JPH01280823A - Coordinate input device - Google Patents

Abstract

PURPOSE:To improve dynamic detecting ability by subtracting the potential of a detecting electrode set right before or after application of a scan pulse from the value of an electrostatic induction pulse produced at that time point. CONSTITUTION:Electrode lines (x) and (y) are arranged at prescribed intervals in the X and Y directions orthogonal to each other on a coordinate input panel 1. The potentials of a detecting electrode 5 are detected right before and after the scan pulses are successively applied to the lines (x) and (y). Then said potential value is subtracted from the value of an electrostatic induction pulse produced with application of the scan pulse. The result of this subtraction is defined as the original value of electrostatic induction. Then the pointed coordinates are calculated based on the value of said electrostatic induction. Thus it is possible to eliminate the influence of a noise voltage produced in accordance with the shift of a coordinate input means and to decrease the errors. Then the dynamic detecting ability is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a coordinate input device, and more particularly, to an improvement in the number of coordinate calculations when moving a coordinate indicating means in a capacitively coupled coordinate input device.

"Prior Art" In a capacitive coupling type coordinate input device, electrode wires are arranged at a predetermined interval in two orthogonal directions on a coordinate input board, and electrode wires are placed at a desired position on the coordinate input board. A detection electrode is provided on a coordinate indicating means such as an input pen or a cursor that is brought into contact to input coordinates. Then, scanning pulses are sequentially applied to the electrode wires, and at this time, the induced pulses generated on the detection electrodes by electrostatic induction are amplified, digitally converted, and supplied to calculation means consisting of a microcomputer, which calculates the Based on the magnitude of the induced pulse, the contact position of the coordinate indicating means at that time is calculated.

(For the calculation procedure, see Japanese Patent Publication No. 53-19380,
See Tokuken Sho 59-37679, etc. ) ``Problem to be solved by the invention'' By the way, in recent years, various systems and programs related to graphic processing have been developed, and in connection with this, for example, the trajectory of the coordinate indicating means when inputting handwriting or signature is more detailed. Regarding coordinate input devices, the number of times coordinate detection can be performed per second when moving (sliding) the coordinate indicating means on the coordinate input panel has become an issue. (Hereinafter, this ability will be referred to as "dynamic detection ability.") Regarding this dynamic detection ability, the applicant company evaluated its capacitive coupling type coordinate input device and found that:
For example, when the coordinate indicating means (hereinafter referred to as "input pen") is stationary at an appropriate position on the coordinate input board, and the number of detections per second is set as an index of 100,
It was found that when the input pen was moved in a circular motion at a speed of 1.75 m/s, the number of detections decreased to an index of 2 to 3 per second.

As a result of various studies on the cause of this, it was discovered that when the input pen slides, a noise voltage of about several hundred to several kilohertz is superimposed on the induced pulse generated in the input pen detection electrode. For this reason, when performing a data check, that is, when detecting signals at the same position multiple times and calculating coordinate data based on each, and confirming that they are the same, each time that should originally match, The coordinate data is
-M was not performed, and it was treated as an error, and as a result, it was found that the dynamic detection ability was degraded.

It is not clear why the noise voltage increases when the input pen is slid, but the main causes are (1) There are slight irregularities on the input panel, and the detection electrodes of the input pen vibrate up and down when sliding. As a result, the capacitance between the detection electrode and the electrode wire of the coordinate input panel fluctuates, and at this time, the impedance of the circuit is high and the charge stored in the 'y'l bottle wire and the detection electrode is Since there is no change, it is thought that noise with a frequency corresponding to the change is generated instead. (2)
One possible reason is that as the detection electrode moves up and down, a spring or the like that biases the detection electrode expands and contracts, and a voltage is generated due to a piezoelectric phenomenon.

"Means for Solving the Problems" Therefore, in the present invention, based on the above analysis results, detection is performed immediately before and/or after applying a scanning pulse to the electrode wire. l1if-1
Detect the potential of , subtract this potential from the magnitude of the electrostatic induction pulse generated by applying the scanning pulse, and assume that the magnitude after subtraction is the original magnitude of electrostatic induction. The designated coordinates will be calculated based on the specified coordinates.

``Effect'' In other words, the potential of the detection electrode when no scanning pulse is applied is:
Is it the noise voltage itself that occurs as the input pen moves, and therefore is it detected immediately before and/or after the scanning pulse is applied? If the potential of l is subtracted from the magnitude of the electrostatic induction pulse generated at that time, the magnitude of the electrostatic induction pulse after the subtraction represents the original value regarding the position of the coordinate indicating means at that time,
Using this, you can obtain correct coordinate data.

``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) 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 T'Fi polar lines X and y mentioned above in accordance with an address signal AD supplied from the central processing unit 3; The central processing unit 3 will be hereinafter referred to as rcPUJ, and in the following description, where a nickname is given in parentheses after the name, the abbreviation will be used hereinafter.

Reference numeral 4 represents an input pen serving as a coordinate indicating means, and reference numeral 5 represents a detection electrode movably 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. Reference numeral 7 denotes a superimposed amplifier that amplifies the electrostatic induction pulse generated at the detection electrode 5. Reference numeral 9 denotes a sample and 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 (electrostatic induction pulse voltage) at that point in time for a while. '11 is an analog-to-digital converter (AD
converter) converts the output voltage of the sample and hold circuit 9 into digital in response to the same read pulse RP. Note that the sample hold circuit 9 is connected to this AD converter 11.
is used to hold the electrostatically induced pulsed voltage for the time required for digital conversion.

The CPU 3 is a so-called microcomputer with a proven circuit, and has a read-only memory (■RI○N・1)12
A predetermined process is executed using a random access memory (RAM) 13 according to a program stored in the memory.

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

FIG. 2 shows the coordinate input panel 1 cut along a vertical plane including the electrode wires yi in the Y direction and partially taken out, with the electrode wires xi=xi+4 extending in the X direction.

These electrode wires xi"xi+4 and yi are connected to the insulating sheet 21
The upper and lower surfaces are formed by silk printing using conductive ink, and on top of these, protective resin layers 22 and 2 are formed.
3 is formed.

An example of an electrostatic induction 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 Figure 3. In the figure, pulse 5xi-
Sxi+4 is an electrostatic induction pulse generated when a scanning pulse is applied to each electrode line X1=xi+4.

Furthermore, the detection electrode 5 of the input pen 4 is brought into contact with the resin layer 22 and moved in a desired direction, and when the detection electrode 5 is at the position shown in FIG. 2, a scanning pulse is applied to each electrode line xi=xi+4. Electrostatic induction pulse Dxi-D when applying
xi+4 is shown in FIG.

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 layer 22, so strictly speaking,
The position of the detection electrode 5 when scanning the electrode line xi+4 is not at the position shown in FIG. However, the time during which the microcomputer applies the scanning pulse to each of the electrode lines xi to xi+4 is short, and the distance that the detection electrode 5 moves during that time is also very short. Therefore, in practice, the distance between the detection electrode 5 and each electrode axi-xj+4 does not change at this point, and each electrostatic induction pulse D generated in the detection electrode 5
xi= Height of Dxi+4 HDi-HDi+4
teeth.

The instantaneous value of the noise NW occurring at the detection electrode 5 at each point in time is expressed as HN
Each pulse HSi to H3i in Fig. 3 is applied to i-HNi+4.
+4 are superimposed on each other.

Therefore, in the present invention, each electrostatic induction pulse HDi=HDi+4 obtained including noise is y1 the noise H
After removing Ni, the original electrostatic induction pulse HS i ”H
The purpose is to obtain S i+4.

That is, the CPU 3 detects the input pen 4 @ the pole 5 is made of resin M22.
When the switch signal SW arrives, a read pulse R is first applied to the sample hold 9 and the AD converter 11.
P, and the instantaneous value of the noise NW at that time, for example, HNi
A digital value indicating this 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.

Next, the CPU 3 reads the aforementioned instantaneous value HNi from the RAM 13, subtracts the value HNi from the value of the electrostatic induction pulse HDi in the register to obtain a digital value representing the original electrostatic induction pulse H5i, and stores this in the RAM 13. .

Then, the CPU 3 executes such operations for the necessary range of electrode wires X to obtain, for example, HDi to HDi+4. Specify the instantaneous X coordinate of the detection electrode 5.

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 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 amount of movement of the detection electrode 5 during that time is It is also conceivable that this may appear as a difference in data. In this case, consider that the purpose of the process of comparing data taken at the same location is to prevent the output of coordinate data that is far from the indicated location due to noise. However, if the difference in the coordinate data is within a predetermined value, it is assumed that the coordinate data is correct, for example, 2 times 11 + 1? ! All you have to do is output the data.

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 it is better to stop the data comparison and just send out all the noise. Improved dynamic detection ability
- I can do things.

"Other Examples" Another example is shown in FIG. In this embodiment, the average of the noise voltages immediately before and after the application of the scanning pulse (16) is subtracted from the magnitude of the electrostatic induction pulse when the scanning pulse is applied, and this is used as the basis for single-press detection. are given the same reference numerals and their explanations will be omitted.

In the figure, 31 and 32 are the same sample and hold circuits as 9, which hold the instantaneous value of the output of the preamplifier 7 at that time in response to the read pulse RP.

33 is an operational amplifier, a resistor 34 (resistance value R) is connected between the input terminals, and a resistor 34.35 (resistance value R) is connected to the input terminal.
sample and hold circuits 31 .
32 outputs are provided.

37 is a differential amplifier, the output of the operational amplifier 33 is supplied to the inverting side input terminal (-), and the output of the sample hold circuit 9 is supplied to the non-inverting side input terminal (+), and the output is supplied to the inverting side input terminal (+). It is supplied to the same analog-to-digital converter 11 as in the example.

In this embodiment, when scanning each electrode X or y, C
The PU 3 first supplies a read pulse RP to the sample hold circuit 31 to cause the circuit 31 to hold the output of the preamplifier 7 at that time. The instantaneous value held here is the magnitude of the noise just before the scanning pulse is applied, for example, the 4th HN i
Represents +3.

Next, the CPU 3 sends the address signal A to the decoder driver 2.
At the same time, a read pulse RP is supplied to the sample and hold circuit 9, and the magnitude of the electrostatic induction pulse at that time is 1, for example, HD i + in FIG. 4. Let me hold 3.

Next, the CPU 3 supplies RP to the sample and hold circuit 32 and causes the circuit 32 to hold the output of the preamplifier 7 at that time. The instantaneous value held here represents the magnitude of the noise immediately after the application of the scanning pulse, for example HNi+3b in FIG. 4.

The operational amplifier 33 and the resistors 34 to 36 constitute an arithmetic averaging circuit, and the output of the operational amplifier 33 is the instantaneous value of the noise voltage held in the sample and hold circuits 31 and 32 immediately before and after the application of the scanning pulse. Shows average value. For example, if the instantaneous values of the miscellaneous H@pressure are the aforementioned HNi+3 and HNi+3b, the output of the operational amplifier 33 at this time will be the average value HNi+3a (see FIG. 4).

Then, in the differential amplifier 37, this average value HNi+3a is subtracted from the height of the electrostatic induction pulse at that time held in the sample and hold circuit 9, for example HDi+3, and the original electrostatic induction pulse size is reduced, that is, the height of the electrostatic induction pulse mentioned above. According to the example, the value corresponding to H'Si+3 in FIG.
appears as the output of

The subsequent flow is the same as in the previous embodiment, and the CPU 3 calculates the coordinates at that time based on the magnitude of the original electrostatic induction pulse obtained in this manner.

Although the embodiment described here has more circuit blocking than the above-mentioned embodiment, since noise components are directly removed, the number of coordinate detections can be increased.

"Effects of the Invention" As explained above, according to the present invention, it is possible to cancel the influence of noise voltage generated due to movement of the coordinate input means, reduce error occurrence, and improve dynamic detection ability. be able to.

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, 4th
The figure is a waveform diagram showing an example of electrostatic induction pulses at a certain point during movement of the input pen, and FIG. 5 is a block diagram showing another embodiment. ]... Coordinate input panel, 3, 12.13... Coordinate calculation means, 4...
Coordinate indicating means, 5...detection electrode, HD...
...Electrostatic induction pulse including noise, HN...
Noise potential due to movement of coordinate indicating means, T-(S...
・Electrostatic induction pulse X, y after subtraction...electrode wire. Patent applicant Pentel Co., Ltd. Figure 2 AH industry input signal section

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. , subtract the potential of the detection electrode immediately before and/or immediately after applying the scanning pulse from the magnitude of the electrostatic induction pulse generated in the detection electrode, and calculate the appropriate potential based on the magnitude of the electrostatic induction pulse after the subtraction. A coordinate input device characterized by comprising a coordinate calculation means for calculating contact position coordinates.