JPH05250086A - Coordinate input device of resistance film system and its production - Google Patents

Abstract

PURPOSE:To provide a highly precise coordinate input device and its manufacture by suppressing the error of linearity below a prescribed value independently of the error during an manufacturing process such as the error of the thickness of a resistance film, etc. CONSTITUTION:The coordinate input device which outputs a voltage value or a current value corresponding to the coordinate of a desired point on the basis of conduction at the above- mentioned desired point of two sheets of the resistance films 1, 2 with the intermediary of a spacer 3 and a storage means which stores beforehand data for correcting the coordinate including the variance of the resistance of the resistance film are provided. An analog switch circuit 21 to switch each connection of the constant current source 25 of a measuring arithmetic part 20, an amplifier circuit 22, and each X and Y resistance film of an input panel 10 are provided. As for the manufacture, a resistance film producing process, a preliminary measuring process of the voltage value/current value before working, an input panel producing process to insert the spacer between two sheets of the resistance films and stick them together are provided, and further, a measure vague working process to make the coordinate and the voltage value/current value of a preliminarily measured definite point correspond to a coordinate correcting method, and a coordinate correction data storing process to store a worked value are provided.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coordinate input device for inputting coordinates with high accuracy by a resistance film method and a manufacturing method thereof.

2. Description of the Related Art A resistance film type coordinate input device includes a plane input section generally called an input panel and a measurement calculation section for measuring a detection signal of the input panel and performing a predetermined calculation on the detected signal to calculate a coordinate value. Composed. The input panel is composed of two opposing resistance films and an isolation layer called a spacer that insulates them. The resistance film is usually a polymer film
A thin film of ITO (indium tin oxide) is formed on the surface of the base so as to have a constant surface resistivity. In the case of the X plane, low resistance terminal electrodes are provided on the edges at both ends in the horizontal direction, and lead wires for connection to the measurement calculation unit are connected. Similarly, the Y plane also has terminal electrodes on the edges at both ends in the vertical direction, and is connected to the measurement calculation unit. As the spacer, a so-called dot spacer has been widely used for a long time, but this is one in which small protrusions of an insulating resin are planted on one resistance film surface at a constant density. With this spacer, when there is no input operation on the input plane, the two resistive films are not in contact and are electrically insulated, but when the input plane is pressed with a fingertip or a pen-shaped object, the film base on the surface bends. , The two resistance films facing each other come into contact with each other at the input point and become electrically conductive. At this time, if a constant voltage or constant current is applied to the X plane, a voltage proportional to the position of the input point on the X plane is transmitted to the Y plane and can be taken out to the measurement circuit through the terminal electrode. Next, by changing the connection and applying a constant voltage or constant current to the Y plane, a voltage proportional to the input point position on the Y plane can be taken out from the terminal electrode on the X plane to the measuring circuit. The respective detected voltages on the X plane and the Y plane are converted into coordinate values by a constant arithmetic processing and output to the outside. The dot spacer is not a problem when performing point input as described above, but is extremely unsuitable when performing line input with an input pen such as handwritten character input. Therefore, various attempts have been made to develop spacers that do not use physical protrusions such as dots, that is, dotless spacers. Also, the measurement calculation unit is configured to switch the connection lines from the resistance films on the X plane and the Y plane to a constant voltage source or a constant current source and an input system circuit, an analog switch circuit, an amplifier circuit, an A / D conversion circuit, It is composed of a micro controller including a CPU, ROM, RAM and the like. The main processing up to the coordinate value conversion is usually performed by control and arithmetic processing by the micro controller.

By the way, in the resistance film type coordinate input device, it is basically assumed that the surface resistivity of the resistance film is constant in every place in the input plane. Therefore, if the surface resistivity differs depending on the location, the output coordinate value will include an error by that amount. Although this error is called a linearity error, in the above measurement example, the detected voltage is not accurately proportional to the input position, and is measured as a value including the linearity error. The linearity error of a commercially available mass-produced ITO film is usually about 0.6%, but it is very unlikely that this value will be significantly improved due to the technical limit of ITO film thickness control in the resistance film manufacturing process. .. On the other hand, in a highly detailed input application such as handwritten character input, the linearity error as an input device is required to be 0.1% or less. The resistive film method has a great advantage as a low-cost input device because of its simple structure in principle, but it has a drawback that it cannot support high-precision input due to the limit of linearity accuracy of the resistive film. The present invention eliminates the above-mentioned conventional defects, suppresses the linearity error to a predetermined value or less regardless of the product error in the manufacturing process such as the film thickness error of the resistance film,
A resistance film type coordinate input device that realizes highly accurate coordinate input and a method for manufacturing the same.

In order to solve this problem, the resistance film type coordinate input device of the present invention is based on the conduction at a desired point between two resistance films via a spacer. A coordinate input means for outputting a voltage value or a current value corresponding to the coordinates of a point, a storage means for previously storing data for coordinate correction including a variation in resistance of the resistance film, and an input value from the coordinate input means. Correspondingly, there is provided coordinate calculation means for calculating corrected coordinates based on the data stored in the storage means. Here, the coordinate calculation means uses the correction data stored in the storage means to correct the coordinates by a two-dimensional interpolation method or a least squares plane method.
Further, the manufacturing method of the resistance film type coordinate input device of the present invention,
A method of manufacturing a resistance film type coordinate input device, which inputs coordinates based on conduction at a desired point between two resistance films via a spacer, comprising: a resistance film forming step of forming a resistance film; Preliminary measurement step of preliminarily measuring the voltage value or current value at a predetermined fixed point on the resistance film of the above, and an input panel preparation for forming an input panel by inserting a spacer between the two preliminarily measured resistance films And a process. Further, a measured value processing step of processing the coordinates of the fixed point and the voltage value or the current value which are preliminarily measured according to the coordinate correction method, and correction data for storing the processed value as data for coordinate correction. And a storage step. Here, in the preliminary measurement step, a plurality of probes (probes) are simultaneously brought into contact with a predetermined fixed point on the surface of the resistance film to be measured, and the probe selection electronic circuit switches at high speed to enhance the measurement efficiency. The present invention is provided with a storage means for pre-storing data for coordinate correction including resistance variation of the resistance film, and a preliminary measurement for previously measuring a voltage value or a current value at a predetermined fixed point on the resistance film before processing. By providing a process,
Highly accurate coordinate input is realized by suppressing the linearity error to a predetermined value or less regardless of the product error in the manufacturing process such as the film thickness error of the resistance film.

【Example】

<Structure of Coordinate Input Device> FIG. 1 is a block diagram showing the structure of the main part of the coordinate input device of this embodiment.
0 and the connection between the measurement calculation unit 20 and the measurement calculation unit 2
0 configuration is shown. FIG. 2 shows a structural example of the resistance film type input panel 10. The input panel 10 is composed of an X-plane resistance film 1, a Y-plane resistance film 2, and a spacer 3 separating these resistance films. Terminal electrodes 1a and 1b for external connection are printed on both edges of the X plane, and terminal electrodes 2a and 2b are similarly printed on both edges of the Y plane. The spacer 3 may be a dot spacer or a dotless spacer, but the dotless is preferable for line input such as handwriting input.
The resistance films 1 and 2 are attached to each other with the spacer 3 interposed therebetween, and assembled into one input panel 10. still,
Reference numeral 4 in FIG. 1 is an input pen. Measurement calculation unit 20
The analog switch circuit 21 switches the connection between the X and Y resistance films of the input panel 10 and the constant current source 25 and the amplification circuit 22 of the measurement calculation unit 20, and the control is performed by the micro controller 24. Output.
The A / D conversion circuit 23 is a circuit for converting the measured voltage value into a digital numerical value, which is also controlled by the output signal of the micro controller 24. Micro controller 2
Reference numeral 4 is composed of a CPU, a ROM, a RAM, etc., and outputs the control signal, performs predetermined calculation on the digitally converted measured value, and outputs the coordinate value (X, Y) of the input position to the outside. Is programmed. The micro-controller 24 is a coordinate correction means 24a for calculating coordinates with a predetermined correction based on the measured digital numerical value, and a reference for storing "reference data" for the coordinate correction corresponding to the measured digital numerical value. It has a coordinate correction table 24b such as an up table. Where "reference data"
Is subjected to appropriate editing processing corresponding to the correction method of the coordinate correction means 24a to the data obtained in the preliminary fixed point measurement step of the device manufacturing process described later, and then the memory (coordinate correction) of the micro controller 24. Pre-stored in table 24b). If the data obtained in the fixed point measurement process is called “fixed point data”, the “fixed point data” and the “reference data” do not necessarily match in content and form. The reason is that when the microcontroller 24 refers to the reference data, it is usual to use the table lookup method, but in order to perform this operation efficiently, it is necessary to devise the form of the data array. thing,
There are two types of correction calculation methods, but the content of the reference data is completely different depending on the method. Appropriate editing / processing refers to this conversion process. <Example of Coordinate Correction Method ... Two-Dimensional Interpolation Method> FIG. 3 is a schematic diagram for explaining a two-dimensional interpolation method which is an example of a correction calculation method by the coordinate correction unit 24a. Points P1 to P4 indicate fixed points that have been actually measured, and the coordinates and measured values are known. A point P indicates a point at which position input is performed, and the measured value is known but the coordinate is unknown. Also, p and q are in the X direction,
The fixed point pitch in the Y direction is shown. The known data and unknown coordinates are summarized as follows. The unknowns are the coordinate values X and Y
And all other values are known. Point X plane measurement value Y plane measurement value Coordinate value P1 Vi, j Wi, j (Xi, Yj) P2 Vi, j + 1 Wi, j + 1 (Xi, Yj + 1) P3 Vi + 1, j Wi + 1 , j (Xi + 1, Yj) P4 Vi + 1, j + 1 Wi + 1, j + 1 (Xi + 1, Yj + 1) P V W (X, Y) Now, the unknown coordinates X of the point P, For example, the X coordinate of Y will be obtained. The calculation of the Y coordinate can be performed by a completely similar method.

[Equation 1] Equation (1) calculates the estimated value X1 of the unknown coordinate X with reference to the fixed points P1 and P3 in FIG. Equation (2) calculates the estimated value X2 of the unknown coordinate X with reference to the fixed points P2 and P4 in FIG. Equation (3) is an interpolation according to the position in the Y-axis direction from the two estimated values X1 and X2,
X is calculated as the final estimated value. The equations (1) and (2) are ordinary interpolation calculations, but the equation (3) is a calculation method for expanding this to two-dimensional coordinates. Fixed point pitch p, q
Should be optimally set from the state of the linear error distribution of the resistance film and a given error tolerance, and various methods have been devised. When the fixed points are optimally arranged, generally p,
Although q does not become a constant value, p and q may be practically made constant depending on the characteristics of the resistance film. In the case of this method, the coordinates of the fixed points P1 to P4 and the measured values are "reference data" stored in the coordinate correction table 24b. The coordinate correction means 24a reads the coordinates and the measured values from the coordinate correction table 24b based on the measured values V and W of the input point P and performs the above calculation, or k1, k2, l1 and l.
2 may be read and calculated, or X and Y may be read directly if the memory capacity is not limited. <Other Example of Coordinate Correction Method ... Least Square Plane Method> FIG. 4 is a schematic diagram of a least square plane method which is another example of the correction calculation method. 4 (1) is a section P1 P2 P3 with the input panel surface
Indicates P4. The X coordinates of the boundary are Xi and Xi + 1, respectively.
, Y coordinates are Yj and Yj + 1, respectively. Figure 2 (2)
Shows the AA ′ cross section of (1) in FIG. Reference numeral 41 in the drawing denotes a cross section of the error distribution curved surface on the X plane or Y plane, and 42 denotes a cross section of the least squares plane obtained as a result of the later-described calculation. Line O
O'indicates a cross section of the reference plane with zero error. Similarly,
(3) of FIG. 4 shows a BB 'cross section, and 41', 42 '
Indicates the cross section of the error curved surface and the cross section of the least squares plane, respectively. Now, it is assumed that an appropriate number of uniformly distributed points are measured from within the section of FIG. The measured value Vx on the X plane is approximated by a linear combination of the coordinates (X, Y) of the point. Similarly, the measured value Vy on the Y plane also has coordinates (X,
Y) is approximated by a linear combination. That is,

[Equation 2] Measured value Vx (Xi, Yj) of each measured point (Xi, Yj)
), Vy (Xi, Yj) by the method of least squares. If the sections P1 P2 P3 P4 are common to the X plane and the Y plane, equations (4) and (5) can be solved for X and Y as simultaneous equations. That is,

[Equation 3] If the constants of the formulas (4) and (5) are prepared for each section, the coordinates X and Y should be calculated from the measured values Vx and Vy of the unknown point according to the formulas (6) and (7). You can
The constant prepared for each of these sections becomes the "reference data" of the coordinate correction table 24b in this method. The coordinate correcting means 24a first finds in which section the input point is located from Vx and Vy, and then calculates coordinates based on a constant measured and stored in advance. The size of the section and the density of the measurement points are determined by the error distribution characteristic of the resistance film and the allowable error value. Also in this method, if the memory capacity permits, the coordinates (X, Y) may be directly stored in the coordinate correction table 24b by using Vx and Vy as addresses. <Method of Creating Reference Data> FIG. 5 shows a manufacturing process of the input panel. First, the ITO film is cut in step S1 to form the resistance films 1 and 2. Next, in step S2, the terminal electrodes 1 are attached to both ends of the ITO film.
Print a, 1b, 2a, 2b. In step S3, a current value or a voltage value at a predetermined fixed point is measured on the resistance films 1 and 2 on which the terminal electrodes are printed, and data stored in the coordinate correction table 24b is created. In step S4, the spacers in the case of dot spacers are processed (in the case of dotless, this step is omitted). In step S5, the resistance films 1 and 2 are bonded via the spacers 3. In step S6, the product error standard is inspected, and in step S7, packaging is performed. In this case, the "fixed point data" measured in step S3 is unchanged, or if the correction method by the micro controller 24 is known, it is processed and attached to "reference data". In the process of FIG. 5, the case where the input panel is manufactured as an individual product has been described, but when the coordinate input device is manufactured integrally,
"Reference data" in the memory of the microcontroller 24
Is stored. The spacer processing step of step S4 is a step in which some processing is performed on the resistance film surface of the X plane or the Y plane, as in the case of a dot spacer, for example. If some processing is performed on the surface of the resistance film, it may be difficult to apply the measurement probe (probe) to an arbitrary place on the resistance film. Therefore, the "fixed point measuring step" of step S3 is the "spacer processing step" of step S4.
Need to be placed in front of. The advantages of inserting a preliminary “fixed point measurement step” will be described in more detail. (B) Input of multiple points is not allowed in principle when assembled as an input panel.
Input and measurement must be repeated point by point. This requires a lot of time and is not suitable for mass production. (B) When the X plane and the Y plane can be measured independently, a predetermined constant voltage or constant current can be applied between the terminal electrodes to bring a large number of probes into contact at the same time. However, high impedance is required between the probes. (C) Since many probes have membrane surface potentials at their respective positions, all probes are measured with a cycle of only the response time of the measuring instrument by sequentially switching the voltage measuring instrument connection by the analog selection circuit. can do. The more specific contents of the "fixed point measuring step" are as follows. The probe groups, which are two-dimensionally arranged at regular intervals, are accurately positioned in the planned input plane of the resistance film to be measured, and the probes are brought into contact with the resistance film surface at a constant pressure. Therefore, the coordinate value of each probe is known. A predetermined constant voltage or constant current is applied to the resistance film. Select the probe group in a predetermined order and connect it to the measuring instrument,
The voltage value of the probe is measured and recorded along with the coordinate value of the probe. After the measurement of all the probes is completed, the quality of the resistance film is inspected by the recorded "fixed point data", and if the product is defective, it is discarded together with the data. If it is a non-defective product, the serial number of the input panel is added to the data and the data is filed. In order to efficiently perform the “fixed point measurement process”, a dedicated measurement jig (or measurement robot) made for that purpose is prepared. Although the manufacturing process described in the preceding paragraph is an example in which measurement efficiency is emphasized, it may not be necessary to introduce an expensive measuring jig (or measuring robot) in the case of medium-to-small volume production. In such a case, it is sufficient to perform fixed point measurement in the product inspection step of step S6 in FIG. 5 without needing to separately provide an independent “fixed point measurement step”. In this case, since the input panel has already been assembled, the fixed point measurement will be performed one by one, and the measurement time will increase to some extent, but the measurement jig is a relatively simple device. Further, in the case where only the plane input section (input panel) is an independent product, this method can perform fixed point measurement again without necessarily depending on the manufacturing process of the manufacturer. <Correction Result According to this Embodiment> FIG. 6 is a diagram showing three-dimensionally the linear error in the non-correction of the X-plane resistance film of the plane input section. Maximum error 1.633 mm, average error 0.65
It is 7 mm. FIG. 7 is a simulation result obtained by performing a correction calculation by the "two-dimensional interpolation method" using a part of the error data as "reference data". According to this result, the maximum error is 0.33 mm and the average error is 0.034 mm, which is 5 times the maximum error and 19 times the average error compared to the uncorrected FIG. There is. Similarly, FIG. 8 is a simulation result of the correction calculation by the “least squares plane method”. In this result, the maximum error is 0.41
mm, the average error is 0.018 mm, which is 4 times the maximum error and 37 times the average error compared to the uncorrected FIG. The maximum error in FIGS. 7 and 8 is a protrusion-like apex that seems to be noise during measurement, but if this is excluded and compared, the maximum error in FIG. 7 is 0.08 mm or less ( That is, the accuracy is improved by 20 times), and the maximum error in FIG. 8 is 0.09 mm or less (that is, 18 times). In any case, the accuracy can be improved more than ten times with the maximum error. As described above, in the present embodiment, (1) a new process of “fixed point measurement process” is provided at a certain stage of the manufacturing process of the resistance film type input panel, and the respective resistance films of the X plane and the Y plane are provided. Measure individually and record "fixed point data" of a certain density. This data is recorded as data unique to the input device in association with the serial number of the solid. (2) The “fixed point data” in the previous section or data processed as necessary is stored in a part of the memory in the measurement calculation unit as “reference data” of the micro controller. The program of the micro controller performs a correction operation from the "reference data" and the measured values of the X plane and the Y plane obtained from the position input to convert the coordinate values into the coordinate values, and outputs the coordinate values. (3) There are two-dimensional interpolation method and least-squares plane method as the correction calculation method. (4) It is possible to improve the linearity error of the output coordinate value to 0.1% or less by the above "reference data" and the predetermined correction calculation. In the present embodiment, the two-dimensional interpolation method and the least squares plane method have been described as the correction calculation method, but this is an example of the correction calculation and may be another calculation method.

According to the present invention, the resistance film type coordinate input for realizing highly accurate coordinate input by suppressing the linearity error to a predetermined value or less regardless of the product error in the manufacturing process such as the resistance film thickness error. A device and a manufacturing method thereof can be provided. That is, in the resistance film type coordinate input device, a “fixed point measurement process” added during the manufacturing process of the plane input unit (input panel)
From the above, the "fixed point data" of the X and Y resistance films are obtained, and the "reference data" that is edited and processed as necessary for this are stored in the memory of the micro controller of the measurement calculation unit, and in the calculation processing of the micro controller By performing the "two-dimensional interpolation method" or "least squares plane method" or a correction calculation based on these methods, the accuracy is greatly improved compared to the conventional case where the coordinate value is directly obtained from the measured value of the plane input section output. It can be performed.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of a coordinate input device of this embodiment.

FIG. 2 is a diagram showing a configuration of an input panel of the coordinate input device according to the present embodiment.

FIG. 3 is a diagram showing an example of a coordinate correction method of the coordinate input device according to the present embodiment.

FIG. 4 is a diagram showing another example of the coordinate correction method of the coordinate input device according to the present embodiment.

FIG. 5 is a diagram showing a manufacturing process of the input panel of the present embodiment.

FIG. 6 is a diagram showing a linear error of an uncorrected resistance film.

FIG. 7 is a diagram showing a linear error by the coordinate correction method of FIG.

FIG. 8 is a diagram showing a linear error by the coordinate correction method of FIG.

[Explanation of symbols]

1 ... X plane resistance film, 1a, 1b ... X plane terminal electrodes,
2 ... Y plane resistance film, 1a, 1b ... X plane terminal electrode,
2a, 2b ... Terminal electrodes on Y plane, 3 ... Spacer, 4 ... Input pen, 10 ... Input panel, 20 ... Measurement / calculation unit, 21
... Analog switch circuit, 22 ... Amplifier circuit, 23 ... A
/ D conversion circuit, 24 ... Micro controller, 23 ...
A / D conversion circuit, 24a ... Coordinate correction means, 24b ... Coordinate correction table, 25 ... Constant current source

Claims (5)

[Claims] 1. A coordinate input means for outputting a voltage value or a current value corresponding to coordinates of the point based on conduction at a desired point between two resistance films via a spacer, and a resistance of the resistance film. Storage means for storing in advance data for coordinate correction including the variation, and coordinate calculation means for calculating corrected coordinates based on the data stored in the storage means, corresponding to the input value from the coordinate input means. And a resistance film type coordinate input device. 2. The coordinate calculation means uses the correction data stored in the storage means to correct the coordinates by a two-dimensional interpolation method or a least squares plane method. Resistance film type coordinate input device. 3. A method of manufacturing a resistance film type coordinate input device for inputting coordinates based on conduction at a desired point between two resistance films via a spacer, the method comprising forming a resistance film. Steps, a preliminary measurement step of previously measuring a voltage value or a current value at a predetermined fixed point on the resistance film before processing, a spacer is inserted between the two preliminarily measured resistance films, and the two are adhered to each other, and an input panel is attached. A method of manufacturing a resistance film type coordinate input device, comprising: a step of creating an input panel. 4. A measurement value processing step of processing the coordinates of the preliminarily measured fixed point and a voltage value or a current value according to a coordinate correction method, and storing the processed value as data for coordinate correction. 4. The method of manufacturing a resistance film type coordinate input device according to claim 3, further comprising a correction data storing step. 5. In the preliminary measurement step, a plurality of probes (probes) are simultaneously brought into contact with a predetermined fixed point on the resistance film surface to be measured, and the probe selection electronic circuit switches at high speed to improve measurement efficiency. 4. The method of manufacturing a resistive film type coordinate input device according to claim 3.