JPH0764698A - Position input device - Google Patents

Abstract

PURPOSE:To simplify the production process, to enable long and stable operation, and to prevent erroneous detection of position information by simplifying the circuit and eliminating the adjustment of a position director. CONSTITUTION:A coordinate pointer 5 is provided with a resonance circuit. The 1st and 2nd scanning circuits successively select the 1st and 2nd sense line groups S1 and S2. When the coordinate pointer 5 comes closer to the sense line group, they and an amplifier 3 make a positive feedback loop circuit and an oscillation signal 101 is generated. A coordinate detection circuit 6 calculates the coordinates when it detects the frequency of the oscillation signal 101 is within the decided range. The amplitude of an input signal 102 which is guided to the 2nd sense line group S2 by the oscillation is provided with the specified position information of the coordinate pointer. The coordinate detection circuit 6 inputs it to calculate the specified position.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position input device for inputting position information to electronic equipment such as a computer, and more particularly to a wireless position input device to which an electromagnetic induction phenomenon is applied.

[0002]

2. Description of the Related Art FIG. 10 is a block diagram of a conventional coordinate reading device which is a kind of position input device. The operation of calculating the coordinates of the conventional coordinate reading device will be described based on this figure.
The excitation line 903 and the sense line 902 are laid orthogonally to each other, and each of them is connected to the first scanning circuit 908 and the second scanning circuit 909 so as to be sequentially selected. The first scanning circuit 908 receives the excitation signal s from the excitation circuit 915.
Since 906 is supplied, the excitation line selected by the first scanning circuit 908 generates an alternating magnetic field. Since the coordinate indicator 906 has a resonance circuit (not shown) that resonates at the frequency of the excitation signal s906, when this is placed on the sense line, the excitation line 903, the coordinate indicator 906, and the sense line 902 are combined. An induction signal s901 is generated on the sense line 902 due to the coupling between them. The induction signal s901 is sequentially selected by the second scanning circuit 909, and is guided to the signal processing circuit 904 to be sent to the amplitude signal s90.
5, and this signal is input to the coordinate detection circuit 905. The coordinate detection circuit 905 determines that a specific signal in the amplitude signal s905 is at a certain level or higher, and calculates the coordinates from the distribution state of the amplitude signal s905 when this condition is satisfied.

[0003]

However, in the conventional coordinate reading apparatus of such a system, it is necessary to constantly generate an alternating magnetic field of a predetermined frequency from the exciting line, so that a dedicated exciting circuit is required. Was needed. Further, since the resonance frequency of the resonance circuit of the coordinate indicator needs to be adjusted to the vicinity of the frequency of the AC magnetic field generated by the exciting circuit, it is necessary to adjust the coordinate indicator by providing a trimmer capacitor, which reduces the manufacturing cost. It was one of the factors that raised it. Also, maintaining a stable resonant frequency for a long period of time has been a difficult task. Further, even if the coordinate indicator is not present on the sense line, the excitation line and the sense line may be directly coupled with each other, and a certain level of induction signal may be generated on the sense line. The coordinate detection circuit is adapted to detect the fact that the amplitude of the induction signal has become equal to or higher than a certain level to calculate the coordinates, so that the coordinates may be erroneously calculated even in such a case.

As described above, the conventional coordinate reader has problems to be solved in terms of circuit scale, manufacturing cost, product stability, and the like. The present invention has been made to solve the above problems, and a first object of the present invention is not to rely on a conventional method of exciting a resonant circuit by a reference signal such as an exciting signal and detecting its response, but to an exciting circuit. It is an object of the present invention to provide a position input device that eliminates the above and simplifies the circuit.

A second object of the present invention is to provide a position input device which can be stably used for a long period of time while reducing the manufacturing cost by eliminating the adjustment of the position indicator. A third object is to provide a position input device which eliminates erroneous position detection by surely detecting the presence of the position indicator on the sense line.

[0006]

In order to solve the above problems, the present invention is provided with first and second coupling means, an amplifier, a position detection circuit, and a position indicator incorporating a resonance circuit. When the resonance circuit of 1 is electromagnetically coupled in the vicinity of the first and second coupling means, the first coupling means, the second coupling means, the amplifier and the resonance circuit form an oscillation circuit by a positive feedback loop. The position input device is configured to generate an oscillation signal and calculate the position of the position indicator when the position detection circuit detects that the oscillation signal has a frequency within a certain range.

[0007]

In the position detecting device having the above structure, no signal is transmitted between these circuits and means when the resonance circuit is not electromagnetically coupled to the first coupling means or the second coupling means or both of them. Since this does not occur, the position detection circuit does not detect the position. However, when the resonance circuit is electromagnetically coupled to the first and second coupling means, a positive feedback loop having the output of the amplifier, the first coupling means, the resonance circuit, the second coupling means, and the input of the amplifier as a series of paths is formed. The oscillation signal is generated by the resonance frequency of the resonance circuit. The position detection circuit can detect whether or not the position indicator exists near the first and second coupling means by determining whether or not the frequency of the oscillation signal is within a certain range. Further, since the amplitude information of oscillation changes according to the feedback amount determined by the distance between the first and second coupling means and the resonance circuit, the position detection circuit inputs this amplitude information and the position information of the position indicator. Can be obtained.

[0008]

First, the basic principle of the present invention will be described with reference to FIG. In the figure, 33 is an amplification circuit, 1 is a first coupling means connected to the output of the amplification circuit 33, and 2 is a second coupling means connected to the input of the amplification circuit 33. 15
Is a position indicator used to indicate the detection position, and is a resonance circuit 4 electromagnetically coupled to both the first and second coupling means.
Built in.

The first coupling means and the second coupling means are not directly coupled to each other when the position indicator 15 is not in close proximity, and are electromagnetically coupled via the resonance circuit 4 when they are in close proximity. Any form may be used as long as it is configured. FIG. 2 shows an example thereof, in which two rectangular sense lines 1a and 2a are laid orthogonally. If these sense lines are sufficiently long in the longitudinal direction, they are orthogonal to each other, so that in principle no direct coupling occurs between them if the position indicators are not close to each other.

When the position indicator 15 is located in the vicinity of the first and second coupling means 1 and 2 and electromagnetic coupling occurs with the resonance circuit 4, the output of the amplifier circuit 33 and the first coupling means 1 are detected. ,
A positive feedback loop is formed with the resonance circuit 4, the second coupling means 2, and the input of the amplifier circuit 33 as a series of paths.
Oscillation occurs at the resonance frequency of. This oscillation phenomenon is excited by noise generated by the amplifier circuit 33, natural noise, etc., and is a known phenomenon.

On the other hand, when the position indicator 15 is located away from the first and second coupling means 1 and 2, and there is no electromagnetic coupling with the resonance circuit 4, there is no feedback and no oscillation occurs. Therefore, the position detection circuit 16 determines that the oscillation signal 101
Is input to detect the frequency information and determine whether or not the frequency information is within a certain frequency range, thereby determining whether the position indicator 15 is close to the first and second coupling means 1 and 2. Can be detected. The frequency range used for the determination may be centered on the resonance frequency of the resonance circuit 4, and a certain width may be provided in consideration of the operation margin of the circuit.

The resonance circuit 4 includes the first and second coupling means 1,
When the frequency approaches 2 and further approaches them, the oscillation frequency does not change, but the amount of feedback changes according to the distance, and the amplitude of the oscillation signal 101 changes. As the distance is shorter, the feedback amount is increased and a large oscillation amplitude is obtained, and as the distance is longer, the feedback amount is reduced and the oscillation amplitude is decreased. In this way, since the oscillation signal 101 having the amplitude corresponding to the position of the position indicator 15 is obtained at the output of the amplifier circuit 33, the position detection circuit 16
The position information can be obtained from the amplitude of the oscillation signal 101.

By the way, the above description is merely a principle, and actually, the first and second coupling means 1, 2 are connected.
The coupling between them cannot be completely zero. For example, FIG. 3 is an example thereof, in which the arrangement of the two sense lines in FIG. 2 is slightly changed. In this case, the folded-back portion 1b ′ of the sense line 1b is different from the other sense line 2b.
It can be understood that some degree of coupling occurs even when the position indicator is not close because it is close to the long side of. As a result, depending on the conditions, even if the position indicators are not close to each other, the oscillation condition may be satisfied and self-oscillation may occur. The oscillation frequency at this time follows the feedback characteristic of the positive feedback loop configured in this state, and it was observed that it was a frequency of several MHz. On the other hand, the resonance frequency of the resonance circuit is selected to be about several hundred kHz. It is possible to design the two separately.

As described above, the position detecting circuit 16 of the position input device according to the present invention first checks the frequency of the oscillation signal 101, and if it is within a predetermined range, the position indicator 15 causes the position indicator 15 to detect the first and second frequencies. It is determined that the position information is close to the coupling means 1 and 2 of 1. Therefore, even if the self-oscillation as described above occurs, it can be identified, so that the position is not erroneously detected.

Next, a first embodiment of a coordinate reading device which is a practical position input device according to the present invention will be described with reference to FIGS. 4 to 9. FIG. 4 is a configuration diagram thereof. In the figure, S1 is a first sense line group having sense lines y1 to yn. Each sense line is a coil having a rectangular shape, the long sides of which are parallel to the X axis of the XY orthogonal coordinate axes and are laid at equal intervals in the Y axis direction. 1
Reference numeral 1 is a first scanning circuit for sequentially selecting the first sense line group S1. S2 is a second sense line group having sense lines x1 to xm. These are the first
Has the same shape as the sense line group S1 and is laid orthogonal to them. Reference numeral 21 is a second scanning circuit for sequentially selecting these second sense line groups S2.

Reference numeral 3 is an amplification circuit having a variable amplification degree, the input of which is connected to the second scanning circuit 21 and the output of which is connected to the first scanning circuit 11. This amplifier circuit 3 has a VCA whose amplification degree can be changed from the outside (for example, TL026 manufactured by TI).
It can be realized by a known one such as.

Reference numeral 7 is an AGC for controlling the amplification degree of the amplifier circuit 3.
Circuit. The oscillation signal 101 output from the amplifier circuit 3 is input, a control signal 103 is given to the amplifier circuit 3 based on the amplitude of this signal, and the amplification degree is controlled. Reference numeral 6 denotes a coordinate detection circuit having the same function as the position detection circuit 16, which selects the first and second scanning circuits 11 and 21 and also receives the input signal 1 from the second scanning circuit 21.
02 and the oscillation signal 101 from the amplifier circuit 3, and the coordinate value is calculated based on this. The coordinate detection device main body is configured by the above circuits.

On the other hand, 5 is a coordinate indicator having the same function as the position indicator 15, and has a resonance circuit (not shown) including a coil. This is used to indicate the coordinate reading position on the main body of the coordinate detecting device. FIG. 5 shows a configuration diagram of the first scanning circuit 11. The first scanning circuit 11 includes a plurality of electronic switches 211 to 21n such as analog switches.
And a decoder 201, and one circuit of the switch is closed by a selection signal 104 output from the coordinate detection circuit 6, and one of the first sense line group S1 is connected to the output of the amplification circuit 3. There is. Although details of the second scanning circuit 21 are not shown, the first scanning circuit 11 is not shown.
The configuration is the same as that of the above, except that it is connected to the input of the amplifier circuit 3.

FIG. 6 shows a configuration diagram of the coordinate detection circuit 6. First, 66 is a control circuit configured by a general CPU circuit. 61 is a rectifier circuit, 62 is a smoothing circuit, and 63 is an A / D.
This is a conversion circuit, which detects the input signal 102 guided from the second scanning circuit 21, converts it into an envelope signal, further converts the magnitude thereof into a digital signal, and outputs it to the control circuit 66. Further, 64 is a waveform shaping circuit, and 65 is a frequency counter circuit, which shapes the oscillation signal 101 into a rectangular wave and then counts it and outputs it to the control circuit 66 as frequency information. The control circuit 66 determines the coordinate indicator 5 based on these signals.
Detects the proximity to the sense line and calculates the coordinates.

FIG. 7 shows a block diagram of the AGC circuit 7. In the figure, 71 is a rectifying circuit, 72 is an integrating circuit, 73 is a comparing circuit, and 74 is an amplitude setting circuit. The oscillation signal 101 is rectified by the rectification circuit 71, integrated by the integration circuit 72, compared with the amplitude setting value set by the amplitude setting circuit 74 by the comparison circuit 73, and output to the amplification circuit 3 as the control signal 103. The control signal 103 controls the amplifier circuit 3 so that the amplitude of the oscillation signal 101 is constant at the amplitude set by the amplitude setting circuit 74.

Next, the operation of this embodiment will be described. FIG. 8 and FIG. 9 are an explanatory diagram for the waveform diagram of the oscillation signal and the coordinate calculation. The first scanning circuit 11 first selects the sense line y1 of the first sense line group S1 according to the selection signal 104 output from the coordinate detection circuit 6. This operation will be described with reference to FIG. 5. The decoder 201 turns on the analog switch 211 by the selection signal 104,
The output of the amplifier circuit 3 is connected to the first sense line y1. On the other hand, the second scanning circuit 21 sequentially selects the second sense line group S2 as x1, x2 ... xm by the selection signal 105 output from the coordinate detection circuit 6 during this period.

When the scanning of the second sense line group is completed, the first scanning circuit 11 then selects the sense line y2 of the first sense line group S1, and the second scanning circuit 21 Similarly to the previous time, set the second sense line group S2 to x1,
x2 ... xm are sequentially selected.

This scanning is repeated in the same manner, and finally, the first scanning circuit 11 selects the sense line yn of the first sense line group S1, and the second scanning circuit 21 receives the second sense line group in the meantime. S2 is sequentially selected as x1, x2 ... xm. When the coordinate indicator 5 is placed in the vicinity of the intersection region of the two selected sense lines in each of the first and second sense line groups in the process of such scanning, as described in the basic principle, A positive feedback loop using the output of the amplifier circuit 3, the first scanning circuit 11, the sense line Yi, the resonance circuit of the coordinate indicator 5, the sense line Xj, the second scanning circuit 21, and the input of the amplifier circuit 3 as a series of paths. Is generated, and oscillation occurs at the resonance frequency of the resonance circuit.

The AGC circuit 7 generates the generated oscillation signal 101.
Is input to the amplifier circuit 3 as a control signal 103, and the oscillation signal 101 is controlled to have a constant amplitude. In this way, the oscillation is stabilized by the control by the AGC circuit 7, and the amplitude of the oscillation signal 101 becomes constant even if the position of the resonance circuit changes.

Focusing on the input signal 102 of the amplifier circuit 3, the amplitude of this signal changes depending on the distance between the intersection area of the selected sense lines and the coordinate indicator 5. When the coordinate indicator is placed right above the intersection area, a signal with the largest amplitude is obtained, and the amplitude decreases as the distance increases. Therefore, the input signal 102
By paying attention to the amplitude of, the position of the coordinate indicator 5 can be obtained.

The coordinate detection circuit 6 generates the oscillation signal 1 obtained by sequentially selecting each sense line as described above.
From 01, it is first detected whether the coordinate indicator 5 is present on the sense line group. The frequency information of the oscillation signal 101 is obtained by the frequency counter circuit 65 shown in FIG. 6 and input to the control circuit 66. The oscillation frequency of the normal positive feedback loop by the coordinate indicator 5 and the frequency band considering the margin are stored in advance in the control circuit 66, so the control circuit 66 should compare the frequency information with these values. Then, it is determined whether the coordinate indicator 5 is present on the sense line group.

If the detected frequency information is not within the stored frequency range, it is determined that abnormal oscillation has occurred, and the subsequent coordinate calculation operation is stopped. If detected correctly, the next coordinate calculation operation is continued. Next, details of the distribution of the amplitude of the input signal 102 will be described with reference to FIG. 8, and the description of the coordinate calculation method will be given.
FIG. 8 is a waveform diagram when the coordinate indicator 5 is located in the portion A of FIG. 4, and shows the selection signal 104 input to the first scanning circuit 11 and the selection signal input to the second scanning circuit 21. Signal 10
5 and the oscillation signal (the signal 151 in FIG. 6) before being AD-converted in the coordinate detection circuit 6.

Symbol a is an oscillation signal immediately below the section A, that is, when the first sense line y4 and the second sense line x4 are selected and is the largest signal generated during scanning. This is the first sense line y4 and the second sense line y4.
This is because the sense line x4 and the sense line x4 are both the closest to the coordinate indicator 5 and thus have the largest degree of coupling with the resonance circuit, and hence the largest feedback amount.

B and c are on the left and right of the section A, that is, when the first sense line y4 and the second sense line x3 are selected, and the first sense line y4 and the second sense line x5 are selected. Is the oscillation signal. In this case, the resonance circuit of the coordinate indicator 5 and the first sense line y4
Have the same coupling degree, but the distance between the resonance circuit and the second sense line is large, the oscillation signal b and the oscillation signal c
Is smaller than the oscillation signal a.

Further, d and e are above and below the section A, that is, when the first sense line y3 and the second sense line x4 are selected, and when the first sense line y5 and the second sense line x4 are selected. This is the oscillation signal when In this case, the degree of coupling between the resonance circuit of the coordinate indicator 5 and the second sense line x4 is the same, but the distance between the resonance circuit and the first sense line is large, so that the oscillation signal d and the oscillation signal e are increased. The magnitude is smaller than the oscillation signal a.

Although the oscillation signals a to e have been described above, the position of the sense line selected from the first sense line group S1 and the second sense line group S2 and the coordinate indicator 5 for other signals as well. The size is determined by the positional relationship of. Next, paying attention to the above five oscillation signals a to e,
A method of calculating coordinates will be described in detail.

First, a method of calculating the X coordinate will be described focusing on the oscillation signals a, b and c. FIG. 9 (1) is an enlarged view of the periphery of the portion A shown in FIG.
Sense line x4 and sense line x5 from the center L0 of 4
Consider the case of moving to the middle L1 of. 9 (2) and 9 (3) show oscillation signals a, b, and c when the coordinate indicator 5 is located at L0 and L1.

First, the case where the coordinate indicator 5 is located at L0 will be described. As described above, the oscillation signal a is the signal when the sense line y4 and the sense line x4 are selected, the oscillation signal b is the sense line y4 and the sense line x3, and the oscillation signal c is the signal when the sense line y4 and the sense line x5 are selected. is there. At this time, the oscillation signal a has the largest value, and the oscillation signals b and c are the same as the coordinate indicator 5 and the sense line x.
Since the distance of 3 and the distance of the coordinate indicator 5 and the sense line x5 are the same, they are equal.

Next, the case where the coordinate indicator 5 is located at L1 will be described. At this time, the oscillation signals a and c are equal because the distance between the coordinate indicator 5 and the sense line x4 and the distance between the coordinate indicator 5 and the sense line x5 are the same. Here, the method proposed by the present applicant (Japanese Patent Laid-Open No. 55-96411).
No.) can be applied to calculate the coordinates. That is, the calculation defined by the following equation is performed based on the oscillation signal.

Q = (V _p −V _{p + 1} ) / (V _p −V _p-1 ) equation-1 where V _{p + 1} > V _{p-1 In the} above equation, the oscillation signal a is oscillated to V _p. Signal b is Vp-1
Substitute the oscillation signal c into Vp + 1 and set the coordinate indicator 5 to L0.
FIG. 9 (4) shows the change in Q shown in Expression-1 when moving from Q to L1. When the coordinate indicator 5 is at the position L0, Q = 1, and when the coordinate indicator 5 is at the position L1, Q = 1.
It is clear from the above description that = 0. Also,
When the coordinate indicator 5 is located between L0 and L1, Q takes a value in the range of 0 <Q <1 corresponding to this position on a one-to-one basis. Therefore, the characteristic of this Q is experimentally obtained in advance to calculate Q from the oscillation signals a, b, and c, and the detailed position of the coordinate indicator 5 between L0 and L1 on the sense line is calculated from this Q. Can be asked. Further, the X coordinate can be obtained from this Q and the position of the sense line where the oscillation signal a is detected.

The Y coordinate can be considered in the same manner as the X coordinate described above. In FIG. 9A, consider a case where the coordinate indicator 5 moves on the center of the sense line x4 from the center L0 of the sense line y4 to the middle L2 of the sense lines y4 and y5. 9 (5) and 9 (6)
Shows the oscillation signals a, d, and e when the coordinate indicator 5 is located at L0 and L2.

First, the case where the coordinate indicator 5 is located at L0 is as described in the method for calculating the X coordinate. When the coordinate indicator 5 is located at L2, the oscillation signals a and e are equal at this time because the distance between the coordinate indicator 5 and the sense line y4 and the distance between the coordinate indicator 5 and the sense line y5 are the same.

Therefore, the characteristic of Q when the coordinate indicator 5 is moved from L0 to L2 as in the case of the above-mentioned X coordinate is as shown in FIG. 9 (7). Similar to the case of the X coordinate, the Y coordinate can be obtained by using the characteristic of Q. As described above, the coordinate detection circuit 6 determines whether the frequency of the oscillation signal 101 is in the correct range and calculates the coordinates only when the frequency is in the correct range. Therefore, self-oscillation occurs. However, the coordinates are not calculated by mistake.

The present invention is characterized in that whether or not to perform coordinate calculation is controlled based on the result of determination that the oscillation signal is in the correct frequency range. Although the AGC circuit is provided in order to obtain a stable oscillation signal in the present embodiment, the present invention can be applied without using the AGC circuit, for example, by clipping the amplitude of the oscillation signal. Further, depending on how the frequency determination result is used, it is possible to realize a coordinate reader having a configuration and operation different from those of the first embodiment.

As a second embodiment, a coordinate reading apparatus having the same configuration as that of FIG. 4 but having different operations will be briefly described. In this type of scanning-type coordinate reading device, the presence of a coordinate indicator is detected to increase the coordinate calculation rate, that is, the number of times of coordinate calculation per time (for example, about 200 points / sec is a general specification). Up to the above, all the sense lines are scanned, and after detecting the presence, only a few peripheral sense lines designated by the coordinate indicator are scanned. Here, the former will be referred to as “entire scanning” and the latter will be referred to as “partial scanning”.

At this time, a technical problem is how to detect the presence of the coordinate indicator during the entire scanning. This will be described with reference to FIG. 10. In the conventional general method, detection is performed from the amplitude information of the oscillation signal s901. That is, as described above, since the amplitude of the oscillation signal depends on the distance between the coordinate indicator 5 and the selected sense line, if the amplitude is detected to exceed a certain value, the coordinate indicator is indicated. It can be determined that the container 5 is present.

It will be appreciated that the present invention can also be applied for such purposes. That is, in the present invention, the presence of the coordinate indicator 5 is determined by the frequency information of the oscillation signal 101. At this time, in order to detect the frequency information, it is sufficient to have a waveform shaping circuit and a means for measuring the frequency as shown in FIG. 6, so that the frequency information can be obtained in a short time by devising the means for measuring the frequency. You can
Therefore, if applied to such a purpose, there is a new effect that scanning can be performed at high speed. If it is attempted to detect the amplitude information as in the conventional case, a circuit having a certain delay must be used in order to obtain the envelope signal of the oscillation signal, so that the scanning cannot be speeded up.

[0043]

As described above, according to the present invention, the oscillation signal related to the position of the position indicator can be obtained by the simple structure of inserting the resonance circuit of the position indicator in the positive feedback loop of the amplifier circuit. Then, the position input device is configured to calculate the position information from this. Therefore, the excitation circuit is not required and the circuit can be simplified.

Further, since the resonance frequency can be arbitrarily set, the position indicator can be adjusted and the manufacturing process can be simplified. Further, even if the resonance frequency fluctuates, it does not affect the position information calculation, so that it is possible to realize a stable position input device for a long term.

Furthermore, since the position information is calculated only when the frequency of the oscillation signal is within a predetermined range, a position input device that does not erroneously calculate position information due to self-oscillation or the like is realized. I was able to.

[Brief description of drawings]

FIG. 1 is a principle configuration diagram for explaining the principle of a coordinate input device of the present invention.

FIG. 2 is an explanatory diagram showing first and second coupling means in the principle configuration of the coordinate input device of the present invention.

FIG. 3 is an explanatory diagram showing an example of the arrangement of first and second coupling means in the principle configuration of the coordinate input device of the present invention.

FIG. 4 is a configuration diagram of a first embodiment of a coordinate reading device according to the present invention.

FIG. 5 is a configuration diagram of a first scanning circuit of the first embodiment of the coordinate input device according to the present invention.

FIG. 6 is a configuration diagram of a coordinate detection circuit of a first embodiment of the coordinate input device of the present invention.

FIG. 7 is an AGC of the first embodiment of the coordinate input device of the present invention.
It is a block diagram of a circuit.

FIG. 8 is a distribution diagram of oscillation signals in the first embodiment of the coordinate input device of the present invention.

FIG. 9 is an explanatory diagram for calculating coordinates in the first embodiment of the coordinate input device according to the present invention.

FIG. 10 is a configuration diagram of a conventional coordinate reading device.

[Explanation of symbols]

1 1st coupling means 2 2nd coupling means 3 Amplification circuit 4 Resonance circuit 5 Coordinate indicator 6 Coordinate detection circuit 15 Position indicator 66 Position detection circuit 7 AGC circuit 11 First scanning circuit 21 Second scanning circuit 33 Amplifier circuit 61 Rectifier circuit 62 Smoothing circuit 63 A / D conversion circuit 64 Waveform shaping circuit 65 Frequency counter circuit 66 Control circuit 71 Rectifier circuit 72 Integrator circuit 73 Comparison circuit 74 Amplitude setting circuit 101 Oscillation signal 102 Input signal 103 Control signal 104, 105 Selection signal S1 First sense line group S2 Second sense line group y1, y2, y3, y4 to yn-1, yn First sense line x1, x2, x3, x4 to xm-1, xm Second Above the sense line

Claims (1)

[Claims] 1. A position indicator having an amplifier circuit, first coupling means connected to the output of the amplifier circuit, second coupling means connected to the input of the amplifier circuit, a position detection circuit, and a resonance circuit. By means of electromagnetically coupling the resonant circuit with both the first and second coupling means,
The resonance circuit, the amplifier circuit, and the first and second coupling means constitute an oscillation circuit by a positive feedback loop, and the position detection circuit is configured so that the oscillation signal generated by the oscillation circuit is in a constant frequency range. A position input device configured to obtain position information of the position indicator from amplitude information of the oscillation signal when it is determined that there is the condition and it is detected that the condition is satisfied.