JPS607302A - Detecting method of coordinate-position - Google Patents

Abstract

PURPOSE:To make it possible to perform high speed detection, by switching electrodes when the potential difference between switches is zero, so that the potential distribution on a flat resistor body is continued before and after the switching, and reducing the saturation of an input-pen detecting signal circuit. CONSTITUTION:A reference sine wave signal e1 and a sine wave signal e2 are compared in a voltage comparator 15. At an instance when the output of the comparator is changed from a ''0'' to a ''1'' (from a ''1'' to a ''0''), a switching signal is sent to switch driving circuit 5 from a T.FF circuit 16. At every time the output of the comparator 15 is changed, the output is reversed by the circuit 16. Electrodes are switched at every 1 period of the sine wave signal. When the switches are changed at the time the voltages of the signals e1 and e2 are the same, the potentials on the sides of the signal sources of the electrode switches at the instance of the switching are the same. The potentials on all the points on a flat resistor body become also the same. Therefore, currents do not flow through the switches. Generation of noise is few. Saturation of an input pen detecting signal circuit is reduced. A dynamic range is reduced. Thus a high speed detection can be performed.

Description

[Detailed Description of the Invention] (a) Technical Field of the Invention The present invention relates to a coordinate position detection method using an input pen,
In particular, it relates to a method of driving electrodes provided on the four sides of a planar resistor.

(bl) Prior Art and Problems A tablet-type coordinate position detection device using a pen is known as an input device for an information processing machine. Recently, detection devices using this method have been used in personal computers, etc., and demand has increased. is on the rise.

The general configuration of such a coordinate position detection device is shown in Fig. 1, and this example uses a method in which sine wave signals with different phases are applied to two opposing sides of a planar resistor and read out. 56-191004).

In FIG. 1, A, , A2 are electrode changeover switches in contact with opposing electrodes in the Y direction of the planar resistor 1, and B, ,
B2 is an electrode changeover switch that contacts opposite electrodes in the X direction. Thus, when detecting the Y coordinate, switches A, . . . A2 are closed, and switches B, . . . B2 are kept open.

As a result, two reference sine wave signals el = E with the same frequency and amplitude and a phase difference of φ are generated on both sides of the planar resistor 1.
1 sinωt and second sine wave signal e2=E2sin(
ωt−φ) is added. When the input pen 2 is brought close to the planar resistor 1, a signal ep corresponding to the input position x (1>x>Q) is generated due to the electrostatic coupling, and the signal ep is e sin (ω is - θ). The input value 'fllx can be calculated from the phase difference θ (0<θ×φ).

The signal ep from the input pen 2 is sent to an amplifier 3. Through the filter 4, the phase comparator 5 compares it with the reference sine wave signal 131 or the second sine wave signal e2, outputs a phase difference, and determines the coordinate position X.

Figure 2 is a phase relationship diagram of these signals.
is the reference sine wave signal el, the same figure (bl is the second sine wave signal e2, and the same figure (C1 is the detection signal ep of the input pen).

Further, when detecting the X coordinate, a switch is changed and the same operation is performed.

By the way, when switching the X coordinate and Y coordinate alternately,
The timing at which the electrode pair is switched is the zero-crossing point of the reference sine wave signal or the second sine wave signal. Figure 3 shows an example of this. Figure, same figure + dl
is an operation diagram of the voltage changeover switch Bl+B2, and in this example, the switch is changed over when the reference sine wave signal is at zero voltage.

However, in this case, at least one of the sine wave signals (the second sine wave signal in FIG. 3) is not zero and there is a potential gradient on the planar resistor. A large voltage or current spike is applied to the switching element (switching element). Moreover, the potential distribution on the surface of the planar resistor! + Due to rapid changes, the detection signal from the input pen also changes suddenly, which tends to cause saturation of the subsequent filter circuit, amplifier circuit, etc. Figures 3(e) and (fl indicate such sudden changes in the signal; Figure 3(e) is the signal appearing on one of the electrodes connected to switch A1; This is a signal appearing on one of the electrodes connected to B2, and the arrow points are discontinuous portions of voltage change.

Furthermore, such a sudden change in signal voltage causes problems such as generating unnecessary electromagnetic radiation, that is, noise in the space around the planar resistor.

fcl OBJECTS OF THE INVENTION It is an object of the present invention to provide a coordinate position detection method that eliminates such drawbacks and reduces the burden on switching elements and detection signal processing circuits.

Fdl Structure of the Invention The object is to apply a reference sine wave signal to one of the opposing electrodes of a planar resistor, and to apply a second sine wave signal having the same frequency as the reference sine wave signal and a predetermined phase difference to the other side. In a coordinate position detection device that detects the position of the input pen from a phase difference between a signal detected by an input pen placed close to the surface of the planar resistor and the reference sine wave signal,
Among the electrodes provided on the four sides of the planar resistor, when performing position detection in two coordinate axis directions while alternately switching two sets of opposing electrodes, switching from one set of electrodes to the other set of electrodes. This is achieved by a coordinate position detection method in which this is performed at a time when the reference sine wave signal and the second sine wave signal are at the same potential. Furthermore, as a means of implementing this, the reference sine wave signal voltage and the second sine wave signal voltage are compared with a voltage comparator, and the electrode changeover switch is switched at the time when both have the same potential. This is accomplished by a detection method.

(el　Embodiments of the invention Examples will be described in detail below with reference to nine drawings.

Fig. 1 is a relational diagram explaining the timing of electrode switching according to the present invention, fa+ in the figure is a reference sine wave signal diagram,
bl is a second sine wave signal diagram, tc) in the figure is an operation diagram of the voltage changeover switch A I + A 2, and fdl in the figure is an operation diagram of the voltage changeover switch B l + 82. As shown in the figure, the present invention includes a reference sine wave signal e1 and a second sine wave signal e.
The switch is changed at the time when 2 and 2 become the same voltage 2, but then the voltage signal becomes continuous as shown in FIG. Figure 4 (Q) is a signal diagram appearing on one of the electrodes connected to switch A1, Figure 2 (fl is switch B2
FIG. 3 is a signal diagram appearing on one of the electrodes connected to the .

In this way, the reference sine wave signal e1 and the second sine wave signal e2
If you switch the switch at the time when and become the same voltage V,
At the moment of switching, the signal source sides of the electrode changeover switches are all at the same potential (2), and as a result, the potentials at all points on the planar resistor are also at the same potential (2). Therefore, if the switch is switched at this moment, no current will flow through the changeover switch, and the load on the switch element can be reduced. Further, since the potential distribution on the planar resistor is continuous before and after switching, there is less possibility that the input voltage detection signal processing circuit will be saturated. Furthermore, noise generation is also small.

FIG. 5 shows an embodiment of the switching circuit configuration of the electrode changeover switch according to the present invention. Changeover switch A 1. B+
Although switch drive circuits 11, 12, 13, and 14 are provided to operate the + A2 and B2, respectively, in the present invention, the reference sine wave signal e1 and the second sine wave signal e
2 is compared by the voltage comparator 15, and at the moment the output changes from O to 1 (or from 1 to 0), a switching signal is sent from the T flip-flop 1 circuit 1G to its switch drive circuit. Since the T flip-flop circuit 16 inverts its output each time the output of the comparator changes in one direction, with this circuit configuration, the electrodes can be switched every cycle of the sine wave signal.

FIG. 6 shows another example of the switching circuit configuration according to the present invention, in which the output of the voltage comparator 15 is connected to one of the electrode changeover switches A, , A.
2 as is, and the other electrode changeover switch B l
+82 is applied through impark 17. In this embodiment, the switching occurs every half cycle of the sine wave signal, so the coordinate detection speed becomes faster and the circuit becomes simpler.

FIG. 7 shows still another example of the switching circuit configuration according to the present invention, in which the output of the voltage comparator 15 is input to the counter 18, one output is applied as is, and the other output is applied to the changeover switch through the inverter 17. This is a configuration in which switching occurs every multiple cycles of the sine wave signal, and is an embodiment used when the signal from the input pen is calculated over multiple cycles to improve the accuracy of the detected value.

(fl Effects of the Invention As is clear from the above explanation, according to the present invention, the potential difference of the changeover switch becomes zero at the moment when the electrodes are switched, so the current flowing through the changeover switch becomes zero, and therefore a small A capacitive changeover switch can be used. Also, noise radiation to the surroundings is reduced.

In addition, an even more important effect is that the potential distribution change of the planar resistor is continuous before and after the switch, so the input pen detection signal circuit is less likely to be saturated, making it possible to reduce the range and enable high-speed detection. become.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of the configuration of the coordinate reading device, FIG. 2 is a phase relationship diagram of its read signals, FIG. 3 is a diagram explaining conventional electrode switching timing, and FIG. 4 is a diagram explaining the electrode switching timing according to the present invention. An explanatory diagram, FIG. 5. 6 and 7 are side views of the structure of the electrode switching circuit according to the present invention. In the figure, 1 is a planar resistor, 2 is an input vent, 3 is an amplifier, and 4
is a filter, 5 is a phase comparator, 11.12.13゜14
15 is a switch drive circuit, 15 is a voltage comparator, 16 is a T flip-flop circuit, 17 is an inverter, 1B is a counter, and Δl + A2, B l + B2 are electrode changeover switches. Figure 3 Figure 4 Figure 5- Figure 6 Figure 7

Claims (1)

[Claims] (l) A reference sine wave signal is applied to one of the opposing electrodes of the planar resistor, and a second sine wave signal having the same frequency as the reference sine wave signal and a predetermined phase difference is applied to the other side. Add wave signal,
A coordinate position detection device that detects the position of the input pen from a phase difference between a signal detected by the input pen placed close to the surface of the planar resistor and the applied sine wave signal,
Among the electrodes provided on the four sides of the planar resistor, when performing position detection in two coordinate axis directions while alternately switching two sets of opposing electrodes, switching from one set of electrodes to the other set of electrodes. A coordinate position detection method characterized in that the step is performed at a time when a reference sine wave signal and a second sine wave signal are at the same potential. (2) A patent claim characterized in that the reference sine wave signal voltage and the second sine wave signal voltage are compared by a voltage comparator, and the electrode changeover switch is switched at the time when both have the same potential. The range of coordinate position detection method described in item 1.