JPH09146686A - Input position detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce linearity error and to improve measurement accuracy by providing the storage means of ROM, RAM and flash memory, digitizing the output signal from the resistance film tablet of device with which an input position is detected, inputting and displaying that digitized signal onto a display part. SOLUTION: A ROM 10 is provided for storing a program code and according to the code in the ROM 10, a central operation processor 11 is controlled. That central operation processor 11 converts the analog position information of input point outputted from a resistance film tablet 14 to a digital value while using an A/D converter 16 and stores provided linear data in the work area of RAM 12. Further, the central operation processor 11 stores an approximate curve for position correction in the approximate curve for correction storage area of flash memory 13 and outputs the corrected position information stored according to a display part control program area onto a display part 18. Thus, linearity error is reduced and measurement accuracy can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tablet-based input position detecting device used in a portable information terminal device or the like.

[0002]

2. Description of the Related Art In recent years, with the increase and diversification of the amount of information managed by an individual, the number of consumers who purchase a portable information terminal device has increased, and it has been attracting attention in the market.

A portable information terminal device often adopts a handwritten character recognition system for easy input work as a user interface, and a resistive film tablet is generally used as a device for detecting an input position.

An input position detecting device according to the prior art will be described below. FIG. 11 is a hardware block diagram of an information terminal device having a conventional input position detecting device. In FIG. 11, reference numeral 1 is a ROM in which program codes are stored, and internally has a resistive film tablet control program area 1a, an A / D control program area 1b, and a display section control program area 1c.

Reference numeral 2 is a central processing unit (CPU) for controlling according to the code stored in the ROM 1, and 3 is a RAM which is a working area of the central processing unit 2 and has a working area 3a therein.

Reference numeral 4 is a resistance film tablet which is an input interface, 5 is a tablet control circuit for switching the X-axis and Y-axis measurement of the resistance film tablet 4, and 6 is an A for digitizing input position analog information from the resistance film tablet 4. /
A D converter, 7 is an A / D control circuit for controlling the operation of the A / D converter 6, 8 is a display unit such as an LCD, and 9 is a system bus.

The operation of the information terminal device having the conventional input position detecting device configured as described above will be described below.

FIG. 12 is a software flowchart of an input position detecting device using a conventional resistive film tablet.

First, when the power of the apparatus is turned on (step 1), the central processing unit 2 operates in accordance with the information in the resistive film tablet control program area 1a and the A / D control program area 1b, and the tablet control circuit 5 and the A / D control area. The register of the D control circuit 7 is set, and the input interrupt from the resistive film tablet 4 is set in a waiting state (step 2).

When an input is made to the resistive film tablet 4 and a pen input interrupt occurs in the central processing unit 2 (step 3), the central processing is performed in order to measure the X (Y) axis position of the input point. The device 2 sets the register of the tablet control circuit 5 so as to measure the X (Y) axis position of the input point according to the resistive film tablet control program area 1a. Then, the A / D converter 6 converts the X (Y) axis position analog information of the input point output from the resistive film tablet 4 into a digital value, and the central processing unit 2 performs R conversion.
The X (Y) axis position of the input point is stored in the work area 3a of AM3 (step 4).

Next, in order to measure the Y (X) axis position of the input point, the central processing unit 2 measures the Y (X) axis position of the input point according to the resistive film tablet control program area 1a. Set the register of the tablet control circuit 5 to Y of the input point output from the resistive film tablet 4.
The (X) axis position analog information is converted into a digital value by the A / D converter 6, and the central processing unit 2 stores the Y (X) axis position of the input point in the work area 3a of the RAM 3 (step 5). ).

Next, in order to measure the writing pressure at the input point, the central processing unit 2 sets the register of the tablet control circuit 5 so as to measure the writing pressure at the input point according to the resistive film tablet control program area 1a. I do. Then, the analog information of the writing pressure value of the input point output from the resistive film tablet 4 is converted into a digital value by the A / D converter 6, and the central processing unit 2 stores the input point in the work area 3 a of the RAM 3. The writing pressure value is stored (step 6), and the central processing unit 2 follows the display unit control program area 1c according to
The position information of the input point stored in the work area 3a of the RAM 3 is output to the display unit 8 (step 7).

The central processing unit 2 refers to the writing pressure value obtained in the writing pressure detection processing step 6 to judge whether the input to the resistive film tablet 4 is continued, and if the input is continued. The process of step 4 is performed, and if the input is completed, the process proceeds to the input interrupt waiting process step 2.

[0014]

However, in such a configuration, an error in the coordinates measured with respect to the input point occurs due to the linearity error due to the non-uniformity of the resistance film sheet of the resistance film tablet, and as a result, However, there is a problem that it causes deterioration of the recognition rate of handwritten characters.

Therefore, it is an object of the present invention to provide an input position detecting device capable of reducing the linearity error and improving the measurement accuracy.

[0016]

An input position detecting device according to the present invention is a ROM (first ROM) in which a program code is stored.
Memory unit), a central processing unit for controlling according to the code stored in the ROM, a RAM (second storage unit) which is a work area of the central processing unit, and an electrical writing and erasing of the program code. A flash memory (third storage means) capable of performing, a resistance film tablet that is a device that detects an input position, a tablet control circuit that controls the resistance film tablet, and an output signal from the resistance film tablet that is digitized A An A / D converter, an A / D control circuit for controlling the A / D converter, and a display unit for input and display are provided.

With the above structure, it is possible to reduce the linearity error caused by the nonuniformity of the resistance film sheet of the resistance film tablet and improve the measurement accuracy.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a hardware block diagram of an information terminal device having an input position detection device according to the first embodiment of the present invention.

In FIG. 1, reference numeral 10 is a ROM in which program codes are stored. Inside, a resistive film tablet control program area 10a, an A / D control program area 10b, a display section control program area 10d, and an approximate curve are provided. It has a calculation program area 10e and an input position correction program area 10f.

Reference numeral 11 denotes a central processing unit (CPU) for controlling according to a code stored in the ROM 10, 12
Is a RAM that is a work area of the central processing unit 11 and has a work area 12a inside.

Reference numeral 13 denotes a flash memory (Flash Memory) capable of being electrically written and erased,
It has a correction approximate curve storage area 13a inside.

Reference numeral 14 is a resistive film tablet which is an input interface, 15 is a tablet control circuit for switching the X-axis and Y-axis measurement of the resistive film tablet 14, and 16 is an A for digitizing analog information of the input position from the resistive film tablet 14. A / D converter, 17 is an A / D control circuit that controls the operation of the A / D converter 16, 18 is a display unit such as an LCD, and 19 is a system bus.

In FIG. 2, 20 is a resistance film sheet for X-axis measurement, and 20a and 20b are resistance film sheets 2 for X-axis measurement.
An electrode for applying voltage to 0, 21 is a resistance film sheet for Y-axis measurement, and 21a and 21b are resistance film sheets for Y-axis measurement 2
1 is an electrode for applying voltage, 22 is a DC power supply, and 23 is Y
It is an output voltage value from the resistance film sheet 21 for axis measurement,
The X-axis coordinate of the input point is shown.

The position analog information of the input point output from the resistive film tablet 14 is converted into a digital value by the A / D converter 16, and the central processing unit 11 converts the obtained linear data into the work area 12a of the RAM 12. To memorize.

The operation of the information terminal device having the input position detecting device using the resistance film tablet 14 configured as described above will be described below.

FIG. 3 is a software flowchart for calculating the position-correcting approximate curve of the input position detecting device according to the first embodiment of the present invention.

When the central processing unit 11 starts the operation according to the approximate curve calculation program area 10e (step 8), the user moves from point A to point B on the X (Y) axis of the resistive film tablet 14 as shown in FIG. A straight line is drawn in parallel along the line and the straight line is sampled (step 9).

Here, the data stored in the work area 12a is as shown by the solid curve 44 in FIG.

In FIG. 4, the X axis is the X of the input point.
The (Y) coordinate is shown, and the Y axis is the resistive film tablet 14.
Shows the output voltage value Eo from.

A straight line 45 indicated by a broken line is a theoretical straight line when there is no error, and the difference ΔE between the measured value 44 and the theoretical value 45 is ΔE.
46 is the linearity error of the resistive film tablet.

The central processing unit 11 converts the theoretical straight line 45 into a straight line of size 1 as shown by the straight line 47 in FIG.
Also transforms the curve 48 at the same ratio.

Then, the central processing unit 11 approximates the curve 48 as an approximate curve for position correction to an n-th order mathematical expression according to the approximate curve calculation program area 10e (step 10).

The general formula of the position correction approximate curve obtained in step 10 is shown in formula (1) below, and the curve according to this formula (1) is hereinafter referred to as position correction approximate curve A. X ′ = Σ (axi + b) (where i = 1, 2, ..., N, a, b are constants) (1) The central processing unit 11 approximates the position correction approximate curve A to the correction approximation of the flash memory 13. It is stored in the curve storage area 13a (step 11).

Next, the central processing unit 11 converts the measurement axis and performs the sampling process (step 12) of the Y (X) axis correction curve in the same manner as in the above X (Y) axis measurement, and Y
The (X) axis correction curve approximation processing (step 13) is performed, and equation (2) is used as the position correction approximation curve. Hereinafter, the curve according to the equation (2) will be referred to as the position correction approximate curve B. Y ′ = Σ (cyi + d) (where i = 1, 2, ..., N, c, d are constants) (2) The central processing unit 11 uses the position correction approximation curve B to correct the approximation of the flash memory 13. It is stored in the curve storage area 13a (step 14), and the central processing unit 11 terminates the correction approximate curve calculation program area 10e (step 15).

FIG. 6 is a software flowchart for measuring the input point coordinates of the input position detecting device using the resistive film tablet according to the first embodiment of the present invention.

First, when the power of the device is turned on (step 16), the central processing unit 11 causes the resistive film tablet control program area 10a and the A / D control program area 1 to operate.
0b, register setting of the tablet control circuit 15 and the A / D control circuit 17 is performed, and setting is made so as to wait for an input interrupt from the resistive film tablet 14 (step 17).

When an input is made to the resistive film tablet 14 and a pen input interrupt occurs in the central processing unit 11 (step 18), the central processing unit 11 is used to measure the X (Y) axis position of the input point. Sets the register of the tablet control circuit 15 so as to measure the X (Y) axis position of the input point according to the resistive film tablet control program area 10a. Then, the analog information of the X (Y) axis position of the input point output from the resistive film tablet 14 is A / D.
It is converted into a digital value by the converter 16, and the central processing unit 11 puts the X of the input point in the work area 12 a of the RAM 12.
The (Y) axis position is stored (step 19).

Next, in order to measure the Y (X) axis position of the input point, the central processing unit 11 measures the Y (X) axis position of the input point according to the resistive film tablet control program area 10a. Then, the register setting of the tablet control circuit 15 is performed. Then, the Y (X) axis position analog information of the input point output from the resistive film tablet 14 is A / D.
It is converted into a digital value by the converter 16, and the central processing unit 11 stores the Y of the input point in the work area 12a of the RAM 12.
The (X) axis position is stored (step 20).

Next, in order to measure the writing pressure at the input point, the central processing unit 11 sets the register of the tablet control circuit 15 so as to measure the writing pressure at the input point according to the resistive film tablet control program area 10a. The analog information of the writing pressure value of the input point output from the resistive film tablet 14 is converted into a digital value by the A / D converter 16,
The central processing unit 11 stores the writing pressure value at the input point in the work area 12a of the RAM 12 (step 21).

The coordinates of the input point measured in step 19 and step 20 will be referred to as (X, Y) below.

Now, the central processing unit 11 corrects the coordinates according to the input position correction program area 10f in order to remove the linearity error, and stores it in the work area 12a of the RAM 12 (step 22). The coordinates after the input position correction is X = X / (Σ (axi + b)), Y = Y
/ (Σ (cyi + d)).

The central processing unit 11 operates the work area 12 of the RAM 12 according to the display control program area 10d.
The corrected position information of the input point stored in a is displayed on the display unit 1.
8 (step 23).

Then, the central processing unit 11 refers to the writing pressure value obtained in the writing pressure detection processing step 21, judges whether or not the input is continued to the resistive film tablet 14, and the input is continued. If so, the X (Y) axis position measuring process step 19 is performed, and if the input is completed, the process proceeds to the input interrupt waiting process step 17.

(Second Embodiment) The second embodiment of the present invention will be described below.
An embodiment will be described with reference to the drawings.

FIG. 7 is a hardware block diagram of an information terminal device having an input position detecting device according to the second embodiment of the present invention.

In FIG. 7, reference numeral 30 is a ROM in which a program code is stored. Inside, a resistance film tablet control program area 10a, an A / D control program area 10b, a display section control program area 10d, and an approximate curve are provided. It has a calculation program area 10e and an input position correction program area 10f.

Reference numeral 31 is a central processing unit for controlling according to the code stored in the ROM 30, reference numeral 32 is a RAM which is a working area of the central processing unit 31, and has a working area 32a inside.

A flash memory 33 is an electrically writable and erasable flash memory, and has a correction approximate curve table storage area 13a therein.

Reference numeral 34 is a resistance film tablet which is an input interface, 35 is a tablet control circuit for switching the X-axis and Y-axis measurement of the resistance film tablet 34, and 36 is A for digitizing the input position analog information from the resistance film tablet 34. A / D converter, 37 is an A / D control circuit for controlling the operation of the A / D converter 36, 38 is a display unit such as an LCD, and 39 is a system bus.

In FIG. 8, 40 is a resistance film sheet for X-axis measurement, and 40a and 40b are resistance film sheets 4 for X-axis measurement.
An electrode for applying voltage to 0, 41 is a resistance film sheet for Y-axis measurement, and 41a and 41b are resistance film sheets 4 for Y-axis measurement.
1 is an electrode for applying voltage, 42 is a DC power supply, 43 is Y
It is an output voltage value from the resistance film sheet 41 for axis measurement,
The X-axis coordinate of the input point is shown.

The position analog information of the input point output from the resistive film tablet 34 is converted into a digital value by the A / D converter 36, and the central processing unit 31 converts the obtained linear data into the work area 32a of the RAM 32. To memorize.

Here, the data stored in the work area 32a is as shown by the solid curve 44 in FIG.

The operation of the information terminal device having the input position detecting device using the resistance film tablet 34 configured as described above will be described below.

FIG. 9 is a software flowchart for calculating the approximate curve for position correction of the input position detecting device according to the second embodiment of the present invention.

First, when the central processing unit 31 starts the operation according to the approximate curve calculation program area 10e (step 24), the user points from point A to point B as shown in FIG.
A straight line is drawn in parallel along the X (Y) axis of the resistive film tablet 34 until the straight line is sampled (step 2).
5).

The central processing unit 31 approximates the curve 48 to the mathematical expression of the n-th order curve as the position correction approximate curve according to the approximate curve calculation program area 10e (step 2).
6).

The general formula of the approximate curve for position correction obtained in step 26 is shown in formula (3), and this formula (3) is shown below.
The curve according to is referred to as an approximate curve C for position correction. X ′ = Σ (exi + f) (where i = 1, 2, ..., N, e, f are constants) (3) The central processing unit 31 uses the position correction approximation curve C to correct the approximation of the flash memory 33. Curve table storage area 1
It is stored in 3a together with the coordinates of the Y (X) axis of the position correction approximate curve C (step 27).

The central processing unit 31 asks the user whether to sample the correction curve along the X (Y) axis again according to the approximate curve calculation program area 10e (step 28), and if sampling is performed again, the step 25
Returning to the above processing, sampling is performed at a position shifted in parallel with AB as in CD in FIG.

If the sampling is not performed again, the central processing unit 31 converts the measurement axis and performs the sampling process of the Y (X) axis correction curve (step 29) as in the case of the X (Y) axis measurement. Then, the Y (X) axis correction curve approximation processing (step 30) is performed, and the equation (4) is used as the position correction approximation curve D. Y ′ = Σ (gxi + h) (where i = 1, 2, ..., N, g, h are constants) (4) The central processing unit 31 uses the approximate curve region D for approximation correction for correction of the flash memory 33. The approximate curve table storage area 13a is stored with the X (Y) coordinates of the approximate curve D for position correction (step 31).

The central processing unit 31 asks the user if the correction curve should be sampled again along the Y (X) axis in accordance with the approximate curve calculation program area 10e (step 32). Step two
Returning to the processing of step 5, sampling is performed at a position shifted in parallel with AB as in CD in FIG.

If the sampling is not performed again, the central processing unit 31 determines the approximate curve calculation program area 10e.
Is finished (step 33).

FIG. 10 is a software flowchart for measuring the input point coordinates of the input position detecting device according to the second embodiment of the present invention.

First, when the power of the device is turned on (step 34), the central processing unit 31 causes the resistive film tablet control program area 10a and the A / D control program area 1 to operate.
0b, register setting of the tablet control circuit 35 and the A / D control circuit 37 is performed, and setting is made so as to wait for an input interrupt from the resistive film tablet 34 (step 35).

When an input is made to the resistance film tablet 34 and a pen input interrupt occurs in the central processing unit 31 (step 36), the central processing unit 31 is used to measure the X (Y) axis position of the input point. Sets the register of the tablet control circuit 35 so as to measure the X (Y) axis position of the input point according to the resistive film tablet control program area 10a. Then, the analog information of the X (Y) axis position of the input point output from the resistive film tablet 34 is A / D.
It is converted into a digital value by the converter 36, and the central processing unit 31 puts the X of the input point in the work area 32a of the RAM 32.
The (Y) axis position is stored (step 37).

Next, in order to measure the Y (X) axis position of the input point, the central processing unit 31 measures the Y (X) axis position of the input point according to the resistive film tablet control program area 10a. Register setting of the tablet control circuit 35 is performed. Then, the Y (X) axis position analog information of the input point output from the resistive film tablet 34 is converted into a digital value by the A / D converter 36, and the central processing unit 31 inputs it into the work area 32 a of the RAM 32. Dot Y
The (X) axis position is stored (step 38).

Next, in order to measure the writing pressure at the input point, the central processing unit 31 sets the register setting of the tablet control circuit 35 so as to measure the writing pressure at the input point according to the resistive film tablet control program area 10a. Then, the analog information of the writing pressure value of the input point output from the resistive film tablet 34 is converted into a digital value by the A / D converter 36, and the central processing unit 31 stores the input point in the work area 32a of the RAM 32. The writing pressure value is stored (step 39).

The central processing unit 31 uses the input point coordinates 42.
The optimum position correction approximate curve for correction is selected from the correction approximate curve table storage area 13a of the flash memory 33 (step 40), and the central processing unit 31 follows the input position correction program area 10f to determine the linearity error in the coordinates. In order to remove the above, the correction is performed by the optimum approximate curve for position correction and is stored in the work area 32a of the RAM 32 (step 41).

The coordinates after the correction of the input position are as follows. X = X / (Σ (exi + f)), Y = Y / (Σ (gyi
+ H)) The central processing unit 31 has a display unit control program area 1
According to 0d, the corrected position information of the input point stored in the work area 32a of the RAM 32 is output to the display unit 38 (step 42).

The central processing unit 31 refers to the writing pressure value obtained in the writing pressure detection processing step 39, judges whether or not the input is continued to the resistive film tablet 34, and if the input is continued. The X (Y) axis position measurement processing step 37 is performed, and if the input is completed, the process proceeds to the input interrupt waiting processing step 35.

[0070]

According to the present invention, in the input position detection using the resistance film tablet, the linearity error is reduced and the measurement accuracy is improved. Therefore, the handwriting character recognition rate can be improved when handwriting character recognition or the like is input from the resistive film tablet.

[Brief description of the drawings]

FIG. 1 is a hardware block diagram of an information terminal device having an input position detection device according to a first embodiment of the present invention.

FIG. 2 is a hardware block diagram of a resistive tablet when measuring input point coordinates according to the first embodiment of the present invention.

FIG. 3 is a software flowchart for calculating an approximate curve for position correction of the input position detecting device according to the first embodiment of the present invention.

FIG. 4 is a diagram showing a linearity error of a resistive film tablet.

FIG. 5 is a diagram showing an approximate curve for position correction.

FIG. 6 is a software flowchart when measuring input point coordinates of the input position detection device using the resistive film tablet according to the first embodiment of the present invention.

FIG. 7 is a hardware block diagram of an information terminal device having an input position detection device according to the second embodiment of the present invention.

FIG. 8 is a hardware block diagram of a resistive tablet when measuring input point coordinates according to the second embodiment of the present invention.

FIG. 9 is a software flowchart when calculating an approximate curve for position correction of the input position detection device according to the second embodiment of the present invention.

FIG. 10 is a software flowchart for measuring input point coordinates of the input position detecting device according to the second embodiment of the present invention.

FIG. 11 is a hardware block diagram of an information terminal device having a conventional input position detection device.

FIG. 12 is a software flowchart of an input position detection device using a conventional resistive film tablet.

[Explanation of symbols]

 10 ROM 10a Resistive film tablet control program area 10b A / D control program area 10d Display control program area 10e Approximate curve calculation program area 10f Input position correction program area 11 Central processing unit (CPU) 12 RAM 12a Working area 13 Flash memory 13a Correction approximate curve storage area 14 Resistive film tablet 15 Tablet control circuit 16 A / D converter 17 A / D control circuit 18 Display unit

Claims (3)

[Claims] 1. A first storage means for storing a program code, a central processing unit for controlling according to a code stored in the first storage means, and a work area of the central processing unit. A certain second storage means, a third storage means capable of electrically writing and erasing the program code, a tablet for detecting an input position, a tablet control circuit for controlling the tablet, and an output signal from the tablet. An input position detecting device, comprising: an A / D converter for digitizing the above, an A / D control circuit for controlling the A / D converter, and a display unit for input and display. 2. A linearity error of the tablet is measured in advance by having an approximate curve calculation program area and an input position correction program area inside the first storage means, and an approximate curve of the obtained measurement data is calculated. Then, the calculated approximate curve is stored as the approximate curve for position correction in the third storage means, and thereafter, the input position signal from the tablet is corrected by the approximate curve for position correction. 1. The input position detection device according to 1. 3. An approximate curve calculation program area and an input position correction program area are provided in the first storage means so that the linearity error of the tablet is shifted in advance for each of the X and Y axes in parallel. Measurement is performed, an approximate curve is calculated for each measurement data, the calculated approximate curve is stored in the third storage means as an approximate curve for position correction, and the position information of each approximate curve for position correction is also the third. And stores the input position signal from the tablet from the plurality of position correction approximate curves stored in the third storage unit to the optimum position correction approximate curve closest to the input position. 2. The input position detecting device according to claim 1, wherein the input position detecting device corrects by using the optimum approximate curve for position correction.