JPS60181913A - Coordinate detecting device - Google Patents

Abstract

PURPOSE:To detect exactly a coordinate by measuring an equivalent impedance seen from both ends of a resistance film on a time division mode and calculating the weighted average of measurement of several time portions with respect to a result of its measurement. CONSTITUTION:Each side of a touch panel 22 which has formed a transparent resistance film on a glass substrate is connected to analog switch arrays 23-26 by each switch line AX, AY, and inputted to an analog switch 27 by connecting lines L1, L2. Also, as for the arrays 23, 24 and the analog switch 27, switch control lines C1, C2 from a control device 30 are connected, a capacity terminal of a capacity variable digital oscillator 29 is connected to the analog switch 27, and its output terminal is connected to the control device 30. In this way, an oscillation output pulse corresponding to an equivalent capacity value by a finger touch 32 from the oscillator 29 is measured and stored by the control device 30, the weighted average is derived by repeating it, and a coordinate is detected with high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The present invention relates to a coordinate detection device, and particularly includes a substrate provided with a resistive film and an impedance added thereto, and detects coordinate values indicated by the impedance. The present invention relates to a coordinate detection device for detecting coordinates.

(2) Technology background Due to developments in office automation, etc.

2. Description of the Related Art It is common practice to input and process figures, characters, etc. into computers. Keyboards are a typical input device for drawings, letters, etc., but there are also coordinate inputs in which drawings, letters, etc. are input by specifying a position on a specific board with a finger or pen, and inputting the coordinates. There is a device.

(3) Conventional technology and problems One method of the above-mentioned coordinate input device is as follows.

There is a method in which a large number of sensors are arranged in a grid on a board, and the coordinates are determined by a signal from a sensor at a particular position by pointing with a finger or a pen. However, in this type of system, the accuracy of inputting coordinates is determined by the density of the sensors arranged, so there is a problem that it is difficult to input coordinates with high accuracy.

Another method of coordinate input device uses a resistive film as the input board, and connects the impedance connection point (
There is a method in which a current is passed through a contact point (such as a finger or a pen) and the coordinates of the connection point are determined from the current ratio. The principle of such a system is shown in FIG. For the left terminal 2 of the resistive film l, which is made of uniform material.

Terminal 5 on one side of power supply 8 is connected via current measuring device 9 . A terminal 5 on one side of a power source 8 is also connected to the right terminal 3 of the resistive film 1 via a current measuring device 10 . The other terminal of power supply 8 is grounded to earth 7 . The output of the current measuring device 9 is connected to an AD converter 11, and the output of the current measuring device 10 is connected to an AD converter 12. AD converters 11 and 12
The output of is connected to the control device 13. Then, an arbitrary position 4 on the resistive film 1 is indicated by an impedance 7 such as a finger or a pointing pen whose one side is grounded to the earth 7 . As a result, the coordinate X (0≦X≦1) of any position 4 on the resistive film 1 where the left end coordinate is 0 and the right end coordinate is 1
) is indicated.

In this state, the resistance value between terminals 2 and 4 is R8, and the resistance value between terminals 3 and 4 is R1-8. Also, the current flowing from terminal 2 to 4 is IX, and the current flowing from terminal 3 to 4 is T
Let it be I-X. At this time, since the resistance value of a resistive film made of a uniform material is proportional to the length of the resistor, the coordinate X of the indicated point 4 is.

X = Rx/ (Rx+R7-x) ---・(t)
given by. Also, since the voltage drop due to the resistance value 'Rx and the voltage drop due to the resistance value R1-8 are equal.

Rx1x = R,, I,

X-11-X/ (I x + 1 +-x)...
・(3) becomes. In other words, the coordinates X of the indicated point 4 are
The current lx flowing between terminals 3 and 4, and the current flowing between terminals 3 and 4 ■2. If you understand it, you can understand it. Therefore, these currents 8 and I +-8 are measured by the current measuring device 9 and the
The coordinate X can be determined as a digital value by detecting it as a voltage value, converting it into a digital value by the AD converters 11 and 12, and then calculating the equation (3) using the control device 13.

According to such a conventional method, the coordinate X of any position on the resistive film 1 (the left end coordinate is 0, the right end coordinate is 1, and a value between them) can be determined as a digital value. However, a current measuring device 9 to measure the current and an operational amplifier to convert the current to voltage as lO are required, and an AD converter 11 with high quantization accuracy and an AD converter 11 with high quantization accuracy and 12 is required, which makes the circuit complicated and increases the cost.

As a technique for solving the above-mentioned problems, there is a "coordinate detection device" for which an application has already been filed. As shown in Figure 2 (the detailed principle will be described later), by adding a buffer circuit to both ends of the resistive film, the equivalent impedance seen from one end of the resistive film and the coordinates of the indicated point can be adjusted to a specific value. By utilizing the functional relationship, the value of the equivalent impedance is detected and the coordinates of the indicated point are detected. According to this method, highly accurate coordinate detection can be performed with a simple circuit configuration. However, although this method is very effective when the value of impedance for specifying coordinates is constant in advance, coordinates cannot be detected when the impedance is uncertain.

For example, when finger touch is used to indicate coordinates and human body capacitance is used as impedance, there is a problem that the above method cannot be used directly because the capacitance varies depending on the person and the location (50 pF to 150 pF).

(4) Purpose of the Invention In order to eliminate the above-mentioned problems, the present invention compares the equivalent impedances seen from both ends of the resistive film based on the principle of coordinate detection from the equivalent impedances.

Furthermore, by measuring and averaging these equivalent impedances multiple times, it is possible to specify coordinates using impedances with uncertain values.At the same time, by providing individual switch means on each of the four edges of the square resistive film, An object of the present invention is to provide a coordinate detection device that enables detection of dimensional coordinates.

(5) Structure of the Invention According to the present invention, the above-mentioned object is achieved by providing a coordinate input panel having a resistive film disposed on a substrate, a coordinate indicating means for indicating one point on the resistive film, and a coordinate inputting means connected to both ends of the resistive film. a buffer circuit that maintains potentials at both ends in a constant relationship; and switching means that alternately switches and connects both ends of the resistive film and both ends of the buffer circuit.

detecting means connected to one end of the buffer circuit and detecting the impedance between the one end and the ground of the coordinate indicating means each time the switching means switches; It is an object of the present invention to provide a coordinate detecting device characterized by having a calculating means for calculating a coordinate position on the coordinate input panel designated by a coordinate specifying means.

(6) Examples of the invention Examples of the present invention will be described in detail below.

FIG. 2 is a diagram for explaining the principle of coordinate detection from equivalent impedance, which is the basis when implementing the present invention. The resistive film 1 is the same as the conventional example explained in FIG.
The coordinate X is detected. In this case as well, the coordinates of the left terminal 2 of the resistive film 1 are 0. The coordinates of the right terminal 3 are 1, and the coordinates X of the designated point 4 take a value of 0≦X≦1.

The difference between this principle and the conventional example shown in FIG. 1 is that both terminals of the resistive film 1 are not connected to a power source as in the conventional example shown in FIG. Instead, terminal 14 is connected to terminal 2 and to terminal 3 via operational amplifier 15. That is, the terminal 14 is connected to the non-inverting input of the operational amplifier 15, and the output of the operational amplifier 15 is connected to the terminal 3. Also, the output of operational amplifier 15 is
It is also connected to its own inverting input.

In the circuit configured as described above, the operational amplifier 15 serves as a buffer circuit that operates as a voltage follower. That is, the feature of the principle is that the terminals 2 and 3 of the resistive film 1 are connected by a buffer circuit. With this configuration, the potentials of terminals 2 and 3 with respect to ground 17 are made equal.

In addition, since the input impedance of the operational amplifier 15 can be considered infinite, the current at the terminal 14 does not include the current flowing from the terminal 3 to the pointing point 4.

In other words, since the current flowing from the terminal 3 to the pointing point 4 is independently supplied from the operational amplifier 15, the current flowing through the terminals 1 and 4 is the current flowing from the terminal 2 to the pointing point 4 itself.

Now, the potential of the terminals 2 and 3 with respect to the ground 17 is ■, and the potential of the pointing point 4 with respect to the ground 17 is Va.
shall be. Also, the resistance values between terminals 2 and 4 and the resistance values between terminals 3 and 4 are set to Rx and R, respectively, as in the case of Fig. 1.
Let it be +-x. and Zo between terminal 14 and ground 17
, Rx, and R1-8 are combined and equivalent impedance is assumed to be Z. This principle utilizes the fact that the coordinate X becomes a function of this impedance Z. Let's calculate this impedance Z below.

First, the current Va/Zo flowing through the impedance Zo is
Current flowing to Rx via indication point 4 (■V a ) R
Current flowing through x and +R1-X (V-Va)/R+-
It becomes the sum of x. Namely.

(V Va ) ((1/Rx)→-(1/R,
−,))−(V a / Z a ) ・・・・・・(
4). However, in reality, for the reasons mentioned above, the current V/Z flowing through one equivalent impedance Z becomes equal to the current (VVa)/Rx flowing through RX. Namely.

V/Z - (V Va) /Rx...151. If we eliminate ■ and Va from equations (4) and (5) and subtract Z.

Z=Rx +Zo ・((Rx +R+-x)/R+
-x))...(6) Here, RX + RI-X is the impedance ZO
RX so that it is sufficiently small compared to the size 1Znl.
, R, and Zo, equation (6) becomes similar.

Z#Z o ・((Rx +R+-x) /R+-x)
' ・It can be set to 171. Here, since the resistive film 1 is the same as the conventional example shown in FIG. 1, the formula (1) (conventional example) is modified.

R,, = ((1-X)/X)RX ・ ・ ・ ・(
8). Substituting equation (8) into equation (7), connecting with an equal sign and subtracting X.

X −1−(Zo/Z) (9). As can be seen from equation (9), by using the configuration shown in FIG. 2, the coordinate X of the indicated point 4 is inversely proportional to the equivalent impedance Z between the terminal 14 and the ground 17. Therefore, the value of the coordinate X can be calculated by measuring the values of the equivalent impedance Z and impedance Za and calculating the equation (9).

To summarize the principle above, both terminals of the resistive film 1 are connected by a buffer circuit using a voltage follower.

The resistance value of the resistive film 1 is set to be sufficiently smaller than the impedance Za of the pointing pen for indicating the pointing point. Then, the impedance Zo is measured in advance, and the equivalent impedance Z between the terminal 14 and the ground 17 is measured by an appropriate measuring means. By calculating equation (9) using 2 and Zo thus accumulated, the coordinate X of the indicated point 4 can be detected.

As a specific example of the impedance in the configuration shown in FIG. 2, consider a case where the impedance Zo is a capacitance. Now, let's say that the capacity is Co.

Zo −1/jωCo...'... (10). Here, j is a symbol representing a complex quantity, and ω is the angular frequency of the signal added to the capacitance. Substituting equation (lO) into equation (7) and concluding with an equal sign.

Z=1/jω[Co (R1-X/ (Rx +R1-
X) ) ]... (I1) It becomes. Therefore, the equivalent impedance Z between terminal 14 and ground 17 is also.

C= Cn [Rr-1/ (R, +R, -x))
It can be seen that the capacitance becomes isometric with a capacitance value of (12).

If we calculate X using equations (8) and (12).

X = 1-(C/Co) (13). From the above, when a capacitance is used for the impedance Zo, the equivalent impedance between the terminal 14 and the ground 17 is also a capacitance, and from these values, the coordinate X can be calculated from equation (13).

According to the above principle, by attaching a variable capacitance digital oscillator and a measuring device for its oscillation period to the terminal 14, for example, equation (13) can be calculated from the relationship of the oscillation period. At this time, the capacitance Co can be measured by bringing the indicating point 4 to the left terminal 2 of the resistive film 1.

However, the above method is very effective when the capacitance Co is constant like an indicator pen, but when the capacitance Co
In the case of using human body capacitance based on finger touch, the above method cannot be used directly because the capacitance value fluctuates during the measurement. Also, when there is stray capacitance between each of the left terminal 2 and right terminal 3 and the ground 17.

The equivalent impedance Z (equivalent capacitance C) due to them
The error in the calculation becomes impossible to ignore.

FIG. 3 shows the principle of the present invention in consideration of such a case.

First, the configuration of FIG. 3(a) is almost the same as that of FIG. 2. However, a variable capacitance digital oscillator 20 is connected to the terminal 14, and its output pulse is taken out from the terminal 21. Further, as the pointing means for the pointing point 4, a finger touch 18 having a variable capacitance value cB is used. Furthermore, stray capacitances with capacitance values C and X exist between the terminal 2 and the ground 17.

There is also a capacitance value CS I- between terminal 3 and ground 17.
Assume that there is a stray capacitance of X. Let's take a look at the equivalent capacitance CX between the terminal 14 and the ground 17 in this state.

In this case, the equivalent capacitance value between the terminal 2 and the ground 17 is given as a value in which Go is replaced by CB in equation (I2) in FIG. And stray capacitance value C11-X
can be ignored since terminal 3 is connected to the operational amplifier 15 with low impedance, and the stray capacitance value CSx is
It is connected in parallel with the equivalent capacitance value between and ground 17. Therefore, the equivalent capacitance Cx is calculated using the above equation (12).

Cx + =Cs x +Cg (R+-x/ (Rx
+R+-x) 1... (14) The operation of the variable capacitance digital oscillator 20 will be described later. Next, the connection between the operational amplifier 15 and the oscillator 20 in FIG. 3(a) is completely reversed between the terminals 2 and 3, so that the connection is as shown in FIG. 3fbl. Assuming that the connection switching at this time is performed in a very short time (about 5 msec), the stray capacitance values C, x, Cs,
It can be considered that the human body capacitance value CB does not change. Then, in the case of +bl in Fig. 3, calculate the voltage ICX2 between the terminal 19 and the ground 17. In this case, CsX is replaced with Cs,-, in the above formula (14).

The relationship between Rx and RI-X is reversed, and CB is considered to be a constant value within a short period of time.

CX 2 =Cs l-X+CII (Rx/ (Rx
+R+-x) )... (15)

Here, if it is assumed that the connection of the circuit in FIG. 3+a+ and the connection of the circuit to FIG.
From equations (14) and (15), (, Q can be eliminated.

R1-X-((Cx + Cs x)/(Cx 2
Cs x)・Rx (16). From this relationship and the formula +11 in the conventional example shown in FIG. 1, the coordinate X of the indicated point 4 is determined.

X-Rx / (Rx + R+-x) = (CX 2
Cs 1-X) / ((Cx+ C1x)→-(CX2 C1t-x))・
・ ・ ・ ・ (17) It can be calculated as follows. This equation (17) is the basic equation of the principle of coordinate detection according to the present invention.

That is, to summarize the basic principles of coordinate detection according to the present invention, the present invention has a means for quickly switching the connection of the circuits shown in FIG. 3 (al and FIG. 3 (bl) to the resistive film 1, and The equal amount of alcoholic drinkers C,+ between terminal 14 and ground 17 (Fig. 3(a)) and terminal 1 for the case of
9 and ground 17 (Fig. 3(b)
)), and further includes means for detecting stray capacitances C6X and CS I-X, and their capacitance values Cx l + Cx 2 + Cs
By calculating the equation (17) using x and CM l-X, the coordinate X of the pointing point 4 can be determined without using the human body capacitance CB of the finger touch 18.

Next, each of the above capacitances is detected by the capacitance variable digital oscillator 20 at +8) and Tb) in FIG.

The oscillation period of the output pulse from the terminal 21 of the variable capacitance digital oscillator 20 is now proportional to the equivalent capacitance value between the terminal 14 or 19 and the ground 17. Therefore, if the oscillation period in the case of ta+ in FIG. 3 is TXI, then the proportional constant is k.

TXI = k-CxI '''' (1B) Similarly, as shown in Fig. 3 (assuming the oscillation period in case of bl is Tx2).

Tx2; k-CX2 (19).

As shown in equations (18) and (19) above, the amount of alcoholic customers C is equal to
x+ and C,2 are detected as the oscillation periods TX+ and Tx2 of the output pulse from the terminal 21.

In addition, the stray capacitance Cg I-X is calculated by finger touch 1 in Fig. 3(a).
It is calculated as the equivalent capacitance value without 8. That is, the above (14
) In the formula, Rl-X is considered to be O. Therefore, let T S 1.X be the oscillation period of the output pulse from the terminal 21 when there is no finger touch 18 in FIG. 3 (al).

T. -X is the equivalent capacitance value in the state where there is no finger touch 18 in Figure 3 (bl) (this is the case where Rx is 0 in the above equation (15)), so the terminal 2 at that time
Let the oscillation period of the output pulse from 1 be Ts+-x.

T, +-x = k-c, +-x...
... is detected as (21).

Substituting the above equations (1B), (19), (20), and (21) into the above equation (17).

The coordinates X of the indicated point 4 are.

x= (Tx 2-Ts +-x)/ ((TXI-Tsx)+ (Tx2-Ts+-x)1.
It can be calculated as (22). That is, in the present invention, FIG.
First, determine the oscillation period when there is no finger touch 18 in each state of + and (b), and then determine the oscillation period in each state of +al and (b) in Figure 3 when there is finger touch 18. Accordingly, the coordinates of the point 4 indicated by the finger touch 18 are calculated from equation (22) corresponding to equation (17). Here, in the case where there is a finger touch 18, FIG. 3 (al and (b)
It is an important point of the present invention that the switching of the connection of the circuit 1 is carried out in a short time.

The above is the principle of coordinate detection according to the present invention.

Next, FIG. 4 shows the configuration of an embodiment of the present invention which is capable of detecting two-dimensional coordinates using this principle.

In FIG. 4, the touch panel 22 has a structure in which a transparent resistive film is formed on a glass substrate and further covered with a SiO2 vapor deposited film. On the left end side of the touch panel 22, an analog switch array 23 has m switch lines AxII and A.
X+21...

They are connected by the AX1 claw, and the other terminals of these switch lines are commonly connected to the connection line L+. Further, on the right side of the touch panel 22, an analog switch array 24 is arranged corresponding to the analog switch array 23, each of 9m switch lines A, 21 . A, 22°...1AX2%, and the other terminals of these switch wires are commonly connected to the connection line L2. Further, on the upper edge of the touch panel, an analog switch array 25 has n switch lines A7II.

A v l 2 + A v l 3 + ..., A
V1%, and the other terminals of these switch lines are commonly connected to the connection line L1. Similarly, on the lower edge of the touch panel 22, an analog switch array 26 has n switch lines A x 2 l + A x 22 + A x 23 corresponding to the analog switch array 25.
+'..., A) (24), and the other terminals of these switch lines are commonly connected to the connection line L2.

The control terminals of the analog switch arrays 23 and 24 are connected to the switch control line C1, and the control terminals of the analog switch arrays 25 and 26 are connected to the inverters 31 and 32.
The switch control line CI is connected to the control device 30 via the switch control line CI. The connection line Ll is connected to the switch S1 of the analog switch 27, and the switch S1 is selectively connected to the terminal 11 or 01. Also, the connection line L2 is the switch S2 of the analog switch 27.
The switch S2 is selectively connected to the terminal I2 or 02. A control terminal of analog switch 27 is connected to switch control line C2.

Switch control line C2 is connected to control device 30.

Further, the non-inverting input terminal of the operational amplifier 28 is connected to the terminals 11 and I2 of the analog switch 27, and also to the capacitance terminal of the variable capacitance digital oscillator 29. The inverting input terminal of the operational amplifier 28 is connected to the output terminal of the operational amplifier 28, and the output terminal of the operational amplifier 28 is connected to the terminals OI and 02 of the analog switch 27. An output terminal of the variable capacitance digital oscillator 29 is connected to a control device 30.

The detected coordinate values are outputted to an output terminal 31 of the control device 30. Coordinates are designated on the touch panel 22 by a finger touch 32. The changing human body capacity at that time is cB, and its ground is 33.

In the coordinate detection device having the above configuration, analog switch arrays 23, 24, 25 . and 26 are controlled by the switch control line C1 in the X direction (left/right direction of the evening/nochi panel 22) or Y direction (up/down direction of the evening/nochi panel 22)
can be opened and closed alternately. For example, when analog switch arrays 23 and 24 are turned on, analog switch arrays 25 and 26 are turned off. Further, the operational amplifier 28 is a voltage follower circuit, and its input and output terminals are alternately connected to connection lines L+ and L2 in the analog switch 27 by a switch control line C2. It is also assumed that the human body capacitance cB caused by the finger touch 32 includes the capacitance of the SiO2 vapor deposited film.

Next, the operation when a finger touch 32 is performed on the touch panel 22 in this embodiment will be described over time.

1. First, a high level signal is output from the control device 30 to the switch control line C1, and the analog switch arrays 23 and 24 are turned on, and the analog switch arrays 25 and 26 are turned off. This is due to inverters 31 and 32.

1-1. In this state, from the control device 30 to the switch control line C
A high level signal is output to analog switch 27.
, switch SI is connected to terminal 11 and switch S2 is connected to terminal 02. From the above, the equivalent circuit of the operational amplifier 28 and touch panel 22 is shown in Figure 3 (
It will be exactly the same as al. As a result, the variable capacitance digital oscillator outputs an output pulse with an oscillation period Tx+ corresponding to the equal drinking volume value CX1 between the left end of the touch panel 22 and the ground 33. The oscillation period TXI of this output pulse
is measured by a timer and a counter in the control device 30 and stored.

Also, in this state, the oscillation period 'lx when there is no finger touch 32
is measured and stored in advance, and this is the touch panel 2.
This corresponds to the stray capacitance C1X at the left end of 2.

(2)-20 Next, the signal on the switch control line C2 becomes low level, and in the analog switch 27, the switch S1 is connected to the terminal 01, and the switch S2 is connected to the terminal (2). At this time, the signal on the switch control line CI remains at high level. Through this operation, the equivalent circuit is shown in Figure 3 (bl
will be exactly the same. As a result, the variable capacitance digital oscillator outputs an output pulse with an oscillation period TX2 corresponding to the equal drinking volume value Cx2 between the right end of the touch panel 22 and the ground 33. The oscillation period TX2 of this output panel is measured and stored by the control device 30. Also, the oscillation period T6 when there is no finger touch 32 in this state. -8 is also measured and stored in advance, and this is the touch panel 2.
This corresponds to the stray capacitance C1bx at the right end of 2.

1-30 or more T X l l T
Using X 2 and T sx + T s , -x,
The above equation (22) is calculated by the calculation device within the control device 30.

The horizontal coordinates of the finger touch 32 on the touch panel 22, that is, the X coordinate, is detected and output to the output terminal 31. In this case, the X coordinate of the left end of the touch panel 22 is 0. The X coordinate of the right end is 1, and the detected X coordinate is 0
and 1.

2. Next, the signal on the switch control line C1 becomes low level, and the analog switch arrays 25 and 26 are turned on.
3 and 24 are turned off.

In the following operation, the horizontal direction of the touch panel 22 is switched to the vertical direction, and the vertical coordinates of the finger touch 32 on the touch panel 22 are changed in exactly the same way.

That is, the X coordinate is detected and output to the output terminal 31.

In this case, the X coordinate of the upper end of the touch panel 22 is O2, and the X coordinate of the lower end is 1.

Through the above-described operations, the two-dimensional coordinates of the finger touch 32 on the touch panel 22 are accurately skewed. Each operation time for the switch control is performed in a time-sharing manner at short time intervals (about 5 msec).

Next, an embodiment for setting the above-mentioned X and Y coordinates with higher precision will be described. In the above example, + Tx I
Although it was assumed that the human body capacitance does not change during the +TX 2 measurement, in reality, the human body capacitance changes slightly during that time, which limits the detection accuracy. Therefore, the above 1
-1. Repeat the steps in 1-2 several times (7! times. a = 2 to 4)
is desirable. ) Repeat, measured value T x + each time
1, Tx 21, (Tx + + Ts x), (Tx
2'l T$1-X) and integrates the value n times. Namely.

Calculate Σ (Tx + l Ts x) tI+1, #(TX2ji111-X) Shikame l. From the above results after β measurements and calculations.

T,, K)) ...... (23) The X coordinate is calculated, detected, and output to the output terminal 31. This value is the detected coordinate value Xl+X+=(TX21Ts+-x)/(
(Tx + + Ts x) + (Tx 2 + - T$
,,)) ...... It is a weighted average of (24), which effectively averages out the variations in detected coordinate values due to changes in human body capacity between TX I + l'TX 21. This makes it possible to detect the X coordinate with high precision.

The X coordinate can be considered in exactly the same way.

What is important in the embodiments of the present invention is to complete the above operations in a time-sharing manner in a short period of time that allows the human body capacitance due to finger touch to be considered constant, and if this is realized, even if the human body capacitance value is uncertain. Even if the coordinates are detected accurately.

At this time, analog switch, variable capacity digital oscillator 2
9 and the counter and arithmetic unit in the control device can be easily realized, and the overall cost can be reduced while maintaining high reliability.

Furthermore, although this embodiment was concerned with the detection of two-dimensional coordinates, it goes without saying that the principle of FIG. 3 can be used to detect one-dimensional coordinates.

Naturally, the present invention can also be applied to coordinate indicating means other than finger touch.

As another embodiment of the present invention, a transparent resistive film can be placed on a part of a CRT display device of a terminal such as a computer, thereby making it possible to use it as a touch panel for inputting information. Furthermore, even when impedance other than capacitance is used as the coordinate indicating means, the above (14)
A similar effect can be obtained by formulating a similar equation corresponding to equations (22) and the like.

(7) Effects of the Invention According to the present invention, it is possible to measure the equivalent impedance seen from both ends of a resistive film in a time-division manner, and furthermore, it is possible to calculate the weighted average of several measurements for these measurement results. This makes it possible to accurately detect coordinates even when the impedance of the coordinate indicating means is uncertain.

Furthermore, by making it possible to measure coordinates in the left and right and up and down directions in a time-divisional manner, it becomes possible to detect two-dimensional coordinates under the above conditions.

Further, according to the present invention, it is possible to provide a coordinate detection device with low cost and high reliability.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram of a conventional coordinate detection device, Fig. 2 is an explanatory diagram of the basic principle behind the present invention, and Fig. 3 (al, (b)
1 is a diagram explaining the principle of the coordinate detection device according to the present invention. FIG. 4 is a configuration diagram of a coordinate detection device according to the present invention. 22...Touch panel, 23, 24° 25.26.
...Analog switch array. 27... Analog switch, Sochi, 28... Operational amplifier, 29... Capacitance variable digital oscillator, 30.
...Control device, C1゜C2...Switch control line. ,'it l l's 1 No. 21 x 1 Fig. 3 (()) Fig. 3(b) Fig. 4 Fig. 5

Claims (14)

[Claims] (1) A coordinate type cabanel in which a resistive film is arranged on a substrate, and a coordinate indicating means for indicating a point on the resistor. a buffer circuit connected to both ends of the resistive film to maintain a constant potential at both ends; a switching means for alternately switching and connecting both ends of the resistive film and both ends of the buffer circuit; a detecting means for detecting the impedance connected and viewed from the one end in each case switched by the switching means; and a coordinate position on the coordinate cabannel indicated by the coordinate indicating means using the output value of the detecting means. A coordinate detection device characterized by having a calculation means for calculating. (2) The coordinate cabanel is a two-dimensional coordinate cabanel in which a resistive film having four ends is arranged, and any two of the four ends of the resistive film facing each other are selected. a switching means for alternately switching and connecting the two ends and both ends of the buffer circuit; and detecting impedance connected to one end of the buffer circuit and viewed from the one end in each case selectively switched by the switching means. and calculating means for calculating a two-dimensional coordinate position on the coordinate formula Cabanel indicated by the coordinate indicating means using the output value of the detecting means. Coordinate detection device as described in section. (3) The coordinate detecting device according to claim 1 or 2, wherein the coordinate indicating means is a finger touch. (4) Claim 1 or 2, characterized in that the resistive film on the substrate is covered with an insulating film.
Coordinate detection device as described in section. (5) The coordinate detection device according to claim 1, 2, or 4, wherein the substrate, the resistive film, and the insulating film are each transparent. (6) The coordinate detecting device according to claim 1, 2, or 3, wherein the coordinate type cover panel is installed on a display screen. (7) The coordinate detection device according to claim 1, wherein the buffer circuit is a voltage follower circuit. (8) A coordinate type cabanel in which a resistive film is arranged on a substrate, and a coordinate indicating means for indicating a point on the resistive film. a buffer circuit connected to both ends of the resistive film to maintain a constant potential at both ends; a switching means for alternately switching and connecting both ends of the resistive film and both ends of the buffer circuit; Detection means for detecting the impedance connected and viewed from the one end for a plurality of measurement cycles switched by the switching means;
a first calculating an average value of a plurality of output values from the detection means;
and a second calculating means for calculating a coordinate position on the coordinate formula Cabanel specified by the coordinate specifying means based on the output value of the first calculating means. Detection device. (9) The coordinate type cabanel is a two-dimensional coordinate type cabanel in which a resistive film having four ends is arranged, and any two opposing ends of the western ends of the resistive film are selected. switching means for alternately switching and connecting both ends of the buffer circuit; and means connected to one end of the buffer circuit for detecting impedance seen from the one end for a plurality of measurement cycles selectively switched by the switching means; , a first calculating means for calculating the average value of a plurality of output values from the detecting means, and a two-dimensional coordinate on the coordinate formula Cabanel specified by the coordinate specifying means based on the output value of the second calculating means. 9. The coordinate detection device according to claim 8, further comprising a second calculation means for calculating the coordinate position. (10) The coordinate detecting device according to claim 8 or 9, wherein the coordinate indicating means is a finger touch. (11) The coordinate detection device according to claim 8 or 9, wherein the resistive film on the substrate is covered with an insulating film. (12) Claim 8 or 9, wherein the substrate, the resistive film, and the insulating film are each transparent.
The coordinate detection device according to item 1 or item 11. (13) The coordinate detecting device according to claim 8, 9, or 11, wherein the coordinate type cover panel is installed on a display screen. (14) The coordinate detection device according to claim 8, wherein the pamphlet 1 circuit is a voltage follower circuit.