JP2001142628A - Coordinate reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coordinate reader capable of accurately reading the coordinates of a transmitting part even though the output of the power supply of the transmitting part falls down or the like and also performing fast processing. SOLUTION: An electronic blackboard in the form of execution is provided with a pen provided an oscillation coil generating an alternating field and a writing panel on which a plurality of loop coils that are magnetically connectable to the alternating field are provided, reads coordinates by the induced voltage of the loop coils induced by the pen and electronically records the coordinates. When the pen exists on the center line C2 of a coil X2 in parallelly provided coils X1, X2 and X3, the voltage of a point Pc on a graph ex2' in the X coordinate of a point Pa is regarded as a maximum voltage in the coil X2 because the voltage values of graphs ex1' and ex3' induced by the coils X1 and X2 become equal at the point Pa, and correct coordinates are read by correcting an input value with a ration to a voltage on a design at a point Pb.

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 calibrating a reference voltage for reading coordinates.

[0002]

2. Description of the Related Art For example, by using an electronic pen which is a marker pen having an oscillation coil for generating an alternating magnetic field, characters and figures can be formed on a white board on which a number of loop coils are laid in parallel in the X and Y directions. When drawn, 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, the value of the induced voltage is read on the board side, and the voltage value is converted into a distance away from the loop coil using table data or the like, whereby the coordinates of the electronic pen are obtained, and the locus of the electronic pen is recorded as digital data. A coordinate reading device such as an electronic blackboard has been proposed. With such an electronic blackboard, characters and figures drawn on a board formed as a whiteboard or flip chart are recorded electronically as they are, and it is convenient to copy characters and figures on the board without having to copy each time. there were. In this electronic blackboard, a value of an induced voltage induced in a loop coil laid in the board is compared with a reference voltage value when an electronic pen stored and set in advance is at the center of the loop coil. The distance between the electronic pen and the loop coil is obtained based on the voltage, and the coordinates are calculated.

[0003]

However, the value of the induced voltage when the electronic pen is located at the center of the loop coil depends on the drop of the power supply voltage of the electronic pen, the thickness of the flip chart attached on the board, and the like. And may cause a difference between the value of the actual induced voltage and the value of the induced voltage that would occur when the electronic pen, which is preset and stored, is at the center of the loop coil. is there. In this case, the value of the voltage actually induced and actually measured in the loop coil laid in the board is calculated based on the reference value when the electronic pen stored in advance and stored at the center of the loop coil. However, even when trying to determine the distance between the electronic pen and the loop coil, since the voltage value when the electronic pen is actually at the center of the loop coil and the reference voltage value are different, the exact distance between the electronic pen and the loop coil is different. It cannot be calculated and an error occurs in the coordinates. Therefore, there has been a problem that inconsistency arises between characters and figures drawn on the board and data recorded electronically.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and provides a coordinate reading device capable of accurately reading the coordinates of a transmission unit and performing high-speed processing even if the output of a power supply of the transmission unit is reduced. The purpose is to do.

[0005]

According to a first aspect of the present invention, there is provided a coordinate reading apparatus comprising: a transmitting unit having an oscillation coil for generating an alternating magnetic field having a predetermined frequency; And a receiving unit having a board unit on which a plurality of loop coils that can be magnetically coupled are provided. The position of the transmitting unit is determined by an induced voltage value of the loop coil induced by an alternating magnetic field generated by the transmitting unit. The plurality of loop coils are laid in parallel, and an arbitrary first loop coil of the plurality of loop coils and a second loop coil disposed on both sides thereof are provided. And in the third loop coil,
At the coordinate position in the width direction of the loop coil of the transmission unit where the induced voltage values of the second loop coil and the third loop coil induced by the transmission unit on the board are equal, the first loop coil There is provided a calibration means for assuming the induced voltage value as the maximum induced voltage value of the first loop coil for detecting the position of the transmitting section.

In the coordinate reading device according to this configuration, the second loop coil and the third loop adjacent to the first loop coil to be calibrated, which are induced by the transmitter on the board, by the calibration means. At the coordinate position of the transmitter where the induced voltage value of the coil became equal,
The induced voltage value induced in the first loop coil is regarded as the maximum induced voltage value of the first loop coil for detecting the position of the transmitting unit, and the detected voltage value is corrected based on this voltage value. Since the position is calculated, the coordinates of the transmission unit can be accurately read even if the output of the power supply of the transmission unit decreases.

In the coordinate reading device according to the second aspect of the present invention,
In addition to the configuration of the coordinate reading device according to the first aspect, the plurality of loop coils are arranged so that a half of each width overlaps each other.

In the coordinate reading device according to this configuration, the calibration is performed from both the second loop coil and the third loop coil by arranging the loop coils so that the widths of the loop coils overlap each other. Enough signal can be obtained. Therefore, accurate calibration can be performed.

In the coordinate reading device according to the third aspect of the present invention,
In addition to the configuration of the coordinate reading device according to claim 1 or 2, a distance from one loop coil, and a voltage value induced from the transmitting unit at that position with reference to a previously stored reference voltage value. Calculating means for calculating coordinates of the transmitting unit using table data storing the correspondence between the voltage value and the ratio of the voltage value regarded as the maximum induced voltage value by the calibration means to the previously stored voltage value. The voltage value read from an arbitrary loop coil is corrected based on

[0010] In the coordinate reading device according to this configuration, the correspondence between the distance from one loop coil and the voltage value induced from the transmitting unit at that position based on the reference voltage value is stored in the table data in advance. By correcting the voltage value read from any loop coil based on the ratio between the voltage value regarded as the maximum induced voltage value by the calibration means and the reference voltage value stored in advance, the table data is corrected. , The position is determined by referring to, and a process faster than calculating and determining the position from the voltage value detected each time can be performed.

[0011] In the coordinate reading apparatus of the invention according to claim 4,
In addition to the configuration of the coordinate reading device according to any one of claims 1 to 3, it is determined whether the voltage value regarded as the maximum induced voltage value is equal to or less than a predetermined value. Determining means, and a notifying means for notifying when the voltage value considered as the maximum induced voltage value has become equal to or less than the predetermined value by the determining means. It is characterized by.

In the coordinate reading device according to this configuration, the determining means can determine whether the voltage value regarded as the maximum induced voltage value has become equal to or less than a predetermined value, and the notifying means determines the maximum induced voltage value in advance. Since it can be notified that the voltage has become equal to or less than the predetermined value, the voltage of the transmitting unit may be reduced while the transmitting unit is on the board, or the predetermined induced voltage may be determined due to the presence of a foreign substance that hinders the transmission. Can be notified to the user when the error does not occur on the board, and it is possible to prevent the discrepancy between the result of drawing with ink or the like on the board and the result of electronic reading.

[0013]

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.
FIG. 3 is an explanatory diagram showing the internal structure of the pen 60. FIG.
FIG. 3 is an explanatory diagram showing an electrical configuration of a pen 60 shown in FIG.

As shown in FIG. 2, 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.
It is wound 00 times to form a ring. In addition, the writing surface 21
a (see FIG. 1) is arranged at a distance of about 20 mm from the tip of the pen tip 62 that contacts the pen tip 62.

A push-button switch 67 is provided between the ink cartridge 63 and the circuit board 69 to supply and cut off electricity to the circuit board 69 and the like. The switch 67 connects the pen tip 62 to the writing surface 21a.
(See FIG. 1), the ink cartridge 63 is turned on when the ink cartridge 63 moves in the direction shown by the arrow F1, and when writing is stopped, the ink cartridge 63 returns to the direction shown by the arrow F2 by a spring in the switch 67 and turns off. That is, the writing surface 21 is
An alternating magnetic field is generated from the coil L1 only when writing is performed on a.

As shown in FIG. 3, the circuit mounted on the circuit board 69 (see FIG. 2) includes a pen 60 (see FIG. 2) such as the color of the ink and the thickness of the pen tip 62 (see FIG. 2). 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 CR oscillation circuit 69e, and an LC oscillation circuit The oscillation frequency of the circuit 69c is determined by the modulation frequency fm of the CR oscillation circuit 69e.
(Frequency Shift Keying) and an FSK circuit 69d for performing modulation. The oscillation frequency of the carrier is determined by the coil L1 which is the inductance and the capacitors C2 and C3 which are the capacitances of the LC oscillation circuit 69c, and the modulation frequency fm
Is determined by a capacitor C5 which is a capacitance constituting the CR oscillation circuit 69e, a resistor R2, and a variable resistor R3. Further, the frequency shift of the carrier oscillation frequency is determined by the capacitance of the capacitor C4, which is the capacitance of the FSK circuit 69d.

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. 2) 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. In addition,
The eraser 40 (see FIG. 1) also has a built-in coil.
3 in order to recognize the eraser 40 based on the signal generated at step 3 and calculate the erasure range, the eraser 40 is also provided with the modulation frequency f.
m is assigned.

In FIG. 3, a switch 67 (see FIG. 2)
Is turned on, the electricity of the battery 70 (see FIG. 2) is supplied to each circuit, and the output of the integrated circuit IC3 of the CR oscillation circuit 69e switches the gate of the MOS FET of the FSK circuit 69d and oscillates from the LC oscillation circuit 69c. Carrier is C
The frequency is modulated by the signal oscillated from the R 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 TC7SLU04F manufactured by Toshiba, and the integrated circuits IC2 and IC
C3 is TC7SLU04 manufactured by Toshiba. Also, M
The OS FET is 2SK2158. The resistors R1 and R2 are both 1 MΩ, and the variable range of the variable resistor R3 is 0.
Ω to 1 MΩ. Capacitors C2, C3, C4, C5
Are 2700pF, 1000pF and 270p, respectively.
F, 100 pF. Further, the battery 70 is connected to the LR 44
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. 4 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.
Is provided. The operation unit 30 includes a speaker 31 for reproducing sounds such as an operation sound and a warning sound, and data indicating the contents written on the writing surface 21a (hereinafter, abbreviated as writing data).
, A page number display LED 32 for displaying the number of pages storing 7 by a 7-segment LED, a page return button 33 for returning one page each time the button is pressed, a page forward button 34 for feeding one page each time the button is pressed, and a stored handwriting. An erase button 35 that erases one page each time data is pressed;
A printer output button 36 pressed to output the stored writing data to the printer 200 (FIG. 4); a PC output button 37 pressed to output the stored writing data to the PC 100 (FIG. 4); There is provided an input warning LED 39a for warning of the failure of the battery, a battery warning LED 39b for warning of battery exhaustion based on an input signal from the pen 60, and a power button 38 to be pressed to activate the electronic blackboard 1.

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. The plug 13 of the connection cable 204 connected to the printer 200 is connected to the connector 13b, and the connection cable 1 connected to the PC 100 is connected to the connector 13a.
04 plug 102 is connected. In other words, electronic blackboard 1
The writing data indicating the contents written on the writing surface 21a of P
Monitor 10 output to C100 and provided in PC 100
3, the content written on the electronic whiteboard 1 can be viewed. 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, 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 900 mm, and the width W1 is 600 mm. The frame 11 and the base 12 are 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. 5 shows the writing panel body 20.
It is explanatory drawing which shows each component. Writing panel body 20
Has a structure in which a writing sheet 21 having a writing surface 21a, a plate-shaped panel 22, a frame-shaped mounting panel 24 on which a loop coil 23 is laid, and a plate-shaped back panel 25 are sequentially stacked. In this embodiment, the writing sheet 21
Is formed by a PET (polyethylene terephthalate) film bonded to a thickness of 0.1 mm,
The panel 22 is formed of acrylic resin, ABS (acrylonitrile-butadiene-styrene copolymer), PC (polycarbonate) or the like to a thickness of 3.0 mm.
The mounting panel 24 is formed of a foamed resin material such as styrene foam to a thickness of 40 mm, and the back panel 25 is formed of a conductive material such as aluminum to a thickness of 1.0 mm. Furthermore, the entire thickness of the frame 11 that holds each end of the writing panel body 20 is 5
0 mm.

Next, the configuration of the loop coil 23 will be described with reference to FIG. FIG. 6A is an explanatory view showing a part of the configuration of the loop coil 23 shown in FIG. 5, and FIG. 6B is a diagram showing the configuration of the loop coil 23 shown in FIG.
FIG. 4 is an explanatory diagram showing a width P1 and an overlapping pitch P × 1/2. In the following description, a loop coil 23 arranged in the X-axis direction is referred to as an X coil, and a loop coil arranged in the Y-axis direction is referred to as a Y coil. Called. FIG.
As shown in (A), m X coils of 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 X-axis direction, and the Y-axis In the direction, n coils Y1 to Yn for detecting the Y coordinate are arranged orthogonally to the X coil. The X coil and the Y coil are each formed in a substantially rectangular shape,
The lengths of the long sides of the rectangular portion are P2X and P2Y, respectively.

As shown in FIG. 6B, the length of the short side of the rectangular portion of the X coil is formed to have a width P1, and the pitch between adjacent X coils is one half of the width P1. Each is overlapped. Each of the Y coils is also formed to have a width P1, and adjacent Y coils are each overlapped at a pitch of half the width P1. Each terminal 23a of the X coil is connected to the X coil switching circuit 50a, and each terminal 23b of the Y coil is connected to the Y coil switching circuit 5a.
0b (hereinafter collectively referred to as X, Y coil switching circuit 50) (see FIG. 9). As an example, in this embodiment, P1 = 50 mm, P2X = 680 m
m, P2Y = 980 mm. Also, m = 22, n =
34. Further, both the X coil and the Y coil are formed of a copper wire having a diameter of 0.345 mm and having an insulating film layer (for example, an enamel layer) on the surface.

Next, the position coordinate table 58a for detecting the position coordinates of the pen 60 on the writing surface 21a will be described with reference to FIGS. FIG. 7A is an explanatory diagram showing a part of the X coils X1 to X3, and FIG.
7A is a graph showing the relationship between the voltage ex generated in the X coils X1 to X3 shown in FIG. 7A and the distance in the width X direction, and FIG. 7C is a graph showing the relationship between the X coils X1 to X3 shown in FIG. It is a graph which shows the voltage difference between mutually adjacent loop coils of X3. FIG. 8A is an explanatory diagram showing the position coordinate table 58a in the form of a graph, FIG. 8B is an explanatory diagram of the position coordinate table 58a, and FIG. FIG. 9 is an explanatory diagram showing a storage state of a value.

In FIG. 7, the centers of the X coils X1, X2 and X3 are C1, C2 and C3, respectively.
The voltages generated at X2 and X3 are ex1, ex2,
ex3. As shown in FIG.
ex3 is the center C1 to C3 of the loop coil 23, respectively.
, And has a monomodal property that becomes smaller as the end in the longitudinal direction approaches. The coils are overlapped with each other at a half width of P1 such that the null point of the coil, that is, the point where the voltage becomes 0, is located farther from the center of the adjacent coil. Therefore, when the pen 60 exists at the coordinate position of the center of an arbitrary loop coil, the X coil X1
An induced voltage will be generated from any of the loop coils 23 adjacent to X3. 6 (A), (B),
In FIG. 7A, for convenience of explanation, each loop coil 2
In order to make it easy to see how 3 overlaps, the width is shown slightly smaller.

As shown in FIG. 7C, X coils X1 to X3
Has a maximum value on each of the centers C1 to C3 of the loop coils 23, and a midpoint 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 23 overlap.

For example, in FIG. 7C, (ex1-e
x2), the right half of the graph (the part shown by the solid line) is X
The distance from the center C1 of the coil X1 to the intermediate point Q1 of the portion where the X coil X2 is overlapped (1/2 of the overlap pitch,
That is, the relationship between (1/4 of P) and (ex1-ex2) is shown. Now, if the pen 60 exists at the point Q2,
If (ex1-ex2) is detected, the distance ΔX1 from the center C1 to the point Q2 can be detected, so that the X coordinate of the point Q2 can be obtained. In this embodiment, the coil width P1
Is 50 mm, so that P1 / 4 = 12.5 mm. For example, in the right half (portion shown by a solid line) of the graph showing (ex1-ex2) in FIG. 7C, the distance ΔX [mm] from the center line Cn of the loop coil Xn at an arbitrary position and the pen 60 8 bits obtained from the A / D conversion circuit 52 (see FIG. 9) when placed at that position
The relationship between the digital data and the amplitude DIFF converted into the digital data is as shown in the graph of FIG. When this graph is converted into a table format, a position coordinate table 58a shown in FIG. 8B is obtained. This position coordinate table 58a
Are 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, 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.
1 is a flowchart showing main control contents executed by the CPU 56 shown in FIG. Hereinafter, main control executed by the CPU 56 according to the flowchart of FIG. 11 will be described. First, the CPU 5 provided in the control unit 3 shown in FIG.
6 detects that the power button 38 (see FIG. 1) is pressed and the power is turned on (Step (hereinafter abbreviated as S) 100: Yes), the control program stored in the ROM 58 and the position coordinate table 58a. (FIG. 8 (B)
(See S200), and load coordinates into the work area of the RAM 59 (S200), and execute coordinate reading / pen information detection processing (S300).

Here, the coordinate reading / pen information detecting process (FIG. 11: S300) will be described with reference to FIG. 9 along the flowchart of FIG. 12 showing the flow. C
The PU 56 outputs a coil selection signal A (see FIG. 10B) for sequentially selecting the X coils X1 to Xm to an input / output circuit (I /
O) Scanning of X coils X1 to Xm is performed by outputting to X coil switching circuit 50a via 53 (S)
302). Subsequently, 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 coils is amplified by the amplifier 50c, and the amplified signal B (see FIG. 10B) is band-passed. An unnecessary band is filtered by the filter (BPF) 50 d, and the amplitude is detected by the amplitude detection circuit 51. Subsequently, the amplitude-detected signal C (see FIG. 10B) is converted into a digital signal corresponding to the amplitude, that is, a voltage value by the A / D conversion circuit 52, and the CPU 56
Is input to

Subsequently, if the pen 60 is not detected (S304: No), the CPU 56 ends the coordinate reading / pen information detection processing (S300 in FIG. 11) (end), and the page processing (S400 in FIG. 11). Here, since the pen has been detected, it is determined that the pen 60 has been detected (S304: Yes), and the voltage value e indicated by the digital signal input by scanning the X coils X1 to Xm by scanning the X coils X1 to Xm.
8C, the voltage value storage area 59a of the RAM 59 is associated with the coil number of the X coil as shown in FIG.
(S306). Subsequently, the CPU 56
Calculates the X coordinate of the pen 60 based on each voltage value stored in the voltage value storage area 59a by the following procedure (S308).

FIG. 13 is a flowchart showing in detail the procedure of the X coordinate calculation (S308) in FIG. Hereinafter, the procedure of the X coordinate calculation (S308) of FIG. 12 will be described in detail with reference to this flowchart. First, when the process is started (start), the maximum voltage value e (max)
The coil number of the X coil from which is extracted is defined as (max) and the X coil X (max) (hereinafter, the X coil X
(Max) is coil max, X coil X (max-1)
Is abbreviated as coil (max-1). ) (S802). Specifically, voltage values e1 to em of X coils X1 to Xm stored in voltage value storage area 59a.
Is selected, and the coil number (max) of the coil (max) that generated the voltage value e (max) is stored in the RAM 59. For example, FIG.
The pen 60 shown in (B) is located at the position of the point Q3, and the voltage values e1, e2, and X3 from the X coils X1, X2, and X3, respectively.
If e3 occurs, the maximum voltage value e2 is selected,
The X coil X2 that generated the voltage value e2 is a coil (m
ax), the coil number 2 of the X coil X2 is changed to (m
ax) = 2 is stored in the RAM 59.

Next, the CPU 56 determines that the coil number of the coil (max) showing the maximum voltage value = the coil number having a number one smaller than (max) = (max-1).
(Max-1) is extracted and stored in the RAM 59 (S
804). The coil number indicating the maximum voltage value = (m
coil number having a number one greater than (ax) = (max
+1) to extract the voltage e (max + 1)
(S806).

Next, the voltage e (max-1) and the voltage e (m
ax + 1) are compared to see if they are the same (S808).
If (max-1) = e (max + 1), then (S80
8: Yes), the voltage value e (max) at that time is taken as the actually measured value MAX, and the reference value g is divided by the actually measured value MAX.
It is set as r = g / MAX (S809).

Here, r is a correction coefficient, g is a reference value, and MAX is an actually measured value. A coil (max-1) adjacent to both sides of an arbitrary loop coil and a coil (ma
x + 1) (S808: Yes), the voltage value e actually induced in the coil (max) showing the largest voltage value
(Max) becomes the actually measured value MAX. The position at which the voltage value e (max) that is the actual measurement value MAX is obtained is the coordinate position of the center line C of the arbitrary coil (max).

The reference value g is a value obtained when the pen 60 is in a perfect state and the ideal state where there is no obstacle to the induction of voltage.
Is a design value of the induced voltage value e that will flow when it is on the center line C of an arbitrary coil X. And the correction value r
Is the ratio of the measured value MAX to the reference value g.

As described above, in S809, the measured value M
Since AX is detected, whether the measured value MAX satisfies the condition MAX ≦ ALM is compared with a predetermined reference value ALM by a comparison circuit (S810). The reference value ALM is a limit value at which coordinates can be correctly read after being corrected by calibration.
If M is exceeded (S810: No), the correct coordinates can be recognized by calibrating and correcting by calibration, so the procedure moves to S812. On the other hand, when the measured value MAX is equal to or smaller than the reference value ALM (S81).
0: Yes), since the coordinates may not be correctly recognized even by calibrating and correcting by the calibration, the battery warning LE of the writing panel 10 shown in FIG.
D39b is lit or blinked for a predetermined time to notify a battery alarm (S811). At this time, a warning sound may be emitted in conjunction with the speaker 31 at the same time. Here, the series of processing is continued without being stopped only by informing the user of the battery alarm. That is, if MAX ≦ ALM, the coordinates may not be recognized correctly, but conversely, they are often recognized correctly. Alternatively, even if there is some positional error, the coordinate position is read. In this case, if all the coordinate data on the writing surface 21a is discarded, the discrepancy that occurs between the recording on the writing surface and the electronically recorded data increases, so that only the battery alarm is notified (S811), and FIG. The other processes in the flowchart of FIG.

In step S808, whether or not the voltage e (max-1) is equal to the voltage e (max + 1) is compared.
ax-1) = e (max + 1) is not satisfied (S8
08: No), and further, the voltage e (max-1) and the voltage e
By comparing the magnitude with (max + 1) (S812), e
(Max-1)> e (max + 1), that is, RAM5
9 is greater than e (max-1).
If the voltage value is larger than 1) (S812: Yes),
The coil (max-1) is replaced by the coil (m
ax2), and sets SIDE as SIDE = 1 (S818). The difference is obtained by subtracting the voltage value e (max-1) of the coil (max-1) having the second largest voltage value from the voltage value e (max) of the coil (max) having the largest voltage value. Multiplied by the correction value r obtained earlier
FF is obtained (S820).

The voltage e (max-1) and the voltage e (m
ax + 1) (S812), and e (ma
x-1)> e (max + 1), that is, RAM
E (max + 1) stored in 59 is e (max + 1)
If the voltage value is larger than -1) (S812: No),
The coil (max + 1) is defined as the coil (max2), and the SI
The DE is set as SIDE = −1 (S814). Then, the voltage value e of the coil (max) showing the maximum voltage value
From (max), the difference is obtained by subtracting the voltage value e (max + 1) of the coil (max + 1) showing the second largest voltage value in this case, and the difference is multiplied by the correction value r obtained earlier to obtain D.
The IFF is obtained (S816).

For example, in the example of the point Q3 shown in FIG.
Since (max + 1)> e (max-1), (81
2: Yes), e being the voltage value e (max + 1) of the X coil X3 on both sides of e2 being the maximum voltage value e (max).
3 and e which is the voltage value e (max-1) of the X coil X1.
1, the voltage e (m) of the X coil X3 having a large voltage value.
ax + 1) which is equal to the second largest coil (max
2) is determined as the voltage value e (max2) of the RAM 5
9 and the variable SIDE is set to 1 (S81
8). Subsequently, the CPU 56

DIFF = r × (e (max) −e (max2))

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 (S822). Subsequently, the CPU 56 sets the coil number to (max),

X = (P1 / 2) × max + OFFSET × SIDE

To calculate the X coordinate X1 (S82).
4). Here, (P1 / 2) × max indicates the X coordinate of the center of the coil number (max). In the example shown in FIG.
X = (P1 / 2) × 2 + (e2-e3) × 1, and the X coordinate of the position of the point Q3 is a distance corresponding to (e2-e3) in the + direction of the X axis from the center line C2 of the X coil X2. For example, the coordinates are separated by ΔX2. Then, the CPU 56
The coil is scanned (S310), and the voltage value detected from each Y coil is stored in the Y coil voltage value storage area of the RAM 59 (S312). Subsequently, the CPU 56
Calculates the Y coordinate of the pen 60 using the same method as the calculation of the X coordinate in S308 described above (S314).

Here, the calibration of the electronic whiteboard 1 of the present embodiment will be described. In calculating the position, as shown in the flow chart of FIG. 13, each X coil obtained by scanning the X coil (FIG. 12: S302).
By comparing the voltage values from the coils, the maximum voltage value e (ma
The coil (max) from which x) was obtained is determined (S802),
Next, after obtaining a coil (max2) from which a large voltage is obtained (S804 to S812), a difference between the two is obtained, and an SIDE indicating a direction from the center line C of the coil (max) is obtained (S814, S818). , DI obtained based on the voltage difference
From FF (S816, S820), position coordinate table 5
8a, the distance is calculated by obtaining the OFFSET, and the X coordinate is obtained from the direction and the distance from the center line C of the coil (max) at which the maximum voltage value e (max) is obtained (S822). ).

Here, FIG. 14A shows coils X1 and X
FIG. 14B is a diagram illustrating an arrangement of X2 and X3, and FIG. 14B is a diagram illustrating an induced voltage obtained by scanning the X coil. FIG. 14C is a graph showing the difference between the voltages of the adjacent coils X at that time. Here, the coils X1 to X3 will be described as an example. As shown in FIG. 14A, the coils X1, X2, and X3 are arranged so as to overlap by 1/2 of the width P1 in the X coordinate direction. According to FIG.
An induced voltage is induced as shown in graphs ex1, ex2 and ex3 shown in FIG. Then, at point Pa in FIG. 14B, voltages e1 and e3 induced in coil X1 and coil X3 become equal. Here, graph e
Since the curves drawn by x1, ex2, and ex3 are the same curves under the same conditions, the graphs ex1 and ex3
Intersect at the X coordinate of the center line C2 of the coil X2. Then, since the maximum voltage value e (max) induced in the coil X2 is the X coordinate of the center line C2, when the voltages e1 and e3 induced in the coil X1 and the coil X3 become equal to each other, the coil The voltage value of the voltage ex2 induced at X2 at the point Pb, that is, the voltage value e (max) is the maximum voltage value of the coil X2.
In this case, the voltage value e (max) is equal to the voltage of the reference value g.

However, if the voltage of the power supply of the pen 60 drops,
In the case where a foreign matter such as a flip chart is stuck on the writing surface 21a, even when the pen 60 is located at the position of the coordinates of the center line C2, the voltage induced in the coil X2 does not reach the predetermined reference value g, Lower graphs ex1 ', ex2', ex
It becomes the voltage on the graph shown in 3 '. And the voltage e1,
The voltage value obtained from the coil X2 when e3 is equal to
An actual measurement value MAX indicated at a point Pc lower than the reference value g is obtained. The voltage difference is also shown in FIG.
2), (ex2-ex1), (ex2-ex3), (e)
x3-ex2), not (ex1'-
ex2 '), (ex2'-ex1'), (ex2'-e
x3 ') and a graph like (ex3'-ex2').

Here, FIG. 15 shows a state in FIG.
4 shows a graph when the voltage induced in the pen 60 is reduced. Hereinafter, a method of reading coordinates when the voltage induced in the pen 60 decreases will be described with reference to FIG. Here, the distance ΔX [mm] from the center line C of the loop coil X at an arbitrary position shown in FIG. 8A and the A / D conversion circuit 52 when the pen 60 is located at that position (see FIG. 9). The relationship with the amplitude DIFF converted into 8-bit digital data obtained from the above is created on the assumption that the reference value g is obtained when the pen 60 is on the center line C. That is, at the center line C of the X coil, the pen 6
When the voltage induced by 0 is lower than the reference value g that can be originally obtained due to the decrease in the voltage of the power supply of the pen 60 itself, as shown in FIG.
If the value of d1 is obtained, the distance ΔX4 is obtained based on the graph DIFF1 if there is no drop in the induced voltage, but actually, as shown in FIG.
, The actual distance is a distance as indicated by ΔX3. Therefore, the position coordinate table 5 shown in FIG. 8B created based on the graph shown in FIG.
Even if the distance ΔX is calculated based on 8a, an error occurs, and a correct position cannot be obtained. Where the correct distance ΔX
In order to find 3, the value dd1 of the 8-bit digital data detected from the voltage value obtained by the X coil scan as shown in FIG. 15 is corrected by the voltage drop so that the distance ΔX3 can be correctly read by the graph DIFF1. Then, if the 8-bit digital data value is set to dd2, even if the voltage drops, the correct distance ΔX3
Can be detected.

Therefore, calibration is performed to correct the voltage value at the center line C of the coil X. That is,
As described above, the actually measured value MAX is obtained, compared with the reference value g, and the rate of the decrease is calculated by g / MAX to obtain the correction value r. Then, by multiplying the difference between the voltages e actually obtained by scanning by the correction constant r, the correct distance ΔX3 is obtained using the position coordinate table 58b created based on the reference value g. Although the calibration procedure has been described for the X coil, the procedure for the Y coordinate calculation (S314 in FIG. 12) for the Y coil is also performed in the same manner, and a description thereof will be omitted. Hereinafter, similarly, the description of the X coil is replaced with the description of the Y coil, and the description of the Y coil is omitted.

When the measured value MAX is equal to or smaller than the predetermined value ALM, the battery warning LED 39b notifies that the voltage of the battery 70 (see FIG. 3) is low.

Next, an electrical configuration and control for the CPU 56 to determine the pen attribute will be described with reference to FIGS.
This will be described with reference to FIG.

FIG. 16A shows an output signal (hereinafter, referred to as a CR signal) of the CR oscillation circuit 69e (see FIG. 3).
An output signal of the LC oscillation circuit 69c (see FIG. 3) (hereinafter referred to as a carrier signal) and an output signal of the limiter circuit 54 (see FIG. 9) (hereinafter referred to as a limiter output signal).
FIG. 20 is an explanatory diagram showing a relationship between the count value and a count value K by a count circuit 55a (see FIG. 19). FIG. 16B is an explanatory diagram showing how the count value K stored in the shift register 55b (see FIG. 19) shifts. FIG. 17 is an explanatory diagram showing signal waveforms appearing at various parts of the FSK demodulation circuit 55 shown in FIG.

FIG. 18 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 S318, and FIG. FIG. 10 is an explanatory diagram showing an electrical configuration (see FIG. 9).
FIG. 20A is an explanatory diagram showing the relationship between the threshold value judgment output by the absolute value comparator 55f (see FIG. 19) and the judgment cycle of the CPU 56, and FIG. It is explanatory drawing which shows a mode that moves. FIG. 21A shows the counter 5 in S318.
FIG. 21 is a flowchart showing the flow of 5g processing, and FIG.
(B) is a flowchart showing the flow of the processing of the adder 55i in S318. The carrier signal shown in FIG. 16A has a center frequency of 410 kHz and a frequency shift of ± 15 kHz, for example, as described above. However, in order to make the description easy to understand, FIG.
Exaggerating the frequency 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. 16A, 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: S318).

Next, referring to FIG. 18, FSK demodulation circuit 5
Operation 5 will be described in detail. Band pass filter 50d
Is output by the limiter circuit 54 as shown in FIG.
7 (A) is converted to a square wave limiter output signal,
The signal is output to the FSK demodulation circuit 55. When the FSK demodulation circuit 55 detects the rise of the limiter output signal (S10 in FIG. 18: Yes), the system clock (C
LK) to start counting the cycle of the limiter output signal (S12). When the next rise of the limiter output signal is detected (S14: Yes), the count value K is output to the shift register 55b (S16), and the count is performed. The value K is reset (S18). 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
16B, as shown in FIG. 16B, the count value K for one cycle of the limiter output signal is stored for eight cycles of K1 to K8, and the oldest count value K is stored every time the newest count value K is fetched. Discard and shift each count value K one by one. As shown in FIG. 19, the first weighted average circuit 5
5c 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 a first weighted average value). Output to the subtractor 55e. The second weighted averaging circuit 55d includes a shift register 55b
, And calculates a weighted average value from the oldest count value K to the third oldest count value K, and calculates the weighted average value (hereinafter, referred to as a second weighted average value) of the subtractor 55.
e.

The subtractor 55e calculates a difference Δm between the first weighted average value and the second weighted average value, and outputs the difference Δm to the absolute value comparator 55f (S20 in FIG. 18). For example, in FIG. 16A, when the first weighted average circuit 55c calculates the weighted average value 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 count 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. In other words, if the period of the changing point of the period of the CR signal is detected, the period of the CR signal can be detected, so that the information of the pen attribute can be recognized.

As described above, the weighted averaging circuit performs the weighted averaging on the count values K counted at different times, so that 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. 20, 〜 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 (see FIG. 18).
(S22), when it is determined that the difference Δm is equal to or larger than the threshold value m1 (S22: Yes), the threshold determination output is changed from a low level to a high level (S24). That is, it is determined that the cycle of the limiter output signal has changed (the rising edge of the CR signal has been detected). For example, FIG.
The count value K by the count circuit 55a of the shorter cycle TB of the limiter output signal shown in FIG.
If the count value K is 16 and the threshold value m1 is 2, since the count values K1 to K6 are all 10, the first weighted average value = (K1 + K2 + K3) / 3 = 10. Since the count values K7 and K8 are both 16,
Second weighted average value = (K6 + K7 + K8) / 3 = 42/3
= 14, and the difference Δm = 10−14 = −4.

The first weighted average circuit 55c and the second
A weighted averaging circuit 55d, a ratio of the carrier frequency (the oscillation frequency of the LC oscillation circuit 69c) to the modulation frequency fm,
The decision is made based on the complexity of the circuit. 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 between the system clock frequency and the frequency of the carrier, and the frequency of the system clock is large enough to discriminate the change in the frequency. Set to.

Therefore, since (absolute value of difference Δm = 4)> (threshold value m1 = 2), the threshold value judgment output changes from low level to high level (FIG. 18: S24). 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. Second
Since both the weighted average circuits 55d 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 judgment 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. 21A: Yes), the time during which the judgment output is at the high level, that is, The half cycle of the judgment output is counted using the system clock (S32). Let the count value be K ((B1) in FIG. 20B).
When the absolute value comparator 55f determines that the difference Δm is equal to or larger than the threshold value m1 (S2 in FIG. 18).
2: Yes), the threshold determination output is changed from the high level to the 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). Thereby, the counter 55g
Detects that the threshold determination output has changed from the high level to the low level (FIG. 21A: S34: Ye).
s), and outputs the count value to the register 55h as shown in (B2) of FIG. 20 (B) (S36). Subsequently, the counter 55g resets the count value (S3
8) Count the time during which the threshold value judgment output is at the low level, that is, the half cycle of the threshold value judgment output (S32 via circle B). The count value is used.

Subsequently, when 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 (S50: Yes), the count value held by the counter 55g is The count value held by the register 55h is added (S52), and the added value is output to the CPU 56 (S56). At this time, the counter 55g outputs the count value to the register 55h as shown in (B3) of FIG. 20B (S36 of FIG. 21A). Then, the CPU 56 reads the value of the FSK demodulation circuit 55 via the input / output circuit 53, that is, the added value (FIG. 1).
2: S316, see FIG. 19), and determine the pen attribute based on the read addition value (S318). For example, when the added value is 245, it is determined that the pen attribute is black and thick as shown in FIG. Also, C
The PU 56 associates the pen attributes with the XY coordinates and stores them in the RAM.
59. The writing data stored in such a form is output to, for example, the printer 200 (see FIG. 4) and printed in black. The data is output to the PC 100 (see FIG. 4) and displayed in black on the monitor 103 (see FIG. 4).
That is, the writing data can be reproduced according to the pen attribute.

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. 20B).
3)). Thereafter, every time the threshold determination output changes, the count value K of the counter 55g is output to the register 55h, and the adder 55i outputs the count value K of the counter 55g and the count value K held in the register 55h.
Are repeated, and the cycle of outputting the added value to the CPU 56 is repeated. That is, as shown in FIG. 20B, the adder 55i adds the latest count value K counted by the counter 55g and the immediately preceding count value K held in the register 55h, and adds the result. To output to the CPU 56, as shown in FIG.
Determines the pen attribute based on the latest count value K and the sum of 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, the added value of one cycle of time t2 to t4 half a cycle after time t1 may be taken, so that the pen attribute can be determined at high speed.

As described above, the X and Y coil scans (S3
02, S310), the pen 60 shown in FIG. 1 is applied to the writing surface 21a and writing is started. 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 is released. And the pen attributes and XY of a series of pens 60 until no is detected (S304: No)
The coordinates and the coordinates are stored in a locus storage area (not shown) of the RAM 59 (S320). The position of the pen 60 is sequentially stored in the trajectory storage area as the X coordinate and the Y coordinate in the dot matrix arranged in the X-axis and Y-axis directions together with the attributes of the pen. Thus, FIG.
The procedure of the coordinate reading / pen information detection process (S300) shown in FIG.

Here, returning to the flowchart of FIG. 11, the description will be continued with reference to FIG. When the procedure of the coordinate reading / pen information detection processing (S300) is completed, the CPU 56
When the page return button 33, the page forward button 34, and the delete button 35 are pressed, page processing (S400) such as returning, sending, or deleting stored writing data in page units is performed. In the page processing, the CPU 5
Reference numeral 6 denotes various buttons provided on the operation unit 30 (see FIG. 1).
The switching signal generated by the operation of I / F circuit 5
7 (see FIG. 9), and performs page processing such as returning or sending the page storing the position coordinate data stored in the RAM 59 in page units, or deleting the position coordinate data in page units. I do. Also, CP
U56 converts the position coordinate data of the target page from the position data stored in the RAM 59 into an appropriate format, and converts the data into a PC 100 or a printer 200 (see FIG. 4).
A data output process (S500) for outputting the data to the computer is executed.

Further, the CPU 56 operates the audio circuit 31a based on a switching signal generated when various buttons are pressed, and emits operation sounds such as "P" and "P" from the speaker (SP) 31. The voice output processing is executed (S600), and when one round of processing is completed, S100
To S600 are 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, the control unit 3 (see FIG. 9), which is a calibration means, is an arbitrary loop coil 23 to be calibrated which is induced by the pen 60 (see FIG. 1), which is a transmitting unit on the writing surface 21a; At the coordinates where the induced voltage value e of the adjacent loop coil 23 on both sides becomes equal, the voltage value e (max) induced on the sandwiched loop coil is taken as the actually measured value MAX, and a reference value g set in advance. The correction value r is obtained from the ratio of the above, and the voltage value e detected based on the correction value r is corrected, so that the coordinate position can be calculated correctly. For this reason, even if the output of the power supply of the pen 60 is reduced, it is possible to obtain the effect that the coordinates of the pen 60 can be accurately read.

In the electronic blackboard 1, the loop coil 23
Are arranged so that the widths of each half of the width P1 overlap each other, so that the first
There is an effect that signals sufficient for calibration can be obtained from both the second loop coil and the third loop coil on both sides of the loop coil. Therefore, there is an effect that accurate calibration can be performed.

Further, the distance OFF from one loop coil 23 is stored in the position coordinate table 58a which is table data.
SET and pen 60 at that position based on reference value g
Is stored in advance, and based on the ratio between the voltage value g regarded as the maximum induced voltage value by the calibration means and the reference voltage value g stored in advance. There is an effect that the position can be determined by referring to the table data by correcting the voltage value e read from an arbitrary loop coil. For this reason, there is an effect that faster processing is possible than when the position is calculated and determined from the voltage value e detected each time.

Then, the voltage value MAX regarded as the maximum induced voltage value is stored in the ROM 56 by the CPU 56 as the judgment means.
It is possible to determine whether or not the value has become equal to or less than a predetermined value ALM in a storage area 58, and a battery warning LED 39 serving as a notification means.
b or the speaker 31 can notify that the maximum induced voltage value MAX has become equal to or less than a predetermined value ALM. Therefore, when the pen 60 is on the writing surface 21a and the voltage of the battery 70 drops or a predetermined induced voltage is not generated on the loop coil 23 due to the presence of a foreign substance such as a flip chart that hinders transmission. In addition, it is possible to notify the user of this, and it is possible to prevent an inconsistency between the result of drawing with ink or the like on the board and the result of electronic reading.

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 and changes can be made without departing from the spirit of the present invention. What is possible can easily be inferred.

[0077]

According to the coordinate reading device of the first aspect of the present invention, the first means to be calibrated induced by the transmitting unit on the board by the calibration means.
Detecting the induced voltage value induced in the first loop coil at the coordinate position of the transmission unit where the induced voltage values of the second loop coil and the third loop coil adjacent to the first loop coil are equal to each other; This is regarded as the maximum induced voltage value of the first loop coil for performing the above, and the voltage value detected based on this voltage value can be corrected to calculate the position. Therefore, even if the output of the power supply of the transmission unit is reduced, the effect of being able to accurately read the coordinates of the transmission unit is achieved.

According to the coordinate reading apparatus of the second aspect of the present invention, in addition to the effect of the coordinate reading apparatus of the first aspect of the present invention, the width of each of the loop coils is set so as to overlap each other by half. Is advantageous in that signals sufficient for calibration can be obtained from both the second loop coil and the third loop coil. Therefore, there is an effect that accurate calibration can be performed.

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, the distance from one loop coil to the table data and the reference voltage The correspondence with the voltage value induced from the transmitting unit at that position based on the value is stored in advance, and the voltage value regarded as the maximum induced voltage value by the calibration means, and the reference voltage value stored in advance By correcting the voltage value read from an arbitrary loop coil based on the ratio of the above, there is an effect that the position can be determined by referring to the table data. Therefore, there is an effect that it is possible to perform faster processing than calculating and determining the position from the voltage value detected each time.

According to the coordinate reading device of the invention according to claim 4, in addition to the effect of the coordinate reading device according to any one of claims 1 to 3, the judgment means regards the coordinate device as the maximum induced voltage value. It is possible to determine whether or not the detected voltage value has become equal to or less than a predetermined value, and it is possible to notify that the maximum induced voltage value has become equal to or less than the predetermined value by the notification means. Therefore, when the voltage of the transmitting unit is reduced while the transmitting unit is on the board, or when a predetermined induced voltage is not generated on the board due to the presence of a foreign substance that hinders transmission, the user is notified of this. This makes it possible to prevent an inconsistency between the result of drawing with ink or the like on the board and the result of electronic reading.

[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 an internal structure of a pen 60.

FIG. 3 is an explanatory diagram illustrating an electrical configuration of a pen 60 illustrated in FIG. 2;

FIG. 4 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. 5 is an explanatory diagram showing each component of the writing panel 20;

6 (A) is an explanatory view showing a configuration of the loop coil 23 shown in FIG. 5 with a part thereof omitted; FIG. (B) It is explanatory drawing which shows the width | variety and overlap pitch of the loop coil 23 shown in FIG. 6 (A).

FIG. 7A is an explanatory view showing a part of X coils X1 to X3. 8B is a graph showing a relationship between a voltage generated in the X coils X1 to X3 shown in FIG. 7A and a distance in a width direction. (C) It is a graph which shows the voltage difference between mutually adjacent loop coils of X coil X1-X3 shown in FIG. 7 (A).

FIG. 8A 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. 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.

FIG. 13 is a flowchart showing in detail a procedure of an X coordinate calculation (S308) in FIG. 12;

FIG. 14A is a diagram illustrating an arrangement of coils X1, X2, and X3. FIG. 3B is a diagram illustrating an induced voltage obtained by scanning an X coil. (C) It is a graph which shows the difference of the voltage of the adjacent coil X at that time.

FIG. 15 is a graph showing a case where the voltage induced in the pen 60 is reduced in FIG.

FIG. 16A 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.

FIG. 17 is an explanatory diagram showing signal waveforms appearing at various parts of the FSK demodulation circuit 55 shown in FIG.

FIG. 18 is a flowchart showing a flow of processing (pen attribute detection processing 1) from a count circuit 55a constituting the FSK demodulation circuit 55 to an absolute value comparator 55f.

FIG. 19 is an explanatory diagram showing an electrical configuration of the FSK demodulation circuit 55.

20A 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. 21A is a flowchart showing the flow of processing of a counter 55g in S318. (B) It is a flowchart which shows the flow of a process of the adder 55i in S318.

[Explanation of symbols]

 Reference Signs List 1 electronic blackboard 10 writing panel 20 writing panel main body 21a writing surface 23 loop coil 56 CPU 58 ROM 59 RAM 60 pen (writing means)

Claims (4)

[Claims] 1. A transmitter comprising an oscillation coil for generating an alternating magnetic field of a predetermined frequency, and a receiver comprising a board on which a plurality of loop coils capable of being magnetically coupled with the alternating magnetic field are provided. A coordinate reading device that reads coordinates of a position of the transmission unit by an induced voltage value of the loop coil induced by an alternating magnetic field generated by the transmission unit; wherein the plurality of loop coils are laid in parallel; An arbitrary first loop coil of the loop coils, and second and third loop coils disposed on both sides thereof, the second loop coil induced by the transmitting unit on the board And at the coordinate position in the width direction of the loop coil of the transmitting unit where the induced voltage values of the third loop coil become equal, the induced voltage induced by the first loop coil. Coordinate reading apparatus characterized by comprising the calibration means be regarded as a maximum induced voltage of the first loop coil for the voltage value detecting the position of the transmission portion. 2. The coordinate reading device according to claim 1, wherein the plurality of loop coils are arranged so that a half of each width overlaps each other. 3. The transmission unit using table data storing a correspondence between a distance from one loop coil and a voltage value induced from the transmission unit at a position based on a reference voltage value stored in advance. Calculation means for calculating coordinates of the voltage read from any loop coil based on a ratio between the voltage value regarded as the maximum induced voltage value and the previously stored voltage value by the calibration means. The coordinate reading device according to claim 1, wherein the value is corrected. 4. A judging means for judging whether or not the voltage value regarded as the maximum induced voltage value has become equal to or less than a predetermined value, wherein the judging means considers the voltage value as the maximum induced voltage value. 4. A notifying means for notifying the determined voltage value when it is determined that the voltage value has become equal to or less than the predetermined value. Coordinate reading device.