JPH03271917A - Touch coordinate input device - Google Patents

Abstract

PURPOSE:To evaluate the change of an impedance measurement condition by providing a two-dimensional touch panel where terminals are provided along one pair of first and second sides facing each other and the other pair of third and fourth sides facing each other and repeatedly measuring impedances viewed from terminals of first, second, third, fourth, second, first, fourth, and third sides in this order. CONSTITUTION:A touch panel 1 is provided with terminals along one pair of first and second sides facing each other and the other pair of third and fourth sides facing each other, and impedances CL1, CR1, CU1, CD1, CR2, CL2, CD2 and CU2 viewed from terminals of first, second, third, fourth, second, first, fourth, and third sides are repeatedly measured in this order by an impedance measuring means 2. A measurement abnormality discriminating means 3 discriminates measurement abnormality if an absolute value Z of the difference between the sum of measured impedances viewed from terminals of first and second sides and that viewed from terminals of third and fourth sides is larger than a set value. Thus, the change of the impedance measurement condition is evaluated.

Description

[Detailed description of the invention] 【table of contents】

Industrial applications Conventional technology (Figures 6 to 8) Problems that the invention aims to solve Means to solve the problem (Figure 1) action Example (Figures 2 to 5) Effect of the invention

【overview】

The purpose of the touch coordinate input device, which measures the impedance seen from the terminals on each side of the touch panel to determine the coordinates of the contact position of an object on the touch panel, is to enable accurate evaluation of changes in impedance measurement conditions. A two-dimensional touch panel in which terminals are provided along a pair of first sides and second sides and another pair of third and fourth sides opposite to each other, and impedance as seen from the terminals on each side of the touch panel. an impedance measuring means for measuring the
If the absolute value of the difference between the sum of the measured impedances seen from the terminals on the first side and the second side and the sum of the measured impedances seen from the terminals on the third side and fourth side is greater than or equal to the set value. For example, a touch coordinate system comprising: a measurement abnormality determining means for determining a measurement abnormality; and a contact position coordinate calculation means for calculating and outputting a contact position coordinate of a pointer on the touch panel using the measurement impedance when there is no measurement abnormality. In the input device, the impedance measuring means measures the impedance seen from the terminals on the first side, second side, third side, fourth side, second side, first side, fourth side, and third side. It is configured to take repeated measurements in sequence.

[Industrial application field]

The present invention relates to a touch coordinate input device that measures impedance seen from terminals on each side of a touch panel to determine the coordinates of a touch position on a touch panel of a pointer.

[Conventional technology]

Figure 8 shows a conventional touch coordinate input device (Japanese Patent Laid-Open No. 60-18
1913) is shown. The one-dimensional touch panel 10 is constructed by depositing a transparent resistive film 10a on a glass substrate, and further depositing an SiO2 film on the glass substrate. Both ends of this resistive film 10a have terminals, R
A terminal R is connected to an input terminal of a voltage follower 12 constituted by an operational amplifier, and a terminal R is connected to an output terminal of the voltage follower 12. therefore,
Terminal R and terminal R are at the same potential. When the finger 14 of the human body is brought into contact with the pointing point P on the touch nozzle lO, a current flows from the terminal R to the resistor W110a toward the pointing point P, and both currents flow through the finger 14. At this time, the voltage across LP is equal to the voltage across RP. Also, since the input impedance of the voltage follower 12 can be considered infinite,
The current that flows from the terminal R to the pointing point P does not flow from the pointing point P to the terminal side, and the impedance seen from the terminal side is R.
The resistance between P II 10 a is equal to the ablation. Here, resistance II! The resistance value of 10 a is the human body capacitance C6
Assuming that the impedance of the human body is sufficiently small compared to the capacitance C1,l, the impedance of the human body can be approximated by the capacitance C1,l. Therefore, the impedance seen from the terminal is approximately capacitance, and when calculating this capacitance CL under the above conditions, CL = CIL + CII (R1-X / (RX
+RI−X) )(1). Here, R11: Resistance value R1-X between LP of resistor W10a:
Resistance value CIL between RP of the resistive film 10a: Stray capacitance between the terminal and ground. The terminal is connected to the input terminal of the variable oscillator 16,
The variable oscillator 16 outputs a pulse whose frequency is inversely proportional to the capacitance value of the capacitor connected to this input terminal. Therefore, by counting the number N of pulses output from the variable oscillator 16 within a certain period of time, the capacitance C-CL can be determined using the following equation (2). In addition, the stray capacitance CBL is Cl1=0, that is, touch)<Nel1
Since the capacitance when the finger 14 is not in contact with 0 (hereinafter referred to as the base capacitance as seen from the terminal) is equal to CL,
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 C3 seen from
R+-w) )... (3) It becomes. Here, C□ is the stray capacitance between the terminal R and the ground, that is, the base capacitance seen from the terminal R. If the positional coordinates of the L point are normalized to 0 and the positional coordinates of the R point to 1, the position aX of the designated point P is expressed by the following equation. X:=R1-1/ (RX +R+-x) ・
・(4) From the above formulas (1), (3), and (4), R1,
By eliminating R1-X and C, and determining the position coordinate X, the following equation is obtained. X = (Cm - Cam) / (
(Ct CIL) + (c, -CH))
(5) According to this equation (5), the position aX of the indicated point P can be determined without directly measuring the human body capacity. In the case of a two-dimensional touch panel, the X coordinate is determined by the above formula (5), and the Y coordinate is determined by connecting the pair of terminals at both ends in the Y direction to the US
Assuming D, it can be obtained by the following formula in the same manner as above. y= (cu-Cmu)/((c,-Cu+)+(c
(6) Here, Cio: Base capacitance C seen from terminal U,: Capacitance C1 seen from terminal U,: Base capacitance seen from terminal C1: Capacitance seen from terminal R be. The above equations (5) and (6) hold true when each capacitance is measured at the same time, in other words, under the same measurement conditions. Among these capacities, the base capacity is usually a constant value,
Initial measurement is taken immediately after power is turned on. Therefore, in order to accurately measure the contact position coordinates, C, must be the same when measuring the capacitance seen from the terminal R and when measuring the capacitance seen from the terminal R, that is, the state of contact of the finger 14 with the touch panel 10 must be the same. Must be the same. Whether this condition is satisfied can be checked as follows. That is, regarding the X-axis, from the above equations (1) and (3), the following equation holds true under the same measurement conditions. CL + C* = CIL + Cas + C
--(T) Similarly, the following equation holds regarding the Y axis. Go +Co =C5u+(,so+cx ・
−・(8) From equations (7) and (8), the following equation holds true. (CL + (g) - (cu + C++) = (CIL
+C□)-(cau+cm) (9) The right side of this equation is almost zero. Assuming that the absolute value of the left side of this equation is 2, the value of Z will deviate from zero if the state of contact of the finger 14 with the touch panel differs when measuring the capacitance seen from each terminal. Therefore, if the value of Z is a certain value or more, it can be determined that the measurement conditions are not constant and the measurement error of the contact position coordinate is large, and this position coordinate is excluded. On the other hand, in order to improve the measurement accuracy of position coordinates, it is necessary to measure the capacitance multiple times and use the average value for coordinate calculation. However, if the capacitance seen from one terminal is continuously measured multiple times, the measurement time becomes longer, the measurement conditions change, and the measurement error increases. Therefore, the capacitances seen from terminals R, U, and D are measured at a high speed of several milliseconds to calculate the position coordinates, and this is repeated multiple times, for example, 4 times, and the average value is output as the position coordinates. Was. Here, since the variable oscillator 16 performs feedback control using a PLL circuit, it usually takes several milliseconds until the measured value becomes stable after the start of capacitance measurement. Therefore, the measured capacitance (the reciprocal of the output frequency of the variable oscillator 16) is determined by the measurement point PA (u, u) on the touch panel 18 shown in FIG.
, Pa (1-u. u), Pc (u, 1 u), Pa (u,
1 u), they change as shown in FIGS. 7(A) to 7(D) mainly due to the variable oscillator 16. Since the actual measured capacitance is obtained by counting the output pulses of the variable oscillator 16 for a certain period of time, it is proportional to the area between this capacitance curve and the horizontal axis. Hereinafter, this proportionality constant will be assumed to be 1 to simplify the explanation. In the figure, the hatched part rising to the right is
This is a region where the capacitance is larger than the actual capacity, and the hatched portion downward to the right is a region where the capacitance is smaller than the actual capacitance. The area of each of these regions is almost the same, and this is defined as Δ (.Δ is a decreasing function of U in the range O<u≦0.5,
When u=0°5, Δ=0.

[Problem to be solved by the invention]

However, even though the measurement conditions (contact state) were the same, the value of the measurement condition change amount Z varied relatively greatly depending on the contact position coordinates. For example, Fig. 7 (A) to (D
), when the measurement conditions are the same, what should be Z=0 becomes Z-0, Z=2Δ, Z=2Δ, and Z-0, respectively. For this reason, the reliability of the finger mZ itself for evaluating the reliability of measured values is not sufficient, and items with relatively large measurement errors are not excluded, or conversely, items with relatively small measurement errors are also excluded. There was a problem. This problem is particularly acute when scanning capacitance measurements at high speeds. In view of these problems, an object of the present invention is to provide a touch coordinate input device that can correctly evaluate changes in impedance measurement conditions. Means for Solving 1 Problem The present inventors discovered that the above-mentioned conventional problems are related to the order of impedance measurement of each terminal, and solved the problem by devising this measurement order. FIG. 1 shows the basic configuration of the present invention. In the figure, 1 is a touch panel, and terminals are provided along a pair of opposing first and second sides and another pair of opposing third and fourth sides. 2 is an impedance measuring means, the first side, the second side,
Impedance CLIC□, CUI5CD seen from the terminals on the 3rd side, 4th side, 2nd side, 1st side, 4th side, and 3rd side
I, Cヮ2, CLa, CD2 and CL12 are repeatedly measured in this order. Here, the contact position coordinates of the pointer on the touch panel 1 are:
It can also be determined using a quantity that has a one-to-one relationship with impedance, such as the reciprocal of impedance. It also includes those who are related. 3 is a measurement abnormality determination means, which determines the absolute value Z of the difference between the sum of the measured impedances seen from the terminals on the first side and the second side and the sum of the measured impedances seen from the terminals on the third side and the fourth side.
However, if it is greater than or equal to the set value, it is determined that the measurement is abnormal. Reference numeral 4 denotes a contact position coordinate calculating means, which calculates and outputs the contact position coordinates of the pointer on the touch panel l using the measured impedance when there is no measurement abnormality. 1 action] Various specific definitions of Z can be considered, but for example, Z = I Ct++C□-C, 1-C□I (i is 1
or 2), then Figure 5<A)~
In the case of FIGS. 7(A) to (D) corresponding to (D>), under the same measurement conditions, what should be Z = 0 is
= the same as Δ (conventionally, as described above, <2=0, Z=2Δ, Z=
2Δ, Z=O (!: relatively large change). Therefore, the error in the measurement condition change amount Z becomes less dependent on the contact position. Also, z= (CL, +CL2)/2+ (C□0C1)/
2- (Cut+Cuz) /2- (Co++Co1
) / 2, in the case of Figures 7 (A) to (D), under the same measurement conditions, Z = 0, Z = 0.5Δ, Z - 0, Z = respectively. 0, Z-0°5Δ. Therefore, the error in measurement condition variation 2 is smaller than the conventional 1
/4, making it less dependent on the contact position. Therefore, changes in impedance measurement conditions can be evaluated correctly. In other words, the reliability of the index Z itself for evaluating the reliability of measured values becomes sufficient, and it becomes possible to exclude only those with relatively large actual measurement errors.

【Example】

Hereinafter, one embodiment of the present invention will be described based on the drawings. FIG. 2 shows the main part configuration of the touch coordinate input device. The two-dimensional touch panel 18 has a transparent resistive film deposited on a rectangular glass substrate as a transparent insulating substrate, and an S + Os film as a transparent insulating film, and the left and right ends of this transparent resistive film are At opposing positions, that is, along the left and right sides of the touch panel 18, the terminals L+ -Rt
(i=1-n, hereinafter simply referred to as R) are formed in pairs at opposing positions on the upper and lower ends of the transparent resistive film, that is, along the pair of upper and lower sides of the touch panel 18. , terminal U,, Dt (i=1-m, hereinafter simply referred to as terminal U
It is called 1D. ) are arranged in pairs. Terminals R, U, and D are each connected to one end of each switch element constituting the analog switch array 2 (122, 24, and 26).
and 24 are commonly connected to the signal line S1, and the other ends of the respective switch elements of the analog switch arrays 22 and 26 are commonly connected to the signal line S. The plurality of switch elements constituting each analog switch array 20 to 26 are turned on and off simultaneously for each analog switch. The signal lines S1 and Ss are connected to the signal lines S= and S, respectively, via a changeover switch 28 having two interlocking switch elements.
a or signal lines S- and Ss. This signal line S3 is connected to the input terminal of the voltage follower 12 and the variable oscillator 16, and the signal IS, lt voltage follower 12
is connected to the output terminal of The signal line S is also a terminal LSR. It is grounded via a changeover switch 35 and a capacitor C for making simulated contact with U and D. The output pulses from variable oscillator 16 are passed through AND gate 38 and counted by counter 40 when AND gate 38 is opened by a measurement pulse as shown in FIG. 3(C) from timing generator 42. Ru. At the falling edge of this measuring pulse, the microcomputer 44 reads the counted value N of the counter 40, and immediately, that is, before the rising edge of the next measuring pulse, this counted value N is cleared to zero by the microcombi coater 44. Timing generator 42 also provides a select signal as shown in FIG. A select signal is supplied to switch arrays 24 and 26. Each switch element of these analog switch arrays 20 to 24 closes when the select signal becomes high level, and opens when the select signal becomes low level. The changeover switch 28 is switched by a changeover pulse supplied from the timing generator 42 via the signal line S, respectively, when the select signal is at a high level or a low level, as shown in FIG. By this combination of select signal and switching pulse, the terminals, RSU, D, R%LSD
, U will be measured in this order. These select signals, switching pulses, and measurement pulses are also supplied to the microcomputer 44, and the microcomputer 44 determines which terminal pair of the touch panel 18 is connected and which terminal is measuring the capacitance. , and the start and end of each impedance measurement. On the right, FIG. 3 shows the case where there are two measurement pulses for each terminal L%R and U%D selected. This means that the impedance seen from each terminal is measured twice in succession, and the average value is taken as the measured impedance. Although the measurement pulse width is constant, the number of measurement pulses for each selection of terminals LXR, U, and D can be set and changed by a configuration not shown. Next, the processing procedure of the microcomputer 44 shown in FIG. 2 will be explained. When the touch coordinate input device is powered on, it is estimated that the finger 14 is not in contact with the touch panel 18 immediately after the power is turned on (100), so the capacitance seen from each terminal L1R1U and D is measured and these are calculated as the base capacitance Cat. s C**, C
Store it as ru and CSa. Next switch 35
Close the terminal, R. For each case in which simulated contact is made sequentially on U and D, the capacitance (simulated contact capacitance) seen from the terminals R, Ll, and D is similarly measured. Then, terminals R and U are determined using the base capacitance and the simulated contact capacitance. Calculate the position coordinates of D. According to the first approximation formula, the position coordinates of terminals R and U are 0, and the position coordinates of terminals R and D are 1, but in reality they deviate from these values. Therefore, in order to make these become 0 and l, respectively,
Memorize this amount of deviation and wipe it. The contact position coordinates determined later are corrected using this amount of deviation. <102) Next, measure the containers CLl% Cm+, CU+ and C□ viewed from the terminals R%U and D in this order. (104) Furthermore, capacitances Cat, Cl2, C□, and Cl1ff viewed from terminals R, L, D, and U in this order are measured. (106) Find the average value of the capacitances measured in steps 102 and 104 above for each terminal. That is, CL = (CLl + CIJ) / 2C, = (
Find C□10Cm2)/2 Cu = (Cu++Cuz)/2 C, = (C++10Ct+z)/2. (108) Next, it is determined whether the finger 14 has touched the touch panel 18. That is, each measured capacitance obtained in step 106 and each base capacitance CB obtained in step 100
is compared with a reference value obtained by adding a constant value ΔC to the reference value, and if any of the measured capacitances is greater than or equal to the corresponding reference value, it is determined that there is contact, and if not, it is determined that there is no contact. If it is determined that there is no contact, the process returns to step 102 above. If it is determined that there is contact, <110) The above measurement condition change amount Z = CLICI CLI CI is determined. Figures 5 (A) to (D) are Figures 7 (A) to (D), respectively.
When the measurement conditions are the same, what should be 22 holes becomes Z=0.5Δ, Z=0, Z=0, and Z, respectively.
=0.5Δ. As a result, the error in the measurement condition change amount Z is reduced to 174 compared to the conventional method, and it becomes less dependent on the contact position. Therefore, the reliability of the index Z itself for evaluating the reliability of measured values becomes sufficient, and it becomes possible to exclude only those with relatively large actual measurement errors. (112) If the value of Z is greater than or equal to the set value d, it is determined that calculating the position coordinates has a large error and cannot be used,
Return to step 102 above. If Z<d, (114) the capacity obtained in step 106 and step 10
Using the base capacitance measured at 0, the above equations (5) and (6
), the contact position coordinates -(X, Y) are calculated, and this is corrected using the amount of deviation of the terminal position coordinates obtained in step 100. After repeating the processing of steps 102 to 114 a plurality of times, for example twice, the average value of the contact position coordinates is calculated and output. Note that the present invention includes various other modifications. For example, in the above embodiment, it has been explained that the capacitance seen from each terminal is measured based on an approximation formula, but to be more precise, since a resistance component is also included, impedance will be measured for boat fishing. In addition, in the above embodiment, the terminals R, U, D, RIL, D
The case where the measurement condition change amount Z is calculated using the capacitance seen from the and D
Use only the capacitances seen in this order from , or use terminals R, LS
A configuration may be adopted in which only the capacities seen in this order from D and U are used. In this case, the error in the measurement condition variation Z is the seventh
In the case of figures (A) to (D), under the same measurement conditions,
What should be Z=0 becomes the same as Z-Δ (conventionally, as described above, it changes relatively greatly, such as z-0, Z=2Δ, Z=2Δ, and z=0). Therefore, the error in the measurement condition change amount Z becomes less dependent on the contact position. [Effects of the Invention] As explained above, in the touch coordinate input device according to the present invention, the order in which the impedance is measured as seen from the terminals on each side of the touch panel is devised, so that the error in the amount of change in measurement conditions does not depend much on the contact position. Therefore, the reliability of the index itself is sufficient for evaluating the reliability of the measured values, and only those with relatively large measurement errors are excluded. This has the excellent effect of making it possible to perform the following functions, and greatly contributes to increasing the scanning speed of the interference measurement viewed from each terminal and improving the reliability of the output coordinate values.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the basic configuration of a touch coordinate input device according to the present invention. 2 to 5 relate to an embodiment of the present invention, FIG. 312 is a main circuit diagram of a touch coordinate input device, FIG. 3 is a timing chart of the circuit shown in FIG. 2, and FIG. 4 is a microcomputer. 5 (A) to 5 (D) are flowcharts showing the processing procedure of 44, and Fig. 5 (A) to (D) mainly show the variation of the measured capacitance seen from the terminals RlU and D when the touch points on the touch panel are P and -P, respectively. It is a graph showing changes caused by an oscillator. 6 to 8 relate to the explanation of the conventional example, and FIG. 6 is a diagram showing the contact points PA-PD on the touch panel, and FIGS. When the contact point is P a -F D, the terminal R. A graph showing changes in the measured capacitance seen from U and D mainly caused by the variable oscillator. FIG. 8 is a circuit diagram showing the principle configuration of the touch coordinate input device. In the figure, 10.18 is the voltage holo of the touch panel 12, 20-26 is the analog switch array, contact position coordinates, principle configuration of the invention, Fig. 1, 2, touch coordinate input device, Fig. 2, Fig. 4, measurement points on the touch panel, Fig. 6, 10. :Principle configuration of touch panel touch coordinate input device (prior art) Fig. 8

Claims (1)

[Claims] A two-dimensional touch panel (1) in which terminals are provided along a pair of opposing first sides and second sides and another pair of opposing third and fourth sides; impedance measuring means (2) for measuring the impedance seen from the terminals on each side of the touch panel; Measurement abnormality determination means (3) that determines that the measurement is abnormal if the absolute value of the difference between the sum of the measured impedances and the sum of the measured impedances seen from the terminal is equal to or greater than a set value; A touch coordinate input device comprising: a contact position coordinate calculation means (4) for calculating and outputting the contact position coordinates of an object on the touch panel; @ Characterized by repeatedly measuring the impedance seen from the terminals on the third side, the fourth side, the second side, the first side, the fourth side, and the third side in this order.