JPH0521148Y2 - - Google Patents

Description

[Detailed Description of the Invention] "Industrial Application Field" 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. X-axis electrodes 5X, 6X consisting of a group of diodes and Y-axis electrodes 5Y, 6Y are provided around the resistance plate 1 of this tablet 4, and one of the XY electrodes 5X, 5Y is connected to a power source 8a via one of the changeover switches 7. The other XY electrodes 6X, 6Y are connected to the ground via the other interlocking changeover switch 9. However, in such a device, pressure is applied to any position on the tablet 4 using the pointing pen 21. While pressurized, changeover switches 7 and 9 are switched to the contacts on the X-axis side to detect the potential distribution in the X-axis direction, and then, while pressurized, changeover switches 7 and 9 are switched to the contacts on the Y-axis side to detect the potential distribution in the Y-axis direction. Detects the potential distribution in the direction.
Each detected analog information is sent to an amplifier 10.
The signal is amplified, further converted into digital information by the A/D converter 11, and outputted via the input/output circuit 12.

``Problem that the invention seeks to solve'' 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, but the A/D converter 11 itself is complicated. Not only is it expensive, but it also has problems such as fluctuations in the analog signal output due to fluctuations when pressure is applied to the tablet 4 with the indicator pen 21 are converted directly into digital signals, making it extremely troublesome to process the fluctuating digital signals. It was hot.

``Means for Solving the Problems'' The present invention is such that the indicator pen 21 is brought into contact with the tablet 4 and the positional information of this contact point is detected as a voltage value. a charging circuit 8 that charges one of the set reference voltages at a predetermined time constant;
14, a comparison circuit 15 which compares the charging voltage of the charging circuits 8 and 14 with the other of the reference voltage and the output voltage of the tablet 4 and outputs an output when they match; and an output voltage of the comparison circuit 15. a switch circuit 13 that rapidly discharges the charging circuits 8 and 14 to make the output of the comparator circuit 15 a repetitive pulse; This is an input position detection circuit characterized by comprising a counter 17 for counting the number of repetition pulses in the input position detection circuit.

"Operation" When an arbitrary point on the tablet 4 is touched with the indicator pen 21, a voltage is first applied in the X-axis direction to form a potential gradient on the tablet 4, and a voltage corresponding to the touched point is generated. . This voltage is the charging circuit 8,
14 capacitors 14 are charged with a predetermined time constant. When the charging voltage increases and reaches a preset reference voltage, the comparison circuit 15 outputs a pulse. This pulse turns on the switch circuit 13 and rapidly discharges the charging circuits 8 and 14. Once discharged, it will start charging again. In this way, from the start of charging to the time of discharging, pulses are generated with a period corresponding to the potential gradient, and the counter 17 counts the number of pulses. Since the counter 17 receives a clock signal with a constant frequency that is sufficiently longer than the cycle of pulses caused by charging and discharging from the comparator circuit 15, the number of pulses in the cycle of this clock signal is counted, and the Get position information on the axis.

After detecting the potential in the X-axis direction, a voltage is applied to the tablet 4 in the Y-axis direction and position information on the Y-axis is obtained in the same way, and the target position information is obtained from these position information on the X and Y axes. can get.

Note that the charging circuits 8 and 14 may charge a reference voltage, and the comparison circuit 15 may compare this voltage with a voltage value as position information obtained by the pointing pen 21 of the tablet 4.

``Operation'' When an arbitrary point on the tablet is touched with the pointing pen, a voltage is first applied in the X-axis direction to form a potential gradient on the tablet, and a voltage corresponding to the touched point 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 switch circuit and rapidly discharges the charging circuit. Once discharged, it will start charging again. In this way, pulses of a certain period are generated from the start of charging to the time of discharging, and the number of pulses is counted by a counter. The period of this pulse is determined according to the voltage corresponding to the point of contact. Since a clock signal with a constant frequency that is sufficiently longer than the cycle of pulses due to charging and discharging from the comparator circuit is input to the counter, when the number of pulses in the cycle of this clock signal is counted, the number of pulses is This is position information on the axis. After detecting the potential in the X-axis direction,
A voltage is applied in the Y-axis direction of the tablet to obtain positional information on the Y-axis in the same manner, and desired positional information is obtained from these positional information on the X and Y axes. Note that the charging circuit may charge a reference voltage, and the comparing circuit may compare this voltage with a voltage value as position information obtained by the pointing pen of the tablet.

"Embodiment" An embodiment of the present invention will be described below with reference to the drawings. The same parts as in FIG. 6 are given the same reference numerals.

In FIG. 1, reference numeral 4 denotes 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.
Axial electrodes 5X, 6X, 5Y, and 6Y are formed. One of these X, Y electrodes 5X, 5Y is connected to the power supply (+B) via one of the changeover switches 2, and the other X, Y electrodes 6X, 6Y are connected to ground through the other interlocked changeover switch 9. has been done.

A resistor 8 and a capacitor 14 as a charging circuit with a sufficiently short time constant are coupled to the indicator pen 21, and the connection point of the resistor 8 and capacitor 14 is coupled to the + side input terminal of a comparator circuit 15. , are coupled to the collector of a transistor 13 as a switch circuit. - of the comparison circuit 15
The side input terminal is a power supply (+B) for setting the reference voltage.
and a variable resistor 16 are coupled. Further, a counter 17 is coupled to the output side, and is also coupled to the base of the transistor 13 and the base resistance,
The emitter of this transistor 13 is grounded. A clock signal input terminal 18 having a constant frequency and sufficiently longer than the period of the pulses from the comparator circuit 15 is coupled to the counter 17, and a latch circuit 19 and an averaging circuit 20 are sequentially coupled to the digital signal output side. has been done.

In such a configuration, an arbitrary point on the tablet 4 is brought into contact with the pointing pen 21. The changeover switches 7 and 9 are initially switched so that a voltage is applied between the X-axis electrodes 5X and 6X. 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 with a constant time constant via the resistor 8, and the charging characteristic curve at this time is A ₀ , It changes in various ways like A ₁ and A ₂ and outputs it. This charging voltage is the preset reference voltage
When Vf is reached, a predetermined output voltage appears from the comparator circuit 15, and with this output voltage, the transistor 13
is turned on, and the charging voltage of the capacitor 14 is rapidly discharged. Therefore, the output voltage of the comparison circuit 15 becomes 0, and as a result, the comparison circuit 15 outputs a pulse signal. When the output voltage of the comparison circuit 15 becomes 0, the transistor 13 is turned off,
Charging of the capacitor 14 is started again. In this way, the comparator circuit 15 outputs a pulse signal with a period of t ₀ , t ₁ , or t ₂ as shown in FIG. . In addition, a clock signal with a constant period T that is sufficiently longer than the pulse signal as shown in FIG. is counted by the counter 17. 2 of the count value output from counter 17
The value data is temporarily stored in a latch circuit 19, which is released by the next clock signal and sent to the averaging circuit 20. At the same time, the counter 17 is reset to start counting anew. The averaging circuit 20 averages the outputs of the latch circuit 19 several times and outputs it 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 switches 7 and 9 are switched to the Y-axis side, and the Y-axis position information is detected by the same operation. Target position information is detected as a digital value from the X- and Y-axis position data detected in this manner.

Although the voltage value of the tablet 4 is used in the embodiment shown in FIG. 1 above, the voltage value is not limited to this.
The resistance value of the tablet 4 can also be used.
In this case, in the circuit of FIG.
All you need to do is remove the ground side 6X, 6Y of the
Since the output is linear rather than using voltage values, correction is unnecessary or extremely simple.

Next, another embodiment will be described based on FIG.

In this embodiment, the detected voltage of the tablet 4 is applied to the negative pole of the comparison circuit 15, and the reference voltage is applied to the charging circuit consisting of the resistor 8 and the capacitor 14 to obtain a constant charge/discharge characteristic curve. 15
This is in addition to the + pole of . That is, when the pointing pen 21 touches any point on the tablet 4, the detected voltage changes as shown in the characteristics V ₀ , V ₁ , and V ₂ in FIG. 4A depending on the point of contact. However,
As shown in FIG. 4, the charge/discharge characteristic Vf of the reference voltage is always constant. Therefore, the number of pulses at any period t ₀ , t _{1 , t 2 at the intersection of the detected voltage characteristics V 0 , V 1 , V 2 and the charge} /discharge characteristic Vf in the clock signal with a constant period T is determined by the number of pulses of the indicator pen 21. This is the X-axis and Y-axis position information corresponding to the contact point. Then, as in FIG. 1, the number of pulses of any one of the periods t ₀ , t ₁ , and t ₂ between clocks of a constant frequency is counted by the counter 17, averaged, and output as a digital value.

In all of the embodiments described above, 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, a first dielectric body 23 whose thickness is uniformly varied in the X-axis direction is provided, the upper surface of this first dielectric body 23 is covered with a protective sheet 24, and the lower surface is covered with a protective sheet 24. A first electrode 25 is formed. A second dielectric 26 is further laminated on the lower surface of the first dielectric 23 . The second dielectric 26 has a thickness that changes uniformly in the Y-axis direction when the first and second dielectrics 23 and 26 are laminated. Electrode 2
form 7. Then, the first and second electrodes 25,
27 are connected to the power supply (+B) via the changeover switch 28 and the resistor 8, respectively, and the changeover switch 2
8 and the resistor 8 are connected to the + electrode of the comparator circuit 15. Further, the pointing pen 21 is grounded. The other configurations are the same as in FIG. 1.

In such a configuration, when the changeover switch 28 is switched to the X-axis electrode 25 side and the indicator pen 21 is brought into contact with any point on the first dielectric 23, the distance between the first electrode 25 and the indicator pen 21 is The capacitance is the capacitor 14 shown 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, the capacitance of both the first and second dielectrics 23 and 26 becomes the capacitor 14 in FIG. 1, and position information in the Y-axis direction is obtained.

``Effects of the invention'' (1) Even if the X-axis and Y-axis position information is output as an analog signal, it is converted into a pulse number and output as a digital signal, so accurate data can be obtained.

(2) The analog signal uses an extremely simple circuit configuration consisting of the charging circuits 8 and 14 and the switch circuit 13 to obtain a pulse signal by repeating rapid charging and discharging, which eliminates the need for a conventional complex digital circuit. You can get a digital signal even without it.

[Brief explanation of the drawing]

Figure 1 shows the first input position detection circuit according to the present invention.
An electric circuit diagram of the embodiment, FIG. 2 is an output waveform diagram of FIG. 1, and FIG. 3 is an electric circuit diagram of the second embodiment of the present invention.
4 is an output waveform diagram of FIG. 3, FIG. 5 is an electric circuit diagram of a 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... Tablet, 5X, 6X... X-axis electrode, 5Y, 6Y... Y-axis electrode, 7, 9... Changeover switch, 8...Resistor, 13...Transistor, 1
4... 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, 26... Second dielectric, 28... Changeover switch.

Claims (1)

[Scope of utility model registration request] In a device in which the indicator pen 21 is brought into contact with the tablet 4 and the positional information of this contact point is detected as a voltage value, one of the output voltage of the tablet 4 and a preset reference voltage is set to a predetermined value. Charging circuits 8 and 14 that charge with a time constant, and a comparison circuit 15 that compares the charging voltage of these charging circuits 8 and 14 with the other of the reference voltage and the output voltage of the tablet 4 and outputs an output when they match. and,
With the output voltage of this comparison circuit 15, the charging circuit 8,
a switch circuit 13 that rapidly discharges the pulse signal 14 to make the output of the comparator circuit 15 a repetitive pulse; An input position detection circuit comprising a counter 17 for counting.