JP2642592B2 - Position detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention eliminates the need to provide a connecting cable for a tablet or a battery for driving an oscillator in a position indicator, and determines whether or not an operator has performed the operation together with the position information. The present invention relates to a position detection device capable of detecting accurately.

[0002]

2. Description of the Related Art As a conventional position detecting device, an alternating current is supplied to an exciting coil provided at one end of a position indicator to generate an electromagnetic wave, thereby detecting an induced voltage locally generated in a tablet. , Or from a tablet to sequentially generate local electromagnetic waves at a predetermined timing,
As a result, a coordinate value at an arbitrary position can be detected by detecting an induced voltage generated in a detection coil provided at one end of the position indicator. However, this position detection device requires a connection cable for supplying an alternating current to the excitation coil of the position indicator or a connection cable for detecting the induced voltage from the detection coil of the position indicator. There was a problem that the property was not good.

In order to eliminate the above-mentioned drawbacks of the conventional position detecting device, an oscillator for supplying an alternating current to an exciting coil of a position indicator and a battery for driving the same are provided, and a connection cable as described above is provided. Although it has already been proposed to eliminate the need for such a battery, it is necessary to replace or charge the battery, which complicates the work, increases the weight of the battery, and increases the operability during the position designation work. Had the disadvantage that it did not improve much.

Further, as another conventional position detecting device,
At one end of the position indicator, an electromagnetic coupling between a plurality of drive lines arranged side by side and sequentially supplied with an alternating current and a plurality of detection lines arranged perpendicularly to the tablet and sequentially detecting an induced voltage is provided. In some cases, the provided magnetic material is changed by bringing the magnetic material into close proximity to or in contact with a tablet, and the induced voltage is changed so that an arbitrary position can be designated. However, in this position detection device, although it is possible to eliminate the battery together with the connection cable as described above from the position indicator, the position is detected even when the position indicator is simply held on the tablet, There is a drawback that an input may be made by mistake.

Furthermore, in order to eliminate the above-mentioned drawbacks of the other conventional position detecting devices, the above-mentioned position-indicating device is only operated when an operator operates the position-indicating device, for example, only when the position-indicating device is pressed against the tablet. There is an LC circuit that changes the inductance of the magnetic material and makes the position detectable (see Japanese Patent Application Laid-Open No. 59-3537). However, no operation is performed by the operator, that is, the position indicator is a tablet. Since the position cannot be detected at all when it is not pressed against the input device, it is not possible to display and confirm the indicated position on the display screen before actually inputting. When using it as input, the positional relationship (distance) with the part already input and displayed on the display screen cannot be confirmed, and input of handwritten characters and handwritten figures as intended There was disadvantage that it can not.

[0006]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and eliminates the need to provide a connection cable between the tablet and the tablet or a battery for driving the oscillator in the position indicator. It is an object of the present invention to provide a position detecting device capable of accurately detecting whether or not the above operation is performed.

[0007]

According to the present invention, in order to achieve the above object, according to the present invention, signals are transmitted and received between a position indicator and a tablet, and coordinates on the tablet indicated by the position indicator are transmitted. A position detecting device that detects a value and an operation state for the position indicator together with the coordinate value,
A first tuning circuit that is normally closed, and a second tuning circuit configured by an operation of an operator and having a different tuning frequency from the first tuning circuit, wherein the first or second tuning circuit is provided. A position indicator that can be arbitrarily or alternatively selected by the operation of the operator, and a plurality of loop coils,
No matter which of the first and second tuning circuits is selected, a radio wave generating means for generating a radio wave of one frequency which can be tuned by the selected tuning circuit, and the first and second tuning circuits A tablet having radio wave detecting means for detecting radio waves having different phases for each of the tuning circuits reflected due to the tuning from a tuning circuit selected by the operation of the operator among the circuits, and comprising the radio wave detecting means Irrespective of whether or not the operation has been performed with a finer accuracy than the arrangement interval of the plurality of loop coils, from the plurality of induced voltages induced by the reflection in the plurality of loop coils, A coordinate calculating means for obtaining a coordinate value of the designated position; and an induced voltage induced in the loop coil constituting the radio wave detecting means in a different phase for each tuning circuit by the reflection. , Radio waves reflected on the tablet from the position indicator is to propose a position detecting device that includes a phase discrimination means for detecting whether a radio wave reflected from any of said first or second tuning circuit.

In a second aspect of the present invention, there is provided a position detecting device according to the first aspect, wherein the radio wave generating means and the radio wave detecting means are operated alternately. According to a third aspect of the present invention, the loop coil constituting the electric wave generating means and the loop coil constituting the electric wave detecting means are combined.
The proposed position detection device is proposed.

According to a fourth aspect of the present invention, a maximum induced voltage is obtained from a plurality of induced voltages induced by reflection in a plurality of loop coils constituting a radio wave detecting means, and the maximum induced voltage and the maximum induced voltage are determined. A function approximating the induced voltage generated in the loop coil located on both sides of the generated loop coil is obtained, the function obtains a coordinate value indicating a maximum value, and the coordinate value is indicated on the tablet of the position indicator by the position indicator. The position detecting device according to any one of claims 1 to 3, further comprising a coordinate calculating means for determining the coordinate value of the position.

[0010]

According to the first aspect of the present invention, when a radio wave of one frequency is generated by the radio wave generating means composed of a plurality of loop coils of the tablet, the radio wave is transmitted to the position pointing device for specifying a position on the tablet. Tuning to a first or second tuning circuit arbitrarily and alternatively selected by an operation of an operator,
That is, although received, the first or second tuning circuit that has received the radio wave transmits or reflects a similar radio wave. The radio wave caused by the tuning reflected from the tuning circuit selected by the operation of the operator among the first and second tuning circuits is detected by radio wave detecting means composed of a plurality of loop coils of the tablet, Further, regardless of whether or not the operation has been performed by the coordinate calculation means, the coordinate value of the position indicated by the position indicator on the tablet is calculated with a finer accuracy than the arrangement interval of the plurality of loop coils, and the phase discrimination is performed. By means, the radio wave reflected from the position indicator to the tablet with a different phase for each tuning circuit from the first tuning circuit or the second tuning circuit is detected as a radio wave reflected from the first or second tuning circuit. It is detected whether an operation has been performed.

According to the second aspect, the radio wave reflected from the tuning circuit is not affected by the radio wave generated in the tablet, and the induced voltage having a different phase for each tuning circuit is guided to the radio wave detecting means of the tablet. be able to. According to the third aspect, it is possible to generate and detect a radio wave with one loop coil.

According to the present invention, the position is indicated by three induced voltages, that is, the maximum induced voltage and the induced voltages generated in the loop coils located on both sides of the loop coil that generated the maximum induced voltage. The coordinates of the position indicated by the container can be obtained.

[0013]

FIG. 1 shows a first embodiment of a position detecting device according to the present invention. In the drawing, reference numeral 10 denotes a position detecting section, 20 is a selection circuit, 30 is a connection switching circuit, 40 is a transmission circuit, and 50 is a transmission circuit. Is a receiving circuit, 60 is a position indicator, and 70 is a processing device.

The position detecting section 10 includes a plurality of, for example, 48 loop coils 11-1 and 11 having conductors parallel to each other.
.., 11-48 are arranged side by side in the direction of arrow A in the figure (hereinafter, referred to as position detection direction). Also,
The loop coils 11-1 to 11-48 are arranged so as to be parallel to each other and overlap each other. Although each of the loop coils 11-1 to 11-48 has one turn here, it may have a plurality of turns if necessary.

As the position detecting section 10, a plurality of parallel conductors formed by, for example, etching a well-known printed circuit board are connected by jumpers or the like to form the plurality of loop coils. Can be used.

The selection circuit 20 is for sequentially selecting one loop coil from the plurality of loop coils 11-1 to 11-48.
8 are connected to one terminal group 21, respectively.
The other end is connected to each of the other terminal groups 22. The selection contact 23 corresponding to the terminal group 21 and the selection contact 24 corresponding to the terminal group 22 operate in conjunction with each other and operate based on information from the processing device 70 to select one loop coil.

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

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

The connection switching circuit 30 is also realized by a known multiplexer.

FIG. 2 shows details of the transmission circuit 40 and the reception circuit 50. In the figure, 41 is an oscillator, 4
2 is a frequency divider, 43 and 44 are NAND gates, 45 is an exclusive-OR (EXOR) gate, and 46 is a drive circuit. Further, 51 is an amplifier, 52 and 53 are phase detectors, and 54 and 55 are low-pass filters (LPFs).

Position indicator (hereinafter referred to as input pen) 6
0 contains a tuning circuit 61 including a coil and a capacitor.

FIG. 3 shows a detailed structure of the input pen 60. A pen shaft 62 made of a non-metallic material such as a synthetic resin is placed inside a pen shaft 62 near a tip thereof. A tuning circuit comprising a ferrite core 64 having a through hole capable of slidably housing the coil, a coil spring 65, a switch 611, a coil 612 wound around the ferrite core 64, capacitors 613 and 614, and a variable capacitor 615. 61 are integrally combined and housed, and a cap 66 is attached to the rear end.

The capacitor 613 and the variable capacitor 61
5 are connected in parallel with each other as shown in FIG. 4, and both ends thereof are connected to a coil 612 to constitute a known parallel resonance circuit. Note that the coil 612 and the capacitor 613
The value of the variable capacitor 615 is selected as a value that resonates (tunes) with the frequency of the radio wave transmitted from each loop coil of the position detection unit 10.

On the other hand, the capacitor 614 is connected to both ends of the coil 612 via the switch 611,
Is turned on, the phase of the current in the parallel resonance circuit is delayed by a predetermined angle. Switch 61
1 presses the tip of the core body 63 against an input surface (not shown) of the position detection unit 10 to
When it is pushed in, it is pushed by its rear end via a coil spring 65 and turned on.

Here, the above-described coil 612 and capacitor
613 and a variable capacitor 615 constitute a first tuning circuit which is normally closed, and a switch 611,
Coil 612, capacitors 613, 614 and variable capacitor
The circuit consisting of 615 is operated (here, the core 63 is connected to the pen shaft 6
2 to turn on the switch 611) to form a second tuning circuit having a tuning frequency different from that of the first tuning circuit. It also includes "the state where no operation is performed.").

The processing unit 70 controls the switching of each loop coil based on the transmission / reception switching signal and the output of the receiving circuit 50 described later, calculates the designated coordinate value, and determines the phase.

Here, the above-described position detecting section 10, selecting circuit 20, connection switching circuit 30 and transmitting circuit 40 constitute a radio wave generating means.
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 phase determining means.

Next, the operation will be described. First, a description will be given of how a radio wave is transmitted and received between the position detecting unit 10 and the input pen 60 and signals obtained at this time with reference to FIG.

In the transmission circuit 40, a clock pulse of, for example, 4 MHz generated by the oscillator 41 is divided by a frequency divider 42.
Is divided into 1/4, 1/8, and 1/256. NAND Gate 4
A pulse signal A of 500 kHz frequency-divided by 1/8 is input to one input terminal of 3, and a transmission / reception switching signal B of 15.625 kHz frequency-divided by 1/256 is input to the other input terminal.
The output is further inverted by the NAND gate 44 and
The signal C is a signal C that outputs or does not output a pulse signal of 500 kHz for each c.

The signal C is converted into a balanced signal by the drive circuit 46, and further the connection switching circuit 30 and the selection circuit 2
0, it is transmitted to one loop coil of the position detecting unit 10, for example, 11-i.
-I generates a radio wave based on the signal C.

At this time, the loop coil 1 of the position detector 10
When the input pen 60 is held substantially upright near 1-i, the radio wave excites the coil 612 of the input pen 60,
An induced voltage D synchronized with the signal C is generated in the tuning circuit 61.

After that, in the signal C, when there is no signal,
That is, when the loop coil 11-i is switched to the receiving circuit 50 at the same time as the reception period starts, the loop coil 11-i
Although the radio wave from i disappears immediately, there is no circuit change in the tuning circuit 61 of the input pen 60, so that the induced voltage D gradually decreases.

On the other hand, the coil 612 generates a radio wave by the current flowing through the tuning circuit 61 based on the induced voltage D.
The electric wave is transmitted to the loop coil 11-connected to the receiving circuit 50.
In order to excite i in reverse, an induced voltage E is generated in the loop coil 11-i.

Since the connection switching circuit 30 is switched by the transmission / reception switching signal B, it takes in the signal from the loop coil 11-i only during the transmission stop period. The received signal E is amplified by the amplifier 51 to become a signal F, which is further transmitted to the phase detectors 52 and 53.

The pulse signal A is input to the phase detector 52 as a detection signal. At this time, if the phase of the received signal F matches the phase of the pulse signal A, the received signal F is just And outputs the inverted signal G. The signal G is converted by sufficiently low low pass filter 54 of the cut-off frequency to a flat signal H of the voltage V _H, is sent to the processor 70.

The phase detector 53 has the same frequency as the pulse signal A produced by inputting the pulse signal A and a pulse signal having a frequency twice that of the pulse signal A to the EXOR gate 45, and the phase is delayed by 90 °. A pulse signal A '(not shown) is input as a detection signal. At this time, if the phase of the received signal F coincides with the phase of the pulse signal A ', a signal I obtained by inverting the received signal F to the minus side is output.
The signal I is converted by sufficiently low low pass filter 55 of the cut-off frequency to a flat signal J of a voltage -V _J, is sent to the processor 70.

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

The input pen 60 has a switch 611.
Is turned on, the tuning circuit 6 is turned on as described above.
The phase of the current at the resonance frequency of 1 is delayed by a predetermined angle with respect to the phase of the voltage. Therefore, the phase of the reception signal F is also delayed by a predetermined angle with respect to the phase of the pulse signal A.
At this time, a voltage appears in both the signals H and J (if the phase delay at this time is 90 °, a voltage appears only in the signal J).

The signals H and J sent to the processing unit 70 are converted into digital signals here, and
The arithmetic processing shown in (1) and (2) is performed.

V _X = (V _H ² + V _J ² ) ^1/2 (1) V _θ = tan ^-1 (V _J / V _H ) (2) where the voltage V _X is the input pen 60 And loop coil 11-
Indicates a value proportional to the distance to i. Further, the voltage _Vθ indicates a value proportional to the phase difference between the voltage and the current in the tuning circuit 61 of the input pen 60.

The value of the voltage V _X varies with switched loop coil 11-i for transmitting and receiving radio waves and the input pen 60, the position of the input pen 60 is detected as described later than this.

The value of the voltage _V θ is on the switch 611,
Since the voltage _Vθ changes only when the switch 611 is turned off, the on / off state of the switch 611 is identified by comparing the voltage _Vθ with a predetermined threshold voltage.

Next, the manner of position detection in the apparatus of the present invention will be described with reference to FIGS.

First, when the power of the entire apparatus is turned on and the measurement is started, the processing apparatus 70 selects the first loop coil 11-1 among the loop coils 11-1 to 11-48 of the position detecting section 10. The information is sent to the selection circuit 20, and the loop coil 11-1 is connected to the connection switching circuit 30.
The connection switching circuit 30 alternately controls the switching of the loop coil 11-1 to the transmission circuit 40 and the reception circuit 50 based on the transmission / reception switching signal B described above.

At this time, during the transmission period of 32 .mu.sec, the transmission circuit 40 operates at a frequency of 16 kHz of 500 kHz as shown in FIG.
The pulse signals are sent to the loop coil 11-1 (only eight of them are shown in FIG. 5 for convenience of the drawing).

As shown in FIG. 6B, the switching between the transmission and the reception is performed for one loop coil, here, 11-1.
Repeated several times. The seven transmission and reception repetition periods correspond to one loop coil selection period (448 μsec).

Induction voltages are obtained from the outputs of the phase detectors 52 and 53 of the reception circuit 50 every seven reception periods for one loop coil. These induction voltages are applied to the low-pass filter as described above. Averaged by 54 and 55,
Sent to 0. 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 11-1 by the above-described arithmetic processing in the processing device 70,
Temporarily stored.

Next, the processing device 70 includes the loop coil 11-2.
Is sent to the selection circuit 20, the loop coil 11-2 is connected to the connection switching circuit 30, and the detection voltage V _X2 is proportional to the distance between the input pen 60 and the loop coil 11-2.
And store the same. Thereafter, the loop coil 11-
3 to 11-48 are sequentially connected to the connection switching circuit 30, and FIG.
The detection voltages V _{X1 to} V _X48 which are proportional to the distance between each loop coil and the input pen 60 as shown in (c) (however, FIG. 6 (c)
Shows only some of them. ) Is stored.

As shown in FIG. 7, the actual detection voltage is generated only at a few loop coils before and after the position (xp) where the input pen 60 is placed as a center.

When the voltage value of the stored detection voltage is equal to or higher than a predetermined detection level, the processing device 70 calculates a coordinate value representing the position of the input pen 60 from these voltage values as described later, and calculates this coordinate value. The data is transferred to a storage unit (not shown).

When the first position detection is completed in this manner, the processing device 70 sets the loop coils 11-1 to 11-1.
Out of 1-48, information for selecting only a certain number of loop coils around the loop coil at which the maximum detection voltage is obtained, for example, only 10 loop coils, is sent to the selection circuit 20,
The detection voltage is obtained in the same manner as described above, the position is detected, the obtained coordinate value is transferred to the storage unit, and the value is updated.

On the other hand, the processing unit 70 detects each of the detection voltages V _X1
With ~V _X48, calculates the detected voltage V _theta proportional to the phase difference between the voltage and current in the tuning circuit 61 of the input pen 60, the detection voltage V _theta constantly compared with a predetermined threshold voltage, the input pen 60 switch 611 on / off.

Here, the processing unit 70 causes the cursor to be displayed at a corresponding coordinate position on a display device (not shown) as a temporary coordinate value when the switch 611 is not operated, that is, when the switch 611 is turned off. The coordinate value when 611 is operated, that is, when the switch is turned on, can be displayed as the coordinate value to be input, for example, the handwriting at the corresponding coordinate position on the display device. While confirming the position of 60, the position to be inputted can be designated by the switch 611.

FIG. 8 shows the timing of the second and subsequent detection operations in the processing device 70. In the figure, the level check is to check whether the maximum value of the detection voltage has reached the detection level, and to check which loop coil has the maximum value of the detection voltage, and to reach the detection level. If not, stop the coordinate calculation,
Also, the center of the loop coil to be selected in the next detection operation is set.

As one method of calculating the coordinate value xp, there is a method of approximating the waveform near the maximum value of the detection voltages V _{X1 to} V _X48 by an appropriate function and obtaining the coordinates of the maximum value of the function.

For example, in FIG. 6C, when the maximum value of the detection voltage V _X3 and the detection voltages V _X2 and V _X4 on both sides thereof are approximated by a quadratic function, it can be calculated as follows. The coordinate values of the center positions of the loop coils 11-1 to 11-48 are x1 to x48, and the interval is Δx.) First, from the voltages and coordinate values, V _X2 = a (x 2 −x p) ² + b (3) V _X3 = a (x ₃ −x p) ² + b (4) V _X4 = a (x 4 −x p) ² + b (5) Here, a and b are constants (a <0). X3−x2 = Δx (6) x4−x2 = 2Δx (7) (6), (7) (4), (5) and rearranging are substituted into equation, xp = x2 + Δx / 2 {(3V X2 -4V X3 + V X4) / (V X2 -2V X3 + V X4) ｝ …… (8)

Therefore, the maximum value detection voltage obtained at the time of the level check and the detection voltages before and after it are extracted from the respective detection voltages V _{X1 to} V _X48 , and these and the maximum value detection voltage are obtained. The coordinate value xp of the input pen 60 can be calculated by performing an operation corresponding to the above-mentioned equation (8) from the coordinate value (known) of the loop coil immediately before the loop coil.

The number and arrangement of the loop coils in the embodiment are merely examples, and it is needless to say that the present invention is not limited to this.

FIG. 9 shows a second embodiment of the present invention. In the figure, reference numerals 81 and 82 denote position detection units in the X and Y directions, reference numerals 83 and 84 denote selection circuits in the X and Y directions, and reference numerals 85 and 86 denote connection switching circuits in the X and Y directions. It has a configuration similar to that of the section 10, the selection circuit 20, and the connection switching circuit 30 (however, details thereof are omitted in the drawings for simplicity). Are superimposed on each other so as to be orthogonal to the X direction and the Y direction, respectively. A processing device 87 is the same as the processing device 70 except that the position detection in the X direction and the Y direction is performed alternately. The processing device 8
FIG. 10 shows the timing of the second and subsequent coordinate detection operations in FIG. As described above, according to the present embodiment, it is possible to easily detect the positions (coordinates) in the two directions of the X direction and the Y direction.
The configurations of the transmission circuit 40, the reception circuit 50, and the input pen 60 may be the same as those in the first embodiment.

The embodiment described so far is the most preferable example of the position detecting device of the present invention. The present invention is not limited to this. For example, a loop coil for generating a radio wave and a loop coil for detecting a radio wave may be used. May be separate,
In this case, the radio wave may be generated at all times.

[0061]

As described above, according to the first aspect of the present invention, a signal is transmitted and received between the position indicator and the tablet, and the coordinate value on the tablet indicated by the position indicator and the position of the tablet are transmitted. What is claimed is: 1. A position detecting device for detecting an operation state of an indicator together with said coordinate values, comprising: a first tuning circuit which is normally closed; and a tuning frequency different from said first tuning circuit which is constituted by an operation of an operator. A second tuning circuit, the first or second tuning circuit is arbitrarily and selectively selectable by an operation of the operator, and is configured from a position indicator, and a plurality of loop coils, Radio wave generating means for generating a radio wave of one frequency to which the selected tuning circuit can tune, regardless of which of the first and second tuning circuits is selected, and the first and second tuning circuits Out of the operator And tablets having a radio wave detection means for detecting a different wave phases for each of the tuning circuit is reflected due to the tuning of the tuning circuit selected Te,
The position indication is performed regardless of whether or not the operation has been performed with a finer accuracy than an arrangement interval of the plurality of loop coils, based on a plurality of induced voltages induced by the reflection in a plurality of loop coils constituting the radio wave detecting means. A coordinate calculating means for calculating a coordinate value of a designated position on the tablet of the tablet, and the position indication from an induced voltage which is induced in a loop coil constituting the radio wave detecting means with a different phase for each tuning circuit by the reflection. Phase determining means for detecting whether the radio wave reflected from the device to the tablet is the radio wave reflected from the first or second tuning circuit, so that the position indicator can be connected to the tablet. Not only does it not require a battery to drive cables or oscillators, but it also generates a radio wave of one frequency from the tablet, and The value can be detected with a finer accuracy than the arrangement interval of each loop coil, that is, with a higher accuracy regardless of whether or not the operator has performed an operation. It is possible to detect whether the radio wave is reflected from any of the second tuning circuits, that is, whether or not the operator has performed an operation. It can be detected along with whether or not the pressing has been performed, and the pointing position can be displayed on the display screen and input while confirming.

According to the second aspect of the present invention, since the radio wave generation means and the radio wave detection means are operated alternately, the radio waves reflected from the tuning circuit are affected by the radio waves generated by the tablet. Instead, an induced voltage having a different phase for each tuning circuit can be induced to the radio wave detecting means of the tablet, and the phase change range can be set large, so that more information can be transmitted.

Further, according to the third aspect of the present invention, the loop coil constituting the radio wave generating means and the loop coil constituting the radio wave detecting means are combined, so that one loop coil can generate and detect a radio wave. Can do
The configuration of the tablet can be simplified.

According to a fourth aspect of the present invention, a maximum induced voltage is obtained from a plurality of induced voltages induced by reflection in a plurality of loop coils constituting the radio wave detecting means, and the maximum induced voltage and the maximum induced voltage are determined. A function that approximates the induced voltage generated in the loop coil located on both sides of the loop coil that generates the maximum induced voltage is obtained, the function obtains a coordinate value indicating a local maximum value, and the coordinate value is obtained by using the position indicator of the position indicator. Since the coordinate calculation means for determining the coordinate value of the indicated position on the tablet is provided, the maximum induced voltage and the induced voltage generated in the loop coils located on both sides of the loop coil that generates the maximum induced voltage are calculated. The coordinate value of the position indicated by the position indicator can be obtained from the two induced voltages, and the coordinate value can be accurately determined only by scanning the loop coil within a narrow range near the indicated position.

[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 illustrating a detailed configuration of a transmission circuit and a reception circuit.

FIG. 3 is a diagram showing a specific configuration of an input pen.

FIG. 4 is a configuration diagram of a tuning circuit.

FIG. 5 is a waveform chart of each part in FIG. 2;

FIG. 6 is a timing chart showing a basic detection operation in the present invention.

FIG. 7 is a diagram showing a detection voltage obtained from each loop coil during a first detection operation;

FIG. 8 is a timing chart showing the second and subsequent detection operations;

FIG. 9 is a configuration diagram showing a second embodiment of the present invention.

FIG. 10 is a view similar to FIG. 8 in a second embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Position detection part, 20 ... Selection circuit, 30 ... Connection switching circuit, 40 ... Transmission circuit, 50 ... Receiving circuit, 60 ... Position indicator, 61 ... Tuning circuit, 70 ... Processing device.

Continuation of front page (72) Inventor Tomoaki Senda 2-510-1, Toyonodai, Otone-cho, Kita-Saitama-gun, Saitama Prefecture Inside Wacom Co., Ltd.

Claims (4)

(57) [Claims] 1. A position detecting device for transmitting and receiving signals between a position indicator and a tablet, and detecting coordinate values on the tablet indicated by the position indicator and an operation state of the position indicator together with the coordinate values. A first tuning circuit that is normally closed, and a second tuning circuit that is configured by an operation of an operator and has a tuning frequency different from that of the first tuning circuit. 2. A position indicator that can select any of the two tuning circuits arbitrarily and alternatively by the operation of the operator, and a plurality of loop coils, and when either the first or the second tuning circuit is selected The radio wave generating means for generating a radio wave of one frequency which can be tuned by the selected tuning circuit and the tuning circuit selected by the operator among the first and second tuning circuits. Due to synchronization A tablet having radio wave detecting means for detecting radio waves having different phases for each of the tuned circuits to be radiated, and a plurality of induced voltages induced by the reflection on a plurality of loop coils constituting the radio wave detecting means, and Coordinate calculation means for obtaining the coordinate value of the position indicated by the position indicator on the tablet regardless of whether the operation is performed with a finer precision than the arrangement interval of the loop coil, and a loop coil constituting the radio wave detection means The radio wave reflected from the position indicator to the tablet is a radio wave reflected from any of the first and second tuning circuits from an induced voltage induced in a different phase for each tuning circuit by the reflection. A position detecting device comprising: a phase discriminating means for detecting whether or not there is an object. 2. The position detecting device according to claim 1, wherein the radio wave generating means and the radio wave detecting means are operated alternately. 3. The position detecting device according to claim 2, wherein the loop coil constituting the electric wave generating means and the loop coil constituting the electric wave detecting means are used in combination. 4. A maximum induced voltage is determined from a plurality of induced voltages induced by reflection on a plurality of loop coils constituting a radio wave detecting means, and the maximum induced voltage and the loop coil generating the maximum induced voltage are determined. A function approximating the induced voltage generated in the loop coil located on both sides is obtained, the function obtains a coordinate value indicating a local maximum value, and the coordinate value is determined as the coordinate value of the position indicated on the tablet of the position indicator. The position detecting device according to claim 1, further comprising a coordinate calculating unit that performs the calculation.