JPH1083251A - Coordinate detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correct an error between input position coordinates and detected position coordinates and to detect correct input position coordinates with respect to a coordinate detecting device such as an input touch panel. SOLUTION: This coordinate detecting device consists of a resistance film 2 which has a surface resistance value on a rectangular plane and feed terminals A to D which come into contact with the four corners of the resistance film 2 respectively, and produces crossing electric fields by applying different potentials between the feed terminals A to D at different time to detect pen input position coordinates. In this case, center potential measurement terminals E to H are provided in the centers between the feed terminals A to D and an error correction arithmetic part 12 is connected to a detecting circuit part 11 connected to the center potential measurement terminals E to H and the feed terminals A to D and relates the detected position coordinates detected by the detecting circuit part 11 to the actual pen input position coordinates with a parabolic function or an approximate function of the parabolic function to correct the error of the detected position coordinates.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a coordinate detecting device such as an input touch panel. For example, coordinate detection devices such as an input touch panel, a digitizer, and a tablet used as an information input device to a computer or the like have a difference between an actual input position coordinate and a detected position coordinate, and it is desired to reduce a detection error as much as possible. Have been.

[0002]

2. Description of the Related Art FIG. 9 is a schematic structural view of an electric tablet (coordinate detecting device) disclosed in Japanese Patent Application Laid-Open No. 47-36923. This is because a square planar resistance film 21 having a sheet resistance of 10 KΩ / □ and a resistance value 10Ω / considerably lower than the sheet resistance of the resistance film 21 on four sides around the resistance film 21.
A frame-shaped peripheral electrode 22 having a square, power supply terminals 23 provided at four corners of the peripheral electrode 22, and power supply terminals 23 at both ends of the opposite side.
The drive circuit unit 24 includes a drive circuit unit 24 that applies a predetermined potential therebetween, and a detection circuit unit 25 that detects a potential at an input position pressed by the input pen 7 made of a conductor. Thus, different electric potentials are applied at different times between the power supply terminals 23 at both ends of the opposite side to generate orthogonal electric fields, and the detection circuit unit 25 detects the X and Y position coordinate values from the electric potential of the pen input position, and Output to

[0003]

In this prior art, the sheet resistance of the central resistance surface surrounded by the peripheral electrodes is set to a sufficiently large value with respect to the sheet resistance of the peripheral electrodes.
Although the detection error is reduced by setting it to 0, it is difficult to obtain a resistive film having a high sheet resistance with a uniform resistance distribution. On the other hand, if the resistance of the surrounding electrodes is set to such a low value, In addition, there is a problem in that the current flowing through the surrounding electrodes becomes too large, resulting in a device with large power consumption.

For this reason, in the above-mentioned known example, the sheet resistance of the resistive film surrounded by the surrounding electrodes is set to 1000 times the sheet resistance of the surrounding electrodes.
As a technique that can reduce the detection error without doubling the size, as shown in FIG. 10, it is disclosed that a peripheral electrode 27 having a parabolic shape is formed to reduce the error predicted in advance. However, this has a problem that the pen input area is limited to a narrower area near the center of the resistive film.

[0005] In view of the above problems, an object of the present invention is to provide a coordinate detecting device capable of correcting an error between an input position coordinate and a detected position coordinate and detecting the input position coordinate as accurately as possible. .

[0006]

In order to achieve the above object, in a coordinate detecting apparatus according to the present invention, a resistive film having a sheet resistance value on a rectangular plane and a power supply contacting each of four corners of the resistive film are provided. A coordinate detecting device for detecting pen input position coordinates by applying different potentials between the power supply terminals at different times to generate intersecting electric fields, wherein a central potential measurement terminal is provided at the center between the power supply terminals. Along with
A parabolic function or an approximate function of the parabolic function, which is connected to a detection circuit section connected to the central potential measurement terminal and the power supply terminal, and detects a detected position coordinate and an actual pen input position coordinate detected by the detection circuit section. And an error correction calculation unit for correcting and calculating the error of the detected position coordinates.

With this configuration, predetermined different potentials are applied to the power supply terminals at the four corners at different times, and the potentials in the coordinate axis direction crossing at the pen input position are detected at the central potential measurement terminal and the power supply terminal position. In this way, the detection circuit unit detects an error correction operation unit that associates the detected position coordinates and the input position coordinates, which are theoretically obtained depending on the configuration of the input panel, with a parabolic function (or an approximation function of the parabolic function). The error of the detected position coordinates can be corrected and output to the outside.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The gist of the present invention will be described below in detail with reference to the embodiments shown in the drawings. 1 (a) and 1 (b) show a schematic configuration diagram and an exploded perspective view of a main part according to the present invention.

According to the present invention, a resistive film 2 attached on a glass substrate 1 with a substantially uniform sheet resistance over substantially the entire surface of a rectangular plane, and a strip-like contact with the upper surface of four sides around the resistive film 2 A peripheral electrode 3 having a resistance lower than the sheet resistance of the resistive film 2, ie, 3 a to 3 d, an insulating film 6 made of a PET (polyethylene terephthalic acid) film or the like having a conductive film 5 adhered to the lower surface thereof, A spacing member 4 such as a double-sided tape for adhering the conductive film 5 of the insulating film 6 and the resistive film 2 at predetermined intervals and facing each other, and power supply terminals A to D provided at the four corners of the peripheral electrodes 3a to 3d ((b) (A is hidden in the figure) and the drive circuit unit 10 that applies a predetermined potential between the power supply terminals A to D at both ends of the opposite side.
And a central potential measuring terminal E-H at the center of each of the four peripheral electrodes 3a-3d (or a resistive film surface in the vicinity thereof), and the potential of the input position pressed by the input pen 7 is applied to the conductive film 5. And a detection circuit section 11 for detecting through the conductive film terminal 5a, each of the power supply terminals A to D, and each of the central potential measurement terminals E to H provided at one edge of the power supply terminal A, and the central potential measurement terminals E to H and the power supply terminals A to D and an error correction operation unit 12 that calculates and corrects an error between the detected position coordinates and the input position coordinates using a parabolic function or an approximate function thereof.

The error correction calculation unit 12 is a microcomputer storing a parabolic function, and is provided in an external detection circuit unit 11 to correct and calculate the detected detection position coordinates. FIG. 2 shows a partially assembled sectional view of FIG. 1 (b), showing a state in which the tip of the input pen 7 presses the insulating film 6, and when the input pen 7 directly presses the upper surface of the insulating film 6. The conductive film 5 on the insulating film 6 side and the resistive film 2 make electrical contact, and the potential at the contact position is transmitted to the conductive film 5,
A conductive film terminal 5a provided at one edge of the conductive film 5 via the conductive film 5 and each of the power supply terminals A to D and each of the central potential measurement terminals E to H
, The potential at the input (contact) position pressed by the input pen 7 is detected.

As shown in FIG. 1 (b), the conductive film terminal 5a, the power supply terminals A to D, and the central potential measurement terminals E to
H is connected to an external connection terminal 8 provided at the center of one side of the glass substrate 1 by a printed wiring 9 made of silver paste, as shown in FIG.
As shown in (a), it is electrically connected to the external detection circuit unit 11.

The input pen in the prior art described above has conductivity and detects the potential at the input position from the lead wire at the rear end of the pen. In this embodiment, the input pen passes through the conductive film 5. The potential at the input position is detected from the conductive film terminal 5a. Further, in this embodiment, the sheet resistance of the resistive film surrounded by the peripheral electrode is set to about 50 times the sheet resistance of the peripheral electrode to suppress the distortion to the extent shown in FIG. I have.

Now, referring to FIG.
A DC potential of 5 V is applied to the power supply terminals B and D at both ends of the pole 3c.
A DC potential of 0 V is applied to feed terminals A and C at both ends of the pole 3b.
Then, the current I flowing through the surrounding electrodes 3a, 3d₀Mock besides
Current I shown_1,I_Two~ I _nFlows through the resistive film 2 and the input
An error occurs between the position coordinates and the detected position coordinates.

FIG. 3 shows the error of the detected coordinate values. FIG. 3 is a diagram in which the entirety of the input quadrangular area is divided into grids by equally-spaced straight lines, and a sequence of coordinate points obtained by pen input and detecting the input position is plotted and displayed on a display screen. Although the actual input position is a coordinate point on a grid sectioned by a straight line, a parabola is drawn because the detected position coordinate includes an error.

Next, a parabolic function required to correct this error is calculated. First, a parabolic function of a sequence of coordinate points in the X-axis direction is obtained. In FIG. 1, a positive potential (DC potential 5 V) is applied to the power supply terminals B and D, and a negative potential (DC potential 0 V) is applied to A and C. As shown in FIG. When the whole surface of the resistive surface is partitioned by lines at regular intervals parallel to the Y-axis and input with a pen, and the coordinate values in the X-axis direction are detected, the detected coordinate value x becomes a parabola including an error as shown in FIG. Draw. Assuming that the coordinate value detected at the position of the point P indicated by the position coordinate (X, Y) on the input screen is (x, Y), the detected coordinate value x is expressed by the following equation (1) and is represented by a parabolic function of Y In the illustrated example of FIGS. 4A and 4B, the detected position coordinate point p is shifted leftward from the input position coordinate point P in parallel with the X axis.

Similarly, a positive potential is applied to points C and D,
A negative potential is applied to points B and B. As shown in FIG. 5 (a), the entire resistive surface surrounded by the surrounding electrodes is divided by equally-spaced lines parallel to the X axis and pen input is performed, and the Y axis is input. When the coordinate value is detected, the detected coordinate value y draws a parabola including an error as shown in FIG. Assuming that a coordinate value detected at the position of the point P indicated by the position coordinates (X, Y) on the input screen is (X, y), the detected coordinate value y is expressed by the following equation (2) and is represented by a parabolic function of X. In the illustrated example of FIGS. 5A and 5B, the detected position coordinate point p is shifted upward from the input position coordinate point P in parallel with the Y axis.

Here, the coordinates (X, Y) of the input position P point,
Coordinates of the detected position point p (x, y), X of the resistance surface, each of the half width in the Y-axis direction L _x, L _y, X, each of the maximum strain on the Y axis w _x, w _y In other words, x = [L _x −w _x {1− (Y ² / L _y ² )}] X / L _x (1) y = [L _y −w _y {1− (X ² / L _x ^2)}] _{Y / L y ····· (2)} (1), by modifying the expression (2), x / X = 1- (w x / L x) {1- (Y ^{_{/ L y) 2} ······ (}} 3) y / Y = 1- (w y / L y) {1- (X / L x) 2} ······ (4) where , Y / L _y ≒ y / L _y , X / L _x ≒ x / L _x Further, by transforming the above equations (3) and (4) and displaying them by X and Y, X = x / [ 1- (w _x / L _x ) {1- (Y / L _y ) ² }] (5) Y = x / [1- (w _y / L _y ) ｛1- (X / L _x ) ² ｝) ・ ・ ・ (6), and input from the parabolic functions of equations (5) and (6) The position coordinates (X, Y) on the screen can be obtained approximately. In addition,
The maximum distortions w _x and w _y in a certain coordinate detection device are theoretically determined if the ratio between the resistance value of the resistance surface surrounded by the peripheral electrode and the resistance value of the peripheral electrode is known. Actually has a measurement because it has variation.

Therefore, at the same time as the known potentials at the points B and D, the potential at the central potential measuring terminal G provided substantially at the center between the points B and D (or the resistive film surface in the vicinity thereof) is measured. By measuring the potential at the center potential measuring terminal H at the center between the points C and D at the same time as the known potentials at the points C and D, as shown in FIGS. 4 (b) and 5 (b). , maximum strain w _x in the coordinate detection apparatus, it is possible to know w _y, obtains a parabolic function for each of the detected coordinate values x, y of the parallel input region outermost end around the electrode, the criterion function this function As described above, a more accurate correction can be made by performing a correction calculation by an external error correction calculation unit.

As described above, by providing a central potential measuring terminal at the center between the two corner electrodes in addition to the four corner electrodes and directly measuring the potential there (or in the vicinity of the resistive film surface), a different coordinate detecting device is provided. In this case, even if the ratio between the resistance value of the resistance surface surrounded by the peripheral electrode and the resistance value of the peripheral electrode is not constant, correction can be individually performed in accordance with the characteristics of the coordinate detection device, and higher-precision coordinate detection can be performed.

As another example, as shown in the schematic diagram of FIG. 6, the distortion is larger than that of the parabola shown in FIG. 3, but the central potential measurement terminals E to H shown in FIG. 1 are omitted. The coordinate values detected in the configuration may be corrected and calculated by an error correction calculation unit. Alternatively, as another example, the distortion is larger than that of the parabola shown in FIG.
As shown in the schematic configuration diagram of FIG. 5, the point electrodes A ′ are provided only at the four corners of the resistance film 2 without providing peripheral electrodes on the four sides around the resistance film.
To D 'may be provided, and as still another embodiment, the configuration in which the central potential measurement terminals E' to H 'are provided in FIG. 7 is also theoretically dependent on the configuration of the input panel. The correction operation can be performed in the same manner as in the technique of FIG. 1 described above using an error correction operation unit that associates the detected position coordinates and the input position coordinates with a parabolic function or an approximate function of the parabolic function. Of course, the configuration of FIG. 1 has the best detection accuracy.

The power supply potential applied to the point electrode or the power supply terminal described above is known, but in order to avoid the effect of potential drop due to the wiring resistance of the power supply line, the resistance film surface near the point electrode or the power supply terminal is used. If a separate potential monitor terminal is provided and the potential of the potential monitor terminal is directly measured, a more accurate potential (monitor potential) can be measured, so that a more accurate correction operation can be performed.

[0022]

As described in detail above, according to the present invention,
As in the prior art, a peripheral electrode that is straight without providing inwardly curved peripheral electrodes on the four sides of the resistive film, or an input panel configuration without peripheral electrodes that are inferior in detection accuracy but easy to manufacture. The position coordinates can be corrected by a parabolic function (or an approximate function thereof) theoretically obtained depending on the configuration of the input panel to output accurate input position coordinates, and a central potential measurement terminal is additionally provided. By measuring the potential at the central position, an extremely useful effect in industry can be achieved, such that a detection error can be corrected by the sheet resistance variation of each coordinate detection device and a more accurate input position coordinate can be output.

[Brief description of the drawings]

FIG. 1 is a schematic structural view and an exploded perspective view of a main part of an embodiment according to the present invention.

FIG. 2 is a partial sectional view of FIG. 1 (b).

FIG. 3 is a diagram illustrating an error of a detected coordinate value according to an embodiment of the present invention.

FIG. 4 is a diagram showing an error occurring in an X-axis coordinate value according to one embodiment of the present invention.

FIG. 5 is a diagram showing an error occurring in a Y-axis coordinate value according to one embodiment of the present invention.

FIG. 6 is a schematic structural view of another embodiment according to the present invention.

FIG. 7 is a schematic structural view of another embodiment according to the present invention.

FIG. 8 is a schematic configuration diagram of still another embodiment according to the present invention.

FIG. 9 is a schematic configuration diagram of a coordinate detection device according to the related art.

10 is a schematic configuration diagram of a peripheral electrode for reducing a detection error in FIG.

[Explanation of symbols]

 2: resistive film 3, 3a to 3d: peripheral electrode 12: error correction operation unit A to D: power supply terminal A 'to D': point electrode E to H, E 'to H': central potential measurement terminal

Claims (3)

[Claims] 1. A resistance film having a sheet resistance value on a rectangular plane, and a power supply terminal contacting each of four corners of the resistance film, and different potentials are applied between the power supply terminals at different times to cross each other. In the coordinate detecting device for detecting a pen input position coordinate by generating an electric field, a central potential measuring terminal is provided at the center between the power supply terminals, and a detection circuit unit connected to the central potential measurement terminal and the power supply terminal. An error correction operation unit for connecting the detected position coordinates detected by the detection circuit unit and the actual pen input position coordinates by a parabolic function or an approximation function of the parabolic function, and correcting and calculating an error of the detected position coordinates. A coordinate detection device, comprising: 2. The resistance film has a resistance lower than the sheet resistance of the resistance film, and is provided with peripheral electrodes provided on four sides around the resistance film, and a power supply contacting each of the four corners of the peripheral electrode. In the coordinate detection device provided with a terminal, connected to a detection circuit portion serving as the power supply terminal, the detected position coordinates and the input position coordinates are associated with a parabolic function or an approximate function of the parabolic function, and the detected position coordinates 2. The coordinate detection device according to claim 1, further comprising an error correction operation unit that performs an error correction operation. 3. A central potential measurement terminal is provided at the center between the power supply terminals, and is connected to a detection circuit section serving as the central potential measurement terminal and the power supply terminal, and the detection position coordinates and the input position coordinates are parabolic. 4. The coordinate detection device according to claim 3, further comprising an error correction operation unit that corrects and calculates an error in the detected position coordinates in association with a function or an approximate function of the parabolic function.