JP3945084B2 - Coordinate reader - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a coordinate reader that reads the coordinates of the coordinate input means based on signals generated in a plurality of loop conductors laid on a coordinate input sheet by an alternating magnetic field generated from the coordinate input means.
[0002]
[Prior art]
Conventionally, for example, the coordinate reading apparatus shown in FIG. 16A is known (Japanese Patent Laid-Open No. 5-165560). FIG. 16A is an explanatory diagram showing a configuration of a conventional coordinate reading apparatus.
The coordinate reader shown in FIG. 16A includes X1 to Xm sense coils (loop conductors) for detecting X coordinates and Y1 to Yn sense coils (loop conductors) for detecting Y coordinates. A tablet (coordinate input sheet) 91, a scanning circuit 92 that sequentially scans the sense coils of the tablet 91, and a detection circuit 90 that detects an induction signal generated in the sense coil and calculates coordinates.
When a pen (coordinate input means) 300 having a coil 101 that generates an alternating magnetic field contacts the tablet 91, the sense coil near the pen 300 is guided by magnetic coupling with the alternating magnetic field generated from the coil 101. A signal 97 is induced, and the induction signal 97 is input to the detection circuit 90. The induction signal 97 input to the detection circuit 90 is amplified by the amplifier 93 and subjected to amplitude detection, for example, by the detection circuit 94. Next, the A / D conversion circuit 95 measures the amplitude of the detected induction signal and outputs a digital value indicating the measured value to the CPU 96. Then, the CPU 96 calculates the coordinates of the pen 300 based on the input digital value. For example, a calculation method of selecting a coordinate corresponding to a digital value by referring to a coordinate table in which a digital value and a coordinate are associated with each other is used.
[0003]
However, in the coordinate reading apparatus, since the digital value constituting the coordinate table is a fixed value set in advance, when the battery built in the pen 300 is consumed and the output level of the alternating magnetic field decreases, the output level is reduced. Since the induction signal generated in the sense coil by the reduced alternating magnetic field is detected and the position coordinate corresponding to the amplitude value of the induction signal is selected, there is a problem that the reading accuracy of the coordinate is lowered. FIG. 16B is an explanatory diagram showing a decrease in reading accuracy of coordinates. As shown in FIG. 16B, the coordinates read based on the original output voltage V1 detected from the sense coil when the battery is not consumed are P1, but the voltage V2 when the output is reduced when the battery is consumed. As a result, the coordinates read by P becomes P2, and a reading error of ΔP occurs.
[0004]
In order to solve such a problem, a method of correcting the coordinate table in response to a voltage drop has been considered (Japanese Patent Laid-Open No. 7-56777). FIG. 16C is a graph showing the relationship between the voltage generated in the sense coil and the position of the pen. The above method is a method of detecting the maximum value Va of the voltage generated in the sense coil, comparing the maximum value Va with a preset reference level, and correcting the coordinate table based on the comparison result. .
[0005]
[Problems to be solved by the invention]
However, there is a problem that the number of times that the coordinates can be corrected is small because there are only the same number of points that can detect the maximum value when the number of loop-shaped sense coils is one. In particular, when creating a coordinate input sheet with a large coordinate input area, if the arrangement interval of the sense coils is widened, the number of points at which the maximum value can be detected decreases, so the number of times the coordinate table can be corrected further decreases. Resulting in. In other words, if the interval until correction is performed becomes longer, the number of coordinates that are not corrected increases accordingly, and there is a problem that the overall reading accuracy is lowered.
In addition, as shown in FIG. 16C, since the vicinity of the maximum value has characteristics that are close to flat with a gradual change, it is difficult to detect the true maximum value. There is also a problem that it cannot be corrected.
[0006]
The present invention has been made to solve the above-described problem, and an object of the present invention is to realize a coordinate reading apparatus that can increase the accuracy of reading coordinates by increasing the number of points where the coordinates can be corrected.
[0007]
[Means for solving the problems, functions and effects of the invention]
In order to achieve the above object, according to the first to seventh aspects of the present invention, a coordinate input surface for inputting coordinates by means of coordinate input means for generating an alternating magnetic field, and a lower side of the coordinate input surface are installed. A coordinate input sheet having a plurality of loop-shaped conductors, and detecting a signal level generated in the loop-shaped conductor by an alternating magnetic field generated from the coordinate input means, and the coordinates based on the detected signal level In a coordinate reader that reads the coordinates of the coordinate input means on the input surface,
Of the second and third loop conductors adjacent to the first loop conductor that generates the maximum signal level, the signal level generated in the third loop conductor having the smaller signal level is a predetermined signal level. Signal level generated on one of the first and second loop conductors when the signal level is lower And a reference signal level set for the one corresponding to a predetermined intensity of the alternating magnetic field, The technical means that the correction means for correcting the coordinates based on the above is provided.
[0008]
The correcting means has a signal level generated in the third loop conductor having the smaller signal level among the second and third loop conductors adjacent to the first loop conductor that has generated the maximum signal level. Signal level generated on one of the first and second loop conductors when the signal level is lower than the predetermined signal level And a reference signal level set for the one corresponding to the predetermined strength of the alternating magnetic field, Correct the coordinates based on.
That is, when the coordinate input means on the coordinate input surface generates an alternating magnetic field, a signal is generated in each of the plurality of loop conductors. In addition, among the plurality of loop conductors where the signals are generated, a maximum level signal is generated in a certain first loop conductor, and the second and third loop conductors on both sides of the first loop conductor. The signal having the second highest level is generated in one of the signals, and the signal having the third highest signal is generated in the other.
Therefore, in the case where the loop conductor having the smaller signal level, that is, the third largest signal is used as the third loop conductor, the signal level generated in the third loop conductor is higher than the predetermined signal level. The signal level generated at one of the first and second loop conductors is the correction timing when the signal level is low And a reference signal level set for the one corresponding to the predetermined strength of the alternating magnetic field, Correct the coordinates based on.
That is, for example, as shown in FIG. 8, the null point (N1, N2,...) That is the timing for correcting the coordinates is the center line (C1) of the sense coil (loop conductor) by the pen 60 (coordinate input means). , C2...) To the next center line, there are always two between the distances d1. Therefore, the correction is based on the maximum value in which only one exists between the distances d1. Can be increased by a factor of two.
Therefore, since the uncorrected interval can be shortened, the coordinate reading accuracy can be increased.
Further, as described in the 39th paragraph, the signal level used when correcting the coordinates is the first sense coil (first loop shape) that generates the maximum signal level when the pen 60 is used. Of the second and third sense coils (second and third loop conductors) on both sides of the conductor), a signal generated in the third sense coil (third loop conductor) having the smaller signal level. It may be the signal level f generated in the first sense coil (first loop conductor) when the level is substantially 0 (null point N4), or the second sense as described in the 61st paragraph. The signal level generated in the coil (second loop conductor) may be used.
[0009]
According to a second aspect of the present invention, in the coordinate reading apparatus according to the first aspect, the correction means determines a signal level used for reading the coordinates, A signal level generated at one of the first and second loop conductors; Said Set for one Reference signal level With A technical means of correcting based on the ratio is used.
[0010]
In other words, the ratio is determined by the signal level generated on one of the first and second loop conductors. Set for said one In order to show how much it has decreased with respect to the reference signal level, by correcting the coordinates based on the ratio, it is possible to read the exact coordinates of the coordinate input means even when the strength of the alternating magnetic field is reduced Can do.
[0011]
According to a third aspect of the present invention, in the coordinate reading apparatus according to the first or second aspect, a signal level smaller than the predetermined signal level of the signal level generated in the third loop conductor is substantially 0. Use technical means that
[0012]
That is, it is easier to detect the timing when the timing at which the signal level generated in the third loop-shaped conductor becomes substantially 0 than when the timing at which the signal level is lower than the predetermined signal level is detected. Can do.
[0013]
According to a fourth aspect of the present invention, in the coordinate reading apparatus according to any one of the first to third aspects, The predetermined signal level is The technical means that the level of noise generated in the coordinate reader is larger when the alternating magnetic field is not generated from the coordinate input means is used.
[0014]
That is, the above A given level If it is set below the level of noise generated in this coordinate reader, the correction timing may not be detected when the noise occurs. A given level By setting the level larger than the noise level, the correction timing can be reliably detected.
[0015]
According to a fifth aspect of the present invention, in the coordinate reading apparatus according to any one of the first to fourth aspects, the loop-shaped conducting wire is formed in a horizontally long annular shape and is adjacent to each other in a loop shape. Occurs in the adjacent loop conductors in a range surrounded by a center line that bisects one loop conductor of the conductor in the longitudinal direction and a center line that bisects the other loop conductor in the longitudinal direction. The technical means is used that the signal level is higher than the signal level generated in the loop conductors other than the adjacent loop conductors.
[0016]
That is, in the above range, if the signal level generated in the loop conductors adjacent to each other is smaller than the signal level generated in the loop conductors other than the loop conductors adjacent to each other, the loops other than the loop conductors Since the coordinates are corrected based on the signal level generated in the wire conductors, and accurate coordinates cannot be obtained, the signal levels generated in the mutually adjacent loop conductors are other than the loop conductor wires adjacent to each other. The loop conductor is arranged so as to be higher than the signal level generated in the loop conductor.
[0017]
According to a sixth aspect of the present invention, in the coordinate reading device according to any one of the first to fifth aspects, the loop-shaped conductive wire includes a primary peak of a signal level generated in each conductive wire, A technical means is used in which the boundaries generated in each loop conductor are arranged at substantially equal intervals at the boundary where the signal level between the secondary peaks appearing at both ends of the primary peak is minimized.
[0018]
That is, when the signal level that is the minimum value of the boundary between the primary peak and the secondary peak of the signal level generated in the loop conductor is the signal level generated in the third loop conductor, the boundary is the correction timing. Therefore, the correction timing intervals can be equalized by arranging the boundaries at substantially equal intervals, so that equal correction can be performed.
[0019]
According to a seventh aspect of the present invention, in the coordinate reading apparatus according to any one of the first to sixth aspects, a signal level generated in one of the first and second loop conductors is as follows. The technical means of notifying that the alternating magnetic field generated from the coordinate input means has been reduced in response to a decrease in strength is used.
[0020]
That is, when the strength of the alternating magnetic field generated from the coordinate input means decreases, the signal level generated in one of the first and second loop conductors becomes smaller than a predetermined value. The user of this coordinate reading apparatus can be notified that the strength of the alternating magnetic field has been reduced.
For example, as described in the embodiments of the invention described later, when the battery built in the pen (coordinate input means) is exhausted, the signal level generated in one of the first and second loop conductors decreases. Therefore, when the signal level becomes smaller than a predetermined value, the battery running out notification LED provided in the electronic blackboard (coordinate reading device) is turned on, or a warning sound is reproduced by a speaker. The user can be notified of the cut.
The coordinate input sheet includes a film shape, a sheet shape, or a plate shape, and includes those having flexibility or not having flexibility.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
[First Embodiment]
Hereinafter, a first embodiment of a coordinate reading apparatus according to the present invention will be described with reference to the drawings.
In each embodiment described below, as a coordinate reading apparatus according to the present invention, a so-called electronic blackboard that electrically reads handwritten characters or figures drawn on a coordinate input sheet will be described as an example.
[Main configuration]
First, the main configuration of the electronic blackboard according to the first embodiment will be described with reference to FIGS. 1 and 2.
FIG. 1 is an external perspective view showing the main configuration of the electronic blackboard, and FIG. 2 is an explanatory view showing a state in which a personal computer (hereinafter abbreviated as a PC) and a printer are connected to the electronic blackboard shown in FIG. is there.
[0022]
The electronic blackboard 1 is provided with 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 is provided with a frame-like frame 11, and the writing panel body 20 is incorporated in the frame 11. A plate-like table 12 is attached to the front lower end of the frame 11 so as to protrude from the front surface along the lower end. A concave portion 12a having a semicircular cross section for accommodating the pen 60 is formed on the upper surface of the table 12, and a flat surface portion 12b for placing the eraser 40 and the like is formed on the right side of the concave portion 12a. .
[0023]
An operation unit 30 is provided on the front right side of the frame 11. The operation unit 30 includes a speaker 31 that reproduces sounds such as operation sounds and warning sounds, and the number of pages in which data indicating the contents written on the writing surface 21a (hereinafter abbreviated as writing data) is stored in 7 segments. LED page number display LED 32, page return button 33 that returns one page each time it is pressed, page feed button 34 that feeds one page each time it is pressed, and one page that is erased each time the stored writing data is pressed Erasing button 35, printer output button 36 for outputting the stored writing data to printer 200 (FIG. 2), and PC output button for outputting the stored writing data to PC 100 (FIG. 2) 37, an LED 39 for notifying that the pen 60 is out of battery, and a power button for starting or stopping the electronic blackboard 1. And down 38 it is provided.
[0024]
A battery case 14 is provided at the lower front portion of the frame 11 to accommodate four AA dry batteries 14a serving as a power source for the electronic blackboard 1. A lid 14b is attached to the front surface of the battery case 14 so as to be openable and closable. It has been. A volume adjustment knob 13c for adjusting the volume of the speaker 31 is provided on the right side of the battery case 14, and connectors 13b and 13a are provided on the right side thereof. As shown in FIG. 2, a plug 202 of a connection cable 201 connected to the printer 200 is connected to the connector 13b, and a plug 102 of a connection cable 101 connected to the PC 100 is connected to the connector 13a.
That is, writing data indicating the contents written on the writing surface 21 a of the electronic blackboard 1 is output to the PC 100, and the contents written on the electronic blackboard 1 can be viewed by the monitor 100 a provided in the PC 100. It is also possible to output writing data to the printer 200 and print the contents written on the electronic blackboard 1 on the printing paper 203.
[0025]
Further, metal fittings 15 for attaching the electronic blackboard 1 to the wall are attached to both ends of the upper end of the back surface of the frame 11.
In this embodiment, the height H1 of the writing surface 21a is 900 mm, and the width W1 is 600 mm. Moreover, the frame 11 and the base 12 are formed lightly by a synthetic resin such as polypropylene, and the total weight of the electronic blackboard 1 is 10 kg or less.
[0026]
[Network configuration]
Next, the configuration of a network when data communication is performed between a plurality of electronic blackboards 1 will be described with reference to FIG.
Here, a case where communication is performed between a plurality of rooms provided with the electronic blackboard 1 or between companies in the company will be described as an example.
The room 3 in the company 2 includes an electronic blackboard 1, a PC 100 connected to the electronic blackboard 1, and a LAN board 103 connected to the PC 100. The room 4 includes the electronic blackboard 1 and A PC 100 connected to the electronic blackboard 1 and a modem 108 connected to the PC 100 are provided. The LAN board 103 provided in each room 3 is connected to the HUB 105 by a LAN 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 communication switching network 301.
Although not shown, in the other company 5, as in the company 2, an electronic blackboard 1 that can communicate via a PC is provided.
[0027]
Here, a data flow in the network will be described.
The writing data stored in the electronic blackboard 1 provided in a room 3 is transmitted from the PC 100 to the PC 100 in the designated room 3 via the LAN board 103 and the HUB 105. The person who has received the data displays the received data on the monitor 100a provided in the PC 100 (FIG. 2) or prints the received data on the sheet 203 by the printer 200 connected to the PC 100. (FIG. 2), the contents of the received data can be viewed.
The handwritten data can also be attached to an e-mail as an image file in a TIFF (Tag Image File Format) format, for example, and transmitted from the server 106 to another company 5 via the Internet 300. As a result, the other company 5 can view the contents of the written data by decoding the image file attached to the electronic mail transmitted from the company 2.
[0028]
[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 body 20.
The writing panel body 20 includes a writing sheet 21 having a writing surface 21a, a plate-like panel 22, a frame-shaped mounting panel 24 on which a sense coil 23 is laid, and a noise-blocking plate-like back panel 25. It is the structure which laminated | stacked in order.
In this embodiment, the writing sheet 21 is formed with a thickness of 0.1 mm by a bonded PET (polyethylene terephthalate) film, and the panel 22 is made of acrylic resin, ABS (acrylonitrile-butadiene-styrene copolymer). , PC (polycarbonate) or the like to a thickness of 3.0 mm. The mounting panel 24 is formed to a thickness of 40 mm from a foamed resin material such as polystyrene foam, and the back panel 25 is formed to a thickness of 1.0 mm from a conductive material such as aluminum. Furthermore, the entire thickness of the frame 11 that holds each end of the writing panel body 20 is 50 mm.
[0029]
[Configuration of Sense Coil 23]
Next, the configuration of the sense coil 23 will be described with reference to FIGS.
FIG. 5A is an explanatory diagram illustrating a part of the configuration of the sense coil 23 illustrated in FIG. 4, and FIG. 5B illustrates the width and overlap of the sense coil 23 illustrated in FIG. It is explanatory drawing which shows a pitch. FIG. 8 is an explanatory diagram showing the correspondence between the movement of the pen 60 and the voltage generated in the sense coil.
In the following description, a sense coil arranged in the X-axis direction among the sense coils 23 is referred to as an X coil, and a sense coil arranged in the Y-axis direction is referred to as a Y coil.
As shown in FIG. 5A, m X coils X1 to Xm for detecting the X coordinates of the (X, Y) coordinates of the pen 60 and the eraser 40 are arranged in the X-axis direction. In the Y-axis direction, n Y coils Y1 to Yn for detecting the Y coordinate are arranged orthogonal to the X coil. Each of the X coil and the Y coil is formed in a horizontally long annular shape (substantially rectangular shape in this embodiment), and the lengths of the long sides of the rectangular portion are P2X and P2Y, respectively.
In FIG. 5A, the sides of the coils are drawn so as not to overlap in order to make the arrangement of the coils easy to understand. However, in practice, for example, each Y coil is placed on the long side of the X coil X1. The short sides of Y1, Y2, Y3. The terminals 23a and 23b are configured with a minimum interval.
[0030]
As shown in FIG. 5B, the X coils are each formed to have a width (the length of the short side of the rectangular portion) P1, and the adjacent X coils are overlapped at a pitch of P1 / 2. . Each Y coil is also formed with a width P1, and adjacent Y coils are overlapped with each other at a pitch of P1 / 2. Each terminal 23a of the X coil is connected to the X coil switching circuit 50a, and each terminal 23b of the Y coil is connected to the Y coil switching circuit 50b (FIG. 10).
In FIG. 8, the center lines of the X coils X1, X2, and X3 are C1, C2, and C3, respectively, and the voltages generated in the X coils X1, X2, and X3 are ex1, ex2, and ex3, respectively. The voltages ex1 to ex3 are maximal at the points intersecting with the center lines C1 to C3 of the sense coils, respectively, and exhibit a single peak property that decreases as the end is approached. Further, secondary peaks ex1 (2) to ex3 (2) appear at both ends of the primary peaks of the voltages ex1 to ex3. Further, each sense coil has a distance between the center lines of the adjacent sense coils as d1, and a distance between the center line of the sense coil and a null point (N1 to N6...) Of a voltage generated in the sense coil. When d2 is d2, they are arranged so that the relationship d2 = 2d1 / 3 is established.
However, the point where the voltage generated in the sense coil is minimal or “0” at the boundary between the primary peak and the secondary peak is called a null point. As a result, there are two null points in the width d1 of each sense coil, and the null points are evenly present at intervals of Δd.
[0031]
In addition, in the range between the center lines of the sense coils adjacent to each other, the signal level generated in the sense coils adjacent to each other is higher than the signal level generated in the sense coils other than the sense coils adjacent to each other. Are arranged as follows. For example, in FIG. 8, in the range between the center lines C1 and C2 of the X coils X1 and X2 adjacent to each other, the signal levels ex1 and ex2 generated in the X coils X1 and X2 are the signal levels ex3 generated in the X coil X3. It arrange | positions so that it may become larger.
Here, the width P1 of the coil may be wide as long as the voltage generated in the coil exhibits unimodality. Further, as long as the own null point is outside the center of the adjacent coil, the overlapping portion may be narrowed, that is, narrower than P1 / 2. As a result, it is possible to detect the position coordinates of a large area with fewer coils.
In this embodiment, P1 = 80 mm, P2X = 680 mm, and P2Y = 980 mm. Further, m = 13 and n = 20. Further, the distance between its own null points (for example, null points N2 and N5 in the case of X coil X2) is 92 mm, and d1 is 45 mm at the maximum. Both the X coil and the Y coil are formed of a copper wire having a diameter of 0.35 mm and having an insulating coating layer (for example, enamel layer) on the surface.
[0032]
[Position coordinate table]
Next, a position coordinate table for detecting the position coordinates of the pen 60 on the writing surface 21a will be described with reference to FIGS.
FIG. 6A is an explanatory diagram showing a part of the X coils X1 to X3, and FIG. 6B shows the voltage generated in the X coils X1 to X3 shown in FIG. 6A and the distance in the width direction. FIG. 6C is a graph showing a voltage difference between adjacent sense coils of the X coils X1 to X3 shown in FIG. 6A. FIG. 7A is an explanatory diagram showing the position coordinate table in a graph, FIG. 7B is an explanatory diagram of the position coordinate table, and FIG. 7C is an explanatory diagram of the corrected position coordinate table. is there.
As shown in FIG. 6C, the voltage difference between the adjacent sense coils of the X coils X1 to X3 has a maximum value on the center line C1 to C3 of the sense coil. The graph is such that it becomes zero at the midpoint of the long side portion of the sense coil, that is, at the midpoint of the portion where the adjacent sense coils overlap.
[0033]
For example, in FIG. 6C, a graph (part indicated by a solid line) indicating (ex2-ex1) is a distance (overlapping) from the center line C2 of the X coil X2 to the intermediate point Q1 of the part where the X coil X2 is overlapped. The relationship between 1/2 of the pitch, that is, P1 / 4) and (ex2-ex1) is shown. Now, if the pen 60 is present at the point Q2, the distance ΔQ2X from the center line C2 to the point Q2 can be detected by detecting (ex2-ex1), so that the X coordinate of the point Q2 can be obtained.
For example, in FIG. 6C, when the voltage difference (ex2-ex1) of the portion (the portion drawn by a solid line) indicating the characteristic of (ex2-ex1) is converted into 8-bit digital data, the graph shown in FIG. Get. When this graph is converted into a table format, a position coordinate table 58a shown in FIG. 7B is obtained. The position coordinate table 58a is stored in the ROM 58 (FIG. 10) or the like and used for calculating the position coordinates of the pen 60.
[0034]
[Main configuration of pen 60]
Next, the main configuration of the pen 60 will be described with reference to FIG.
9A is an explanatory diagram showing the internal structure of the pen 60, and FIG. 9B is an explanatory diagram showing the electrical configuration of the pen 60 shown in FIG. 9A.
The pen 60 is provided with a cylindrical body portion 61a and a lid 61c that is detachably attached to the rear end of the body portion 61a. To generate an alternating magnetic field from the coil L1, the coil L1, the ink cartridge 63 that can be taken out in the direction indicated by the arrow F2, the pen tip 62 inserted at the tip of the ink cartridge 63, and the coil L1 are provided inside the body portion 61a. A circuit board 69 on which the oscillation circuit is mounted and a battery 70 for supplying power to the circuit board 69 are incorporated.
[0035]
Further, a push button type switch 67 is provided between the ink cartridge 63 and the circuit board 69 for supplying and shutting off power to the oscillation circuit and the like. The switch 67 presses the pen tip 62 against the writing surface 21a (FIG. 1) and turns ON when the ink cartridge 63 moves in the direction indicated by the arrow F1, and turns OFF when the ink cartridge 63 returns in the direction indicated by the arrow F2. That is, an alternating magnetic field is generated from the coil L1 when writing is performed on the writing surface 21a by the pen 60.
As shown in FIG. 9B, the circuit mounted on the circuit board 69 carries a CR oscillation circuit 69e in which a different oscillation frequency is set for each attribute of the pen and a signal oscillated from the CR oscillation circuit 69e. An LC oscillation circuit 69c that oscillates a carrier wave to be transmitted and an FSK circuit 69d that modulates the oscillation frequency of the LC oscillation circuit 69c with the oscillation frequency of the CR oscillation circuit 69e by FSK (Frequency Shift Keying).
For example, the carrier frequency is 410 kHz, and the oscillation frequency of the CR oscillation circuit 69e is 4.1 kHz in the case of a black pen.
The eraser 40 includes a coil that generates an alternating magnetic field, an oscillation circuit, a battery, and the like.
[0036]
[Electrical configuration of electronic blackboard 1 and main control contents]
Next, an electrical configuration of the electronic blackboard 1 and main control contents will be described with reference to FIGS. 10 and 12.
FIG. 10 is an explanatory diagram showing the electrical configuration of the electronic blackboard 1 in blocks, and FIG. 12 is a flowchart showing the main control contents by the CPU 56 shown in FIG.
As shown in FIG. 10, the control device 50 built in the electronic blackboard 1 includes an X coil switching circuit 50a for sequentially switching X coils from X1 to Xm by a switching element such as a transistor (for example, MOS FET), and Y And a Y coil switching circuit 50b for sequentially switching the coils from Y1 to Yn. The ROM 58 stores various control programs executed by the CPU 56, a position coordinate table 58a (FIG. 7B), and the like.
[0037]
As shown in FIG. 12, when the CPU 56 detects that the power button 38 (FIG. 1) is pressed and the power is turned on (step (hereinafter abbreviated as S) 100), the CPU 56 stores the control program stored in the ROM 58, Initial setting such as loading the position coordinate table 58a into the work area of the RAM 59 is performed (S200), and coordinate reading processing is performed (S300).
[Coordinate reading process]
Here, the coordinate reading process will be described with reference to FIG. 8, FIG. 11, and FIG.
FIG. 11A is an explanatory diagram showing a voltage value and a voltage drop when the timing for correcting the position coordinate table 58a is reached, and FIG. 11B is an explanatory diagram showing a part of the contents stored in the RAM 59. FIG. 11C is an explanatory diagram showing a state in which the detected value detected from each X coil by scanning is stored in the temporary storage area 59a of the RAM 59 in association with the coil number. FIG. 13 is a flowchart showing the flow of the coordinate reading process executed by the CPU 56 in S300 of FIG.
[0038]
First, the features of this coordinate reading process will be described.
The position coordinate table 58a shown in FIG. 7B shows a voltage difference DIFF (8-bit digital value) between the sense coil that generates the maximum voltage and the sense coil that generates the second highest voltage, and the center line of the sense coil. It is configured in association with the distance ΔX, and the position coordinates are calculated using ΔX corresponding to the calculated DIFF.
However, since DIFF is a fixed value measured in a state where the strength of the alternating magnetic field generated from the pen 60 is not reduced, that is, in a state where the battery 70 of the pen 60 is not consumed, the battery 70 of the pen 60 is consumed. If the strength of the alternating magnetic field decreases and the value of DIFF decreases, the corresponding distance ΔX increases, resulting in an error in the calculated position coordinates.
[0039]
Therefore, when the battery 70 of the pen 60 is not depleted, the third of the second and third sense coils adjacent to the first sense coil that has generated the maximum signal level has the smaller signal level. The signal level generated in the first sense coil when the signal level generated in the sense coil is approximately 0 is stored in advance in the ROM 58 as the reference value g, and the maximum value is obtained when the pen 60 is used. The first when the signal level generated in the third sense coil with the smaller signal level among the second and third sense coils adjacent to the first sense coil that generated the signal level is approximately zero. The ratio between the signal level f generated in the sense coil and the reference value g is calculated, and the DIFF of the position coordinate table 58a is corrected using the ratio, whereby the level due to the decrease in the strength of the alternating magnetic field. To correct an error of coordinates.
For example, in the example shown in FIG. 8, the X coil is scanned when the battery 70 of the pen 60 is not depleted, and both sides of the X coil X2 that generates the maximum signal level ex2 when the pen 60 passes the point Q4. Among the X coils X1 and X3, the voltage e2 generated in the X coil X2 when the voltage generated in the X coil X1 having the smaller voltage becomes substantially 0 (null point N4) is set to the reference value g. This reference value g is stored in the ROM 58 in advance.
Then, as shown in FIG. 8, when the X coil X2 is scanned when the pen 60 passes the point Q4 (null point N4), the X coil X2 is generated as shown in FIG. A ratio r = f / g between the voltage f (corresponding to the signal level generated in one of the first and second loop conductors of the present invention) and the reference value g is calculated, and DIFF is used using the ratio r. Correct.
[0040]
[Coordinate reading process]
Next, the flow of the coordinate reading process will be described with reference to FIG.
The CPU 56 operates the X coil switching circuit 50a to scan the X coil (S302). At this time, the signal generated in each X coil by the magnetic coupling between the alternating magnetic field generated from the pen 60 placed on the writing surface 21a and the X coil is amplified by the amplifier 50c, and the amplified signal is Unnecessary bands are filtered by the pass filter 50d, and amplitude detection is performed by the amplitude detection circuit 51. Subsequently, 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 is input to the CPU 56 via the I / O circuit 53, and the CPU 56 detects the pen 60. (S304: Yes).
[0041]
The CPU 56 scans the X coils X1 to Xm, and detects the detection values (signal levels according to the present invention) e1 to em indicated by the digital signals as shown in FIG. Corresponding data are sequentially stored in the temporary storage area 59a (FIG. 11B) of the RAM 59 (S306).
The signal that has passed through the bandpass filter 50d is shaped into a square wave pulse by the limiter circuit 54. The FSK demodulation circuit 55 performs FSK demodulation based on the square wave pulse input from the limiter circuit 54, and the FSK demodulation result Is output to the CPU 56 via the I / O circuit 53. Then, the CPU 56 reads the value output from the FSK demodulation circuit 55, and determines the pen attribute based on the value (S308).
For example, if the value output from the FSK demodulation circuit 55 is 245 when the oscillation frequency of the CR oscillation circuit 69e when the black pen is used is 4.1 kHz, the CPU 56 reads from the FSK demodulation circuit 55. When the value is 245, it is determined that the pen attribute is black.
[0042]
Then, the CPU 56 extracts the maximum detection value e (max) from the detection values stored in the RAM 59, and the coil number (hereinafter referred to as max) of the X coil that generated the detection value e (max). The data is stored in the RAM 59 (S310).
For example, as shown in FIG. 6A, the pen 60 exists at the position Q2, and as shown in FIG. 6B, voltages e1, e2, e3 are detected from the X coils X1, X2, X3, respectively. Then, the maximum voltage value e2 is selected, and the coil number 2 of the X coil that generated the voltage value e2 is stored in the RAM 59 as max.
Then, the CPU 56 extracts one detection value e (max-1) from the detection values on both sides of e (max), and the coil number of the X coil (hereinafter, referred to as the detection value e (max-1)). (referred to as max2) is stored in the RAM 59 (S312). For example, in the example shown in FIG. 6, the coil number 1 of the X coil X1 that has generated the detection value e1 is stored.
Subsequently, the CPU 56 extracts the other detection value e (max + 1) from the detection values on both sides of e (max), and the coil number of the X coil that generated the detection value e (max + 1) (hereinafter referred to as max3). ) Is stored in the RAM 59 (S314). For example, in the example shown in FIG. 6, the coil number 3 of the X coil X3 that has generated the detection value e3 is stored.
[0043]
Subsequently, the CPU 56 determines whether or not the detected value e (max-1) is larger than the detected value e (max + 1) (S316). If larger (S316: Yes), the detected value e (max-1) is set. The detection value e (max + 1) is set to the first voltage v1 and the second voltage v2 (corresponding to the signal level generated in the third loop conductor having the smaller signal level of the present invention) and stored in the RAM 59. The coil number of the X coil that has generated the second largest voltage is set to max2 and stored in the RAM 59 (S318).
For example, in the example shown in FIG. 6, since e1> e3, e1 is set to the first voltage v1 and e3 is set to the second voltage v2 and stored.
When the detected value e (max-1) is smaller than the detected value e (max + 1) (S320: No), the CPU 56 sets the detected value e (max + 1) to the first voltage v1 and the detected value e (max-1). Is set to the second voltage v2 and stored in the RAM 59, and the coil number of the X coil that has generated the second largest voltage is set to max3 and stored in the RAM 59 (S320).
[0044]
[Correction of position coordinate table]
Subsequently, the CPU 56 determines whether or not the second voltage v2 is 0 (S322). That is, it is determined whether or not the pen 60 has passed the null point when the X coil is scanned in S302. Here, if the pen 60 passes the null point (S322: Yes), it is the timing to execute the correction of the position coordinate table 58a, so the following S326 to S330 are executed to correct the position coordinate table 58a. First, the position coordinate table 58a loaded in the work area of the RAM 59 in the initial setting (S200) is discarded, the position coordinate table 58a is newly reloaded from the ROM 58 into the work area of the RAM 59, and the pen attributes determined in S308 are changed. The data are stored in the work area in association with each other (S326). For example, when the pen attribute is black, as shown in FIG. 11B, the position coordinate table 58a reloaded in the work area is set to a position coordinate table dedicated to the black pen.
The reason why the old position coordinate table 58a is discarded is to prevent recorrection of the corrected position coordinate table.
[0045]
Subsequently, the CPU 56 calculates a ratio r between e (max) extracted in S310 and a reference value (reference signal level according to the present invention) g (S328), and the ratio r is stored in the position coordinates stored in the work area. Each value of DIFF in the table 58a is multiplied (S330).
For example, if the reference value g is 256, in the example shown in FIG. 11C, since e (max) is f = 128, the ratio r = f / g = 128/256 = 0.5 is positioned. By multiplying each DIFF in the coordinate table 58a, as shown in FIG. 7C, a new position coordinate table 58b in which the value of each DIFF is corrected to about ½ is obtained. In addition, each DIFF shown in FIG.7 (C) rounds off the result which multiplied the ratio r.
Then, the CPU 56 determines whether or not the ratio r is equal to or less than a preset value r1 (S336). If the ratio r is equal to or less than the set value r1 (S336: Yes), the battery 70 of the pen 60 is depleted. (S338).
For example, the battery exhaustion notification LED 39 (FIG. 1) is turned on or blinked. Alternatively, the audio circuit 31a (FIG. 10) may be operated to reproduce and notify an electronic sound such as “pea” from the speaker 31 (FIG. 1). Further, the set value r1 is selected and set from the range of 0.25 ≦ r1 ≦ 0.5, for example.
[0046]
[Coordinate calculation]
Then, the CPU 56 calculates the X coordinate by the following procedure (S340).
First, when the coil number max2 is stored in S318, it can be determined that the coil number max2 (= max-1) exists in the negative direction of the X axis from the coil number max. Then, the variable SIDE is set to (−1). If the coil number max3 is stored in S320, it can be determined that the coil number max3 (= max + 1) is present in the + direction of the X axis from the coil number max. Then, the variable SIDE is set to 1.
In the example shown in FIG. 6, since max = 2 and max2 = 1, the variable SIDE is set to (−1).
Subsequently, the CPU 56
[0047]
DIFF = e (max) −v1 (1)
[0048]
And the position coordinate closest to the calculated DIFF is read from the position coordinate table 58a stored in the ROM 58, and set as OFFSET. Subsequently, the CPU 56
[0049]
X1 = (P1 / 2) × max + OFFSET × SIDE (2)
[0050]
Is calculated to obtain the X coordinate, and the X coordinate is stored in the fixed area 59b (S340). Here, (P1 / 2) × max indicates the X coordinate of the center of the coil number max. In the example shown in FIG. 6, the equation (2) becomes X = (P1 / 2) × 2 + (e2−e1) × (−1), and the X coordinate of the point Q2 is X to X from the center line C2 of the X coil X2. The distance corresponds to (e2-e1) in the negative direction of the axis, for example, coordinates that are separated by ΔQ2X.
Although not shown, the CPU 56 also executes the same processing as the above-described S302 to S340 for the Y coils Y1 to Yn. In this process, when v2 = 0, the position coordinate table 58a is corrected in the same manner as in S326 to S330. Further, when the ratio r is equal to or less than the set value r, battery consumption is notified in the same manner as in S338.
[0051]
Returning to the description of FIG. 12, the CPU 56 returns or sends the written data in units of pages when the page return button 33, the page feed button 34 and the delete button 35 are pressed. Page processing such as erasure is performed (S400). Further, the CPU 56 takes in switching signals generated by the operation of various buttons (FIG. 1) provided on the operation unit 30 via the I / F circuit 57 (FIG. 10), and acquires the position coordinate data stored in the RAM 59. A page process such as sending or returning the page to be stored, or deleting the position coordinate data in page units is executed (S400). Further, the CPU 56 executes a data output process for converting the position coordinate data of the target page out of the position coordinate data stored in the RAM 59 into an appropriate format and outputting it to the PC 100 or the printer 200 (FIG. 2) ( S500).
[0052]
Furthermore, the CPU 56 operates the audio circuit 31a based on switching signals generated when various buttons are pressed, and executes an audio output process for generating operation sounds such as “Peep” and “Pip” from the speaker 31. (S600). Further, the CPU 56 calculates the wiping locus of the eraser 40 based on the voltage generated in the X coil and the Y coil by the alternating magnetic field generated from the coil built in the eraser 40, and the position coordinate data in the calculated wiping locus is stored in the RAM 59. The eraser process for erasing from FIG. 10 is executed (S700).
[0053]
As described above, if the electronic blackboard 1 according to the first embodiment is used, the second and third sense coils adjacent to both sides of the first sense coil that has generated the maximum voltage have the smaller voltage. A ratio r between the voltage f generated in the first sense coil when the voltage generated in the sense coil becomes 0 and the reference signal level g is calculated, and the DFF in the position coordinate table 58a is multiplied by the ratio r. Thus, the position coordinate table 58a can be corrected.
Therefore, even when the battery 70 of the pen 60 is consumed and the strength of the alternating magnetic field is reduced, the position coordinate table 58a can be corrected according to the degree of the reduction, so that the accurate position of the pen 60 can be corrected. Coordinates can be read.
Moreover, as shown in FIG. 8, there are always two null points that are the timing for correcting the position coordinate table 58a during the distance d1 in which the pen 60 moves from the center line of the sense coil to the next center line. The number of points where correction can be performed can be increased by a factor of two compared to the conventional method in which correction is performed based on the maximum value in which only one exists during the distance d1.
Therefore, since the uncorrected interval can be shortened, the coordinate reading accuracy can be increased.
[0054]
Moreover, since each null point is substantially equal intervals, a coordinate can be correct | amended at equal timing. The correction timing is a timing at which the voltage generated in the third sense coil becomes smaller than a predetermined voltage, but the predetermined voltage is a value larger than the level of noise generated in the electronic blackboard 1 ( For example, it is desirable to set to 10 to 20 mV). As a result, it is possible to prevent a situation where the correction timing is lost due to the influence of noise.
[0055]
[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIG.
The electronic blackboard according to the second embodiment is characterized in that the position coordinates read in the past can be retroactively corrected.
FIG. 14 is a flowchart showing a part of the coordinate reading process executed by the CPU 56 provided in the electronic blackboard of the second embodiment with a part thereof omitted. In the following second and third embodiments, the processing executed by the CPU 56 other than the coordinate reading processing and the other configurations are the same as those of the electronic blackboard of the first embodiment described above. Only the flow of the coordinate reading process will be described. Moreover, the same code | symbol is used about the same structure as the electronic blackboard of 1st Embodiment.
[0056]
When the CPU 56 scans the X coil (S302) and detects the pen 60 (S304: Yes), it corrects the position coordinate table 58a from the process of storing the detected value of each X coil in the temporary storage area 59a (S306). ~ S338). When the CPU 56 detects that the pen 60 has moved away from the writing surface 21a (S304: No), if the detected value of the X coordinate is stored in the temporary storage area 59a (S350: Yes), it is stored in the work area. Referring to the corrected position coordinate table 58a, ΔX corresponding to the stored detection value is extracted, and the X coordinate is calculated by the above-described method using ΔX or the like (S352). Subsequently, the CPU 56 moves the calculated X coordinate to the confirmed area 59b (FIG. 11B) of the RAM 59 (S354).
[0057]
Thereafter, while the pen 60 is in contact with the writing surface 21a, the CPU 56 executes S302 to S338 to store the detected values and correct the position coordinate table 58a, and when the pen 60 leaves the writing surface 21a. The cycle of calculating the X coordinate by executing S350 to S354 is repeated. The Y coordinate is also obtained by executing the same process as the X coordinate.
As described above, if the electronic blackboard according to the second embodiment is used, the coordinates input before the pen 60 moves away from the writing surface 21a, particularly the detection value before v2 = 0 can be corrected, so that the entire reading is performed. Accuracy can be increased.
[0058]
[Third Embodiment]
Next, a third embodiment of the present invention will be described with reference to FIG.
The electronic blackboard according to the third embodiment is characterized in that the position coordinate table 58a is not updated when a predetermined time has not elapsed since the previous correction timing even when the correction timing is reached.
FIG. 15 is a flowchart showing a flow of coordinate reading processing executed by the CPU 56 provided in the electronic blackboard of the third embodiment.
[0059]
If the CPU 56 determines that the second voltage v2 is 0 (S322: Yes), the measurement time of a timer (for example, a timer built in the CPU 56) that measures the elapsed time from the timing when the position coordinate table 58a was corrected previously. When T is equal to or longer than the preset time T1 preset in the ROM 58 or the like (S324: Yes), the position coordinate table 58a is corrected (S326 to S330). Subsequently, the CPU 56 resets the timer (S332) and restarts the timer (S334). Subsequently, when the ratio r calculated in S328 is equal to or less than the set value r1 (S336: Yes), the CPU 56 notifies battery consumption (S338), and calculates the X coordinate based on the corrected position coordinate table 58a (S338). S340). If the measurement time T is not equal to or longer than the set time T1 (S324: No), the X coordinate is calculated without correcting the position coordinate table 58a (S340). The Y coordinate is obtained by executing the same process as the X coordinate.
In the third embodiment, the set time T1 can be set in seconds, minutes, or hours. In addition, once the position coordinate table 58a is corrected, the same position coordinate table 58a can be used until the power of the electronic blackboard 1 is cut off.
[0060]
As described above, the CPU 56 does not perform the operation of reloading and updating the position coordinate table 58a when the set time T1 or more has not elapsed since the previous correction timing even when the correction timing is reached. On the other hand, when the value of the timer has exceeded the set time T1, the process of updating the position coordinate table 58a as described above is performed, and the timer is reset again and restarted.
Therefore, wasteful consumption of CPU power used for updating the position coordinate table 58a can be prevented.
[0061]
In each of the above-described embodiments, the second adjacent to the first sense coil that has generated the maximum signal level. 2 And second 3 Signal level f generated in the first sense coil when the signal level generated in the third sense coil having the smaller signal level is lower than the predetermined signal level, Although the ratio with the reference value g was calculated, the signal level f generated in the second sense coil and the reference value g (When the battery 70 of the pen 60 is not depleted, the third sense with the smaller signal level out of the second and third sense coils adjacent to the first sense coil that has generated the maximum signal level) The signal level generated in the second sense coil when the signal level generated in the coil is substantially zero) It can also comprise so that ratio with may be calculated. Further, the ratio between the signal level f generated in the first or second sense coil and the reference value g when the signal level generated in the third sense coil having the smaller signal level is the minimum value is calculated. It may be configured.
By the way, the pen 60 corresponds to the coordinate input means of the present invention, the writing surface 21a corresponds to the coordinate input surface, the sense coil 23 corresponds to the loop conductor, the writing sheet 21 corresponds to the coordinate input sheet, and the battery runs out. The notification LED 39 corresponds to the notification means. The reference value g corresponds to the reference signal level.
Further, S310 to S330 executed by the CPU 56 function as the correcting means of the present invention, and S336 and S338 function as the notifying means.
[Brief description of the drawings]
FIG. 1 is an external perspective view illustrating the main configuration of an electronic blackboard according to an embodiment of the present invention.
FIG. 2 is an explanatory diagram showing a state in which a PC and a printer are connected to the electronic blackboard shown in FIG.
FIG. 3 is an explanatory diagram showing in block form the configuration of a network when data communication is performed between the electronic blackboard 1 and another electronic blackboard 1;
FIG. 4 is an explanatory view showing each component of the writing panel body 20;
5A is an explanatory diagram showing a part of the configuration of the sense coil 23 shown in FIG. 5 with part omitted, and FIG. 5B is a width of the sense coil 23 shown in FIG. 5A. It is explanatory drawing which shows an overlap pitch.
6A is an explanatory diagram showing a part of the X coils X1 to X3, and FIG. 6B is a voltage generated in the X coils X1 to X3 shown in FIG. 6A and the width direction. 6C is a graph showing the voltage difference between the adjacent sense coils of the X coils X1 to X3 shown in FIG. 6A.
7A is an explanatory diagram showing the position coordinate table in a graph, FIG. 7B is an explanatory diagram of the position coordinate table, and FIG. 7C is a corrected position coordinate table. It is explanatory drawing of.
FIG. 8 is an explanatory diagram showing the correspondence between the movement of the pen 60 and the voltage generated in the sense coil.
9A is an explanatory diagram showing an internal structure of the pen 60, and FIG. 9B is an explanatory diagram showing an electrical configuration of the pen 60 shown in FIG. 9A.
FIG. 10 is an explanatory diagram showing the electrical configuration of the electronic blackboard 1 in blocks.
FIG. 11A is an explanatory diagram showing a voltage value and a voltage drop when it is time to correct the position coordinate table 58a. FIG. 11B is a part of the contents stored in the RAM 59. FIG. 11C is an explanatory diagram showing a state in which the detection value detected from each X coil by scanning is stored in the temporary storage area 59a of the RAM 59 in association with the coil number.
12 is a flowchart showing main control contents by a CPU 56 shown in FIG. 10;
13 is a flowchart showing the flow of coordinate reading processing executed by the CPU 56 in S300 of FIG. 12 in the first embodiment.
14 is a flowchart showing a flow of coordinate reading processing executed by the CPU 56 in S300 of FIG. 12 in the second embodiment.
FIG. 15 is a flowchart showing a flow of coordinate reading processing executed by a CPU in S300 of FIG. 12 in the third embodiment.
FIG. 16A is an explanatory diagram showing a configuration of a conventional coordinate reading apparatus, and FIG. 16B is an explanatory diagram showing a decrease in coordinate reading accuracy, and FIG. These are graphs showing the relationship between the voltage generated in the sense coil and the position of the pen.
[Explanation of symbols]
1 Electronic blackboard (coordinate reader)
21 Writing sheet (coordinate input sheet)
21a Writing surface (coordinate input surface)
23 Sense coil (loop conductor)
30 Operation unit
39 Battery low notification LED (notification means)
56 CPU
58a Position coordinate table
60 pen (coordinate input means)

Claims (7)

A coordinate input sheet having a coordinate input surface for inputting coordinates by a coordinate input means for generating an alternating magnetic field, and a plurality of loop conductors laid under the coordinate input surface, the alternating force generated from the coordinate input means In a coordinate reader that detects a signal level generated in the loop-shaped conductor by a magnetic field and reads the coordinates of the coordinate input means on the coordinate input surface based on the detected signal level,
Of the second and third loop conductors adjacent to the first loop conductor that generates the maximum signal level, the signal level generated in the third loop conductor having the smaller signal level is a predetermined signal level. The signal level generated in one of the first and second loop conductors when the signal level is smaller and the reference set for the one corresponding to the predetermined strength of the alternating magnetic field A coordinate reading apparatus comprising correction means for correcting the coordinates based on a signal level. The correction means includes
Correcting a signal level used for reading the coordinates based on a ratio between a signal level generated in one of the first and second loop conductors and a reference signal level set for the one. The coordinate reader according to claim 1, wherein   3. The coordinate reading apparatus according to claim 1, wherein a signal level smaller than the predetermined signal level of the signal level generated in the third loop-shaped conductor is approximately 0. 4. 4. The predetermined signal level is higher than a level of noise generated in the coordinate reader when the alternating magnetic field is not generated from the coordinate input means. The coordinate reader according to one.   The loop conductor is formed in a horizontally long ring shape, and a center line that bisects one loop conductor of the adjacent loop conductors in the longitudinal direction and the other loop conductor in the longitudinal direction are 2 The signal level generated in the mutually adjacent loop conductors is higher than the signal level generated in the loop conductors other than the mutually adjacent loop conductors in a range surrounded by the center line to be divided. The coordinate reading device according to claim 1, wherein the coordinate reading device is disposed in a position.   The loop conductor is generated in each loop conductor at the boundary where the signal level between the primary peak of the signal level generated in each conductor and the secondary peak appearing at both ends of the primary peak is minimized. The coordinate reading apparatus according to claim 1, wherein the boundaries to be arranged are arranged at substantially equal intervals.   It is characterized by comprising notifying means for notifying that a signal level generated in one of the first and second loop conductors has decreased in response to a decrease in strength of the alternating magnetic field generated from the coordinate input means. The coordinate reading apparatus according to any one of claims 1 to 6.

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