JPH0417523B2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention is characterized in that the position indicator is not connected anywhere,
Moreover, the present invention relates to a position detection device with high position detection accuracy and a method thereof.

(Prior Art) As a conventional position detection device, a pulse current is applied to a drive coil provided at one end of a magnetostrictive transmission medium or a tip of a position indicator, and magnetostrictive vibration waves are generated in the magnetostrictive transmission medium. , a processing device or the like measures the time until an induced voltage based on the magnetostrictive oscillation waves is detected in a detection coil provided at the tip of the position indicator or one end of the magnetostrictive transmission medium, and calculates the designated position of the position indicator from this. Something happened just like that. In addition, as another conventional position detection device, a plurality of drive lines and detection lines are arranged perpendicularly to each other, and current is sequentially applied to the drive lines and detection lines are sequentially selected to detect induced voltage. There was a device in which a position specified by a position indicator made of a magnetic material such as ferrite was detected from the position of a detection line in which a large induced voltage was induced.

(Problem to be solved by the invention) Although the former device has relatively good position detection accuracy, it requires a code between the position indicator and the processing device to send and receive timing signals, etc. There are problems in that handling is severely restricted and the position indicator must be held perpendicular to the magnetostrictive transmission medium and used very close to it. In addition, although the position indicator in the latter device can be made cordless, the resolution of the coordinate position is determined by the line spacing, and if the line spacing is made smaller to increase the resolution, the signal-to-noise ratio and stability will deteriorate. It is difficult to increase the resolution, it is difficult to detect the position directly above the intersection of the drive line and the detection line, and there are other problems such as the position indicator must be placed extremely close to the line. Ta.

The present invention provides a position detection device that has extremely good operability of a position indicator, has high position detection accuracy, can detect operations on the position indicator, and can easily fix or remove menu sheets, drawings, etc. The purpose is to provide a method.

(Means for Solving the Problems) In order to achieve the above object, the present invention transmits and receives signals between a position indicator and a tablet, and calculates coordinate values on the tablet indicated by the position indicator. The position detecting device detects and inputs the detected information to a host device such as a computer, and includes a first tuned circuit that is normally closed, and a tuned frequency of the first tuned circuit configured by operation. A radio wave that is composed of a position indicator having a different second tuning circuit and a plurality of loop coils in which adjacent loop coils are stacked on top of each other, and that generates a radio wave that can be tuned by the first and second tuning circuits. A tablet having a generating means and a radio wave detection means for detecting radio waves reflected from the first or second tuning circuit by switching and scanning the plurality of loop coils; Coordinate calculation means calculates the coordinate value of the indicated position of the indicator by a calculation finer than the arrangement interval of the plurality of loop coils, and the radio wave reflected from the position indicator is determined based on the induced voltage detected by the radio wave detection means. A position detection device comprising a tuned circuit determining means for detecting from which tuned circuit the radio wave is reflected, and an electrostatic adsorption mechanism provided on the tablet to electrostatically adsorb a menu sheet, etc. The present invention also provides a position detection method in which a position indicator is operated from an electrostatic adsorption mechanism mounted on a tablet and coordinate values on the tablet indicated by the position indicator are detected, the method comprising: Radio waves are generated by a radio wave generating means consisting of a plurality of loop coils in which adjacent tablets are stacked on top of each other, and the first, which is constantly closed, has a frequency that can be tuned to the radio waves as a tuning frequency. The radio waves are reflected by a position indicator having a tuning circuit and a second tuning circuit configured by operation and capable of tuning to the radio waves and having a tuning frequency different from that of the first tuning circuit. The reflected radio waves are detected by a radio wave detection means composed of a plurality of loop coils in which adjacent ones of the tablet are overlapped with each other, and the plurality of loop coils are switched and scanned, and the position is indicated from the detected induced voltage. The coordinate values of the indicated position of the position indicator are calculated with a precision finer than the arrangement interval of the plurality of loop coils, and the radio wave reflected from the position indicator is detected from which of the tuned circuits. We propose a position detection method that does this.

(Function) According to the device of the present invention, the menu sheet, etc. is held and fixed on the tablet by the electrostatic adsorption mechanism, and adjacent tablets are composed of a plurality of loop coils stacked on top of each other. When a radio wave is generated by the radio wave generating means, the radio wave is tuned to, or received by, the first or second tuning circuit of the position indicator that specifies the position on the tablet. The tuned circuit of the transmitter emits or reflects similar radio waves. The reflected radio waves are detected by radio wave detection means consisting of a plurality of loop coils in which adjacent tablets are overlapped with each other, and the plurality of loop coils are switched and scanned, and further detected by coordinate calculation means. The coordinate values of the indicated position of the position indicator are calculated with a precision that is finer than the arrangement spacing of the plurality of loop coils, and the radio waves reflected from the position indicator are determined by the tuned circuit determining means to determine which of the tuned circuits. It is detected whether the radio waves are reflected from

Further, according to the method of the present invention, by operating the position indicator on the menu sheet, etc. held and fixed on the tablet by the electrostatic adsorption mechanism, the coordinate values of the indicated position with respect to the menu sheet, etc. can be determined. At the same time, it is detected which of the first or second tuned circuit of the position indicator reflected the radio wave.

(Embodiment) FIG. 1 shows the configuration of a system of a position detection device as an embodiment of the present invention. In the figure, 1 is an input/output panel, 2 is a control device, 3 is a power supply device, and 60
is an input pen as a position indicator.

As shown in FIGS. 1 and 2, the input/output panel 1 includes position detectors 4X and 4Y in the X and Y directions.
An electrostatic chuck plate 5 is provided on the position detecting section 4, which is housed integrally in a case 6 made of plastic or the like.

As shown in FIGS. 3 and 4, the electrostatic adsorption plate 5 includes a back insulating layer 7, comb-shaped electrodes 8 and 9, and a terminal 1.
0 and 11, and a surface adsorption layer 12.
As the back insulating layer 7, a material having an electrical resistivity of 10 ¹⁵ Ωcm or more and a dielectric constant of 4 or less, for example, a hard vinyl chloride plate with a thickness of 5 mm is used.

For the electrodes 8 and 9, for example, polyvinyl chloride, conductive carbon black, and a plasticizer (polyester type) are kneaded in the same weight to make a conductive plastic sheet with a thickness of 0.5 mm, and this is punched out into a comb shape. None, and this is further arranged on the insulating layer 7 so that the teeth of the comb are interlocked with each other at equal intervals, and the comb is thermally bonded with a heat press and buried in the upper surface of the insulating layer 7, and the surface is finished to a smooth surface. That's what I did.

The terminals 10 and 11 are made of ordinary copper or the like, and are connected to the electrodes 8 and 9 by flat braided wires also made of copper and thermally bonded.

The adsorption layer 12 is made of a plastic dielectric material having an electrical resistivity of 10 ⁵ to ^{10 12} Ωcm and a dielectric constant of 4 to 12, such as equal amounts of nitrile butadiene rubber and methyl methacrylate resin (for PVC modification), and adding 1/ 10 carbon black was blended and kneaded with a hot roll to form a sheet with a thickness of 0.5 mm, and this sheet was layered on the electrode-embedding surface of the insulating layer 7 and bonded with a hot press. .

This electrostatic adsorption plate 5 is embedded approximately in the center of the upper surface of the case 6 of the tablet 1 through an insulating sheet (not shown), with the adsorption surface 13 flush with the peripheral surface thereof, and furthermore, the terminals 10 and 11 are It is connected to the power supply device 3.

Then, an object to be placed (an object to be attracted) A such as a menu sheet or a drawing is placed on the suction surface 13, and the terminals 10,
When a DC voltage of 1,000 to 5,000 volts is applied from the power supply 3 to 11, a charge of the opposite sign on the electrode is excited due to the dielectric polarization phenomenon, as shown in FIG. A force is created that attracts and holds it. Further, if this power source is turned off by the power supply device 3, the charges are quickly eliminated through the adsorption layer 12, and the adsorbed object A can be peeled off very easily.

The power supply device 3 is a well-known rectifier, transformer, DC
- It consists of a DC converter, etc., and supplies necessary power to the control device 2 in addition to the DC voltage of 1,000 to 5,000 volts.

FIG. 5 shows a position detection control circuit related to the X direction of the position detection section 4 and the configuration of the position detection section 4, and mainly describes control in the X direction. In the figure,
20 is a selection circuit, 30 is a connection switching circuit, 40 is a transmitting circuit, 50 is a receiving circuit, 60 is a position indicator, 7
0 is a processing device composed of an electronic computer or the like.

Position detector 4 (in the same figure, position detector 4 in the X direction)
Indicates X. ) is a plurality of conductors that are parallel to each other,
For example, 48 loop coils C1, C2,...C48
are arranged in parallel in the direction of arrow A (hereinafter referred to as the position detection direction) in the figure. Further, the loop coils C1 to C48 are arranged parallel to each other and overlapping each other.

The position detecting section 4 is formed by connecting a large number of parallel conductors formed by etching a well-known printed circuit board with jumper wires or the like to form the plurality of loop coils. can be used.

The selection circuit 20 selects the plurality of loop coils C1.
A loop coil is sequentially selected from C48, and one end of the loop coil C1 to C48 is connected to one terminal group 21, and the other end is connected to another terminal group 22. .
The selection contact 23 corresponding to the terminal group 21 and the selection contact 24 corresponding to the terminal group 22 are interlocked with each other,
It operates based on information from the processing device 70 and selects one loop coil.

The selection circuit 20 can be realized by combining a large number of well-known multiplexers.

The connection switching circuit 30 alternately connects one loop coil selected by the selection circuit 20 to the transmitting circuit 40 and the receiving circuit 50,
The selection contacts 23 and 24 of the selection circuit 20 are
They are connected to selection contacts 31 and 32, respectively. Further, the two output terminals of the transmitting circuit 40 are connected to the terminals 33 and 35, and the two output terminals of the receiving circuit 50 are connected to the terminals 33 and 35.
The two input terminals are connected to terminals 34 and 36. Selection contact 3 corresponding to the terminals 33 and 34
1, and selection contact 3 corresponding to terminals 35 and 36
2 are interlocked with each other and operate based on a transmission/reception switching signal, which will be described later, to switch between transmission and reception.

Note that the connection switching circuit 30 is also realized by a well-known multiplexer.

FIG. 6 is an overall configuration diagram of the position detection control circuit and the position detection section 4. The same parts as in FIG. are shown with the same reference numerals and a dash. In the figure, 4X and 4Y are X- and Y-direction position detection units formed on the printed circuit board, 20 and 20' are X- and Y-direction selection circuits, and 30 and 30' are X- and Y-direction position detection units. With connection switching circuit, position detector 4
Regarding X and 4Y, the respective loop coils shown in the position detecting section 4 in FIG. 4 are superimposed on each other so as to be orthogonal to the X direction and the Y direction, respectively.
Furthermore, the processing device 70 alternately performs position detection in the X direction and the Y direction.

FIG. 7 shows details of the transmitting circuit 40 and receiving circuit 50. Note that since the control in the X direction and the Y direction is the same, the figure shows one of them. In the figure, 41 is an oscillator, 42 is a frequency divider, 43 and 44 are NAND gates, 45 is an exclusive OR (EXOR) gate, and 46 is a drive circuit, which constitute the transmitting circuit 40. Further, 51 is an amplifier, 52 and 53 are phase detectors, and 5
4 and 55 are reduction filters (LPF), which constitute the receiving circuit 50.

The position indicator (hereinafter referred to as input pen) 60 is
It has a built-in tuning circuit 61 including a coil and a capacitor.

FIG. 8 shows the detailed structure of the input pen 60, in which the pen shaft 62 is made of a non-metallic material such as synthetic resin.
Inside, from the tip end, a core body 63 of a ballpoint pen or the like, a ferrite core 64 having a through hole capable of slidably accommodating the core body 63, and a coil spring 65.
, a switch 611, a coil 612 wound around the ferrite core 64, a capacitor 613,
614 and a tuning circuit 61 consisting of a variable capacitor 615 are integrated and built in, and a cap 66 is attached to the rear end.

The capacitor 613 and the variable capacitor 6
15 are connected in parallel to each other as shown in FIG. 9, and both ends thereof are connected to a coil 612, forming a well-known parallel resonant circuit. In addition,
The values of the coil 612, capacitor 613, and variable capacitor 615 are selected to resonate (synchronize) with the frequency of the radio waves transmitted from each loop coil of the position detection section 4.

On the other hand, a capacitor 614 is connected to both ends of the coil 612 via a switch 611, and when the switch 611 is turned on, it acts to delay the phase of the current in the parallel resonant circuit described above by a predetermined angle. In addition, when the switch 611 pushes the tip of the core 63 into the pen shaft 62 by pressing the tip of the core 63 against the input surface (not shown) of the position detection unit 4, the coil spring is activated by the rear end. 65 to turn it on.

In the above-mentioned tuning circuit 61, when the switch 611 is off, that is, the circuit consisting of the coil 612, the capacitor 613, and the variable capacitor 615 constitutes the first tuning circuit, and when the switch 611 is on, that is, the coil 612, capacitors 613 and 614, and a variable capacitor 615 constitute a second tuning circuit.

The processing device 70 controls switching of each loop coil and calculates designated coordinate values based on a transmission/reception switching signal described later and the output of the receiving circuit 50.

Note that the position detection section 4, selection circuit 20,
The connection switching circuit 30 and the transmission circuit 40 constitute radio wave generation means, and the position detection section 4 and the selection circuit 2
0, the connection switching circuit 30 and the receiving circuit 50 constitute a radio wave detecting means, and the processing device 70 constitutes a coordinate calculating means and a tuning circuit determining means.

The following operation will be described. First, the manner in which radio waves are transmitted and received between the position detection force section 4 and the input pen 60, and the signals obtained at this time will be described with reference to FIG.

In the transmitting circuit 40, the clock pulse of, for example, 4MHz generated by the oscillator 41 is sent to the frequency divider 4.
2 divides the frequency into 1/4, 1/8 and 1/256. One input terminal of the NAND gate 43 receives a 500kHz pulse signal A divided by 1/8, and the other input terminal receives a 15.625kHz transmission/reception switching signal B divided by 1/256. The output is further inverted by a NAND gate 44 to generate a signal C that outputs or does not output a 500kHz pulse signal every 32μsec.
becomes.

The signal C is converted into a balanced signal by the drive circuit 46, and is further sent to one loop coil, for example Ci, of the position detection section 4 via the connection switching circuit 30 and the selection circuit 20. The loop coil Ci generates radio waves based on the signal C.

At this time, if the input pen 60 is held in a substantially upright state near the loop coil Ci of the position detection section 4, the radio wave excites the coil 612 of the input pen 60, and the tuned circuit 61 receives the signal C. A synchronous induced voltage D is generated.

After that, when the signal C enters a no-signal period, that is, a reception period, and the loop coil Ci is switched to the reception circuit 50 side, the loop coil Ci
Although the electric wave immediately disappears, since there is no circuit change in the tuning circuit 61 of the input pen 60, the induced voltage D gradually attenuates.

On the other hand, the coil 612 generates radio waves by the current flowing through the tuned circuit 61 based on the induced voltage D. Since the radio waves reversely excite the loop coil Ci connected to the receiving circuit 50, the loop coil Ci
An induced voltage E is generated.

Since the connection switching circuit 30 is switched by the transmission/reception switching signal B, it receives the signal from the loop coil Ci only during the transmission stop period. The received signal E is amplified by an amplifier 51, and a signal F
The signal is further sent to phase detectors 52 and 53.

The pulse signal A is input to the phase detector 52 as a detection signal, and at this time, if the phase of the received signal F matches the phase of the pulse signal A, the received signal F is immediately turned to the positive side. Outputs an inverted signal G. The signal G is sent to a processing device 70 where it is converted into a flat signal H of voltage VH by a low-pass filter 54 having a sufficiently low cutoff frequency.

Further, the phase detector 53 receives the pulse signal A and the pulse signal with twice the frequency of the EXOR gate 4.
A pulse signal A' (not shown), which has the same frequency as the pulse signal A created by inputting the pulse signal A' to the pulse signal A and is delayed in phase by 90 degrees, is input as a detection signal. At this time, if the phase of the received signal F matches the phase of the pulse signal A', a signal I which is just an inversion of the received signal F to the negative side is output. The signal I is passed through a low-pass filter 55 with a sufficiently low cutoff frequency to a voltage of -
It is converted into a flat signal J of VJ and sent to the processing device 70.

Here, in the input pen 60, the switch 61
1 is off, the phases of the voltage and current at the resonant frequency of the tuning circuit 61 match as described above, and therefore the phases of the received signal F and pulse signal A match. At this time, a voltage appears only in the signal H, and no voltage appears in the signal J.

Further, in the input pen 60, a switch 611
is on, the phase of the current at the resonant frequency of the tuned circuit 61 lags the phase of the voltage by a predetermined angle, and therefore the phase of the received signal F also lags the phase of the pulse signal A. There will be a delay by a predetermined angle. At this time, a voltage appears in both signals H and J (if the phase delay at this time is 90°, a voltage will appear only in signal J).

Said signals H and J sent to processing device 70
is converted into a digital signal here, and further subjected to arithmetic processing shown in equations (1) and (2) below.

_V ^{_ _ _ _} _{_} indicates a value proportional to . Also, the voltage
V〓 indicates a value proportional to the phase difference between voltage and current in the tuning circuit 61 of the input pen 60.

The value of the voltage _VX changes when the loop coil Ci that transmits and receives radio waves to and from the input pen 60 is switched, and the position of the input pen 60 is detected from this as will be described later.

Since the value of the voltage V〓 changes only depending on whether the switch 611 is turned on or off, whether the switch 611 is on or off is identified by comparing the voltage V〓 with a predetermined threshold voltage.

Next, the state of position detection in the apparatus of the present invention will be explained with reference to FIGS. 11 to 13.

First, when the entire device is powered on and enters the measurement start state, the processing device 70 sends information for selecting the first loop coil C1 from among the loop coils C1 to C48 of the position detecting section 4 to the selection circuit 20. Connect the loop coil C1 to the connection switching circuit 30. The connection switching circuit 30 receives the above-mentioned transmission/reception switching signal B.
Based on the loop coil C1 as a transmitting circuit, 40
and the receiving circuit 50 alternately.

At this time, the transmitting circuit 40 sends 16 pulse signals of 500 kHz as shown in FIG. 11a to the loop coil C1 during a 32 μsec transmission period. The switching between transmitting and receiving is repeated seven times for one loop coil, here C1, as shown in FIG. 11b. These seven transmission and reception repetition periods correspond to one loop coil selection period (448 μsec).

At the outputs of the phase detectors 52 and 53 of the receiving circuit 50, induced voltages are obtained for one loop coil every seven reception periods, but these induced voltages are passed through the low-pass filters 54 and 53 as described above. The signals are averaged at 55 and sent to a processing device 70. The two induced voltages are converted into a detection voltage V _X1 proportional to the distance between the input pen 60 and the loop coil C1 by the above-mentioned arithmetic processing in the processing device 70, and are temporarily stored.

Next, the processing device 70 sends information for selecting the loop coil C1 to the selection circuit 20, and
2 to the connection switching circuit 30, and a detection voltage proportional to the distance between the input pen 60 and the loop coil C2.
After obtaining _V detected voltage V _X1 ~
V _X48 (however, only a part of it is shown in Figure 11c).

As shown in FIG. 12, the actual detected voltage is centered around the position (xp) where the input pen 60 is placed.
Detected voltage only in several loop coils before and after it
Va~Vg occurs.

When the voltage values of the stored detection voltages are above a certain detection level, the processing device 70 calculates coordinate values representing the position of the input pen 60 from these voltage values, and transfers the coordinate values to a storage section (not shown).

When the first position detection is completed in this way, the processing device 70 detects the loop coils C1 to C4.
Out of 8, the selection circuit 2 generates information that selects only a certain number of loop coils, for example 10, around the loop coil for which the maximum detected voltage was obtained.
0, the detection voltage is obtained in the same manner as described above, the position is detected, and the obtained coordinate values are transferred to the storage section and the values are updated.

On the other hand, the processing device 70 handles each of the detection voltages V _X1 to
Along with V _X48 , a detection voltage proportional to the phase difference between voltage and current in the tuning circuit 61 of the input pen 60
V〓 is calculated, and the detected voltage V〓 is constantly compared with a predetermined threshold voltage. Therefore, at this time, the input pen 6
When the switch 611 of 0 is turned on, the processing device 70
detects this from the comparison result, and sends the coordinate value at this point as an input value to another computer, etc. (not shown).

FIG. 13 shows the timing of the second and subsequent detection operations in the processing device 70. In the figure, the level check means checking whether the maximum value of the detection voltage has reached the detection level and which loop coil has the maximum detection voltage, and checking whether the maximum value of the detection voltage has reached the detection level. If not, the coordinate calculation is stopped, and the center of the loop coil to be selected in the next detection operation is set.

In addition to those shown in the embodiments, any electrostatic adsorption plate may be used as long as it can transmit radio waves.

(Effects of the Invention) As explained above, according to the device of the present invention, the radio wave generating means of the tablet allows the position indicator having the first and second tuning circuits having different tuning frequencies to A radio wave detection means constituted by a plurality of loop coils in which adjacent tablets generate radio waves that can be tuned by the first or second tuning circuit, and the radio waves reflected from the first or second tuning circuit are superimposed on each other. detecting the position by switching and scanning the plurality of loop coils, and further calculating the coordinate value of the indicated position of the position indicator with a precision finer than the arrangement interval of the plurality of loop coils by means of a coordinate calculating means. In addition, the tuned circuit determining means detects which of the tuning circuits the radio waves reflected from the position indicator are from, and since an electrostatic adsorption mechanism is provided on the tablet, the position indicator can be detected. The device should be equipped with passive elements such as coils and capacitors to form a tuned circuit.
This eliminates the need for cords and heavy parts such as batteries and magnets, which greatly improves operability and allows the coordinate values of indicated positions to be calculated with finer precision than the spacing between each loop coil, that is, with high precision. In addition, depending on which tuned circuit reflects the radio wave, it is possible to detect the coordinate values as well as the operation of the position indicator.Furthermore, it is possible to attach and remove menu sheets etc. on the tablet and to freely hold and Can be fixed. Furthermore, since the tablet does not require any special parts, it can be made larger and can be applied to electronic whiteboards and the like.

Further, according to the method of the present invention, a menu sheet, etc. is held and fixed on a tablet by an electrostatic adsorption mechanism, and radio waves are transmitted and received from the tablet to a position indicator operated on the tablet. In addition to calculating the coordinate values of the indicated position,
Since it detects which of the first or second tuned circuit of the position indicator reflected the radio wave, instructions for the menu sheet, etc. can be given simply by operating the position indicator on the menu sheet, etc. It is possible to obtain the coordinate values of a position, and in addition to detecting the coordinate values, it is also possible to detect an operation on the position indicator.

[Brief explanation of drawings]

Fig. 1 is a system diagram of a position detection device showing an embodiment of the present invention, Fig. 2 is a sectional view of an input/output panel,
Fig. 3 is a longitudinal sectional view of the electrostatic adsorption plate, Fig. 4 is a sectional view taken in the direction of the - line arrow in Fig. 2, Fig. 5 is a basic configuration diagram of the position detection control circuit and the position detection section, and Fig. 6 7 is an overall configuration diagram of the position detection control circuit and the position detection section.
The figure shows the detailed configuration of the transmitting circuit and the receiving circuit, and FIG. 8 shows the specific configuration of the input pen.
FIG. 9 is a configuration diagram of the tuning circuit, FIG. 10 is a waveform diagram of each part of FIG. 7, FIG. 11 is a timing diagram showing the basic detection operation in the present invention, and FIG.
A diagram showing the detection voltage obtained from each loop coil during the second detection operation, FIG. 13 is a timing diagram showing the second and subsequent detection operations, 4...position detection unit, 5...electrostatic adsorption plate, C1~
C48...Loop coil, 20...Selection circuit, 3
0...Connection switching circuit, 40...Transmission circuit, 50...
...reception circuit, 60 ... position indicator, 61 ... tuning circuit, 611 ... switch, 70 ... processing device,
4X...X direction position detector, 4Y...Y direction position detector.

Claims (1)

[Claims] 1. Signals are exchanged between the position indicator and the tablet, the coordinate values on the tablet indicated by the position indicator are detected, and this is input into a host device such as a computer. a position indicator, which is a position detection device and has a first tuned circuit that is normally closed; and a second tuned circuit that is configured by operation and has a different tuning frequency from the first tuned circuit; A radio wave generating means comprising a plurality of loop coils in which adjacent loop coils are stacked on top of each other and generates a radio wave that can be tuned by the first and second tuning circuits, and a radio wave reflected from the first or second tuning circuit. a tablet having a radio wave detection means for detecting radio waves by switching and scanning the plurality of loop coils; and a tablet having a radio wave detection means for detecting radio waves by switching and scanning the plurality of loop coils; coordinate calculation means for calculating with a precision finer than the arrangement spacing; and detecting which of the tuned circuits the radio waves reflected from the position indicator are from, based on the induced voltage detected by the radio wave detection means. What is claimed is: 1. A position detecting device comprising: a tuned circuit discriminating means; and an electrostatic adsorption mechanism provided on the tablet to electrostatically adsorb a menu sheet or the like. 2 At least three radio wave detection means adjacent to each other
Claim 1, characterized in that the invention comprises coordinate calculation means for calculating the coordinate value of the indicated position of the position indicator from the induced voltage detected by one loop coil with a precision finer than the arrangement interval of the plurality of loop coils. 1
The position detection device described in Section 1. 3. When the indicated position of the position indicator is not detected, all multiple loop coils are switched and scanned, and after the indicated position is detected, only the loop coils within a predetermined range including the indicated position are switched and scanned to detect radio waves. A position detection device according to claim 1 or 2, characterized in that it comprises a tablet having a detection means. 4. A position detection method in which a position indicator is operated from an electrostatic adsorption mechanism mounted on a tablet, and coordinate values on the tablet indicated by the position indicator are detected, which is adjacent to the tablet. a normally closed first tuning circuit that generates radio waves from a radio wave generating means composed of a plurality of loop coils stacked on top of each other, and has a tuning frequency that can be tuned to the radio waves; a second tuning circuit, which is configured by a second tuning circuit, is capable of tuning to the radio waves, and has a tuning frequency different from that of the first tuning circuit;
reflecting the radio waves with a position indicator having a tuning circuit; The coils are switched and scanned, and from the detected induced voltage, the coordinate values of the indicated position of the position indicator are calculated with a precision finer than the arrangement interval of the plurality of loop coils, and the coordinates of the position indicated by the position indicator are 1. A position detection method, comprising: detecting which of the tuning circuits a radio wave is reflected from. 5 At least three radio wave detection means adjacent to each other
Claim 4, characterized in that the coordinate value of the indicated position of the position indicator is calculated from the induced voltage detected by one loop coil with a precision finer than the arrangement interval of the plurality of loop coils. The position detection method described. 6. When the indicated position of the position indicator is not detected, all the plural loop coils of the radio wave detection means are switched and scanned, and after the indicated position is detected, only the loop coils within a predetermined range including the indicated position are switched and scanned to detect radio waves. A position detection method according to claim 4 or 5, characterized in that the position detection method is configured to detect.