JPH0413719Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a coordinate input device that detects the coordinates of an input position of handwritten characters or figures.

[Prior art]

Coordinate input devices called data tablets, digitizers, and the like that detect the coordinates of input positions of handwritten characters, graphics, etc. are used in computer terminal equipment, handwritten character/graphic communication terminal equipment, and the like.

This type of coordinate input device uses a digital method that digitally quantizes and detects the input coordinate position using a diode, and another that uses two resistive sheets coated with a resistive film to detect the input coordinate position. There is an analog method in which the position is detected analogously as X and Y coordinates on the resistive film.

Since the former digital type has a complicated circuit configuration and is disadvantageous in terms of manufacturing costs, the latter analog type has been mainly used in recent years.

There are two types of analog coordinate input devices: a capacitive type that presses the input surfaces of two resistive sheets with an electric pen powered by AC power, and a capacitive type that presses the input surfaces of two resistive sheets with an indicator pen. A contact method has been proposed in which the input coordinate position is detected by voltage or current by pressing the button.

The configuration and operation of a conventionally proposed contact type coordinate input device will be explained using FIGS. 3 and 4.

Here, FIG. 3 is a partially cutaway plan view showing the configuration of a conventionally proposed coordinate input device, and FIG. 4 is a sectional view taken along the line AA in FIG. 3.

A thin first resistive film 2 made of indium oxide or the like is deposited on a first insulating film 1 formed of a substantially square plate-shaped polyester film or the like by means of vapor deposition, sputtering, etc. to form a first resistive sheet 3. is formed. In this first resistive sheet 3, first current collecting electrodes 4 are extended in parallel to each other at both ends of the first resistive film 2. Furthermore, a plurality of auxiliary electrodes 5 are extended and formed on the first resistive film 2 in parallel to these two first current collecting electrodes 4 .

Similarly, a second resistive film 7 is deposited on the second insulating film 6 to form a second resistive sheet 8. Second current collecting electrodes 9 are formed parallel to each other. Further, a plurality of auxiliary electrodes 10 are formed on the second resistive film 7 in parallel to the second current collecting electrode 9.

The first and second resistance sheets 3 and 8 thus formed are connected to the first and second current collecting electrodes 4 and 9.
are arranged facing each other perpendicularly to each other, and their peripheral portions are fixed by a frame-shaped insulating spacer 11.

On the side of the first resistance sheet 3, one end of the first current collecting electrode 4 is connected to the positive electrode of a battery 13 via a switch 12, and the negative electrode of the battery 13 is grounded. Further, at one end of the first current collecting electrode 4, a lead terminal _t2 is provided.
Further, one end of the other first current collecting electrode 4 is grounded via a switch 14.

Similarly, on the second resistance sheet 8 side, one end of one second current collecting electrode 9 is connected to the switch 1.
2 to the positive electrode of the battery 13,
The negative pole of is grounded. Also, the second
An extraction terminal _t3 is provided at one end of the current collecting electrode 9. Furthermore, one end of the other second current collecting electrode 9 is grounded via a switch 14.

The switches 12 and 14 mentioned above are controlled by a computer, for example, to set the DC constant voltage E to the first and second switches.
The voltage is applied alternately to the first and second current collecting electrodes 4 and 9 of the resistive sheets 3 and 8.

Now, switch 12 is switched to terminal t ₅ side, switch 14 is switched to terminal t ₆ side, DC voltage E is applied to first resistor sheet 3, and second resistor sheet 8 is applied.
in the open state, apply pressure to any point p on the second resistance sheet 8 with an indicator pen, and press the point p on the first and second resistance films 2 and 7 of each resistance sheet 3 and 8.
Make point contact at the points. Then, a potential gradient is generated in the x direction in the resistive film 2 of the first resistive sheet 3, and a divided voltage e _x is generated at a point p on the first resistive film 2, and this voltage e _x is is detected by the lead terminal t ₃ from the second current collecting electrode 9 of the resistor sheet 8 . Here, the coordinates of point p are (x, y), and the first resistance sheet 3
Letting L be the distance between both current collecting electrodes 4, the following equation holds true under the condition that the resistance value per unit area of the first resistive film 2 is uniform.

e _x /E=x/L (1) Therefore, by finding e _x , the x coordinate of point p can be found. In addition, by switching the switches 12 and 14 after the x-coordinate is detected, the voltage is directly switched and connected to the second resistor sheet 8, and the first resistor sheet 3
When it is in the open state, the y-coordinate of point p is set to the current collecting electrode 4 of the first resistor sheet 3 using the same detection principle as described above.
The voltage e _y can be detected by the output terminal t ₂ .

The auxiliary electrodes 5 and 10 formed on the first and second resistive films 2 and 7 have the function of forming equipotential positions on the respective resistive films and correcting distortion of equipotential lines on the resistive films. have

That is, in order to accurately detect the input coordinates, the film thicknesses of the first and second resistive films 2 and 7 should be set constant over the entire surface, and the resistance value per unit area should be set as follows.
It is necessary to hold it constant at any position on the resistive film. However, as a practical matter, the first
Also, it is difficult to form the second resistive films 2 and 7 to have the same thickness, so that slight variations in film thickness inevitably occur. Further, the resistive films 2 and 7 may be damaged during the manufacturing process or during use, resulting in partial discontinuity. Therefore, for example, if the thickness of the first resistive film 2 of the first resistive sheet 3 is non-uniform and there is some discontinuity, the equipotential lines on the first resistive film 2 Since it is no longer parallel to the current collecting electrode 4, even at the same x-coordinate position on the first resistive film 2,
If the y-coordinate position is different, the measured voltage value will be different, and there is a possibility that equation (1) will not hold.

In this case, if the auxiliary electrodes 5 and 10 are formed on the first and second resistive films 2 and 7 as described above, for example, when measuring on the first resistive film 2, the auxiliary electrodes 5 forcibly sets an equipotential position on the first resistive film 2. Therefore, in the region of the first resistive film 2 sandwiched between the auxiliary electrodes 5, due to non-uniform film thickness or the presence of scratches as described above, the resistance value per unit area changes and the equipotential line is changed. Even if a distortion exists, equipotential positions are forcibly set on both sides by the auxiliary electrodes 5 that sandwich the area, and the distortion of the equipotential line is compressed between these equipotential positions. Similarly, on the second resistive film 7, the distortion of the equipotential lines is corrected by the auxiliary electrode 10.

In this way, distortions in the equipotential lines on the resistive film caused by uneven film thickness or the presence of scratches are compressed without affecting adjacent regions, and the linearity of the equipotential lines is improved overall. It will be significantly improved.

[Problem that the invention attempts to solve]

As mentioned above, according to the previously proposed coordinate input devices, by providing an auxiliary electrode, distortions in equipotential lines due to non-uniformity of the thickness of the resistive film or the presence of scratches can be corrected, and coordinate input is possible. Highly accurate measurements of position can be made.

However, with the conventionally proposed coordinate input devices, it is not possible to correct the potential gradient that occurs in the current collecting electrode, so even if the thickness of the resistive film is uniform and there are no scratches on the resistive film, A distortion of the equipotential lines exists between the current collecting electrode and the adjacent auxiliary electrode.

In other words, as shown in Fig. 5, the current collecting electrode formed by Ag printing is formed in a shape with an extremely large length compared to the cross-sectional area s. It is also necessary to take into account the resistance of the electrodes. This tendency becomes more pronounced as the coordinate input device becomes larger and the length of the current collecting electrode becomes longer, since the width of the current collecting electrode cannot be made too large due to manufacturing costs.

In FIG. 5, the potential of one end of the current collecting electrode 4 connected to the battery 13 is e ₁ , the potential of the other end of the current collecting electrode 4 is e ₄ , the resistivity of Ag is ρ, and the voltage of the battery 13 is E. Then, the following equation holds.

e ₁ =E (2) e ₄ =E−i ₀ ·ρ·/s (3) However, in equation (3), i ₀ is the current flowing through the current collecting electrode 4.

Obviously, e ₁ > e ₄ from equations (2) and (3), and if the potentials e ₂ and e ₃ in the longitudinal direction of the current collecting electrode 4 are determined, e ₁ > e ₂ > e ₃ > It becomes e ₄ . For this reason, from the points of each potential e ₁ to e ₄ on the current collecting electrode 4, currents i ₁ to i ₄ (i ₁ > i ₂ > i ₃ > i ₄ ) having different current densities flow through the resistive film 2. flows into.

Therefore, the distribution of equipotential lines in the region 2D on the resistive film 2 sandwiched between the current collecting electrode 4 and the adjacent auxiliary electrode 5 is as shown by the dotted line in FIG. Even if the thickness is uniform and there are no scratches on the resistive film, the equipotential lines will be greatly disturbed in the region 2D.

If the equipotential lines are greatly disturbed in the region 2D in this way, this influence will affect the auxiliary electrode 5 adjacent to the current collecting electrode 4.
As a result, a slight potential deviation occurs in the longitudinal direction of the auxiliary electrode 5. When high precision measurement is required, the auxiliary electrode 5 is used to set a reference potential for measurement.
Even if the potential deviation is minute, it will adversely affect the measurement.

The present invention was developed in view of the current state of the coordinate input devices that have been proposed in the past, as described above, and its purpose is to ensure that even if equipotential lines are disturbed due to the potential gradient generated in the current collecting electrode, An object of the present invention is to provide a coordinate input device that can significantly reduce minute potential deviations on the surface of an auxiliary electrode adjacent to a current collecting electrode arranged in parallel, and can perform highly accurate measurements. .

[Means for solving problems]

In order to achieve the above object, in the present invention, first current collecting electrodes are formed parallel to each other at both ends of the first resistive film, and second current collecting electrodes are formed parallel to each other at both ends of the second resistive film. The first and second current collecting electrodes are arranged perpendicularly to each other, and the first and second resistive films are disposed facing each other, and the first and second current collecting electrodes are arranged to face each other, and the first and second current collecting electrodes are arranged to face each other, and the first and second current collecting electrodes are arranged to face each other. In a coordinate input device in which a plurality of auxiliary electrodes are formed in parallel to a second current collecting electrode,
The area between adjacent auxiliary electrodes adjacent to the first and second current collecting electrodes is a used area, and the area between the first and second current collecting electrodes and the adjacent auxiliary electrode is an unused area, Further, the width of the adjacent auxiliary electrode is set wider than the width of other auxiliary electrodes.

[Effect]

In the present invention, since the width of the adjacent auxiliary electrode adjacent to the first and second current collecting electrodes to which a DC voltage is applied is set wider than the width of the other auxiliary electrodes,
Potential deviations are corrected in unused areas within the current collecting electrode and the adjacent auxiliary electrode, and minute potential deviations are significantly reduced on this side of the adjacent auxiliary electrode. Therefore, it is possible to measure the coordinate input position with high precision using the adjacent auxiliary electrode as a reference.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to FIGS. 1 and 2.

Here, FIG. 1 is a plan view of a coordinate input device according to an embodiment of the present invention, and FIG. 2 is an explanatory diagram showing potential distribution at adjacent auxiliary electrodes provided in the coordinate input device. Note that although only the first resistance sheet 3 side is illustrated in FIGS. 1 and 2, similar to the conventionally proposed coordinate input device already explained using FIGS. 3 and 4, In the embodiment of the present invention, the current collecting electrode 9 is orthogonal to the current collecting electrode 4, and the second resistive sheet 8 is disposed opposite to the first resistive sheet 3.

As shown in FIG. 1, the first resistance sheet 3 side is
In the embodiment of the present invention, the width d of the adjacent auxiliary electrode 5N disposed adjacent to the first current collecting electrode 4 is set to be wider than the other auxiliary electrodes _d0 .

When measuring coordinate input, when the DC voltage of the battery 13 is applied to one end of the first current collecting electrode 4, as described above, due to the voltage drop caused by the resistivity of the first current collecting electrode 4. , distortion occurs in the equipotential lines as shown by dotted lines in FIG. Due to this distortion of the equipotential lines, the region 2 of the first resistive film 2 between the first current collecting electrode 4 and the adjacent auxiliary electrode 5N adjacent thereto is
If four points are selected at the end of the N adjacent auxiliary electrode 5N as shown in _FIG .
E ₄ ′, and these clearly have the following relationship.

E ₁ ′>E ₂ ′>E ₃ ′>E ₄ ′ (4) For this reason, different potential distributions are set in the longitudinal direction on the surfaces of the adjacent auxiliary electrodes 5N that are in contact with the regions 2N. Taking into account the resistivity of the adjacent auxiliary electrode 5N, a current flows between these potential distribution points within the adjacent auxiliary electrode 5N as shown by the dotted line in FIG. 2, so the equipotential line within the adjacent auxiliary electrode 5N is On the region 2N side, it is quite disordered.

Therefore, if the width of the adjacent auxiliary electrode 5N is narrow, a potential deviation will occur on the surface of the adjacent auxiliary electrode 5N on the first resistive film 2 side, which makes it difficult to use the adjacent auxiliary electrode 5N as a reference potential plane for measurement. Undesirable. Therefore, in the present invention, the width d of the adjacent auxiliary electrode 5N is set wider than the width d ₀ of the other auxiliary electrodes.

In addition, a region 2N of the first resistive film 2 between the first current collecting electrodes 4 formed parallel to each other and the adjacent auxiliary electrodes 5N adjacent thereto is an unused region where no input operation is performed. ing. Therefore, the area of the first resistive film 2 between the adjacent auxiliary electrodes 5N arranged in parallel with each other is the area used for input operations.

Furthermore, in the above embodiment, the width of the adjacent auxiliary electrode 5N adjacent to the first current collecting electrode 4 that is grounded is also set to d, which is set wider than the width d ₀ of the other auxiliary electrodes 5. 3, the resistance distribution between the first current collecting electrodes 4 formed in parallel with each other is formed tightly and symmetrically in the direction perpendicular to the longitudinal direction of the first current collecting electrodes, allowing accurate coordinate input positions. The structure is such that measurement is possible.

Here, for example, in an A3 size coordinate input device, the total resistance value between the first and second current collecting electrodes and their respective adjacent auxiliary electrodes is 0.5 to 20Ω, and the total resistance value between the mutually opposing current collecting electrodes is 0.5 to 20Ω. is about 1000Ω. Further, in the A3 size, the width of the first and second current collecting electrodes is 2 mm, the width of the adjacent auxiliary electrode is 1 to 2 mm, and the width of the other auxiliary electrodes is 0.5 mm or less. Naturally, the width and resistance value of each electrode will take different values depending on the dimensions of the coordinate input device and the interface board to be connected.

The rest of the configuration is the same as the previously proposed coordinate input device already explained using FIGS. 3 and 4, so a redundant explanation thereof will be omitted.

Although the first resistance sheet 3 has been described above, the second resistance sheet has exactly the same structure, and the first and second resistance sheets serve as the first and second current collecting electrodes. They are arranged so as to be orthogonal to each other and facing each other.

Next, the operation of the embodiment of the present invention having such a configuration will be explained.

When measuring the x-coordinate of coordinate input, by switching the switch 12 to the terminal t ₅ side and the switch 14 to the terminal t ₆ side, the distance between the first current collecting electrodes 4 connected to the first resistive film 2 is The voltage of battery 13 is applied to . By applying the voltage of the battery 13, the first current collecting electrode 4 connected to the battery 13 has a second
As shown in the figure, the potentials E ₁ to E ₄ are distributed with potential deviations.

In the region 2N of the first resistive film 2, equipotential lines are distorted as shown by dotted lines in FIG. 2 in accordance with the potential distribution of the first current collecting electrode 4.
At the end of the region 2N on the side of the adjacent auxiliary electrode 5N,
A potential distribution from E ₁ ′ to E ₄ ′ occurs. These potentials
Equation (4) holds between E ₁ ′ to E ₄ ′, and there is a relationship expressed by the following equation.

E ₁ > E ₁ ′, E ₂ > E ₂ ′, E ₃ > E ₃ ′, E ₄ > E ₄ ′...(5) Within the adjacent auxiliary electrode 5N, the area given to the region 2N side of the adjacent auxiliary electrode 5N Due to the potential distribution, taking into account its resistivity, a current, a portion of which is shown by the dotted line in FIG. 2, is generated.

Due to the generation of such current, the adjacent auxiliary electrode 5
On the area 2N side of N, the equipotential lines are greatly disturbed, but since the width of the adjacent auxiliary electrode 5N is set sufficiently large, the next auxiliary electrode 5
On the side surfaces, the equipotential lines are almost parallel to the longitudinal direction of the adjacent auxiliary electrodes 5N.

Therefore, the surface of the next auxiliary electrode 5 next to the adjacent auxiliary electrode 5N becomes a substantially equipotential surface, and with this adjacent auxiliary electrode 5N as a reference potential, a voltage signal e _x corresponding to the x coordinate of the pressed point of the coordinate input is extracted. Detection can be performed with extremely high accuracy from terminal _t3 .

To measure the y-coordinate of the pressing point, as already explained using FIG. 3, switch 12 to the terminal _t4 side and switch 14 to the terminal _t7 side, The voltage of the battery 13 is applied between the current collecting electrodes, and a voltage signal e _y corresponding to the y-coordinate of the pressing point is measured from the extraction terminal t ₂ .

In this way, compared to conventionally proposed methods, a minute potential is generated on the adjacent auxiliary electrodes based on the resistivity of the adjacent auxiliary electrodes 5N and 10N adjacent to the first and second current collecting electrodes 4 and 9. By also correcting deviations, it is possible to measure the coordinate input position with extremely high precision.

[Effect of idea]

As explained in detail above, according to the present invention, the adjacent auxiliary electrodes adjacent to the first and second current collecting electrodes formed on the first and second resistive films are made wider than other auxiliary electrodes. As a result, it is possible to provide a coordinate input device that can greatly reduce minute potential deviations that occur on adjacent auxiliary electrodes and can measure coordinate input with high accuracy.

[Brief explanation of the drawing]

FIG. 1 is an explanatory plan view of a coordinate input device according to an embodiment of the present invention, and FIG. 2 is an explanatory diagram showing potential distribution at adjacent auxiliary electrodes provided in the coordinate input device.
FIG. 3 is a partially cutaway plan view showing the configuration of a conventionally proposed coordinate input device, and FIG. 4 is A-A in FIG. 3.
The cross-sectional view, FIG. 5, is an explanatory diagram showing the influence of the potential distribution of the current collecting electrode in the coordinate input device. DESCRIPTION OF SYMBOLS 1... First insulating film, 2... First resistive film, 2N... Unused area, 3... First resistive sheet, 4... First current collecting electrode, 5... Auxiliary electrode, 5
N...Adjacent auxiliary electrode.

Claims (1)

[Scope of utility model registration request] First current collecting electrodes are formed parallel to each other at both ends of the first resistive film, second current collecting electrodes are formed parallel to each other at both ends of the second resistive film, and these first and second current collecting electrodes are formed parallel to each other at both ends of the second resistive film.
The current collecting electrodes of the first and second electrodes are arranged perpendicularly to each other.
In the coordinate input device, a plurality of auxiliary electrodes are formed on the first and second resistive films in parallel with the first and second current collecting electrodes, respectively. The area between the auxiliary electrodes adjacent to each of the current collecting electrodes is a used area, and the area between the first and second current collecting electrodes and the adjacent auxiliary electrode is an unused area, and the width of the adjacent auxiliary electrode is A coordinate input device characterized in that the width of the auxiliary electrode is set wider than the width of other auxiliary electrodes.