JPS60129828A - Position detector - Google Patents

Abstract

PURPOSE:To reduce noise caused by an external electric field and to improve the position detecting accuracy or resolution, by successively applying a prescribed voltage to numeral parallel-arranged electric conductors of a position detecting plate at intervals of a unit time over a time period which is multiple of the unit time. CONSTITUTION:A prescribed voltage VCC is successively applied to each of electric conductors X1, X2-Xn arranged in parallel at time intervals of a unit time TS over a time period 2TS which is twice the unit time TS. Namely, when the period of successively continuing unit time TS is represented as P1, P2- Pn+1, the prescribed voltage VCC is applied to the electric condutor X1 during periods P1 and P2, to the conductor X2 during periods P2 and P3, and to the conductor Xn during period Pn and Pn+1. Therefore, the prescribed voltage VCC is simultaneously applied to adjacent two conductors during the period from P2- Pn except the first and last periods P1 and Pn+1. When such arrangement is used, a signal voltage obtained at the detecting electrode of a stylus goes to a driving voltage which is about two times larger than a driving voltage at the time of the unit time TS.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention provides a method for drawing figures, etc. on a tablet board by sequentially detecting the position of the stylus on the tablet board. This data can be used to display figures on a cathode ray tube display, change the screen displayed on a cathode ray tube display, or create desired figures. The present invention relates to a position detection device in a device or a graphic creation device.

Background Art and Problems Such a position detection device has a position detection plate forming a tablet board and a stylus for drawing figures etc. on this position detection plate, and one type of the position detection device is electrostatic position detection. There is something to be done.

Figures 1 and 2 are examples of such position detection devices,
The position detection board 10 constituting the tablet board has an insulating layer 11
A large number of conductors Yl, Y2...Ym are formed on the insulating layer 11 arranged in parallel at regular intervals.
On the insulating layer 12 deposited above, conductors Y+, Yz...
...Many conductors X+, X2 perpendicular to Ym...
・Xn is conductor Y.

, Y2 . . . are arranged in parallel at the same intervals as Ym, and an insulating layer 13 is further deposited on the insulating layer 12. The stylus is position detection plate 1
It is composed of a detection electrode 31 arranged on an insulating layer 13 of 0,
A capacitor with a fixed capacitance Cf is connected between the detection electrode 31 and ground. In practice, the insulation Jilt, 12 and 13 are each made transparent and the conductors X1. X2 . . . Xn and YIll2 .

As shown in FIG. 3, within a certain period of time, a predetermined voltage Vcc is applied to each of the conductors x, , X2 . . . Given sequentially. Although not shown, within another fixed period, a predetermined voltage Vcc is similarly applied to the conductors Y+, Yz...YIll, respectively, over a unit time Ts, at time intervals of a unit time TS. Given sequentially.

Here, if the capacitance formed between the conductor to which the voltage Vcc is applied and the detection electrode 31 is Cp, the signal voltage Vo obtained at the detection electrode 31 at that time is expressed as Cp+Cf, and the capacitance is The larger cp is, therefore the voltage Vcc
The smaller the distance between the conductor and the detection electrode 31, the greater the signal voltage 0 becomes. Therefore, conductor X + ,
X 2...Xn or yl.

Y2... Voltage Vcc is sequentially applied to Ym as described above, and as shown in FIG. As the signal voltage V0 obtained at the detection electrode 31 changes stepwise at a time interval of unit time TS, the signal voltage V0 obtained at the detection electrode 31 changes stepwise at a time interval of unit time TS, and the voltage of the conductors X+, Xz...X
n or Y.

, yz . . . The maximum value Vm is reached when the voltage Vcc is applied to the conductor closest to the position of the detection electrode 31 among Ym. However, the signal voltage Vo is actually the fifth
As shown in the figure, the voltage Vcc is obtained only when the voltage Vcc is applied to several conductors before and after the point where the detection electrode 31 is located;
When c is given, it is almost equal to zero.

Based on this signal voltage Vo, the detection electrode 31
Conductors X,,X2...Xn on the position detection plate 10 of
The X direction which is the arrangement direction of the conductors Y1, Y2...
The position in the Y direction, which is the arrangement direction of Ym, is detected. Specifically, the signal voltage V0 obtained at the detection electrode 31 is supplied to the tuned amplifier circuit, and as shown in FIG.
A signal sb of a predetermined frequency that reaches its maximum amplitude after a certain time delay from the time when Vm reaches its maximum value is obtained, and this signal sb is supplied to a Schmitt trigger circuit so that the signal sb changes the predetermined positive potential Vs from negative to negative. A signal Sz is obtained which falls from a high level to a low level when the ground potential crosses in the positive direction, and then rises from a low level to a high level when the ground potential crosses from the positive direction to the negative direction. And conductor X1. X2
...The subsequent signal Sz first rises from the time t when the voltage Vcc is applied to the nearest conductor XI to Y of Xn to Y, Y, ...Ym. During the period up to time t2, the counter counts clock pulses whose period is sufficiently shorter than the above-mentioned unit time Ts, thereby detecting the time Td from time 1° to time t2, and the output of the counter at this time t2. The data is the above-mentioned X on the position detection plate 10 of the detection electrode 31.
It is taken out as a detection output of the position in the direction or Y direction.

Note that the capacitance Cp formed between the conductor to which the voltage Vcc is applied and the detection electrode 31 becomes smaller as the distance between the conductor and the detection electrode 31 becomes larger, and becomes larger as the width of the conductor becomes larger.

Therefore, the voltage Vcc is applied to the conductors XI, X2...Xn.
When detecting the position in the X direction where
I, Y2 . . . Ym. As shown in , the width of the lower conductors Y, , Y, . . . Small upper conductor X+, X2...Xn
is made larger than that of

By the way, in such a position detection device, an external electric field such as an electric field emitted by a cathode ray tube display device used together is detected by the stylus, and noise due to the external electric field is often mixed into the voltage obtained at the detection electrode 31. . Further, thermal noise is generated from the above-mentioned tuned amplifier circuit. If there is noise in the voltage obtained at the detection electrode 31 or in the output signal sb of the tuned amplifier circuit, the time t of the first rise of the output signal S2 of the Schmitt trigger circuit described above
2. Therefore, the above-mentioned time Td does not necessarily correspond to the position of the detection electrode 31 on the position detection plate 10 in the X direction or the Y direction, resulting in a disadvantage that the precision or resolution of position detection deteriorates.

Purpose of the Invention In view of this point, the present invention aims to reduce the influence of noise caused by external electric fields and the like, thereby increasing the precision or resolution of position detection.

SUMMARY OF THE INVENTION In the present invention, a predetermined voltage is applied to a plurality of conductors arranged in parallel on a position detection board at time intervals of a unit time so as to apply a predetermined voltage to the same conductor for a time that is multiple times the unit time. Give them sequentially. For example, a large number of four bodies arranged in parallel are X.

, Xz + X3..."'Xn-+, Xn, these conductors X +
, X2, X3...Xn-+ + Xn,
The respective predetermined voltages Vcc are sequentially applied at time intervals of the unit time Ts over a time period 2Ts, which is twice the unit time Ts. In other words, the periods of successive unit time Ts are P+, P2+ P3...,
If HPn-1, Pn, P-+, then conductor X.

conductor X2 has periods P2 and P2, and conductor X2 has periods P2 and P2.
3, . . . conductor X, , has periods P1-1 and Pn
Then, a predetermined voltage Vcc is applied to the conductor Xn during periods Pn and P□1, respectively, and thus, periods PK and P3 except the first period P and the last period P1141.
``-PR-+ and Pn, a predetermined voltage Vcc is simultaneously applied to two adjacent conductors.

In this way, the signal voltage obtained at the detection electrodes constituting the stylus will be approximately multiple times that when the stylus is driven as shown in FIG. Specifically, when driving as shown in the upper part of FIG. 6, the amount is approximately doubled. To explain the reason, when driving as shown in the upper part of FIG. 6, in the first period P, as shown in the upper part of FIG. 7, the voltage Vcc is applied only to the conductor X2. X3...
... is grounded. Here, the detection electrode 31 and the conductor
, X2, X3..., CPI+CP2+CF2..., then the fixed capacitance Cf is equal to these capacitances Cp, , Cp2... C, 3...
Since the capacitances C, , □, C, 3, etc., which are sufficiently large compared to the capacitance Cf and connected in parallel with the capacitance Cf, can be ignored, the signal voltage vol in the period Pl is expressed as . At this time, the voltage across the capacitor CP is Vcc-V. It is 1. In the next period P2, as shown in the lower part of FIG. 7, a voltage Vcc is applied to the conductors X and X2. At this time, as the voltage of the conductor X2 increases from the ground potential to Vcc, the voltage Vcc is applied to the series capacitance of the capacitor Cf and the capacitor CP□, which initially has no potential difference, and the voltage vol
The capacitance Cf has the same initial voltage ■. Capacity C with 1
A charge of CPz+Cf flows through P□, and as a result, the signal voltage ■ during period P2.

2 is the signal voltage ■ during period PI. 1, Cf Cp
□+Cf The height increases by Cpz+Cf, and it becomes V 02 =V o H+ΔV (4). As is clear from this, when driving as shown in the upper part of FIG. 6, the signal voltage ■0 obtained at the detection electrode 31 is as shown in the lower part of FIG.
X2...Xn has periods P + and P z, respectively
...When the voltage Vcc is sequentially applied to Pn, the signal voltage Voa is applied to the conductors x, , X2 ...
Period P2゜P3 for Xn respectively...P 114
1, the signal voltage Vob when the voltages Vcc are sequentially applied is equal to a superimposed one, and is approximately twice that when driven as shown in FIG.

Therefore, according to the present invention, the voltage S obtained at the detection electrode is
/N is improved, the influence of noise due to external electric fields is relatively reduced, and the accuracy or resolution of position detection is improved.

Embodiment FIG. 8 shows an example of the position detection device of the present invention, in which the position detection plate 1
0 has conductors Y+ and Y2 on the insulating layer 11.

...Ym are arranged in parallel, and insulation N
On the insulation 112 deposited on the conductors X+ and Xz
, . The width of the lower conductors Y, Y2...Ym is made larger than that of the upper conductors >C+, Xz...Xn. Note that the insulating layers 11 and 12 and the insulating layer 1
The insulating layers deposited on 2 are each made transparent and the conductors
+, Xz...Xn and Y+, Yz...
・Ym is also formed as a transparent electrode using a Nesa film.

On the other hand, from the clock pulse generation circuit 41, for example, 4
A clock pulse C0 with a frequency of MHz is obtained, which is supplied to a frequency divider circuit 42, for example, to another signal generating port 1.
i843, the clock pulse C is supplied from the circuit 43 and has a period of the unit detection period, as shown in FIG.
Detection start signal S having a pulse width of, for example, two periods of s
t, and for example 2 of the clock pulse Cs for the signal St.
The drive start signal D0 is delayed by a period of time, the detection period identification signal sty whose level is inverted every cycle of the signal 3t, and the period P in which the signal Sxy of the signal D0 is at a high level.
A signal Dx consisting of a pulse at x and a signal Dy consisting of a pulse during a period py during which the signal Sxy of the signal D0 is at a low level are obtained.

Then, the clock pulse Cs is supplied to the shift register 24- as a shift pulse, the signal Dx is supplied to the shift register 24 as a data pulse, and from the time of the leading edge of the signal Dx within the period px, the clock pulse Cs
During the driving period up to the point in time when (n+1) cycles have elapsed, the output terminals N+ and NZ of the shift register 24
. . . Nn is a pulse signal each having a pulse width of two periods of the clock pulse Cs, ,,D,! ...
...D Xn is the time T for one cycle of the clock pulse Cs
This pulse signal DX, is obtained sequentially at a time interval of s.

I) xz...D Time Ts for one cycle of clock pulse Cs
The conductors X, , X
2...The voltage Vcc from the power supply terminal 21 is sequentially applied to Xn over a time period 2Ts corresponding to two cycles of the clock pulse Cs at time intervals of a time Ts corresponding to one cycle of the clock pulse Cs.

Similarly, the clock pulse Cs is supplied to the shift register 25 as a shift pulse, and the signal Dy is supplied to the shift register 25 as a data pulse, so that from the time of the leading edge of the signal DyO within the period py, the clock pulse Cs ( During the drive period up to the point in time when m+1) cycles have elapsed, the output terminals M, , M2 . . . of the shift register 25
...Pulse signal DI'l+I)Y2... having a pulse width of two cycles of clock pulse C3 in each Mm...
...Dym is the time Ts for one period of the clock pulse C3
These pulse signals Dv, , D, are obtained sequentially at time intervals of
.

...pym is the switch 23 of the switch circuit 23,
．． 23□ ... Supplied to 23m, switch 2
3+, 23z...23m is from terminal A side to terminal B
The conductors YI, Y2...
. . . The voltage VCC from the power supply terminal 21 is sequentially applied to Ym over a time period 2Ts corresponding to two cycles of the clock pulse Cs at time intervals of a time Ts corresponding to one cycle of the clock pulse C8.

The detection electrode 31 constituting the stylus 30 is placed on the position detection plate IO with its head facing the outside of the shield case 33, and is grounded inside the shield case 33 via a capacitor 32 with a fixed capacitance Cf. Further, the detection electrode 31 is connected to the gate of a field effect transistor 34 inside the shield case 33, and a bias resistor 35 is connected between the gate of the transistor 34 and ground. Therefore, the signal voltage V obtained at the detection electrode 31
0 differs from that shown in FIG. 6 in that it does not have a complete step-like shape due to the occurrence of discharge through the resistor 35, but in period Px, the detection electrode 31 of the conductors X+, Xz...Xn It is maximum when the voltage Vcc is applied to the conductor closest to the position of , and in the period py, the conductor Yl,
Ym...The voltage is maximized when the voltage Vcc is applied to the conductor of Ym closest to the position of the detection electrode 31.

The voltage Vo obtained at the detection electrode 31 is supplied to the tuned amplifier circuit 51 through the field effect transistor 34, and a signal sb of a constant frequency that reaches its maximum amplitude after a certain time delay from the time when the voltage Vo reaches its maximum is obtained. The signal sb is supplied to the Schmitt trigger circuit 52, and as shown in FIG. 9, the signal sb falls from a high level to a low level when it crosses a predetermined positive potential Vs from negative to positive.
Thereafter, when the ground potential reverses from positive to negative, a signal Sz rising from a low level to a high level is obtained.

Then, a drive start signal D obtained from the signal generation circuit 43
o is supplied to the cent terminal S of the RS flip-flop 53, and the output signal SZ of the Schmitt trigger circuit 52 is supplied to the RS
It is supplied to the reset terminal R of the flip-flop 53,
RS Free 7 Bufuwa.

53, the time t at which the voltage Vcc is applied to the conductors X1 to YI at the beginning of the driving period within the period Px to py.
, after which the output signal sb of the tuned amplifier circuit 51 crosses the ground potential from positive to negative for the first time,
That is, after that, the output signal Sz of the Schmitt trigger circuit 52 first rises at a time t2, and then the signal Gc falls.
is obtained. Further, the detection start signal St obtained from the signal generation circuit 43 is supplied to the clear terminal CLR of the counter 54, the counter 54 is cleared at the beginning of the period Px or py, and the detection start signal St obtained from the clock pulse generation circuit 41 is cleared. -Tsuku pulse C0 and the output signal Gc of the RS flip-flop 53 are supplied to the AND gate 55,
During the high level period of the signal Gc, the clock pulse C0
The clock pulse obtained from the AND gate 55 during the high level period of the signal Gc within the period Px to Py after the counter 54 is cleared is supplied to the clock terminal CK of the counter 54 and counted. Ru. That is, the period Px to P is determined by the counter 54.
The time Td of the high level period of the signal Gc at y is the conductor Xt on the position detection plate 10 of the detection electrode 31 at that time,
Xz......X direction which is the arrangement direction of Xn or conductor y, Yz......Y which is the arrangement direction of YTIl
It is detected as the position in the direction.

Note that the output signal Sz of the Schmitt trigger circuit 52 is R
It is supplied to the node terminal S of the S flip-flop 56,
The detection start signal 3t obtained from the signal generation circuit 43 is RS
is supplied to the reset terminal R of the flip-flop 56,
A signal Sa is obtained from the RS flip-flop 56 and becomes high level during the period in which the output data of the counter 54 is indicative of the time Td. The detection period identification signal 3xy is supplied to the data processing circuit 57, and the circuit 57 obtains data as a detection output of the position of the detection electrode 31 on the position detection plate 10 in the X direction and the Y direction.

Effects of the Invention According to the present invention, a predetermined voltage is applied to each of the multiple conductors arranged in parallel on the position detection board for a time that is multiple times the unit time. Since the signals are applied sequentially at intervals, the signal voltage obtained at the detection electrodes constituting the stylus increases, and the S/N ratio of the voltage obtained at the detection electrodes improves, as clarified in the section of the summary of the invention. , the influence of noise due to external electric fields is relatively reduced, and the accuracy or resolution of position detection is improved.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the main parts of an example of a position detection device to which the present invention is applied, FIG. 2 is a diagram showing the arrangement relationship of its conductors, and FIG.
4 and 5 are diagrams for explaining the operation. FIG. 6 is a diagram showing the driving method according to the present invention and the form of the signal voltage when it is applied. FIG. 7 is a diagram showing the conventional driving method. 8 is a diagram for explaining the increase in signal voltage, FIG. 8 is a diagram showing the configuration of an example of the position detection device of the present invention, and FIG. 9 is a waveform diagram for explaining its operation. In the figure, 10 is a position detection plate, XI, XI...Xn
and Y, , Y2...Ym is a conductor, 31 is a detection electrode, and Ts is a unit time. Figure 4 Figure 5 d Figure 6 Figure 7

Claims (1)

[Claims] It has a position detection plate in which a large number of conductors are arranged in parallel on an insulating layer, and a detection electrode arranged on this position detection plate, and a predetermined voltage is applied to each of the plurality of conductors of the position detection plate. is sequentially applied to the same conductor at time intervals of the unit time so that the voltage is applied to the same conductor over a time period that is multiple times the unit time, and based on the voltage obtained at the detection electrode, the position of the detection electrode is determined on the detection plate. A position detection device for detecting the position of the plurality of conductors in the arrangement direction.