JPH01159721A - Input position detection circuit - Google Patents

Abstract

PURPOSE:To constitute the title circuit by simple circuit constitution by generating a potential gradient on a tablet, outputting the voltage of a point touched by an indicator pen as a pulse from a comparison circuit and outputting it as the clock of a definite frequency by a counter. CONSTITUTION:The tablet 4 of an input position detection circuit consists of a resistance plate whose resistance value varies at the contacting point of the indicator pen 21, and the electrodes 5X-6Y of X, Y axes are formed at its external circumference, and one side of it is connected to a power source through a selector switch 7 and the other side is grounded through the selector switch 9. A resistor 8 and a capacitor 14 as a charging circuit are connected to the above-mentioned indicator pen 21. Besides, a transistor as a switch circuit is connected to it. A reference voltage is connected to the comparison circuit 15, and a counter 17, a latch circuit 19 and an averaging circuit 20 are connected by turns to the output side of the circuit 15. Thus, when the surface of the tablet 4 is touched by the indicator pen 21, the potential gradient is formed, and the voltage is generated, and the pulse by a prescribed time constant is outputted from the comparison circuit 15, and the clock signal of definite frequency is outputted.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to an input position detection circuit for inputting position information of characters, figures, etc. using an indicator pen.

"Prior Art" Generally, in order to detect pressure position information on a sensitive sheet, as shown in FIG. 6, a resistance plate (1), a pressure sensitive sheet (2),
Conductive plates (3) are laminated to form a tablet (4), and around the resistive plate (1) of this tablet (4) are X thin electrodes (5X) (6X) consisting of a group of diodes, and Y thin electrodes (
5Y) (6Y) and one XY electrode (5X) (
5Y) is connected to the power supply (8) via one selector switch (7).
Combined with.

The other xy electrodes (6X) (6Y) are grounded via the other interlocking changeover switch (9). However, in such a device, pressure is applied to an arbitrary position on the tablet (4) using the pointing pen (21). Switch the switch (7) (9) to the X-axis side contact while pressurized to detect the potential distribution in the X-axis direction, then switch the switch (7) (9) to the Y-axis contact while pressurized. Switch to contact and detect the potential distribution in the Y-axis direction. Each detected analog information is amplified by an amplifier (10), and further A/
It is converted into digital information by a D converter (11) and output via an input/output circuit (12).

"Problems to be Solved by the Invention" In the conventional circuit, the analog information detected from the tablet (4) is converted to digital information by the A/D converter (11) and output. (11) Not only is it complicated and expensive, but the indicator pen (21) can be used on a tablet (
4) There is a problem in that the fluctuation in the analog signal output due to the fluctuation when pressurizing is directly converted into a digital signal, and the processing of the fluctuated digital signal is extremely troublesome.

"Means for Solving the Problems" The present invention has been made to solve the above-mentioned problems, and includes a method in which an indicator pen is brought into contact with a tablet and positional information of this contact point is detected as a voltage value. a charging circuit that charges either one of the tablet output voltage and a preset reference voltage at a predetermined time constant, the charging voltage of this charging circuit, the reference voltage and the output voltage of the tablet; A comparator circuit that compares the voltage with the other voltage and outputs a pulse when they match, and a comparator circuit that counts and outputs a clock signal that is sufficiently shorter than the pulse interval and oscillates at a constant frequency during the pulse interval of this comparator circuit. It is equipped with a counter.

"Operation" When you touch any point on the tablet with the indicator pen, first,
A voltage is applied in the X-axis direction to form a potential gradient on the tablet, and a voltage corresponding to the point of contact is generated. This voltage charges the capacitor of the charging circuit with a predetermined time constant. When the charging voltage increases and reaches a preset reference voltage, a pulse is output from the comparator circuit. This pulse turns on the counter and outputs a clock signal of a constant frequency. At the same time, the charging circuit is rapidly discharged. Once discharged, it will start charging again. In this way, pulses with a certain period are generated from the start of charging to the time of discharging. This cycle is
It is determined according to the voltage corresponding to the contact point. As a result, the number of clock signals between two pulses becomes position information on the X-axis of the contact point.

After detecting the potential in the X-axis direction, a voltage is applied to the tablet in the Y-axis direction and position information on the Y-axis is obtained in the same way, and the desired position information is obtained from these position information on the X and Y axes. It will be done. Note that the charging circuit may charge a reference voltage, and the comparing circuit may compare this voltage with a voltage value as positional information obtained by the pointing pen of the tablet.

``Example'' An example of the present invention will be described below with reference to the drawings. 6th
Parts that are the same as those in the figures are given the same reference numerals.

In Fig. 1, (4) is a tablet, and this tablet (4) consists of a resistance plate whose resistance value changes depending on the contact point of the indicator pen (21). ) (6X), (5Y) (6Y) are formed. One of these X, Y electrodes (5X) (5Y)
is connected to the power supply (10B) via the negative selector switch (7), and the other X and Y electrodes (6X) (6Y) are grounded via the other interlocking selector switch (9). .

The indicator pen (21) includes a resistor (8) as a charging circuit.
and a capacitor (14), and the connection point between the resistor (8) and the capacitor (14) is coupled to the + side input terminal of the comparator circuit (15), and the collector of the transistor (13) as a switch circuit. is combined with

A power source (10 B) for setting a reference voltage and a variable resistor (16) are coupled to the − input terminals of the comparison circuit (15). Further, a counter (17) is coupled to the output side, and is also coupled to the base of the transistor (13) and the base resistor, and the emitter of this transistor (13) is grounded. A constant frequency clock signal input terminal (18) is coupled to the counter (17).

Furthermore, a latch circuit (19) and an averaging circuit (20) are connected in sequence on the digital signal output side.

In such a configuration, an arbitrary point on the tablet (4) is brought into contact with the pointing pen (21). Changeover switch (7)
(9) Initially, the power supply (
+B) +71 It is switched so that a constant voltage is applied. In this state, a potential gradient is formed in the X-axis direction, so a voltage corresponding to the contact point is outputted via the indicator pen (21). This output voltage is charged to the capacitor (14) via the resistor (8) with a constant time constant, and the charging characteristic curve at this time is determined by the voltage value corresponding to the contact point as shown in Fig. 2 (Ao) (A , ) (Aa).

Output with various changes. When this charging voltage reaches the preset reference voltage (Vf), the comparator circuit (15) outputs an output at a predetermined period (tO) (ti) (t), which is counted by the counter (17). The number of clock signals is fixed by the latch circuit (19).Then, when the counter (17) is reset, it starts counting clock signals of a constant frequency again.At the same time, the transistor (13) is turned on and the capacitor (14) is charged. Charge is a transistor (13)
is rapidly discharged through. When the pulse disappears, the transistor (13) turns off and charges the capacitor (14) again. The period (to) (tL) (tl) between two pulses during discharge from the comparator circuit (15) corresponds to the position information on the X axis, for example, corresponds to the period (to) of the solid line characteristic (80). A clock signal with a constant frequency is a latch circuit (19)
- time is stored and sent to the averaging circuit (20) at the next pulse of the comparator circuit (15). Then, the outputs of the latch circuit (19) several times are averaged and output from the output terminal (22) as a final digital signal in the X-axis direction. When the detection in the X-axis direction is completed, the changeover switch (7) (9)
Switching to the axis side, Y-axis position information is detected by a similar operation. Target position information is detected as a digital value from the X and Y position information detected in this manner.

Although the voltage value of the tablet (4) is used in the embodiment shown in FIG. 1 above, the present invention is not limited to this, and the resistance value of the tablet (4) may also be used.

In this case, in the circuit shown in Figure 1, it is only necessary to remove the ground side (6X) (6Y) of the tablet (4), and
A constant voltage is supplied to the X thin electrodes (5X) (5Y) from the power supply (+B). With such a configuration, a linear output is obtained rather than using a voltage value, so correction is unnecessary or becomes extremely simple.

Next, another embodiment will be explained based on FIG.

In this embodiment, the detected voltage of the tablet (4) is applied to the negative pole of the comparator circuit (15), and the reference voltage is applied to the resistor (8).
In addition to the charging circuit consisting of the
This is in addition to the electrodes. In other words, the indicator pen (
21) makes contact with an arbitrary point on the tablet (4), the detected voltage changes according to the contact point as shown in FIG.
) (V, ) (V, ).

However, as shown in Figure 4, the charge/discharge characteristics of the reference voltage (Vf
) is always constant. Therefore, the detection voltage characteristics (v,
) (v, ) (v, ) and the period (t.) (tl) (tl) of the intersection of the charging/discharging characteristic (Vf) corresponds to the contact point of the indicator pen (21) on the X-axis and Y-axis position information becomes. and,
As in FIG. 1, the number of clock pulses of a constant frequency during the period (tO) (tt) (tl) is counted by a counter (17), averaged, and output as a digital value.

In all of the above embodiments, the tablet (4) is made of a resistor, but it can also be made of a dielectric material that takes advantage of changes in capacitance. That is, in FIG. 5, in the X-axis direction,
A first dielectric (23) having a uniformly varied thickness is provided,
The upper surface of this first dielectric (23) is covered with a conductive protective sheet (
24), and a first electrode (25) is formed on the lower surface. A second dielectric (26) is further laminated on the lower surface of the first dielectric (23). This second dielectric (26) has a thickness that changes uniformly in the Y-axis direction with the first and second dielectrics (23) (26) laminated, and also has a thickness that changes uniformly in the Y-axis direction. A second electrode (27) is formed on. The first and second electrodes (25) and (27) are connected to a constant voltage power source (10B) via a changeover switch (28) and a resistor (8), respectively, and are also connected to a changeover switch (28). The connection point of the resistor (8) is connected to the electrode of the comparator circuit (15). Furthermore, the indicator pen (21) is grounded. The other configurations are the same as in FIG. 1.

In such a configuration, the selector switch (28) is
When you switch to the electrode (25) side and touch the indicator pen (21) to any one point on the first dielectric (23), the first electrode (
23) and the indicator pen (21) serves as a capacitor (14) in FIG. 1, and the detected voltage is charged at a predetermined time constant. The digital position information in the X-axis direction is obtained by repeating charging and discharging, as in FIG. 1.

Next, when the changeover switch (28) is switched to the Y-axis electrode (27) side, both the first and second dielectrics (23) (26
) becomes the capacitor (14) in FIG. 1, and position information in the Y-axis direction can be obtained.

"Effects of the Invention" Since the present invention is configured as described above, even if the position information on the X-axis and Y-axis is output as an analog signal, it is averaged as a digital signal based on the number of pulses of a clock signal of a constant frequency. It has the advantage of being able to output accurate data and having an extremely simple circuit configuration.

[Brief explanation of the drawing]

FIG. 1 is an electric circuit diagram of a first embodiment of the input position detection circuit according to the present invention, FIG. 2 is an output waveform diagram, FIG. 3 is an electric circuit diagram of a second embodiment of the present invention, and FIG. 4 is an output FIG. 5 is an electric circuit diagram of the third embodiment of the present invention, and FIG. 6 is a conventional electric circuit diagram. (1)...Resistance plate, (2)...Pressure sensitive sheet, (3)
...Conductive film. (4)--Tab L/t, (5X) (6X) ・X
Axis electrode, (5Y) (6Y)...Y axis electrode, (7) (
9)...Selector switch, (8)...Resistor. (13)...Transistor, (14)...Capacitor, (15)...Comparison circuit, (16)...Variable resistor, (17)...Counter, (18)...Clock input Terminal, (19)...Latch circuit, (20)...
Averaging circuit, (21)... Indicator pen, (22)...
Digital output terminal, (23)...first dielectric, (2
6)...second dielectric, (28)...changeover switch.

Claims (4)

[Claims] (1) In a device in which an indicator pen is brought into contact with a tablet and the positional information of this contact point is detected as a voltage value, one of the output voltage of the tablet and a preset reference voltage is set to a predetermined value. A charging circuit that charges with a time constant, a comparison circuit that compares the charging voltage of this charging circuit with the other of the reference voltage and the output voltage of the tablet, and outputs a pulse when they match; An input position detection circuit comprising: a counter that counts and outputs a clock signal that is sufficiently shorter than the pulse interval and oscillated at a constant frequency during the pulse interval. (2) The input position detection circuit according to claim 1, wherein the charging circuit charges the output voltage of the tablet, and the comparison circuit compares this charging voltage with a reference voltage. (3) The input position detection circuit according to claim 1, wherein the charging circuit charges a reference voltage, and the comparison circuit compares this charging voltage with the output voltage of the tablet. (4) In a device in which an indicator pen is brought into contact with a tablet and positional information of the contact point is detected based on a resistance value or a capacitance value of the contact point of the tablet, the resistance value or capacitance value of the contact point of the tablet is detected. A charging circuit configured as a time constant determining element and charging with a preset constant voltage, a comparison circuit that compares the charging voltage of this charging circuit with a reference voltage and outputs a pulse when they match, and this comparison circuit. 1. An input position detection circuit comprising: a counter that counts and outputs a clock signal which is sufficiently shorter than the pulse interval and is oscillated at a constant frequency during the pulse interval.