JP2002108552A - Coordinate inputting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the detecting precision of the position of a writing instrument such as a pen or an eraser in a coordinate reading board by identifying the attribute of the wiring instrument, and generating alternating magnetic fields in which any AM component is not included for position coordinate reading. SOLUTION: In this coordinate inputting device equipped with a coordinate reading board on which a plurality of sense coils are arranged in XY directions for reading coordinates when the sense coils are magnetically connected to alternating magnetic fields and a wiring instrument equipped with an oscillation coil to be butted to the coordinate reading board for generating the alternating magnetic fields with prescribed frequencies, the writing instrument is constituted of a CR oscillation circuit 69b, an LC oscillation circuit 69a, and a power-on detecting circuit 69c, and the power on detecting circuit 69c is constituted so that the oscillation by the CR oscillation circuit 69b can be validated only in a prescribed period just after the power-on is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coordinate input apparatus, and more particularly, to a coordinate reading board for laying a plurality of sense coils in XY directions and for reading the coordinates by magnetically coupling the sense coils with an alternating magnetic field. The present invention relates to a coordinate input device provided with a writing instrument (pen, eraser, etc.) for generating an alternating magnetic field by pressing against the coordinate reading board.

[0002]

2. Description of the Related Art Conventionally, an electromagnetic induction type coordinate input device used for an electronic blackboard or the like includes, for example, a pen as a position indicator, and a specific transmission frequency for indicating the position in the pen. Some have a built-in electromagnetic coil that generates an alternating magnetic field. On the other hand, there is a type in which an alternating magnetic field is generated from the receiving side, and a position indicator is provided with a sense coil having no power supply to indicate the position. However, by providing an electromagnetic coil that generates an alternating magnetic field with a power supply on the pen side, a strong signal is output, and an electronic blackboard that is resistant to noise and has high reading accuracy can be obtained. Further, in such an electronic blackboard, attributes such as the color and thickness of the pen can be transmitted to the receiving side by modulating the frequency of the generated alternating magnetic field at a specific frequency.

As an oscillation circuit 600 for generating this alternating magnetic field, for example, a circuit shown in FIG. 24 is used. The oscillation circuit 600 mainly includes an LC oscillation circuit 69
0c, the FSK circuit 690d, and the CR oscillation circuit 690e.
It is composed of Here, the CR oscillation circuit 690
“e” is a circuit that generates a different modulation frequency for each attribute in order to distinguish the color and thickness of the pen. Also,
The LC oscillation circuit 690c is a circuit for oscillating a carrier wave S100 (see FIGS. 26 and 27) that carries the signal oscillated from the CR oscillation circuit 690e. Also, FSK
The circuit 690d uses the modulation frequency of the CR oscillation circuit 690e to change the oscillation frequency of the LC oscillation circuit 690c to FSK (FSK
This is a circuit for performing REQ (Shift Keying) modulation.

More specifically, the oscillation circuit 600 controls the N-MOS field effect transistor FET10 of the FSK circuit 690d while the low signal is output from the CR oscillation circuit 690e.
Since 0 is turned off, the circuit shown in FIG.
Frequency fc100 (= 1 / [2π ｛L1 · C1 · C2 /
(C1 + C2)｝ ^1/2 ]). On the other hand, CR
While the oscillator circuit 690e outputs a high signal, FS
As shown in FIG. 25 (b), the K circuit 690d
The capacitor C300 of the circuit 690d is connected to the capacitor C20.
0 and a circuit connected in parallel with the frequency fc200 (=
1 / [2π ｛L1 · C1 · (C2 + C3) / (C1 + C
2 + C3)｝ ^1/2 ]). By modulating the frequency of the carrier in this manner, the frequency of the alternating magnetic field is modulated, and attributes such as the color and thickness of the pen are transmitted to the receiving side.

[0005]

However, FIG.
, The carrier wave S output from the oscillation circuit 600
There is a problem that the amplitude of 100 differs between the case where the field effect transistor FET100 of the FSK circuit 690d is on and the case where it is off. Amplitude VH10 when field effect transistor FET100 is on
0 and the amplitude VL100 when it is off are VH1
Since 00 is larger than VL100, the amplitude of the carrier S100 changes for each transmission cycle T100 of the CR oscillation circuit 690e, and an AM component is generated.
If the carrier wave S100 contains an AM component as shown in FIG. 27, the reading accuracy on the receiving side may be reduced, and the pen detection position on the electronic blackboard may be erroneously detected.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and it is possible to generate an alternating magnetic field containing no AM component for reading position coordinates while identifying attributes of a writing instrument such as a pen or an eraser. It is an object of the present invention to improve the accuracy of detecting the position of the writing implement on the coordinate reading board.

[0007]

According to a first aspect of the present invention, there is provided a coordinate input device, wherein a plurality of sense coils are laid in XY directions, and the sense coils are magnetically coupled to an alternating magnetic field. A coordinate input device including a coordinate reading board that reads coordinates by a writing implement having an oscillation coil that generates an alternating magnetic field having a predetermined frequency by being pressed against the coordinate reading board.
The writing implement is configured to transmit a writing implement identification signal indicating the attribute of the writing implement for a predetermined period after being pressed against the coordinate reading board, and thereafter to transmit a signal without the writing implement identification signal. And

According to the coordinate input device of the present invention, a writing implement identification signal indicating an attribute of the writing implement is transmitted for a predetermined period after the writing implement is pressed against the coordinate reading board, and thereafter there is no writing implement identification signal. Send a signal.
The coordinate reading board identifies the attribute of the writing implement while transmitting the writing implement identification signal. During this time, an AM component exists in the signal transmitted from the writing instrument. But,
After that, after the signal without the writing implement identification signal is transmitted, the position coordinates of the writing implement can be accurately read based on the signal without the AM component.

According to a second aspect of the present invention, there is provided the coordinate input device according to the first aspect, wherein the writing implement has an FSK modulation indicating an attribute of the writing implement for a predetermined period immediately after being pressed against the coordinate reading board. A signal is transmitted, and then a signal without FSK modulation is transmitted.

According to the coordinate input device of the present invention, the writing implement sends out the FSK modulation signal indicating the attribute of the writing implement for a predetermined period immediately after pressing the writing implement on the coordinate reading board, and thereafter there is no FSK modulation. Send a signal. Therefore, the attribute of the writing instrument is identified based on the FSK modulation signal transmitted only for a short period immediately after the writing instrument is pressed against the coordinate reading board, and thereafter, the influence of the AM component is determined based on the signal without FSK modulation. It becomes possible to accurately read the position coordinates of the writing instrument without receiving it.

According to a third aspect of the present invention, in the coordinate input device according to the first aspect, the writing instrument includes a rectangular wave generating circuit, a sine wave generating circuit, and a power on / off circuit. The power supply on / off detection circuit is characterized in that oscillation by the rectangular wave generation circuit is enabled only for a predetermined period after power-on is detected.

According to the coordinate input device of the third aspect, the writing instrument is pressed against the coordinate reading board to enable oscillation by the rectangular wave generating circuit for a predetermined period after power-on is detected, and thereafter the rectangular wave is generated. Disable oscillation by the generator. As a result, the attribute of the writing implement is identified while the oscillation by the square wave generation circuit is enabled immediately after the writing implement is pressed against the coordinate reading board, and after the oscillation by the square wave generation circuit is disabled, the AM Based on the sine wave having no component, the position coordinates of the writing instrument can be accurately read.

According to a fourth aspect of the present invention, there is provided the coordinate input device according to the first aspect, wherein the writing instrument comprises a CR oscillation circuit, an LC oscillation circuit, and a power-on detection circuit. The detection circuit is configured to enable oscillation by the CR oscillation circuit only for a predetermined period immediately after detecting power-on.

According to the coordinate input device of the fourth aspect, the oscillation by the CR oscillation circuit is enabled only for a predetermined period immediately after the power-on detection circuit detects the power-on, so that the signal based on the modulated signal can be obtained. To identify the attribute of the writing instrument, then disable the oscillation by the CR oscillation circuit,
Since only oscillation by the oscillation circuit is effective, AM
Based on the signal having no component, the position coordinates of the writing instrument can be accurately read.

According to a fifth aspect of the present invention, in the coordinate input device according to the first aspect, the writing instrument includes an LC oscillation circuit and a CPU, and the CPU operates for a predetermined period immediately after power-on. It is characterized in that modulation frequency control is performed such that only FSK-modulated signals are transmitted.

According to the coordinate input device of the fifth aspect, C
The PU performs modulation frequency control so as to transmit a signal subjected to FSK modulation only for a predetermined period immediately after power-on, and thereafter, sets a state in which only the oscillation signal from the LC oscillation circuit not subjected to FSK modulation is transmitted. . As a result, the attributes of the writing implement can be identified based on the FSK-modulated signal immediately after power-on, and thereafter, the position coordinates of the writing implement can be accurately identified based on the signal without FSK modulation. Become.

According to a sixth aspect of the present invention, in the coordinate input device, a plurality of sense coils are laid in the X and Y directions, and the sense coils are magnetically coupled to an alternating magnetic field to read coordinates. A coordinate input device including a writing implement having a coil that generates an alternating magnetic field of a predetermined frequency by pressing the coordinate input apparatus,
The coordinate reading board demodulates FSK for a predetermined period after being pressed by the writing instrument.

According to the coordinate input device of the present invention, the FSK demodulation by the coordinate reading board is performed only for a predetermined period after being pressed by the writing instrument.
There is an effect that the processing load is reduced.

According to a seventh aspect of the present invention, in the coordinate input device according to the sixth aspect, the predetermined period is at least 1.5 cycles of an FSK modulation frequency at which attribute determination of the writing instrument can be performed. It is characterized by having such a configuration.

According to the coordinate input device of the present invention, the attribute of the writing implement can be reliably determined by using at least 1.5 cycles of the FSK modulation frequency at which the attribute of the writing implement can be determined. it can.

[0021]

Next, a coordinate input device according to the present invention will be described.
This will be described with reference to an electronic blackboard 1 according to a preferred embodiment.
In this explanation, when the electronic blackboard 1 draws handwritten characters and figures on the writing surface 21a of the writing panel 10 as a coordinate reading board with the pen 60 as a writing instrument, the position on the writing surface 21a of the pen 60 is It refers to one that is magnetically coupled by a plurality of sense coils 23 laid inside the writing panel 10 and reads its coordinates.

FIG. 1 is an external perspective view showing a main structure of the electronic whiteboard 1. As shown in FIG. 1, the electronic blackboard 1 has a writing panel 10 and a pen 6 for writing on a writing surface 21a.
0 and an eraser 40 for erasing the written trajectory and data indicating the trajectory. The writing panel 10 is provided with a frame-shaped frame 11. The writing panel main body 20 is incorporated in the frame 11. At the lower end of the front surface of the frame 11, a plate-like base 12 is incorporated along the lower end. A plurality of recesses 1 for accommodating and holding the pen 60 are provided on the upper surface of the table 12.
2a is formed. 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.
Is provided. The operation unit 30 has a speaker 31 for reproducing sounds such as operation sounds and warning sounds, and the number of pages storing data indicating the contents written on the writing surface 21a (hereinafter referred to as “writing data”) of seven. A page display LED 32 displayed by the LED of the segment, 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 of the written data stored each time the button is pressed. Erase button 35 to erase
And the stored writing data to the printer 200 (FIG. 2).
Printer output button 36 to output to
And a PC output button 37 that is pressed to output the stored writing data to a personal computer (hereinafter, referred to as “PC”) 100 (see FIG. 2), and a battery exhaustion notification for reporting that the pen 60 has run out of battery. An LED 39 and a power button 38 to be pressed to activate the electronic whiteboard 1 are provided.

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. A cover 14b is attached to the front of the battery case 14 so as to be openable and closable. On the right side of the battery case 14,
A volume control knob 13c for the speaker 31 is provided, and connectors 13b and 13a are provided on the right side thereof. FIG. 2 is a diagram illustrating a state in which the PC 100 and the printer 200 are connected to the electronic whiteboard 1. As shown in FIG. 2, a plug 202 of a connection cable 204 connected to the printer 200 is connected to the connector 13b, and a plug 102 of a connection cable 104 connected to the PC 100 is connected to the connector 13a. With this connection, handwriting data indicating the contents handwritten on the writing surface 21a of the electronic blackboard 1 is output to the PC 100, and the PC 100
Can be displayed on the monitor 103, or handwriting data can be output to the printer 200 and printed 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 at the upper end of the back surface of the frame 11. Here, the height H1 of the writing surface 21a of the present embodiment is 900 mm, and the width W1 is 600 mm. The frame 11 and the base 12 are made of a lightweight synthetic resin such as PP (polypropylene), and the total weight of the electronic blackboard 1 is 10 k.
g or less.

Next, the structure of the writing panel main body 20 will be described with reference to FIG. FIG. 3 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 constituting 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 laminated. ing. In this embodiment, the writing sheet 21 is formed of a laminated PET (polyethylene terephthalate) film to a thickness of 0.1 mm, and the panel 22 is made of acrylic resin, ABS (acrylonitrile-butadiene-styrene copolymer). ), P
It is formed to a thickness of 3.0 mm by C (polycarbonate) or the like. 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. Note that the entire thickness of the frame 11 (see FIG. 1) that holds each end of the writing panel main body 20 is 50 mm.

Next, referring to FIG.
Will be described. FIG. 4A is an explanatory diagram in which the configuration of the sense coil 23 shown in FIG. 3 is partially omitted, and FIG. 4B is a diagram illustrating the sense coil 23 shown in FIG.
It is explanatory drawing which shows the width | variety and overlap pitch. In the following description, among the sense coils 23, the sense coils arranged in the X-axis direction are called X coils, and the sense coils arranged in the Y-axis direction are called Y coils. FIG.
In (a), a small gap is provided in the overlapping portion of each sense coil 23 in order to make it easy to see how the sense coils 23 overlap, but there is no actual gap.

As shown in FIG. 4A, m X coils (X1 to Xm) for detecting the X coordinate of the (X, Y) coordinates of the pen 60 and the eraser 40 are arranged in the X axis direction. Further, in the Y-axis direction, n (Y1-Yn) Y coils for detecting the Y coordinate are arranged orthogonally to the X coils. Each terminal 23a of the X coil is connected to an X coil switching circuit 50a described later, and each terminal 23b of the Y coil is connected to a Y coil switching circuit 50b described later (see FIG. 7). X coil and Y coil are
Each of them is formed in a substantially rectangular shape, and the lengths of the long sides of the rectangular portion are P2Y and P2X, respectively.

As shown in FIG. 4 (b), the length of the short side of the rectangular portion of the X coil is formed to have a width P1, and the adjacent X coils are each overlapped at a half pitch of the width P1. I have. Similarly, the length of the short side of the rectangular portion of the Y coil is also formed to have the width P1, and the adjacent Y coil has the width P1.
Each of them is overlapped at a half pitch of 1. In this embodiment, P1 = 50 mm, P2X = 680 mm, P2
2Y = 980 mm. Also, m = 22 and n = 34. Further, the X coil and the Y coil both have an insulating film layer (for example, an enamel layer) on the surface and have a diameter of 0.34.
It is formed of a 5 mm copper wire.

Next, referring to FIG. 5 and FIG.
A method of detecting the position coordinates of the pen 60 on 1a will be described. FIG. 5A is an explanatory diagram showing a part of the X coils (X1 to X3), and FIG. 5B is a diagram showing the voltages generated in the X coils (X1 to X3) shown in FIG. FIG. 5C is a graph illustrating a relationship with a distance in a width direction, and FIG. 5C is a graph illustrating a voltage difference between mutually adjacent sense coils of the X coils (X1 to X3) illustrated in FIG. . FIG. 6 (a)
FIG. 6B is an explanatory diagram showing the position coordinate table as a graph. FIG. 6B is an explanatory diagram of the position coordinate table.
FIG. 6C is an explanatory diagram showing a storage state of the detection value detected from each X coil. In FIG. 5A, in order to make it easy to see how the X coils (X1 to X3) overlap, a small gap is provided in the overlapping portion.

Since the coil width P1 is 50 mm, P1
1/4 = 12.5 mm. In FIG. 5C,
When the part showing the characteristics of the voltage difference (ex1-ex2) (the part drawn by a solid line) is converted into 8-bit digital data,
The graph shown in FIG. 6A is obtained. What converted this graph into a table format is the position coordinate table 58a shown in FIG. This position coordinate table 58a
Are stored in the ROM 58 (see FIG. 7), and the pen 6
0 is used for calculating the position coordinates.

Therefore, for example, when the pen 60 is located at the point Q2, the voltage difference (ex1-ex2) is detected, and the position coordinate table 58a is referred to based on the detection result, so that the center C1 to the point Q2 can be detected. Of the point Q2 can be obtained because the distance .DELTA.X1 is obtained. The X coil serving as a reference when calculating the position coordinates is determined as follows using the voltage value storage area 59a shown in FIG. That is, all the X coils (X1 to Xm) are scanned, and the scanned voltage values e1 to em are temporarily stored in the voltage value storage area 59a. Then, the X coil indicating the maximum voltage value among the stored voltage values e1 to em is set as the X coil serving as the reference of the position coordinates. In the case described above, the X coil of X1 is used as the reference of the position coordinates by such processing.

With reference to FIG. 7, the main electrical configuration of the electronic whiteboard 1 will be described together with basic coordinate reading processing. FIG. 7 is a block diagram showing an electrical configuration of the electronic whiteboard 1. The details of the reading process according to the present embodiment will be described later together with a flowchart. Here, only the concept of the coordinate detection process executed by the electronic whiteboard 1 of the present embodiment will be described.

The CPU 56 provided in the control unit 2 sends a coil selection signal for sequentially selecting the X coils (X1 to Xm) to the X coil switching circuit 5 via the input / output circuit (I / O) 53.
The output to 0a scans the X coils (X1 to Xm). A signal generated by magnetic coupling between the alternating magnetic field generated from the pen 60 and one of the X coils is amplified by the amplifier 50c, and the amplified signal is
An unnecessary band is filtered by a band-pass filter (BPF) 50 d, and the amplitude is detected by an amplitude detection circuit 51. The amplitude-detected signal is converted into a digital signal corresponding to the amplitude, that is, the voltage value by the A / D conversion circuit 52, and the digital signal is input to the CPU 56 via an input / output circuit (I / O) 53.
Is input to

On the other hand, the CPU 56 determines that the pen 60
The bandpass filter 5 is generated based on the FSK modulated wave oscillated from the pen 60 for a predetermined short period (for example, one or two scan times after the detection of the pen) immediately after being pressed by 1a.
The signal output from 0d is converted into a square wave limiter output signal by the limiter circuit 54, and then output to the FSK demodulation circuit 55 to determine the pen attribute (pen thickness and color information). After that, as described above, A
Based on the digital signal input from the / D conversion circuit 52, the coordinate position calculation is executed as follows. That is, CPU
Reference numeral 56 denotes a voltage value storage area 59a for the X coil of the RAM 59, which stores the respective voltage values indicated by the digital signals input by scanning the X coils (X1 to Xm).
(See FIG. 6C). And CP
U56 calculates the X coordinate of the pen 60 based on each voltage value stored in the RAM 59.

When the calculation of the X coordinate of the pen 60 is completed, scanning of each Y coil (Y1 to Yn) is executed, and the voltage value detected from each Y coil is stored in the voltage value storage area for the Y coil of the RAM 59. . Then, the CPU 56 uses the same method as the calculation of the X coordinate in S308 described above,
The Y coordinate of the pen 60 is calculated.

The pen attribute determined previously is the pen 6
It is stored in a predetermined area of the RAM 59 in association with the X coordinate and the Y coordinate of 0.

The CPU 56 captures a switching signal generated by operating various buttons (see FIG. 1) provided on the operation unit 30 through the I / F circuit 57, and
A page process for returning or sending the page storing the position coordinate data stored in the M59 in page units or deleting the position coordinate data in page units is executed. Further, the CPU 56 operates the audio circuit 31a based on a switching signal generated when various buttons provided on the operation unit 30 are pressed, and the speaker (SP)
From 31, operation sounds such as “P” and “B” are produced.

Next, the configuration of the pen 60 will be described with reference to FIG. FIG. 8 is a side sectional view showing the internal structure of the pen 60. As shown in FIG. 8, the pen 60 is provided with a cylindrical body 61a and a lid 61c detachably attached to the rear end of the body 61a. Body part 61
a, a coil L1, an ink cartridge 63 which can be taken out in a direction indicated by an arrow F2, a pen point 62 inserted into the ink cartridge 63, a circuit board 6
9 and a battery 70 which is a power supply for supplying a current to the circuit board 69. The coil L1 has an inner diameter of about 15 mm, and is formed in an annular shape by a copper wire having a diameter of about 15 mm and a length of 200 turns. Also,
The coil L1 is arranged at a distance of about 20 mm from the tip of the pen tip 62 that contacts the writing surface 21a (see FIG. 1).

Next, the configuration of the circuit board 69 of the pen 60 will be described with reference to FIG. The circuit board 69 is roughly composed of an LC oscillation circuit 69a, a CR oscillation circuit 69b, and a power-on detection circuit 69c. LC
The oscillation circuit 69a includes a coil L, capacitors C1 and C2 disposed at both ends of the coil L and having the other end grounded, and an IC1 connected to both ends of the coil L.
And a resistor R4 similarly connected to both ends of the coil L. The CR oscillation circuit 69b is connected to the I
C2, IC3, a variable resistor R1 having one end connected between the IC2 and IC3, a resistor R2 connected in series with the variable resistor R1, and one end connected to an output terminal of the IC3. A capacitor C4 has the other end connected to the resistor R2, and a resistor R5 having one end connected to the input end of the IC2 and the other end connected to the resistor R2. The CR oscillation circuit 69b is a circuit that oscillates a different modulation frequency for each attribute of the pen 60 in order to distinguish pen attributes such as color and thickness. The power-on detection circuit 69c is connected to the IC4 and the IC5 having one input terminal connected to the output terminal of the IC4 and the other input terminal connected to the output terminal of the IC3 of the CR oscillation circuit 69b. , A capacitor C6 having one end connected to the input end of IC4 and the other end grounded,
And a resistor R6 having both ends connected to the output end of the diode D and the input end of the IC4. And the diode D
Is connected to a switch SW for turning on and off the battery 70 and the circuit board 69. The output terminal of IC5 is connected to the gate terminal of field effect transistor FET1, and the drain terminal of field effect transistor FET1 is connected to one end of capacitor C3. In addition,
The other end of the capacitor C3 is connected to one end of the capacitor C1 so that when FET1 is on, C1 and C3 are connected in parallel.

As a result of the circuit board 69 having the structure shown in FIG. 9, when the power is turned on by pen down,
Since C6 is gradually charged through R6, during this time I
The output of C5 is high, and the circuit board 69
A signal subjected to FSK modulation according to the oscillation cycle of the oscillation circuit 69b is transmitted. Then, after a certain period (determined by C6 and R6) has elapsed, the output of the IC5 becomes low, so that the FET1 is always off and the circuit board 69 is turned off.
A signal without an AM component without K modulation is transmitted. Here, it is important to be able to determine the attribute of the pen during the period in which the signal subjected to the FSK modulation is transmitted, and it is necessary to detect that the frequency is switched by the CR oscillation circuit at least three times. That is, assuming that the period from switching from one frequency to another frequency and transmitting the signal of the first frequency again is one cycle of the modulation frequency, the pen transmits a signal subjected to FSK modulation corresponding to at least 1.5 cycles. . In the present embodiment, this F
The capacities of R6 and C6 are determined so that the period during which the signal subjected to the SK modulation is transmitted is as short as approximately 13 msec after power-on (1 to 2 scan times by the CPU 56).

On the other hand, when the pen comes up, the switch SW
Is turned off and the power supply to the entire circuit is cut off, so that no signal is sent from the circuit board 69. Then, the charge accumulated in C6 is rapidly discharged through the diode D.

Next, control processing executed by the CPU 56 will be described with reference to the flowchart of FIG. The CPU 56 first scans the X coil (S3).
02). Subsequently, the Y coil is scanned (S30).
4). Then, it is determined whether or not a pen is detected based on the scan results of S302 and S304 (S306).
Specifically, when a voltage value exceeding a predetermined threshold value is detected as a result of the X coil scan and the Y coil scan, it is determined that the pen is detected. If a pen is detected (S30)
6: YES), it is determined whether the attribute of the pen is stored (S308). Here, when the pen is detected for the first time, the pen attribute is not stored (S308: N
O), the value of the FSK demodulation circuit 55 is read (S31)
0). Then, the process proceeds to the pen attribute determination process (S31)
2). When the pen attributes can be determined in this way, the pen attributes are stored (S314). And time adjustment (S316).
And terminates the present process once. This time adjustment is a very short time for shifting from the processing for determining the pen attribute to the coordinate detection processing. On the other hand, when the pen attribute is stored (S308: YES), the X coordinate calculation is performed (S318), and the Y coordinate calculation is further performed (S3).
20) The XY coordinates are stored in association with the stored pen attributes (S322). On the other hand, when the pen is not detected even after executing the X coil scan and the Y coil scan (S306: NO), the pen attribute is deleted (S3).
24), exit this processing.

Next, the contents of the pen attribute detecting process will be described with reference to the flowcharts of FIGS.

When the pen attribute detection process starts, FIG.
First, it is determined whether or not a rising edge of a signal has been input (S402). Then, when the rising is detected (S402: YES), the counting process by the counter is started (S404). Then, it is determined whether or not the rising has been input again (S406). The counting process is repeated until the rising is detected again (S406: NO, S404). Then, when the rise is detected again (S406: YES), the process exits the above loop, outputs the count value K (S408), and performs reset (S410). Thereafter, the difference Δm between the first weighted average value (the head part of the register) and the second weighted average value (the tail part of the register) is calculated (S412). Then, the difference Δm is compared with the threshold value m1 (S414),
If Δm ≧ m1 (S414: YES), the threshold determination output is changed (S416), and the process exits. If it is determined that Δm ≧ m1 is not satisfied (S41
4: NO), and passes S416 to exit this processing. Thus, the timing of the frequency change of the FSK-modulated signal wave is monitored.

Next, the counter processing will be described. This counter process is a process for determining what color pen is currently detected. In this counter processing, as shown in FIG. 12, first, it waits for a change in the threshold value determination output (S420). Then, when the threshold value determination output changes (S420: YES), counting is started (S422). Then, it waits again for a change in the threshold value judgment output (S424). In this way, counting is performed from the time when the threshold value determination output changes to the time when the threshold value determination output changes again. Then, when the threshold determination output changes again (S424: YES), the count value is output to the register (S426), and the reset is performed (S428).

Next, the adder processing will be described. In this adder processing, as shown in FIG. 13, first, it is determined whether or not the addition timing has come (S430). Then, when the addition timing comes (S430: YES),
The output values of the counter and the register are added (S43
2). Then, the added value is output (S434). From this addition value, the CPU 56 can determine what color of the pen is being detected.

According to the first embodiment, as shown in FIG. 14, a signal subjected to FSK modulation for judging pen attributes is transmitted only for a predetermined period immediately after pen down, and Of the pen can be determined based on the FSK modulation signal. Then, after the time adjustment, the pen position can be detected based on the signal switched from the FSK modulation to the non-modulated signal. Therefore, the pen is not affected by the AM component, and the position detection accuracy is improved. Be demonstrated. Further, the period during which the FSK demodulation is performed is very short, the load on the CPU 56 is reduced, and other processing such as high-speed serial communication can be performed, so that there is an effect that the overall cost can be reduced.

Next, a second embodiment will be described. The configuration and the like of the electronic blackboard 1 and the pen 60 in the second embodiment are the same as those in the first embodiment. The different part is a part of the pen coordinate detection processing. Therefore, control processing executed by the CPU 56 in the second embodiment will be described with reference to the flowchart of FIG.

In the control processing according to the second embodiment, C
The PU 56 first scans the X coil (S50).
2). Subsequently, the Y coil is scanned (S504).
Then, it is determined whether or not a pen is detected based on the scan results of S502 and S504 (S506). Specifically, as a result of the X coil scan and the Y coil scan,
If a voltage value exceeding a predetermined threshold value is detected, it is determined that a pen has been detected. If a pen is detected (S506: Y
ES), it is determined whether or not the attribute of the pen is stored (S508). Here, when the pen is detected for the first time, the pen attribute is not stored (S508: N
O), the value of the FSK demodulation circuit 55 is read (S51)
0). Then, the process proceeds to pen attribute determination processing (S51).
2). If the pen attributes can be determined in this way, the pen attributes are stored (S514). Then, it is determined whether or not the signal has been switched to the non-modulated signal (S516). After switching to the non-modulated signal, the signal becomes a signal having no AM component, so that the pen position can be detected with high accuracy. Then, when the mode is switched to the non-modulated signal (S516: YES), the present process is temporarily ended. After the pen attribute is determined in this way, since the pen attribute is stored (S508: YES), the X coordinate calculation is executed (S518), the Y coordinate calculation is further executed (S520), and the XY coordinates are stored. (S522). On the other hand, when the pen is not detected even when the X coil scan and the Y coil scan are executed (S506: NO),
The pen attribute is deleted (S524), and the process exits.

Next, the contents of the pen attribute detection processing according to the second embodiment will be described with reference to the flowcharts of FIGS.

When the pen attribute detection process starts, FIG.
First, it is determined whether or not a rising edge of a signal has been input (S602). Then, when the rising is detected (S602: YES), the counting process by the counter is started (S604). Then, it is determined whether or not the rising has been input again (S606). Until the rising edge is detected again, the counting process is repeated (S606: NO, S604). Then, when the rising is detected again (S606: YES), the process exits the above loop, outputs the count value K (S608), and performs reset (S610). Thereafter, a difference Δm between the first weighted average value (the head part of the register) and the second weighted average value (the tail part of the register) is calculated (S612). Then, the difference Δm is compared with the threshold value m1 (S614),
If Δm ≧ m1 (S614: YES), the threshold determination output is changed (S616), and the process exits. If it is determined that Δm ≧ m1 is not satisfied (S61
4: NO), Passes S616 and exits this process. Thus, the timing of the frequency change of the FSK-modulated signal wave is monitored.

Next, the counter processing will be described. This counter process is a process for determining what color pen is currently detected. In this counter processing, as shown in FIG. 17, first, it waits for a change in the threshold value determination output (S620). Then, when the threshold determination output changes (S620: YES), counting is started (S622). Subsequently, it is determined whether or not the count value has become 150 or more (S624). When the count value is 150 or more (S624: YE
S), it is determined that the signal has become a non-modulated signal (S626). On the other hand, if the count value is not 150 or more (S
624: NO), and again waits for a change in the threshold value determination output (S628). In this way, counting is performed from the time when the threshold value determination output changes to the time when the threshold value determination output changes again. Then, when the threshold determination output changes again (S628: YES), the count value is output to the register (S630), and reset is performed (S63).
2).

Next, the adder processing will be described. In this adder processing, as shown in FIG. 18, it is first determined whether or not the addition timing has come (S640). Then, when the addition timing comes (S640: YES),
The output values of the counter and the register are added (S64
2). Then, the added value is output (S644). From this addition value, the CPU 56 can determine what color of the pen is being detected.

Also in the second embodiment, FSK
Since the demodulation is performed only until the color of the pen can be determined, the load on the CPU 56 is reduced as in the first embodiment. As a feature of the second embodiment, as shown in FIG. 19, it is not time adjustment, but a determination is made as to whether or not the signal has been switched from a modulated signal to a non-modulated signal. Can be started, so that there is an effect that there is no waste in the position detection processing.

Next, a third embodiment will be described. In the third embodiment, the configuration of the electronic blackboard 1 and the pen 6
The main configuration of 0 is the same as that of the first embodiment. Further, control processing for pen attribute detection and position coordinate detection can be configured in the same manner as in the first and second embodiments. The difference lies in the configuration of the circuit board 69 of the pen 60. Therefore, the configuration of the circuit board 69 of the pen 60 will be described below.

As shown in FIG. 20, the circuit board 69 is roughly composed of an LC oscillation circuit 69a and a CPU. The coil L, the capacitors C1 and C2, the IC, and the resistor R1 are connected to the LC oscillation circuit 69a as illustrated. The CPU is configured to be able to detect the opening and closing of the switch SW, and to output a signal to the gate terminals of the two field effect transistors FET1 and FET2. The capacitor C3 is connected to the drain terminal of the FET1. The drain terminal of FET2 is connected to capacitors C1 and C2.
And the source terminal of FET1 and
The source terminal of FET2 is grounded. The configuration of the circuit board 69 according to the third embodiment is more conceptually shown in FIG. That is, a switch ON / OFF unit including a switch SW, a control unit including a CPU,
An FSK modulator composed of ET1, FET2 and C3;
The circuit board 69 is constituted by the coil oscillation section including the C oscillation circuit 69a.

Then, the switch SW is operated by pen down.
Is closed, the CPU 70 executes the following processing. That is, as shown in FIG. 22, first, it is determined whether or not the switch SW is turned on (S702). If the switch is on (S702: YES), the FET2 is turned on and the FET1 is turned on and off repeatedly. The FSK modulation signal is set to be output (S704). In this state, the FSK modulation signal is continuously oscillated for 13 msec (S
706). Then, after that, the FET 1 is turned off to set a state in which an unmodulated signal is output (S7).
08). After that, S7 until the switch SW is turned off.
08 is maintained (S710). When the switch SW is turned off (S710: YES), the FE
T2 is also turned off to stop the coil oscillation, and the process ends (S712).

In the third embodiment, the circuit board 69
Is configured as described above. As a result, 13 m after pen down
During the sec, a signal subjected to FSK modulation is transmitted, and 13
After a lapse of msec, an unmodulated signal is transmitted. Therefore, the circuit operates in the same manner as the circuit board described in the first embodiment, and the receiving side executes the pen information detection / coordinate reading processing as described in the first or second embodiment, so that It is possible to detect a pen attribute within a short time of about one or two scans immediately after pen down, and to accurately detect the pen position coordinates based on a non-modulated signal having no AM component in the subsequent position coordinate detection. The same effects as those of the first and second embodiments can be obtained in that it is possible.

The embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and it is possible to adopt various forms without departing from the gist of the present invention. Of course.

For example, in the first embodiment, as shown in FIG. 23, after the pen attribute is determined, the coordinates are adjusted for a predetermined time until switching from the transmission-side modulated signal to the non-modulated signal, and then the coordinates are adjusted. Only the detection process is performed. In the second embodiment, as shown in FIG. 23, after the pen attribute is determined, the time when the modulation signal on the transmission side is switched to the non-modulation signal is detected. Then, the coordinate detection processing is performed after that, but pen attribute determination and coordinate reading processing as shown in (1) to (3) in FIG. 23 may be performed.

More specifically, as shown in (1), the coordinate detection process may be performed immediately after the writing implement is pressed against the board until the writing implement is released, regardless of the determination of the pen attribute.
Also, as shown in the figure, the pen is determined by performing FSK demodulation until switching from the modulation signal on the transmission side to the non-modulation signal,
The coordinate detection processing may be performed immediately after the writing implement is pressed against the board until the writing implement is released, regardless of the determination of the pen attribute. Further, as shown in (1), the coordinate detection process may be performed immediately after the determination of the pen attribute. Further, as shown in (1), the pen attribute may be determined by performing FSK demodulation until switching from the modulation signal on the transmission side to the non-modulation signal, and then the coordinate detection processing may be performed.

Here, the advantages and disadvantages of (1) will be described as follows.

Since the FSK demodulation and the coordinate detection do not occur at the same time, the coordinate detection accuracy is good.
However, several msec (1 scan to 2 scans) after pen detection is discarded.

Since the coordinate detection process is performed after the pen is detected, the initial portion of the stroke has poor coordinate accuracy. However, since the initial part of the stroke can also be used for coordinate detection, there is an advantage that position detection can be performed for the entire writing state of the writing instrument.

Can be said to be an intermediate processing form between the above and.

The advantage of the method is that if the determination of the pen attribute is detected a plurality of times until the modulated signal is switched to the non-modulated signal, the pen attribute determination processing without erroneous determination can be performed.

[0068]

As described above, according to the present invention, while identifying the attributes of writing instruments such as pens and erasers, an alternating magnetic field containing no AM component for position coordinate reading is generated to read coordinates. The accuracy of detecting the position of the writing implement on the board can be improved.

[Brief description of the drawings]

FIG. 1 is an external perspective view illustrating a main configuration of an electronic blackboard according to an embodiment.

FIG. 2 is a perspective view showing a state in which a personal computer and a printer are connected to the electronic whiteboard according to the embodiment;

FIG. 3 is a perspective view showing a corner component of a writing panel main body in the electronic blackboard according to the embodiment.

FIG. 4 is an explanatory diagram illustrating a configuration of a sense coil laid in a writing panel main body in the electronic blackboard according to the embodiment.

FIG. 5 is an explanatory diagram illustrating a relationship between a position of a pen and a voltage generated in an X coil in the electronic blackboard according to the embodiment;

FIG. 6A is an explanatory diagram showing a position coordinate table in the embodiment in a graph form, and FIG. 6B is an explanatory diagram of the position coordinate table in the same embodiment;
FIG. 3C is an explanatory diagram showing a storage state of a voltage value detected from each X coil in the embodiment.

FIG. 7 is a block diagram illustrating an electrical configuration of the electronic blackboard according to the embodiment;

FIG. 8 is a side sectional view showing the internal structure of the pen according to the embodiment.

FIG. 9 is a circuit diagram showing a configuration of a circuit board according to the first embodiment.

FIG. 10 is a flowchart showing the contents of a control process according to the first embodiment.

FIG. 11 is a flowchart showing the contents of a control process according to the first embodiment.

FIG. 12 is a flowchart illustrating the contents of a control process according to the first embodiment.

FIG. 13 is a flowchart showing the contents of a control process according to the first embodiment.

FIG. 14 is an explanatory diagram showing a temporal relationship of control processing according to the first embodiment.

FIG. 15 is a flowchart illustrating the contents of a control process according to the second embodiment.

FIG. 16 is a flowchart showing the contents of a control process according to the second embodiment.

FIG. 17 is a flowchart showing the contents of a control process according to the second embodiment.

FIG. 18 is a flowchart illustrating the contents of a control process according to the second embodiment.

FIG. 19 is an explanatory diagram showing a temporal relationship of control processing according to the second embodiment.

FIG. 20 is a circuit diagram showing a configuration of a circuit board according to a third embodiment.

FIG. 21 is a block diagram schematically illustrating a configuration of a circuit board according to a third embodiment.

FIG. 22 is a flowchart showing the contents of a control process according to the third embodiment.

FIG. 23 is an explanatory diagram showing processing contents on the coordinate reading board side as a modified example.

FIG. 24 is a circuit diagram showing a configuration of a pen oscillation circuit in an electronic blackboard as a conventional example.

FIG. 25 is a circuit diagram showing an equivalent circuit of a configuration of a pen oscillation circuit in an electronic blackboard as a conventional example.

FIG. 26 is an explanatory diagram showing a carrier wave output from a pen in an electronic blackboard as a conventional example.

FIG. 27 is an explanatory diagram showing an oscilloscope screen of a carrier output from a pen on an electronic blackboard as a conventional example.

[Explanation of symbols]

1 ... electronic blackboard, 10 ... writing panel, 23 ...
Sense coil, 60 ... pen, 69 ... circuit board,
69a: LC oscillation circuit, 69b: CR oscillation circuit, 69c: Power-on detection circuit, 70: Battery.

Claims (7)

[Claims] A plurality of sense coils are laid in XY directions, a coordinate reading board for reading coordinates by magnetically coupling the sense coils with an alternating magnetic field, and an alternating frequency of a predetermined frequency when pressed against the coordinate reading board. In a coordinate input device including a writing implement having an oscillation coil that generates a magnetic field, the writing implement sends a writing implement identification signal indicating an attribute of the writing implement for a predetermined period after being pressed against the coordinate reading board, Thereafter, the coordinate input device is configured to transmit a signal having no writing implement identification signal. 2. The coordinate input device according to claim 1, wherein the writing implement transmits an FSK modulation signal indicating an attribute of the writing implement for a predetermined period immediately after pressing the writing implement on the coordinate reading board, and thereafter, performs FSK modulation. A coordinate input device characterized in that the coordinate input device is configured to transmit a signal free from the coordinate. 3. The coordinate input device according to claim 1, wherein the writing instrument includes a rectangular wave generating circuit, a sine wave generating circuit,
A power on / off circuit, wherein the power on / off detection circuit is configured to enable oscillation by the rectangular wave generation circuit only for a predetermined period after power on is detected. Input device. 4. The coordinate input device according to claim 1, wherein the writing instrument includes a CR oscillation circuit, an LC oscillation circuit, and a power-on detection circuit, and the power-on detection circuit detects power-on. A coordinate input device configured to enable oscillation by a CR oscillation circuit only for a predetermined period immediately thereafter. 5. The coordinate input device according to claim 1, wherein the writing instrument comprises an LC oscillation circuit and a CPU, wherein the CPU operates only for a predetermined period immediately after power-on.
A coordinate input device configured to perform modulation frequency control for transmitting a modulated signal. 6. A coordinate reading board for reading coordinates by magnetically coupling a plurality of sense coils in an XY direction, the sense coils being magnetically coupled to an alternating magnetic field; A coordinate input device comprising: a writing implement having a coil for generating a magnetic field, wherein the coordinate reading board performs FSK demodulation for a predetermined period after being pressed by the writing implement. . 7. The coordinate input device according to claim 6, wherein the predetermined period is at least 1.5 cycles of an FSK modulation frequency at which attribute determination of the writing instrument can be performed. Coordinate input device.