JP2001209485A - Coordinate digitizer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coordinate digitizer capable of accurately reading the coordinate of a loop coil end without changing the composition of the loop coil. SOLUTION: A loop coil 23, a receiving part of an electronic board, includes a X coil group and a Y coil group, and is disposed so that its edge part will not overlap with the coil groups. X coil group, including X coils X1, X2, X3... which are slim in the Y direction, can be magnetically coupled with the alternating field of a pen, and are parallely laid respectively along the X direction so that adjoining X coils will overlap. Y coil group, including Y coils Y1, Y2, Y3... which are slim in the X direction, are parallely laid respectively along the Y direction so that adjoining Y coils will partly overlap. The coordinates in boarder parts BDx, BDy and edge parts Egx, Egy can be read by executing different processes required in the following cases: the case when the pen is located in boarder parts BDx, BDy; the case when the pen is located in edge parts Egx, Egy; and the other cases.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coordinate reading device capable of reading coordinates accurately even at the end of a loop coil.

[0002]

2. Description of the Related Art For example, a white board or a board provided with a flip chart in which a large number of loop coils are laid in parallel in the X and Y directions by an electronic pen which is a marker pen provided with an oscillation coil for generating an alternating magnetic field. When a character, a figure, or the like is drawn thereon, an alternating voltage generated by the oscillation coil of the electronic pen induces an induced voltage in a loop coil magnetically coupled to the magnetic field. Then, each loop coil is scanned, the induced voltage value is read on the board side, and the difference between the voltage value of the loop coil indicating the maximum voltage value and the adjacent loop coil value indicating the next highest voltage is shown in table data. A coordinate reading device such as an electronic blackboard in which the coordinates of the electronic pen are obtained by converting the distance to a reference and the locus of the electronic pen is recorded as digital data has been proposed.

In such an electronic blackboard, characters and figures drawn on a board provided with a whiteboard or a flip chart are electronically recorded as they are, and there is no need to copy or copy the characters and figures on the board each time. It was convenient. In this electronic blackboard, coordinates are calculated by referring to table data set and stored in advance by a difference between induced voltages induced in two adjacent loop coils among loop coils laid in the board. Was to do.

[0004]

However, in the case of a border coil which is an end loop coil having no adjacent loop coil only in one direction, the position of this loop coil on the side where there is no adjacent loop coil. However, there is a problem that the coordinates of the electronic pen cannot be detected depending on the difference between the induced voltages of the adjacent loop coils.

[0005] Further, an edge portion which is an end portion in the longitudinal direction of the loop coil is affected by a short side laid in a direction orthogonal to the longitudinal direction of the loop coil. In this case, it is detected at the edge portion. Voltage changes, and coordinates near the edge cannot be read correctly.

For this reason, there is a problem that the range that can be used as an electronic blackboard is reduced in spite of the existence of the loop coil.

As a method for solving these problems, a method for narrowing the width of an end coil described in Japanese Patent Application Laid-Open No. H8-202491, and a method described in Japanese Patent Application Laid-Open No.
Although there is a method using a sub-loop as described in Japanese Patent Application Publication No. 4 (1994), these methods have a problem that the structure of the end portion becomes complicated or the number of coils increases to complicate the structure. there were.

An object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to provide a coordinate reading device capable of accurately reading the coordinates of the end of a loop coil with a simple loop coil configuration.

[0009]

In order to achieve this object, a coordinate reading apparatus according to a first aspect of the present invention comprises: a transmitting section for generating an alternating magnetic field having a predetermined frequency; A plurality of loop coils elongated in the Y direction that can be coupled are arranged so that adjacent loop coils partially overlap with the adjacent loop coils.
An X coil group configured in parallel with each other in the X direction, which is a direction orthogonal to the Y direction, and a plurality of elongate loop coils in the X direction that can be magnetically coupled with the alternating magnetic field are combined with an adjacent loop coil. A group of Y coils arranged in parallel with each other in the Y direction so that
In the coil group and the Y coil group, a coil voltage detecting means for detecting a voltage induced in each loop coil unit, and a voltage of a loop coil in the X coil group or the Y coil group detected by the coil voltage detecting means A maximum voltage coil detecting means for detecting a maximum voltage loop coil in which a maximum voltage is detected; and a loop coil in which the maximum voltage loop coil is disposed at an end in the X direction of the X coil group, or In the case of a border coil which is a loop coil arranged at an end in the Y direction in the Y coil group, a voltage value induced from the border coil to a reference coil which is a second loop coil in the inward direction is calculated. First comparing means for comparing with a predetermined first reference voltage value, and a voltage value induced in the reference coil by the first comparing means. Adding means for adding a voltage value induced in the border coil and a voltage value induced in the reference coil when it is determined that the voltage is smaller than the first reference voltage value; Border table data that stores a coordinate position corresponding to a value obtained by adding the voltage value and the voltage value of the reference coil, and the coordinate position is referred to by referring to the border table data based on the value added by the adding means. And a border coordinate detecting means for reading the data.

[0010] In the coordinate reading device according to this configuration, the coordinates are not changed even when the transmitting unit exists on the border coils disposed at both ends without changing the configuration of the end of the loop coil. Can be read. In particular, unlike reading the voltage induced in the border coil itself and calculating the coordinates as it is, in addition to the ordinary coordinate detection means, the addition means adds the reference coil, which is the second loop coil in the inward direction of the border coil. Since there is provided border coordinate detecting means for adding the induced voltages and reading the coordinates from the total voltage based on the border table data, the coordinates can be accurately read even with a border coil.

The invention according to claim 2 is characterized in that, when the maximum voltage coil detected by the maximum voltage coil detecting means is an adjacent coil adjacent to the border coil, the maximum coil detected by the maximum voltage coil detection means is connected to the previously stored border coil. A second reference voltage value that is an intermediate value between a voltage value at which the voltage of the adjacent coil matches and a maximum voltage value of the adjacent coil at a position where the border coil does not overlap with the adjacent coil; A second comparing unit that compares the detected voltage with the detected voltage, and when it is determined that the voltage detected from the adjacent coil by the second comparing unit is smaller than the second reference voltage value, The border coordinate detection means, based on the value added by the addition means,
The coordinate position is read with reference to the border table data.

In the coordinate reading device according to this configuration, even if the transmitting unit is present in the border portion, there is a case where the adjacent coil adjacent to the border coil is detected as the maximum voltage coil by the maximum voltage coil detecting unit. However, even in such a case, the coordinates are controlled so that the coordinates can be read correctly. Therefore, even if the transmission unit exists in the border coil, the coordinates can always be read correctly and accurately.

[0013] Also. The invention according to claim 3, wherein the edge table data storing a correction value corresponding to an arbitrary X coordinate or a Y coordinate, and the voltage value of the Y coil or the X coil read by the coil scanning means is stored in the border. Correction means for performing correction by referring to the edge table data based on the coordinate position read by the coordinate detection means, wherein the coordinate position read by the border coordinate detection means is the edge position of the X coil group. The X-coordinate or the Y-coordinate is read based on the voltage value corrected by the correction means when the Y-coordinate is within a predetermined range or within a predetermined distance from the X-coordinate of the edge of the Y coil group. It is characterized by:

In the coordinate reading device according to this configuration, even when the transmitting unit is located near the edge of the loop coil, the coordinates are read after the voltage detected by referring to the edge table data is corrected by the correcting unit. The coordinates can be correctly read even when the transmitting section is near the edge section.

Furthermore, in the invention according to claim 4, the longitudinal ends of the loop coils of the X coil group and the Y coil group are arranged on a flat board surface so as not to overlap with other coil groups. In addition, the end portion is formed so as to be bent rearward with respect to the surface of the board surface on which the X coil group and the Y coil group are laid.

In the coordinate reading device according to this configuration, the end of the loop coil in the longitudinal direction is formed to be bent rearward with respect to the surface of the board surface on which the X coil group and the Y coil group are laid. By canceling the influence of the magnetic field due to the longitudinal end of the loop coil, reducing the ineffective portion around the board surface and increasing the ratio of the writable surface including the portion that can be corrected, the loop coil The ratio of the effective area to the area of the laid board surface can be increased.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A coordinate reading apparatus according to the present invention will be described below with reference to the accompanying drawings, taking an electronic blackboard 1 as a preferred embodiment as an example. FIG. 1 is an external perspective view showing a main configuration of the electronic blackboard 1. As shown in the figure, the electronic blackboard 1 is composed of a pen 60 as a transmitting unit and a writing panel 10 as a receiving unit.

First, the main configuration of the pen 60, which is a transmitting unit, will be described with reference to FIGS. FIG. 3 is an explanatory diagram showing the internal structure of the pen 60, and FIG. 8 is an explanatory diagram showing the electrical configuration of the pen 60 shown in FIG.

As shown in FIG. 3, the pen 60 has a cylindrical body 61a and a lid 61c detachably attached to the rear end of the body 61a. Body part 6
1a, a coil L1, an ink cartridge 63 that can be taken out in a direction indicated by an arrow F2, a pen tip 62 inserted into the ink cartridge 63, and a coil L
A circuit board 69 on which an oscillation circuit or the like for generating an alternating magnetic field is mounted from 1, and a battery 70 as a power supply for supplying electricity to the circuit board 69 are provided. This coil L1 has an inner diameter of about 15 mm and a length of about 15 mm.
The writing surface 21a (FIG. 1)
About 20 mm from the tip of the pen tip 62 in contact with the
It is arranged at a distance.

Between the ink cartridge 63 and the circuit board 69, there is provided a push-button switch 67 for supplying and shutting off electricity to the circuit board 69 and the like. The switch 67 connects the pen tip 62 to the writing surface 21.
a (see FIG. 1), the ink cartridge 63 is turned on when the ink cartridge 63 moves in the direction indicated by the arrow F1, and when writing is stopped, the ink cartridge 63 returns to the direction indicated by the arrow F2 by a spring in the switch 67 and turns off. That is, the writing surface 2 is
An alternating magnetic field is generated from the coil L1 only when writing on 1a.

As shown in FIG. 8, the circuit mounted on the circuit board 69 (see FIG. 3) includes a pen 60 (see FIG. 3) such as the color of ink and the thickness of the pen tip 62 (see FIG. 3). A CR oscillation circuit 69e in which a different modulation frequency fm is set for each attribute (hereinafter referred to as a pen attribute);
An LC oscillation circuit 69c that oscillates a carrier wave that carries a signal oscillated from the oscillating circuit.
(Frequency Shift Keying) and an FSK circuit 69d for performing modulation. The oscillation frequency of the carrier is determined by the coil which is the inductance L1 and the capacitors C2 and C3 which are the capacitances of the LC oscillation circuit 69c.
It is determined by the capacitor C5, the resistor R2, and the variable resistor R3, which constitute the CR oscillation circuit 69e. The frequency shift of the carrier oscillation frequency is F
Capacitor C4, which is the capacitance of SK circuit 69d
Is determined by the capacity of

The relationship between the pen attribute and the modulation frequency fm is set as shown in FIG. 10A for explaining the relationship. In FIG. 10A, “thin” means the pen tip 62
(See FIG. 3) indicates that the pen is thin, and “thick” indicates that the pen tip 62 is thick. For example, “black thick” indicates a pen whose pen tip 62 is thick and uses black ink.

The eraser 40 (see FIG. 1) also has a built-in coil, and recognizes and erases the eraser 40 based on a signal generated in the loop coil 23 (see FIG. 4) by an alternating magnetic field generated from the coil. The modulation frequency fm is also assigned to the eraser 40 to calculate the range.

In FIG. 8, when the switch 67 is turned on, the electricity of the battery 70 is supplied to each circuit, and the output of the integrated circuit IC3 of the CR oscillation circuit 69e is output to the MSK of the FSK circuit 69d.
The gate of the OSFET is switched, and the LC oscillation circuit 6
The carrier wave oscillated from 9c is frequency-modulated by the signal oscillated from the CR oscillation circuit 69e. In the present embodiment, the center frequency of the carrier is 410 kHz, and the frequency shift is ± 15 kHz. In the present embodiment, the integrated circuit IC1 is a TC7SLU04F manufactured by Toshiba, and the integrated circuits IC2 and IC3 are both TC7SLU manufactured by Toshiba.
LU04. The MOS FET is 2SK215
8 The resistors R1 and R2 are both 1 MΩ, and the variable range of the variable resistor R3 is 0Ω to 1MΩ. Capacitors C2, C3, C4 and C5 are 2700 pF and 1 respectively.
000 pF, 270 pF, and 100 pF. further,
Battery 70 is LR44, and its voltage is about 1.5V.

Next, the configuration of the writing panel 10 of the electronic whiteboard 1 which is the receiving unit of the coordinate reading apparatus according to the present embodiment will be described with reference to FIGS. FIG. 2 is an explanatory diagram showing a state in which a personal computer (hereinafter, abbreviated as PC) 100 and a printer 200 are connected to the electronic whiteboard 1 shown in FIG.

The electronic blackboard 1 includes a writing panel 10, a pen 60 for writing on the writing surface 21a, and an eraser 40 for erasing the written locus and data indicating the locus. . The writing panel 10 includes a frame 11 having a frame shape, and the writing panel main body 20 is incorporated in the frame 11. A plate-like base 12 is attached to the lower end of the front surface of the frame 11 along the lower end so as to project to the front surface. On the upper surface of the table 12, a plurality of stand-shaped recesses 12a for accommodating the pen 60 are formed. On the right side of the concave portion 12a, a flat portion 12b for placing the eraser 40 is formed.

On the front right side of the frame 11, an operation unit 30
Is provided. The operation unit 30 has a speaker 31 for reproducing sounds such as an operation sound and a warning sound, and a seven-segment page number in which data indicating the content written on the writing surface 21a (hereinafter abbreviated as writing data) is stored. A page number display LED 32 displayed by an LED, a page return button 33 for returning one page each time the button is pressed, a page forward button 34 for forwarding one page each time the button is pressed, and one page each time the stored writing data is pressed. Delete button 3
5, a printer output button 36 pressed to output the stored writing data to the printer 200 (FIG. 2);
A PC output button 37 pressed to output the stored writing data to the PC 100 (FIG. 2), an input warning LED 39a for warning of an input failure, a battery warning LED 39b for warning of battery exhaustion, and the electronic whiteboard 1 A power button 38 is provided for pressing to activate.

A battery case 14 for accommodating four C-size batteries 14a serving as a power source of the electronic blackboard 1 is provided at a lower portion of the front surface of the frame 11, and a lid 14b is opened and closed on the front surface of the battery case 14. Mounted as possible. On the right side of the battery case 14, a volume control knob 13c of the speaker 31 is provided.
On the right side, connectors 13b and 13a are provided. As shown in FIG. 2, the connector 13b has a plug 202 of a connection cable 204 connected to the printer 200.
Is connected, and the plug 102 of the connection cable 104 connected to the PC 100 is connected to the connector 13a.
That is, writing data indicating the content written on the writing surface 21a of the electronic whiteboard 1 is output to the PC 100, and the content written on the electronic whiteboard 1 can be viewed on the monitor 103 provided in the PC 100. Further, it is also possible to output handwriting data to the printer 200 and print the contents handwritten on the electronic blackboard 1 on the printing paper 203.

As shown in FIG. 1, metal fittings 15 for hanging the electronic blackboard 1 on a wall are attached to both ends of the upper end of the back surface of the frame 11. In the present embodiment, the height H1 of the writing surface 21a is 930 mm, and the width W1 is 610 mm. Also, the frame 11 and the table 1
2 is made of a synthetic resin such as PP (polypropylene) so as to be lightweight, and the total weight of the electronic blackboard 1 is 10 kg or less.

Next, the structure of the writing panel main body 20 will be described with reference to FIG. FIG. 4 shows the writing panel body 20.
It is explanatory drawing which shows each component. Writing panel body 20
Is stored in a frame 11 (see FIG. 1), and has a writing sheet 21 having a writing surface 21a;
2, a frame-shaped mounting panel 24 on which a loop coil 23 is laid, and a plate-shaped back panel 25 are sequentially laminated. In this embodiment, the writing sheet 21 is formed of a PET (polyethylene terephthalate) film having a thickness of 0.1 mm, and the panel 22 is formed of an acrylic resin, ABS (acrylonitrile-butadiene-styrene copolymer). , PC (polycarbonate) or the like to a thickness of 3.0 mm. Also,
The mounting panel 24 is formed of a foamed resin material such as styrene foam to a thickness of 30 mm, and the back panel 25 is formed of a conductive material such as aluminum to a thickness of 1.0 mm.
mm. Further, the entire thickness of the frame 11 that holds each end of the writing panel body 20 is 50 mm.
It is.

Next, the configuration of the loop coil 23 will be described with reference to FIG. FIG. 5A is an explanatory view showing a part of the configuration of the loop coil 23 shown in FIG. 4, and FIG. 5B is a diagram showing the loop coil 23 shown in FIG.
It is explanatory drawing which shows the width | variety and overlap pitch. In the following description, a set of loop coils arranged in the X-axis direction among the loop coils 23 is referred to as an X coil group, and each loop coil is referred to as an X coil. A set of loop coils arranged in the Y-axis direction is called a Y coil group, and each loop coil is called a Y coil. As shown in FIG. 5A, in the X-axis direction, m X coils X1 to Xm for detecting the X coordinate of the (X, Y) coordinates of the pen 60 and the eraser 40 are arranged. In the Y-axis direction, n coils Y1 to Yn for detecting the Y coordinate are arranged orthogonally to the X coil. X coil and Y coil are
Each is formed in a substantially rectangular shape, and the lengths of the long sides of the rectangular portion are P2Y and P2X, respectively.

As shown in FIG. 5B, the length of the short side of the rectangular portion of the X coil is formed to have a width P1, and P1 = 80 mm. The adjacent X coil has a width P
Each of them is overlapped so as to overlap by 40 mm at a pitch of half of one. Each Y coil has width P1 = 80
mm, and adjacent Y coils are overlapped by 40 mm at a pitch of half the width P1. Each terminal 23a of the X coil is connected to the X coil switching circuit 50a (see FIG. 9), and each terminal 23b of the Y coil
Are connected to a Y coil switching circuit 50b (see FIG. 9) (hereinafter collectively referred to as X and Y coil switching circuits 50) (FIG. 9). As an example, in this embodiment, P
1 = 80 mm, P2X is about 652 mm,
P2Y is about 972 mm. Also, m = 14 and n = 22. In addition, the X coil and the Y coil
Both are formed of a 0.345 mm diameter copper wire having an insulating film layer (for example, an enamel layer) on the surface.

Next, the configuration of the end of the loop coil 23 will be described. FIG. 26 is an enlarged view of a part of the loop coil 23. In this description, the border coil Xb of the X coil group refers to the X coil arranged at the end of the X coil group in which there is no adjacent X coil only in one direction, as shown in FIG. Means a portion on the side where there is no adjacent X coil in the border coil Xb and a signal can be detected (a hatched portion ascending right in FIG. 26). The same applies to the Y coil group (the hatched portion in the lower right part of FIG. 26, where the X coil border portions BDx and Yx).
A region where the coil border portion BDy overlaps is indicated by a vertical line. ). In FIG. 26, the border of the X coil group is denoted by B.
Dx, and the border of the Y coil group is denoted by BDy.

The edge portion EG is a portion where a signal can be detected near the short side of the longitudinal end of the loop coil. Here, in FIG. 26, when the edge of the X coil is indicated by EGx, the edge EG of the upper end of the X coil is indicated by EGx.
x is substantially in the same range as the border BDy of the coil Y1 of the Y coil, and similarly, the edge of the Y coil is defined as EG.
y, the edge EGy at the left end of the Y coil is X
The range is substantially common to the border portion BDx of the coil X1 of the coil.

FIG. 27 shows an edge E of the X coil.
It is a perspective view explaining the shape of Gx vicinity. As shown in FIG. 27, the loop coil 23 in the X coil group is composed of a writing surface 21 having a long side arranged in the longitudinal direction and having a flat long side.
a is laid along the Y-axis direction, and if the short side is formed at the end in the Y-direction of the coil by changing its direction on the same plane as the writing surface 21a, the short side laid in the X-axis direction In the part, the distance between the pen 60 and the coil L1 is too close. Therefore, even if the pen 60 has the same X coordinate, the voltage value corresponding to the X coordinate cannot be detected from the loop coil 23 under the influence of the coil short side portion. Therefore, the short side (the end in the longitudinal direction, A in FIG. 27) is bent to the opposite side (the Z direction in FIG. 27) from the writing surface 21a of the panel 22 so as not to approach the coil L1 of the pen 60. Formed. By being formed in this way, the influence of the short side can be reduced.

Note that, as shown in FIG.
The X coil group and the Y coil group constituting the third coil 3 and the X coil and the Y coil constituting the same have a phase difference of 90 °, and the X coil length P2Y is larger than the Y coil length P2X. Is basically the same except that it is formed longer, so that the description of the Y coil will be omitted from the description of the X coil in place of the description of the Y coil. The same applies to the following description.

Here, a position coordinate table for detecting the position coordinates of the pen 60 on the writing surface 21a in a normal portion, that is, a portion other than the border portion BD and the edge portion EG will be described with reference to FIGS. I do. FIG. 6 (A)
FIG. 6B is an explanatory view showing a part of the X coils X1 to X3, and FIG. 6B is a graph showing the relationship between the voltage generated in the X coils X1 to X3 shown in FIG. And
FIG. 6C is a graph showing a voltage difference between mutually adjacent loop coils of the X coils X1 to X3 shown in FIG. 6A. FIG. 7A is an explanatory diagram showing the position coordinate table in a graph, FIG. 7B is an explanatory diagram of the position coordinate table, and FIG. 7C is a diagram of the detected values detected from each X coil. FIG. 4 is an explanatory diagram showing a storage state.

In FIG. 6, the center lines of the X coils X1, X2, and X3 are c1, c2, and c3, respectively.
The graphs of the voltages generated at 1, X2 and X3 are ex, respectively.
1, ex2 and ex3. As shown in FIG.
The voltages ex1 to ex3 are respectively at the center c of the loop coil.
It becomes maximum at 1 to c3 and becomes smaller as the end portion gets closer. Each X coil is overlapped with a width of 1/2 of P so that its own null point, that is, the point where the voltage becomes 0, is located farther from the center of the adjacent X coil. Therefore, when the pen 60 exists at the coordinate position of the center of an arbitrary loop coil 23, an induced voltage is generated from any coil adjacent to the coil. FIG.
6 (A), (B) and FIG. 6 (A), the width is shown to be slightly smaller in order to make it easy to see how the loop coils 23 overlap each other for convenience of explanation.

As shown in FIG. 6C, X coils X1 to X
3 has a maximum value on each of the centers c1 to c3 of the loop coils 23, and an intermediate point between the center of the loop coil 23 and the long side of the loop coil 23; That is, the graph becomes zero at the midpoint of the portion where the adjacent loop coils overlap.

For example, in FIG. 6C, (ex1-e
x2) is the X coil X
1 from the center C1 to the midpoint Q1 of the portion where the X coil X2 is superimposed (1/2 of the superimposed pitch, ie, P
1/4) and (ex1-ex2). Now, if the pen 60 exists at the point Q2, (ex1-
ex2), the distance Δ from the center c1 to the point Q2
Since X1 can be detected, the X coordinate of point Q2 can be obtained. In this embodiment, the coil width P1 is 80 mm
Therefore, P1 / 4 = 20 mm. For example, FIG.
In (C), in a portion showing the characteristics of (ex1-ex2) (portion drawn by a solid line), a distance ΔX [mm] from the center line Cn of the loop coil Xn at an arbitrary position
The relationship between the amplitude DIFF converted into 8-bit digital data obtained from the A / D conversion circuit 52 (see FIG. 9) when the pen 60 is at that position is as shown in the graph of FIG. become. When this graph is converted into a table format, a position coordinate table 58a shown in FIG.
Get. The position coordinate table 58a is stored in the ROM 58
(See FIG. 9) and referred to as table data for determining the position coordinates of the pen 60 from the detected induced voltage.

Next, detection of coordinates in the border portion will be described. FIG. 22 is a graph showing signals detected by the A / D conversion circuit 52 (see FIG. 9) from the X coils X1, X2, and X3. The vertical axis represents the detected signal as b
It is shown in it units. The horizontal axis indicates the distance from this reference line, with the left end of the Y coil Y1 in FIG. 26, that is, the position in the X direction of the short side of the Y coil as the reference line.

First, when the pen 60 is on the X coil X1, the voltage induced for each X coil is detected by X and Y coil scanning (S302 in FIG. 12). Excluding the case, the maximum voltage value ex
For the coil indicating (max), X (max) = X1. Here, if the coil X (max) indicating the maximum voltage value ex (max) is another loop coil 23 other than the border coil Xb, the X coil indicating the second highest voltage value = X (max2) , And the coordinate position can be calculated by referring to the position coordinate table 58a. However, in the border portion BDx having no adjacent X coil, the coordinate position cannot be specified by such a method. On the other hand, in the vicinity of the center line c1 of the loop coil of the present embodiment, as shown in FIG. 22, the characteristic that a relatively gentle top is formed is exhibited, so that only one output change of the X coil X1 is accurate. The X coordinate cannot be detected. So, border part BD
In x, the X coordinate is detected in the following procedure.

In FIG. 26, the border portion BDx is located approximately at the left end of the Y coil Y1 (at a position 26 mm to the left from the left end of the X coil X1; X = 0 in FIG. 26).
Position. ) To the right of 21 mm (hereinafter, X =
From 0, the right side is positive, and the left side is negative, and a distance Nmm from X = 0
Is described as X = N. ) To the position of X = 66. When the pen 60 exists in this range, the X coil X3 which is not adjacent to the second X coil X1 in the inward direction of the border coil Xb together with the X coil X1.
(Here, it is referred to as a reference coil Xs.) Indicates a relatively large voltage. Therefore, the voltage ex of the X coil X1
1 and a voltage ex (1) obtained by summing the voltage ex3 of the X coil X3.
If +3) is used, as shown in FIG. 22, the voltage value greatly changes in accordance with the X coordinate, so that this voltage value ex (1+
From 3), the X coordinate can be specified. Therefore, border table data in which the voltage value ex (1 + 3) and the X coordinate correspond in advance is prepared by an experiment, and the border table data is stored in the ROM 58 as a border table 58b (see FIG. 7D). That is, using the border table 58b, the X coordinate in the border portion BDx is a voltage value ex that is the sum of the voltage value of the X coil X1) that is the border coil Xb and the voltage value of the X coil X3 that is the reference coil Xs. (1 + 3).

However, even if the X coil X1 is the coil X (max) indicating the maximum voltage, the position of the pen 60 is not always in the range of the border portion BDx of the X coil X1.
Whether the pen 60 is in the border portion BDx, the X coil X2
If it is not clear whether the coordinates are on the side adjacent to the above, it cannot be determined whether to calculate the coordinates using the position coordinate table 58a or to calculate the coordinates using the border table 58b. Therefore, it is determined whether the pen 60 is on the border portion BDx or on the side adjacent to the X coil X2 as described below. The output of the X coil X3 when the pen 60 is located at the center line c1 of the X coil X1 is stored in advance as data, and the data is stored in the first reference voltage V
2C. When the X coil X1 is the coil X (max), the voltage ex3, which is the output of the X coil X3 when the pen 60 is outside the center line c1, that is, on the side of the border portion BD, is smaller than the voltage V2C. become. On the other hand, the voltage ex3 when the pen 60 is located inside the center line c1, that is, on the side of the adjacent coil Xr, is higher than the voltage V2C. That is, if the voltage value ex3 of the X coil X3 is known, the voltage value ex3 is compared with the first reference voltage value V2C. It can be determined that it exists.

Note that even when the X coil X2, which is the border coil Xb of the X coil indicating the maximum voltage ex (max), is used instead of the X coil X2, the pen 60 is connected to the X coil X1 that is the border coil Xb. It may be in the vicinity. That is, the border portion BDx of the X coil X1
In the case where the pen 60 is present in the vicinity of the end on the side of the side, the voltage induced near the minimum point of the voltage ex1 at the coil end of the nearest X coil X1 is small, and the induced voltage is small.
In the portion indicated by x1 <ex2, the voltage ex2 induced on the X coil X2, which is far away, is larger. Therefore, even if the X coil X (max) indicating the maximum voltage value ex (max) is X2, the pen 60 is not necessarily required.
Is not necessarily on the coil X2 and may be present on the border portion BDx. To determine this, the following determination is made. First, the voltage value Veq at a place where the output voltage of the adjacent coil Xr Xr X2 adjacent to the X coil X1 adjacent to the border coil Xb becomes equal in advance.
Is calculated. Further, a local maximum voltage value Vom outside the coil of the X coil X2 is calculated. Then, the average value of voltage value Veq and voltage value Vom is stored in advance as second reference voltage value V1C. Next, the adjacent coil X coil X
2 and a second reference voltage value V1C
Compare with If the voltage value ex2 of the adjacent X coil X2
Is smaller than the second reference voltage value V1C, the pen 60
Exist in the border portion BDx.

Therefore, even if the X coil indicating the maximum voltage value ex (max) is X2, the voltage value ex of the X coil X2
If 2 is smaller than the second reference voltage value V1C, BRDROFFSET is obtained using the border table 58b, and the X coordinate is calculated by the following equation.

X = (P1 / 2) × X (max) + BRD
ROFFSET × SIDE + BRDR Here, P1 indicates the width of the coil as described above.
= 80 mm, and x (max) is the number of the coil at which the maximum voltage was detected. Therefore, (P1 / 2) × X
(Max) is the coil number max at which the maximum voltage was detected
BRDROFFSET is a numerical value obtained from the voltage value ex (1 + 3) by the border table 58b. If the SIDE is in the border portion BDx area, that is, if the coil X (max) indicating the maximum voltage is X1, ex3 <V2C or e
If x2 <V1C, SIDE = −1 is set,
Otherwise, SIDE = 1 is set. Further, the BRDR shifts the position of the origin by 26 mm (26 mm to the left in FIG. 26). In the present embodiment, the origin is moved from the left end of the X coil X1 to the left end of the Y coil in the longitudinal direction. Value for For example,
The coil showing the maximum voltage among the X coils is X1,
The maximum voltage value ex (max) <8-bit digital data> at that time is 195, and the direction 2 inside the X1 coil at this time is 2
When the voltage value ex3 <8-bit digital data> of the third X3 coil is 34, ex (1 + 3) is 1
95 + 34 = 229, and BRDROFFSET = 20 is obtained from the border table 58b. P1 = 8
0, X (max) = 1 (“1” of X1), SIDE = −
By substituting 1 (assuming that the pen 60 is in the BDx area (see FIG. 26)) into the above equation, X = (80/2) × 1 + 20 × (−1) + 26 = 46, and the X coordinate “26” Is required.

For example, even when ex (1 + 3) = 230, the closest data among the data existing in the border table 58b is obtained, and ex (1 + 3) is obtained.
+3) Even if 230 = BRDROFFSET = 2
0 is required.

Next, detection of the Y coordinate will be described. FIG. 23 is a graph showing the relationship between the position of the X coordinate in the edge portion EGy and the Y position
The change in the magnitude of the induced voltage of the coil Y1 is represented by the Y coordinate (Y =
26mm, 36mm, 46mm, 56mm from position 0
And the position of 66 mm).
The vertical axis indicates the induced voltage V (X) [V], and the horizontal axis indicates the distance [mm] from X = 0 of the X coil (voltage is also negative on the negative side of X = 0 (left side in FIG. 26). To be induced,
In this embodiment, data from a position where an induced voltage appears is shown. ). For example, approximately Y =
In the graph of 66 [mm], X = 200 [m] from the end.
m] to X = 60 [mm], about 1.5 V
, There is no change, and the voltage decreases as approaching the end from X = 60 [mm]. Also, as shown in FIG. 27, since the upper end of the Y coil is bent to the rear side as described above, when X = 0 [mm], it does not become 0 [V], and X = 0.
It becomes about 0.7 V at [mm] and 0 V at X = -40 [mm]. Similarly, when Y = 56 [mm], X = 60 [m]
m], at about 1.5 V, Y = 46 [mm]
In the case of the above, in the range up to X = 50 [mm], about 1.2
In the case of 5V and Y = 36 [mm], X = 30 [mm]
In the range up to about 0.9 V, when Y = 26 [mm], about 0.25 V in the range up to X = 30 [mm]
Indicate stable voltages, and the voltage decreases as approaching the coil end. From this, at least up to X = 60 [mm], the characteristics are flat, and from the detected voltage value, referring to 58a (see FIG. 7), Y
The coordinates can be determined. On the other hand, if the distance is closer to the end than X = 60 [mm], the voltage drop is not uniform due to the Y coordinate of the pen 60.
Coordinates cannot be detected.

FIG. 24 is a graph showing the voltage value of the induced voltage at each position in each graph shown in FIG. 23 calculated by V (X, Y) / V (X, Y = 66 [mm]). = 66 [mm] is a graph obtained by dividing by the voltage value at the corresponding position in the graph of 66 [mm]. From this graph, a constant numerical value is shown in any of the cases of Y = 56, Y = 46, Y = 36, and Y = 26, that is, in any position of the Y coil Y1, if approximately X> 21. It can be seen that the X coordinate can be detected based on this numerical value. In other words, Y = 56, Y = 46, Y
In any case of = 36 and Y = 26, the peaks differ, but the graph of Y = 66 [mm] gradually decreases at the same rate as the graph gradually decreases toward the end. Therefore, the Y coordinate of the pen 60 is obtained as follows according to the range of the Y coordinate.

For example, when the Y coil overlaps another Y coil (when Y> 66, the hatched portion ascending to the right in FIG. 26), it is obtained by the following equation.

Y = (P1 / 2) × Y (max) + COR
R × SIDE + BRDR Here, P1 indicates the coil width as described above and P1
= 80 mm, and (max) is the number of the coil at which the maximum voltage was detected. Therefore, (P1 / 2) × Y
(Max) is the coil number Y (m) at which the maximum voltage was detected.
ax) indicates the Y coordinate of the center, and CORR is a numerical value obtained by the border table 58a. Also, S
IDE has ey (max-1) equal to ey as described later.
If it is larger than (max + 1), SIDE = −1 is set, and ey (max−1) becomes ey (max + 1)
If not, SIDE = 1 is set. Further, BRDR sets the position of the origin at 26 mm (FIG. 2).
In the present embodiment, this is a value for moving the origin from the upper end of the Y coil Y1 to the upper end in the longitudinal direction of the X coil.

Further, CORR is obtained as follows. First, from the DIFF obtained as described later, D
A correction voltage is obtained by IFF × EDGE. Here ED
GE is a correction value for correcting a voltage that gradually decreases as approaching the end of the Y coil. This EDGE is obtained by the following equation.

EDGE = V (X = 300, Y = 66) /
V (X, Y = 66) Here, V (X = 300, Y = 66) is the coil Y1
Is sufficiently affected by the short side of the coil, X = 30.
0 is the voltage value at the center Y of the coil in the Y direction = 66. V (X, Y = 66) is a voltage value at each X coordinate when Y = 66. Then, the voltage value V (X = 300, Y = 66) is changed to the voltage value V
By dividing by (X, Y = 66), a correction value EDGE for correcting the rate of reduction at each X coordinate is obtained. FIG. 25 shows the correction value thus obtained and the Y coil Y1.
6 is a graph showing a relationship with a distance X [mm] from an end of the graph. In other words, regardless of the position of the Y coordinate, it has been confirmed that the rate at which the voltage gradually decreases as approaching the end of the Y coil is the same and constant as when Y = 66.
The effect of the short side of the Y coil Y1 is eliminated by applying the correction value EDGE to the detected voltage value.

Next, a voltage corrected by DIFF × EDGE is obtained. When a corresponding OFFSET (△ x) is obtained from the position coordinate table 58a based on the corrected voltage value, this value becomes CORR. As mentioned above,
The Y coordinate at the edge portion EGy is obtained.

More specifically, for example, the coil showing the maximum voltage among the Y coils is Y3, and the maximum voltage value ey (max) <8-bit digital data> is 219 at this time. When the voltage value ey2 <8-bit digital data> of the coil Y2 on both sides of Y3 is 1
12. If the voltage value ey4 of the coil Y4 <8-bit digital data> is 77, ey2 = 112 is equal to ey.
Since 4 is larger than 77, SIDE is set to -1. On the other hand, since X = 46 is obtained as described above, the edge table 58C (see FIG. 7E, the contents of the edge table 58C constitute the edge table data of the present invention) corresponds to X = 46. EDGE = 0.9
89 is obtained, and EDGE × DIFF = 0.89 × 1
07 = 106, the position coordinate table 5
8a can be used, and Δx = 10 is obtained from this 106, and this 10 becomes the value of CORR. Note that this COR
The processing for obtaining the value of R functions as the correction means of the present invention. Therefore, when these values are substituted into the equation, Y = (80/2) × 3 + 10 × (−1) + 26 = 136, and the Y coordinate “136” is obtained.

On the other hand, when the Y coil overlaps another Y coil (when Y ≦ 66, the vertical line portion in FIG. 26), it is obtained by the following equation.

Y = (P1 / 2) × Y (max) + BRD
ROFFSET × SIDE + BRDR Here, P1 indicates the width of the coil as described above.
= 80 mm, and Y (max) is the number of the coil at which the maximum voltage was detected. Therefore, (P1 / 2) × Y
(Max) is the coil number Y (m) at which the maximum voltage was detected.
ax) indicates the Y coordinate of the center of BRDROFFSET
Is the voltage value ey (1+
It is a numerical value obtained by 3). Also, SIDE
If it is in the border area BDy, that is, ey3 <V
If 2C or ey2 <V1C, SIDE = −
Set to 1, otherwise set SIDE = 1. Furthermore, BRDR sets the position of the origin to 26
This is a value for shifting the origin from the upper end of the Y coil Y1 to the upper end in the longitudinal direction of the X coil from the upper end of the Y coil Y1 in the present embodiment. For example, the coil showing the maximum voltage among the Y coils is Y1, and the maximum voltage value ey (max) <
8-bit digital data> is 218, and at this time, the voltage value ey3 <8 of the second Y3 coil in the inward direction of the Y1 coil
If the digital data of bits> 30, ey
(1 + 3) is 218 + 30 = 248, and BRDROFFSET = 15 is obtained from the border table 58b. P1 = 80, (max) = 1 (“1” of Y1), SIDE = −1 (the pen 60 is in the BDx area X =
Since it is at 46, it becomes "-1". ) Into the above equation, Y = (80/2) × 1 + 15 × (−1) + 26 = 51, and the Y coordinate “51” is obtained.

For example, even when ey (1 + 3) = 249, the closest data among the data existing in the border table 58b is obtained, and ey (1
+3) = 249 even if BRDROFFSET = 1
5 is required.

Next, the main electrical configuration and control contents of the electronic whiteboard 1 will be described with reference to FIGS. 9, 10B and 11. FIG. FIG. 9 is an explanatory diagram showing the electrical configuration of the electronic whiteboard 1 by blocks, and FIG. 10B is an explanatory diagram showing signals at points A, B, and C in FIG. FIG.
10 is a flowchart showing main control contents executed by the CPU 56 shown in FIG. Hereinafter, main control executed by the CPU 56 will be described with reference to the flowchart of FIG. First, when the CPU 56 provided in the control unit 3 shown in FIG. 9 detects that the power button 38 (see FIG. 1) is pressed and the power is turned on (step (hereinafter abbreviated as S) 10).
0: Yes), the control program stored in the ROM 58 and the position coordinate table 58a (see FIG.
Initial settings such as loading into the work area of AM59 are performed (S200).

FIG. 19 is a flowchart showing the process of initial setting (S200) of the flowchart of FIG.
When the initial setting is started (start), the data of the position coordinate table 58a of the ROM 58 (see FIG.
9 (S201), and then
The data of border table 58b of ROM 58 is RAM
59 (S202), and the data of the edge table 58c of the ROM 58 is stored in the RAM 5 (S202).
9 (S203). Then, initialization such as initialization of other data such as a control program and a flag is also performed (S204), and when the preparation for the processing is completed, the processing of the initialization (S200 in FIG. 11) ends.
Return to the main routine (Return).

When the initial setting (S200) is completed, the process proceeds to the coordinate reading / pen information detecting process (FIG. 11: S300). Here, FIG. 12 is a flowchart showing the flow of the coordinate reading / pen information detection processing (S300) of FIG. Hereinafter, the flow of the coordinate reading / pen information detection processing (S300) in FIG. 11 will be described with reference to FIG. 9 along the flowchart in FIG. When the process starts (start), the X and Y coil scans (S3
02) is performed. The CPU 56 includes X coils X1 to Xm
The coil selection signal A (FIG. 10B) for sequentially selecting the X-coil switching circuit 5 via the input / output circuit (I / O) 53
0a, the X coils X1 to Xm are scanned, and a coil selection signal A (FIG. 10B) for sequentially selecting the Y coils Y1 to Yn is input to the input / output circuit (I
/ O) 53 to the Y-coil switching circuit 50b to scan the Y-coils Y1 to Yn.

Subsequently, if the pen 60 is not detected (S304: No), the CPU 56 ends the coordinate reading / pen information detection processing (FIG. 11: S300) (end) and page processing (FIG. 11: S400). Here, since the pen is detected, it is determined that the pen 60 has been detected (S304: Yes), and the voltage values of the X coil and the Y coil are stored (S306).

Incidentally, the coil scanning of the X coil and the Y coil in S302 functions as the coil voltage detecting means of the present invention.

Here, a signal generated by magnetic coupling between the alternating magnetic field generated from the coil L1 of the pen 60 and one of the X and Y coils is amplified by the amplifier 50c.
An unnecessary band of the amplified signal (see FIG. 10B) is filtered by a band-pass filter (BPF) 50d.
The amplitude detection is performed by the amplitude detection circuit 51. Subsequently, the amplitude-detected signal (FIG. 10B) is converted into a digital signal corresponding to the amplitude, that is, the voltage value by the A / D conversion circuit 52 and input to the CPU 56 via the input / output circuit 53. . X coils X1 to X input to CPU 56
m, the voltage values ex1 to exm indicated by the input digital signal are scanned as shown in FIG.
The values are sequentially stored in the voltage value storage area 59a of the RAM 59 in association with the coil numbers of the X coils,
The voltage values ey1 to eyn indicated by the digital signal input by scanning Yn are shown in FIG.
As in the case of (C), it is sequentially stored in the voltage value storage area 59a of the RAM 59 in association with the coil number of the Y coil. Then, the coil in which the maximum voltage value is detected is extracted from the X coils X1 to Xm, and the X coil number is stored as X (max) (S320). For example, in FIG. 6, the pen 60 exists at the position Q3 and the X coil X
Voltage values ex1, ex2, e
If x3 is generated, the maximum voltage value ex2 is selected, and the coil number 2 of the X2 coil that generated the voltage value ex2 is stored in the RAM 59 as X (max) = 2. In addition, for the Y coil, the coil in which the maximum voltage value is detected among the Y coils Y1 to Yn is extracted, and the Y coil number is stored as Y (max) (S322).
The X (max) and Y (max) stored here are referred to in determining the processing method in the next X, Y coordinate calculation (S308). When the process of S322 ends, the process of X, Y coordinate calculation (S308) is performed.

FIGS. 20 and 21 are flow charts showing the details of the X, Y coordinate calculation (S308) of FIG. Hereinafter, FIG. 1 along FIG. 20 and FIG.
The procedure of X, Y coordinate calculation (S308) of Step 2 will be described. When the processing of the X and Y coordinate calculation (S308) in FIG. 12 is started (FIG. 20: Start), first, the voltage of the X coil and the Y coil stored in the RAM 59 is used to determine the maximum voltage among the X coils. It is determined whether X (max), which is an X coil indicating a value, is X1 (S71), and if X (max) is X1
If so (S71: Yes), it is determined whether ex3 <V2C because the pen 60 may be on the border coil Xb (S75). If ex3 <V2
In the case of C, since X (max) is the border coil X1, the processing shifts to S79, and the X coordinate is calculated as described above with reference to the border table 58b. And FIG.
As shown in FIG. 6, if the pen 60 is located at the border portion BDx of X, the pen 60 is located at the edge portion EGy of Y at the same time.
The processing shifts to S80, where the Y coordinate is stored in the edge table 58.
The calculation is performed as described above with reference to the data of c.

Even if X (max) is not X1 (S71:
No), if X (max) is X2 (S72: Ye
s), if ex2 <V1C, pen 60 is placed in border B
Dx may be present, so it is determined whether ex2 <V1C (S76), and if ex2 <V1C (S76).
76: Yes), and are processed by S79 and S80. If X (max) is neither X1 nor X2, (S
72: No), the border coil at the opposite end is X (ma)
x), to determine whether or not X (max) is X
(M-1) is determined (S73), and X (ma
If x) is X (m-1) (S73: Yes), ex
It is determined whether (m-1) <V1C (S77), and e
If x (m-1) <V1C (S77: Yes), S
79 and S80. And X (max)
Is not any of X1, X2, X (m-1) (S
73: No), it is determined whether or not X (max) is X (m) (S74), and if X (max) is X (m) (S74).
74: Yes), it is determined whether ex (m-2) <V2C (S78), and if ex (m-2) <V2C (S78: Yes), processing is performed in S79 and S80.

If S74, S75, S76, S77,
If each condition is not satisfied in S78, (S74: N
o, S75: No, S76: No, S77: No, S7
8: No), the pen 60 has a border portion BDx of the X coil.
, Respectively, through the connector circled A, FIG.
The processing shifts to the flowchart of FIG.

When the processing shifts to the processing of the flowchart of FIG. 21 via the connector circled A, it is next determined whether or not Y (max) which is the Y coil showing the maximum voltage value among the Y coils is Y1 ( (S81) If Y (max) is Y1 (S81: Yes), it is determined whether or not ey3 <V2C because the pen 60 may be on the border coil Yb (S87). If ey3 <V2C
Then, since Y (max) is the border coil Y1,
The processing shifts to S91, where the Y coordinate is stored in the border table 58.
It is calculated as described above with reference to b. Then, as shown in FIG. 26, if the pen 60 is in the border portion BDy of Y,
At the same time, since it is at the edge portion EGx of X, the X coordinate is calculated as described above with reference to the data of the edge table 58c.

Even if Y (max) is not Y1 (S81:
No), Y (max) is Y2 (S82: Ye
s) If ey2 <V1C, pen 60 is placed in border B
Since Dy may exist, it is determined whether or not ey2 <V1C (S88). If ey2 <V1C, it is determined (S88).
88: Yes), and are processed in S91 and S92. If Y (max) is neither Y1 nor Y2 (S
82: No), the border coil at the opposite end is Y (ma)
x), to determine whether it is x), Y (max) is Y
(N-1) is determined (S83), and Y (ma
If x) is Y (n-1) (S83: Yes), ey
It is determined whether (n-1) <V1C (S89), and e
If y (n-1) <V1C (S89: Yes), S
The processing is performed by steps 91 and S92. And Y (max)
Is not any of Y1, Y2, Y (n-1) (S
83: No), it is determined whether or not Y (max) is Y (n) (S84). If Y (max) is Y (n) (S84)
84: Yes), it is determined whether or not ey (n−2) <V2C (S90). If ey (n−2) <V2C (S90: Yes), processing is performed in S91 and S92.

If S84, S87, S88, S89,
If each condition is not satisfied in S90, (S84: N
o, S87: No, S88: No, S89: No, S9
0: No), the pen 60 is a border portion BDx of the X coil.
S85, S85, respectively, either directly or via a connector circle B
The process proceeds to 86. In S85, the above-described pen 60 is
Normal position coordinate table 58a in the case where neither the border part BDx of the X coil nor the border part BDy of the Y coil exists
The following processing using is performed. In S86, the Y coordinate is obtained in the same procedure.

The processing of S75, the processing of S79, the processing of S87 and the processing of S90 function as the first comparing means of the present invention, and the processing of S76, the processing of S77, the processing of S88 and the processing of S89 Functions as the second comparing means of the present invention.

FIG. 28 shows a procedure for calculating the X coordinate shown in FIG. 21 with reference to the position coordinate table data (FIG. 2).
1: S85) is a flowchart showing the details of the X coordinate calculation procedure. Hereinafter, the procedure of calculating the X coordinate of FIG. 21 with reference to the position coordinate table data (FIG. 21: S85) will be described in detail along this flowchart. First, when the processing is started (start), the CPU 56
The voltage value ex (max-1) of the coil number = X (max-1) having a number smaller than the coil number = X (max) indicating the maximum voltage value is extracted and stored in the RAM 59 (S804). Further, a coil number indicating a maximum voltage value = a coil number having a number one greater than X (max) =
The voltage value ex (max + 1) of X (max + 1) is extracted and stored in the RAM 59 (S806).

The voltage ex (max-1) and the voltage ex (ma
x (x + 1) (S812), and ex (ma
x-1)> ex (max + 1), that is, ex (max-1) stored in the RAM 59 is ex (max +
If the voltage value is larger than 1) (S812: Yes),
Coil X (max-1) is defined as coil max2, and SID
E is set as SIDE = −1 (S818). The voltage value ex (ma) of the coil X (max) indicating the maximum voltage value
x), the coil X (ma) indicating the second largest voltage value
The difference is obtained by subtracting the voltage value ex (max-1) of x-1) to obtain DIFF (S820).

The voltage ex (max-1) and the voltage ex
By comparing the magnitude with (max + 1) (S812), ex
If (max−1)> ex (max + 1) is not satisfied, that is, if the voltage value of ex (max + 1) stored in the RAM 59 is larger than ex (max−1), (S
812: No), coil X (max + 1) is replaced with coil ma
x2, and SIDE is set as SIDE = 1 (S
814). Then, the coil X (ma) indicating the maximum voltage value
x), the voltage value e of the coil X (max + 1) showing the second largest voltage value in this case from the voltage value ex (max)
The difference is obtained by subtracting x (max + 1) to obtain DIFF (S816).

For example, in the example of Q3 shown in FIG.
Since (max + 1)> ex (max−1), (81
2: No), ex2 which is the maximum voltage value ex (max)
Ex3 which is a voltage value ex (max + 1) on both sides of
Among ex1 which is x (max-1), ex3 which is ex (max + 1) having a large voltage value is determined as max2, stored in the RAM 59, and the variable SIDE is set to 1 (S814). Subsequently, the CPU 56 sets DIFF = ex2
-Ex3 is calculated, and the position coordinates closest to the calculated DIFF are read out from the position coordinate table 58a stored in the ROM 58 and set as OFFSET (S
822). Subsequently, assuming that the coil number is max, X = (P1 / 2) × X (max) + OFFSE
T × SIDE + BRDR is calculated to obtain an X coordinate X1 (S824). Here, P1 indicates the width of the coil as described above, where P1 = 80 mm, and X (max) is the number of the coil at which the maximum voltage was detected. Therefore,
(P1 / 2) × X (max) indicates the X coordinate of the center of the coil number X (max) at which the maximum voltage was detected, and BR
DR shifts the X coordinate by 26 mm (26 mm to the left in FIG. 26). In the present embodiment, the origin is X
This is a value for moving from the left end of the coil X1 to the left end in the longitudinal direction of the Y coil. For example, Q3 shown in FIG.
Are (ex2-ex3) = 176,
Since △ X corresponding to (ex2-ex3) = 176 is obtained from the position coordinate table 58a as △ X = 4, it is OFF.
SET = 4. Therefore, X = (80/2) × 2 + 4
× 1 + 26 = 110, and the X coordinate of the position Q3 is X =
114. As described above, when the process of calculating the X coordinate of FIG. 21 with reference to the position coordinate table data (S85) is completed (end), the Y coordinate is calculated in the same procedure,
The X and Y coordinate calculation processing (S308) in FIG. 12 ends.

When the X and Y coordinate calculation processing (S308) in FIG. 12 is completed in the above procedure, the FSK in FIG.
The process of reading the value of the demodulation circuit (S310) and the process of determining the pen attribute (S312) are performed. Below, CPU5
6 reads the value of the FSK demodulation circuit of FIG. 12 which performs the electrical configuration and control for determining the pen attribute (S31).
0) and the process of determining the pen attribute (S312) will be described with reference to FIGS. FIG.
FIG. 14 is an explanatory diagram showing an electrical configuration of the demodulation circuit 55 (FIG. 9), and FIG. 14 is an explanatory diagram showing signal waveforms appearing at various parts of the FSK demodulation circuit 55 shown in FIG.

FIG. 15A shows an output signal (hereinafter, referred to as a CR signal) of the CR oscillation circuit 69e (see FIG. 8).
The output signal of the LC oscillation circuit 69c (refer to FIG. 8) (hereinafter referred to as a carrier signal) and the output signal of the limiter circuit 54 (refer to FIG. 9) (hereinafter referred to as a limiter output signal).
FIG. 14 is an explanatory diagram showing a relationship between the count value and a count value K by a count circuit 55a (see FIG. 13). FIG. 15B is an explanatory diagram showing how the count value K stored in the shift register 55b (see FIG. 13) shifts.

FIG. 16A shows an absolute value comparator 55.
f (see FIG. 13) and the CPU 5
FIG. 16 is an explanatory diagram showing the relationship with the determination cycle of FIG.
(B) is an explanatory diagram showing how the count value K by the counter 55g moves. FIG. 17 is a flowchart showing the flow of processing (pen attribute detection processing 1) from the count circuit 55a constituting the FSK demodulation circuit 55 to the absolute value comparator 55f in S312.
FIG. 18A is a flowchart showing the flow of processing of the counter 55g in S312, and FIG.
12 is a flowchart showing the flow of the processing of an adder 55i in FIG. The carrier signal shown in FIG. 15A has, for example, a center frequency of 410 kHz and a frequency shift of ± 15 kHz as described above. However, in FIG. Exaggerate the shift.

First, FSK for detecting pen attributes
The features of the demodulation circuit 55 will be described with reference to FIG. In the example shown in FIG. 15A, the carrier signal has a high frequency (for example, 425 kHz) during the low level of the CR signal.
z), and is modulated to a low frequency (for example, 395 kHz) during the high level. For this reason,
Assuming that the period of the limiter output signal during the low level of the CR signal is TB, the period of the limiter output signal during the high level of the CR signal is TC longer than TB. Therefore, the count value K for one cycle of the limiter output signal by the count circuit 55a increases when the CR signal changes from a low level to a high level, and decreases when the CR signal changes from a high level to a low level.

That is, by detecting the timing at which the count value K by the count circuit 55a changes, C
The rising or falling timing of the R signal can be detected. Since the time from the change of the count value K to the next change corresponds to a half cycle of the CR signal, if one cycle of the change time of the count value K is measured, Since the period can be obtained, the pen attribute can be detected. Where FSK
An outline of the operation of each component of the demodulation circuit 55 will be described.
The count circuit 55a measures the count value K, and outputs a shift register 55b, a first weighted average circuit 55c, a second weighted average circuit 55d, a subtractor 55e, and an absolute value comparator 5
5f detects the change timing of the count value K, and the counter 55g, the register 55h, and the adder 55i measure the cycle in which the count value K changes. And the CPU 56
Determines the pen attribute based on the added value output from the adder 55i (FIG. 12: S312).

Next, the operation of the FSK demodulation circuit 55 will be described in detail. The signal output from the band-pass filter 50 d is converted by the limiter circuit 54 into a square wave limiter output signal shown in FIG. 14 and output to the FSK demodulation circuit 55. Then, upon detecting the rise of the limiter output signal, the FSK demodulation circuit 55 (S10 in FIG. 17: Y
es), counting of the cycle of the limiter output signal is started using the system clock (CLK) (S1 in FIG. 17).
2) When the next rise of the limiter output signal is detected (S14 in FIG. 17: Yes), the count value K is output to the shift register 55b (S16 in FIG. 17), and the count value K is reset (S18 in FIG. 17). ). That is, the count circuit 55a measures the length TB or TC of one cycle of the limiter output signal.

In this embodiment, the shift register 55
15B, as shown in FIG. 15B, the count value K for one cycle of the limiter output signal is stored for eight cycles of K1 to K8, and every time the newest count value K is taken in, the oldest count value K is stored. Discard and shift each count value K one by one. The first weighted average circuit 55c calculates a weighted average value from the latest count value K stored in the shift register 55b to the third newest count value K, and calculates the weighted average value (hereinafter, referred to as the first weighted average value). ) Is output to the subtractor 55e. The second weighted average circuit 55d calculates a weighted average value from the oldest count value K stored in the shift register 55b to the third oldest count value K, and calculates the weighted average value (hereinafter, referred to as a second average value).
It is called the weighted average. ) Is output to the subtractor 55e.

The subtractor 55e calculates a difference Δm between the first weighted average and the second weighted average, and outputs the difference Δm to the absolute value comparator 55f (S20 in FIG. 17). For example, in FIG. 15A, when the first weighted average circuit 55c calculates the weighted average of the count values K1 to K3, and the second weighted average circuit 55d calculates the weighted average value of the count values K6 to K8, Among the values K6 to K8, since the count values K7 and K8 are obtained by counting the period TC longer than the period TB of the limiter output signal, the second weighted average value is larger than the first weighted average value. Therefore, by detecting that the second weighted average value has become larger than the first weighted average value, it is possible to detect a change point of the period of the CR signal. That is, if the period of the change point of the period of the CR signal is detected, the period of the CR signal can be detected, so that the attribute information of the pen 60 can be recognized.

As described above, since the count values K counted in time intervals are weighted and averaged by the weighted averaging circuit, even if a certain count value K is affected by noise, the influence is reduced.

Next, the processing from the absolute value comparator 55f to the adder 55i will be described with reference to FIG. In FIG. 16, 〜 indicates the count value K by the counter 55g. The absolute value comparator 55f calculates the difference Δ
m is compared with a preset threshold value m1, and it is determined whether or not the difference Δm is equal to or greater than the threshold value m1 (FIG. 17).
If it is determined that the difference Δm is equal to or greater than the threshold value m1 (S22: Yes in FIG. 17), the threshold determination output is changed from low level to high level (S2 in FIG. 17).
4). That is, the period of the limiter output signal has changed (C
(A rising edge of the R signal is detected). For example, the count value K by the count circuit 55a of the shorter cycle TB of the limiter output signal shown in FIG.
0, the count value K of the period TC is 16, and the threshold value m1 is 2
Then, since the count values K1 to K6 are all 10, the first weighted average value = (K1 + K2 + K3) / 3 = 1
It becomes 0. In addition, since the count values K7 and K8 are both 16, the second weighted average value = (K6 + K7 + K8) / 3
= 42/3 = 14, and the difference Δm = 10−14 = −4.

The first weighted averaging circuit 55c and the second weighted averaging circuit 55d are determined based on the ratio between the carrier frequency (the oscillation frequency of the LC oscillation circuit 69c) and the modulation frequency fm, and the complexity of the circuit. Further, the count value K held by the shift register 55b, that is, the number of periods of the limiter output signal is determined by the ratio of the system clock frequency to the frequency of the carrier, and the frequency of the system clock is large enough to discriminate the change in the frequency. Set to

Accordingly, since (absolute value of difference Δm = 4)> (threshold value m1 = 2), the threshold value judgment output changes from low level to high level (S24 in FIG. 17). This high level state indicates that the absolute value of the difference Δm is equal to the threshold value m1
The above is maintained until the absolute value comparator 55f determines. When the calculation range of the first weighted averaging circuit 55c and the second weighted averaging circuit 55d reaches a portion passing through the edge of the CR signal, the period of the limiter output signal becomes constant. Calculate the weighted average value of the count value K in the same cycle, the subtraction value by the subtractor 55e becomes 0, and the threshold value determination output remains in the high level state.

On the other hand, when the counter 55g detects that the threshold value judgment output has changed from the low level to the high level (S30 in FIG. 18A: Yes), the time when the judgment output is at the high level, that is, The half cycle of the judgment output is counted using the system clock (CLK) (S3).
2). Let the count value be K ((B1) in FIG. 16B). When the absolute value comparator 55f determines that the difference Δm is equal to or larger than the threshold value m1 (S22: Yes in FIG. 17), the threshold determination output is changed from a high level to a low level (S24). That is, it is determined that the cycle of the limiter output signal has changed (the falling edge of the CR signal has been detected). Thus, the counter 55g detects that the threshold value determination output has changed from the high level to the low level (FIG. 18A: S34:
Yes), and outputs the count value to the register 55h as shown in (B2) of FIG. 16B (S36). Subsequently, the counter 55g resets the count value (S3
8) Count the time when the threshold value judgment output is at the low level, that is, the half cycle of the threshold value judgment output (circled B, S32). The count value is used.

Subsequently, the adder 55i determines that the timing at which the count value K is held in both the counter 55g and the register 55h, that is, the addition timing (S
50: Yes), the count value held by the counter 55g and the count value held by the register 55h are added (S52), and the added value is output to the CPU 56 (S56). At this time, the counter 55g is
The count value is output to the register 55h as shown in (B3) of (B) (S36 of FIG. 18A). And
The CPU 56 reads the value of the FKS demodulation circuit 55 via the input / output circuit 53, that is, the addition value (S in FIG. 12).
310, FIG. 13), and determines the pen attribute based on the read addition value (S312). For example, when the added value is 245, it is determined that the pen attribute is black and thick as shown in FIG. Also, the CPU 56
The pen attributes and the XY coordinates are stored in the RAM 59 in association with each other. The writing data stored in this manner is output to, for example, the printer 200 (see FIG. 2) and printed in black. The data is output to the PC 100 (see FIG. 2) and displayed on the monitor 103 (see FIG. 2) in black. That is, the writing data can be reproduced according to the attribute of the pen 60.

Subsequently, the adder 55i adds the count value of the register 55h and the count value of the counter 55g and outputs the result to the CPU 56 ((B) in FIG. 16B).
3)). Thereafter, each time the threshold determination output changes, the count value K of the counter 55g is output to the register 55h, and the adder 55i adds the count value K of the counter 55g and the count value K held in the register 55h. Then, the cycle of outputting the added value to the CPU 56 is repeated. That is, as shown in FIG. 16B, the adder 55i includes the latest count value K counted by the counter 55g and 1 held in the register 55h.
In order to add the previous count value K and output it to the CPU 56, as shown in FIG.
Determines the pen attribute based on the sum of the latest count value K and the previous count value K every half cycle of the threshold value determination output. Therefore, even if the scan of the loop coil 23 is performed in the middle of the threshold determination output, for example, between times t0 and t1 in FIG. Even if the added value of (t2 to t4) is not taken in, one of the times t2 to t4 half a cycle after the time t1 is obtained.
Since it is sufficient to take in the added value of the period, the pen attribute can be determined at high speed.

As described above, the X and Y coil scans (FIG. 1)
2 and S302) are repeated to start writing with the pen 60 shown in FIG. 1 on the writing surface 21a. After the pen 60 is detected for the first time (S304: Yes), the pen 60 is separated from the writing surface 21a and the pen 60 (S
304: No), the processing of S302 to S314 is repeated, and the pen attributes of the series of pens 60 and the XY coordinates are associated with each other and stored in the locus storage area (not shown) of the RAM 59.
Axis, in a dot matrix aligned in the Y-axis direction,
The X coordinate and the Y coordinate are stored together with the pen attributes.
Thus, the procedure of the coordinate reading / pen information detecting process (S300) shown in FIG. 11 ends.

Here, returning to the flowchart of FIG. 11, the description will be continued. Coordinate reading / pen information detection processing (S300)
Is completed, when the page return button 33, the page forward button 34, and the delete button 35 are pressed, the CPU 56 performs page processing such as returning, sending, or deleting stored writing data in page units. (S40
Perform 0). In the page processing, the CPU 56 operates the operation unit 3
A switching signal generated by operating various buttons (see FIG. 1) provided on an I / F circuit 57 (see FIG. 9)
Page processing, such as returning or sending the page storing the position coordinate data stored in the RAM 59 in page units, or erasing the position coordinate data in page units. Further, the CPU 56
Of the position data stored in M59, the position coordinate data of the target page is converted into an appropriate format and
A data output process (S500) for outputting to the C100 and the printer 200 (see FIG. 2) is executed.

Further, the CPU 56 (see FIG. 9) operates the audio circuit 31a (see FIG. 9) based on a switching signal generated when various buttons are pressed, and the speaker (SP) 31 (see FIG. 9). Then, a voice output process for generating operation sounds such as “P” and “B” is executed (S600).
When one round of processing is completed, the processing from S100 to S600 is repeated (return, S100 to S600).

The electronic blackboard 1 according to the embodiment of the present invention comprises:
With the above-described configuration and effects, the following effects can be obtained. That is, even if the pen 60 exists on the border coils Xb and Yb disposed at both ends without changing the configuration of the end of the loop coil 23, the coordinates can be read. is there. In particular, it cannot take the difference between adjacent coils,
Border coil X coil X1, Xm or Y coil Y1, Y
In contrast to reading the voltage induced on itself and calculating the coordinates, the normal position coordinate table 58
coordinate detecting means for obtaining coordinates with reference to a (FIG. 21: S8
5, S86), the adding means adds the voltage induced in the reference coil, which is the second loop coil in the inward direction of the border coil (the adding means of the present invention). Border coordinate detecting means for reading the coordinates (FIG. 20: S79, FIG. 21: S
91), there is an effect that the coordinates can be accurately read even with the border coils Xb and Yb.

Further, the pen 60 is moved to the border portion BDx, B
Even if it exists in Dy, the maximum voltage coil detecting means (FIG. 12: S306) exceptionally makes the border coils Xb, Y
b is the maximum voltage coil Xr.
In some cases, the coordinates are detected as (max) and Y (max), but even in such a case, there is an effect that the coordinates are controlled so that the coordinates can be read correctly. Therefore, even if the pen 60 is present on the border coils Xb and Yb, the coordinates can always be read correctly and accurately.

When the pen 60 exists at the edge portions EGx and EGy, which are the ends in the longitudinal direction of the loop coil 23, the correcting means (FIG. 20: S80, FIG. 21: S92).
Therefore, the coordinates are read after correcting the voltage detected with reference to the data of the edge table 58c, so that the coordinates can be read correctly even when the pen 60 is located at the edge portions EGx and EGy.

As described above, the present invention has been described based on one embodiment. However, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. Can be easily inferred.

[0099]

According to the coordinate reading device of the first aspect of the present invention, the transmitting unit is provided on the border coils disposed at both ends without changing the configuration of the end of the loop coil. Even when it exists, there is an effect that its coordinates can be read. In particular, unlike reading the voltage induced in the border coil itself and calculating the coordinates as it is, in addition to the ordinary coordinate detection means, the addition means adds the reference coil, which is the second loop coil in the inward direction of the border coil. Since there is provided border coordinate detecting means for adding the induced voltages and reading the coordinates from the total voltage based on the border table data, there is an effect that the coordinates can be accurately read even with a border coil.

According to the coordinate reading device of the second aspect of the present invention, in addition to the effect of the coordinate reading device of the first aspect of the present invention, even if the transmitting section is present in the border section, the maximum voltage exceptionally occurs. In some cases, the coil detecting means detects an adjacent coil adjacent to the border coil as the maximum voltage coil. Even in such a case, there is an effect that control is performed so that coordinates can be read correctly. Therefore, there is an effect that the coordinates can always be read correctly and accurately even if the transmission unit exists in the border coil.

According to the coordinate reading device of the third aspect of the present invention, in addition to the effects of the coordinate reading device of the first or second aspect of the present invention, when the transmitting unit is located near the edge, the correction is performed. Since the coordinates are read after the voltage detected by referring to the edge table data is corrected by the means, there is an effect that the coordinates can be read correctly even when the transmitting section is near the edge section.

According to the coordinate reading device of the fourth aspect of the present invention, in addition to the effect of the coordinate reading device of the first aspect, the longitudinal end of the loop coil is formed on the board surface. By being bent to the back side with respect to the surface on which the X coil group and the Y coil group are laid, there is an effect that the influence of the magnetic field due to the longitudinal end can be canceled,
By reducing the invalid portion around the board surface and increasing the percentage of the writable surface including the portion that can be corrected,
There is an effect that the ratio of the effective area to the area of the board surface on which the loop coil is laid can be increased.

[Brief description of the drawings]

FIG. 1 is an external perspective view illustrating a main configuration of an electronic blackboard 1;

FIG. 2 is an explanatory diagram showing a state in which a personal computer 100 and a printer 200 are connected to the electronic whiteboard 1 shown in FIG.

FIG. 3 is an explanatory diagram showing an internal structure of a pen 60.

FIG. 4 is an explanatory diagram showing each component of the writing panel 20.

FIG. 5A is an explanatory view showing a configuration of the loop coil 23 shown in FIG. 4 with a part thereof omitted; (B) It is explanatory drawing which shows the width | variety and overlap pitch of the loop coil 23 shown in FIG. 5 (A).

FIG. 6A is an explanatory view showing a part of X coils X1 to X3. FIG. 7B is a graph showing the relationship between the voltage generated in the X coils X1 to X3 shown in FIG. 6A and the distance in the width direction. 7C is a graph showing a voltage difference between mutually adjacent loop coils of the X coils X1 to X3 shown in FIG.

FIG. 7A is an explanatory diagram showing a position coordinate table as a graph. (B) It is explanatory drawing of a position coordinate table. (C) It is explanatory drawing which shows the storage state of the detection value detected from each X coil.

FIG. 8 is an explanatory diagram showing an electrical configuration of the pen 60 shown in FIG.

FIG. 9 is an explanatory diagram showing the electrical configuration of the electronic blackboard 1 by blocks.

FIG. 10A is a diagram illustrating a relationship between an attribute of a pen 60 and a modulation frequency fm. (B) It is explanatory drawing which shows the signal in point A, B, and C in FIG.

11 is a flowchart showing main control contents executed by a CPU 56 shown in FIG.

FIG. 12 is a flowchart illustrating a flow of a coordinate reading process.

13 is an explanatory diagram illustrating an electrical configuration of an FSK demodulation circuit 55. FIG.

14 is an explanatory diagram showing signal waveforms appearing at various parts of the FSK demodulation circuit 55 shown in FIG.

FIG. 15A shows an output signal of a CR oscillation circuit 69e;
FIG. 9 is an explanatory diagram showing a relationship among an output signal of an LC oscillation circuit 69c, an output signal of a limiter circuit 54, and a count value K by a count circuit 55a. (B) is an explanatory diagram showing how the count value K stored in the shift register 55b shifts.

16A is an explanatory diagram showing a relationship between a threshold determination output by an absolute value comparator 55f and a determination cycle of a CPU 56. FIG. (B) It is explanatory drawing which shows a mode that the count value K by the counter 55g moves.

FIG. 17 is a flowchart showing the flow of processing (pen attribute detection processing 1) from the count circuit 55a to the absolute value comparator 55f that constitutes the FSK demodulation circuit 55.

FIG. 18A is a flowchart showing the flow of processing of a counter 55g in S312. (B) It is a flowchart which shows the flow of a process of the adder 55i in S312.

FIG. 19 is an initial setting of the flowchart of FIG. 11 (S20);
It is a flowchart which shows the process of 0).

20 is a flowchart showing the details of the X and Y coordinate calculation (S308) of FIG. 12 together with FIG. 21;

21 is a flowchart showing details of the processing of the X and Y coordinate calculation (S308) of FIG. 12 together with FIG. 20;

FIG. 22 is a graph showing signals detected by the A / D conversion circuit 52 (see FIG. 9) from the X coils X1, X2, and X3.

FIG. 23 is a graph showing a change in the magnitude of the induced voltage depending on the position of the Y coordinate at the edge EG for each distance from the end of the X coil X1.

FIG. 24 shows the values of the induced voltage at each position of each graph shown in FIG. 23 as V (X, Y), V (X = 40 [m
m], Y), and shows a graph obtained by dividing by a voltage value at a corresponding position in the graph of X = 40 [mm].

FIG. 25 is a graph showing the relationship between the obtained correction value and the distance Y [mm] from the end of the X coil X1.

FIG. 26 is an enlarged view of a part of the loop coil 23.

FIG. 27 is a perspective view illustrating a shape near the edge portion EGx of the X coil.

FIG. 28 is a flowchart showing in detail a procedure of an X coordinate calculation in a procedure of calculating the X coordinate shown in FIG. 21 with reference to the position coordinate table data (FIG. 21: S85).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electronic blackboard 10 Writing panel 20 Writing panel main body 21a Writing surface 23 Loop coil 60 Pen (writing means) X1, X2, X3 X coil Y1, Y2, Y3 Y coil BDx, BDy Border part EGx, EGy Edge part

Claims (4)

[Claims] 1. A transmitting section for generating an alternating magnetic field of a predetermined frequency, and a plurality of Y-direction elongated loop coils magnetically coupleable with the alternating magnetic field generated from the transmitting section are disposed adjacent to each other. An X coil group configured in parallel with each other in the X direction, which is a direction orthogonal to the Y direction, so that the portions overlap, and an elongated in the X direction that can be magnetically coupled with the alternating magnetic field generated from the transmission unit. A plurality of loop coils arranged in parallel with each other in the Y direction such that a part thereof overlaps with an adjacent loop coil; and a loop coil in each of the X coil group and the Y coil group. A coil voltage detecting means for detecting a voltage induced per unit; and a voltage of a loop coil in the X coil group or the Y coil group detected by the coil voltage detecting means. Chi, the maximum voltage coil detection means for detecting a maximum voltage loop coil at which the maximum voltage is detected, the maximum voltage loop coil, among the X coil group X
A loop coil placed at the end in the direction
When the coil group is a border coil which is a loop coil arranged at the end in the Y direction, a voltage value induced from the border coil to a reference coil which is a second inward loop coil is determined by a predetermined value. First comparing means for comparing with the first reference voltage value, and the first comparing means determines that the voltage value induced in the reference coil is smaller than the first reference voltage value. In this case, adding means for adding a voltage value induced in the border coil and a voltage value induced in the reference coil, and a value obtained by adding the voltage value of the border coil and the voltage value of the reference coil. Based on the border table data storing the corresponding coordinate positions and the value added by the adding means, the position coordinates where the transmitting unit is present are read by referring to the border table data. Coordinate reading apparatus being characterized in that a border coordinate detection means that. 2. When the maximum voltage coil detected by the maximum voltage coil detection means is an adjacent coil adjacent to the border coil, the voltage of the border coil and the voltage of the adjacent coil stored in advance match. And a second reference voltage value which is an intermediate value between the voltage value of the adjacent coil and a maximum voltage value of the adjacent coil at a position where the border coil does not overlap the adjacent coil, and a voltage detected from the adjacent coil. A second comparing means, and when it is determined that the voltage detected from the adjacent coil by the second comparing means is smaller than the second reference voltage value, the border coordinate detecting means sets 2. The coordinate reading apparatus according to claim 1, wherein the coordinate position is read by referring to the border table data based on the value added by the adding means. . 3. An edge table data storing a correction value corresponding to an arbitrary X coordinate or a Y coordinate, and a voltage value of the Y coil or the X coil read by the coil scanning means, and the border coordinate detecting means. Correction means for correcting by referring to the edge table data on the basis of the coordinate position read by the method, wherein the coordinate position read by the border coordinate detection means is calculated from the Y coordinate of the edge portion of the X coil group. The X-coordinate or the Y-coordinate is read based on the voltage value corrected by the correction means when the distance is within a predetermined range or within a predetermined distance range from the X coordinate of the edge of the Y coil group. The coordinate reading device according to claim 1 or 2, wherein 4. The X-coil group and the Y-coil group are arranged on a flat board surface such that longitudinal ends of respective loop coils do not overlap with other coil groups, and the end portions are connected to the board. The coordinate reading device according to any one of claims 1 to 3, wherein the coordinate reading device is formed to bend rearward with respect to a surface on which the X coil group and the Y coil group are laid.