JPH0212518A - Touch coordinate input device - Google Patents

Abstract

PURPOSE:To detect the position coordinate of a support with high accuracy even when the capacity of the support is large by correcting a contact position coordinate corresponding to the impedance of the support and a calculated contact position coordinate when the impedance of the support exceeds a prescribed value. CONSTITUTION:When a finger 14 is touched on a touch panel 18, either stored impedance exceeds the prescribed value, and the presence of touch is decided, and the impedance observing from each terminal side of L1, R1, U1, and D1 is measured and stored. Next, the coordinate of an indication position is calculated by using the impedance stored before the touch and in touching, and the capacity CB of a human body is found from the impedance in touching measured previously and stored in a memory. When the capacity CB of the human body exceeds a comparatively large prescribed value, the coordinate value (X, Y) is corrected. In such a way, it is possible to detect a found coordinate value with high accuracy.

Description

[Detailed Description of the Invention] [Table of Contents] Overview Industrial Application Fields Prior Art (Figure 6) Problems to be Solved by the Invention Means and Effects for Solving the Problems (Figure 5) Examples (1 to 3) Figure 4) Effects of the invention [Summary] Regarding a touch coordinate human-powered device that measures the impedance seen from each terminal of a touch panel provided with a resistive film to determine the coordinates of a touch position on the touch panel, the capacitance of the pointer is relatively large. With the aim of detecting position coordinates with high precision, a resistive film is placed on a substrate, and one or more pairs of opposing terminals are connected to a touch panel that serves as the resistive film, and both terminals of each pair are kept at the same potential. impedance measuring means for measuring the impedance seen from one of the terminals and the impedance seen from the other terminal, and the touch position using the impedance measured before and during contact of the pointer with the touch panel; contact position coordinate calculation means for calculating the coordinates of the
In a touch coordinate input device having a touch coordinate input device, the impedance of the pointer is determined from the measured impedance, and if the impedance of the pointer is greater than or equal to a predetermined value, the impedance of the pointer and the calculated contact position coordinates are calculated. The contact position coordinate correction means is configured to correct the contact position coordinates accordingly.

[! FIELD OF THE INVENTION The present invention relates to a touch coordinate input device that measures impedance seen from each terminal of a touch panel provided with a resistive film to determine contact position coordinates on the touch panel.

[Prior art] Fig. 6 shows a conventional touch coordinate input device (Japanese Patent Laid-Open No. 60-18
1913) is shown.

A terminal L%R is provided at both ends of the resistor 1110, and this terminal is connected to the input terminal of the voltage follower 12 constituted by an operational amplifier, and the terminal R is connected to the output terminal of the voltage follower 12. , terminal R and terminal R are at the same potential. When a finger +4 of a human body is brought into contact with the pointing point P on the resistor @10, a current flows through the resistive film IO from the terminals and terminals R to the pointing point P side, and both currents flow through the fingers 1 and 4. Further, the current flowing from the terminal R to the indicated point P does not flow from the indicated point P to the terminal side because the human power impedance of the voltage follower 12 can be regarded as infinite.

Therefore, the voltage between LP is equal to the voltage between RP, and the impedance seen from the terminal side is the resistance film between RP! Equivalent to 0 removed.

22, an insulating film is attached to the resistive film lO, and the combined impedance of the human body and this insulating film (herein simply referred to as the impedance or capacitance of the indicator (including the human body)) is the capacity lIC- It can be approximated by Also,
Resistive film! The resistance value of O is sufficiently small compared to this capacitance Cm.

Therefore, the impedance seen from the terminal side is the capacitance C
x, and calculating this capacitance Cx under the above conditions,
Cx-Cmx+C5(R+-x/(Rx+R+-x))
・(1) becomes.

Here, Rx is resistance! ! 10, R+-x is the resistance value between RP of resistor 110, and Cox is the stray capacitance l between the terminal and ground.

The terminal is connected to the input terminal of the variable oscillator 'a16, and the variable oscillator! 6 is the capacity of the capacitor connected to this input terminal! Outputs a pulse with a frequency inversely proportional to the l value.

Therefore, by counting the number N of pulses output from the variable oscillator 16 within a certain period of time, the volume and weight Cx can be determined using the following formula (%). Also, floating volume 1
Since 1cax is equal to c=0, that is, the capacitance ICx before the finger I4 contacts the resistive film IO, this can also be measured.

Next, the input terminal of the voltage follower 12 is connected to the terminal R, the output terminal of the voltage follower 12 is connected to the terminal R, the input terminal of the variable oscillator 16 is connected to the terminal R, and the output terminal of the voltage follower 12 is connected to the terminal R.
If we measure the capacitance Cl-8 seen from the side, this C+-x is: C+-x= C5l-x+ CJRx/(Rx+
R+-x)) (3)

Here, C, λ is the stray capacitance 1 between the terminal R and the ground.

Set the position coordinates of L grain to 0. If the position coordinate of point Ft is normalized to 1, the position coordinate X of indicated point P is expressed by the following equation.

X == Rl-X/(RX+RI-X)
-(4) From the above formulas (1), (3), and (4), J,
, Rl-X and CB to find the positional dust [X, the following equation is obtained.

X ” (CI-x-Cs+-x)/((c x
Cax)+ (CI-X-C111-11))
, (5) According to this equation (5), the position coordinate x of the indicated point P can be determined without directly measuring the human body capacity.

A touch coordinate input device using such a resistor *10 is
It is possible to detect position coordinates with higher accuracy than when position sensors are arranged in a matrix.

[Problem to be solved by the invention]

However, when the human body capacity is relatively large, the detection accuracy becomes low.

An object of the present invention is to provide a touch coordinate input device that can detect position coordinates with high accuracy even if the capacity of a pointer is relatively large.

[Means for Solving the Problems] In order to achieve this object, a touch coordinate input device according to the present invention includes the following components.

(2) A touch panel in which a resistive film is arranged on a substrate and one or more pairs of opposing terminals are provided on the resistive film.

(2) An impedance measuring means for keeping both terminals of each pair at the same potential and measuring the impedance seen from one terminal and the impedance seen from the other terminal.

(2) Touch position coordinate calculation means for calculating the coordinates of the touch position using the impedance measured before and during contact of the pointer with the touch panel.

■ Obtain the impedance of the pointer from the measured impedance, and if the impedance of the pointer is greater than a predetermined value, calculate the contact position coordinates according to the impedance of the pointer and the calculated contact position coordinates. Position coordinate correction means for correction.

[Operation] As a result of experiments, it was found that when the pointer capacitance C3 is relatively large, as shown in FIG. 5, the coordinate detection error increases as the capacitance ffi Cs increases. Also,
It has been found that this error increases as the touch position moves away from the center point of the touch panel.

It has been found through theoretical analysis that such coordinate detection errors are based on the fact that when deriving the above equations (1) and (3), the impedance of the pointer is approximated only by the capacitance Cm, and the resistance component is ignored.

In the present invention, since the above-mentioned position coordinate correction means is provided,
Even if the capacity of the pointer is relatively large, position coordinates can be detected with high accuracy.

[Example] An embodiment of the present invention will be described based on the drawings.

FIG. 1 shows the main part configuration of a touch coordinate input device.

The touch panel 18 has a transparent resistive film coated on a rectangular glass S plate, a SiOx film further coated thereon, and terminals L is R+ at opposing positions on the left and right ends of the transparent resistive film.
(1; the same applies below 1 to ns) are formed in pairs,
Terminals Ut and D are located at opposite positions on the upper and lower ends of the transparent resistive film.
t (i=l-m, the same applies hereinafter) are formed in pairs.

Terminals Ls, Rt, tJ, and Dt are each connected to one end of each switch element constituting analog switch arrays 20, 22, 24, and 26.

The other end of each switch element of analog switch arrays 20 and 24 is commonly connected to signal line SI, and the other end of each switch element of analog switch arrays 22 and 26 is commonly connected to signal line S.

In the following, for example, when the switch elements of the analog switch array 20.22 connected to the terminals Li and Ri are closed, the terminal pair (L+, R+) is said to be in a connected state.

The signal lines S1 and S are connected to the signal lines S3 and S, respectively, via a changeover switch 28 having two interlocking switch elements.
4 or signal line S. This signal line S
, are connected to the input terminals of the voltage follower 12 and the variable oscillator 16, and the signal line S.

is connected to the output terminal of the voltage follower 12.

The output pulses of the variable oscillator 16 pass through the AND gate 38 and are counted by the counter 40 when the AND gate 38 is opened by the output pulses of the monomultivibrator 36 . This mono multivibrator 36 is
As shown in FIG. 4, it is triggered at the falling edge of the trigger pulse from the timing generator 42. Further, after the count value of the counter 40 is read by the microcomputer 44 at the rising edge of this trigger pulse, the count value of the counter 40 is cleared by the microcomputer 44.

Timing generator 42 also provides select signals to analog switch arrays 20 and 22 via signal line Ss, and select signals to analog switch arrays 24 and 22 via signal line S and inverters 32 and 34, respectively. and signal line S.

A switch element driving pulse is supplied to the analog switch arrays 20 to 26 via the analog switch arrays 20 to 26. In these analog switch arrays 20 to 24, when the select signal is at a high level, any one of the switch elements is sequentially closed by a switch element drive pulse.

That is, the switch element is scanned by the switch element drive pulse. Therefore, the terminal pair (L□, R1), (
Either Ul or Di) becomes connected sequentially.

The selector switch 28 is switched twice by a switching pulse supplied from the timing generator 42 via the signal line S, as shown in FIG. 3, when the select signal is at the low level and when the select signal is at the low level. For each switching, the selected analog switch array 20, 22 or analog switch array 24 . ．． 26 switch elements are driven by switch element drive pulses! scanned. Fourth
As shown in the figure, a trigger pulse is output immediately after the switch element drive pulse.

These select signals, switch element drive pulses, and switching pulses are also supplied to the microcomputer 44, and the microcomputer 44 measures which terminal pair of the touch panel 18 is in a connected state and the impedance seen from which terminal side. Know what you are doing.

Next, referring to the timing chart shown in Figure 3.4,
The processing procedure of the microcomputer 44 shown in FIG. 2 will be explained.

In the initial state, the select signal is at a high level and the analog switch 1 noise 20, 22 is selected, the switching pulse is at a low level and the selector switch 28 is in the state shown in Fig. 1, and the terminal pair (L, , R , ) is assumed to be connected.

(100) Terminal pair (LI
R1) becomes connected, and the count value of the counter 40 is cleared at the rising edge of the trigger pulse immediately after that, and at the falling edge of this trigger pulse, the mono multivibrator 36 is triggered and its output becomes high level, and the anti-game) - 38 is opened and pulses from variable oscillator 16 are counted by counter 40; Anne 1 after a certain period of time
The gate 38 is closed, and the count value N of the counter 40 at this time is proportional to the reciprocal of the impedance seen from the terminal L1 side. Terminal pair (shi2, R1) with the next switch drive pulse
is connected, the count VLN of the counter 40 is read into the register at the rising edge of the trigger pulse immediately after that, the counter 40 is cleared at the falling edge of this trigger pulse, and then the count VLN stored in the register is read from the count value N stored in the register. , the impedance seen from the terminal LI side is calculated using the above equation (2) and written into the memory.

Similarly, the terminals 2, L, . . . are connected, and the impedance seen from the 1 side is measured and stored.

Next, the changeover switch 28 is changed over by the changeover pulse, and the impedance seen from the terminals R4 to R, , ff1l+ is measured and stored in the same manner as described above.

Next, the select signal becomes low level, the analog switch array 24, 26 is selected, and the innovative dance seen from the terminals U, .about.U1, D, .about.D is measured and stored.

(102) If all of the stored impedances are below a certain value, it is determined that r>14 has not been touched on the touch panel 18, and the process returns to step 100.

When the finger 14 touches the touch panel 18, one of the stored impedances becomes a certain value or more,
It is determined that there is a touch, and (104) the above step 100 is performed.
In the same manner as above, the impedance of each terminal 4, Ri, U+, and Dt as seen from the side is measured and stored.

(106) Next, the coordinates (X, Y) of the indicated position are calculated using the impedances stored before and during the touch and the above equation (5).

(108) Next, the human body capacitance CB is determined from the impedance during the touch measured in step 104 and stored in the memory.

Human body capacity CB is calculated from the above formula (ri, (3), (4), C5=
(Cx C5x)+(C+-x C5t-x)
・(6) becomes. This right-hand side is equal to the denominator of equation (5).

If the human body capacitance CB is a relatively large predetermined value 00 or more, (110) Correct the coordinate value (XSY) using the following equation.

X”X+Kx(PcxX)/Pxo”
(7)Y”Y +Ky(Pcy Y)/Pyo
・ (8) Here, Pcx is the median value of the X coordinate, Pxo is xFM, and the maximum value of a (= 2 P C ri, PC
Y is the median value of the Y coordinate, PYO is the maximum value of Y [1 = standard (= 2 p CY), and if the maximum value is normalized to 1.0, the median value is 0.5 .

K,,KY is a function of human body capacity Cs, for example, Kx=
A+(C+s Co)+At(Co Co)+A
n (Ca Co) ' ・ ・(
9) allows accurate approximation. Coefficient A + , A
t, ·Afi are determined using experimental values. The same applies to KY.

If Cn<Co, the above correction is not performed.

(112) Next, the coordinate value (X
, Y).

[Effects of the Invention] As explained above, according to the touch coordinate input device according to the present invention, one or more pairs of terminals facing the resistive film provided on the touch panel are provided, and both terminals of each pair are connected to the same potential. Measure the impedance seen from one of the terminals and the impedance seen from the other terminal, and calculate the impedance of the pointer from the measured impedance, and if the impedance of the pointer is greater than a predetermined value, Since the contact position coordinates are corrected according to the impedance of the pointing object and the calculated contact position coordinates, an excellent effect is achieved in that the position coordinates can be detected with high accuracy even if the capacity of the object is relatively large.

[Brief explanation of the drawing]

1 to 4 relate to one embodiment of the present invention, in which FIG. 1 is a circuit diagram showing the main configuration of a touch coordinate human-powered device, FIG. 2 is a flowchart showing the processing procedure of the microcomputer 44, and FIG. FIG. 4 is a timing chart of the circuit shown in FIG. FIG. 5 is a diagram for explaining the operation of the present invention. FIG. 6 is a circuit diagram showing the principle structure of a conventional touch coordinate input device. In the figure, 10 is a resistive film 12 is a voltage follower 16 is a variable oscillator 18 is a touch panel 20 to 26 is an analog switch array 28 is a changeover switch 32.34 is an inverter 36 is a mono-multi-by-break 38 is an AND gate 40 is a counter 42 is a timing Generator 44 is a microcomputer touch coordinate input device Fig. 1 Processing procedure of microcomputer 44 Fig. 2 Coordinate detection error when changing the capacity of the pointer for a specific indicated position Fig. 5 Conventional touch coordinate input Principle configuration of the device

Claims (1)

[Claims] A touch panel (18) in which a resistive film is arranged on a substrate, and one or more pairs of opposing terminals are provided on the resistive film, and both terminals of each pair are kept at the same potential, and one of the terminals is impedance measuring means (12, 16, 20 to 44) for measuring the impedance seen from the terminal and the impedance seen from the other terminal; a touch position coordinate calculation means (44, 106) for calculating the coordinates of the touch position using the touch coordinate input device; Touch coordinate input characterized by comprising: position coordinate correction means (44, 110) that corrects the contact position coordinates according to the impedance of the pointer and the calculated contact position coordinates when the contact position coordinates are greater than or equal to the value. Device.