JP3138346B2 - Position detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a position detecting device using radio waves.

[0002]

Prior to this application, the applicant filed Japanese Patent Application No. Sho 61
No. 213970 (refer to Japanese Patent Application Laid-Open No. 63-70326) (hereinafter referred to as the prior application), radio waves are exchanged between the sensing unit and the position indicator to determine the position indicated by the position indicator. A position detection device for obtaining coordinate values was proposed.

[0003] Briefly explaining the contents of the prior application, a radio wave of a predetermined frequency is transmitted from a loop coil of a sensing unit, and the radio wave is received by a resonance circuit provided in a position indicator. At this time, a radio wave transmitted from the resonance circuit that has received the radio wave is received by the loop coil to generate an induced voltage. This is repeated by sequentially switching a plurality of loop coils of the sense section, and the coordinate value of the designated position is obtained based on the level of the induced voltage generated in each loop coil.

In this type of position detecting device, in addition to the coordinate value of the designated position, information indicating a state where the designated position to be actually input is specified (pen down state), the type of the position indicator, for example, a pen or a cursor. Or information for changing parameters other than coordinate values, such as the thickness of a line, hue and density (brightness) of a designated position or designated region, depending on software, together with the coordinate value of the designated position. There is a request to enter.

In the above-mentioned prior application, by connecting another capacitor to a coil and a capacitor constituting a resonance circuit via a manual switch, the resonance frequency is slightly changed in accordance with an operation on the switch. This slight change in the resonance frequency is detected as a change in the phase angle,
The above-described various types of information (hereinafter, referred to as indicator information) are provided.

However, in the above-described position detecting device, the range of the detectable phase angle is limited to about -60 ° to + 60 °, and the inductance of the coil and the capacitance of the capacitor change due to a change in ambient temperature and the like. Due to the problem that the phase angle at the time of detection must have a certain width, there has been a problem that the number of inputtable indicator information cannot be increased much.

Therefore, the applicant has provided a code generator in the position indicator, and has a coil and a capacitor constituting a resonance circuit through electronic switches in accordance with a binary code of a plurality of bits output from the code generator. By intermittently connecting the other capacitors, the resonance frequency is slightly changed in accordance with the binary code, and the slight change in the resonance frequency in accordance with the binary code is detected as a change in the phase angle. A position detecting device has been proposed which is capable of inputting indicator information corresponding to the number of binary codes of a plurality of bits by reproducing the binary code (Japanese Patent Application No. 61-28).
No. 0889 (see JP-A-63-136124),
Japanese Patent Application No. 1-327276 (see Japanese Patent Application Laid-Open No. 3-189716) and Japanese Patent Application No. 1-327277 (Japanese Unexamined Patent Application Publication No.
89717) and the like).

[0008]

However, in the above-described position detecting device, when the resonance frequency of the resonance circuit changes, the level of the received signal (induced voltage) also changes.
The period corresponding to each bit of the binary code must be sufficiently longer than one coordinate detection period, or a period for code identification must be provided completely separately from the coordinate detection period. There is a problem that it takes a long time to transmit or the sampling rate of the coordinate detection becomes low.

SUMMARY OF THE INVENTION In view of the above-mentioned conventional problems, an object of the present invention is to provide a position detecting device capable of transmitting a large amount of information at a high speed without lowering a sampling rate for coordinate detection.

[0010]

In order to achieve the above object, according to the present invention, there is provided a position indicator having at least a resonance circuit, and a position indicated by the position indicator by transmitting and receiving radio waves to and from the position indicator. And a tablet for calculating the coordinate values of
A code generating means for generating a plurality of codes respectively corresponding to the plurality of indicator information, and a resonance frequency control means for continuously changing a resonance frequency of the resonance circuit according to the code are provided. Frequency detecting means for detecting the frequency of the radio wave generated from the resonance circuit, so that the frequency of the radio wave to be transmitted and the frequency of the radio wave to be received according to the detected frequency always coincide with the resonance frequency of the resonance circuit A position detection system comprising: frequency tracking control means for performing tracking control; and information identification means for reproducing a code corresponding to a change in the resonance frequency in the resonance circuit from the frequency detected by the frequency detection means and identifying indicator information. Suggest a device.

Further, according to the present invention, there is provided a position pointing device having at least a radio wave generating means for generating a radio wave and a power supply for driving the same, a radio wave transmitted from the position pointing device, and an instruction by the position pointing device. In a position detecting device comprising a tablet for obtaining the coordinate value of the position,
Code generating means for generating a plurality of codes respectively corresponding to the plurality of indicator information, and frequency control means for continuously changing the frequency of the radio wave generating means according to the code are provided, and the tablet is provided with a position indicator. Frequency detecting means for detecting the frequency of a radio wave generated from the radio wave generating means, and frequency tracking control for following and controlling the frequency of the radio wave received in accordance with the detected frequency so as to always match the frequency of the radio wave generating means The present invention proposes a position detecting device comprising: means for reproducing a code corresponding to a frequency change in the radio wave generating means from the frequency detected by the frequency detecting means, and information identifying means for identifying indicator information.

[0012]

According to the present invention, the frequency of the radio wave generated from the resonance circuit of the position pointing device is detected by the frequency detecting means, and the frequency of the radio wave to be transmitted and the frequency of the received radio wave always coincide with the detected frequency. Is controlled by the frequency follow-up control means so that the level change caused by the change in the frequency is eliminated, and a code corresponding to the change in the resonance frequency in the resonance circuit is reproduced from the detected frequency by the information identification means. , Indicator information is identified.

Further, according to the present invention, the frequency of the radio wave generated from the radio wave generating means of the position indicator is detected by the frequency detecting means, and the frequency of the received radio wave always coincides with the detected frequency. The tracking control is performed by the frequency tracking control means, the level change caused by the change in the frequency is eliminated, and a code corresponding to the frequency change in the radio wave generating means is reproduced from the detected frequency by the information identification means, Information is identified.

[0014]

FIG. 1 shows a first embodiment of the present invention.
In the figure, 11a is a coil, 11b is a capacitor for blocking DC, 11c is a variable capacitance diode, 12 is a diode for supplying power, 13 is a code generator, 14 is a voltage controller,
For example, an integrator 15 is a capacitor for supplying power, S1,
S2 is a switch, and these constitute a position indicator A. 21-1, 21-2, 21-3, 21-4 are loop coils, 22 is a selection circuit, 23 is an auxiliary antenna coil, 24 is a voltage controlled oscillator, 25 is a current driver, 2
6, 27 are transmission / reception switching circuits, 28, 29 are reception amplifiers, 3
0 is a synchronous detector, 31 is a phase comparator, 32 is a switch,
33 and 34 are low-pass filters (LPF), 35 and 36 are analog / digital (A / D) conversion circuits, and 37 is a processing unit (CPU).

The coil 11a, the capacitor 11b, and the variable capacitance diode 11c are connected in series with each other to form a well-known resonance circuit 11. Diode 1
2 extracts a DC voltage from the induced voltage generated in the resonance circuit 11, and uses the DC voltage as a power supply voltage to generate a code generator 13;
And to the integrator 14. The code generator 13 generates a low-level voltage corresponding to the bit “0” when neither of the switches S1 and S2 is operated, and outputs a low-level voltage when the switch S1 or S2 is operated. Start bits ST before and after the corresponding plurality of bits, here 8-bit binary codes b1 to b8.
(“1”) and a stop-bit SP (“0”) are added to generate a known start-stop synchronization data signal, which is supplied to the integrator 14. Note that the code generation period of the data signal is set to be about 10 times as long as one scanning period described later, for example, about 10 ms. The integrator 14 is a well-known device including an operational amplifier, a resistor, a capacitor, and the like. The integrator 14 receives the data signal, and continuously changes the low-level to high-level and high-level to low-level changes. Is supplied to the variable capacitance diode 11c.

Since the capacitance value of the variable capacitance diode 11c changes according to the applied voltage, the switch S1 or S2 is operated and a data signal is generated from the code generator 13 and is supplied through the integrator 14. The resonance frequency of the resonance circuit 11 also changes according to the voltage value of the signal.

FIGS. 2A and 2B show switches S1 and S2, respectively.
Shows an example of how the resonance frequency changes when is operated. In the figure, the frequencies f1 and f2 indicate the frequencies of the resonance circuit 11 when the low-level and high-level voltages are output from the code generator 13, respectively. Resonant frequency, for example 495
kHz and 505 kHz. Here, the switch S1
Are operated, the binary codes b1 to b8 generated by the code generator 13 are “00110100”, and
The example shows that the binary codes b1 to b8 generated by the code generator 13 when the switch S2 is operated are "01001010".

The loop coils 21-1 to 21-4 are arranged side by side substantially parallel to each other in the position detection direction, and one end of each is connected to the selection circuit 22, and the other end is commonly grounded. I have. The selection circuit 22 receives the loop coil 21-1 according to a predetermined selection signal applied from the processing device 37.
21-4, one loop coil is sequentially selected. The auxiliary antenna coil 23 includes loop coils 21-1 to 21-4.
, One end of which is connected to the voltage-controlled oscillator 24 and the other end is grounded.

The voltage controlled oscillator 24 has the frequency f1 described above.
A free-running frequency is defined as a frequency f0 between 500 and f2, for example, 500 kHz, and a predetermined control signal, in this case, an AC signal having a frequency and a phase corresponding to the output voltage of the low-pass filter 34 is generated. , To the synchronous detector 30 and the phase comparator 31. The current driver 25 converts the AC signal into a current and sends it to the transmission / reception switching circuit 27.
The transmission / reception switching circuit 26 connects or grounds one loop coil selected by the selection circuit 22 to the reception amplifier 28 in accordance with a predetermined transmission / reception switching signal applied from the processing device 37. The transmission / reception switching circuit 27 alternately switches and connects the current driver 25 and the reception amplifier 29 to the auxiliary antenna coil 23 according to a predetermined transmission / reception switching signal applied from the processing device 37.

The receiving amplifier 28 generates a signal in the selected one of the loop coils, and the selecting circuit 22 and the transmission / reception switching circuit 26
, And amplifies the induced voltage sent to the synchronous detector 30. The reception amplifier 29 amplifies the induced voltage generated in the auxiliary antenna coil 23 and transmitted via the transmission / reception switching circuit 27, and transmits the amplified voltage to the phase comparator 31. The synchronous detector 30 synchronously detects the induced voltage generated in the one loop coil, that is, the received signal as a detection signal of an AC signal from the voltage controlled oscillator 24, and sends the signal to the low-pass filter 33. The phase comparator 31 compares the phase of the induced voltage generated in the auxiliary antenna coil with the phase of the AC signal from the voltage controlled oscillator 24, generates a phase difference signal, and sends it to the low-pass filter 34 via the switch 32. In addition,
The switch 32 operates according to a control signal from the processing device 37.
This is to prevent the output signal of the phase comparator 31 from being sent to the low-pass filter 34 when the transmission / reception switching circuit 27 is on the transmission side.

The low-pass filter 33 has the frequency f0,
It has a cutoff frequency sufficiently lower than f1 and f2, converts the output signal of the synchronous detector 30 into a DC signal, and sends it to the A / D conversion circuit 35. The low-pass filter 34 also has a cut-off frequency sufficiently lower than the above-mentioned frequencies f0, f1, f2, and converts the output signal of the phase comparator 31 into a DC signal to convert the output signal from the voltage-controlled oscillator 24 and the A / D conversion circuit. 36. The A / D conversion circuits 35 and 36 convert the outputs of the low-pass filters 33 and 34 from analog to digital, respectively, and send them to the processing device 37. The processing device 37 is provided with each of the loop coils 21-1 to 21 converted into the digital value.
-4 based on the voltage value of the received signal corresponding to -4
Is calculated, and the state of the switch of the position indicator A is identified based on the control signal of the voltage controlled oscillator 24 converted into the digital value.

Next, the operation of the device will be described.

First, when the auxiliary antenna coil 23 is connected to the current driver 25 via the transmission / reception switching circuit 27 and an AC current having a free-running frequency f0 is supplied from the voltage controlled oscillator 24, the frequency f0 is output from the auxiliary antenna coil. Radio waves are generated. The radio wave excites the coil 11 a of the position indicator A and gives electromagnetic energy to the resonance circuit 11. Also,
At this time, the selection circuit 22 selects one of the loop coils from the loop coils 21-1 to 21-4 based on the selection signal from the processing device 37. Since the input terminal of the amplifier 28 is grounded, the signal generated in the one loop coil is not transmitted to the receiving amplifier 28. Thereafter, when the auxiliary antenna coil 23 is connected to the receiving amplifier 29 via the transmission / reception switching circuit 27, the generation of radio waves from the auxiliary antenna coil 23 stops.

On the other hand, the electromagnetic energy applied to the resonance circuit 11 is supplied to a coil 11a to generate a radio wave, and a part thereof is transmitted through a diode 12, a capacitor 15 to a code generator 13 and an integrator 14. To drive these. At this time, assuming that none of the switches S1 and S2 of the position indicator A are operated, the output of the code generator 13 remains at the low level as described above, and the resonance frequency of the resonance circuit 11 becomes f1. Therefore, the radio wave of the frequency f1 is continuously generated from the coil 11a. The radio wave excites the auxiliary antenna coil 23 together with the one selected loop coil,
An induced voltage of the frequency f1 is generated in the one loop coil and the auxiliary antenna coil 23.

The induced voltage generated in the auxiliary antenna coil 23 is amplified by the receiving amplifier 29,
1 and is compared in phase with the AC signal from the voltage controlled oscillator 24. Here, the resonance frequency of the resonance circuit 11 is f1 as described above, and the phase of the induced voltage is initially delayed with respect to the phase of the AC signal.
The output voltage of 1 becomes negative. Therefore, the output voltage of the low-pass filter 34 also becomes negative, and the voltage-controlled oscillator 24
Oscillation frequency changes from f0 to f1. The output voltage of the low-pass filter 34 is output from an A / D conversion circuit 36.
To the processing device 37 through the above-mentioned condition. In this case, the value changes from 0 to minus (actually, a digital value smaller than a predetermined digital value corresponding to the output voltage 0 [V] of the low-pass filter 34). To the switches S1 and S2 of the position indicator A.
Are not operated.

The induced voltage generated in the one loop coil is amplified by the receiving amplifier 28 and sent out to the synchronous detector 30, synchronously detected using the AC signal from the voltage controlled oscillator 24 as a detection signal, and further subjected to a low-pass filter 33. And A /
The signal is sent to the processing device 37 via the D conversion circuit 35 as a voltage value. Thereafter, the one loop coil selected by the selection circuit 23 is sequentially switched and the same operation is repeated, and the voltage value of the induced voltage generated in each of the loop coils 21-1 to 21-4 is transmitted to the processing device 37. Is done.

The voltage value of the induced voltage extracted from each of the loop coils 21-1 to 21-4 depends on the distance between each loop coil and the resonance circuit 11, and becomes larger as the distance is smaller. Therefore, the voltage value of the induced voltage extracted from each of the loop coils 21-1 to 21-4 is determined by the position of the resonance circuit 11,
That is, the induced voltage corresponding to the loop coil closest to the position indicated by the position indicator A is maximized, and gradually decreases as the corresponding loop coil moves away from the indicated position. The voltage value of each of the induced voltages is subjected to arithmetic processing by the processing device 37, and the position where the distribution of the voltage value is maximum, that is, the position indicator
The coordinate value of the designated position is obtained.

In this state, for example, when the switch S1 of the position indicator A is operated, the resonance frequency of the resonance circuit 11 is changed to an 8-bit binary code "00110100" (actually, before and after that) corresponding to the switch S1. 2 (a) with the start bit ST “1” and the stop bit SP “0” added thereto, the frequency changes between f1 and f2 as shown in FIG. The frequency of the voltage changes as well.

Since the phase of the induced voltage other than the frequency f0 does not coincide with the phase of the AC signal from the voltage controlled oscillator 24, the phase comparator 31 during the period in which the frequency of the induced voltage changes between f1 and f2. A voltage having a sign and a value corresponding to the phase difference is output. Accordingly, the output of the low-pass filter 34 also has a sign and a value corresponding to the phase difference during a period in which the frequency of the induced voltage changes between f1 and f2.
It is controlled so as to oscillate between 1 and f2, and the change in the frequency of the induced voltage does not change the output voltage value of the synchronous detector 30, that is, does not affect the coordinate value of the designated position.

At this time, the output voltage of the low-pass filter 34 is converted into a digital value by the A / D conversion circuit 36 as described above and sent to the processing device 37. The frequency of the induced voltage is other than f0. During the period, the value of the induced voltage becomes a value corresponding to the frequency, that is, a value smaller or larger than a predetermined digital value corresponding to the output voltage 0 [V] of the low-pass filter 34. Change, and when the digital value first becomes larger than the predetermined digital value, the starting point (start bit S
T), by sampling at the code generation cycle of the code generator 13 and detecting whether the digital value is larger or smaller than the predetermined digital value, the processing device 37 converts the digital value output from the A / D conversion circuit 36 into 8 bits. In this case, it can be identified that the switch S1 has been operated on the position indicator A. Further, when the switch S2 is operated on the position indicator A, it can be similarly identified.

As described above, according to the present embodiment, even if the resonance frequency of the resonance circuit changes, the signal strength of the received signal does not change, so that the period corresponding to each bit of the binary code is once performed as in the conventional case. It is not necessary to extend the coordinate detection period sufficiently, or to provide a period for code identification completely separate from the coordinate detection period. Therefore, a large amount of information can be transmitted at high speed without lowering the sampling rate of coordinate detection. Can be.

In the above-described embodiment, the position is detected in one direction. A plurality of loop coils similar to the loop coils 21-1 to 21-4 are arranged so as to be orthogonal thereto, and a selection circuit similar to the above is provided. It is needless to say that the designated positions in the two orthogonal directions can be detected by providing and alternately detecting the position by using another circuit. In this case, since one scan is performed in two directions of the x and y directions, the code generation cycle of the data signal is set to be twice as long as that in one direction, for example, about 20 ms.

FIG. 3 shows another example of the position indicator in the first embodiment. Here, a battery is provided as a power source for the code generator and the integrator, instead of a diode and a capacitor for supplying power. Here is an example. That is, in the figure, 16
Is a well-known NiCad battery or the like, and both ends thereof are connected to power terminals of the code generator 13 and the integrator 14, respectively. According to this configuration, the code generator and the integrator can be driven with a stable power supply voltage, and information can be transmitted without error.

FIG. 4 shows a second embodiment of the present invention. In the figure, the same components as those of the first embodiment are denoted by the same reference numerals. That is, 11a is a coil, 13 is a code generator, 14 is an integrator, 16 is a battery, 17 is a voltage controlled oscillator, S1 and S2 are switches, and these constitute a position indicator A. 23 is an auxiliary antenna coil, 28
Is a reception amplifier, 30 is a synchronous detector, 33 is a low-pass filter (LPF), and 35 and 36 are analog / digital (A / A / D).
D) a conversion circuit; 37a, a processing device (CPU);
1, 38-2,..., 38-8 are conductors, 39 is a selection circuit,
Reference numeral 40 denotes a PLL receiving circuit, which constitutes a tablet B.

The voltage controlled oscillator 17 has the frequency f1 described above.
Is a free-running frequency, and a predetermined control signal, here, an integrator 1
An AC signal having a frequency and a phase corresponding to the output voltage of No. 4 is generated and sent to the coil 11a. As described above, the code generator 13 generates a low-level voltage corresponding to the bit "0" when neither the switch S1 nor the switch S2 is operated. In this case, the voltage-controlled oscillator 17 outputs the alternating current having the frequency f1. Signal. Therefore, the radio wave of the frequency f1 is transmitted from the coil 11a of the position indicator A in a state where neither the switch S1 nor the switch S2 is operated, and the switch S1 or S
2 is operated, the frequency becomes f1 as shown in FIG.
A radio wave varying between f2 and f2 is transmitted.

The conductors 38-1 to 38-8 are arranged side by side substantially in parallel with each other in the position detection direction. One end of each of the conductors is connected to the selection circuit 39, and the other end thereof is commonly grounded. . The selection circuit 39 sequentially selects one of the conductors 38-1 to 38-8 according to a predetermined selection signal applied from the processing device 37a. The auxiliary antenna coil 23 is disposed so as to surround the conductors 38-1 to 38-8. One end of the auxiliary antenna coil 23 is connected to the PLL receiving circuit 40, and the other end is grounded.

The PLL receiving circuit 40 generates a reference AC signal having the same frequency and phase as the induced voltage generated in the auxiliary antenna coil 23, sends the signal to the synchronous detector 30, and outputs the reference AC signal. The control signal representing the phase is processed by the processing device 37 via the A / D conversion circuit 36.
a. The receiving amplifier 28 amplifies the induced voltage generated on the one selected conductor and sent through the selecting circuit 39 and sends it to the synchronous detector 30. The synchronous detector 30 synchronously detects the induced voltage generated in the one conductor, that is, the received signal, using the reference AC signal from the PLL receiving circuit 40 as a detection signal, and sends it to the low-pass filter 33.

The low-pass filter 33 has the frequency f0,
It has a cutoff frequency sufficiently lower than f1 and f2, converts the output signal of the synchronous detector 30 into a DC signal, and sends it to the A / D conversion circuit 35. The A / D conversion circuits 35 and 36 convert the output of the low-pass filter 33 and the output of the PLL receiving circuit 40 from analog to digital, respectively, and send them to the processing device 37a. The processing device 37a calculates the coordinate value of the position indicated by the position indicator A based on the voltage value of the received signal corresponding to each of the conductors 38-1 to 38-8 converted into the digital value, and converts the coordinate value into the digital value. The state of the switch of the position indicator A is identified based on the converted control signal of the PLL receiving circuit 40.

The operation of the above device will be described below.

Initially, the switches S1 and S2 of the position indicator A
Are not operated, and the radio wave of the frequency f1 is continuously generated from the coil 11a, the radio wave is transmitted to each of the conductors 38-1 to 38-8 and the auxiliary antenna coil 23.
, An induced voltage having a frequency f1 is generated. Each conductor 38-1
The induced voltages generated at .about.38-8 are sequentially sampled by the selection circuit 39, amplified by the reception amplifier 28 and sent to the synchronous detector 30, and synchronously detected using the reference AC signal from the PLL receiving circuit 40 as a detection signal. Further, the voltage is sent to the processing device 37a as a voltage value through the low-pass filter 33 and the A / D conversion circuit 35.

Here, the direction of the radio wave with respect to each conductor is opposite at the center position (indicated position) of the coil 11a, and the phase of the induced voltage is also inverted at the indicated position. The signal is also a signal of opposite polarity from the indicated position. Therefore, the output signal of the low-pass filter 33 crosses 0 [V] corresponding to the indicated position. The voltage value of each of the induced voltages is processed by the processing device 37a, and the position where the voltage value crosses 0 [V], that is, the coordinate value of the position indicated by the position indicator A is obtained.

The induced voltage generated in the auxiliary antenna coil 23 is received by the PLL receiving circuit 40, and the PLL receiving circuit 40 generates a reference AC signal having the same frequency and phase as the induced voltage, and performs synchronous detection. At the same time, a control signal indicating the frequency and phase of the induced voltage is generated and sent to the processing device 37a via the A / D conversion circuit 36. Here, the frequency of the induced voltage is continuously f1, and the control signal also corresponds to the frequency. Therefore, the processing device 37a determines that none of the switches S1 and S2 of the position indicator A is operated. I do.

In this state, for example, when the switch S1 of the position indicator A is operated, the frequency of the radio wave transmitted from the coil 11a is changed to the 8-bit binary code "00110100" (actually, the switch S1). Before and after the start bit ST “1” and the stop bit SP
2A, the frequency changes between f1 and f2 as shown in FIG. 2A, so that the frequency of the induced voltage generated in the auxiliary antenna coil 23 also changes.

The induced voltage other than the frequency f1 is also the frequency f
1, is received by the PLL receiving circuit 40,
Since a reference AC signal having the same frequency and phase is generated and sent to the synchronous detector 30, a change in the frequency of the induced voltage does not change the output voltage value of the synchronous detector 30, that is, the coordinate value of the designated position. Does not affect

At this time, the control signal representing the frequency and phase of the induced voltage output from the PLL receiving circuit 40 is converted into a digital value in the A / D conversion circuit 36 as described above, and is sent to the processing device 37a. The starting point (start bit ST) is when the digital value first becomes larger than a predetermined value, for example, a value corresponding to the frequency f0.
By sampling at the code generation cycle of the code generator 13 and detecting whether the value is larger or smaller than the value corresponding to the frequency f0, the processing device 37a performs A / D
An 8-bit binary code can be reproduced from the output digital value of the conversion circuit 36. In this case, it is possible to recognize that the switch S1 has been operated in the position indicator A. Further, when the switch S2 is operated on the position indicator A, it can be similarly identified.

As described above, according to the present embodiment, even if the frequency of the radio wave transmitted from the position indicator changes, the signal strength of the received signal does not change. It is not necessary to make the time period for performing the detection sufficiently longer than one coordinate detection period or to provide a period for code identification completely separate from the coordinate detection period. Therefore, much information can be obtained without lowering the sampling rate for coordinate detection. It can be transmitted at high speed. Further, in this embodiment, it is not necessary to transmit radio waves from the tablet to the position indicator, and once the position of the position indicator is detected, the position is determined only by selecting two conductors located on both sides of the position indicator. Since the detection is possible, one scanning cycle can be greatly reduced as compared with the case of the first embodiment, so that the code generation cycle of the data signal is also larger than that of the first embodiment. And can transmit information faster.

In the above-described embodiment, the position detection in one direction is performed. A plurality of conductors similar to the conductors 38-1 to 38-8 are arranged so as to be orthogonal thereto, and a selection circuit similar to the above is provided. It goes without saying that the designated position in two orthogonal directions can be detected by alternately detecting the position by using another circuit. In this case, since one scan is performed in two directions of the x and y directions, the code generation cycle of the data signal is set to be twice as long as that in the one direction. The same is true.

FIG. 5 shows another example of the tablet in the second embodiment. Here, an example in which an FM detection circuit and a voltage controlled oscillator are used instead of the PLL receiving circuit is shown. That is, in the figure, 41 is an FM detection circuit, 42 is a voltage controlled oscillator, and the FM detection circuit 41 performs FM detection of the induced voltage generated in the auxiliary antenna coil 23, and a frequency signal representing the frequency and phase of the induced voltage. Which is sent to the voltage controlled oscillator 42 and the A / D conversion circuit 36
To the processing device 37a via the. The voltage controlled oscillator 42 generates a predetermined control signal, in this case, an AC signal having a frequency and a phase corresponding to the frequency signal from the FM detection circuit 41, using the frequency f0 as a free-running frequency, and synchronously detects the signal. To the vessel 30. Other configurations and operations are the same as those of the tablet of the second embodiment.

[0049] shows the case of providing the hitherto two switches in the position indicator in the examples, be identified those provided 2 ^eight switches corresponding to the binary code of 8 bits It is possible, and it is also possible to provide more switches by increasing the number of bits of the binary code. Further, when information indicating the type of the position indicator itself is transmitted, the information may be always transmitted.

[0050]

As described above, according to the present invention, even if the resonance frequency of the resonance circuit changes, the signal strength of the received signal does not change. Does not need to be sufficiently longer than one coordinate detection period, or to provide a code identification period completely separate from the coordinate detection period. Therefore, much information can be transmitted at high speed without lowering the coordinate detection sampling rate. Can be transmitted.

Further, according to the present invention, even if the frequency of the radio wave transmitted from the position indicator changes, the signal strength of the received signal does not change. Does not need to be sufficiently longer than one coordinate detection period, or to provide a code identification period completely separate from the coordinate detection period. Therefore, much information can be transmitted at high speed without lowering the coordinate detection sampling rate. Can be transmitted.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a first embodiment of a position detection device of the present invention.

FIG. 2 is a diagram showing an example of a change in resonance frequency when switches S1 and S2 are operated.

FIG. 3 is a configuration diagram showing another example of the position indicator in the first embodiment.

FIG. 4 is a configuration diagram showing a second embodiment of the position detection device of the present invention.

FIG. 5 is a configuration diagram showing another example of the tablet in the second embodiment.

[Explanation of symbols]

11a: coil, 11b: capacitor, 11c: variable capacitance diode, 12: diode for power supply, 13 ...
Code generator, 14 integrator, 15 power supply capacitor, 16 battery, 17, 24, 42 voltage controlled oscillator, 25 current driver, S1, S2 switch, 21
-1 to 21-4: loop coil, 22, 39: selection circuit, 23: auxiliary antenna coil, 26, 27: transmission / reception switching circuit, 28, 29: reception amplifier, 30: synchronous detector, 3
DESCRIPTION OF SYMBOLS 1 ... Phase comparator, 32 ... Switch, 33, 34 ... Low-pass filter (LPF), 35, 36 ... Analog / Digital (A / D) conversion circuit, 37, 37a ... Processing device (CP
U), 38-1 to 38-8: conductor, 40: PLL receiving circuit, 41: FM detection circuit, A: position indicator, B: tablet.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G06F 3/03

Claims (9)

(57) [Claims] 1. A position detecting device comprising: a position indicator having at least a resonance circuit; and a tablet for transmitting and receiving radio waves to and from the position indicator to obtain a coordinate value of a position indicated by the position indicator. The indicator is provided with code generation means for generating a plurality of codes respectively corresponding to the plurality of pieces of indicator information, and resonance frequency control means for continuously changing the resonance frequency of the resonance circuit according to the codes. A frequency detecting means for detecting a frequency of a radio wave generated from a resonance circuit of the position indicator, and a frequency of a radio wave to be transmitted and a frequency of a radio wave to be received in accordance with the detected frequency are always defined as a resonance frequency of the resonance circuit Frequency follow-up control means for performing follow-up control so as to coincide with each other, and a resonance frequency in the resonance circuit based on the frequency detected by the frequency detection means. Play the code corresponding to the change, the position detecting apparatus is characterized by providing the information identifying means for identifying the pointing device information. 2. A code generator for generating a plurality of codes respectively corresponding to a plurality of indicator information, a voltage controller for generating a voltage value that continuously changes according to the code, and a capacity according to the voltage value A position indicator having a resonance circuit including an element whose value or induction value changes, and a power supply circuit for extracting a DC voltage for driving the code generator and the voltage controller from an induction voltage generated in the resonance circuit; A plurality of loop coils arranged in parallel in the detection direction, a selection unit for sequentially selecting one loop coil from the plurality of loop coils, an auxiliary antenna coil provided near the plurality of loop coils, and resonance of the position indicator AC signal supply means for supplying an AC signal for generating a radio wave for exciting a circuit to the auxiliary antenna coil, a frequency of an induced voltage generated in the auxiliary antenna coil Frequency detection means for detecting the frequency of the AC signal supplied from the AC signal supply means according to the detected frequency so as to always match the resonance frequency of the resonance circuit, the selected frequency tracking control means, Receiving detection means for detecting an induced voltage generated in the loop coil with an AC signal generated from the AC signal supply means, and position determination for obtaining an indicated position of the position indicator based on the magnitude of each detected induced voltage. Means, and a tablet having information identification means for reproducing a code corresponding to a change in the resonance frequency in the resonance circuit from the frequency detected by the frequency detection means and identifying indicator information. Detection device. 3. A code generator that generates a plurality of codes respectively corresponding to a plurality of indicator information, a voltage controller that generates a voltage value that continuously changes in accordance with the code, and a capacity in accordance with the voltage value A resonance circuit including an element whose value or induction value changes, a position indicator having a battery for supplying a DC voltage for driving the code generator and the voltage controller, and a plurality of cells arranged in parallel in the position detection direction. A loop coil, selecting means for sequentially selecting one loop coil from the plurality of loop coils, an auxiliary antenna coil provided near the plurality of loop coils, and a radio wave for exciting a resonance circuit of the position indicator. AC signal supply means for supplying the AC signal to the auxiliary antenna coil, frequency detection means for detecting the frequency of the induced voltage generated in the auxiliary antenna coil, Frequency follow-up control means for controlling the frequency of the AC signal supplied from the AC signal supply means in accordance with the obtained frequency, so as to always coincide with the resonance frequency of the resonance circuit, and the induced voltage generated in the selected loop coil. Reception detection means for detecting with an AC signal generated from the AC signal supply means, position determination means for obtaining the position indicated by the position indicator based on the magnitude of each of the detected induced voltages, and detection by the frequency detection means A tablet having information identification means for reproducing a code corresponding to a change in the resonance frequency in the resonance circuit from the frequency, and identifying the indicator information. 4. The position detecting device according to claim 2, wherein a variable capacitance diode is used as the element whose capacitance value changes according to the voltage value. 5. A position indicator having at least a radio wave generator for generating a radio wave and a power supply for driving the same, and a coordinate value of a position indicated by the position indicator by receiving a radio wave transmitted from the position indicator In a position detection device comprising: a tablet for obtaining a plurality of codes; a position indicator; code generation means for generating a plurality of codes respectively corresponding to the plurality of pieces of indicator information; and continuously changing the frequency of the radio wave generation means in accordance with the codes. Frequency control means for changing the frequency of the radio wave, a frequency detecting means for detecting the frequency of the radio wave generated from the radio wave generating means of the position indicator, and a frequency of the radio wave received in accordance with the detected frequency. Frequency tracking control means for performing tracking control so as to always coincide with the frequency of the generation means, and from the frequency detected by the frequency detection means to the radio wave generation means Kicking reproduces the code corresponding to the change of frequency, the position detection device is characterized by providing the information identifying means for identifying the pointing device information. 6. A code generator for generating a plurality of codes respectively corresponding to a plurality of indicator information, a voltage controller for generating a voltage value that continuously changes in accordance with the code, and a frequency in response to the voltage value Radio wave generating means including an oscillator having variable power, a position indicator having a power source for driving the code generator, the voltage controller and the radio wave generating means, a plurality of conductors juxtaposed in the position detection direction, and the plurality of conductors Selecting means for sequentially selecting one of the conductors, an auxiliary antenna coil provided in the vicinity of the plurality of conductors, frequency detecting means for detecting a frequency of an induced voltage generated in the auxiliary antenna coil, and matching the detected frequency Detection signal generation means for generating a detection signal of a frequency to be detected, reception detection means for detecting an induced voltage generated in the selected conductor by the detection signal, and detection of each of the detected induced voltages. Said position determining means for determining the position indicated by the position indicator, and reproduces the code corresponding to the change of frequency in the radio wave generating means from the detected frequency by said frequency detecting means based on sex change,
A position detecting device comprising: a tablet having information identifying means for identifying indicator information. 7. A PLL receiving circuit as a frequency detecting means and a detection signal generating means.
The position detecting device as described in the above. 8. The position detection device according to claim 6, wherein an FM detection circuit is used as the frequency detection means, and a voltage control oscillator is used as the detection signal generation means. 9. The position detecting device according to claim 1, wherein a data signal of an asynchronous system is used as the code.