JPH0793083A - Position detecting device - Google Patents

Abstract

PURPOSE:To eliminate the influence of an external noise on position detecting operation and obtained coordinate values without making a user take trouble or a time. CONSTITUTION:The oscillation frequency of a voltage-controlled oscillator 29 is set to the starting resonance frequency of a resonance circuit 10 and a switching connection circuit 25 is fixed on the side of a receiving amplifier 28 to detect a noise level at the starting resonance frequency from an auxiliary antenna coil 23. And when the noise level exceeds a certain value, an electromagnetic wave of frequency different from the starting resonance frequency is sent to and received by the resonance circuit 10 and variation of the resonance frequency of the resonance circuit 10 is urged through a host device 47 to perform position detection with the electromagnetic wave of frequency under no influence of the external noise.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a position detecting device utilizing electromagnetic induction.

[0002]

2. Description of the Related Art Conventionally, an electromagnetic induction action is provided between a sensing portion having a plurality of conductors or loop coils arranged in parallel in at least a position detecting direction and at least a position indicator having an electromagnetic wave radiating member such as a coil. There is known a position detection device that obtains the coordinate value of the position pointed by the position pointer based on the above.

For example, the applicant is the Japanese Patent Application No. 61-21397.
No. 0 (see JP-A-63-70326),
One loop coil is selected from the plurality of loop coils of the sensing section, an alternating current of a predetermined frequency is supplied to this to generate an electromagnetic wave, and the electromagnetic wave is received by the coil of the resonance circuit provided in the position indicator, At this time, the one loop coil receives the electromagnetic wave transmitted from the coil of the resonance circuit which is supplied with the energy by the electromagnetic wave to generate an induced voltage, which is sequentially switched and repeated for a plurality of loop coils. We have proposed a device that determines the position of the coil of the resonance circuit, that is, the coordinate value of the indicated position based on the level of the induced voltage generated in the loop coil.

By the way, in the position detecting device, each loop coil receives an electromagnetic wave only from the coil of the resonance circuit provided in the position indicator, and generates an induced voltage depending only on the position indicated by the position indicator. It is assumed.

However, in practice, other than the coil of the resonance circuit, for example, a circuit for selecting each loop coil or a circuit for supplying an alternating current to the loop coil, an electronic circuit constituting the position detecting device itself, or Random electromagnetic waves or AC magnetic fields (hereinafter referred to as "external noise") jump into the loop coils from the host computer, display, etc. used with the position detecting device, or other electronic devices, so that an induced voltage is generated in each loop coil. May be completely unrelated to the pointing position of the position pointing device, or may include a random error component.

Further, in this type of position detecting device, a plurality of position indicators may be used by using different frequencies. In this case, in particular, external noise may occur at any frequency. It was very good.

For this reason, the coordinate value of the position pointed by the position pointing device cannot be obtained at all, and in the position detecting device, generally, the above-mentioned coordinate detection is carried out from 100 to several 1 per second.
This is repeated 00 times, but at this time, the obtained coordinate value includes a variation (hereinafter referred to as jitter) due to the random error in the induced voltage described above, and for example, the position indicator is not moved at all. There was a problem that the value did not become constant even in the state.

Conventionally, as a method of solving such a problem, there has been a method of attenuating the external noise by using a bandpass filter having a narrow passband that allows only the frequency of the electromagnetic wave transmitted from the position indicator side to pass. . In addition, as another method, the current value of the alternating current applied to the loop coil of the sensing unit is increased to increase the electromagnetic energy supplied to the resonance circuit of the position indicator, and the strength of the electromagnetic wave transmitted from the resonance circuit is increased. There has been a method of increasing the SN ratio to improve the SN ratio of the received signal. Furthermore, as another method, there is a method of changing the frequency of an electromagnetic wave exchanged between the sensing unit and the position indicator. As a method of reducing the above-mentioned coordinate value jitter, there has been a method of averaging a plurality of, for example, about 5 to 10, coordinate values that are continuous on the time axis.

[0009]

However, since each of the above-mentioned methods has its own drawbacks, any one or more of them are uniformly applied to all position detecting devices. I couldn't.

For this reason, conventionally, at the time when the above-mentioned problem actually occurs, the user himself or the user requests the maker to select one or more of the above-mentioned methods that are considered to be appropriate. It took a lot of effort and time to solve the problem because I had to choose a method and deal with it.

Recently, a pen input type computer in which the position detecting device described above is integrated in the main body of the device has been developed. This computer is used not only in a normal office but also in a factory or an outdoor work site. Since it is expected to be used in a place where the conditions are relatively strict, that is, where the emission of unnecessary electromagnetic waves to the outside is significantly limited or there is a lot of extraneous noise, it is more difficult to solve the above problems. I was doing.

It is an object of the present invention to provide a position detecting device capable of eliminating the position detecting operation and the influence on the obtained coordinate value due to the external noise without the user taking time and effort.

Another object of the present invention is to provide a position detecting device capable of appropriately eliminating the position detecting operation caused by external noise and the influence on the obtained coordinate values depending on the environment of use.

[0014]

In order to achieve the above object, the present invention has a sensing section having at least a plurality of conductors or loop coils arranged in parallel in the position detecting direction, and at least an electromagnetic wave radiating member such as a coil. A position detection device that includes a position indicator and detects the coordinate value of the position pointed by the position indicator based on the electromagnetic induction action between them, and is used for the electromagnetic induction action between the sensing unit and the position indicator. A position detecting device is proposed which is provided with a noise level detecting means for detecting a noise level at a frequency, and a frequency changing means for changing a frequency to be used to another frequency when the detected noise level exceeds a certain value. .

Further, a sensing section having at least a plurality of conductors or loop coils arranged in parallel in the position detection direction, and a position indicator having at least a resonance circuit are provided,
In the position detection device that detects the coordinate value of the position pointed by the position indicator by exchanging electromagnetic waves having a frequency that resonates in the resonance circuit between them, at the frequency of the electromagnetic waves exchanged between the sensing unit and the position indicator. Noise level detection means for detecting the noise level, frequency changing means for changing the frequency of the electromagnetic wave to another frequency when the detected noise level exceeds a certain value, and frequency of the electromagnetic wave is changed to another frequency. In that case, a position detection device provided with a guidance means for urging the resonance frequency of the resonance circuit to change is proposed.

Further, at least a sensing unit having a plurality of conductors or loop coils arranged in parallel in the position detecting direction and a position indicator having at least an electromagnetic wave radiating member such as a coil are provided, and an electromagnetic induction action therebetween. In a position detecting device for detecting the coordinate value of the position indicated by the position indicator based on the above, noise level detecting means for detecting a noise level at a frequency used in an electromagnetic induction action between the sensing section and the position indicator, A position detecting device provided with level control means for relatively increasing the level of a signal relating to the electromagnetic induction action from the detected noise level is proposed.

Further, at least a sensing section having a plurality of conductors or loop coils arranged in parallel in the position detecting direction and a position indicator having at least an electromagnetic wave radiating member such as a coil are provided, and an electromagnetic induction action therebetween. A position detection device that detects the coordinate value of the position indicated by the position indicator based on the above, and averages and outputs a predetermined number of coordinate values that are continuous on the time axis among the detected coordinate values. Level detecting means for detecting a noise level at a frequency used by an electromagnetic induction action between the control section and the position indicator, and arithmetic control for increasing or decreasing the number of coordinate values to be averaged according to the detected noise level. And a position detecting device provided with the means.

[0018]

According to the present invention, the noise level detecting means detects the noise level at the frequency used for the electromagnetic induction action between the sensing portion and the position indicator, and when the detected noise level exceeds a certain value. The frequency changing means changes the frequency to be used to another frequency.

Further, according to the present invention, the noise level detecting means detects the noise level at the frequency of the electromagnetic wave exchanged between the sensing section and the position indicator, and when the detected noise level exceeds a certain value. The frequency changing means changes the frequency of the electromagnetic wave to another frequency, and the guidance means prompts to change the resonance frequency of the resonance circuit.

Further, according to the present invention, the noise level detecting means detects the noise level at the frequency used for the electromagnetic induction action between the sensing portion and the position indicator, and the level control means detects the detected noise level. The level of the signal relating to the electromagnetic induction action is relatively increased.

According to the present invention, the noise level detecting means detects the noise level at the frequency used for the electromagnetic induction action between the sensing section and the position indicator, and the arithmetic control means detects the detected noise level. The number of coordinate values to be averaged is increased or decreased according to

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of the position detecting device of the present invention, in which 10 is a resonance circuit, 21-1, 21-.
2, 21-3 and 21-4 are loop coils, 22 is a selection circuit, 23 is an auxiliary antenna coil, 24 and 25 are switching connection circuits, 26 is a current driver, 27 and 28 are receiving amplifiers,
29 is a voltage controlled oscillator (VCO), 30 is a frequency counter, 31 is a phase shifter, 32 is a phase comparator, 33 is a resistor, 34 is a capacitor, 35 is a digital / analog conversion circuit (D / A converter), and 36 is switching. Circuit, 37,
38 is a synchronous detector, 39 and 40 are low-pass filters (LP
F), 41 and 42 are sample hold (S / H) circuits,
43 and 44 are analog / digital conversion circuits (A / D converters), 45 is a memory, and 46 is a processing device (CP).
U) and 47 are upper devices.

The resonance circuit 10 includes a coil 11, a capacitor 12 and a trimmer capacitor 13 which are connected to both ends of the coil 11 so as to be in parallel with each other, a switch 14 which is turned on / off according to a use state, and the switch 14. And a capacitor 15 connected to both ends of the coil 11 via a coil, and constitutes a position indicator which can be moved to an arbitrary position according to an operation of an operator.

Here, the capacitance value of the capacitor 15 is set to a value much smaller than the total capacitance value of the capacitor 12 and the trimmer capacitor 13, and the resonance frequency of the resonance circuit 10 initially turns off the switch 14. Is set to a predetermined frequency, for example, f11, and when the switch is turned on, the frequency is set to a frequency slightly lower than the frequency f11, for example, f12. Further, the resonance frequency of the resonance circuit 10 is changed (including fine adjustment) by adjusting the trimmer capacitor 14, and, for example, the resonance frequency f11,
f12 can be changed to different resonance frequencies f21 and f22.

The resonance frequencies f11 and f12 (or f21)
And f22) are close enough to obtain a reception signal of a sufficient level from the resonance circuit 10 regardless of whether the switch is on or off regardless of whether the frequency of the transmission electromagnetic wave is f11, f12 (or f21, f22). The resonance frequencies f11, f12 and f21, f22 are almost the same as those of the resonance circuit 10 having the resonance frequency f21 or f22 when the frequency of the transmission electromagnetic wave is f11 (or f12). No
Further, if the frequency of the transmitted electromagnetic wave is f21 (or f22), the resonance frequency is set to a frequency far from the resonance circuit 10 having the resonance frequency f11 or f12 so that a reception signal is hardly obtained.

The loop coils 21-1 to 21-4 are juxtaposed substantially parallel to each other in the position detecting direction, one end of each is connected to the selection circuit 22, and the other ends thereof are commonly grounded. There is. The selection circuit 22 is responsive to a predetermined selection signal applied from the processing unit 46 to form the loop coil 21-1.
One loop coil is sequentially selected from 21-4. The auxiliary antenna coils 23 are loop coils 21-1 to 21-4.
Are arranged so as to surround the periphery of the, and one end thereof is connected to the switching connection circuit 25, and the other end is grounded.

The switching connection circuit 24 is responsive to a predetermined switching connection signal applied from the processing unit 46 to select the selection circuit 22.
The one loop coil selected by the receiving amplifier 27
Connect to or ground. The switching connection circuit 25 is the processing device 4
In accordance with a predetermined switching connection signal added from No. 6, the current driver 26 and the receiving amplifier 2 are added to the auxiliary antenna coil 23.
8 are alternately switched and connected.

The current driver 26 converts an AC signal generated by the voltage controlled oscillator 29 into a current and switches the connection circuit 25.
Send to. The reception amplifier 27 is generated in the selected one loop coil, and the selection circuit 22 and the switching connection circuit 24
The induced voltage sent via the amplifier is amplified and sent to the synchronous detector 38. The reception amplifier 28 amplifies the induced voltage generated in the auxiliary antenna coil 23 and sent through the switching connection circuit 25, and sends it to the phase comparator 32 and the synchronous detector 37.

The voltage controlled oscillator 29 generates a predetermined control signal, here an AC signal having a frequency and a phase corresponding to the terminal voltage of the capacitor 34, and sends this to the current driver 26, the frequency counter 30 and the phase shifter 31. . The frequency counter 30 measures the frequency of the output signal of the voltage controlled oscillator 29 and sends the result to the processing device 46. The phase shifter 31 is for correcting the phase shift due to the transmission and reception of electromagnetic waves, and shifts the output signal of the voltage controlled oscillator 29 by a predetermined phase and sends it to the phase comparator 32 and the synchronous detectors 37 and 38.

The phase comparator 32 compares the phase of the induced voltage generated in the auxiliary antenna coil 23 with the AC signal from the phase shifter 31 to generate a phase difference signal, and the resistance 3
3. Send to the capacitor 34 via the switching circuit 36.
The resistor 33 constitutes an integrating circuit together with the capacitor 34 connected via the switching circuit 36, and outputs the output voltage thereof, that is, the terminal voltage of the capacitor 34 to the voltage controlled oscillator 29 as a control signal. That is, the voltage-controlled oscillator 29, the phase comparator 31, the resistor 33, and the capacitor 34 are well-known PLs.
Will form L.

Further, the D / A converter 35 is the switching circuit 3
6 for setting the terminal voltage of the capacitor 34 connected via 6 to an arbitrary designated voltage.
The digital signal representing the specified voltage supplied from the converter 3 is converted into an analog voltage value, and the capacitor 3 is converted through the switching circuit 36.
It sends to 4. The switching circuit 36 causes the capacitor 34 to receive the resistance 3 according to a predetermined switching signal applied from the processing device 46.
Either one of the 3 and the D / A converter 35 is connected. Note that the D / A converter 35 does not have a resistor because the terminal voltage of the capacitor 34 is rapidly changed to a specified voltage value.

The synchronous detectors 37 and 38 synchronously detect the induced voltage generated in the auxiliary antenna coil and one loop coil, that is, the received signal, using the AC signal from the phase shifter 31 as the detected signal, and the low pass filters 39 and 40. Send to.
The low-pass filters 39 and 40 have cutoff frequencies sufficiently lower than the frequencies f11 to f22 described above, and the synchronous detector 37,
The output signal of 38 is converted into a DC signal, and the S / H circuit 41,
42 to 42. The S / H circuits 41 and 42 are processing devices 46.
The voltage values of the output signals of the low-pass filters 39 and 40 described above are held at predetermined timings according to the added sampling signal, and are sent to the A / D converters 43 and 44. The A / D converters 43 and 44 convert the outputs of the S / H circuits 41 and 42 into analog / digital signals and send them to the processing device 46.

The memory 45 stores the relationship between the usage state (switch ON / OFF here) of the resonance circuit (position indicator) 10 measured by the processing device 46 as described later and the resonance frequency corresponding thereto. To do.

The processing unit 46 detects the noise level as will be described later. If the noise level exceeds a certain value, the frequency of the electromagnetic wave is changed, and this is transmitted to the host unit 47. The coordinate value of the indicated position of the resonance circuit (position indicator) 10 is calculated based on the voltage value of the received signal corresponding to each loop coil 21-1 to 21-4 converted into the digital value, and the frequency counter 30 The usage state of the resonance circuit (position indicator) 10 is identified based on the measured value of.

The host device 47 includes an input unit, a storage unit, a display unit, a processing unit, etc., which are not shown, and receives an instruction from the processing device 46 to give guidance to an operator.

FIG. 2 is a flow chart for detecting the noise level and changing the frequency of the electromagnetic wave, and the operation of the apparatus will be described below in accordance with the flow chart.

The processing unit 46 supplies the D / A converter 35 with a digital signal for outputting a control voltage corresponding to the frequency of the initial electromagnetic wave, that is, f11, for example, V11, and the switching circuit 36 is operated by the D / A converter. Connected to the 35 side, the terminal voltage of the capacitor 34 is set to V11 and the voltage controlled oscillator 29 generates an AC signal of frequency f11. At this time, the processing device 46 causes the frequency counter 30
Read the measured value and confirm that the oscillation frequency of the voltage-controlled oscillator 29 is f11. If different, D /
The digital value supplied to the A converter 35 is adjusted.

Next, the processor 46 connects the switching connection circuit 25 only to the receiving amplifier 28 side to start the reception of the electromagnetic wave by the auxiliary antenna coil 23, and at the same time, the A / D
The reading of the digital value from the converter 43 is started.

In this case, since the auxiliary antenna coil 23 does not generate an electromagnetic wave and the resonance circuit 10 is not supplied with electromagnetic energy, the resonance circuit 10 also does not generate an electromagnetic wave.
Therefore, at this time, the signal generated in the auxiliary antenna coil 23, amplified by the receiving amplifier 28, passes through the synchronous detector 37 to which the AC signal of the frequency f11 is input as the detection signal, and finally from the A / D converter 43. The digital value read by the processor 46 becomes the noise level at the frequency f11.

The processor 46 compares the noise level with a certain value, and if it is less than the certain value, it shifts to the normal coordinate detection mode. If it exceeds the certain value, the frequency of the electromagnetic wave is changed as follows. To change.

The processing unit 46 supplies the D / A converter 35 with a digital signal for outputting a control voltage corresponding to another preset frequency of the electromagnetic wave, that is, f21, for example, V21, and outputs the terminal voltage of the capacitor 34. The voltage-controlled oscillator 29 is set to V21 to generate an AC signal of frequency f21. At this time, the processing device 46 reads the measured value of the frequency counter 30 and confirms that the oscillation frequency of the voltage controlled oscillator 29 is f21, and if it is different, supplies the same to the D / A converter 35. Adjust the digital value.

Next, the processing unit 46 detects the noise level at the frequency f21 in the same manner as above, and if the noise level exceeds a certain value, further changes the frequency of the electromagnetic wave and repeats this.

On the other hand, if the noise level is below a certain level, the processor 46 operates the switching connection circuit 25 to start the alternate transmission and reception of electromagnetic waves by the auxiliary antenna coil 23, and the switching circuit 36 to the phase comparator 32 side. In addition, the reading of the measurement value of the frequency counter 30 for every fixed cycle is started. Furthermore, the processing device 46 transmits the fact that the frequency of the electromagnetic wave is changed to the higher-level device 47, and the higher-level device 47 turns off the resonance circuit 10 and the effective area for position detection (effective area here). Means a two-dimensional coordinate input range determined by the positions where the loop coils 21-1 to 21-4 are arranged, and a three-dimensional area determined by the readable height). The operator is informed of a message prompting to change the resonance frequency of the resonance circuit 10 through a display device or the like.

Initially, the frequency of the electromagnetic wave transmitted from the auxiliary antenna coil 23 is f21, but at this time, if the resonance frequency of the resonance circuit 10 is not changed to the extent of resonating with the electromagnetic wave of the frequency f21, During the reception period, no induced voltage is generated in the auxiliary antenna coil 23, and nothing is output from the phase comparator 32. As a result, the terminal voltage of the capacitor 34 gradually decreases due to self-discharge, and the oscillation frequency of the voltage controlled oscillator 29 also decreases accordingly.

When the oscillation frequency of the voltage controlled oscillator 29 is lowered and the resonance circuit 10 begins to resonate with the electromagnetic wave transmitted from the auxiliary antenna coil 23, the electromagnetic energy stored in the resonance circuit 10 is stored in the resonance circuit 10. Electromagnetic waves are emitted in reverse from the coil, and an induced voltage is generated in the auxiliary antenna coil 23 during the reception period. The induced voltage is sent to the phase comparator 32 via the reception amplifier 28, is phase-compared with the AC signal from the voltage-controlled oscillator 29 (correctly via the phase shifter 31), and corresponds to the frequency and phase difference. The voltage value is sent to the capacitor 34 via the resistor 33. As a result, the well-known PLL operation works and the oscillation frequency of the voltage controlled oscillator 29 is fixed to the resonance frequency of the resonance circuit 10.

When the frequency read from the frequency counter 30 does not change, the processing unit 46 checks whether the frequency is f21 or not, and if so, transmits information indicating that the change of the frequency of the electromagnetic wave is completed to the upper level device 47. Then, the upper device 47 notifies the operator of a message instructing the end of the change of the resonance frequency of the resonance circuit 10 through the display device or the like. Further, the processing device 46 transmits the fact that the frequency when the use state of the resonant circuit 10 is changed, that is, when the switch 14 is turned on, to the upper device 47, and the upper device 47 switches the resonant circuit 10 to the switch. A message prompting the operator to turn off is notified to the operator via a display device or the like, the frequency when the switch 14 is turned on is detected in the same manner as described above, and the memory 45 together with the frequency when the detected switch 14 is off is detected. To memorize.

On the other hand, if the frequency read from the frequency counter 30 is not f21, the processor 46 again
A digital signal for outputting the control voltage V21 corresponding to the frequency f21 is supplied to the D / A converter 35 to set the terminal voltage of the capacitor 34 to V21, and this is repeated thereafter.

When the change of the frequency of the electromagnetic wave and the change of the resonance frequency of the resonance circuit are completed in this way, the processing device 4
6 shifts to the normal coordinate detection mode. The operation of the normal coordinate detection mode is the same as that of the conventional one, and the description thereof is omitted.

In the above embodiment, one frequency is used and
The case of using one position indicator has been described, but it is also applicable to the case of using a plurality of position indicators by using different frequencies. In this case, the noise level at each frequency may be detected in the same manner as described above, and the frequency at which the noise level exceeds a certain value may be changed to another frequency in the same manner as described above.

Further, in the above-mentioned embodiment, when the noise level exceeds a certain value, the influence is eliminated by changing the frequency of the electromagnetic wave. The effect can be eliminated by increasing the level relatively, for example, by increasing or decreasing the radiation intensity of the electromagnetic wave generated from the loop coil according to the noise level, thereby relatively increasing the level of the received signal.

FIG. 3 is a flow chart for noise level detection and increase / decrease in radiation intensity of electromagnetic waves, and the hardware configuration and noise level detection processing are the same as those in the above embodiment. There are various methods of controlling the radiation intensity of electromagnetic waves, but here, control is performed so that the ratio of the signal level and the noise level obtained when transmitting and receiving electromagnetic waves to the resonance circuit in the effective area becomes a predetermined value or more. Here is an example.
It should be noted that if the radiation intensity of the electromagnetic wave is increased, the power consumption is correspondingly increased and the device may become a radiation source of the unnecessary electromagnetic wave to the outside.

Also, this method can be applied to a case where a plurality of position indicators are used by using different frequencies, as in the above. In that case, the noise level at each frequency may be detected, and the level of the signal relating to the electromagnetic induction action may be made relatively higher than the detected noise level for each frequency.

Further, as described in the conventional example, in general,
The position detection device repeats the coordinate detection 100 to several hundreds of times per second, and further, among the detected coordinate values, a predetermined number of continuous coordinate values on the time axis are averaged and output. However, it is possible to eliminate the influence by increasing or decreasing the number of coordinate values to be averaged according to the noise level while keeping the electromagnetic wave frequency unchanged.

FIG. 4 is a flowchart when the number of coordinate values to be subjected to noise level detection and averaging processing is increased or decreased, and the hardware configuration and the noise level detection processing are the same as those in the above embodiment. It should be noted that if the number of coordinate values to be averaged increases, the response speed of coordinate value detection slows down accordingly, and the followability to the position indicator deteriorates. Therefore, the number cannot be increased indefinitely.

Also, this method can be applied to the case where a plurality of position indicators are used by using different frequencies, similarly to the above. In that case, the noise level at each frequency may be detected, and the number of coordinate values to be averaged may be increased or decreased for each frequency according to the detected noise level.

Further, in the above-mentioned embodiment, the electromagnetic waves are alternately transmitted and received, but the present invention can be applied to the one which simultaneously transmits and receives the electromagnetic waves.

Furthermore, in the description so far, the position indicator is provided with a resonance circuit, and electromagnetic waves are transmitted and received between the resonance circuit and the sense section including the loop coil, so that the position indicator is cordless and battery-less. As mentioned above, the position indicator is provided with a cord or a built-in oscillator, an AC signal is sent from these to the coil to emit an electromagnetic wave, and the sensing unit only receives the electromagnetic wave. The present invention can also be applied to a device, or conversely, a device in which only the position indicator side receives electromagnetic waves oscillated by the sensing unit. Needless to say, adjustment is not necessary on the side of the position indicator when changing the operating frequency in such a device.

[0058]

As described above, according to the present invention, the noise level at the frequency used for the electromagnetic induction action between the sensing section and the position indicator is detected, and the detected noise level has a constant value. If it exceeds the limit, the frequency to be used will be changed to another frequency, so it will not be necessary for the user or the user to request the manufacturer to deal with the problem when there is a problem as in the past, and the position will not be affected by external noise. It becomes possible to detect.

Further, according to the present invention, the noise level at the frequency of the electromagnetic wave exchanged between the sensing section and the position indicator is detected, and when the detected noise level exceeds a certain value, the frequency of the electromagnetic wave is changed. Since it is changed to another frequency and the change of the resonance frequency of the resonance circuit is promoted, it is not necessary for the user himself or the user to request the manufacturer to deal with the problem when a problem occurs as in the conventional case.
It is possible to detect the position without being affected by external noise.

Further, according to the present invention, the noise level at the frequency used for the electromagnetic induction action between the sensing section and the position indicator is detected, and the level of the signal relating to the electromagnetic induction action is detected from the detected noise level. Is relatively large, it becomes unnecessary for the user himself or the user to request the manufacturer to deal with the problem when a problem occurs as in the past, and it becomes possible to perform position detection without being affected by external noise. It is possible to provide a device that does not consume useless power or become a radiation source of unnecessary electromagnetic waves.

Further, according to the present invention, the noise level at the frequency of the electromagnetic wave used for the electromagnetic induction action between the sensing section and the position indicator is detected, and the averaging process is performed according to the detected noise level. Since the number of coordinate values is increased / decreased, it is no longer necessary for the user or the user to request the manufacturer to deal with the problem when there is a problem as in the past, and it is possible to detect the position without being affected by external noise. Therefore, it is possible to provide a device in which the response speed of coordinate value detection is unlimitedly delayed and the followability to the position indicator is not deteriorated.

[Brief description of drawings]

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

FIG. 2 is a flowchart for noise level detection and electromagnetic wave frequency change.

FIG. 3 is a flowchart for noise level detection and increase / decrease in radiation intensity of electromagnetic waves.

FIG. 4 is a flowchart when the number of coordinate values to be subjected to noise level detection and averaging is increased or decreased.

[Explanation of symbols]

10 ... Resonance circuit, 21-1 to 21-4 ... Loop coil,
22 ... Selection circuit, 23 ... Auxiliary antenna coil, 24, 2
5 ... Switching connection circuit, 26 ... Current driver, 27, 28 ...
Reception amplifier, 29 ... Voltage controlled oscillator, 30 ... Frequency counter, 31 ... Phase shifter, 32 ... Phase comparator, 33 ... Resistor, 34 ... Capacitor, 35 ... Digital / analog conversion circuit, 36 ... Switching circuit, 37, 38 ... Synchronous detector, 3
9, 40 ... Low-pass filter, 41, 42 ... Sample and hold circuit, 43, 44 ... Analog / digital conversion circuit,
45 ... Memory, 46 ... Processing device, 47 ... Host device.

Claims (15)

[Claims] 1. A sense unit having a plurality of conductors or loop coils arranged in parallel in at least a position detection direction, and a position indicator having at least an electromagnetic wave radiation member such as a coil, and an electromagnetic induction action therebetween. A position detecting device for detecting the coordinate value of the position pointed by the position indicator based on the following: noise level detecting means for detecting a noise level at a frequency used for electromagnetic induction between the sensing section and the position indicator, A position detecting device, comprising: frequency changing means for changing a frequency to be used to another frequency when the detected noise level exceeds a certain value. 2. When using a plurality of position indicators each using a different frequency, the noise level at each frequency is detected, and the frequency at which the noise level exceeds a certain value is changed to another frequency. The position detecting device according to claim 1, wherein the position detecting device is made. 3. The position detecting device according to claim 1, further comprising frequency changing means for changing a frequency of an electromagnetic wave generated from a coil of the position pointing device. 4. An electromagnetic wave having a frequency that resonates in the resonance circuit between at least a sense section having a plurality of conductors or loop coils arranged in the direction of position detection and a position indicator having at least a resonance circuit. A position detecting device for detecting the coordinate value of the position pointed by the position indicator by exchanging a noise level detecting means for detecting the noise level at the frequency of the electromagnetic wave exchanged between the sensing section and the position indicator; When the detected noise level exceeds a certain value, frequency change means to change the frequency of the electromagnetic wave to another frequency, and when the frequency of the electromagnetic wave is changed to another frequency, prompt the change of the resonance frequency of the resonance circuit. A position detecting device provided with guidance means. 5. When using a plurality of position indicators each using a different frequency, a noise level at each frequency is detected, and a frequency whose noise level exceeds a certain value is changed to another frequency and 5. The position detecting device according to claim 4, wherein the position detecting device is adapted to prompt a change in the resonance frequency of the resonance circuit of the position indicator. 6. The position detecting device according to claim 1, further comprising frequency changing means for changing the frequency of the electromagnetic wave generated from the conductor of the sensing section or the loop coil. 7. A sensing unit having a plurality of conductors or loop coils arranged in parallel in at least the position detection direction, and a position indicator having at least an electromagnetic wave radiation member such as a coil, and an electromagnetic induction action therebetween. A position detecting device for detecting the coordinate value of the position pointed by the position indicator based on the following: noise level detecting means for detecting a noise level at a frequency used for electromagnetic induction between the sensing section and the position indicator, A position detecting device, comprising level control means for relatively increasing a level of a signal relating to an electromagnetic induction action from a detected noise level. 8. When using a plurality of position indicators each using a different frequency, the noise level at each frequency is detected, and the level of the signal related to the electromagnetic induction action is detected from the detected noise level for each frequency. 7. The method according to claim 7, characterized in that
The position detection device described. 9. The position detecting device according to claim 7, further comprising level control means for increasing or decreasing the radiation intensity of the electromagnetic wave generated from the conductor or the loop coil of the sensing section according to the noise level. 10. The position detecting device according to claim 7, further comprising level control means for increasing or decreasing the radiation intensity of the electromagnetic wave generated from the coil of the position indicator according to the noise level. 11. A sense section having a plurality of conductors or loop coils arranged in parallel in at least a position detection direction,
A position indicator having at least an electromagnetic wave radiating member such as a coil, and detecting the coordinate value of the position indicated by the position indicator based on the electromagnetic induction action therebetween, and the time axis of the detected coordinate values. In a position detecting device for averaging and outputting a predetermined number of consecutive coordinate values above, a noise level detecting means for detecting a noise level at a frequency used for an electromagnetic induction action between a sensing section and a position indicator. And a calculation control means for increasing or decreasing the number of coordinate values to be averaged according to the detected noise level. 12. A coordinate value for detecting a noise level at each frequency and averaging according to the detected noise level for each frequency when a plurality of position indicators are used by using different frequencies. 12. The position detecting device according to claim 11, wherein the number of is increased or decreased. 13. A noise level detecting means for detecting a signal level at a frequency used for an electromagnetic induction action between the sensing section and the position indicator when there is no electromagnetic induction action to obtain a noise level. The position detecting device according to any one of claims 1 to 12, characterized by the above-mentioned. 14. A position indicator having a resonance circuit capable of changing a resonance frequency to an arbitrary frequency, a plurality of loop coils arranged in parallel in a position detection direction, and an auxiliary provided near the plurality of loop coils. An antenna coil, a selection unit that sequentially selects one loop coil from the plurality of loop coils, a first induction voltage detection unit that detects an induction voltage generated in the selected loop coil, and the first induction unit. Coordinate value calculation means for obtaining the coordinate value of the pointing position of the position pointing device based on the level of each induced voltage detected by the voltage detection means; variable frequency signal generation means for generating an AC signal of an arbitrary frequency; Frequency measuring means for measuring the frequency of the AC signal generated from the frequency signal generating means, and an AC signal generated from the variable frequency signal generating means and a resonance circuit of the position indicator. A frequency difference detecting means for detecting a frequency difference between the generated and received electromagnetic waves; a second induced voltage detecting means for detecting an induced voltage generated in the auxiliary antenna coil; and the variable frequency signal in the auxiliary antenna coil. Switching connection means for switching and connecting the generating means, the frequency difference detecting means, and the second induced voltage detecting means, and the second when the variable frequency signal generating means is not continuously connected to the auxiliary antenna coil for a certain period of time or more. Noise level detecting means for detecting a noise level based on the induced voltage detected by the induced voltage detecting means, and the variable frequency signal generating means if the noise level detected by the noise level detecting means exceeds a certain value. Frequency control means for controlling to change the frequency of the AC signal generated from the frequency to another preset frequency, and the frequency control means. A position detecting device comprising: guidance means for urging the resonance frequency of the resonance circuit of the position indicator to change based on the frequency difference detected by the frequency difference detecting means after the frequency is changed by the step. 15. The position detecting device according to claim 14, wherein the auxiliary antenna coil is replaced by a loop coil.