JP3050356B2 - Tablet and driving method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tablet for inputting position information with a pen, and more particularly to an electrostatic input tablet and a position information detecting method for the input tablet.

[0002]

2. Description of the Related Art With the rapid spread of personal computers and liquid crystal displays in recent years, pen input tablets have become
The importance is increasing quickly. Pen input is promising as a pointing device instead of a mouse because it can easily input a position, and as a character input method due to the development of handwritten character recognition. To date, word processors and personal computers capable of pen input have been commercialized.

[0006] Examples of pen input methods include an electrostatic method using capacitive coupling, an electromagnetic induction method and an electromagnetic transfer method using electromagnetic waves, and a resistive film method using a change in resistance value. The present invention relates to an electrostatic system. FIG. 6 shows a configuration of a general electrostatic tablet. Tablet X
And Y, and electrode groups 24 and 25 orthogonal to the two directions, a drive circuit 22 for driving them, a pen 3, a detection circuit connected thereto, and a controller 23 for controlling these.

The position is detected by detecting a pulse generated from the electrode group by an electrode incorporated in the pen via a capacitive coupling. FIG. 7 shows an example of a pulse generated from the electrode group. For example, as shown in FIG. 6, if the pen position is closest to the X8th and Y3rd positions, the signal becomes the largest when the X8th pulse and the Y3rd pulse are generated, and the position can be determined.

[0005]

Although the position can be detected by a simple method as described above, this method has the following disadvantages. That is, many drive circuits (usually ICs) and their connections are required, and signal reading takes time. For example, in the case of a liquid crystal display of 640 × 480 pixels, which is a common type of a notebook personal computer at present, if the same number of electrode lines are provided, 640 + 480 = 1120 wiring unit connections and an IC for driving the wiring unit are required. become. Also, pulses are generated by the number of electrodes, and it takes time to read.

In order to solve this, Japanese Patent Publication No. 61-1311
No. 15 discloses the following invention. FIG.
2 shows a connection diagram of electrode lines used for reading in the X direction. The electrode group is an electrode group 26 of J2 to J5 and an electrode group 2 of J6 to J8.
It is divided into seven. The method of the present invention determines the position by the relative strength of the signal for the two separate groups of electrodes. For example, assuming that the pen is at the position a, a large signal appears at the positions of the pulses J5 and J6 as shown in FIG. 9A. J5 and J when in the position of b
A large signal comes out at the position of the 6th pulse. The distinction between the positions a and b is determined by the magnitude relationship between the signals J7 and J8.
At the position a, the signal at J8 is larger because the electrode at J8 is closer, and at the position b, the signal at J7 is larger. This is read and the position is determined.

Although the position can be detected with such a small number of electrode wires, as is easily supposed, this method has a drawback that it is weak against noise and the like. For example, in this case,
The difference between the second and third magnitudes is slight, and there is a high possibility that an erroneous decision is made due to some noise. Moreover, the reading positions when an erroneous determination is made are largely separated as shown in the figure, which is very inconvenient for this type of input device.

An object of the present invention is to provide a tablet capable of accurately detecting a position with a small number of electrode wires and a driving method thereof.

[0009]

According to the present invention, a tablet having an X electrode group and a Y electrode group arranged in an X direction and a Y direction, a driving circuit for driving the tablet, and an electrostatic coupling with the electrode group are provided. Of the X-electrode group and the Y-electrode group in each divided area in an electrostatic tablet comprising a pen connected by a pen and a means for reading a pulse from these electrodes through the pen. And a tablet comprising relative address electrodes grouped for each relative position in the area.

In this tablet, the block electrodes are sequentially scanned, and at this time, it is determined that the pen is located in the block indicating the maximum value of the signal detected through the pen,
When there is no difference between the signal of the block showing the maximum value and the signal from the adjacent block by a certain value or more, the pen determines that the two blocks are near each other, and then scans the relative address electrode. A tablet driving method is characterized in that it is determined that the pen is located at the address indicating the maximum value of the signal detected through the pen.

[0011]

The present invention will be described below with reference to examples. FIG. 1 shows an example of an electrode connection diagram in the X direction of the tablet of the present invention. B1 to B4 corresponding to the block
A1 to A4 corresponding to the electrode group 1 and the position in the block
Electrode group 2. Although only the X direction is shown in this figure, as will be described later, the electrode group in the Y direction is actually arranged in a form orthogonal to the X direction.

FIG. 2 shows a timing chart of pulses applied to the electrodes and output signals. When the pen is located at the position C shown in FIG. 1, the pen is in the area covered by the electrode of B2, and the largest signal is output when the pulse of B2 is generated. Similarly, the pen is closest to the A3 electrode and produces a large signal when the A3 pulse occurs. This is shown in signal (a). This indicates that the pen is at the position A3 in the block B2. In this way, it is possible to know which block is where the largest signal appears in the B electrode group, and to know where in the block where the largest signal appears in the A electrode group.

[0013] Even in the present method, it may be difficult to determine the position only by the above method. This is a case where the block is located between blocks as shown in FIG. 1D. The signal in this case is as shown in FIG. The signals for B3 and B4 are almost equal, and it is not clear to which block they belong. If B4 is considered to be larger due to some signal fluctuation, it will be erroneously recognized as point E.

In order to eliminate this, in the driving method of the present invention, when there is no large difference in the signal between the adjacent blocks, a process for determining that the position of the pen is in the vicinity of the contact portion between the two is performed. Specifically, this is performed by a circuit as shown in FIG. 3, for example. In the figure, a signal charge input to a pen 3 through a capacitance is converted into a voltage by an integrator 4 and a switch 5,
6, separate sample-and-hold circuits 7, 8 for each signal.
Is held. The voltages held by these sample and hold circuits are applied to two comparators 11 and 1 as shown in FIG.
2 is input. At this time, the input is divided directly into input and input into a next comparator by a certain ratio, for example, a coefficient of 0.9 using the multipliers 9 and 10. The determination that the signal indicating the maximum value is substantially the same as the signal of the two adjacent blocks is performed by the determination circuit 15 that determines the outputs of these comparators. The other comparator 13 connected to the integrator is a circuit for not judging a signal value below a certain threshold voltage 14. In other words, this circuit is for preventing a case where a signal is weak to determine that the signal looks like a maximum value due to noise.

FIG. 4 shows the judgment conditions of this circuit. The output of the comparator 11 is CA, and the output of the comparator 12 is C
B. The above two cases are when the maximum value is taken at B2,
Since B1 and B3 are smaller than B2, only CB of the comparator takes the value of H. Next, the following two cases in which the values of B1 and B2 are close to each other. When B1 and B2 are larger than 0.9 times each other, both comparators become H, and only at this time, it is determined that the maximum value is obtained in the two blocks. That is, it is determined that the pen is located near the middle of both blocks.

FIG. 5 shows another embodiment. In the figure,
4 is as described above, and is a block electrode group 1 in the Y direction.
6, a group of relative address electrodes 17 in the Y direction, a drive circuit 18 for driving them, an A / D converter 19 for converting the output of the integrator 4 from analog to digital, a memory 20 for storing the data, and processing of data on the memory. It comprises an arithmetic unit 21. The above-described processing of comparing the maximum value and the signal between adjacent blocks can be performed by recording all the signals once and then performing software processing.

[0017]

When the tablet of the present invention described above and its driving method are compared with the conventional example, the following differences are found. In the conventional example, it is difficult to determine an accurate position unless the first, second, and third orders are determined for the determination of the signal magnitude. In particular, the second and third signals tend to be weak, causing malfunction.

On the other hand, in the case of the present invention, basically, only the maximum value is obtained. However, if the pen is near the block break, it may not be clear which is the maximum value, but if the second signal is so large that there is no difference between the maximum values, two Both are processed as the maximum, and it is determined that the pen is near the cut. Since this processing occurs when the second signal is large, a weak signal is not handled as in the conventional example. Also, at this time, the first and second numbers may be either, so they are strong against noise. Thus, much more accurate position detection can be performed as compared with the conventional example.

As a result, the problems of the drive IC, the number of wiring connections, and the length of the reading time, which were problems in the general electrostatic system, can be truly solved. For example, a liquid crystal display of about 640 × 480 pixels requires more than 1000 connections and more than a dozen ICs. In the present invention, 32 block electrode groups in the X direction, 20 relative address electrode groups, and 20 block electrodes in the Y direction. There were 20 groups and 20 relative address electrode groups, for a total of 92, and the number and time could be reduced to about 1/10.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an X-direction electrode group of a tablet of the present invention.

FIG. 2 is a diagram showing a timing chart and signals of the present invention.

FIG. 3 is a diagram illustrating an example of a detection unit of the tablet of the present invention.

FIG. 4 is a diagram showing a position determination condition.

FIG. 5 is a diagram showing an embodiment of the present invention.

FIG. 6 is a diagram illustrating a configuration example of a general electrostatic tablet.

FIG. 7 is a timing chart of a conventional type.

FIG. 8 is a diagram showing a configuration of an X-direction electrode group of another conventional tablet.

FIG. 9 is a diagram showing an example of the signal.

[Explanation of symbols]

 Reference Signs List 1 Block electrode group in X direction 2 Relative address electrode group in X direction 3 Pen 4 Integrator 5, 6 Switch 7, 8 Sample hold circuit 9, 10 Multiplier 11, 12, 13 Comparator 14 Threshold power supply 15 Judgment circuit 16 Block electrode group in Y direction 17 Relative address electrode group in Y direction 18 Drive circuit 19 A / D converter 20 Memory 21 Arithmetic unit

Claims (2)

(57) [Claims] 1. A tablet on which an X electrode group and a Y electrode group are arranged in an X direction and a Y direction, a driving circuit for driving the tablet, a pen connected to the electrode group by electrostatic coupling, and these electrodes A block electrode group in which the X electrode group and the Y electrode group are grouped for each divided area, and a relative position in the area. Do from the summarized relative address electrode group Ri, the
The reading means includes the block electrodes of the X electrode group and the Y electrode group.
Read the signal from the pole group and calculate the maximum value of the detected signal.
Judge that the indicated block has a pen or indicate the maximum value.
In the signal of the adjacent block and the signal from the adjacent block
When there is no difference exceeding a certain value, the pen position
A tablet having means for determining that it is in the vicinity of a tablet. 2. The tablet driving method according to claim 1, wherein the block electrodes are sequentially scanned, and at this time, it is determined that the pen is located in a block indicating a maximum value of a signal detected through the pen, and If there is no difference between the signal of the block showing the maximum value and the signal from the adjacent block by a certain value or more, the pen determines that both blocks are in contact with each other, and then scans the relative address electrode. And determining that the pen is located at an address indicating the maximum value of the signal detected through the tablet.