JPH0239314A - Coordinate input device - Google Patents

Abstract

PURPOSE:To decrease errors due to a noise voltage by neglecting the electrostatic induced pulse in case the difference between the potentials of the detecting electrodes set right before and after application of a scan pulse exceeds a prescribed level. CONSTITUTION:The electrode lines X and Y are set on a coordinate input board 1 in the two directions orthogonal to each other with the prescribed spaces secured. A decoder driver 2 applies successively the scan pulses to the lines X and Y according to the address signal AD received from a CPU 3. A sample holding circuit 9 holds temporarily the input voltage (electrostatic induced pulse voltage and potentials set right before and after application of scan pulse) of that time point in response to the read pulse RP supplied from the CPU 3 via an input/output port 10. The CPU 3 sends the pulse RP to the circuit 9 when a detecting electrode 5 of an input pen 4 touches the board 1. Then the digital value of the pulse RP is stored in a RAM 13 and the difference is obtained between potentials of the electrode 5 set right before and after application of the scan pulse. When this potential difference exceeds a prescribed level, the mixture of high frequency noises is decided. This fact is written into the RAM 13.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a coordinate input device, and more particularly to improving the number of coordinate detections and preventing sending of erroneous data when the coordinate indicating means moves.

``Prior Art'' The present applicant has previously proposed a capacitive coupling type coordinate input device which aims to improve the number of times coordinates are detected when the coordinate indicating means is moved (Japanese Patent Application No. 63-46466 r Coordinate Manual Power Device).

In this device, the potential of the detection electrode immediately before and/or after the application of the scanning pulse is determined, and this is subtracted from the magnitude of the electrostatic induction pulse at that time, thereby reducing the noise voltage of several hundred to several KILz that occurs when the coordinate detection means is moved. We are trying to eliminate the impact.

"Problems to be Solved by the Invention" Coordinate input devices are used in various environments, and may be used in environments with a lot of high frequency noise. In this case, when we evaluated the coordinate input device proposed by the above-mentioned optical system, we found that if the scanning pulse and high frequency noise are superimposed, it may send out incorrect coordinate information.

"Means for Solving the Problem" Therefore, in the present invention, the potential of the detection electrode immediately before and after the application of the scanning pulse is detected, the difference between them is determined, and if the difference exceeds a predetermined value, the potential of the detection electrode is The coordinate calculation is performed while ignoring such electrostatic induction pulses.

``Effect'' In other words, the width of a scanning pulse is usually several microseconds, but the fact that there is a certain difference in potential when comparing the potential immediately before and after that means that the frequency changes over a period of several microseconds. In other words, this indicates that a noise component on the order of several hundred kilohertz is mixed in, and in the present invention, immediately before this,
After confirming the presence or absence of noise components by comparing the potentials immediately after, as in the previous appearance, in order to remove the influence of noise on the order of hundreds to several kilohertz caused by the movement of the coordinate input means, Alternatively, these average values are subtracted from the magnitude of the electrostatic induction pulse, and this is used as the basis for coordinate calculation.

``Example'' The details of the present invention will be explained below based on the illustrated example. 1st
The figure shows the block configuration. In the figure, 1 is a coordinate input board, which has electrode lines X (represented by thin lines extending vertically in FIG. 1) arranged at predetermined intervals in two orthogonal directions (X direction, Y direction). Electrode wires y (same, horizontal direction) are arranged. 2 is a decoder driver which sequentially applies scanning pulses to the aforementioned electrode lines X and y in accordance with an address signal AD supplied from the central processing unit 3; In addition, the central processing unit 3
will be hereinafter referred to as rCPUJ, and in the following description, when an abbreviation is shown in parentheses after the name of other parts, the abbreviation will be used thereafter.

Reference numeral 4 represents an input pen serving as a coordinate indicating means, and reference numeral 5 represents a detection electrode slidably held at the tip of the input pen. Reference numeral 6 denotes a switch, which opens and closes according to the sliding movement of the detection electrode 5. A preamplifier 7 amplifies the electrostatic induction pulse generated at the detection electrode 5. Reference numeral 9 denotes a sample hold circuit, which responds to the read pulse RP supplied from the CPU 3 via the input/output port 10 and holds the input voltage at that point in time (electrostatic induction pulse voltage and the potential immediately before and after) for a while. do. Reference numeral 11 denotes an analog-to-digital converter (AD converter), which digitally converts the output voltage of the sample and hold circuit 9 in response to the same read pulse RP. Note that the sample hold circuit 9
is used to hold the electrostatically induced pulse voltage while the AD converter 11 performs digital conversion.

The CPU 3 is a so-called microcomputer made into an integrated circuit, and according to a program stored in a read-only memory (ROM) 12, a random access memory (R
AM) 13 to execute predetermined processing.

FIG. 2 shows details of the coordinate input panel 1.

FIG. 2 shows a partial view of the coordinate input panel 1 cut along a vertical plane including the electrode wires yi in the Y direction, and electrode wires xi''xi+4 are lined up in the X direction.

These electrode wires xi"xi+4 and yi are the insulating sheet 2
The upper and lower surfaces of 1 are formed using a silk printing method using conductive ink, and on top of that, a protective resin fFIJ2 is applied.
2 and 23 are formed.

The following is an example of the electrostatic pulse generated in the detection electrode 5 when the detection electrode 5 of the input pen 4 is brought into contact with the position shown in FIG. It is shown in Fig. 3. In the figure, the pulse Sxi”Sxi
+4 is an electrostatic induction pulse generated when a scanning pulse is applied to each of the electrode lines xi to xi+4.

In addition, the detection electrode 5 of the manual pen 4 is brought into contact with the resin y122 and moved in a desired direction, and when the detection electrode 5 is at the position shown in FIG. 2, each electrode line xi''xi+4
Electrostatic induction pulse Dxi when a scanning pulse is applied to
-Dxi+4 is shown in FIG.

Further, FIG. 5 shows an example where high frequency noise is mixed in while applying a scanning pulse at a certain position while the input pen 4 is moving.

Note that it takes some time to sequentially apply scanning pulses to the electrode lines xi-xi+4. During that time, the detection electrode 5 is moving on the resin M22, so strictly speaking,
The position of the detection electrode 5 when the electrode line xi+4 is scanned is not at the position at the start of the scanning pulse application. However, using a microcomputer, each electrode line x i = x i÷
The time for applying the scanning pulse to 4 is short, and the distance that the detection electrode 5 moves during that time is also very short. Therefore, in practice, at this point, the detection electrode 5 and each electrode line xi"x
The distance of i+4 remains unchanged, and each electrostatic induction pulse generated on the detection electrode 5 has a height HDi to HDi of Dxi=Dxi+4.
+4 is the instantaneous value HNi=HNi+4 of the noise NW occurring in the detection electrode 5 at each point in time, and each pulse H8 in FIG.
i=H3i+4, respectively, are superimposed.

Therefore, in the present invention, each i? is obtained including noise.
% of the potential of the detection electrode 5 immediately before and after the induction pulse DxiNDxi÷4 HNia−HNi+
4 a, HNi b=HNi÷4b, and if this exceeds a predetermined value, the electrostatic induction pulse Dxi”
It is assumed that high frequency noise is superimposed on Dxi+4 and is ignored, and if the difference is within a predetermined value, it is assumed that there is no influence of high frequency noise and the electrostatic induction pulse Dxi''
The potential immediately before or after the magnitude of Dxi+4 HDi”HDi+4 HNia=HNi÷4a, HNib”H
Ni+4b or its average value is subtracted, and the value after the subtraction (H
5i=IIsi+4), the position of the detection electrode 5 at that time is determined.

That is, the CPU 3 detects that the detection electrode 5 of the input pen 4 is connected to the resin layer 22.
When the switch signal SW arrives, first a read pulse RP is applied to the sample hold 9 and the AD converter rIll in order to take the potential of the detection electrode 5 immediately before the scanning pulse is applied.
, and the instantaneous value of the noise NW at that time, for example, HN i
A digital value indicating a is stored in the RAM 13.

Next, the CPU 3 supplies address data AD to the decoder driver 2 to apply a scan pulse to the electrode line X or y corresponding to the address, and at the same time supplies a read pulse RP to the sample hold circuit 9 and the AD converter 11.

The electrostatic induction pulse obtained at this time, for example, HDi
A digital value indicating the value is stored in a predetermined register.

Subsequently, the CPU 3 sends a read pulse RP to the sample hold 9 and the AD converter 11 in order to obtain the potential of the electrode 5 immediately after the application of the scanning pulse, and stores in the RAM 13 a digital value indicating the noise HNib at that time.

Next, the CPU 3 executes such operations for the necessary range of electrode wires X, and obtains, for example, each instantaneous value HNi+1 a
-HNi+4a, HDi+1 to HDi+4, HNi+1
b”HNi+4 b is obtained and stored in the RAM 13.

Next, the CPU 3 determines the potentials of the detection electrodes 5 immediately before and after each of the above groups HN i a =HN i+4 a and HN
Find the difference for ib-HNi÷4b.

If the difference exceeds a predetermined value, for example, FIG.
When z+3a and HNj+3b exceed a certain predetermined value, it is assumed that high-frequency noise such as NH in FIG. Write to RAM13.

If the difference between the immediately before and after does not exceed a predetermined value (in most cases, the high frequency noise is small, so it does not exceed the predetermined value), calculate the average of the potentials immediately before and after, for example, llN1a and HNib, and The average value is subtracted from the height HDi of the electrostatic induction pulse and stored in the RAM 13. The value after this subtraction is Sxi~Sxi+'4 in Figure 3.
This corresponds to the magnitude of the electrostatic induction pulse when the input pen 4 is at rest.

After calculating the value after the subtraction, the CPU 13 calculates the coordinate of the detection electrode 5 in the X direction at that moment based on this value. Various calculation methods have already been proposed, such as the
One of them is disclosed in No. 380.

Note that the amount of data required for coordinate calculation differs depending on the method adopted. Therefore, if the data ignored in the calculation of the difference is required, the above-described process is repeated for the electrode line X to obtain the correct value of the electrostatic induction pulse.

Next, the CPU 3 performs the same process for each electrode line in the Y direction to obtain the Y coordinate, and then
The coordinate data for the direction and the Y direction is taken and compared with the previous coordinate data, and if they match, it is assumed that the detection was successful and the value is sent to a computer main body (not shown) or the like.

Note that this data comparison operation for the same position is usually extremely short, and the position of the detection electrode 5 can be assumed to remain unchanged during that time. However, if the resolution of the coordinate input device is high, the detection type (box) It is also possible that the amount of movement of 5 becomes a difference in the coordinate data and becomes cursed.In this case, the purpose of this process, which is to compare data taken at the same position, may be different from the instructions at that time due to noise. Taking into account that the purpose is to prevent the output of coordinate data at a position that is far from the actual position, if the difference between the coordinate data is within a predetermined value, it is assumed that the coordinate data is correct, and for example, the second coordinate data is output. All you have to do is output .

However, according to the present invention, it is possible to eliminate not only the noise caused by the movement of the detection pen 4 but also the influence of external noise, so if data comparison is stopped and all data is sent as it is, mm dynamic performance can be improved. Detection ability can be improved.

"Other Examples" In this example, the potential of the detection electrode 5 immediately before and after the scanning pulse is applied, for example, the average value of I(Nia and HNib) is subtracted from the magnitude HDi of the electrostatic induction pulse at that time. Alternatively, since the difference in potential immediately after is inherently small, one of the potentials may be subtracted.

``Effects of the Invention'' As explained hereinafter, according to the present invention, in addition to the noise voltage generated due to the movement of the coordinate input means, it is possible to cancel the influence of external noise, thereby reducing errors. The dynamic detection ability can be improved by reducing the number of occurrences.

Furthermore, since it is no longer affected by external noise, the check operation can be eliminated and the mm dynamic detection ability can be further improved.

[Brief explanation of the drawing]

The figures show one embodiment of the present invention; Fig. 1 is a block diagram, Fig. 2 is a sectional view showing a part of the coordinate input panel, and Fig. 3 is an example of electrostatic induction pulses when the input pen is stationary. Waveform diagram shown, No. 4
The figure is a waveform diagram showing an example of an electrostatic induction pulse (without high-frequency noise) at a certain position while the input pen is moving, and Figure 5 is a waveform diagram showing an example of an electrostatic induction pulse (with high-frequency noise mixed in) at a certain position while the input pen is moving. FIG. DESCRIPTION OF SYMBOLS 1...Coordinate manual board, 3.12.13...Coordinate calculation means, 4...Coordinate instruction means, 5...Detection electrode. 7.9.11...Detection means, X, y...
・Electrode wire. Patent applicant Pentel Co., Ltd.

Claims (1)

[Claims] a coordinate input board on which electrode wires are arranged in two orthogonal directions; a coordinate indicating means provided with detection electrodes and brought into contact with desired positions on the input board; and when a scanning pulse is applied to the electrode wires. , a detection means for detecting an electrostatic induction pulse generated in the detection electrode and a potential of the detection electrode immediately before and after the application of the scanning pulse; or their average value is subtracted from the magnitude of the electrostatic induction pulse, and the magnitude of the electrostatic induction pulse after the subtraction is used as the basis for calculating the contact position coordinates, and the difference between the two potentials is 1. A coordinate input device comprising: coordinate calculation means for calculating coordinates while ignoring the magnitude of an electrostatic induction pulse at that time when the magnitude exceeds a predetermined value.