JPS61294534A - Touch panel input device - Google Patents

Abstract

PURPOSE:To improve the detecting accuracy by measuring the distribution of voltage applied to a touch panel and then detecting a contact position of a touch panel according to the measured distribution of voltage. CONSTITUTION:A CPU 2 of a touch panel input device is connected to an A/D converter 3, and an I/O port 4 and a memory 5 via a bus. The electrode terminals of the upper and lower panels of a touch panel 1 are connected to the converter 3 from gates 8 (8a-8d) via buffer amplifiers 7 (7a-7d). Furthermore, the electrode terminals (A) and (C) of the upper and lower panels at the side of a voltage application circuit of a conduction sheet are connected to the converter 3 via the amplifiers 7a and 7c and gates 8a and 8c. Thus the voltage between the terminals at both ends of the conduction sheet is measured when the voltage is applied. Then the actual voltage distribution is obtained on the surface of the conduction sheet from the measured both-end voltage. Based on this voltage distribution, it is possible to detect accurately the push of a specific position to produce the voltage from the conduction sheet at the other side.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field The present invention relates to improving the accuracy of contact position detection in an input device having a transparent sheet-like touch panel switch installed on a CRT screen or the like.

...) Summary of the Invention The touch panel input device according to the present invention measures the voltage at both ends of one conductive sheet when a voltage is applied to the conductive sheet, and determines the actual voltage distribution of the conductive sheet from the voltage. It is possible to determine an accurate contact position by referring to the actual voltage distribution from the measured value obtained when two conductive sheets come into contact with each other by pressing.

(C) Prior Art and Its Disadvantages ■ Description of Analog Touch Panel Switch Used in Touch Panel Input Device First, FIG. 5 shows the configuration of a touch panel switch. FIG. 5 shows an analog touch panel switch. This analog touch panel switch is composed of an upper panel 10 and a lower panel 20. The upper panel 10 will now be explained. The touch panel surface is made of a conductive sheet 1) in which a conductive film such as ITO (1de on Indius tin O) is deposited on a resin film base material, and electrode terminals 12L and 13 are formed at both ends of the conductive sheet 1). This electrode 12.
Lead wires 14 and 15 are connected to 13, and a voltage application circuit (not shown) is connected when the touch panel switch is operated.
to lead wires 14, 15. A voltage (Vcc) is applied to the conductive sheet (1) via the electrode terminals 12.13. A voltage gradient (voltage distribution) occurs on the conductive sheet 1). The lower panel 20 also has the same configuration as the upper panel 10 described above, and these upper panels 10. The lower panel 20 is arranged so that the voltage gradient directions are perpendicular to each other (in this figure, the voltage gradient of the upper panel 10 is in the vertical (Y-axis) direction, and the voltage gradient of the lower panel 20 is in the horizontal (X-axis) direction). An analog touch panel switch is constructed by arranging the conductive film surfaces facing each other at a very small interval. The voltage (Vcc) is applied to the upper panel 10.
are applied alternately to the lower panel 20.

(2) Description of conventional touch panel input device FIG. 4 is a block diagram of a conventional touch panel input device including the touch panel switch described above. , CPU 2 connects A/D converter 3 . to A/D converter 3 . I10 port 4 and memory 5
It is connected to the. A ground electrode terminal 13 on the upper panel of the touch panel 1 is connected to the A/D converter 3 via a gate 8b and a buffer amplifier 7b. A detection voltage in the X-axis direction of the contact point (contact position) of the touch panel switch 1 is inputted from this electrode terminal 13, and is connected to the A/D converter 3 via the gate 8d and the buffer amplifier 7d on the lower panel. A detection voltage in the Y-axis direction of the contact point is inputted from the ground side electrode terminal 15 of the contact point.

Here, the electrode terminals 12, 13, 14.15 are called A, B, C, and D, respectively. A, B, C, and D have switching transistors 6a, 6b, 6c, respectively.
6d is connected. These switching transistors 6a, 6b, 6c, and 6d correspond to a switch circuit.

These switching transistors are CPU2-1)0
The on signals a, b, c, and d from boat 4 turn on and off alternately in combinations of 5a, 5b, 5c, and 5d.
Repeatedly turning off, the switching transistors 6a, 6b
When switching transistors 5c and 5d are turned on, a voltage (Vcc) is applied to the upper panel, and when switching transistors 5c and 5d are turned on, a voltage (Vcc) is applied to the lower panel. Further, when the voltage (Vcc) is applied to the upper panel, the gate 8d is turned on by the on signal e, and the contact detection voltage in the Y-axis direction is transmitted from the lower panel to the A/D converter 3.
When the voltage is applied to the lower panel, the gate 8b is similarly turned on by the on signal f, and the X-axis direction contact detection voltage is inputted to the A/D converter 3 from the upper panel.

That is, when a voltage (Vcc) is applied to the upper panel IO while the touch panel switch 1 is pressed and the upper panel IO and the lower panel 20 are in contact with each other, the voltage generated at the contact point of the upper panel is It will be applied to the lower panel via the contacts. Since the buffer amplifier 7d has a very high input impedance, the lower panel 2
The membrane resistance of 0 and the current flowing from the upper panel to the lower panel can be ignored, and the voltage manually applied to the A/D converter 3 is the voltage gradient caused by the voltage (Vcc) applied to the upper panel 10. It can be regarded as the voltage (Vy) at the contact point. Since the conductive sheet of the upper panel 10 is configured so that the voltage gradient is uniform, the vertical direction (Y-axis direction) position (Y coordinate value) of the contact point is determined by the voltage input to the A/D converter 3. can be detected. The voltage (Vcc) is applied alternately to the upper panel lO1 and the lower panel 20 as described above, and immediately after the Y coordinate value is detected by applying the voltage (Vcc) to the upper panel 10, this time, the voltage (Vcc) is applied to the lower panel 20. Application of voltage (Vcc) to and gate) 8
b is turned on. Voltage to lower panel 20 (Vcc
) The voltage generated at the contacts on the lower panel by applying
This is now applied to the upper panel via the contacts. The buffer amplifier 7b has the same configuration as the buffer amplifier 7b and has a very high input impedance.
The membrane resistance of the upper panel 10 and the current flowing from the lower panel to the upper panel can be ignored, and the voltage input to the A/D converter 3 is equal to the voltage (Vcp
) is applied, resulting in a voltage gradient at the contact point (V
x). Like the conductive sheet of the upper panel 10, the conductive sheet of the lower panel 20 is configured to have an even voltage gradient, so the voltage input to the A/D converter 3 causes the contact to move in the left-right direction (X-axis direction). The position (X coordinate value) of can be calculated. These, X, X
The contact point (pressed position) can be accurately detected using the coordinate values. Note that the switching transistors 6a, 6
On/off signals (a, b, c, d) for gates b, 6c, 5d and on/off signals (e, f) for gates 8b, 8d are generated by the CPU 2 and supplied via the I10 port 4.

A touch panel input device as described above is usually installed on a CRT screen of an automatic transaction processing device or the like, and is used to determine whether a key displayed on the screen is pressed. That is, when a press (contact) of a coordinate point corresponding to the image position of a displayed key is detected, it is determined that the key has been pressed, and the other control units are notified.

■Description of other touch panel switches FIG. 6 shows another touch panel switch. This touch panel switch is constructed from a conductive sheet that can eliminate the voltage gradient distortion that is a drawback of the touch panel switch shown in FIG. 5, and can obtain an accurate stepwise voltage gradient. In other words, in the analog touch panel switch described above, a conductive sheet forming the touch panel surface has a uniform conductive film formed over the entire surface, but it is technically extremely difficult to form a conductive film uniformly over the entire surface. in,
Differences in the thickness (resistance value) of the conductive film often occurred. If such a conductive sheet is used in the analog touch panel, the voltage gradient will not be uniform, resulting in errors in position detection. In order to eliminate this drawback, this touch panel switch with a striped touch panel surface is designed to have a uniform voltage gradient by separating the resistor that causes the voltage gradient from the touch panel surface that detects the contact position. be. The upper panel 30 will be explained. Resistors 32a and 32b are formed on both sides of the upper panel 30, and a conductive sheet 31 on which conductor stripes are formed at regular intervals connecting the resistors constitutes the touch panel surface. A voltage (Vcc) is applied across this resistor. This voltage (
The application of Vcc) causes the voltage ramp on resistor 328.32b. A resistor 32a connected to each of the transparent conductor stripes 31a to 31g,
A voltage of the same magnitude as the voltage on 32b is occurring. By arranging the touch sheets having the above structure one above the other so that the respective transparent conductor stripes intersect perpendicularly, it is possible to perform the same operation as the analog touch panel switch using the uniform conductive sheet. However, in this figure, contrary to the analog touch panel switch shown in FIG. 5, the upper panel 30 is arranged so as to generate a voltage gradient in the X-axis direction, and the lower panel 40 is arranged so as to produce a voltage gradient in the Y-axis direction. ing.

■Disadvantages of the above-mentioned conventional touch panel input device As mentioned above, the voltage (Vcc) for creating a voltage gradient is applied by closing the switch circuit (switching transistor), but even if the switching transistor is in the on state. , has a certain degree of forward resistance, and the entire voltage (Vcc) is not applied across the conductive sheet. Figure 3 shows an equivalent circuit and voltage slope showing the state of application of voltage (Vcc) to the conductive sheet. It is a graph. The case of applying voltage to the conductive sheet of the upper panel will be explained.

What is the internal resistance value of the switching transistor 6a on the voltage (Vcc) side when it is on? ? 1. The resistance value of the conductive sheet is R2
, if the internal resistance value of the switching transistor 6b on the ground side when it is on is R3, then these resistances R1, l? 2.R
3, Vcc is Vl, V2. V3 is divided into two parts. Therefore, the actual voltage slope on the conductive sheet is V2 +
The slope P is due to the voltage v2 between V3 and v3. The same applies to the lower panel and the switching transistors 6c and 6d.

However, in the above-mentioned conventional touch panel input device, since it has not been possible to measure the voltage across the conductive sheet when voltage (Vcc) is applied to the conductive sheet, the entire Vcc is applied to both ends of the conductive sheet, thereby increasing the voltage. It was assumed that there was a slope. The voltage slope based on the above estimation is shown in Q. Here, L is the length between both ends of the touch panel switch (upper panel). In reality, the voltage gradient occurring over this length is the state shown in P above, so if the contact position is detected by the voltage gradient Q above, a deviation error as shown by the arrow in the figure will occur. . If this error is significant, the pressed key may be incorrectly determined.

If such a malfunction occurs, for example, in the touch panel input device installed on the CRT screen of an automatic transaction processing device, the password entered manually by the user.

There was a risk that the transaction would be processed by erroneously detecting the human input value such as the amount to be withdrawn, causing a serious problem with the transaction.

(d1 Purpose of the Invention In view of the above-mentioned drawbacks, the object of the present invention is to provide a touch panel input device that can accurately measure the voltage applied to a touch panel switch and accurately detect the contact position based on the voltage applied to the touch panel switch. shall be.

(el) Structure and effect of the invention This invention provides a voltage application method in which electrode terminals are provided at both ends of two opposing conductive sheets, and a voltage is applied to the electrode terminal of one of the conductive sheets to form a voltage distribution on its surface. and a switch circuit for opening and closing the application of this voltage, and a voltage measuring circuit for measuring the voltage obtained by the other conductive sheet when the two conductive sheets are in contact with each other, the voltage measuring circuit In a touch panel switch that detects a contact position from a measured value of and the voltage distribution, an inter-terminal voltage measuring means for measuring the voltage of the electrode terminals at both ends when a voltage is applied to the one conductive sheet; The method is characterized by comprising means for determining the actual voltage distribution on the surface of the one conductive sheet from the measured value of the voltage measuring means.

According to the present invention, configured as described above,
The inter-terminal voltage measuring means can measure the voltage between the terminals at both ends of the conductive sheet when voltage is applied, and the actual voltage distribution on the surface of the conductive sheet can be determined from the measured voltage at both ends of the conductive sheet. According to this voltage distribution, it is possible to accurately detect which position was pressed to obtain the voltage obtained by the other conductive sheet, and the detection accuracy of the contact position can be significantly improved. . As a result, it is possible to eliminate malfunctions of, for example, an automatic transaction processing device equipped with this touch panel input device, and it is also possible to improve the reliability of the device.

(fl Embodiment FIG. 1 is a circuit diagram of a touch panel input device according to an embodiment of the present invention. In this circuit diagram, the difference in configuration from the conventional touch panel input device explained in FIG. 4 is that the upper panel, the lower panel Connect electrode terminals A and C on the voltage application circuit side ((Vcc) side) of the conductive sheet on the side panel to the buffer amplifier 7.
A/D converter 3 via a, 7c and gates 8a, 8c.
This is the point connected to . Hereinafter, in this figure, the same parts as those in the block diagram shown in FIG. 4 will be given the same numbers and the explanation will be omitted.

FIG. 2 is a flowchart showing the operation of the CPU 2 of the above embodiment. In step nl (hereinafter, step ni is simply referred to as ni), the switching transistors 5a, 5
b is turned on to apply voltage (Vcc) to the upper panel.

At n2, the gates 8a and 8b are turned on in sequence and the voltages Va and Vb of the electrode terminals A and B on the upper panel are read. Game on n3) Turn on 8d to detect contact. When the upper panel and the lower panel are in contact due to pressing, the voltage generated on the contact point of the upper panel due to the voltage gradient is transmitted to the lower panel via the contact point, so that the voltage from the electrode terminal of the lower panel is transmitted to the lower panel. The voltage vy can be detected. When not in contact (not pressed), vy=o. At n4, the Y coordinate value of the contact position is detected based on the above measured value. That is, the Y coordinate value y is given by the following formula: y = Vy/ (Va - Vb) Here, Va is V2 + Va in Fig. 3,
vb is v3 in FIG.

The above was an operation for applying voltage (Vcc) to the upper panel and finding the Y coordinate value of the contact position, but below, applying voltage (Vcc) to the lower panel and calculating the X coordinate value of the contact position. This is an action to find out.

At n5, switching transistors 6c and 6d are turned on to apply a voltage (Vcc) to the lower panel.

At n6, the gates 13c and 8d are turned on in sequence and the voltages Vc and Vd of the electrode terminals C and D on the lower panel are read. At n7, the gate 8b is turned on and the voltage Vx corresponding to the X coordinate of the contact position is detected. Similar to the voltage Vy, this voltage Vx is also Vx when the touch panel switch is not pressed.
x=O. At n8, the X coordinate value X of the contact position is detected based on the above measured value.

The detection formula is given by the following formula: z = VX / (VC - Vd) where Vc is V2 + Va in Figure 3,
Vd is v3 in FIG.

The coordinates (x, y) obtained through the above operations are the exact coordinates of the contact position.

In this way, if the touch panel input device with the above configuration is used, the actual voltage gradient (voltage distribution) on the conductive sheet can be determined based on the measured values Va, Vb, Vc, and Vd. voltage Vx, Vy
It becomes possible to detect the exact position of contact. As a result, it is possible to prevent malfunctions due to detection errors, and it is also possible to contribute to improving the trustworthiness of an automatic transaction processing device or the like equipped with the touch panel input device according to this embodiment.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a touch panel input device that is an embodiment of the present invention, FIG. 2 is a diagram showing the operation when voltage is applied to the touch panel of the above embodiment, and FIG. 3 is a general diagram of a touch panel input device including the above embodiment. FIG. 3 is a diagram showing a state of voltage application to a conductive sheet of a typical touch panel input device. Further, FIG. 4 is a block diagram of a conventional touch panel input device, and FIGS. 5 and 6 are diagrams showing the structure of a touch panel switch. ? a, 7c - buffer amplifier, 8a, 8cm gate.

Claims (1)

[Claims] (1) A voltage application circuit that provides electrode terminals at both ends of two opposing conductive sheets and applies a voltage to the electrode terminal of one conductive sheet to form a voltage distribution on its surface, and a voltage application circuit that opens and closes the application of this voltage. and a voltage measuring circuit that measures the voltage obtained by the other conductive sheet when the two conductive sheets come into contact, and from the measured value of the voltage measuring circuit and the voltage distribution. In a touch panel switch that detects a contact position, a terminal-to-terminal voltage measuring means measures the voltage of the electrode terminals at both ends when a voltage is applied to the one conductive sheet; means for determining the actual voltage distribution on the surface of the conductive sheet.