JPH0441374B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention provides, for example, when characters or figures are drawn with a pen, the information of the orthogonal coordinate points of the pen's movement trajectory at any moment is converted into a current value or a voltage value. The present invention relates to a drawing tablet device that allows for drawing.

BACKGROUND ART AND PROBLEMS A drawing tablet device is known as a line drawing input device used to input line drawings such as handwritten characters and figures into a computer in real time or to transmit them to a terminal at the other end. This is when handwriting letters and figures on a tablet board with a pen, etc.
The character or graphic data is obtained as the X, Y orthogonal coordinates of the input point position on the tablet board of the pen, and the X, Y coordinates are obtained as current values or voltage values.

FIG. 1 shows an example of this type of tablet device. This is an example of a pressure-sensitive drawing tablet device that has a simple structure and is easy to use and inexpensive because an ordinary ballpoint pen or the like can be used as an input pen.

In the figure, 1 is an input sheet, 2 is a pressure-sensitive rubber conductive sheet, and 3 is a substrate. These sheets 1, 2, and the substrate 3 are stacked with an interval for explanation in the figure, but in reality, Closely attached. In this case, a plurality of electrode wires for configuring orthogonal X and Y coordinates are provided on the front and back sides of the pressure sensitive rubber sheet 2 so as to sandwich it therebetween. That is,
Between the input sheet 1 and the pressure-sensitive rubber sheet 2, a plurality of electrode wires Y ₀ , Y ₁ . _. .
The Y coordinate is configured by arranging the Y coordinate. On the other hand, a plurality of electrode wires X ₀ , X _{1 .} . . are placed between the pressure-sensitive rubber sheet 2 and the substrate 3 along the vertical direction Y of the input surface 1a.
X _n are arranged at equal intervals along the horizontal direction
Coordinates are constructed.

The input sheet 1 has elasticity, and when a thin paper is placed on the input surface 1a of the sheet 1 and a line is drawn on it with a ballpoint pen, the pressure applied to the pen tip is applied to the pressure-sensitive rubber through the sheet 1. as given to Sheet 2.

As shown in the characteristics of Figure 2, the pressure-sensitive conductive rubber sheet 2 has infinite resistance when no pressure is applied to it, and when a pressure of more than a certain value is applied to it in the thickness direction, the pressure It has a pressure-resistance characteristic such that the resistance in the thickness direction of the portion where the pressure is applied rapidly decreases. Therefore, when a line drawing is not drawn, the electrodes X ₀ - _{X n} and Y ₀ - _Yo are insulated, but when a line drawing is drawn, the resistance of the two parts of the sheet that are touching the pen is becomes low resistance due to pen pressure, and the electrode wires of that part of the electrode wires X ₀ to _{X n} and the electrode wires Y ₀ to _Yo are electrically connected through a resistor. be.

In this example, the coordinate position where pen pressure is applied is extracted as a voltage having a value corresponding to that position. That is, resistors 4 and 5 are provided whose resistance value is exactly proportional to their length. One end of the resistor 4 in the length direction is connected to the electrode wire _X0 , and the other end is connected to the electrode wire _Xn .
The area between this one end and the other end is divided into m equal parts, and electrode wires X ₁ to X _n-1 are sequentially connected to each of the equal division points. Similarly, electrode wires Y ₀ to _{Y o} are sequentially connected to the resistor 5 at equal intervals.

One end and the other end of the resistors 4 and 5 are connected to the inverting and non-inverting input terminals of the operational amplifiers 6 and 7, respectively, and one end of the resistor 4 receives a constant current I ₀ from the current source 8. is supplied, and one end of the resistor 5 is grounded. Then, an X-coordinate output SX is obtained from the amplifier 6 and is output to the output terminal 11, and a Y-coordinate output SY is obtained from the amplifier 7 and is output to the output terminal 12.

In addition, to avoid incorrect input, please use the pressure-sensitive rubber sheet 2.
The pen touch is detected by detecting whether pressure exceeding a certain value is applied to the sensor. A comparison circuit 9 consisting of an operational amplifier is provided for this purpose, and a detection output DP is outputted to a terminal 13 as its comparison output. One input terminal of this comparison circuit 9 is supplied with the voltage obtained at the connection point P between the current source 8 and one end of the resistor 4, and the other input terminal is supplied with the reference voltage ER for detection from the voltage source 10. Supplied.

An equivalent circuit of the device shown in FIG. 1 is shown in FIG. 3, and the operation of obtaining pen input as coordinate position information (voltage) will be explained with reference to FIG.

First, when there is no pen input, the resistance RP of the pressure-sensitive rubber sheet 2 is infinite, so no current flows through the resistors 4 and 5, and therefore no coordinate output is obtained. At this time, the potential at point P is the power supply voltage, which is greater than the reference voltage ER, so terminal 13
The signal obtained at is set to, for example, a low level, thereby preventing the coordinate outputs SX and SY from being supplied to, for example, a computer.

Next, let us now assume that pressure is being applied by the pen to the position indicated by the circle in FIG. 1, for example. If this pressure is 200 g or more, the resistance value RP of the pressure-sensitive rubber sheet 2 at this point rapidly decreases. Then, as shown by the broken line in FIG. 1, the current I ₀ from the current source 8 flows from one end of the resistor 4 to the intersection with the electrode wire X ₂ → electrode wire X ₂ → electrode wire Y ₂ → The current flows from the intersection of the resistor 5 with the electrode wire Y ₂ to one end → ground. Since the input impedance of amplifiers 6 and 7 is high, resistors 4 and 5
Almost no current flows from the point of intersection with the electrode lines X ₂ and Y ₂ to the other end of each. Therefore, the resistance value RX in the equivalent circuit of FIG. 3 is a value RX ₂ corresponding to the length from one end of the resistor ₄ to the intersection position with the electrode line A voltage of RX ₂・I ₀ is obtained.
Similarly, the resistance value RY is a value RY ₂ corresponding to the length from the intersection with the electrode wire Y ₂ of the resistor 5 to one end side, and the output terminal 12 is output as the Y coordinate output SY.
A voltage of RY ₂・I ₀ is obtained.

Also, at this time, a voltage of I ₀ (RX ₂ + RP + RY ₂ ) ...(1) is obtained at the connection point P, and as the resistance value RP decreases, this becomes lower than the reference voltage ER, so
A high level signal is obtained as a detection output DP at the output terminal 13, and it is detected that there is a pen touch.
As a result, the X and Y coordinate outputs SX and SY are input to, for example, a computer.

This pressure-sensitive drawing tablet device has the advantage of being easy to use because it can use a normal ballpoint pen as the input pen, but if a pressure of more than a certain value is applied to a point on the input surface using anything other than the pen, that point will be affected. Since coordinate values are output, if a pressure of a certain value or more is applied to multiple coordinate points at the same time, an error will occur in the original drawing coordinate output of the input pen. For example, when pressure is applied simultaneously to two points in the X direction, for example, the two intersections of electrode wire Y ₁ and electrode wires X ₁ and X ₄ , the current I ₀ is always at the input terminal of the current I ₀ of the resistor 4. It flows through a point close to the side, that is, the intersection of electrode lines X ₁ and Y ₁ , and if the correct input position is the intersection of electrode lines X ₄ and Y ₁ , the coordinate output will be incorrect. The same thing happens when pressure is input simultaneously at two points in the Y direction.

In this way, situations in which pressure is applied to multiple coordinate points at the same time are not limited to intentional cases, but often occur due to the habits of people with drawing skills, such as the habit of drawing with their fingernails raised.

Purpose of the Invention In view of the above points, this invention is designed to detect when there are two or more pressure points on the input surface in order to prevent obtaining erroneous coordinate outputs. It seeks to provide something.

Summary of the Invention This invention obtains the original X, Y coordinate outputs SX, SY, and obtains the X, Y coordinate outputs SX', SY' of the input point with the origin of the X, Y coordinates reversed.
Compare output SX, SY and output SX', SY' to detect whether output SX'= and output SY'=, and detect that there are two or more input points from the detected output. This is how it was done.

Embodiment FIG. 4 shows an embodiment of the device of the present invention, which uses the same pressure-sensitive tablet as the example in FIG. 2 and substrate 3 are omitted. Also,
In this example, unlike the example in Fig. 1, the constant current I ₀
is injected from the Y-coordinate resistor 5 side.

In this example, the switches S ₁ to _{S 6} set the starting point of the tablet coordinates to the intersection position O ₁ of the electrode lines X ₀ and Y ₀ (corresponding to the O point of the coordinates) and the intersection point of the electrode lines X _n and _Yo. This is a switch for inverting the position (corresponding to the maximum value point of the coordinates) to _O2 .

Further, 18 is an operational amplifier for forming a constant current _I0 , and the current _I0 is supplied to the resistor 5 side via the switch _S1 .

16 is an operational amplifier for obtaining the X coordinate output SX,
Reference numeral 17 is an operational amplifier for obtaining the Y coordinate output SY, and reference numeral 19 is a comparison circuit for detecting a pen touch.

In this example, under the control of the microcomputer 30, X, X,
Writes Y coordinate data to memory or prohibits writing. microcomputer 30
CPU31, ROM32, RAM for work area
33 and input/output ports 34 to 39,
It operates according to a program stored in the ROM 32, and the RAM 33 serves as a register for temporarily storing individual coordinate data and a memory for storing coordinate data.

The operation will be explained below with reference to the flowchart shown in FIG.

First, a switch switching signal is obtained from the port 34, whereby the switches _S1 to _S6 are switched to the state shown in the figure, that is, to the terminal A side (step [101]).

Then, the constant current I ₀ from the operational amplifier 18 flows through the switch S ₁ to one end side of the resistor 5 (electrode Y ₀ side).
Supplied from. Then, this current I ₀ flows from the resistor 5 from this one end to the Y-direction electrode line including the input pressure point → the Y-direction electrode wire → the pressure-sensitive rubber sheet portion of the input pressure point → the input pressure point. Including X-direction electrode wire → resistor 4 → one end side of resistor 4 (electrode wire X ₀ side)
→It passes through the path of switch _S2 and flows to ground via resistor 20. In other words, this corresponds to the case where the starting point of the coordinates is set at the intersection position O ₁ of the electrode lines X ₀ and Y ₀ .

In this case, if there are two or more input pressurizing points, the current I ₀ flows through the input point on the electrode line closest to the electrode line X ₀ and Y ₀ in the X and Y directions, that is, closest to the starting point O ₁ . .

Then, the amplifier 16 outputs the starting point of the coordinates.
The X coordinate output voltage SX of the input point with O ₁ is obtained,
From the amplifier 17, the starting point of the coordinates of the input point is O ₁
The Y coordinate output voltage SY is obtained. These output voltages SX and SY are output from A/D conversion circuits 21 and 2.
2 into digital signals DX and DY and then supplied to the data bus through ports 35 and 36.

At this time, the resistance change at the input point of the pressure-sensitive rubber sheet 2 is detected by the pen input in the comparator circuit 19, and the detection output DP is sent to the port 37.
is supplied to the data bus through the input terminal, and information about the presence of input is given. Then, data DX, DY are RAM
33 is temporarily stored at a predetermined address (step [102]).

When data DX and DY are stored, port 3
4, the switch S ₁ ~
_S6 is switched to the terminal B side (step [103]).
Then, when there is a pen input, the current I ₀ is the resistor 5
It flows into the vertical end side (electrode wire Y _o side), is taken out from the other end side (electrode wire X _n side) of the resistor 4, and flows through the switch S ₂ and the resistor 20 to the ground. Therefore, the origin of the coordinates is defined as the electrode line X _n
The _starting point of the _coordinates is reversed between the point O and the point of the maximum value.

Therefore, in this case, the amplifier 16 obtains the X coordinate output SX' of the input point with the starting point of the coordinates being _O2 ,
From the amplifier 16, the Y coordinate output SY' of the input point whose starting point is _O2 is obtained. And these outputs
SX' and SY' are converted into digital data DX' and DY' through A/D conversion circuits 21 and 22, and these data DX' and DY' are supplied to the data bus through ports 35 and 36, and are stored in predetermined locations in the RAM 33. Stored at the address (step [104]).

In this way, the stored data DX′, DY′ are
and the value that is the maximum resolution of A/D conversion of the Y coordinate output, that is, all “1” from LSB to MSB
is subtracted from the values DX _MAX and DY _MAX (step [105]). And its subtraction output DX'' and
DY'' is temporarily stored at another address in the RAM 33.

When the origin of the coordinates is O ₂ , the maximum value, that is
The position where all “1” from LSB to MSB is a point
Since O ₁ , the subtraction outputs DX″ and DY″ are
By calculation, the data DX′ and DY′ are set to the starting point of coordinates O ₁
It is converted to the value when .

Therefore, the data stored in RAM33
DX and DY are compared with the data DX'' and DY'' to determine whether they are the same (step [106]).

If there is only one input point, DX=DX'' and DY=DY''. However, if there are two or more input points, DX≠DY″ or
DY≠DY″.

This will be explained with reference to FIG. 6, which shows the coordinates as 4-bit digital information.

First, consider the case where there is only one input point _A1 .
The coordinate data DX, DY with the starting point as O ₁ are
DX = [0100] and DY = [0110], respectively. Also, the coordinate data DX′ with the starting point of this point A ₁ as O ₂ ,
DY′ becomes DX′=[1011] and DY′=[1001], as shown in parentheses in the figure. Therefore, DX″=DX _MAX −DX′=[1111]−[1011]=[0100] DY′=DY _MAX −DY′=[1111]−[0110] =[0110], and DX=DX″ , DY=DY″.

However, when there are two input points, point A ₁ and point A ₂ , the current I ₀ is
Coordinate data with the starting point as O ₁ because it flows through a point on the electrode line side close to the starting point O _{1 or O 2 ,} respectively.
DX, DY remain the coordinate data of the input point A ₁ , but the coordinate data DX′, whose starting point is O ₂ ,
DY′ becomes the coordinate data of input point _A2 , DX′=[1001], DY′=[1001], DX″=[1111]−[1001]=[0110], and DX=[0100] ]. Therefore, it is determined that there are two or more input points. Point A ₁
Since the Y coordinate is the same between and AN ₂ , DY=
DY", but if two points with different Y coordinates are input points, DY≠DY". However, the X coordinate, Y
If any of the coordinates are different, it means that there are two or more input points.

As described above, it is determined whether there are two or more input points, and if there is one input point, that is, if DX = DX'' and DY = DY'', the data DX and DY are It is stored in the RAM 33 as the coordinate data of the input point at the time (step [107]).

On the other hand, if there are two or more input points, that is,
If DX≠DX″ or DY≠DY″, the data
DX and DY are not written to the memory (step [108]), but an audio frequency signal, for example, is obtained through the port 38, which is supplied to the speaker 41 via the amplifier 40, and an alarm sound is emitted (step [109]). ).

When there is one input point and the data has been written to the RAM 33, the process returns to step [101], the above operations are repeated, and data at the coordinates of the next input point is loaded.

In addition, when detecting whether there are two input points, the data DX, DY of the coordinate origin O ₁ and the data DX', DY of the coordinate origin O ₂ are used without performing the calculation in step [105]. ′ may be compared directly. In other words, if the input is one point, DX′=, DY′=
It can be detected from the relationship DX・=0, DY・=0. In other words, calculate DX・DX′=K ₁ , DY・DY′=K ₂ , and if K ₁ = 0, K ₂ = 0, the input point is 1
point, and if K ₁ ≠ 0 or K ₂ ≠ 0, the input point is 2
It can be determined that the value is more than a point.

Note that the above detection is actually performed while drawing a line drawing on the input sheet surface with a pen, but the processing from step [101] to step [109] involves the pen input point moving between two electrode lines. There is no problem in terms of data processing speed, as it only needs to be done by the time the data is processed. However, if the data processing speed is slow,
Instead of detecting DX-DX"=0 and DY-DY"=0, if DX-DX"< _dX and DY-DY"< _dY , it is detected as one input point. Here, d _X and d _Y are, for example, the minimum value of coordinate change (difference in coordinate data of adjacent electrode lines). This is because when there are two input points, it is considered that the input points are almost never close to each other, and considering the maximum speed when writing a continuous line with a pen, _d It is sufficient to determine the value of d _Y.

Note that the line drawing coordinate data stored in the RAM 33 is read out when the line drawing input is completed, for example, when a display command is given, and is supplied to the display device via the port 39 or transmitted to the receiving side.

FIG. 7 shows another example of the device of this invention, which is also a pressure-sensitive tablet, but its structure is different.
That is, 51 is an input sheet, the entire back surface of which is an electrode. 52 is a pressure-sensitive conductive rubber sheet. Further, 53 is an electrode 53 on the peripheral part.
This is a resistance sheet in which electrodes 53a, 53b, 53c, and 53d are formed, and carbon 54 is evenly printed on the portion surrounded by the electrodes 53a to 53d. The diode is for backflow prevention.

The constant current I ₀ from the current source 55 is
1, and this input sheet 51
When pressure is applied from the surface, the electrode at the pressure point and the carbon 54 become electrically connected via the pressure-sensitive conductive rubber sheet 52. Then, in the resistance sheet 53,
A current is shunted to each electrode 53a to 53d, and from the pressure point to each peripheral electrode 53a, 53b, 53c, 5
A current is obtained from each of the peripheral electrodes 53a to 53d as a current value inversely proportional to the length up to 3d.

In this example, the X coordinate output and the Y coordinate output are taken out in a time-division manner. The switch _S9 is a switch for this purpose, and when this is switched to the terminal X, the current obtained from the electrodes 53a and 53b flows to the ground via the resistors 56 and 57 having the same resistance value, respectively. Therefore, voltages XA and XB proportional to the respective current values are obtained at the connection points between the resistors 56 and 57 and the peripheral electrodes 53a and 53b, but the voltage XA has the electrode 53b side as the origin of the X coordinate, The voltage XB is a value with the electrode 53a side as the starting point of the X coordinate. These voltages XA and XB are switched by switch _S8 for inverting the starting point, and
0 as the X coordinate output.

On the other hand, when the switch _S9 is switched to the terminal Y, the current obtained from the electrodes 53c and 53d flows to the ground via the resistors 58 and 59 having the same resistance value, respectively, and connects these resistors 58 and 59 and the peripheral electrode 53c. At the connection point with 53d and 53d, there is a voltage YA as a coordinate output with different starting points, respectively.
YB is obtained, which is switched by the switch _S7 and taken out from the amplifier 61. amplifier 60
and 61, the X and Y coordinate outputs are A/D, respectively.
The signal is converted into a digital signal by the conversion circuits 62 and 63, and is supplied to the microcomputer as in the example of FIG. 4, and the same control as in the example of FIG. 4 is performed.

In this example, first, switch S ₉ is set to
After switching to both terminals to obtain both X and Y coordinate outputs, switch S ₇ and S ₈ to invert the starting point of the coordinates, then switch S ₉ to both X and Y terminals to obtain both X and Y coordinates. Get the coordinate output, switch S ₇ and
By comparing the data before and after switching _S8 , it is detected whether there are two or more input points.

Note that the operational amplifier 64 constitutes a comparison circuit for pen-touch detection.

Note that the means for warning that there are two or more input points is not limited to an auditory means using sound, but may also be a visual means such as lighting an alarm lamp.

Effects of the Invention According to the present invention, while performing pen input, it is easily known that there are two or more input points and there is a possibility that erroneous data may have been input. Then, it can be detected that there are two or more input points by inverting the starting point of the coordinates and comparing the data before and after the inversion.
It is characterized by simple configuration.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining an example of a drawing tablet device, FIGS. 2 and 3 are diagrams for explaining the same, FIG. 4 is a block diagram of an example of this invention device,
5 and 6 are diagrams for explaining the same, and FIG. 7 is a block diagram of another example of the apparatus of the present invention. 1 is an input sheet, 2 is a pressure-sensitive conductive rubber sheet,
X ₀ -X _n and Y ₀ -Y _o are electrode lines in the X direction and Y direction, respectively, and S ₁ -S ₈ are switches for reversing the starting point of the coordinates.

Claims (1)

[Claims] 1. A device that expresses each of the X and Y coordinates of the input point position as a current value or a voltage value when the position of a drawing input point is expressed moment by moment using X coordinates and Y coordinates in mutually orthogonal directions, which Means for varying impedance by an input operation is provided between the X and Y coordinate points of the input point, and detects whether or not the input operation has been performed based on changes in voltage and current caused by changes in the impedance of the means, The X, Y coordinate outputs SX, SY of the above input point are obtained, and the maximum value position of the above X, Y coordinates is O.
The X and Y coordinate outputs SX' and SY' of the above input point are obtained with the origin of the coordinates reversed so that it becomes a point,
This coordinate output SX′, SY′ and the above coordinate output SX, SY
A drawing tablet device in which two or more input points are compared, and it is detected from the comparison output that there are two or more input points.