JPH02260023A - Coordinate input device - Google Patents

Abstract

PURPOSE:To secure the highly accurate coordinate input position information despite the unsatisfactory linearity of the surface resistance of each coordinate input sheet and also to secure the high resolution even with use of an inexpensive 8-bit A/D converter by providing plural intermediate electrodes, a CPU, etc. CONSTITUTION:The intermediate electrodes 11a - 11c which are parallel to the counter electrodes 12 and 13 are provided on the sheet surfaces of surface resistances 1La and 1Lb of coordinate input sheets 10A and 10B. When a position is detected on the X/Y coordinates of an input point P, the analog signals of input points PX and PY to an A/D converter 22 are inputted via a switch connection circuit 19, a switch circuit 25, a differential amplifier 30, etc. A CPU 27 converts the analog signal amplified up to a proper voltage level by the amplifier 30 into a digital signal via the converter 22 to store and fetch it and carries out a prescribed arithmetic process to calculate the X/Y coordinate positions at the point P. As a result, the high reading accuracy is secured despite the unsatisfactory linearity of the surface resistance. Furthermore the information detecting ability is improved even with an inexpensive 8-bit A/D converter together with reduction of the cost.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of the Invention) The present invention relates to a so-called digitizer used for handwritten input of characters and figures, and in particular, to a coordinate input sheet when the tip of a special pen such as a stylus is brought into contact with the coordinate input sheet. The present invention relates to a coordinate input device for inputting the coordinate position of the contact point (hereinafter referred to as "input point").

(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 of the electrodes between the input points to each coordinate input sheet using one differential amplifier circuit. A peak hold circuit is provided to apply the voltage to the reference voltage terminal and hold the voltage value, thereby simplifying the circuit and providing highly accurate coordinate position information even if the linearity of the sheet resistor is not sufficient. Moreover, high resolution can be ensured with an A/D converter having an inexpensive configuration.

(Prior art and its problems) In the conventional coordinate input device, as shown in FIG. coordinate input sheet (hereinafter referred to as "X
A coordinate input sheet (hereinafter referred to as "coordinate input sheet") IA and a coordinate input sheet for detecting the Y coordinate position (hereinafter referred to as "Y coordinate input sheet") IB, which has 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 IA, I
When the tip of a special pen is brought into contact with the sheet surface while a predetermined voltage is applied to B, the partial pressure at input point P becomes the partial pressure output terminal 6.
．． 7 to analog-to-digital converter (hereinafter simply A/D)
The digital signal is read by a converter (referred to as a converter) and converted into a digital quantity, and this digital signal is output from an A/D converter as position information of X coordinates and Y coordinates.

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 LA 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 to ensuring the linearity of the resistance value of the sheet resistance 4.

Furthermore, 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 higher bit (for example, 10 bits or 10 bits). 12 bits, etc.), and it is necessary to adopt a complicated circuit configuration to handle a large amount 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 calculate the sheet resistance value on each coordinate input sheet provided in the coordinate input device. Even if linearity is not sufficient, the influence of noise etc. is prevented as much as possible, highly accurate coordinate position information can be obtained, and the circuit configuration is relatively simple.
An object of the present invention is to provide a coordinate input device that can ensure high reading accuracy even with a /D converter.

(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 coordinate input sheet for position detection of X and Y coordinates, in which a sheet resistance is formed on a sheet surface between 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. , Analog-digital exchange for accepting pen contact input to the coordinate input sheet while voltage is 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, a switching connection circuit for switching and connecting each electrode provided on each of the coordinate input sheets to the input terminal of the differential amplifier circuit, and One differential amplifier circuit that collects input signals, amplifies the input signal to an appropriate voltage level, and outputs it, and a peak hold circuit that holds the differential voltage input from the differential amplifier circuit. It is characterized by being composed of.

According to this invention, a coordinate input sheet for position detection is provided with a plurality of intermediate electrodes, and one differential amplifier circuit differentially amplifies the voltage of the electrodes that sandwich the input points to each coordinate input sheet. A peak hold circuit is provided to apply the voltage to the voltage terminal and hold the voltage value, thereby simplifying the circuit and allowing highly accurate coordinate position information to be obtained even if the linearity of the sheet resistor is not sufficient. , the circuit configuration can be relatively simplified, high resolution can be ensured even with an inexpensive 8-bit configuration A/D converter, and the influence of noise etc. can be prevented as much as possible, and the information detection ability has been improved overall.

This has effects such as cost reduction.

(Embodiment) Hereinafter, an embodiment of the coordinate human power device of the present invention will be described based on the drawings.

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

In the coordinate input device of the present invention, sheet resistances ILA and 14LB are formed on the sheet surface between the counter electrodes 12.13, and a plurality of intermediate electrodes 11a to 14LB are formed on the sheet surface of the sheet resistance portion parallel to the counter electrodes 12.13. The coordinate input sheets 10A and 10B for detecting the X and Y coordinate positions are provided with the coordinate input sheets IOA and IOB, and the pen contact input is accepted with voltage applied to the coordinate input sheets IOA and IOB, and the partial pressure at the input point is calculated. An A/D converter 22 for reading out positional information of X and Y coordinates, and a reference voltage terminal 23 of the A/D converter 22 for each electrode in the coordinate input sheets IOA and 10B.
and a switching connection circuit 19 for switching connection to the reference ground terminal 24, and amplifying the input voltage of the X-Y coordinates inputted from the switching connection circuit 19 to an appropriate level,
It is roughly composed of one differential amplifier 30, which is a differential amplifier circuit for outputting to the A/D converter 22, and a peak hold circuit 31 that holds the amplified voltage.

FIG. 1 shows a coordinate system according to a position embodiment of the present invention, which includes an X-coordinate input sheet IOA for detecting the X-coordinate position of an input point, and an X-coordinate input sheet IOA for detecting the Y-coordinate position of an input point. It is equipped with a Y coordinate input sheet 10B. Coordinate input sheets 10A and IOB are provided with opposing electrodes 12 and 13 at both ends of an insulating sheet, and sheet resistances ILA and ILB are formed on the sheet surface between the two electrodes. , IOB are positioned so that the opposing electrodes 12 and 13 are shifted by 90 degrees from each other, and are stacked one on top of the other.

In each of the above coordinate manual sheets IOA and IOB, resistance 1
A counter electrode 12.1 is provided in the effective area of 1A and IIB.
Intermediate electrodes 11a to 11lid in a straight line parallel to 3 are arranged at appropriate distance intervals.

In the illustrated example, four intermediate electrodes are provided, but the number is not limited to this, and the number may be two to three, or five or more.

Coordinate system (coordinate type) 10A, IOH counter electrode 12, respectively
．． A voltage E of about 3.5V is selectively applied between the terminals 13 and 13 via switches XH and YH.

The opposing electrodes 13 on the side of each coordinate input sheet IOA and IOB are provided with partial voltage output terminals YX and YL, and when the voltage E is applied to one coordinate input sheet 10A, the other coordinate input sheet IOB is The partial pressure at the input point P is extracted from the partial pressure output terminal YL of the input point P, and from the partial pressure output terminal XL of the other coordinate input sheet IOA when the voltage E is applied to the other coordinate input sheet 10B. become.

Opposing electrode 12 in each coordinate manual sheet IOA, IOB
．． 13 and intermediate electrodes 11a to 11d are connected to electrode terminals X.
o-X4. Yo-Y4 is pulled out and these electrode terminals
O” Given.

Figure 1 shows an input device that uses pen contact to input both coordinates.
0A indicates a state in which IOB is in contact. In particular, the figure shows the coordinate manual device as an equivalent circuit when the X-coordinate position information of the input point is extracted. p
y is the input point (pen contact point) for each coordinate input sheet IOA and IOB, and 8 is the contact resistance between the input points PX and PY.

FIG. 2 shows an example of the circuit configuration of the entire coordinate input device including the equivalent circuit of the coordinate input sheets 10A and 10B.
The switching connection circuits 19a to 19d on the X side and Y side, the switching circuits 25X and 25Y, the differential amplifier 30, and the peak
Hold circuit 31, A/D converter 22, and CPU 27
It is composed of and.

The switching connection circuit 19a on the X side is as shown in FIG.
Divide the electrode terminals Xo-X4 on the X-coordinate input sheet 10a into two parts. Second changeover switch XCH, XC
L and one selector switch XCH
is connected to the reference voltage terminal 23 of the A/D one ventilation via the switching circuit 25X, operating amplifier 30, and peak hold circuit 31, and the other switch YCH, YCL is connected to the switching circuit 25Y.
Operating amplifier 30. A via the peak hold circuit 31
/D piece ventilation 22 is connected to the reference ground terminal 24, respectively.

The switching circuit 25 selects one of the switching connection circuits 19a to 19d on the X side and the Y side, and compares the voltage (position information) thereof to an appropriate voltage level that is not affected by noise using the operational amplifier 30. and connects to the reference voltage terminal 23 and reference ground terminal 24 of the A/D converter 22.

The A/D converter 22 has a coordinate input unit 10A.

When there is a pen contact with 10B, each coordinate input box)
10A, the partial pressure at the input point at IOB is converted to A/D converter 2.
After inputting from the input terminal 25 of No. 2 and converting it from analog to digital, this digital signal 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. 1, the reference voltage terminal 23 of the A/D converter 22 has a voltage of one intermediate electrode 11a (electrode terminal is given as the reference voltage Vref, and the input point PY is shown at the reference ground terminal 24 of the A/D converter 22, and the voltage of the lower intermediate electrode 11b (electrode terminal X2) is given as the ground voltage. The resolution of the A/D converter 22 can be used within the section resolved by the intermediate electrodes 11a to 11d, and the reading accuracy is greatly improved.

Furthermore, 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 location information can be input to the CPU 27,
The control of the CPU 27, which will be described later, will also be highly accurate.

In addition, since the voltage value is held in the peak hold circuit 31, more accurate position information can be obtained.

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

FIG. 3 shows the coordinate creation flow of the coordinate input device. When the coordinate input sheets IOA and IOH are pressed with a special pen and an input point P is given, the CPU 27 detects the press, Each switch is turned on.

In other words, when only the switch 1YEs,
When YCH(7) voltage<3.4V(7), a correction electrode value is given.

Next, when XH and XL are ON, the reference voltage E is 3.5
V, the voltage of XCH selection is sequentially A/D converted, and CPU2
7, store Y, ~Y,.

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. Then, this voltage value is determined by the peak hold circuit 3.
It is held at 1.

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

...(1) Equation ) is converted into a digital signal by the A/D converter 22 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 operation amplifier 30. Since the peak hold circuit 31 replaces the voltage with an appropriate voltage level, it is possible to output coordinate position information with high precision resolution, and the differential amplifier 3
In addition to having a simple configuration using one 0, high reading accuracy can be ensured even with an A/D converter using an inexpensive 8-bit CPU 27, and overall the information detection ability of the coordinate input device can be improved and costs can be reduced. It has the effect of

[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 FIG. 2 is an explanatory diagram showing the configuration of an example coordinate input device. 10a, 10b...Coordinate input sheet 11a-11d...Intermediate electrode 12.13...Counter electrode ILA, ILB...Sheet resistance 19 (19a-19d)...Switching connection circuit 22...
・A/D converter 27...CPU 30...Differential amplifier (differential amplifier circuit) 31...Peak hold circuit P...Input point

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 electrode are arranged on the sheet surface of this sheet resistance portion. A coordinate input sheet for position detection, and with a voltage applied to this coordinate input sheet, pen contact input to the coordinate input sheet is accepted and the partial pressure at the input point of the pen is calculated as position information of the X and Y coordinates. an analog-to-digital switching circuit for reading out the data as a signal; 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 an input from the switching connection circuit. A differential amplifier circuit that collects input signals of X and Y coordinates, amplifies the input signals to an appropriate voltage level, and outputs the signals, and a differential voltage that is input from the differential amplifier circuit. A coordinate input device comprising: a peak hold circuit for holding.