JPS60181915A - Coordinate detecting device - Google Patents

Abstract

PURPOSE:To obtain a detecting device which is inexpensive and has high reliability by adding a simple buffer circuit, when detecting a coordinate by a resistance sheet. CONSTITUTION:An indicating point 4 is indicated by an impedance (corresponding to a finger or an indicating pen) whose one side has been grounded to an earth 17, and a resistance sheet 1 detects its coordinate (x). In this case, as for both terminals of the sheet 1, a terminal 14 is connected to a terminal 2, and also connected to a terminal 3 through an operational amplifier 15. Also, the terminal 14 is connected to a CR digital oscillator 19, and its output pulse is connected to a control device 20. In this way, as oscillation period of an output pulse of the oscillator 19 corresponding to an equivalent capacity between the terminal 14 and the earth 17 is derived by the control device 20 having a timer, and a coordinate is calculated and outputted.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The present invention relates to a coordinate input device, and more particularly to a coordinate detection device having a substrate provided with a resistive film and an impedance added thereto.

(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 device for inputting figures and letters, but there are also coordinate systems that allow you to input figures or letters by specifying a position on a specific board with your finger or a pen, and inputting the coordinates. There is an input device.

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

There is a system in which a large number of sensors are arranged in a grid on a board, instructions are given with a finger or a pen, and the coordinates are determined by signals from the sensors at the positions. 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 in that it is difficult to input coordinates with high accuracy.

Another method of coordinate input device is to use a resistor sheet as an input board, to flow a current from both ends of the resistor sheet to an impedance connection point (a contact point with a finger or a pen, etc.), and to estimate the coordinates of the connection point from the current ratio. There is a method called The principle of such a system is shown in FIG.

A terminal 5 on one side of a power source 8 is connected to the left terminal 2 of the resistive sheet 1, which is made of a uniform material, via a 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 resistance sheet 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 A/
It is connected to the D converter 11, and the output of the current measuring device 10 is A/
It is connected to the D converter 12.

The outputs of A/D converters 11 and 12 are connected to a control device 13. Then, an arbitrary position 4 on the resistance sheet 1 is indicated by an impedance 7 such as a finger or an indicator pen whose one side is grounded to the earth 7.

As a result, the coordinate X(
0≦X≦1) is specified.

In this state, the resistance value between terminals 2 and 4 is Rx, and the resistance value between terminals 3 and 4 is Rl-X. Also, the current flowing from terminal 2 to 4 is ■, and the current flowing from terminal 3 to 4 is 1
8. At this time, since the resistance value of a resistor made of a uniform material is proportional to the length of the resistor, the coordinate X of the indicated point 4 is.

It is given by x=Rx/ (Rx+R+-x) ・---・tt+. Also, since the voltage drop due to the resistance value Rx and the voltage drop due to the resistance value RI-H are equal.

The following relationship holds true: RXIX-R1-I, -8... (2). From equations (1) and (2).

X"' I+-x/ (I x +II-X) ・ ・
・ ・ It becomes 131. In other words, the coordinates X of one pointing point 4 are:
Current flowing between terminals 2 and 4 1. It can be determined by solving for the current I1-X flowing between terminals 3 and 4. Therefore, these currents ■8 and 1. -8 is detected as a voltage value by the current measuring device 9 and IO, and the A/D converter II and 1
2, and then the control device 13 calculates the equation (3), whereby the coordinate X can be determined as a digital value.

According to such a conventional method, the coordinate X of any position on the resistance sheet 1 (the left end coordinate is O9, the right end coordinate is 1, and a value between them) can be determined as a digital value. However, as the current measuring devices 9 and 10 for measuring current, an operational amplifier or the like is required to convert the current into voltage, and an A/D converter with high quantization accuracy is required to improve the accuracy of the value of X. 11 and 12 are required, which makes the circuit complicated and increases the cost.

(4) Object of the Invention In order to eliminate the above-mentioned problems, an object of the present invention is to provide an inexpensive coordinate detection device that can simplify the electric circuit for detecting the coordinates on the resistive sheet.

(5) Structure of the Invention According to the present invention, the above-mentioned object includes: a coordinate entry cover panel having a resistive film disposed on a substrate; a coordinate indicating means for indicating one point on the resistive film; and a coordinate indicating means connected to both ends of the resistive film. and is connected to one end of the resistive film and a buffer circuit that maintains the potentials at both ends in a constant relationship.

a detecting means for detecting impedance between the one end and the ground of the coordinate indicating means; and an arithmetic means for calculating the coordinate position on the resistive film indicated by the coordinate indicating means using the output value of the detecting means. The present invention is configured by providing a coordinate detection device characterized by having the following.

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

FIG. 2 is a diagram for explaining the present invention in detail.

The resistance sheet 1 is the same as the conventional example explained in FIG. To detect.

In this case as well, the coordinates of the left terminal 2 of the resistance sheet 1 are 0°, the coordinates of the right terminal 3 are 1, and the coordinate X of the indicated point 4 takes a value of O≦X≦1. The difference between the present invention and the conventional example is that the resistance sheet 1
The difference is that both terminals are not connected to a power source as in the conventional example.

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. The output of the operational amplifier 15 is also connected to the inverting input of the operational amplifier 15 itself.

The operational amplifier 15 in the circuit configured as described above serves as a buffer circuit that operates as a voltage follower. That is, the feature of the present invention is that the terminals 2 and 3 of the resistor sheet 1 are connected by a buffer circuit.

With this configuration, the potentials of terminals 2 and 3 with respect to the ground 17 become equal, and since the input impedance of the operational amplifier 15 can be considered infinite,
The characteristic is that the current flowing from the terminal 3 to the pointing point 4 does not include the current flowing from the terminal 3 to the pointing point 4.

Now, the potential of terminals 2 and 30 with respect to ground 17 is
, the potential of the pointing point 40 with respect to the ground 17 is Va. Also, the resistance values between terminals 2 and 4 and the resistance values between terminals 3 and 4 are set to R and R+-, respectively, as in the case of Fig. 1.
Let it be x. The impedance between the terminal 14 and the ground 17 is Zo, and the isometric impedance obtained by combining RX and R+-x is Z. The present invention utilizes the fact that the coordinate X is a function of this impedance 2.

Let's calculate this impedance Z below.

First, the current Va/Zo flowing through the impedance Zo is
This is the sum of the current (VVa)/Rx flowing to RX via the pointing point 4 and the current (v-Va)/R, -X flowing to +R+-x. That is.

becomes. However, in reality, it can be considered that no current flows through R and -U for the reason mentioned above, so the current V/Z flowing through 1 equivalent impedance Z is the current flowing through RX (
VVa)/Rx.

Namely.

V-Va Z R, """ (5) If we eliminate V and Va from equations (4) and (5) and subtract Z.

becomes. Here, if Rx, R, -, and Zo are set so that Rx + Rl-x is sufficiently smaller than the magnitude of impedance Zo, 1Zol, then equation (6) can be approximately obtained.

K1-x. Here, since the resistance sheet 1 is the same as the conventional example, the above formula (3) (conventional example) is modified.

becomes. Substituting equation (8) into equation (7), connecting with an equal sign and subtracting X.

0 2 °°゛°゛°(9) As can be seen from equation (9), by using the configuration shown in Figure 2, the coordinates X of the indicated point 4 are
The relationship is inversely proportional to the equivalent impedance Z between and ground 17. Therefore, the value of the coordinate X can be calculated by measuring the values of the equivalent impedance 2 and the impedance Zo and calculating the equation (9).

To summarize the principle of the present invention as described above, both terminals of the resistor sheet 1 are connected by a buffer circuit using a voltage follower, and the resistance value of the resistor sheet 1 corresponds to the impedance Za of the finger or indicator pen for pointing the pointing point. Set it so that it is sufficiently small compared to the actual value.

Then, measure the impedance Zo in advance,
The equivalent impedance Z between terminal 14 and ground 17 is measured by suitable measuring means. By calculating equation (9) using Z and Za accumulated in this way, the indicated point 4
The coordinate X of can be detected.

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

becomes. Here, j is a symbol representing a complex quantity, and ω is the angular frequency of the signal added to the capacitance. (10) to (7)
Substituting into the equation and connecting with an equal sign.

becomes. Therefore, the equivalent impedance between terminal 14 and ground 17 is also 2.

C=Co・-----1--... (12) RX
It can be seen that the capacitance becomes isometric with a capacitance value of -R, -8.

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).

Next, Figure 3 shows the impedance Z in the configuration of Figure 2.
Use the above ff1ca as o.

This is an embodiment of the coordinate detection device according to the present invention, which is further equipped with means for measuring the capacitance Co and the value of the equal amount C between the terminal 14 and the ground 17, and calculating the coordinate X from equation (13). . The 98-minute configuration surrounded by the broken line 18 is the same as the configuration in FIG. 2, so its explanation will be omitted. However, as the impedance 16, a large capacitance value Co (for example, to
A capacitive pen with OOPP) is used. Terminal 14 is connected to a CR digital oscillator 19 whose output pulses are connected to control device 20 . And control z11 equipped R2
The coordinate value is taken out as an output of 0.

In the above configuration, the equal amount of alcoholic customers between the terminal 14 and the ground 17 is assumed to be C. The oscillation period of the output pulse of the CR digital oscillator 19 is now directly proportional to the human power capacity connected to the terminal 14, and the control device 20 has a timer for calculating the oscillation period. Such a timer includes a counter that counts the number of input pulses within a certain period of time by δ1 according to a clock having a higher frequency than the input pulses.

Here, k is a proportionality constant between the oscillation period of the output pulse of the CR digital oscillator 19 and the human power capacity.

Let To be the oscillation period when the input capacitance from the terminal 14 is CO, and T be the oscillation period when it is C.

Each.

To- to -co (14) T = to -C (15) There is a relationship. (
14) From 2 and equations (15) and (13).

The following relationship is derived: x-1-(T/TO) . . . (I6). First, the control device 20 controls C.
The oscillation period To when the input capacitance of the R digital oscillator I9 is only the capacitor Co provided by the capacitor pen 16 is determined in advance. Similarly, the controller 20 determines the oscillation period T for the capacitance C at the coordinate X, and calculates equation (16).

You can find the coordinate X. In this case the capacity c.

Specifically, the oscillation period To at this time can be calculated by bringing the capacitive pen 16 into contact with the left terminal 2 of the resistive sheet 1, and this value is stored in a suitable storage means within the control device 20. Next, point to an appropriate point 4 on the resistance sheet 1,
The control device 2 controls the oscillation period T corresponding to the amount of alcoholic customers C at that time.
Equation (16) is calculated from this value and the previously stored value of To, and the value of the coordinate X is output as an output.

In such an embodiment, the CR digital oscillator is already commercially available as an inexpensive product, and the control device 20 can be constructed from only a simple timer, an arithmetic device, and a storage device such as a lunch.

The overall cost can be reduced while maintaining high reliability.

In the above embodiment, a capacitance pen is used as the impedance 16, but two fingers can be used as the same capacitance, and the same effect can be obtained. Using this, for example, CR in computers etc.
If two resistive sheets according to the present invention are placed on a part of a T-display device and touched with a finger, it can be used as a touch panel for inputting information. In this case, it is very easy to use a transparent resistor sheet. Furthermore, even if the surface of the resistor sheet is covered with a suitable insulating material, the same effect can be obtained if the surface of the resistor sheet is indicated by a finger because that part also becomes a capacitor.

As another example, an optical input device consisting of a photoconverter and a resistive film can be used instead of a resistive sheet, and the change in resistance value depending on the incident position of the light can be used to detect the laser beam irradiation position, deflection angle, etc. can do. This can also be applied to light pens and the like. Furthermore, if a pressure sensitive rubber or the like is used instead of the resistance sheet, the pressure position can also be detected.

(7) Effects of the Invention According to the present invention, by adding a simple buffer circuit, a highly reliable coordinate detection device is provided without requiring an expensive analog device such as an A/D converter. be able to.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a conventional coordinate detection device. FIG. 2 is a diagram explaining the principle of the coordinate detection device according to the present invention. FIG. 3 is a configuration diagram of a coordinate detection device according to the present invention. 1...Resistance sheet, 2.3...Terminal. 4... Indication point, 14... Terminal. 15...Operational amplifier, 16...Impedance (
capacitance pen), 19...CR digital oscillator, 2
0...Control device Fig. 1 Fig. 2

Claims (1)

[Scope of Claims] (1) A coordinate entry cabinet 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 keep the potentials at both ends in a constant relationship; and a detection circuit connected to one end of the resistive film to detect impedance between the one end and the ground of the coordinate indicating means. With means. A coordinate detecting device comprising: calculating means for calculating a coordinate position on the resistive film specified by the coordinate specifying means using an output value of the detecting means. (2) The coordinate detection bag according to claim 1, wherein the substrate and the resistive film according to claim 1 are made of a transparent material.(3) The coordinate detection bag according to claim 1, wherein 2. The coordinate detection device according to claim 1, wherein the resistive film is covered with an insulator. (4) The coordinate detection device according to claim 3, wherein the insulator, the resistive film, and the insulator according to claim 3 are transparent. (5) The coordinate detection device according to claim 1, wherein the buffer circuit according to claim 1 is a voltage follower circuit.