JPH02260021A - Coordinate input device - Google Patents

Abstract

PURPOSE:To obtain the highly accurate coordinate input position information despite the unsatisfactory linearity of the surface resistance of a coordinate input sheet and also to secure the high resolution even with use of an inexpensive 8-bit A/D converter by providing a differential amplifier, a switch circuit, etc. CONSTITUTION:Plural intermediate electrodes are provided on the position detecting coordinate input sheets 10A and 10B, and the voltage of the electrodes sandwiching each input point to both sheets 10A and 10B is differentially amplified by a differential amplifier 30. This amplified voltage is applied to an analog input terminal. In other words, the amplifier 30 detects the voltage difference inputted from switch circuits 25X and 25Y and supplies this voltage difference to a reference voltage terminal 23 of an A/D converter 22 via a switch contact and a peak holding circuit as well as to the analog input terminal. As a result, the highly accurate coordinate input position information is obtained despite the unsatisfactory linearity of a surface resistor. At the same time, the high resolution is secured even with an inexpensive 8-bit A/D converter. As a result, the overall information detecting ability is improved at a low cost.

Description

[Detailed Description of the Invention] (Field of the Invention) The present invention relates to a so-called digitizer used for handwriting input of characters and figures, and in particular, the present invention relates to a so-called digitizer used for handwriting input of characters, figures, etc. The present invention relates to a coordinate input device for inputting the coordinate position of a contact point (hereinafter referred to as an "input point") by making contact.

(Summary of the Invention) This invention provides a plurality of intermediate electrodes on a coordinate input sheet for position detection, and differentially amplifies the voltage values of the electrodes between the input points to each coordinate input sheet using a differential amplifier circuit. Apply it to the reference voltage terminal, and immediately write and store the voltage value in the calculation means, and use the calculation means to calculate the coordinate value from the voltage value between the electrodes that sandwich the input point and the voltage value between the input point. Highly accurate coordinate position information can be obtained even if the linearity of the resistor is not sufficient, the circuit configuration is simplified, and high resolution can be ensured even with an inexpensive 8-bit A/D converter. This is what I did.

(Prior art and its problems) In the conventional coordinate input device, as shown in Fig. 4,
A coordinate input sheet for X-coordinate position detection (hereinafter referred to as "
A coordinate input sheet (hereinafter referred to as "X coordinate input sheet") IA and a coordinate input sheet for Y coordinate position detection (hereinafter referred to as "Y coordinate input sheet") IB having the same configuration as this X coordinate input sheet IA are shifted 90 degrees vertically. A polymerized product is used.

In this type of coordinate input device, each coordinate input sheet 1, IB
When the tip of a special pen is brought into contact with the sheet surface while a predetermined voltage is applied to the input point P, the partial pressure at the input point P becomes the partial pressure output terminal 6.
7 is read by an analog-to-digital converter (hereinafter simply referred to as an A/D converter) and converted into a digital quantity, and this digital signal is output from the A/D converter as each position information of the X coordinate and Y coordinate. It has become so.

However, in the coordinate input device having the above configuration, it is necessary to improve the printing accuracy of the sheet resistance 4 on each of the coordinate input sheets IA and IB so that the linearity of the resistance value is good. However, since the coordinate input sheets IA and IB are manufactured by silk screen printing, there is a certain limit in processing the linearity of the resistance value of the sheet resistance 4.

In addition, the A/D converter used is usually an 8-bit one, but in order to improve the reading accuracy (resolution) of coordinate position information, it is necessary to convert it to an even larger number of bits (for example, 10 or 12 bits). etc.) and have to deal with a lot of information. However, multi-bit A/D converters are expensive, which causes several problems, such as an increase in the manufacturing cost of the coordinate input device itself.

(Object of the Invention) This invention was made to solve the various problems mentioned above, and its purpose is to increase the surface resistance of each coordinate input sheet provided in the coordinate input device. Coordinate input that prevents the influence of noise as much as possible even when linearity is not sufficient, provides highly accurate coordinate position information, and ensures high reading accuracy even with an inexpensive 8-bit low capacity A/D converter. The goal is to provide equipment.

(Structure and Effects of the Invention) In order to achieve the above object, the coordinate input device of the present invention has the following features:
A sheet resistance is formed on the sheet surface between the opposing electrodes, and a plurality of intermediate electrodes parallel to the aforementioned opposing electrodes are arranged on the sheet surface of this sheet resistance portion.Coordinate input sheet for X-coordinate and Y-coordinate position detection device and an analog/digital controller for accepting pen contact input to the coordinate input sheet with voltage applied to the coordinate input sheet and reading out the partial pressure at the input point of the pen as position information of the X and Y coordinates. circuit replacement, a switching connection circuit for switching and connecting each electrode provided on each coordinate input sheet to the input terminal of the differential amplifier circuit, and a differential amplifier circuit for amplifying each differential input voltage to an appropriate level and outputting it to the analog/digital switching circuit; and a coordinate input device comprising: a voltage between electrodes sandwiching the input point; The present invention is characterized in that it includes a calculation means for calculating coordinate values from the voltage values of the points.

According to this invention, a coordinate input sheet for position detection is provided with a plurality of intermediate electrodes, and a differential amplifier circuit differentially amplifies the voltage of the electrodes that sandwich the input points to each coordinate input sheet, and the reference voltage terminal is and the voltage value is immediately written and stored in the calculation means, and the coordinate value is calculated by the calculation means from the ratio of the voltage value between the electrodes sandwiching the input point and the voltage value at the input point. Because of this, highly accurate coordinate position information can be obtained even if the linearity of the sheet resistor is not sufficient, the circuit can be simplified, and even an inexpensive 8-bit A/D converter can be used. High resolution can be ensured, and the effects of noise and the like are prevented as much as possible, resulting in overall improvements in information detection ability and cost reduction.

(Description of Embodiments) Hereinafter, position embodiments of the coordinate input device of the present invention will be described based on the drawings.

1 and 3 show an embodiment of the coordinate input device of the present invention.

In the coordinate input device of the present invention, sheet resistances ILA and ILB are formed on the sheet surface between the counter electrodes 12 and 13, and a plurality of intermediate electrodes 11a to 11a parallel to the sheet counter electrodes 12 and 13 in this sheet resistance portion are connected to each other. coordinate input sheets IOA and IOB for detecting the X coordinate and An A/D converter for reading out X coordinates and positional information of the A switching connection circuit 19 for switching connection, and a differential amplification for amplifying the input voltage of the X-X coordinate input from the switching connection circuit 19 to an appropriate level and outputting it to the A/D exchanger 22. One differential amplifier 30, which is a circuit, and a calculation means that immediately stores the amplified voltage value and calculates coordinate values from the ratio of the voltage value between the electrodes that sandwich the input point and the voltage value at the input point. It is roughly composed of a CPU 27 and a CPU 27.

FIG. 1 shows a coordinate input device according to a first embodiment of the present invention.
It includes a coordinate input sheet IOA and a Y coordinate input sheet B for detecting the X coordinate position of the input point P. Coordinate input sheets 10A and IOB each have electrodes 12 and 13 arranged opposite to each other at both ends of an insulating sheet, and sheet resistances ILA and ILB are formed on the sheet surface between the two electrodes. and IOA, IOB are the opposing electrodes 12°13
The sheets are positioned so that they are shifted 90 degrees from the other sheets, and are stacked one on top of the other.

In each of the above coordinate type horn sheets IOA and IOB, the effective area portion of the sheet resistance ILA and ILB includes intermediate electrodes 11a to ll which are on a straight line parallel to the counter electrode 12.13.
d are arranged at appropriate distance intervals. In the illustrated example, 4
Although a book of intermediate electrodes is provided, the present invention is not limited to this, and the number of intermediate electrodes may be two or three, or five or more.

Coordinate system (coordinate type) 10A, IOB counter electrode 12, respectively
．． 13, a voltage E of about 3.5 volts is applied to the selection system via switches XH and YH.

Negative side counter electrode 13 of each coordinate input sheet IOA, IOB
are provided with partial voltage output terminals YX and YL, and when the voltage E is applied to one coordinate input sheet 10A,
When the voltage E is applied from the partial voltage output terminal YL of the partner coordinate input sheet 10B to the other coordinate input sheet IOB, the voltage E is applied between the partial voltage output terminals X of the partner coordinate input sheet IOA.
From L, the partial pressure at the input point P is extracted. Each coordinate type box) 10A, counter electrode 12.13 in IOB and intermediate electrodes 11a to 11d to electrode terminals Xo-X4. Yo-Y4 is drawn out, and the voltages of these electrode terminals Xo-X, Yo-Y, are sent to the A/D via a switching connection circuit 19, a switching circuit 25, and a differential amplifier 30, which will be described later.
Reference voltage terminal 23 and reference ground terminal 24 of converter 22
given to.

Figure 1 shows the coordinate system (Kashi) 1 by input operation by touching the pen.
0A indicates a state in which IOB is in contact. In particular, the figure shows the coordinate input device as an equivalent circuit when the X-coordinate position information of the input point is extracted.
B is the sheet resistance of each coordinate formula IOA, IOB, Px
, Py are input points (surface contact points) for each coordinate input sheet IOA and IOB, and 28 is a contact resistance between input points Px and Py.

FIG. 2 shows an example of a circuit configuration of a coordinate input device including an equivalent circuit of the coordinate input sheets 10A and 10B. 25Y, differential amplifier 30 and A/D converter 2
2 and a CPU 27.

The switching connection circuit 19a on the X side is configured as shown in FIG.
Divide into two hands and divide into 1st. Second changeover switch XCH,X
Connected to CL, one selector switch XC
H connects the switching circuit 25X and the differential amplifier 30 to the reference voltage terminal 23 of the A/D converter 22, and connects the other switch YCH to the reference voltage terminal 23 of the A/D converter 22.
, YCL are connected to the reference ground voltage terminal 24 of the A/D converter 22 via a switching circuit 25Y.

The switching circuit 25 selects one of these X-side and Y-side switching connection circuits 19a to 19d, and uses a differential amplifier to set the voltage (position information) to an appropriate voltage level that is not affected by noise. Connected to the reference voltage terminal 23 and reference ground terminal 24 of the A/D converter 22.

The A/D converter 22 is the coordinate input sheet 10A.

10B, the suppression of the input point P on each coordinate input sheet 10A, 10B is input from the analog input terminal 25 of the A/D converter 22, and after analog-to-digital conversion, this digital signal is is output to the CPU 27 as position information of the X and Y coordinates. In this case, in the pen contact example shown in FIG.
One electrode 11a (electrode terminal
) is given as the reference voltage vRεF, and A/
The reference switch terminal 24 of the D converter 22 has an input point, py
is given as the voltage of the other electrode 11b (electrode terminal
The resolution can be utilized within the section divided by the intermediate electrodes 11a to 11d, and the reading accuracy is greatly improved.

In addition, since the position information of the input point P input via the switching circuits 25X and 25Y is boosted to an appropriate voltage level by the differential amplifier 30 and input to the A/D converter 22, accurate position information is obtained. can be input to the CPU 27, and the control of the CPU 27, which will be described later, will be more accurate.

The CPU 27 constitutes a microcomputer together with a memory, etc., and takes in the digital signal from the A/D converter 22, executes predetermined calculations and processing, and calculates the X-coordinate position and Y-coordinate position of the input point P. In addition to calculating
Each of the switching connection circuits 19a to 19d and the switching circuit 25X,
It has the function of controlling the operation of 25Y.

Then, the input voltage value of the A/D converter 22 is stored, and coordinate values are calculated from the ratio of the voltage value between the electrodes sandwiching the input point P and the voltage value at the input point.

FIG. 3 shows the coordinate creation flow of the coordinate input device. When the coordinate input sheet 10A and IOB are pressed with a special pen and an input point P is given, the CPU 27 detects the press and each The switch is turned on.

That is, when only switch XH is ON, YCH is selected, and when the voltage of YCH is 3.4v, YES,
A correction electrode value is given when the voltage <3.4V.

Next, when both XH and XL are ON, the reference voltage E is 3.5
In volts, the voltage value of the XCH selection is sequentially A/D converted, and the voltage value is immediately written to the CPU 27, and Y4 to Y1 are stored.

Then, when both XH and XL are ON, the voltage value of YCH is converted from analog to digital, and compared with a table of corrected electrode values of the CPU 27, and the CPU 27 determines which block it belongs to.

From the position information obtained in this way, the CPU
Calculate in 27.

...(1) Equation information) is converted into a digital signal by the A/D converter 22, stored and taken in, and the X-Y coordinate position of the input point P can be calculated by performing predetermined calculations and processing.

As is clear from the above, according to the present invention, even if the linearity of the sheet resistance in each coordinate input sheet is not sufficient, the differential amplifier 30 and CPU 27 replace it with an appropriate voltage level, so the peak hold It is possible to output coordinate position information with high precision resolution without using a voltage value holding means such as a circuit, and moreover, it is possible to output coordinate position information with high precision resolution without using a voltage value holding means such as a circuit.
Even an A/D converter using No. 7 can ensure high reading accuracy, and the overall effect is that the information detection ability of the coordinate input device can be improved and costs can be reduced.

[Brief explanation of drawings]

1 and 2 are electric circuit diagrams showing one embodiment of the coordinate input device of the present invention, FIG. 3 is a flow diagram showing coordinate creation in the case of one embodiment of the present invention, and FIG. 4 is a conventional example. FIG. 2 is an explanatory diagram showing the configuration of a coordinate input device. 10A, IOB...Coordinate input sheet 11A to 11D...Intermediate electrode 12.13...Counter electrode 14A, 14B...Sheet resistance 19 (19a to 19d)...Connection circuit 22...
・A/D converter 27...CPU 30...Differential amplifier (differential amplifier circuit) Patent applicant
Tateishi Electric Co., Ltd.

Claims (1)

[Claims] 1. A sheet resistance is formed on the sheet surface between the opposing electrodes, and a plurality of intermediate electrodes parallel to the opposing electrodes are arranged on the sheet surface of this sheet resistance portion at the X and Y coordinates. A coordinate input sheet for the position detection device, and with a voltage applied to the coordinate input sheet, accept pen contact input to the coordinate input sheet and calculate the partial pressure of the input point of the pen at the X and Y coordinate positions. An analog/digital circuit exchange for reading out information, a switching connection circuit for switching and connecting each electrode provided on each coordinate input sheet to the input terminal of the differential amplifier circuit, and from the above switching connection circuit. a differential amplifier circuit for amplifying each differential input voltage of the input X and Y coordinates to an appropriate level and outputting it to the analog/digital switching circuit; A coordinate input device comprising a calculation means for calculating coordinate values from the voltage between the electrodes and the voltage value at the input point.