disconnected. Is a measured value D.
At this time, the coordinates (X, Y) of the position indicated by the input pen 61 are X = 2a × (−A + B + C−D) / (A + B + C + D), Y = 2b × (−A−B + C + D) in the orthogonal coordinate system XY. It is known that it can be obtained by / (A + B + C + D). However, in the orthogonal coordinate system XY, the center of the coordinate input surface 58 is the origin, the X axis is positive in the direction from the detection electrode 54 to the detection electrode 55, and the Y axis is positive in the direction from the detection electrode 54 to the detection electrode 57. And a and b indicate distances from the origin to the boundary of the coordinate input surface 58 in the X direction and the Y direction, respectively. When the resistance values of the external resistance components 66 to 69 cannot be ignored, the measured values A to D are corrected or the calculation results (X, Y) are corrected according to the resistance values.
As in the first embodiment, the CPU 75 sets a state in which coordinates cannot be detected as an initial state, continuously monitors the total value of measurement values (A + B + C + D), and the total value of measurement values is determined in advance. When it becomes larger than a predetermined detection threshold value, it is determined that the state has changed from a state where coordinates cannot be detected to a state where coordinates can be detected.
The detection threshold is determined based on the total value of the measurement values measured in a state where the input pen 61 is floated from the coordinate input surface 58 and is stationary in the coordinate input surface 58. At this time, the further away from the coordinate input surface 58, the smaller the total value of the measured values, and the calculated coordinates become inaccurate. Therefore, in consideration of these conditions, the coordinate value is set to a value desired to be detected. Is preferred. At this time, the surface of the coordinate input surface 58 in which the coordinates can be detected and the upper range in the vertical direction are set as the coordinate input area.
On the other hand, for the detection of the on / off state, a switch (not shown) is provided at the tip of the input pen 61 so that the switch is pushed in when the input pen contacts the coordinate input surface 58 and pressure is applied. The CPU 75 monitors the state of the switch, and determines that it has changed to the ON state when the switch is changed from the state where the switch is not pushed in to the pushed state. When the total value (A + B + C + D) of the measured values is smaller than the detection threshold value, the tip of the input pen 61 is not in contact with the coordinate input surface 58 even in a situation where it can be determined that the switch is pressed. It may be determined that it is pushed in due to a cause, and it may be determined that it is in an off state. Alternatively, regarding the total value of the measurement values, another threshold value that is larger than the detection threshold value is provided, and when the total value of the measurement values is smaller than that, the tip of the input pen 61 is within the coordinate input area, but the coordinate input It may be determined that it is not in contact with the surface 58 and determined to be in the off state.
As for the coordinate smoothing means, an infinite impulse response type digital low pass filter is used as the first smoothing means, and a moving average is used as the second smoothing means, as in the first embodiment. is there.
In the present embodiment, when the first smoothing means and the second smoothing means are in a state where they can be detected from a state where coordinates cannot be detected, they are not only initialized as an index i = 0 but also turned on / off. When the state changes from the off state to the on state, initialization is performed in the same manner. It is not initialized when it changes from the on state to the off state.

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
Example 1 corresponds to the first embodiment, and uses the coordinate input panel 11 as a receiving side.
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 order to compare the results with other methods, the coordinate smoothing means is not mounted on the CPU 35, and coordinate data that is not smoothed is transmitted to the subsequent stage. Coordinate data was taken into a personal computer via serial communication, and coordinate smoothing means was applied to the coordinate data converted and stored in millimeters on the personal computer.
A digital low-pass filter was used as the first smoothing means. The sampling frequency was about 100 Hz. The cutoff frequency was 10 Hz, and R _i = (67P _i + 135P _i-1 + 67P _i-2 + 1143R _i-1 -413R _i-2 ) / 1000 was used. As the second smoothing means, a moving average was used, and N = 4, and a formula M _i = (R _i + R _i-1 +... + R _i-3 ) / 4 was used.
As coordinate data, coordinate data when a circle was drawn at a relatively high speed and coordinate data when a straight line was drawn at a relatively low speed were collected.
(Comparative Example 1)
As a comparative example, a moving average (N = 4), moving average (N = 10), or digital low-pass filter (same as in the first embodiment) is applied to the same coordinate data as in the first embodiment as a coordinate smoothing unit. did.
The collected coordinate data, the result of applying the coordinate smoothing means of Comparative Example 1, and the result of applying the coordinate smoothing means of Example 1 are shown in FIG. FIG. 4 shows a case where a straight line-like locus is drawn at a low speed. The drawing direction is indicated by an arrow in “(a) Original coordinates” in FIGS. In FIG. 3 showing a case where a locus on an arc is drawn at high speed, the original coordinate data is drawn with a broken line in the result of applying the coordinate smoothing means. In FIG. 4 showing a case where a straight line-like locus is drawn at a low speed, the ratio of the vertical and horizontal scales is changed in order to emphasize the fluctuation in the direction orthogonal to the straight line.
As a result, the coordinate smoothing means shown in Comparative Example 1 is suitable for either the case where the movement of the finger is low speed or high speed, but is not effective for both. It has been confirmed that the smoothing means can perform smoothing in the same manner regardless of whether the finger moves at a low speed or at a high speed.

(Example 2)
Example 2 corresponds to the second embodiment, and uses the coordinate input panel 51 as a transmission side.
The coordinate input panel 51 is manufactured in the same manner as in the first embodiment, but the width of the resistive surrounding electrode 53 is about 68Ω between the resistance AB and the resistance BC of the resistive surrounding electrode 53. The resistance values measured at both ends of each side of the resistive surrounding electrode 53 were made substantially equal.
A digital low-pass filter was used as the first smoothing means. The sampling frequency was about 100 Hz. The cutoff frequency was 10 Hz, and R _i = (67P _i + 135P _i-1 + 67P _i-2 + 1143R _i-1 -413R _i-2 ) / 1000 was used. As the second smoothing means, a moving average was used, and N = 4, and a formula M _i = (R _i + R _i-1 +... + R _i-3 ) / 4 was used. When both the first smoothing means and the second smoothing means are in a state where the coordinates cannot be detected, the first smoothing means and the second smoothing means are not only initialized as the index i = 0 of the expression, but also the on / off state of the input pen 61 is changed. The same initialization was done when the off state changed to the on state.
The coordinate smoothing means was mounted on the CPU 35, and coordinate data to which smoothing was applied was taken into a personal computer via serial communication.
FIG. 5 shows the result when three horizontal lines are drawn in order from the top while the input pen 61 is kept in the coordinate input area. The input pen 61 was brought into contact with the coordinate input surface 58 to draw a horizontal line from left to right, and the pen tip of the input pen 61 was slightly lifted and moved to the lower left. In FIG. 5, data in which the on / off state of the input pen 61 is on is drawn by a solid line, and data in which the input pen 61 is off is drawn by a broken line. The reason why the right end of each horizontal line is in the off state is that the input pen 61 floats while moving to the right.
As a result, it was confirmed that the coordinate input system has coordinate smoothing means effective even when the trajectory changes particularly rapidly at the time of initial writing.

DESCRIPTION OF SYMBOLS 1 Coordinate input panel 2 Surface resistor 3 Resistive surrounding electrode 4, 5, 6, 7 Detection electrode 8 Coordinate input surface 11 Coordinate input panel 12 Surface resistor 13 Resistive surrounding electrode 14, 15, 16, 17 Detection electrode 18 Coordinate Input surface 21 Fingers 22, 23, 24, 25 Lead lines 26, 27, 28, 29 External resistance component 30 Analog signal processing unit 31 Vibration voltage application circuit 32 Vibration voltage generator 33 Analog multiplexer 34 A / D converter 35 CPU
51 Coordinate input panel 52 Surface resistor 53 Resistive surrounding electrodes 54, 55, 56, 57 Drive electrode 58 Coordinate input surface 61 Input pens 62, 63, 64, 65 Lead lines 66, 67, 68, 69 External resistance component 70 Drive Electrode changeover switch 71 Signal generator 72 Cable 73 Analog signal processor 74 A / D converter 75 CPU

Claims (5)

Coordinate detection means for detecting the coordinates of the coordinate instruction means and the on / off state of the coordinate instruction means in a coordinate input area comprising a two-dimensional planar coordinate input surface and a space on the coordinate input surface. A coordinate smoothing means for smoothing the coordinates, and a transmission means for transmitting the smoothed coordinates and the on / off state to the outside. The coordinate smoothing means includes a first smoothing means and a second smoothing means. And the first and second smoothing means are initialized at a time when the coordinates input area is detected from a state in which the coordinates of the coordinate indicating means cannot be detected. While the coordinates can be detected, the coordinate input system is characterized in that the first smoothing means and then the second smoothing means are applied to the coordinates of the coordinate designating means. 2. The coordinate input system according to claim 1, wherein the first smoothing means is a low-pass filter, and the second smoothing means is a moving average. The coordinate instruction means is an input pen having a switch at a pen tip, and the on / off state is a state in which the pen tip of the input pen is in contact with the coordinate input surface, and a state in which the pen tip is not in contact is turned off. The coordinate input system according to claim 1. The coordinate instruction means is a user's finger, and the on / off state is on when the user's finger is in contact with the coordinate input surface, and off when the user's finger is not in contact. Coordinate input system described. 5. The coordinate input system according to claim 1, wherein the first and second smoothing means are initialized when an on / off state of the coordinate indicating means changes from off to on.

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