JPH08255051A - Coordinate reader - Google Patents

Abstract

PURPOSE: To provide a coordinate reader which eliminates the need to connect a coordinate indicator and a coordinate detection main body by a signal line and does not deteriorate in periphery precision. CONSTITUTION: This reader consists of plural excitation lines including an excitation line 101, plural detection lines including a detection line 102, an exciting circuit 2, a signal processing circuit 3, a control circuit 4, the coordinate indicator 5 including a resonance circuit 6, a selecting circuit 7 which selects an excitation line and a detection line, and a phase detecting circuit 8; when the coordinate indicator is put close to the excitation line and detection line, an induction signal s13 is induced. The phase detecting circuit detects the phase difference between the excitation signal and induction signal and if the phase difference is not within a specific range, it is judged that the coordinate indicator is positioned outside a readable range to stop coordinate calculation, but when the phase difference is within the specific range, the coordinate calculation is performed on the basis of the amplitude distribution of the induction signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coordinate reader for inputting coordinate information to an external device such as a computer, and more particularly to a wireless coordinate system which does not require a signal line to connect between the coordinate detecting device body and the coordinate indicator. The present invention relates to a reading device.

[0002]

2. Description of the Related Art FIG. 17 is a block diagram of a conventional coordinate reading device. The operation of detecting the position of the conventional coordinate reading device will be described with reference to FIG. Excitation line 911
The excitation line group typified by 1 and the detection line group typified by the detection line 912 are laid orthogonally to each other and are connected to the selection circuit 907 to sequentially select. Excitation line 91
An excitation signal s902 is supplied to 1 from the excitation circuit 902 via the selection circuit 907, and an alternating magnetic field is generated from the excitation line selected by the selection circuit 907. Coordinate indicator 905
Has a resonance circuit 906 composed of a coil and a capacitor so as to resonate at the frequency of the excitation signal. Therefore, when this is brought close to the detection line, electromagnetic coupling occurs between the excitation line, the resonance circuit, and the detection line. An induction signal s903 is generated on the detection line. This induction signal is used to select circuit 9
08, the signal is sequentially selected and guided to the signal processing circuit 903 to be the amplitude information s904 of the induction signal. Further, the amplitude information of the induction signal is input to the control circuit 904 to generate the induction signal s90.
The coordinates are calculated from the amplitude distribution of 3.

The coordinates are calculated only when the maximum value of the amplitude of the guidance signal is equal to or larger than the threshold value for starting the calculation of the coordinates. A coordinate calculation method for calculating the position of the coordinate indicator from the amplitude distribution of the guidance signal will be described with reference to FIGS. It should be noted that only the coordinate calculation method for calculating the position of the coordinate indicator in the x direction will be described here, and the y direction coordinate calculation method is the same as that in the x direction, and therefore description thereof is omitted.

FIG. 18 shows detection lines x0 to
Of xn, a part of the detection lines x0 to x4 is enlarged. 19 and 20 respectively show a coordinate indicator 905.
Is located on the center L0 of the detection line x2 shown in FIG. 18 and on the position L1 equidistant from the centers of the detection lines x2 and x3, the amplitudes of the induction signals generated on the detection lines x1 to x3. V11 to V13 are shown.

First, the case where the coordinate indicator 905 is located on the center L0 of the detection line x2 shown in FIG. 18 will be described. In this case, when the amplitudes of the induction signals induced in the detection lines x1 to x3 are compared, the amplitude V12 of the induction signal induced in the detection line x2 having the smallest distance from the coordinate indicator 905 becomes maximum as shown in FIG. Coordinate indicator 905
Is located equidistant from the detection lines x1 and x3, the amplitude V1 of the induction signal of the detection lines x1 and x3
1 and V13 are equal.

Next, the case where the coordinate indicator 905 is located on the line L1 equidistant from the centers of the detection lines x2 and x3 shown in FIG. 18 will be described. In this case, as shown in FIG. 20, the amplitudes V12 and V13 of the induction signals of the detection lines x2 and x3 are the same as the distance between the coordinate indicator 905 and the detection line x2 and the distance between the coordinate indicator 905 and the detection line x3. Therefore, they are equal.

Coordinates can be calculated by applying the method proposed by the present applicant (Japanese Patent Laid-Open No. 55-96411). That is, the calculation defined by the following equation is performed based on the amplitude of the induction signal. Q = (Vp -Vp + 1) / (Vp -Vp-1) ( Equation 1) However, in Vp + 1 ≧ Vp-1 the above equation, the V12 to V _p, the V11 to V _p-1, the V13 Substitute in V _{p + 1} and set the coordinate indicator 905 in parallel with the x-axis by L0.
FIG. 21 shows the change in Q shown in (Equation 1) when moving from L1 to L1. When the coordinate indicator 905 is at the position L0, Q = 1, and when the coordinate indicator 905 is at the position L1, Q = 0. Also, when the coordinate indicator is located between L0 and L1, Q is 0 <Q corresponding to this position in a one-to-one correspondence.
It takes a value in the range of <1. Therefore, it is possible to calculate Q from the amplitude of the induction signal and obtain the position of the coordinate indicator between L0 and L1 by calculating the characteristic of this Q in advance experimentally. Therefore,
First, the rough position in the x direction of the coordinate indicator is specified by detecting the position of the detection line where the amplitude of the guidance signal is maximum, and then the detailed position obtained from Q is added / subtracted to determine the x direction. The exact position of can be determined.

[0008]

By the way, in the conventional coordinate reading device, when the coordinate indicator is located outside the coordinate readable range, there are cases where a coordinate greatly different from the indicated position of the coordinate indicator is calculated. It was

In the conventional coordinate reading apparatus, the detection line where the amplitude of the guidance signal is maximum is determined to be the detection line having the shortest distance from the coordinate indicator, and the rough position in the x direction of the coordinate indicator is determined. I had specified. In the actual coordinate reading device, when the coordinate indicator is located outside the coordinate readable range due to the height or position of the coordinate indicator, etc., the distance from the coordinate indicator is smaller than the amplitude of the guide signal of the detection line that is the smallest,
In some cases, the amplitude of the inductive signal generated on the other detection line becomes maximum. As a result, a large error may occur between the indicated position of the coordinate indicator and the coordinate calculated by the control circuit.

FIG. 22 is a diagram for explaining the positional relationship between the coordinate indicator and the excitation and detection lines. FIG. 23 shows detection lines x0 and x1 when the coordinate indicator 905 is located on the center line b3 of the excitation line y0 in FIG.
3 shows an x-direction amplitude distribution of an inductive signal generated in the. From this amplitude distribution, it can be seen that the center line a2 of the detection line x1 shows a first-order peak, and the outer lines a0 and a4 outside the detection line x1 have a second-order peak. The reason for this is that the mutual inductance M between the coil included in the resonance circuit of the coordinate indicator 905 and the detection line changes depending on the position of the coordinate indicator 905, and the mutual inductance M takes a maximum value near a2 and near a0 and a4. This is because it takes a minimum value (the sign is negative and the absolute value is maximum). On the other hand, the distribution of the induced voltage generated in the detection line x0 is almost the same as that of x1 and is moved in the minus direction of the x coordinate as a whole. The distribution of the induced voltage generated in the detection line x0 also has a secondary peak, but it is omitted here because it is not important in the description here. As shown in FIG. 23, when the coordinate indicator 905 is located on a1 slightly outside the detection line x1, the amplitude of the induction signal induced on the detection line x0 having the smallest distance from the coordinate indicator 905 is the detection line. Although it is larger than the amplitude of the induction signal induced in x1, but when located on a0, the induction induced in the detection line x1 is larger than the amplitude of the induction signal induced in the detection line x0 having the smallest distance from the coordinate indicator 905. The signal amplitude increases.

As described above, particularly in the area outside the readable range of the peripheral portion of the coordinate detecting device 901, the amplitude of the induction signal induced in other detection lines is larger than that of the detection line having the shortest distance from the coordinate indicator. However, there is a problem that the difference between the designated position of the coordinate indicator and the coordinate calculated by the control circuit becomes large.

In order to solve the above-mentioned problems, it is necessary to set a high threshold value of the amplitude of the guiding signal for starting the coordinate calculation in the conventional coordinate reading device so that the amplitude of the guiding signal which becomes the secondary peak is not detected. It was However, when the threshold value is set high, there is a problem that the height of the coordinate indicator that can be detected by the coordinate detection device, that is, the readable height is reduced.

In particular, when a pen-shaped coordinate indicator is used, the amplitude distribution of the guidance signal may change greatly depending on the tilt angle of the pen, and the above-mentioned secondary peak may become high. Had to be higher.
As a result, there is a problem that the required readable height of the coordinate indicator cannot be secured.

An object of the present invention is to ensure a coordinate readable height even when the coordinate indicator is located in the peripheral portion of the coordinate detecting device,
Moreover, it is an object of the present invention to provide a coordinate reading device that does not reduce the coordinate detection accuracy.

[0015]

In order to solve the above-mentioned problems, the present invention has, as a first structure, a plurality of excitation lines laid in a loop shape parallel to one axis of an xy rectangular coordinate system. , A plurality of detection lines laid in a loop shape parallel to the other axis of the xy rectangular coordinate system and the plurality of excitation lines, and one excitation line is sequentially selected from the plurality of excitation lines. A first selection circuit, a second selection circuit connected to the plurality of detection lines and sequentially selecting one detection line from the plurality of detection lines, and the first selection circuit for the plurality of excitation lines. An excitation circuit that supplies an excitation signal via the coordinate indicator, a coordinate indicator that includes a resonance circuit that uses the frequency of the excitation signal as a resonance frequency, and an induction signal that induces in the plurality of detection lines via the second selection circuit. Receiving A signal processing circuit for converting the signal into an amplitude information, a phase detection circuit for detecting a phase difference between the excitation signal and the induction signal, and outputting a detection result to the control circuit, and the first and second selections. While outputting the selection signal to the circuit, when the phase detection circuit determines that the phase difference between the excitation signal and the induction signal is within a preset range, the position calculation of the coordinate indicator is performed by the signal. A control circuit that performs the amplitude information from the processing circuit,
The coordinate reading device is composed of

In order to solve the above problems, the second aspect of the present invention
And a plurality of excitation lines laid in a loop shape parallel to one axis of the xy rectangular coordinate system,
a plurality of detection lines laid in a loop shape parallel to the other axis of the y orthogonal coordinate system and a plurality of excitation lines, and one excitation line is sequentially selected from the plurality of excitation lines One selection circuit, a second selection circuit that is connected to the plurality of detection lines and sequentially selects one detection line from the plurality of detection lines, and the plurality of excitation lines through the first selection circuit. An excitation circuit for supplying an excitation signal, a coordinate indicator including a resonance circuit having the frequency of the excitation signal as a resonance frequency, and an induction signal induced in the plurality of detection lines via the second selection circuit. A signal processing circuit for converting into amplitude information, and at least forming a loop shape in parallel with the plurality of excitation lines,
Is connected to the excitation circuit via the first selection circuit,
The auxiliary excitation line laid so that the induction signal is sufficiently small when the coordinate indicator is located outside the readable range, and a loop shape is formed in parallel with the plurality of detection lines, and the second selection circuit Connected to the signal processing circuit via, the auxiliary detection line laid so that the guidance signal is sufficiently small when the coordinate indicator is located outside the readable range, and one of the lines, The first
And outputting a selection signal to the second selection circuit,
Control for calculating the position of the coordinate indicator based on the amplitude information from the signal processing circuit when the amplitude information of the induction signal obtained by selecting the auxiliary excitation line or the auxiliary detection line exceeds a preset threshold value The coordinate reading device is composed of a circuit.

In order to solve the above problems, a third aspect of the present invention is provided.
In the configuration, an amplifier circuit, a plurality of first sense lines laid in a loop shape parallel to one of the xy rectangular coordinate axes, and a loop shape parallel to the other axis of the xy rectangular coordinate axes are formed. It is connected to the plurality of laid second sense lines and the plurality of first sense lines, and one sense line is sequentially selected from the plurality of first sense lines and connected to the output of the amplifier circuit. A second selection circuit that is connected to a first selection circuit and the plurality of second sense lines, and sequentially selects one sense line from the plurality of second sense lines and connects it to the input of the amplifier circuit. A coordinate indicator including a resonance circuit and an input or output of the amplifier circuit, and when the resonance circuit is close to the first and second sense lines and electromagnetically coupled to the sense line, An amplifier circuit, the resonance circuit, a signal processing circuit that obtains amplitude information from an oscillation signal that the first and second sense lines form a positive feedback loop and oscillates at the resonance frequency of the resonance circuit; 1
Forming a loop shape in parallel with the sense line, is connected to the output of the amplifier circuit through the first selection circuit, and the oscillation signal is sufficiently small when the coordinate indicator is located outside the readable range. Forming a loop shape in parallel with the plurality of first auxiliary sense lines and the plurality of second sense lines, which are connected to the input of the amplifier circuit via the second selection circuit, A plurality of second auxiliary sense lines laid so that the oscillation signal is sufficiently small when the coordinate indicator is located outside the readable range;
Amplitude information of the oscillation signal when a selection signal is output to either one of the lines and the first and second selection circuits, and the first auxiliary sense line or the second auxiliary sense line is selected. When the value exceeds a preset threshold value, the coordinate reading device is configured by a control circuit that receives the output signal of the signal processing circuit and calculates the position of the coordinate indicator.

In order to solve the above problems, the fourth aspect of the present invention
In addition to the above-mentioned third configuration,
And a second sense line and at least one of the first and second assisting sense lines include a differential sense line in which two loops are connected to each other in opposite windings. The coordinate reading device is provided with a phase switching circuit at the output or input of the amplification circuit so that the positive feedback loop is established regardless of which of the two loops the coordinate indicator approaches.

[0019]

According to the first configuration of the present invention, the phase detection circuit detects the phase difference between the excitation signal and the induction signal induced in the detection line, and outputs it to the control circuit as phase information. When the coordinate indicator is located outside the readable range around the coordinate detection device, the phase difference differs by about 180 degrees from when it is located within the readable range. Therefore, when the phase difference exceeds the predetermined range, the control circuit stops the coordinate calculation based on the phase information from the phase detection circuit. Therefore, it is possible to output the accurate position of the coordinate indicator.

Further, according to the second aspect of the present invention, when the coordinate indicator is located outside the readable range, the auxiliary excitation line or auxiliary detection line is formed so that the induction signal becomes sufficiently small. If the induction signal detected when the auxiliary excitation line or the auxiliary detection line is selected is sufficiently small, the coordinate calculation is stopped. Therefore, it is possible to output the accurate position of the coordinate indicator.

Further, according to the third aspect of the present invention, when the coordinate indicator is located outside the readable range, the first or second signal is generated so that the signal generated in the positive feedback loop becomes sufficiently small.
Since the auxiliary sense line is laid, the coordinate calculation is stopped if the signal generated in the positive feedback loop is sufficiently small when the first or second auxiliary sense line is selected by the selection circuit. Therefore, it is possible to output the accurate position of the coordinate indicator.

Further, according to the fourth configuration of the present invention, the phase condition for the positive feedback loop to be established in the phase switching circuit is 0 degree and 1 phase.
Properly switch to two states of 80 degrees, 2 of differential sense line
Even in a coordinate reading device with a special configuration configured so that the positive feedback loop is established even when the coordinate indicator approaches any one of the two loops, if the coordinate indicator is located outside the readable range, positive feedback is performed. Since the first or second auxiliary sense line is laid so that the signal generated in the loop is sufficiently small, it occurs in the positive feedback loop when the first or second auxiliary sense line is selected by the selection circuit. If the signal is sufficiently small, the coordinate calculation is stopped. Therefore,
It is possible to output the exact position of the coordinate indicator.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A coordinate reading device according to the present invention will be described below with reference to the drawings. FIG. 1 shows a first coordinate reading apparatus according to the present invention.
It is explanatory drawing which showed the structure of. The coordinate detection device 1 includes an excitation circuit 2, a signal processing circuit 3, a control circuit 4, selection circuits 71 and 72, a phase detection circuit 8, and an excitation line 10.
It is composed of a plurality of excitation lines including 1 and a plurality of detection lines including a detection line 102.

The excitation circuit 2 supplies an excitation signal s12 to the excitation line according to the excitation control signal s11 output from the control circuit 4. As shown in FIG. 2, the signal processing circuit 3 includes an amplifier circuit 9, a rectifying circuit 10, a smoothing circuit 11, and an A / D.
The inductive signal s13 that is formed by the conversion circuit 12 and induces in the plurality of detection lines that have been input is amplified, rectified,
The signal is smoothed, digitized by an A / D conversion circuit, and output as amplitude information s14 of the induction signal.

The control circuit 4 controls the amplitude information s14 of the induction signal.
Has a function of calculating the position of the coordinate indicator 5 based on
Further, it also has a function of controlling the excitation circuit 2 and the selection circuits 71 and 72. The coordinate indicator 5 includes a resonance circuit 6 including a coil and a capacitor inside.

The selection circuit 71 selects one from a plurality of excitation lines.
One excitation line is selected and connected to the excitation circuit, and the selection circuit 72 has a function of selecting one detection line from a plurality of detection lines and connecting it to the signal processing circuit 3 and the phase detection circuit 8. The phase detection circuit 8 detects the phase difference between the excitation signal s12 and the induction signal s13, and outputs it as the phase information s15 to the control circuit 4.

Next, the structure of the excitation line and the detection line will be described with reference to FIG. The excitation line 101 forms a substantially rectangular loop, and one end thereof is connected to the excitation circuit 2 via the selection circuit 71 (see FIG. 1). The detection line 102 forms a substantially rectangular loop, and one end thereof is connected to the signal processing circuit 3 via the selection circuit 72 (see FIG. 1).

Next, the operation of the first configuration of the present invention will be described. First, the excitation signal s12 is output from the excitation circuit 2 in response to the excitation control signal s11 output from the control circuit 4. When the selection signal s16 is output so as to select the exciting line 101, an alternating magnetic field is generated from the exciting line 101.

When the coordinate indicator 5 is sufficiently separated from the excitation line 101 and the detection line 102, the excitation line 10
1 and the detection line 102 and the resonance circuit 6 of the coordinate indicator 5 are not electromagnetically coupled to each other, and the induction signal s13 is not induced in the detection line 102. Next, the coordinate indicator 5 is brought close to the excitation line 101 and the detection line 102, and the control circuit 4
When the selection signal s17 is output so as to select the detection line 102, the resonance circuit 6 in the coordinate indicator is configured to resonate with the alternating magnetic field, and thus the excitation line 10
1, the detection line 102 and the resonance circuit 6 are electromagnetically coupled to each other, and the induction signal s13 is induced in the detection line 102. The induction signal s13 is guided to the signal processing circuit 3 and output as amplitude information s14 of the induction signal to the control circuit 4.
Here, the selection signals s16 and s17 from the control circuit 4 are sequentially changed so that the selection circuits 71 and 72 sequentially select the excitation line and the detection line to thereby induce the induction signal s1.
An amplitude distribution of 3 can be obtained.

The above operation is basically the same as that of the conventional coordinate reading device. Next, the operation of detecting the phase difference between the excitation signal and the induction signal and determining whether or not the coordinate indicator is located within the readable range based on the phase difference will be described. The excitation line and the detection line having the maximum amplitude are selected from the amplitude distribution of the induction signal s13, and the phase detection circuit 8 detects the phase difference between the excitation signal s12 and the induction signal s13. As described above, the phase difference when the coordinate indicator is located outside the readable range is about 180 degrees different from when it is located within the readable range. 1 is output as information and the coordinate calculation is stopped. If the phase difference is within a predetermined range, 0 is output as the phase information to start the coordinate calculation, the coordinate is calculated from the amplitude distribution of the induction signal, and the coordinate is output. The coordinate calculation method has been described in the conventional example, and thus the description thereof is omitted.

Next, the process of detecting the excitation signal and the induction signal and determining whether or not the coordinate indicator is located outside the readable range will be described in detail with reference to FIGS. FIG.
FIG. 3 is a diagram showing a positional relationship between a position of a coordinate indicator 5 (see FIG. 1) and an excitation line and a detection line. FIG. 4 is a diagram showing the amplitude distribution in the x direction of the induction signals generated in the detection lines x0 and x1 with respect to the position of the coordinate indicator 5. Figure 5
FIG. 6 is an explanatory diagram showing states of an excitation signal s12 and a detected induction signal s13.

The amplitude distribution of FIG. 4 is the first when the coordinate indicator 5 moves on the line b3 of FIG. 3 (the center line of the excitation line y0).
3 shows the inductive signal generated in the detection lines x0 to x4. From FIG. 4, when the coordinate indicator 5 exists near a0, which is outside the readable range, the amplitude of the detection line x1 is larger than the amplitude of the induction signal of the detection line x0 having the smallest distance from the coordinate indicator 5. You can see that it has become.

Next, the phase difference between the excitation signal and the induction signal will be compared depending on the position of the coordinate indicator. Figure 5 shows the excitation signal
(A), FIG. 5 (b) shows the guidance signal generated on the detection line x1 when the coordinate indicator is present near a2 (the center line of the detection line x1), and when the coordinate indicator 5 is present near a0. The induction signal generated in the detection line x1 is shown in FIG. From FIG. 5, the guidance signal in the case where the coordinate indicator exists in a0 outside the readable range [FIG. 5 (c)] is the same as the guidance signal in the case where the coordinate indicator exists in the readable range [FIG. 5 (b)]. It can be seen that the phases differ by about 180 degrees. Therefore, by detecting the phase difference between the excitation signal s12 and the induction signal s13, it is possible to determine whether or not the coordinate indicator 5 is located outside the readable range. For example, the phase detection circuit 8
Then, the phase difference between the excitation signal s12 and the induction signal s13 is compared. When the phase difference between the excitation signal s12 and the induction signal s13 is close to 0 degree, the phase information s15 is output as 0, and the phase difference becomes 180 degrees. When it is set to output the phase information s15 as 1 when it is close, when the phase information s15 is 1, it is determined that the coordinate indicator 5 exists outside the readable range, and the coordinate calculation is stopped.

Next, the second configuration of the coordinate reading device of the present invention will be described. FIG. 6 shows a second embodiment of the coordinate reading device of the present invention.
It is explanatory drawing which showed the structure of. First, the configuration of the coordinate reading device will be described with reference to FIG. The description of the same operation as the first configuration is omitted.

The coordinate detecting device 1a includes an exciting circuit 2, a signal processing circuit 3, a control circuit 4a, and selecting circuits 71 and 7.
2, a plurality of excitation lines including an excitation line 101, a plurality of detection lines including a detection line 102, and a plurality of auxiliary detection lines including an auxiliary detection line 103. The auxiliary detection line 103 is added to the first configuration, the phase detection circuit 8 is deleted, and the contents of the control circuit 4a are slightly changed accordingly.

The coordinate indicator 5 having the resonance circuit 6 has the same structure as the first structure. The output of the excitation circuit 2 is supplied to one excitation line selected by the selection circuit 71, the coordinate indicator 5 receives the magnetic field emitted from the excitation line, and one detection line selected by the selection circuit 72 is the coordinate system. Indicator 5
The signal processing circuit 3 receives this magnetic field and converts this induction signal into amplitude information s14. The control circuit 4a calculates the position of the coordinate indicator 5 based on the amplitude information s14.

Next, the structure of the excitation line including the excitation line 101, the detection line including the detection line 102, and the auxiliary detection line including the auxiliary detection line 103 will be described with reference to FIG.
It will be described in detail based on. The excitation line 101 and the detection line 102 have the same configuration as the first configuration (FIG. 3). The auxiliary detection line typified by the auxiliary detection line 103 forms a substantially rectangular loop, and one end of the auxiliary detection line 103 is connected to the signal processing circuit 3 (see FIG. 6) via the selection circuit 72, similarly to the detection line 102.
And the coordinate indicator 5 is located outside the readable range, the guidance signal s13 generated on the auxiliary detection line
Is laid so that the amplitude of is sufficiently smaller than the threshold for starting coordinate calculation.

In FIG. 7, the auxiliary detection line 103 has a width substantially equal to that of the detection line 102, and the length thereof is set to be vertically short. The optimum value of this difference in length varies depending on the characteristics of the coordinate indicator 5, but a good result is obtained with one sense line. (While the detection line 102 has a length including y0 to y4, the auxiliary detection line 103 has a length from y1 to y4.
The length is set to include y3. However, when the shape of the coordinate indicator 5 is extremely changed, it is necessary to make a considerably different setting.

The width of the auxiliary detection line 103 does not have to be the same as that of the detection line 102, and it is better to make it a little wider. Further, the width can be set to two or three detection lines to reduce the number of auxiliary detection lines. (In FIG. 7, since there are two auxiliary detection lines, it is impossible to further reduce them, but auxiliary detection lines corresponding to the detection lines x1 and x3 may be provided.) Next, the operation of the coordinate reading device will be described. .

The calculation of coordinates by the excitation line 101 and the detection line 102, which is the basic operation, is omitted since it is the same as in the first configuration, and the process of determining whether or not the coordinate indicator is located outside the readable range will be described. It will be described in detail based on 7-10. Here, in order to simplify the description, the case where the coordinate indicator is located on a3 which is the center of the detection line x0 will be described (see FIGS. 7 and 8).

FIG. 8 shows the coordinate indicator 5 and the excitation lines y0-.
The positional relationship between y4, the detection line x0, and the auxiliary detection line x0 'is shown. FIG. 9 is a flowchart for explaining the operation of outputting the coordinates after obtaining the amplitude distribution of the induction signal.

FIG. 10 shows the y-direction amplitude distribution of the induction signal induced in the detection line x0 [FIG. 10 (a)] and the induction signal induced in the auxiliary detection line x0 'when the excitation lines y0 to y4 are selected. Amplitude distribution in the y direction [Fig. 10 (b)]
Indicates. The coordinate indicator is a3 which is the center of the detection line x0.
Since it is located above, the maximum induction signal is obtained at the detection line x0 in the x direction. On the other hand, in the y direction, the guidance signal s13
It is necessary to obtain the excitation line yk having the maximum amplitude from the amplitude distribution of. If the amplitude of the induction signal s13 when the excitation line yk is selected is equal to or smaller than the threshold value Vth for starting the coordinate calculation, the coordinate calculation is stopped. The amplitude of the induction signal s13 is greater than or equal to the threshold value Vth for starting coordinate calculation, and the excitation line y
Excitation line y1 or y3 when k is y1 or y3
And the auxiliary detection line x0 'are selected and the induction signal s13 is detected. When the amplitude of the induction signal s13 is equal to or more than the threshold value Vth, the coordinates are calculated from the amplitude distribution of the induction signal s13 by a normal calculation. When the excitation line having the maximum amplitude is y1 or y3 and the amplitude of the induction signal s13 induced on the auxiliary detection line x0 'is less than the threshold value Vth, the coordinate calculation is set to be stopped.

When the amplitude of the induction signal s13 when the first detection line x0 is selected is equal to or greater than the threshold value Vth and the excitation line having the maximum amplitude is other than y1 and y3, the induction signal s13 is calculated by normal calculation. The coordinates are obtained from the amplitude distribution of. The difference in voltage induced between the detection line x0 and the auxiliary detection line x0 'will be described in detail with reference to FIG. Since the detection line x0 has a length including the excitation lines y0 to y4, its induced voltage has almost the same shape as that of the excitation lines y0 to y4, and the peak position of the induced voltage varies depending on the position of each excitation line. y
Is shifting in the direction. However, there is a secondary peak of y1 on the negative side in the y direction from the peak of the excitation line y0,
There is a secondary peak of y3 on the plus side in the y direction from the peak of the excitation line y4, and these secondary peaks pose a problem.
There are also secondary peaks of the excitation lines y0, y2, y4, but they are omitted here for simplicity. Excitation line y0
When the coordinate indicator 5 is located at the position of b2 which is the center of the excitation line, the induction signal corresponding to the excitation line y0 is the excitation line y1.
Since it is larger than the induction signal corresponding to, the coordinate can be calculated normally, but when the coordinate indicator 5 is located at a position b0 slightly above and outside the excitation line y0, the excitation line y1 is set to a position closer to the excitation line y0 than the induction signal corresponding to the excitation line y0. Since the corresponding guidance signal is larger, an error occurs in coordinate calculation.

On the other hand, the auxiliary detection line x0 'is the excitation line y.
Since it has a length including 1 to y3, the induced voltage has almost the same shape for the excitation lines y1 to y3, but the induced voltage for the excitation lines y0 and y4 is lower than the others. Further, the secondary peak on the minus side in the y direction corresponding to the excitation line y1 is greatly reduced because the position of b0 is outside the auxiliary detection line x0 '. Similarly, the secondary peak on the plus side in the y direction corresponding to the excitation line y3 also decreases.

Therefore, when the coordinate indicator 5 is located at the position b0, the induced voltage obtained by the combination of the detection line x0 and the excitation line y1 is changed by the combination of the auxiliary detection line x0 'and the excitation line y1. The resulting induced voltage is low enough to be easily identified. In this way, the coordinate indicator 5
Is determined to be outside the readable range, and when the coordinate indicator 5 is located outside the readable range, the coordinate calculation is stopped, and the coordinate indicated by the coordinate indicator 5 and the coordinate calculated by the control circuit are stopped. Can be prevented from increasing.

In general, the coordinate indicator 5 also moves in the x direction, so that the maximum value of the induction signal is not limited to the y direction of the excitation line but the detection line x as shown in the flowchart of FIG.
It is also necessary to select the line in the direction. In this case, the auxiliary detection lines may be provided not only at x0 'but also auxiliary detection lines x1' to x4 'corresponding to the detection lines x1 to x4 (not shown in FIGS. 7 and 8). Corresponding to this, in FIG. 9, the excitation line yk and the detection line xi having the maximum amplitude are obtained,
After checking the amplitude (comparison with the threshold value Vth), it is checked whether k is 1 or 3, and if k is 1 or 3, the auxiliary detection line xi 'is checked.

As described above, by laying the auxiliary detection lines x0 'to x4' so that the guidance signal induced when the coordinate indicator is located outside the readable range is sufficiently small, the auxiliary detection line x0 is laid out. Since the coordinate calculation is stopped when the guidance signal induced in'˜x4 'does not exceed the threshold value Vth, the difference between the designated position of the coordinate indicator 5 and the calculated coordinate may become large as described above. Absent.

In the second embodiment described above, the auxiliary detection line is laid in order to simplify the description, but it is laid near the excitation line and the coordinate indicator is located outside the readable range. In this case, when the auxiliary excitation line formed so that the induction signal is sufficiently small is laid, the same effect as that of the present embodiment can be obtained. further,
It is also possible to lay both the auxiliary detection line and the auxiliary excitation line.

The second structure described above is an example of the present invention, and limits the length, width, number of loops, winding number of each loop, and laying interval of the auxiliary excitation line and the auxiliary detection line. Not something to do. In addition, a threshold for amplitude determination may be separately provided for the detection line and the auxiliary detection line.

The first and second configurations described above are examples of the present invention. The length and width of the excitation line and the detection line, the number of loops, the number of turns of each loop,
It does not limit the laying interval. The second configuration can also be applied to the first configuration having a phase detection circuit by providing an auxiliary detection line or an auxiliary excitation line, and the phase determination by the phase detection circuit of the first configuration and the second configuration By combining the auxiliary detection line or the auxiliary excitation line having the above configuration, more effective malfunction prevention can be achieved.

Next, a description will be given of a third configuration in which the present invention is applied to a coordinate reading device of a system different from the coordinate reading device shown in the first and second configurations. FIG. 11 is an explanatory diagram showing a third configuration of the coordinate reading device of the present invention. The coordinate detection device 1b includes a signal processing circuit 3, a control circuit 4b, selection circuits 71 and 72, and an amplification circuit 9b. The signal processing circuit 3, the control circuit 4b, and the selection circuits 71 and 72 have basically the same functions as the circuits of the first and second configurations,
An amplifier circuit 9 is used instead of the exciting circuit 2 of the second configuration (FIG. 6).
b is used.

The coordinate indicator 5 has the same structure as the first and second configurations. One ends of the plurality of first sense lines represented by the first sense line 201 are connected to the output of the amplifier circuit 9b via the selection circuit 71. One ends of the plurality of second sense lines represented by the second sense line 202 are connected to the input of the amplifier circuit 9b and the signal processing circuit 3 via the selection circuit 72. Further, a plurality of auxiliary sense lines represented by the auxiliary sense line 203 are laid in parallel with the plurality of second sense lines, one end of which is similar to the second sense line 202 via the selection circuit 72 and an amplifier circuit. It is connected to the input of 9b and the signal processing circuit 3.

The above plurality of first sense lines, second sense lines, and auxiliary sense lines have the same configurations as the excitation line, the detection line, and the auxiliary detection line shown in FIG. 7, respectively. Next, the operation of this third configuration will be described.

First, when the coordinate indicator 5 is separated from the first sense line 201 and the second sense line 202, the first sense line 201, the resonance circuit 6 of the coordinate indicator 5 and the second sense line. There is no electromagnetic coupling between the two in 202. Therefore, no feedback occurs between the input and output of the amplifier circuit 9b, and no oscillation occurs. Next, the coordinate indicator 5 approaches the first sense line 201 and the second sense line 202, the control circuit 4b outputs the selection signals s25 and s26, and these signals cause the selection circuits 71 and 72 to move to the first position. When the first sense line 201 and the second sense line 202 are selected, the resonance circuit 6 is electromagnetically coupled to the first sense line 201 and the second sense line 202, and the output of the amplifier circuit 9b and the first sense line are detected. 201, the resonance circuit 6, the second sense line 202, a positive feedback loop using the inputs of the amplifier circuit 9b as a series of paths is formed, and the resonance circuit 6
Output signal s21, input signal s2
2 occurs.

Output signal s21 appearing in this positive feedback loop
The amplitude of the input signal s22 changes according to the distance between the coordinate indicator 5 and the first sense line 201 and the second sense line 202. The input signal s22 is converted into amplitude information s24 by the signal processing circuit 3 and taken into the control circuit 4b. Here, the selection signals s25 and s26 from the control circuit 4b are sequentially changed to select the selection circuits 71, 7
By sequentially selecting the first sense line and the second sense line at 2, the amplitude distribution of the input signal s22 can be obtained, and the coordinates of the coordinate indicator 5 are calculated from this amplitude distribution.

Next, a process of determining whether or not the coordinate indicator is located outside the readable range will be described. Basically, the process is the same as that of the second configuration, and therefore a brief description will be given. The control circuit 4b obtains the first sense line and the second sense line having the maximum amplitude from the amplitude distribution of the input signal s22. In this case, the amplitude is equal to or larger than the threshold value Vth for starting the coordinate calculation, and the first sense line is the second from the substrate end (the excitation line shown in FIG. 7 is y1 or y3 in terms of the second configuration). In the case of, the selection signal s26 by the control circuit 4b
And an auxiliary sense line corresponding to the second sense line having the maximum amplitude in the selection circuit 72 (in the case of the second configuration, the auxiliary detection line xi ′ corresponding to the detection line xi in FIG. 9). Is selected to obtain the amplitude information s24 of the input signal. When the amplitude information s24 of the auxiliary sense line is equal to or larger than the threshold value Vth, the coordinates indicated by the coordinate indicator 5 are calculated from the amplitude distribution of the input signal, and when the amplitude information s24 is smaller than the threshold value Vth, the coordinate calculation is stopped. Set. When the first sense line having the maximum amplitude is other than the second one from the substrate end, the coordinates are calculated from the amplitude distribution of the input signal s22 and the coordinates are output. With this, when the coordinate indicator 5 is located outside the readable range, the coordinate calculation is stopped, so that the difference between the indicated position of the coordinate indicator and the calculated coordinate does not become large.

Since the coordinate calculation method is the same as the method shown in the conventional example, the description thereof is omitted here. In the third configuration described above, the auxiliary sense line is laid in the vicinity of the second sense line in order to simplify the description, but it is laid in the vicinity of the first sense line and outside the readable range. The contents of the present embodiment can be applied by using an auxiliary sense line formed so that the input signal becomes sufficiently small when the coordinate indicator is located.

The third configuration described above is an example of the present invention, and does not limit the length, width, number of turns, laying interval, and number of the first and second sense lines. . Next, a fourth configuration of the coordinate reading device according to the present invention will be described.

FIG. 12 is an explanatory view showing the fourth configuration of the coordinate reading device of the present invention. The coordinate detection device 1c includes a signal processing circuit 3, a control circuit 4c, selection circuits 71 and 72,
It is composed of an amplifier circuit 9b and a phase switching circuit 13. The signal processing circuit 3, the control circuit 4c, and the selection circuits 71 and 72 have basically the same functions as those of the third configuration.
The sense line configuration is different from that of the above configuration, and a phase switching circuit 13 is added. .

The coordinate indicator 5 has the same structure as the first, second and third configurations. As shown in FIG. 13, the phase switching circuit 13 includes a phase switching switch 14 and a phase inverting circuit 15, and according to the phase switching signal s27 output from the control circuit 4c, the phase difference between the output signal s21 and the oscillation signal s23 is calculated. It has the function of switching to the in-phase or anti-phase state.

The structure of the sense lines will be described in detail with reference to FIG. 14, but the first and second sense lines and the auxiliary sense line are similar to those of the second and third structures, and therefore will be briefly described. One end of the plurality of first sense lines typified by the first sense line 201 (corresponding to y1) has a selection circuit 7
1. It is connected to the output of the amplifier circuit 9b via the phase switching circuit 13 (see FIG. 12).

Second sense line 202 (corresponding to x3)
One end of the plurality of second sense lines typified by 1 is connected to the input of the amplifier circuit 9b and the signal processing circuit 3 via the selection circuit 72 (see FIG. 12). Auxiliary sense line 20
A plurality of auxiliary sense lines typified by 3 (omitted in FIG. 14) are connected to the input of the amplifier circuit 9b and the signal processing circuit 3 via the selection circuit 72 at one end similarly to the second sense line 202. The auxiliary sense line 203 is the second and third
Similar to the configuration described above, the longitudinal direction is shorter than the second sense line 202.

The first differential sense line 204 (y0 + y
(Corresponding to 4) is located outside the first sense line 201, has two rectangular loops, and is laid so that the directions of the two loops are opposite to each other. Further, one end has a selection circuit 71, similar to the first sense line 201.
It is connected to the output of the amplifier circuit 9b via the phase switching circuit 13.

The second differential sense line 205 (x0 + x
(Corresponding to 4) is located outside the second sense line 202, has two rectangular loops, and is laid so that the directions of the two loops are opposite to each other. Further, one end is connected to the input of the amplifier circuit 9b and the signal processing circuit 3 via the selection circuit 72, similarly to the second sense line 202.

The third differential sense line 206 (x0 '+ x
(Corresponding to 4 ') is located outside the auxiliary sense line 203,
It has two loops having the same shape as the auxiliary sense line 203, and is laid so that the directions of the two loops are opposite to each other. In addition, one end is the second sense line 20.
Similar to 2, the input of the amplifier circuit 9b is connected to the signal processing circuit 3 via the selection circuit 72.

FIG. 15 shows the first differential sense line 20.
FIG. 4 is a diagram extracted and drawn for easy understanding of the relationship between the fourth differential sense line 205, the second differential sense line 205, and the third differential sense line 206. Next, the operation of the fourth embodiment will be described. The operations of the first and second sense lines and the auxiliary sense line are almost the same as those of the third configuration, and therefore will be briefly described.

The selection circuit 71 selects one of the plurality of first sense lines or the first differential sense line in response to the selection signal s25 from the control circuit 4c and connects it to the phase switching circuit 13. The phase switching circuit 13 switches the phase according to the phase switching signal s27 shown in FIG. 16 from the control circuit 4c. In other words, when a plurality of first sense lines are selected, they are in the same phase (s27 = 0), and when a first differential sense line is selected, the y0 side or y4 side is sensed. Switch to in-phase or anti-phase. At this time, since y0 and y4 are connected in series as one loop, the selection circuit 71, not the selection circuit 71, selects y0 or y4.

The selection of the plurality of second sense lines or the second differential sense lines is similarly performed. By these operations, one sense line can be sequentially selected, and the coordinates can be calculated by obtaining the amplitude distribution of the input signal s22. The control circuit 4c obtains the x-direction and y-direction sense lines having the maximum amplitude from the amplitude distribution of the input signal s22. When the maximum amplitude is equal to or larger than the threshold value Vth for starting the coordinate calculation and the sense line having the maximum amplitude is the second line from the substrate end, that is, y1 or y3 shown in FIG. 14, the maximum amplitude x
The auxiliary sense line or the third differential sense line is selected corresponding to the direction sense line to detect the amplitude of the input signal s22. The subsequent operation is similar to that of the third configuration, and will be omitted.

It is possible to determine whether or not the coordinate indicator 5 is located outside the readable range by the above operation. If it is determined that the coordinate indicator 5 is located outside the readable range, the coordinate calculation is stopped. The difference between the calculated coordinates does not increase. Note that the coordinate calculation method is the same as the method shown in the conventional example, and a description thereof will be omitted.

The fourth configuration described above is an example of the present invention, and is the length, width, and number of turns of the first and second sense lines and the first and second differential sense lines. ,
The laying interval and the number of lines are not limited. For example, FIG.
1 instead of the first differential sense line (y0 and y4) and the second differential sense line (x0 and x4) shown in FIG.
The first and second sense lines having one loop shape may be laid, or conversely, the first sense line (y1 ~
Instead of y3) and the second sense lines (x1 to x3), a plurality of first and second differential sense lines may be laid.

Also, regarding the second differential sense line, the number of turns, the laying interval, and the number of turns are not particularly limited. Further, in the fourth configuration described above, an auxiliary sense line is laid in the vicinity of the second sense line and a third differential sense line is laid in order to simplify the description.
The auxiliary sense line and the first sense line, which are located near the first sense line and have a shortened shape of the first sense line so that the input signal becomes sufficiently small when the coordinate indicator is located outside the readable range. Even if a differential sense line having a shortened shape of the differential sense line is laid, the contents of this embodiment can be applied.

Although the phase switching circuit is used in the fourth configuration shown above, it is sufficient to have means for switching the phase between the inverted state and the non-inverted state. It is also possible to switch the phase by switching to the non-inverting amplification state.

In the third and fourth configurations, the coordinates are calculated from the amplitude distribution of the input signal, but the coordinates can be calculated by detecting the amplitudes of other signals generated in the positive feedback loop. Is. For example, the coordinates can be calculated from the amplitude distribution of the output signal s21 and the oscillation signal s23.

In the coordinate reading device having the third and fourth configurations, an AGC circuit for controlling the amplification degree of the amplifier circuit is provided in the coordinate detecting device main body, and the position of the coordinate indicator is determined from the control signal output from the AGC circuit. It may be configured to calculate. In the coordinate reading device having the first to fourth configurations, the resonance circuit in the coordinate indicator is composed of a coil and a capacitor, but a state setting means is provided in the coordinate indicator to detect the state. The detection means may be provided on the coordinate detection device side. For example, an element that is provided in the coordinate indicator and that changes in inductance, capacitance, impedance, etc. according to the state of pressure or the like acting on the coordinate indicator is provided.
By changing the resonance frequency or the phase of the resonance circuit, the signal processing circuit or the phase detection circuit on the coordinate detection device side can detect the change in the state of the coordinate indicator from the change in the resonance frequency or the phase. Further, a means for detecting the state of the coordinate indicator by detecting a signal that changes according to the inclination or height of the coordinate indicator may be provided on the coordinate detection device side.

Further, in the coordinate reading device having the first to fourth configurations, the number of excitation lines, detection lines and sense lines can be arbitrarily increased or decreased depending on the detectable range. Therefore, in the present invention, there is no limitation on the detectable range, and it is obvious that the invention can be widely applied from a coordinate reading device called a small tablet to a coordinate reading device called a large digitizer.

[0076]

As described above, according to the present invention, when the coordinate indicator is located outside the readable range of the peripheral portion of the coordinate detecting device, the coordinate calculation is stopped, so that the peripheral portion is Also in the above, it is possible to provide a coordinate reading device that accurately calculates coordinates.

[Brief description of drawings]

FIG. 1 is a diagram showing a first configuration of a coordinate reading device according to the present invention.

FIG. 2 is a configuration diagram of a signal processing circuit.

FIG. 3 is a configuration diagram of an excitation line and a detection line in the first configuration.

FIG. 4 is a diagram showing an amplitude distribution of an induction signal of a detection line in the first configuration.

FIG. 5 is a waveform diagram of an excitation signal and a detection line induction signal in the first configuration.

FIG. 6 is a diagram showing a second configuration of the coordinate reading device according to the present invention.

FIG. 7 is a diagram showing the configurations of an excitation line, a detection line, and an auxiliary detection line in the second configuration, and first and second sense lines and an auxiliary sense line in the third configuration.

FIG. 8 is a configuration diagram of an excitation line, a detection line, and an auxiliary detection line in the second configuration.

FIG. 9 is a flowchart illustrating an operation in the second configuration.

FIG. 10 is a diagram showing an amplitude distribution of an induction signal when an excitation line in the second configuration is selected.

FIG. 11 is a diagram showing a third configuration of the coordinate reading device according to the present invention.

FIG. 12 is a diagram showing a fourth configuration of the coordinate reading device according to the present invention.

FIG. 13 is a configuration diagram of a phase switching circuit in a fourth configuration.

FIG. 14 is a configuration diagram of first and second sense lines, auxiliary sense lines, and first, second, and third differential sense lines in a fourth configuration.

FIG. 15 is a configuration diagram of first, second and third differential sense lines in a fourth configuration.

FIG. 16 is a diagram showing the relationship between the first and second sense lines and the first and second differential sense lines selected by the selection circuit and the phase switching signal.

FIG. 17 is a diagram showing a configuration of a conventional coordinate reading device.

FIG. 18 is an explanatory diagram showing a positional relationship between a coordinate indicator, an excitation line, and a detection line in a conventional coordinate reading device.

FIG. 19 is a diagram showing the amplitude of the guidance signal detected when the coordinate indicator is located at L0 in the conventional coordinate reading device.

FIG. 20 is a diagram showing the amplitude of the guidance signal detected when the coordinate indicator is located at L1 in the conventional coordinate reading device.

FIG. 21 is a diagram showing a conventional coordinate reading device in which L0 to L1 are used.
It is a figure which shows Q calculated from the amplitude distribution of an induction signal, when a coordinate indicator is located between.

FIG. 22 is an explanatory diagram showing a positional relationship between a coordinate indicator, an excitation line, and a detection line in a conventional coordinate reading device.

FIG. 23 is a distribution diagram showing the amplitude of the guidance signal detected when the coordinate indicator is located on the line b3 in the conventional coordinate reading device.

[Explanation of symbols]

 1, 1a, 1b, 1c Coordinate detection device 2 Excitation circuit 3 Signal processing circuit 4, 4a, 4b, 4c Control circuit 5 Coordinate indicator 6 Resonance circuit 8 Phase detection circuit 9, 9b Amplification circuit 10 Rectification circuit 11 Smoothing circuit 12 A / D conversion circuit 13 Phase switching circuit 14 Phase switching switch 15 Phase inversion circuit 71, 72 Selection circuit 101 Excitation line 102 Detection line 103 Auxiliary detection line 201 First sense line 202 Second sense line 203 Auxiliary sense line 204 First Differential sense line 205 Second differential sense line 206 Third differential sense line 901 Coordinate detection device 902 Excitation circuit 903 Signal processing circuit 904 Control circuit 905 Coordinate indicator 906 Resonance circuit 907 Selection circuit 911 Excitation line 912 Detection Line s11, s901 Excitation control signal s12, s902 Excitation signal s13, s903 Induction signal s14, s904 Induction signal amplitude information s15 Phase information s16, s17, s25, s26, Selection signal s21 Output signal s22 Input signal s23 Oscillation signal s24 Input signal amplitude information s27 Phase switching signal

Claims (4)

[Claims] 1. A plurality of excitation lines laid in a loop shape parallel to one axis of an xy rectangular coordinate system, and a plurality of excitation lines laid in a loop shape parallel to the other axis of the xy rectangular coordinate system. A plurality of detection lines, a first selection circuit connected to the plurality of excitation lines and sequentially selecting one excitation line from the plurality of excitation lines, and a plurality of detection lines connected to the plurality of detection lines A second selection circuit for sequentially selecting one detection line from the above, an excitation circuit for supplying an excitation signal to the plurality of excitation lines via the first selection circuit, and a frequency of the excitation signal as a resonance frequency. A coordinate indicator including a resonance circuit, a signal processing circuit that receives an induction signal induced in the plurality of detection lines via the second selection circuit and converts the induction signal into amplitude information, the excitation signal and the induction A phase detection circuit that detects a phase difference with the signal and outputs a detection result to the control circuit; and a selection signal that is output to the first and second selection circuits, and the phase detection circuit outputs the excitation signal and the excitation signal. And a control circuit that calculates the position of the coordinate indicator based on the amplitude information from the signal processing circuit when it is determined that the phase difference from the induction signal is within a preset range. And coordinate reading device. 2. A plurality of excitation lines laid in a loop shape parallel to one axis of an xy rectangular coordinate system, and a loop shape laid in parallel to the other axis of the xy rectangular coordinate system. A plurality of detection lines, a first selection circuit connected to the plurality of excitation lines and sequentially selecting one excitation line from the plurality of excitation lines, and a plurality of detection lines connected to the plurality of detection lines A second selection circuit that sequentially selects one detection line from among the lines; an excitation circuit that supplies an excitation signal to the plurality of excitation lines via the first selection circuit; and a frequency of the excitation signal as a resonance frequency. A coordinate indicator including a resonance circuit, and a signal processing circuit that receives an induction signal induced in the plurality of detection lines via the second selection circuit and converts the induction signal into amplitude information, at least the plurality of A loop shape is formed in parallel with the excitation line and is connected to the excitation circuit via the first selection circuit so that the induction signal is sufficiently small when the coordinate indicator is located outside the readable range. And an auxiliary excitation line formed into a loop shape parallel to the plurality of detection lines and connected to the signal processing circuit via the second selection circuit,
Any one of an auxiliary detection line laid so that the guidance signal is sufficiently small when the coordinate indicator is located outside the readable range, and is selected by the first and second selection circuits. When outputting the signal, and when the amplitude information of the induction signal obtained by selecting the auxiliary excitation line or the auxiliary detection line exceeds a preset threshold value, the coordinate indicator based on the amplitude information from the signal processing circuit. And a control circuit for calculating the position of the coordinate reading device. 3. An amplifier circuit, a plurality of first sense lines laid in a loop shape parallel to one of the xy rectangular coordinate axes, and a loop shape parallel to the other axis of the xy rectangular coordinate axes. Connected to the plurality of second sense lines and the plurality of first sense lines, and one sense line is sequentially selected from the plurality of first sense lines and connected to the output of the amplifier circuit. And a second selection circuit that is connected to the plurality of second sense lines, sequentially selects one sense line from the plurality of second sense lines, and connects the sense line to an input of the amplifier circuit. A circuit, a coordinate indicator including a resonance circuit, and an input or output of the amplification circuit, and when the resonance circuit approaches the first and second sense lines and is electromagnetically coupled to the sense line, A signal processing circuit that obtains amplitude information from an oscillation signal that the amplification circuit, the resonance circuit, and the first and second sense lines form a positive feedback loop and oscillates at the resonance frequency of the resonance circuit; It forms a loop shape parallel to the first sense line, is connected to the output of the amplifier circuit through the first selection circuit, and the oscillation signal is sufficient when the coordinate indicator is located outside the readable range. A plurality of first auxiliary sense lines laid so as to be small, and a loop shape parallel to the plurality of second sense lines, and connected to the input of the amplifier circuit via the second selection circuit. Any one of a plurality of second auxiliary sense lines laid so that the oscillation signal is sufficiently small when the coordinate indicator is located outside the readable range, When the amplitude information of the oscillation signal exceeds a preset threshold value when the selection signal is output to the first and second selection circuits and the first auxiliary sense line or the second auxiliary sense line is selected. And a control circuit that receives the output signal of the signal processing circuit and calculates the position of the coordinate indicator. 4. The coordinate reading device according to claim 3, wherein at least one of the first and second sense lines and the first and second assisting sense lines has two loops wound in opposite directions. So that the positive feedback loop is established regardless of which of the two loops of the differential sense line the coordinate indicator approaches. Coordinate reading device characterized in that a phase switching circuit is provided at the output or input of the circuit