JP2001051786A - Coordinate input pen and coordinate reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a coordinate input pen and a coordinate reader improved in the reading resolution of the position coordinate of the coordinate input pen. SOLUTION: In this coordinate reader, coils L1, L2 incorporated in a pen 60 simultaneously output the alternate magnetic fields each different in frequencies. The alternate magnetic fields outputted from the coils L1, L2 are FSK- modulated by two CR oscillation circuits mounted to a circuit substrate 70 respectively. A signal for FSK-modulating the alternate magnetic field of the coil L1 is set to a period corresponding to the attribute of the pen 60. A signal for FSK-modulating the alternate magnetic field of the coil L2, on the other hand, has its frequency varied by the resistance value of a writing pressure sensor 68. Thus, a receiving side separates an induction signal generated at a sense coil by the alternate magnetic fields simultaneously outputted from the coils L1, L2 by each frequency of each alternate magnetic field by a band pass filter and FSK-demodulates it to detect the attribute and the writing pressure of the pen 60.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coordinate input pen for outputting an alternating magnetic field from a coil and inputting coordinates on a coordinate input sheet, and laying on the coordinate input sheet by the alternating magnetic field output from the coordinate input pen. And a coordinate reading device for reading the position coordinates of the coordinate input pen based on a guiding signal generated in the conducted wire.

[0002]

2. Description of the Related Art Conventionally, as the above-mentioned coordinate input pen and coordinate reading device, for example, those described in Japanese Patent Application Laid-Open No. 2-23012 are known. FIG. 24A is an explanatory diagram showing the configuration of the above-described conventional coordinate input pen and coordinate reading device by blocks, and FIG. 24B shows the data output timing of the coordinate detection circuit 308 shown in FIG. 6 is a timing chart showing the relationship between the output timing of the coordinate correction circuit 310 and the output timing. The two coils LA and LB incorporated in the coordinate input pen 300 are respectively connected to the switch circuit 3
06. Then, the two coils L
A and LB each generate an induced voltage signal by being magnetically coupled to a conductor (not shown) laid below the input surface of the tablet 312. One of the induced voltage signals, which is selectively connected by the switch circuit 306, is guided to the coordinate detection circuit 308. The coordinate detection circuit 308
By detecting the appearance timing of the induced voltage signal selectively connected by the switch circuit 306, the coil L
Data D1 indicating the position coordinates of A or the coil LB is generated, and the data D1 is sent to the coordinate correction circuit 310. The coordinate correction circuit 310 calculates the position coordinates of the pen tip of the coordinate input pen 300 based on the two data D1 indicating the position coordinates of the coil LA and the coil LB, and outputs data D2 indicating the calculation result.

[0003]

However, since the above-mentioned conventional device has a configuration in which the two coils LA and LB are alternately switched by the switch circuit 306, two data A indicating the position coordinates of both coils are prepared. , The position coordinates of the pen tip of the coordinate input pen 300 are calculated, so that the number of position coordinates that can be calculated is small. That is, since the number of position coordinate data obtained is small, there is a problem that the reading resolution of the position coordinates of the coordinate input pen 300 is low.

Therefore, the present invention has been made to solve the above-mentioned problem, and its object is to
An object of the present invention is to realize a coordinate input pen and a coordinate reading device that can increase the reading resolution of position coordinates of a coordinate input pen.

[0005]

Means for Solving the Problems, Functions and Effects of the Invention
In order to achieve the above object, the present invention provides a coordinate input sheet in which a plurality of conductors are laid below a coordinate input surface, and an alternating magnetic field magnetically coupled to the conductors. And a coordinate input pen having a plurality of coils that output a plurality of coils, by scanning the plurality of conductors,
The coordinate input pen used in a coordinate reading device that detects an induction signal generated in the conductive wire by an alternating magnetic field output from the plurality of coils and reads a position coordinate of the coordinate input pen based on the detected induction signal. , The plurality of coils use a technical means of simultaneously outputting alternating magnetic fields having different frequencies.

Since the plurality of coils output alternating magnetic fields having different frequencies, the position coordinates of each coil can be detected by detecting the frequency of the output alternating magnetic field. If the relationship between the coordinate input pen and the actual position coordinates of the pen tip is determined, the actual position coordinates of the pen tip based on the position coordinates of each coil,
That is, it is possible to detect accurate position coordinates in consideration of the inclination of the coordinate input pen. In addition, since the plurality of coils simultaneously output alternating magnetic fields having different frequencies, the induction signals generated in the conductors can be detected at the same timing by the alternating magnetic fields output from the plurality of coils. It is possible to calculate the position coordinates of the coordinate input pen faster than a conventional one that alternately detects the guidance signal generated from the pen. Therefore, since the position coordinates of the coordinate input pen can be calculated quickly, the number of data of the obtained position coordinates can be increased, and the reading resolution of the position coordinates of the coordinate input pen can be increased.

According to a second aspect of the present invention, in the coordinate input pen according to the first aspect, among the plurality of coils,
A technical means is used in which the output is set to be larger as the coil is farther from the pen tip.

That is, by setting the output to be larger as the coil is farther from the pen tip, the magnitude of the output of each coil can be made to match the output of the coil closest to the pen tip. Since the reading error of the position coordinate of the coordinate input pen due to the variation of the size of the coordinate input pen can be eliminated, the reading accuracy of the position coordinate of the coordinate input pen can be improved.

According to a third aspect of the present invention, in the coordinate input pen according to the first or second aspect, a technical means is used in which at least the coil closest to the pen tip is an air-core coil. .

In order to make the output of each coil at the pen tip constant, it is necessary that the output of the coil closest to the pen tip be at least the minimum. Here, as means for reducing the output of the coil, it is conceivable to reduce the number of turns of the coil compared to other coils or to change the magnetic material of the core to a weaker one. The air core means can easily reduce the output. Therefore, by making the coil closest to the pen tip at least the air core, the output of the coil closest to the pen tip can be easily minimized.

According to a fourth aspect of the present invention, in the coordinate input pen according to any one of the first to third aspects, a switch operated by pressing the pen tip is provided, and The coil uses a technical means that is configured to simultaneously output the respective alternating magnetic fields in conjunction with the switch.

That is, when the pen tip is pressed, the alternating magnetic field can be simultaneously output from each coil, so that the power consumption of the power supply for supplying the current to each coil can be reduced as compared with the one that outputs the alternating magnetic field even when not writing. can do. In addition, since the coil can be turned on and off in conjunction with the pressing of the pen tip, the trouble of switching on and off every time writing is interrupted and resumed can be omitted. Furthermore, forgetting to switch off when writing is stopped can be prevented.

According to a fifth aspect of the present invention, in the coordinate input pen according to any one of the first to fourth aspects, an information carrier for carrying predetermined information using an alternating magnetic field output from the coil. Use the technical means that the means are provided.

That is, predetermined information, for example, pen attribute information such as the color of the ink of the coordinate input pen and the thickness of the pen tip can be conveyed using the alternating magnetic field output from the coil. Also, a plurality of pieces of information can be transmitted by carrying different pieces of predetermined information for each of the plurality of coils.

According to a sixth aspect of the present invention, in the coordinate input pen according to the fifth aspect, a pen pressure detecting means for detecting a pen pressure applied to the pen tip is provided, and the predetermined information is Technical means is used which is pen pressure information indicating the pen pressure detected by the pen pressure detecting means.

In other words, pen pressure information indicating the pen pressure applied to the pen tip can be conveyed using the alternating magnetic field. Therefore, by detecting the pen pressure information conveyed by the alternating magnetic field, the coordinate input pen can be used to detect the pen pressure. The trajectory drawn on the input surface can be reproduced with shading, for example, according to the pen pressure.

According to a seventh aspect of the present invention, there is provided a coordinate input pen according to any one of the first to sixth aspects, and a coordinate input sheet on which a plurality of conductive wires are laid below the coordinate input surface. By scanning the plurality of conductors, an induction signal generated in the conductor by an alternating magnetic field simultaneously output from the plurality of coils is detected, and based on the detected induction signal, the position coordinates of the coordinate input pen are detected. And a reading means for reading the data.

That is, as described above, since the plurality of coils provided in the coordinate input pen simultaneously output the alternating magnetic field, the induction signal generated in the conductive wire by the simultaneously output alternating magnetic field is scanned in one scan. Can be detected. Therefore, an induction signal generated in a conductor by an alternating magnetic field generated from one coil is detected by one scanning,
Since the number of data obtained by one scan is large, the reading accuracy of the position coordinates of the coordinate input pen can be improved.

According to an eighth aspect of the present invention, in the coordinate reading apparatus according to the seventh aspect, the coordinate input pen has a single cycle or a single duty set for each attribute information of the coordinate input pen. Using a signal having a ratio, an alternating magnetic field generated from a predetermined coil among the plurality of coils is angle-modulated, and the reading unit demodulates the induction signal to thereby generate an alternating magnetic field generated from the coordinate input pen. A technical means for detecting the single cycle or the single duty ratio of the magnetic field and recognizing attribute information of the coordinate input pen based on the detected cycle or the duty ratio is used.

That is, since the period or duty ratio of the signal that angularly modulates the alternating magnetic field generated from the coordinate input pen is single, and the period or the duty ratio differs depending on the attribute information of the coordinate input pen, the reading means uses the alternating magnetic field. The attribute information of the coordinate input pen can be recognized only by detecting the length of one cycle in which the cycle of the coordinate input pen changes. Further, the attribute information can be recognized only by a slight difference in the cycle or duty ratio of the signal for angularly modulating the alternating magnetic field. For example, the attribute information can be recognized only by a difference in the cycle or duty ratio by at least one cycle of the system clock of the reading unit. Therefore, a very large number of types of attribute information can be transmitted, and the attribute information can be recognized in a short time.

Further, the alternating magnetic field generated from the coil of the coordinate input pen is angle-modulated by the signal to transmit the attribute information, and the induction signal generated in the conductor laid on the coordinate input sheet is demodulated to obtain the above-mentioned signal. A single cycle or a single duty ratio of the signal is detected, and the attribute information is recognized based on the detected cycle or the duty ratio. Since the period or phase, which is the portion shown, is not affected, the attribute information can be transmitted and received accurately.

According to a ninth aspect of the present invention, in the coordinate reading device according to the seventh or eighth aspect, an alternating magnetic field output from the plurality of coils converts an induction signal detected from the conductor into each alternating current. Technical means is used in which a separating means for separating into signals corresponding to the frequency of the magnetic field is provided.

In other words, the separation means separates the induction signal detected from the conductor into a signal corresponding to the frequency of the alternating magnetic field output from each coil, so that the signal is conveyed using the alternating magnetic field output from each coil. It is possible to detect predetermined information, for example, pen attribute information such as the color of the ink of the coordinate input pen and the thickness of the pen tip.

According to a tenth aspect of the present invention, in the coordinate reading apparatus according to the ninth aspect, information detecting means for detecting the predetermined information contained in the signal separated by the separating means is provided. The technical means of using.

That is, by detecting predetermined information included in the signal separated by the separating means, for example, pen attribute information such as the color of the ink of the coordinate input pen and the thickness of the pen tip, the attribute corresponding to the attribute is detected. It is possible to reproduce the written trajectory.

According to the eleventh aspect, in the tenth aspect,
In the coordinate reading device described in (1), technical means is used in which the predetermined information is the pen pressure information.

That is, the writing locus drawn on the coordinate input surface by the coordinate input pen can be reproduced with shading, for example, corresponding to the pen pressure.

According to the twelfth aspect, in the tenth aspect,
Alternatively, in the coordinate reading device according to claim 11, the predetermined information is color information, and the information detection unit detects the color information during a predetermined number of scans from the start of the scan. Use means.

That is, the writing locus corresponding to the color of the ink used by the coordinate input pen can be reproduced. Also,
Since the color information is detected during the predetermined number of scans from the start of the scan, after the color information is detected, the processing load on the CPU can be reduced because the color information is not detected. In addition,
The coordinate input sheet includes a sheet or plate having no flexibility, or a sheet or plate having flexibility.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a coordinate input pen and a coordinate reading device according to the present invention will be described below with reference to the drawings. In each of the embodiments described below, a so-called electronic blackboard, which electrically reads handwritten characters and figures drawn on a coordinate input sheet, will be described as an example of a coordinate input pen and a coordinate reading device according to the present invention. I do. Further, an example using frequency modulation which is a kind of angle modulation will be described. [Main Configuration] First, the main configuration of the electronic blackboard according to the first embodiment will be described with reference to FIGS. FIG. 1 is an explanatory perspective view showing an external appearance of a main structure of the electronic blackboard, and FIG. 2 is an explanatory diagram showing a state in which a personal computer (hereinafter abbreviated as PC) and a printer are connected to the electronic blackboard shown in FIG. is there.

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. A recess 1 having a semicircular cross section for accommodating the pen 60 is provided on the upper surface of the base 12.
2a is formed, and on the right side of the concave portion 12a, a flat portion 12b for placing the eraser 40 and the like is formed.

On the right side of the front of the frame 11, an operation unit 30
Is provided. The operation unit 30 includes a speaker 31 for reproducing sounds such as an operation sound and a warning sound, and a seven-segment page number storing data indicating the contents written on the writing surface 21a (hereinafter abbreviated as writing data). 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 sending one page each time the button is pressed, and one page each time the stored writing data is pressed. Delete button 35 for writing the stored writing data to the printer 200
Printer output button 36 pressed to output to (FIG. 2)
, A PC output button 37 pressed to output the stored writing data to the PC 100 (FIG. 2), a dead battery notification LED 39 for reporting that the battery of the pen 60 is dead, and the electronic blackboard 1 to start or stop. And a power button 38 to be pressed.

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 a 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 for controlling the volume of the speaker 31 is provided, and on the right side, connectors 13b and 13a are provided. As shown in FIG. 2, the plug 13 of the connection cable 201 connected to the printer 200 is connected to the connector 13b, and the PC 13 is connected to the connector 13a.
The plug 102 of the connection cable 101 connected to 00 is connected. That is, writing data indicating the contents written on the writing surface 21a of the electronic blackboard 1 is output to the PC 100,
The electronic blackboard 1 is monitored by the monitor 103 provided in the C100.
You can see the contents written in. 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.

Metal fittings 15, 15 for hanging the electronic blackboard 1 on a wall are provided at both ends at the upper end of the rear surface of the frame 11.
Is installed. In the first embodiment, the writing surface 2
The height H1 of 1a is 900 mm and the width W1 is 600 m
m. Further, the frame 11 and the base 12 are made of a synthetic resin such as polypropylene so as to be lightweight.
The total weight of the electronic blackboard 1 is 10 kg or less, so that it can be easily carried. Further, the eraser 40 includes a coil for generating an alternating magnetic field, an oscillation circuit, a battery, and the like.

[Network Configuration] Next, the electronic blackboard 1
FIG. 3 is a block diagram showing the configuration of a network in a case where data communication is performed between the network and another electronic whiteboard 1.
This will be described with reference to FIG. Here, a case where communication is performed between a plurality of rooms provided with the electronic whiteboard 1 in a company or between companies is described as an example. In the room 3 in the company 2, an electronic blackboard 1 and a P connected to the electronic blackboard 1
C100 and a LAN board 103 connected to the PC 100 are provided.
And the PC 100 connected to the electronic whiteboard 1 and the P
A modem 108 connected to C100 is provided. The LAN board 103 provided in each room 3 is LA
It is connected to the hub 105 by an N cable 104. The HUB 105 is connected to a server 106, and the server 106 can be connected to another company 5 via the Internet 300. The modem 108 provided in the room 4 can be connected to another company 5 from the telephone line 109 via the public switched telephone network 301. Although not shown, the other company 5 is provided with an electronic whiteboard 1 communicable via a PC, as in the company 2.

Here, the flow of data in the network will be described. Writing data stored on the electronic blackboard 1 provided in a certain room 3 is transmitted from the PC 100 to the LA.
The data is transmitted to PC 100 in room 3 designated via N board 103 and HUB 105. Then, the person who has received the data can use the monitor 103 provided in the PC 100.
The received data is displayed on the printer 20 (FIG. 2), or the received data is displayed on the printer 20 connected to the PC 100.
The content of the received data can be viewed by printing on the paper 203 with 0 (FIG. 2). In addition, the handwritten data is stored in, for example, TIFF (Tag Image File).
The file can be attached to the electronic mail as an image file in the format (Format) and transmitted from the server 106 to another company 5 via the Internet 300. This allows
The other company 5 can see the contents of the writing data by decoding the image file attached to the e-mail sent from the company 2.

[Structure of Writing Panel Body 20] Next, the structure of the writing panel body 20 will be described with reference to FIG. FIG. 4 is an explanatory diagram showing each component of the writing panel main body 20. The 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 sense coil 23 is laid, and a plate-shaped back panel 25 are sequentially stacked. It is. In this embodiment, the writing sheet 21 is composed of the bonded PE.
The panel 22 is formed to a thickness of 0.1 mm using a T (polyethylene terephthalate) film, and the panel 22 is formed to a thickness of 3.0 mm using an acrylic resin, ABS (acrylonitrile-butadiene-styrene copolymer), PC (polycarbonate), or the like. Is formed. Also, the mounting panel 24
Is made of a foamed resin material such as styrofoam and has a thickness of 3
The back panel 25 is formed of a conductive material such as aluminum and has a thickness of 1.0 mm. Further, the entire thickness of the frame 11 for holding each end of the writing panel main body 20 is 50 mm.

[Structure of Sense Coil 23] Next, the structure of the sense coil 23 will be described with reference to FIG. FIG. 5A is an explanatory view showing a configuration of the sense coil 23 shown in FIG. 4 with a part thereof being omitted, and FIG.
It is explanatory drawing which shows the width | variety and overlap pitch of the sense coil 23 shown to (A). In the following description, among the sense coils 23, the sense coils arranged in the X-axis direction are referred to as X coils, and the sense coils arranged in the Y-axis direction are referred to as Y coils. As shown in FIG. 5A, in the X-axis direction, the X and Y coordinates of the (X, Y) coordinates of the pen 60 and the eraser 40 are set.
There are m X coils X1 to Xm for detecting coordinates, and Y coils for detecting Y coordinates are arranged in the Y-axis direction.
N coils 1 to Yn are arranged orthogonally to the X coil. The X coil and the Y coil are each formed in a substantially rectangular shape, and the length of the long side of the rectangular portion is W, respectively.
3X, W3Y.

As shown in FIG. 5B, the X coils are each formed in a width (the length of the short side of the rectangular portion) W2, and the adjacent X coils are overlapped at a pitch of W2 / 2. Have been. Each Y coil is also formed to have a width W2, and adjacent Y coils are respectively overlapped at a pitch of W2 / 2. Also, each terminal 23a of the X coil
Are connected to an X coil switching circuit 50, and each terminal 23b of the Y coil is connected to a Y coil switching circuit 51 (FIG. 13). In the first embodiment, W2 = 5
0 mm, W3X = 680 mm, W3Y = 9
80 mm. Also, m = 23 and n = 35. Further, the X coil and the Y coil both have an insulating coating layer (for example, an enamel layer) on the surface and have a diameter of 0.3.
It is formed of a 5 mm copper wire. Note that FIG.
In the figure, the sides of each coil are drawn so as not to overlap in order to make the arrangement of the coils easy to understand. However, actually, for example, the long sides of the X coil X1 have the respective Y coils Y1, Y2,
The short sides of Y3 are arranged so as to overlap. Also,
The terminals 23a and 23b are configured such that their intervals are minimized.

[Principle for Determining Position Coordinates] Next, the writing surface 2
FIG. 6 shows the principle of obtaining the position coordinates of the pen 60 on the position 1a.
This will be described with reference to FIG. FIG. 6A shows X coils X1 to X3.
FIG. 6B 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, and FIG. ) Is FIG. 6 (A)
5 is a graph showing a voltage difference between mutually adjacent sense coils of X coils X1 to X3 shown in FIG.

In FIG. 6, the center lines of the X coils X1, X2 and X3 are C1, C2 and C3, respectively.
1, X2, and X3 are represented by ex1, ex, respectively.
2, ex3. As shown in FIG.
1 to ex3 are the center C1 to C3 of the sense coil, respectively.
, And has a monomodal property which becomes smaller as approaching the end in the longitudinal direction. Each coil has a P1 / 2 such that its own null point, that is, the point at which each of the voltages ex1 to ex3 becomes 0, is outside the center of the adjacent coil.
Layered. Further, as shown in FIG. 6C, the voltage difference between the mutually adjacent sense coils of the X coils X1 to X3 has a maximum value on the centers C1 to C3 of the sense coils, respectively. The graph becomes zero at the midpoint between the long sides of the sense coils, that is, the midpoint of the portion where the adjacent sense coils overlap, that is, the midpoint of the portion where the adjacent sense coils overlap.

For example, in FIG. 6C, (ex1-
ex2), the right half of the graph (the part shown by the solid line)
The distance from the center C1 of the X coil X1 to the midpoint Q2 of the portion where the X coil X2 is superimposed (1/2 of the superimposition pitch,
That is, the relationship between (W2 / 4) and (ex1-ex2) is shown. Now, if the pen 60 exists at the point Q2, (ex
If 1−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 W2 is 50 m
m, W2 / 4 = 12.5 mm.

[Coordinate Calculation Table] Next, the coordinate calculation table will be described with reference to FIG.
When writing is performed on the writing surface 21a (FIG. 1) using the pen 60, the pen 60 is normally in a state of having a certain angle, that is, a state of being inclined, with respect to a normal perpendicular to the writing surface 21a. In such a case, the alternating magnetic field radiated from the coil is not orthogonal to the sense coil 23 laid on the lower surface of the writing surface 21a. Is the pen point 6
2 does not match the actual position coordinates. Therefore, if the relationship between the tilt of the pen 60 and the actual position coordinates of the pen 60 is measured and obtained in advance, and the relationship is stored in the form of a table in the ROM 58, the tilt of the pen 60 is detected and the table is stored. By referring to the reference, the actual position coordinates of the pen 60 can be obtained.

Here, the position coordinates of the coil L1 and the coil L
The smaller the difference from the position coordinates of the two is, the closer the two coils are to the above-mentioned normal line, that is, the smaller the inclination is, and conversely, the larger the difference is, the larger the inclination is. Is stored in the ROM 58 as a coordinate calculation table 58a in which the position coordinates of both coils and the actual position coordinates of the pen 60 are associated with each other in place of the angle. Coordinate calculation table 58a
Is a coil L built in the pen 60 as shown in FIG.
1, the difference Xa (Ya) of the voltage value between the adjacent sense coils among the voltages induced in the sense coils by 1 is plotted on the horizontal axis.
Among the voltages induced in the sense coil by the coil L2, the difference Xb (Yb) in the voltage value between adjacent sense coils
Xa (Y
The intersection of a) and Xb (Yb) is the X or Y coordinate of pen 60 to be determined. The X coordinate and the Y coordinate are calculated using the same coordinate calculation table 58a shown in FIG.

[Structure of Pen] Next, the main structure of the pen 60 will be described with reference to FIGS. FIG.
FIG. 10A is an explanatory view showing the appearance of the pen 60, and FIG.
FIG. 10B is an explanatory diagram schematically showing the electrical configuration of the pen 60, and FIG. 10C is a circuit diagram showing the electrical configuration of the oscillation circuit 71 shown in FIG. 10B. FIG. 11 is FIG.
5 is a circuit section showing the electrical configuration of the oscillation circuit 72 shown in FIG.
FIG. 12 is an explanatory diagram showing the internal structure of the pen 60. In FIGS. 10A and 12, the direction of the pen tip 62 is the front end, and the direction of the lid 61 c is the rear end. FIG.
As shown in (A), the pen 60 has a case 61. The case 61 includes a cylindrical body 61a and a substantially conical tip 6 formed at the tip of the body 61a.
1b and a lid 61c detachably attached to the rear end of the body 61a.

As shown in FIG. 12, a rib 65a is formed on the inner wall 61d of the body portion 61a so as to protrude inward along a circumferential direction thereof. 65b is formed to project inward along the circumferential direction of the inner wall 61d. A coil L2 is fitted between the ribs 65a and 65b. On the rear end side of the rib 65b, a rib 66a is formed to protrude inward along the circumferential direction of the inner wall 61d, and on the rear end side away from the rib 66a, a rib 66b is formed in the circumferential direction of the inner wall 61d. Is formed to protrude inward along. Ribs 66a, 6
The coil L1 is fitted between 6b.

The ink cartridge 63 is inserted through the core L1a around which the coil L1 is wound and the core L2a around which the coil L2 is wound.
Are supported by ribs 65a, 65b, 66a, 66b. The pen tip 62 is inserted into the conical tip 63 b of the ink cartridge 63, and the ink 64 contained inside the ink cartridge 63 penetrates the pen tip 62. A ring-shaped protrusion 63 c is formed on the peripheral surface near the front end of the ink cartridge 63, and the protrusion 6 c is formed on the inner wall of the front end 61 b of the case 61.
A groove 61c having a shape corresponding to 3c is formed. That is, the ink cartridge 63 has the protrusion 63 c
By being fitted in c, it is fixed inside the case 61. When replacing the ink cartridge 63,
When the ink cartridge 63 is pulled in the direction indicated by the arrow F2, the protrusion 63c is separated from the groove 61c, and the ink cartridge 63 can be pulled out of the case 61.
Further, the new ink cartridge 63 is
a through the distal end portion 61 b of the case 61, and projecting portions 63
By fitting c into the groove 61c, the ink cartridge 63 can be loaded inside the case 61.

The coils L1, L
2 houses a circuit board 70 on which a circuit for generating an alternating magnetic field is mounted. A pen pressure sensor 68 is attached to a front end portion 70 a of the circuit board 70. A pen pressure sensor 68 and a rear end portion 63a of the ink cartridge 63
And a switch 67 is interposed therebetween. Switch 6
Reference numeral 7 includes a push button 67a and a contact portion 67b that opens and closes a contact when the push button 67a is pressed. The contact portion 67 has a built-in spring that is compressed by a push button 67a. When the pressing of the pen tip 62 is released, the pen tip 62 is moved by the arrow F due to the restoring force of the spring.
It moves in the direction shown by 2 and returns to the position before pressing. The switch 67 switches between ON and OFF each time the switch 67 is pressed.

At the rear end of the circuit board 70, a button battery 69 is accommodated.
Is electrically connected to the circuit board 70 via a spring 74 formed of a conductive material in a plate shape. The plus electrode of the button battery 69 is connected to the circuit board 70 via a spring 75 formed of a conductive material in a plate shape.
Is electrically connected to The lid 61c is a button battery 6
9 and the like can be attached to and detached from the body 61a to exchange them. Also, a cushion 71 formed of sponge is attached to the back surface 61e of the lid 61c.
The button battery 69 is held between the cushion 71 and the spring 74 by the expansion force of the cushion 71 and the restoring force of the spring 74.

When the pen tip 62 is pressed in the direction indicated by the arrow F1, the ink cartridge 63 moves to the rear end side, so that the push button 67a is pressed and the contact portion 67b is pressed.
Is closed, and the switch 67 is turned ON. Thus, the oscillating circuits 71 and 72 (FIG. 10B) mounted on the circuit board 70 operate, and the coils L1 and L2 simultaneously output the alternating magnetic field. In addition, the pen point 62 is the writing surface 1
2a (FIG. 1) and presses the pen tip 62, the pressing force is applied to the pen pressure sensor 68 via the contact portion 67b, and the resistance value of the resistor R6 (FIG. 11) of the pen pressure sensor 68 is reduced. Change. That is, the CR oscillation circuit 7 corresponds to the pen pressure.
Since the period of 2c changes, the period is set to the CPU on the receiving side.
The writing locus can be reproduced in accordance with the writing pressure by storing the writing pressure and the writing data calculated by the detected cycle and the writing data in association with each other.

In the first embodiment, a ferrite core is used for the core L1a of the coil L1, and the coil L2 is an air core. FIG. 23 is a graph showing the results of measurement of the outputs of the ferrite coil and the air-core coil by the inventor. As shown in FIG. 23, it can be seen that the output of the air-core coil is smaller than the ferrite coil by 10.0 mV or more at the maximum value. That is, by using an air-core coil with a small output as the coil L2 close to the pen tip 62 and a ferrite coil with a large output as the coil L1 far from the pen tip 62, the strength of the alternating magnetic field output by both coils L1 and L2 is reduced. It can be made equal near the pen tip 62. The total length W4 of the pen 60 (FIG. 10)
(A)) is 140 mm, and the outer diameter φ1 is 18 mm. Further, the distance from the tip of the pen tip 62 to the tip of the coil L1 is 5 cm, and the distance from the tip of the pen tip 62 to the tip of the coil L2 is 2 cm. In addition, a piezoelectric element is used for the pen pressure sensor 68, and the piezoelectric effect causes
A voltage corresponding to the pressing force (pen pressure) applied to the contact portion 67b is generated. Further, the button battery 69 is LR44,
The voltage is about 1.5V. Further, the body 61a, the tip 61b, and the lid 61c are each formed of a synthetic resin, and the pen tip 62 is formed of felt.

[Electrical Configuration of Pen 60] As shown in FIG. 10B, a circuit board 70 includes two oscillation circuits 71 and 7.
2 has been implemented. As shown in FIG. 10C, the oscillation circuit 71 includes a CR oscillation circuit 7 in which a different modulation frequency is set for each pen attribute such as the color of the ink and the thickness of the pen tip.
1c, an LC oscillation circuit 71a that oscillates a carrier wave that carries a signal oscillated from the CR oscillation circuit 71c, and an oscillation frequency of the LC oscillation circuit 71a.
FSK (Frequency S)
and an FSK circuit 71b for performing the modulation. The oscillation frequency of the carrier is determined by the inductance L1 of the coil L1 and the capacitances of the capacitors C1, C2, and C3, which constitute the LC oscillation circuit 71a.
The modulation frequency fm is determined by the capacitance of the capacitor C5 and the resistance values of the resistors R2 and R3 that constitute the CR oscillation circuit 71c. Further, the frequency deviation of the oscillation frequency of the carrier wave is determined by the capacitance of the capacitor C4 constituting the FSK circuit 71b.

The relationship between the attribute of the pen 60 and the modulation frequency fm is set as shown in FIG. 14A for explaining the relationship. In FIG. 14A, “thin” indicates that the pen tip 62 (FIG. 12) is thin, and “thick” indicates that the pen tip 62 is thick. For example, black pen indicates a pen 60 that has a thick pen tip and uses black ink. The eraser 40 also has a built-in coil, and calculates the erasure range of the eraser 40 based on the signal generated in the sense coil by the alternating magnetic field generated from the coil.
The modulation frequency fm is also assigned to the eraser 40, and the pen 60
Is identified.

As shown in FIG. 11, the oscillation circuit 72 includes a CR oscillation circuit 72c whose frequency changes according to the resistance value of the resistor R6 of the pen pressure sensor 68, and a CR oscillation circuit 7c.
L that oscillates a carrier that carries the signal oscillated from 2c
The oscillation frequency of the C oscillation circuit 72a and the oscillation frequency of the LC oscillation circuit 72a is determined by the modulation frequency of the CR oscillation circuit 72c.
(Frequency Shift Keying) and an FSK circuit 72b for performing modulation. The oscillation frequency of the carrier is determined by the coil L2 that constitutes the LC oscillation circuit 72a.
Inductance L2 and capacitors C6, C7, C
The modulation frequency fm is changed by the capacitance of the capacitor C10 constituting the CR oscillation circuit 72c and the resistance value of the resistor R6 of the pen pressure sensor 68. The frequency deviation of the carrier oscillation frequency is FSK
It is determined by the capacitance of the capacitor C9 constituting the circuit 72b.

Next, the operation of the oscillation circuits 71 and 72 will be described using the oscillation circuit 71 as an example. The pen tip 62 is the writing surface 21
a (FIG. 1) is pressed and the switch 67 is turned on, the power of the battery 69 is supplied to each circuit, and the output of the integrated circuit IC3 of the CR oscillation circuit 71c is output to the MOS F of the FSK circuit 71b.
Turn ON / OFF the gate of ET1, and set the LC oscillation circuit 71a
The carrier wave oscillated from is frequency-modulated by the signal oscillated from the CR oscillation circuit 71c. Note that the oscillation circuit 72
Is basically the same as that of the oscillation circuit 71, and the description is omitted. In the first embodiment, the LC oscillation circuit 71
The center frequency of the carrier wave a oscillates is 500 kHz, and the frequency deviation is ± 20 kHz. The integrated circuit IC1 is Toshiba TC7SLU04F, and the integrated circuits IC2 and IC3 are both Toshiba U04. MO
SFET1 is 2SK2158 made by NEC. The resistors R1 and R2 are each 1MΩ, and the resistor R3 is a 1MΩ variable resistor. The capacitors C1 to C5 are 1 μF, 2200 pF, 2200 pF, and 270, respectively.
F, 220F. Further, the center frequency of the carrier wave oscillated by the LC oscillation circuit 72a is 400 kHz, and the frequency deviation is ± 20 kHz. The integrated circuit IC4 is a TC7SLU04F made by Toshiba, and the integrated circuits IC5 and IC6 are both U04 made by Toshiba. MOS FE
T2 is 2SK2158 manufactured by NEC. The resistances of the resistors R4 and R5 are each 1 MΩ, and the variable range of the resistance R6 is 0Ω to 1MΩ. Capacitors C6 to C10 are respectively 2200 pF, 2200 pF, 2200 pF, 2
70F and 220F.

[Main Electrical Configuration and Control Contents of Electronic Blackboard 1] Next, main electrical configurations and control contents of the electronic blackboard 1 are shown in FIGS. 13, 14B, 14C and 19. This will be described with reference to FIG. FIG. 13 is an explanatory diagram showing the electrical configuration of the electronic blackboard 1 by blocks. FIG. 14B is a timing chart showing the relationship between the output timing of the coils L1 and L2 and the position detection timing of the pen 60, and FIG. 14C is a signal waveform at points A, B, and C in FIG. FIG. FIG. 19 is a flowchart showing main control contents executed by the CPU 56 shown in FIG.

The C provided in the control device 50 shown in FIG.
When the PU 56 detects that the power button 38 (FIG. 1) is turned on (step (hereinafter abbreviated as S) 100: Ye
s), initial settings such as loading the control program stored in the ROM 58, the coordinate calculation table 58a (FIG. 8), and the pen pressure calculation table 58d (FIG. 9) into the work area of the RAM 59 (S200). A coordinate reading / pen information detection process is executed (S300). [Coordinate Reading / Pen Information Detection Processing] Here, coordinate reading / pen information detection processing will be described with reference to FIGS. FIG. 7 is an explanatory diagram showing a state in which voltage values are stored in the voltage value storage area of the RAM 59, and FIG. 20 is a flowchart showing a flow of coordinate reading / pen information detection processing. The CPU 56 transmits a coil selection signal A (FIG. 14C) 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 50 via 53 (S3).
02). Subsequently, the coils L1 and L2 of the pen 60
The signal generated by the magnetic coupling between the alternating magnetic field simultaneously output by the X-ray generator and one of the X coils is supplied to the amplifier 52 (FIG. 1).
3), and the amplified signal B (FIG. 14)
(C)) is input to a detection circuit 80 that detects an alternating magnetic field output from the coil L1 and a detection circuit 90 that detects an alternating magnetic field output from the coil L2.

The band-pass filter (BPF) 81 forming the detection circuit 80 extracts the frequency band of the alternating magnetic field output from the coil L 1 from the band of the amplified signal B, and forms the band-pass filter forming the detection circuit 90. (BP
F) 91 extracts the frequency band of the alternating magnetic field output from the coil L2 from the band of the amplified signal B. The signals output from the band-pass filters 81 and 91 are subjected to amplitude detection by amplitude detection circuits 84 and 94, respectively, and the detected signals C (FIG. 14C) are respectively converted into A / D conversion circuits 85 and 94.
95 converts the signal into a digital signal corresponding to the amplitude, that is, the voltage value. Then these two digital signals are
CPU 56 via input / output circuit (I / O) 53
Is input to

Subsequently, the CPU 56 determines that the pen 60 has been detected (S304: Yes), and the voltage value e of the voltage generated in each X coil by the alternating magnetic field output from the coil L1.
As shown in FIG. 7, 1a to ema are sequentially stored in the voltage value storage area 59a of the RAM 59 in association with the coil number of the X coil (S306), and the voltage generated in each X coil by the alternating magnetic field output from the coil L2. Voltage value e1b ~
emb is associated with the coil number of the X coil and the RAM 59
Are sequentially stored in the voltage value storage area 59a (S30).
8). 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 according to the following procedure. Here, the voltage values e1a to e1
When calculating X coordinate Xn based on ma (S310)
Will be described as an example.

First, the maximum voltage value eam among the voltage values e1a to ema stored in the voltage value storage area 59a.
a, the coil number (hereinafter, referred to as max) of the X coil that generated the voltage value eamax is stored in the RAM 59.
To memorize. For example, as shown in FIG. 6, the pen 60 exists at the position Q3, and as shown in FIG. 6B, the voltage values e1a, e2a,
If e3a is generated, the maximum voltage value e2a is selected, and the coil number 2 of the X coil that generated the voltage value e2a is stored in the RAM 59 as max. And CP
U56 stores the larger of the voltage values eamax ± 1 on both sides of eamax in RAM 59 as eamax, and stores the coil number (hereinafter, referred to as max2) of the X coil that generated the stored voltage value in RAM 59.

In the example shown in FIG. 6, the larger of the voltage values e3a and e1a on both sides of e2a is determined, and the coil number 3 of the X coil generating the e3a is stored in the RAM 59 as max2. Subsequently, the CPU 56
By comparing the coil numbers max and max2 stored in M59, it is determined whether the coil number max2 exists in the + direction or the − direction of the X axis from the coil number max. Then, if max2 ≧ max, the variable SIDE is set to 1, and if max2 <max, the variable SIDE is set to −1. In the example shown in FIG. 6, since max = 2 and max2 = 3, max2>
max, and the variable SIDE is set to 1. Then C
PU56 is the voltage difference

Xa = eamax−eamax2 (1)

Is calculated. Then, the CPU 56 sets the voltage values e1b to em stored in the voltage value storage area 59a.
b, the difference between the voltage values

Xb = ebmax−ebmax2 (2)

Is calculated. Subsequently, the CPU 56 refers to the coordinate calculation table 58a (FIG. 8) and refers to the Xa calculated in S310 and the Xb calculated in S312.
Is read out (S314). For example, when Xa = 50 and Xb = 100, Xd = 7.
Next, the CPU 56 calculates the X coordinate of the pen tip Xn = (P1 / 2) × Xd + OFFSET × SIDE (3) (S312).

Subsequently, the CPU 56 determines whether or not the attribute detection flag indicating that the attribute of the pen 60 has been detected is set (S316). Since the attribute has not been detected yet, the process proceeds to S318 (S316). : No), FSK
The value of the demodulation circuit 83 is read (S318), the pen attribute is detected based on the count value of the read value (hereinafter, referred to as demodulation count number) (S320), and an attribute detection flag is set (S322). For example, as shown in FIG. 14A, when the demodulation count is 245, the pen attribute is black.

The CPU 56 has an FSK demodulation circuit 93
Is read (S324), and the pen pressure calculation table 58d is read.
Referring to (FIG. 9), the pen pressure corresponding to the demodulation count number is detected (S326). Subsequently, the CPU 56 executes scanning of each Y coil (S328), and associates the voltage value of the voltage generated in each Y coil by the alternating magnetic field output from the coil L1 with the coil number of the Y coil and stores the voltage value for the Y coil in the RAM 59. Are sequentially stored in the voltage value storage area (S330),
The voltage value of the voltage generated in each Y coil by the alternating magnetic field output by the coil L2 is sequentially stored in the voltage value storage area for the Y coil in association with the coil number of the Y coil (S3).
32). Subsequently, the CPU 56 determines in S310 and S312
Calculate Ya and Yb in the same procedure as when Xa and Xb are calculated in (S334, S336),
The Y coordinate Yd corresponding to Ya and Yb is read with reference to the coordinate calculation table 58a (FIG. 8). Subsequently, the CPU 56
Calculates the Y coordinate Yn in the same procedure as when the X coordinate Xn is calculated (S338).

Subsequently, the CPU 56 determines the pen attribute detected in S320, the pen pressure detected in S326,
The X coordinate Xn calculated in S314 and the Y coordinate Yn calculated in S338 are stored in the RAM 58 in association with each other (S340). Here, the position coordinate specified by the X coordinate Xn and the Y coordinate Yn is defined as P1. Afterwards CP
U56 repeatedly executes S302 to S340, calculates the position coordinates P2, P3, P4... And stores them in the RAM 58. Writing data stored in such a form
For example, it is output to the printer 200 (FIG. 2),
In addition, printing is performed with shading corresponding to the pen pressure. Also, P
Is output to C100 and is displayed in black on the monitor 103 (FIG. 2).
In addition, it is displayed with shading corresponding to the pen pressure. That is,
The writing data can be reproduced according to the attributes and pen pressure of the pen 60.

While the pen is detected (S30)
4: Yes), after detecting the pen attribute once (S32)
2) Pen attributes are not detected twice. When the pen 60 is separated from the writing surface 21a (FIG. 1) (S304: N
o), the attribute detection flag is reset (S342), and the pen attribute is detected (S316: No, S318 to S32).
2). That is, even if the pen 60 is replaced with one having a different attribute during writing, the attribute detection flag is reset (S342), so that a new attribute of the pen 60 can be detected immediately. Further, for example, when writing a character, the pen attribute can be detected only at the first scan of the stroke for each stroke, so that the pen attribute is detected more than when the pen attribute is detected every time the X coil is scanned.
The processing load on the PU 56 can be reduced.

[Determination of Pen Attribute] Next, the CPU 56
The electrical configuration and control for detecting the pen attribute at 320 will be described with reference to FIGS. 15 to 18, 21 and 22. FIG. 15 shows the FSK demodulation circuit 83
FIG. 16 is an explanatory diagram showing the electrical configuration of FIG. 13 and FIG. 16 is an explanatory diagram showing signal waveforms appearing at various parts of the FSK demodulation circuit 83 shown in FIG. FIG. 17A shows an output signal of the CR oscillation circuit 71c (hereinafter, referred to as a CR signal) and an LC signal.
An output signal of the oscillation circuit 71a (hereinafter, referred to as a carrier signal), an output signal of the limiter circuit 82 (hereinafter, referred to as a limiter output signal), and a count circuit 83a (FIG. 15)
FIG. 7 is an explanatory diagram showing a relationship with a count value according to the embodiment. FIG.
(B) is an explanatory diagram showing how the count value stored in the shift register 83b (FIG. 15) shifts.

FIG. 18A shows an absolute value comparator 83f.
FIG. 18 is an explanatory diagram showing the relationship between the threshold value determination output by FIG. 15 and the determination cycle of the CPU 56, and FIG. 18B is an explanatory diagram showing how the count value of the counter 83g moves. FIG. 21 is a flowchart showing the flow of processing (pen attribute detection processing 1) from the count circuit 83a to the absolute value comparator 83f constituting the FSK demodulation circuit 83, and FIG. 22 is a counter 83g and an adder 83i.
3 is a flowchart showing the flow of the process (pen attribute detection process 2). The carrier signal shown in FIG. 17A has, for example, a center frequency of 500 kHz as described above.
The frequency shift is ± 20 kHz, but the frequency shift is exaggerated in FIG. 17A for easy understanding.

First, FSK for detecting pen attributes
The features of the demodulation circuit 83 will be described with reference to FIG. In the example shown in FIG. 17A, the carrier signal has a high frequency (for example, 520 k) during the low level of the CR signal.
Hz), and is modulated to a low frequency (for example, 480 kHz) during a high level. Therefore, assuming that the period of the limiter output signal while the CR signal is at a low level is TB, the period of the limiter output signal while the CR signal is at a high level is TC longer than TB. Therefore, the count value k for one cycle of the limiter output signal by the count circuit 83a 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 83a 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, the cycle of the CR signal can be obtained. Can be obtained, so that the pen attribute can be detected. Where FSK
An outline of the operation of each component of the demodulation circuit 83 will be described.
The count circuit 83a measures the count value k, and outputs a shift register 83b, a first weighted average circuit 83c, a second weighted average circuit 83d, a subtractor 83e, and an absolute value comparator 8
3f detects the change timing of the count value k, and the counter 83g, the register 83h, and the adder 83i measure the cycle in which the count value k changes. And the CPU 56
Counts the added value output from the adder 83i,
The pen attribute is detected based on the demodulated count number (S
320).

Next, the operation of the FSK demodulation circuit 83 will be described in detail. The signal output from the band pass filter 81 is converted by the limiter circuit 82 into a square wave limiter output signal shown in FIG. 16 and output to the FSK demodulation circuit 83. Then, when the FSK demodulation circuit 83 detects the rise of the limiter output signal (S10 in FIG. 21: Ye
s), counting of the cycle of the limiter output signal is started using the system clock (CLK) (S12), and when the next rising of the limiter output signal is detected (S14: Ye)
s), the count value k is output to the shift register 83b (S16), and the count value k is reset (S18).
That is, the count circuit 83a measures the length TB or TC of one cycle of the limiter output signal.

In this embodiment, the shift register 83b
Is the limiter output signal 1 as shown in FIG.
The count value k for the cycle is stored for eight cycles of k1 to k8,
Every time the newest count value k is fetched, the oldest count value k is discarded, and each count value k is shifted by one. The first weighted averaging circuit 83c includes a shift register 8
A weighted average value from the newest count value stored in 3b to the third newest count value is calculated, and the weighted average value (hereinafter, referred to as a first weighted average value) is subtracted by the subtractor 8
Output to 3e. The second weighted average circuit 83d calculates a weighted average value from the oldest count value stored in the shift register 83b to the third oldest count value, and calculates the weighted average value (hereinafter, referred to as the second weighted average value). Is called)
Is output to the subtractor 83e.

As described above, the weighted averaging circuit performs the weighted averaging on the count values counted in time, so that even if a certain count value is affected by noise, the influence can be reduced. The subtractor 83e 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 83f (S20 in FIG. 21). For example, in FIG. 17A, a first weighted average circuit 83c calculates a weighted average value of count values k1 to k3, and a second weighted average circuit 83d calculates count values k6 to k3.
8 are calculated, the count values k6 to k8
Among them, 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, if it is detected that the second weighted average value is 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 attribute information of the pen 60 can be detected. The first weighted averaging circuit 55c and the second weighted averaging circuit 55d respectively provide a carrier frequency (the oscillation frequency of the LC oscillation circuits 71a and 72a) and a modulation frequency,
The decision is based on the complexity of the circuit. Further, the count value 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 wave. I do.

Next, the processing from the absolute value comparator 83f to the adder 83i will be described with reference to FIG. In FIG. 18, 〜 indicates the count value of the counter 83g. The absolute value comparator 83f calculates the difference Δm
Is compared with a preset threshold value m1, and the difference Δ
It is determined whether or not m is equal to or greater than the threshold value m1 (S22 in FIG. 21). If it is determined that the difference Δm is equal to or greater than the threshold value m1 (S22: Yes), the threshold determination output is changed from the low level. The level is changed 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.
Assuming that the count value of the shorter cycle TB of the limiter signal is 10 by the count circuit 83a, the count value of the cycle TC is 16 and the threshold value m1 is 2 as shown in FIG.
Since each of k6 is 10, the first weighted average value = (k
1 + k2 + k3) / 3 = 10. Since the count values k7 and k8 are both 16, the second weighted average value = (k6 + k7 + k8) / 3 = 42/3 = 14,
The difference Δm = 10−14 = −4.

Therefore, (absolute value of difference Δm = 4)>
Since (threshold value m1 = 2), the threshold value determination output changes from low level to high level (S24). This high level state is maintained until the absolute value comparator 83f determines that the absolute value of the difference Δm is equal to or larger than the threshold value m1. When the calculation range of the first weighted average circuit 83c and the second weighted average circuit 83d reaches a portion that has passed through the edge of the CR signal, the period of the limiter output signal becomes constant. Since the weighted average value of the cycle count value is calculated, the subtractor 55e
Becomes 0, and the threshold value judgment output remains in the high level state.

On the other hand, when the counter 83g detects that the threshold value judgment output has changed from the low level to the high level (S30 in FIG. 22: Yes), the time during which the judgment output is at the high level, that is, the judgment output Is counted using the system clock (CLK) (S3).
2). The count value is defined as (B in FIG. 18B).
1)). Then, the absolute value comparator 55f again determines the difference Δ
If it is determined that m is equal to or larger than the threshold value m1 (S in FIG. 22)
22: Yes), the threshold determination output is changed from the high level to the low level (S24). That is, it is determined that the period of the limiter output signal has changed (the falling edge of the CR signal has been detected). Thereby, the counter 83g
Detects that the threshold determination output has changed from the high level to the low level (S34: Yes), and FIG. 18 (B)
As shown in (B2) of FIG.
h (S36). Subsequently, the counter 83g resets the count value (S38), and counts the time during which the threshold determination output is at the low level, that is, the half cycle of the threshold determination output (S32). The count value is used.

Subsequently, the adder 83i determines that the timing at which the count value is held in both the counter 83g and the register 83h, that is, the addition timing (S
50: Yes), the count value held by the counter 83g and the count value held by the register 83h are added (S52), and the added value is output to the CPU 56 (S54). At this time, the counter 83 g
The count value is output to the register 83h as shown in (B3) of (B) (S36 in FIG. 22). And CPU
56 reads the added value, that is, the demodulated count number (S318 in FIG. 20), and determines the pen attribute based on the read demodulated count number (S320).

Subsequently, the adder 83i adds the count value of the register 83h and the count value of the counter 83g and outputs the result to the CPU 56 ((B) in FIG. 18B).
3)). Thereafter, each time the threshold determination output changes, the count value of the counter 83g is output to the register 83h, and the adder 83i adds the count value of the counter 83g and the count value held in the register 83h, and The cycle of outputting the added value to the CPU 56 is repeated. That is, as shown in FIG. 18B, the adder 83i adds the latest count value counted by the counter 83g and the immediately preceding count value held in the register 83h, and adds the result to the CPU 56. As shown in FIG.
Determines the pen attribute based on the latest count value and the added value of the immediately preceding count value every half cycle of the threshold value determination output.

Accordingly, even if the scan of the sense coil 23 is performed during the threshold value judgment output, for example, between the times t0 and t1 in FIG. Even if the added value of one cycle (t2 to t4) is not taken in, the time t2 to t4 half a cycle after the time t1
Since it is sufficient to take in the added value of one cycle of the above, the pen attribute can be determined at a high speed. The FSK demodulation circuit 9
3 has the same configuration as the above-described FSK demodulation circuit 83 (FIG. 15), and is not shown. However, the CPU 56 reads the demodulation count output from the FSK demodulation circuit 83 (S324 in FIG. 20), The pen pressure corresponding to the read demodulation count is detected with reference to the calculation table 58d (FIG. 9) (S326).

Returning to the description of FIG. 19, the CPU
56 is a page return button 33, a page forward button 34
When the erase button 35 (FIG. 1) is pressed, page processing such as returning, sending, or erasing the stored writing data in page units is performed (S400). Further, the CPU 56 outputs a switching signal generated by operating various buttons (FIG. 1) provided on the operation unit 30 to an I / O.
Page processing such as sending or returning a page in which the position coordinate data stored in the RAM 59 is stored via the F circuit 54 (FIG. 13) in page units, or erasing the position coordinate data in page units. Execute (S400). Also, the CPU 56 converts the position coordinate data of the target page from the position coordinate data stored in the RAM 59 into an appropriate format, and
And a data output process for outputting to the printer 200 (FIG. 2) (S500).

Further, the CPU 56 operates the audio circuit 31a (FIG. 13) based on a switching signal generated when various buttons are pressed, and generates an operation sound such as "P" or "P" from the speaker 31. A voice output process is performed (S600). Further, the CPU 56 includes the eraser 4
0 due to the alternating magnetic field generated from the coil built in
An erasing trajectory of the eraser 40 is calculated based on the voltage generated in the coil and the Y coil, and an eraser process for erasing the position coordinate data in the calculated wiping trajectory from the RAM 59 (FIG. 13) is executed (S700).

As described above, if the pen 60 and the electronic blackboard 1 of the first embodiment are used, the coils L1 and L2 of the pen 60 simultaneously output alternating magnetic fields having different frequencies. Sense coil 2
3 can be detected at the same timing, so that the induction signal generated from the two coils is alternately switched and detected as compared with the conventional signal (FIG. 24).
The position coordinates of the pen 60 can be calculated quickly. Therefore, since the position coordinates of the pen 60 can be calculated faster, the number of data of the obtained position coordinates can be increased.
The reading resolution of the position coordinates of the pen 60 can be increased. Comparing the timing chart of the present invention shown in FIG. 14 (B) with the conventional timing chart shown in FIG. 24 (B), the conventional one outputs the alternating magnetic field from the coils L1 and L2 alternately. The position coordinates P1, P2... Cannot be detected unless both L2 are output, but in the case of the present invention, the coils L1 and L2
Output the alternating magnetic field at the same time, so that there is no need to wait for the output of one coil, so that many position coordinates P1, P2
. Can be obtained at high speed.

Further, since the period or duty ratio of the CR signal is single and the period or duty ratio differs depending on the attribute information of the pen 60, the CPU 56 only detects the length of one period of the CR signal, 60 attribute information can be detected. Furthermore, attribute information can be recognized only by slightly different periods or duty ratios of CR signals. For example, the attribute information can be recognized only by a difference in the cycle or duty ratio by at least one cycle of the system clock. Therefore, a very large number of types of attribute information can be transmitted, and the attribute information can be recognized in a short time. In addition,
When the duty ratio of the CR signal is 50%, FSK
Even when the demodulation circuit 83 detects a half cycle of the CR signal, the attribute information of the pen 60 can be detected.

Further, the coils L1 and L2 of the pen 60
The attribute information is transmitted by FSK modulating the alternating magnetic field output by the CR signal, and the FSK demodulation of the induction signal generated in the conductor laid on the coordinate input sheet is performed, so that a single cycle or a single CR signal is generated. To detect the attribute information based on the detected cycle or duty ratio. Therefore, even if the strength of the alternating magnetic field changes, the cycle or phase, which is the portion indicating the attribute information, Is not affected, so that attribute information can be transmitted and received accurately. The duty ratio of the CR oscillation circuit 71c or 72c may be changed according to the pen pressure, and the duty ratio may be detected by the FSK demodulation circuit 83 or 93. In this case, the writing pressure calculation table 58d (FIG. 9) has a configuration in which the duty ratio and the writing pressure are associated with each other.

Incidentally, the writing surface 12a corresponds to the coordinate input surface of the present invention, the sense coil 23 corresponds to the conducting wire, the mounting panel 24 corresponds to the coordinate input sheet, and the writing pressure sensor 6
Reference numeral 8 corresponds to the pen pressure detecting means. Also, the oscillation circuits 71 and 7
2, the switch 67 and the battery 69 correspond to the information carrying means of the present invention, the control device 50 corresponds to the reading means, the band pass filters 81 and 91 correspond to the separating means, the limiters 82 and 92 and the FSK demodulation circuit. 83 and 93 correspond to information detecting means. Then, S executed by the CPU 56
302 to S314 and S328 to S340 function as reading means of the present invention, and S316 to S322, S324 to S326, and S342 function as information detecting means.

[Brief description of the drawings]

FIG. 1 is an external perspective explanatory view showing a main configuration of an electronic blackboard according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a state where a PC and a printer are connected to the electronic whiteboard shown in FIG. 1;

FIG. 3 is an explanatory diagram showing a block diagram of a network configuration when data communication is performed between the electronic whiteboard 1 and another electronic whiteboard 1;

FIG. 4 is an explanatory view showing each component of the writing panel main body 20;

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

6 (A) is an explanatory view showing a part of X coils X1 to X3, and FIG. 6 (B) is a diagram showing voltages and width directions generated in X coils X1 to X3 shown in FIG. 6 (A). 6 (C) is a graph showing a voltage difference between mutually adjacent sense coils of the X coils X1 to X3 shown in FIG. 6 (A).

FIG. 7 is an explanatory diagram showing a state where a voltage value is stored in a voltage value storage area of a RAM 59;

FIG. 8 is an explanatory diagram of a coordinate calculation table.

FIG. 9 is an explanatory diagram of a pen pressure calculation table.

10A is an explanatory diagram showing an appearance of a pen 60, FIG. 10B is an explanatory diagram showing an outline of an electric configuration of the pen 60, and FIG. FIG. 4 is a circuit diagram showing an electrical configuration of an oscillation circuit shown in FIG.

11 is a circuit portion illustrating an electrical configuration of the oscillation circuit 72 illustrated in FIG.

FIG. 12 is an explanatory diagram showing an internal structure of a pen 60.

FIG. 13 is an explanatory diagram showing an electric configuration of the electronic blackboard 1 by blocks.

14A is an explanatory diagram showing a relationship between an attribute of a pen 60 and a modulation frequency fm, and FIG. 14B is a diagram showing a relationship between output timings of coils L1 and L2 and position detection timing of pen 60; FIG. 14C is an explanatory diagram showing signal waveforms at points A, B, and C in FIG.

FIG. 15 is an explanatory diagram showing an electrical configuration of an FSK demodulation circuit 83 (FIG. 13).

FIG. 16 is an explanatory diagram showing signal waveforms appearing at various parts of the FSK demodulation circuit 83.

FIG. 17A shows a CR signal, a carrier signal, a limiter output signal, and a count circuit 55a (FIG. 1).
FIG. 17B is an explanatory diagram showing the relationship with the count value according to 5), and FIG. 17B is an explanatory diagram showing how the count value stored in the shift register 83b (FIG. 15) shifts.

FIG. 18A shows an absolute value comparator 83f.
FIG. 18 is an explanatory diagram showing the relationship between the threshold value determination output by FIG. 15 and the determination cycle of the CPU 56, and FIG. 18B is an explanatory diagram showing how the count value of the counter 83g moves.

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

20 is a flowchart showing a flow of coordinate reading / pen information detection processing executed by the CPU 56 in S300 of FIG.

FIG. 21 is a flowchart showing a flow of processing (pen attribute detection processing 1) from a count circuit 83a constituting the FSK demodulation circuit 83 to an absolute value comparator 83f.

FIG. 22 is a flowchart showing the flow of processing of a counter 83g and an adder 83i.

FIG. 23 is a graph showing the results of measurement of the outputs of the ferrite coil and the air-core coil by the inventor.

FIG. 24A is an explanatory diagram showing the configuration of a conventional coordinate input pen and a conventional coordinate reading device by blocks, and FIG.
FIG. 4B is a timing chart showing the relationship between the data output timing of the coordinate detection circuit 308 and the output timing of the coordinate correction circuit 310 shown in FIG.

[Explanation of symbols]

 Reference Signs List 1 electronic blackboard (coordinate reading device) 21a writing surface (coordinate input surface) 23 sense coil (conductor) 24 mounting panel (coordinate input sheet) 30 operation unit 56 CPU 58a coordinate calculation table 60 pen (coordinate input pen) 67 switch 68 brush Pressure sensor (writing pressure detecting means) 71, 72 Oscillation circuit 83, 93 FSK demodulation circuit L1, L2 Coil

Claims (12)

[Claims] 1. A coordinate input sheet having a plurality of conductors laid below a coordinate input surface; and a coordinate input pen having a plurality of coils for outputting an alternating magnetic field magnetically coupled to the conductors, wherein the plurality of conductors are provided. A coordinate reading device that detects an induction signal generated in the conductive wire by an alternating magnetic field output from the plurality of coils, and reads a position coordinate of the coordinate input pen based on the detected induction signal. 2. The coordinate input pen according to claim 1, wherein the plurality of coils simultaneously output alternating magnetic fields having different frequencies. 2. The coordinate input pen according to claim 1, wherein, among the plurality of coils, the output is set to be larger as the coil is farther from the pen tip. 3. The coordinate input pen according to claim 1, wherein at least the coil closest to the pen tip is an air-core coil. 4. A switch that is operated by pressing the pen tip is provided, and the plurality of coils are configured to output respective alternating magnetic fields simultaneously in conjunction with the switch. The coordinate input pen according to any one of claims 1 to 3, wherein 5. A coordinate input device according to claim 1, further comprising an information carrying means for carrying predetermined information by using an alternating magnetic field output from said coil. pen. 6. A writing pressure detecting means for detecting writing pressure applied to the pen tip, wherein the predetermined information is writing pressure information indicating the writing pressure detected by the writing pressure detecting means. The coordinate input pen according to claim 5, wherein: 7. A coordinate input pen according to claim 1, a coordinate input sheet on which a plurality of conductors are laid below a coordinate input surface, and scanning of the plurality of conductors. Reading means for detecting an induction signal generated in the conductive wire by an alternating magnetic field simultaneously output from the plurality of coils, and reading a position coordinate of the coordinate input pen based on the detected induction signal. A coordinate reading device comprising: 8. The method according to claim 1, wherein the coordinate input pen uses a signal having a single cycle or a single duty ratio set for each piece of attribute information of the coordinate input pen. Angle-modulating the alternating magnetic field generated from the, the reading means, by demodulating the induction signal,
Detecting the single cycle or single duty ratio of the alternating magnetic field generated from the coordinate input pen, and detecting attribute information of the coordinate input pen based on the detected cycle or duty ratio. The coordinate reading device according to claim 7, wherein 9. A separation means for separating an induction signal detected from the conductor into a signal corresponding to a frequency of each of the alternating magnetic fields by an alternating magnetic field output from the plurality of coils. The coordinate reading device according to claim 7 or 8. 10. The coordinate reading device according to claim 9, further comprising information detecting means for detecting the predetermined information included in the signal separated by the separating means. 11. The coordinate reading device according to claim 10, wherein the predetermined information is the pen pressure information. 12. The information processing apparatus according to claim 10, wherein the predetermined information is color information, and the information detection unit detects the color information during a predetermined number of scans from the start of the scan. Item 12. The coordinate reading device according to item 11.