JPH02212917A - Position detector - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a position detection device that is resistant to external noise and the like.

(Prior Art) Prior to filing this application, the applicant filed Japanese Patent Application No. 61-213970.
No. 63-70326 (hereinafter referred to as the prior application), radio waves are sent and received between an input indicator and a tablet, and the position indicated by the input indicator is detected. proposed a position detection device.

The content of this prior application will be briefly explained. First, an alternating current signal of a predetermined frequency is applied to the loop coil on the tablet side to transmit radio waves, and the radio waves are received by a tuning circuit provided in the input indicator. At this time, a loop coil on the tablet side receives radio waves transmitted from a tuned circuit that receives the radio waves, and an induced voltage is generated in the loop coil. This is sequentially switched and repeated for a plurality of loop coils, and the position indicated by the input indicator is detected based on the induced voltage generated in each loop coil.

(Problems to be Solved by the Invention) However, since the device uses an analog switch to switch the loop coil, the amount of current that can be passed through the loop coil is limited. Therefore, the radio waves emitted from the loop coil were weak, the intensity of the radio waves emitted from the tuning circuit of the input indicator was also weak, and the voltage induced in the loop coil on the tablet side was also small. Therefore, if other radio waves are mixed in from the outside, there is a problem that the position detection accuracy decreases or malfunctions occur, making it impossible to detect the position.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and provide a device capable of detecting a position with high accuracy even when there are other radio waves mixed in from the outside.

(Means for Solving Three Problems) In order to achieve the above object, the present invention transmits and receives radio waves between a manual indicator having a tuning circuit and a tablet having a plurality of loop coils, and the input indicator A position detection device that detects a position indicated by a circuit, which has separate loop coils for transmitting radio waves and loop coils for receiving radio waves, and that is capable of supplying a large current to the loop coil for transmitting radio waves. We propose a position detection device that is driven by

(Function) According to the present invention, a large current is supplied to the loop coil for transmitting radio waves on the tablet side from a circuit capable of supplying a large current, so that high-intensity radio waves are transmitted. At this time, a large induced voltage is generated in the tuned circuit of the input indicator that receives the radio wave, so the tuned circuit of the input indicator transmits a radio wave with a higher intensity than the radio waves mixed in from the outside. Ru.

Therefore, a large induced voltage depending on the radio waves transmitted from the tuning circuit of the input indicator is generated in the loop coil that receives the radio waves from the tablet side.

(Embodiment) FIG. 1 shows a first embodiment of the position detection device of the present invention, in which 1 is a position detection section, 2 is a selection drive section, 3 is a selection amplification section, and 4 is a control section. , 5 is a manual pen.

The position detection unit 1 includes a large number of conductors parallel to each other, for example, 48 loop coils 1, 1, 11-2, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, , , , , , , 1, 1, , , , , , , 1, 1, , , , , , , , , , , ,
. . . 11-48, and a large number of receiving loop coils 12, for example 48, which also have conductors parallel to each other.
-1.12-2. It consists of 12-48. The loop coils im-] to 11-48 are arranged parallel to each other and spaced apart by a predetermined interval in the direction of arrow A (hereinafter referred to as position detection direction) in the figure. Further, each of the loop coils 12-1 to 12-48 is arranged in parallel around each of the loop coils 11-1 to 11-48, respectively.

Here, each of the loop coils 11-1 to 11-48 and 12-1 to 12-48 is configured with one turn, but may be configured with multiple turns if necessary. In addition, each loop coil 1 is placed around each loop coil 11-1 to 11-48.
Although 2-1 to 1.2-48 are arranged, they may be reversed.

In addition, each loop coil 11-1 to 11-48 and 12-
1 to 12-48 are arranged side by side at a predetermined interval, but they may be arranged so as to overlap each other. Furthermore, although the number of loop coils for transmitting and the number of loop coils for receiving are made equal to each other, they may be different.

The selection drive unit 2 includes the transmission loop coils 11-1 to 11-1.
The loop coils 11-48 to 11-48 are sequentially selected and a current is supplied to drive them.
current drivers 21-1. ．． 21-2.・・・・・・
21-48 and a well-known multiplexer 22.

The front five loop coils are connected to each output terminal of the current drivers 21-1 to 21-48, and the other end is grounded. Also,
Each input terminal of current drivers 21-1 to 21-48 is connected to 48 output terminals of multiplexer 22, respectively. Further, the multiplexer 22 outputs an AC signal manually input from the control section 4 via the - input terminal from any one of the output terminals according to selection information also input from the control section 4.

The selective amplification section 3 includes the receiving loop coils 12-1 to 12-1.
It sequentially selects the loop coils 12-48 and amplifies their output voltages, and consists of a well-known analog switch 31 and a voltage amplifier 32.

The selection terminal of the analog switch 31 is connected to the lube coil 1.
2-1 to 12-48 are connected, and the loop coils 12 to 1 to 12- are connected according to selection information input from the control unit 4.
48 is connected to amplifier 32. The voltage amplifier 32 is connected to the loop coils 12-1 to 12-48.
The induced voltage generated is amplified and output to the control section 4.

The aforementioned position detection section 11 selection drive section 2 and selection amplification section 3
is housed together with the control unit 4 in a case (not shown) made of a non-metallic material such as synthetic resin, and constitutes a tablet.

The input vent 5 constitutes an input indicator and has a built-in tuning circuit 51 including a coil and a capacitor.

FIG. 2 shows the detailed structure of Ben 5, in which a core 53 of a ballpoint pen or the like is slid inside a pen shaft 52 made of a non-metallic material such as synthetic resin from near its tip. A ferrite core 54 with a through hole that can be freely accommodated, a coil spring 55, and a switch 511 Ferrite core 5
Coil 512.4 wound around coil 512.4. capacitor 513
and a tuning circuit 51 consisting of No. 51 are integrally combined and built in, and a cap 56 is attached to the rear end.

As shown in FIG. 3, the coil 512 and capacitor 513 are connected in series to form a well-known resonant circuit.
The numerical value 3 is set to a value such that the phases of the voltage and current resonate (synchronize) in the same phase at a predetermined frequency fO. Further, a capacitor 514 is connected in parallel to both ends of the capacitor 513 via a switch 511.
When 11 is turned on, the tuning frequency in the above-mentioned resonant circuit is slightly lowered, and the phase of the received signal, which will be described later, is delayed by a predetermined angle, for example, 45 degrees. Note that when the switch 511 is operated by holding the pen barrel 52 by hand or the like and pushing the tip of the core body 53 into the pen barrel 52 by pressing it against the input surface (not shown) of the tablet, the coil spring 55 is activated by the rear end. It is turned on by being pressed through the switch.

Figure 13 shows the details of the control unit 4 as well as the overall configuration of the device. In the figure, 401 is a microprocessor, 402 is a signal generation circuit, and 403 is a low-pass filter (LPF).
, 404 is a transmission timing switching circuit, 405 is a reception timing switching circuit, 4'08 is a bandpass filter (BPF),
407 is a detector, 408 and 409 are phase detectors (P
S D ), 410 , 411 , 412 are low pass filters (LPF).

Next, the operation of the device will be explained along with its configuration.
First, we will explain how radio waves are transmitted and received between the position detection unit 1 and the input vent 5, and the signals obtained at this time.
This will be explained according to the diagram.

When the microprocessor 401 controls the signal generation circuit 402, it also controls switching of each loop coil of the position detection section 1 via the selection drive section 2 and the selection amplification section 3 according to the flowchart shown in FIG. Low pass filters 410-41
．． 2, converts the output value from analog to digital (A/D), executes the arithmetic processing described later to calculate the coordinates of the position indicated by the input sensor 5, and detects the phase of the received signal described above. is sent to a host computer (not shown).

The signal generation circuit 402 has a predetermined frequency fO1, for example, 500.
kHz rectangular wave signal A, the phase to the rectangular wave signal is 901
Delayed signal B1 predetermined frequency fk, for example 15.82
Generates a 5kHz transmit timing signal C and a receive timing signal. The rectangular wave signal A is passed through a phase detector 40.
8 and is converted into a sine wave signal E by a low-pass filter 403 and sent to the selection drive unit 2. Further, the rectangular wave signal B is sent to a phase detector 409. Furthermore, the transmission timing signal C is transmitted by the transmission timing switching circuit 40.
Further, the reception timing signal is sent to the reception timing switching circuit 405.

The transmission timing switching circuit 404 receives the above-mentioned sine wave signal E.
is sent to the selection drive section 2 at a predetermined timing, and when the transmission timing signal C is at a high (H) level, it outputs a sine wave signal E, and when it is at a low (L) level, it outputs nothing. do not. Therefore, the transmission timing switching circuit 4
The signal outputted from 04 to the selection drive section 2 is generated at a time T (-
1/2 fk), here 500k every 32μsec
This becomes a signal F that may or may not emit a Hz signal.

The signal F is passed through the multiplexer 22 to a negative current driver 21-i (1s-1+ 2 + . . .
48), the current driver 21-1 sends out a large current having a current value based on the voltage value of the signal F to the - transmission loop coil 11-1 of the position detection unit 1. Therefore, at this time, the loop coil 11-i generates a strong radio wave according to the signal F.

At this time, if the input vent 5 is held in a substantially upright state, that is, in a used state, near the loop coil 11-i of the position detection unit 1, the radio wave excites the coil 512 of the input vent 5, and its tuned circuit At 51, an induced voltage G synchronized with the signal F is generated. Since the magnitude of the induced voltage generated in the tuned circuit 51 is proportional to the intensity of the radio waves that excites the coil 512, the induced voltage G becomes large.

Thereafter, when the signal F enters a no-signal period, ie, a reception period, the radio wave from the loop coil 11-f immediately disappears, but the induced voltage G gradually attenuates in accordance with the loss within the tuning circuit 51.

On the other hand, the large current flowing through the tuning circuit 51 based on the large induced voltage G causes the coil 512 to emit radio waves with greater intensity. Since the radio wave excites the receiving loop coil 12-1 connected to the selective amplification section 3, a large induced voltage due to the radio wave from the coil 512 is generated in the loop coil 12-1. The induced voltage is applied to the analog switch 3
1 to the voltage amplifier 32 , where it is amplified to become a reception signal H (approximately the same waveform as signal G), and further sent to the reception timing switching circuit 405 .

The reception timing switching circuit 405 is for sending the above-mentioned reception signal H to the bandpass filter 408 at a predetermined timing. During the period, the received signal H is output, and during the period when the level is low, nothing is output. Therefore, the signal I is obtained at its output.

The signal I is sent to the bandpass filter 4 (18), and the bandpass filter 40G is a filter having a pass band centered at the frequency fO, and has an amplitude depending on the energy of the acid component at the frequency fO in the signal I. The signal J (strictly speaking, in the state where several signals I are input to the bandpass filter 408 and converged) is passed through the detector 407 and the phase detector 408.
, 409.

The signal J input to the detector 407 is rectified into a signal, and then passed through a low-pass filter 410 with a sufficiently low cut-off frequency to a voltage value corresponding to approximately 1/2 of the amplitude of the signal J. For example, it is converted into a DC signal having VX and sent to the microprocessor 401.

The voltage value VX of the signal is a value that depends on the distance between the input pen 5 and the receiving loop coil 12-1, and here is a value that is approximately inversely proportional to the fourth power of the distance.
-1 changes when switched, so each loop coil 1
The coordinate values of the position indicated by the input pen 5 are calculated by converting the voltage values VX obtained every 2-1 to 12-48 into digital values and performing arithmetic processing to be described later on these values.

On the other hand, the rectangular wave signals A and B are input to the phase detectors 408 and 409 as detected signals, and at this time, assuming that the phase of the signal J almost matches the phase of the rectangular wave signal A°, The phase detector 40g outputs a signal Ml (substantially the same as the signal) which is the inversion of the signal J to the positive side, and the phase detector 409 outputs a signal M2 having a symmetrical waveform on the positive and negative sides. Output.

The signal Ml is filtered by a low-pass filter 411 similar to the one described above, and is converted into a DC signal N1. (substantially the same as the signal M) and sent to the microprocessor 401, and the signal M
2 is converted into a DC signal N2 by a similar low-pass filter 412 and sent to the microprocessor 401, but here, since the positive and negative components of the signal M2 from the phase detector 409 are the same, the low-frequency The voltage value of the output of the filter 412 is 0 [V].

The microprocessor 401 A/D converts the output values of the low-pass filters 411 and 412, here signals N1 and N2, and further uses these digital values to perform calculation processing according to the following equation (1), and then outputs the output values from the phase detectors 408 and 412. The phase difference θ between the signal added to 409, here J, and the rectangular wave signal is calculated.

θ--tan” (VQ/VP)
="(1) However, VP is the digital value corresponding to the output of the low-pass filter 411, and VQ is the digital value corresponding to the output of the low-pass filter 411.
The digital value corresponding to the output of 2 is shown. For example, in the case of the U-J mentioned above, the voltage value of the signal Nl is VW, but
Since the voltage value of the signal N2 is O[V], that is, VQ-0, the phase difference is θ-06.

By the way, the phase of the signal J is determined by the tuning circuit 5 of the input bench 5.
The tuning frequency at 1 varies depending on the tuning frequency. That is, when the tuned frequency in the tuned circuit 51 matches the predetermined frequency fO, an induced voltage of frequency [O is generated in the tuned circuit 51 during both the signal transmission period and the signal reception period, and an induced voltage synchronized with this Since a current flows, the frequency and phase of the received signal I match those of the rectangular wave signal A, and the phase of the signal J also matches those of the rectangular wave signal A.

On the other hand, if the tuned frequency in the tuned circuit 51 does not match the predetermined frequency fO, for example, if the frequency f1 is slightly lower than the frequency fO, an induced voltage of the frequency fO is generated in the tuned circuit 51 during the signal transmission period. However, at that time, an induced current with a phase delay flows through the tuned circuit 51, and an induced voltage of approximately frequency fl and an induced current synchronized with this flow during the signal reception period, so that the frequency of the received signal l is is slightly lower than the frequency of the rectangular wave signal A, and its phase is also slightly delayed. As mentioned above, since the bandpass filter 40B passes only the frequency fO, a shift in the frequency of the input signal toward the lower side is outputted as a phase delay.

Conversely, if the tuning frequency in the tuning circuit 51 is slightly higher than the predetermined frequency fO, for example f2,
During the signal transmission period, the tuning circuit 51 receives the frequency fO.
An induced voltage of f2 is generated, but at that time, an induced current with a phase lead flows through the tuned circuit 51, and an induced voltage of approximately frequency f2 and an induced current synchronized with this flow during the signal reception period. The frequency of the received signal I is slightly higher than the frequency of the rectangular wave signal A, and its phase is also slightly advanced. In the bandpass filter 406, a shift in the frequency of the input signal toward the higher side is outputted as a phase advance, contrary to the case described above.

As described above, since the tuning frequency of the tuning circuit 51 changes depending on the state of the switch 511, the phase difference θ determined by the above equation <1) also changes depending on the state of the switch 511. In this embodiment, the switch 511 of the input vent 5
The phase difference θ is set in advance to be O# in the off state and -45° in the on state. Therefore, by determining whether the phase difference θ is 06 or -45@, it is possible to accurately identify whether the switch 511 is on or off.

Note that the phase difference θ is actually sent as is to the host computer along with the coordinate values of the position indicated by the input bench 5, and is converted into information indicating the on or off state of the switch 511 described above on the host computer side. Ru.

Further, the information indicating the on or off state of the switch 511 identified here is used as information for specifying the value to be actually input among the coordinate values of the position indicated by the input ben 5.

Next, the position detection operation and phase detection operation in the apparatus of the present invention will be explained in detail according to FIGS. 5 to 8.

First, when the power of the entire apparatus is turned on and measurement starts, the microprocessor 401 selects the first loop coil 11-1 of the transmitting loop coils 11-1 to 11-48 of the position detecting section 1 and the receiving loop coil 11-1. loop coil 12-1
Information for selecting the first loop coil 12-1 out of ~12-48 is sent to the selection drive section 2 and the selection amplification section 3, respectively, and the loop coils 11-1 and 12-1 are sent to the transmission timing switching circuit 404 and the reception timing switching circuit 404. Timing switching circuit 40
5 respectively.

The transmission timing switching circuit 404 and the reception timing switching circuit 405 alternately connect the loop coils 11-1 and 12-1 to the low-pass filter 403 and the bandpass filter 408 based on the above-mentioned transmission timing signal C and reception timing signal. .

At this time, the current driver 21-1 in the selection drive unit 2 is 32
During the μSee transmission period, 16 sine wave signals of 500 kHz as shown in Fig. 6(a) are generated (only 5 of them are shown in Fig. 4 for convenience of drawing).
A large current according to the following is sent to the loop coil 11-1.

The switching between transmission and reception is as shown in FIG. 6(b).
Loop coil for transmitting and receiving, here 11-1
and repeated 7 times for 12-1. These seven transmission and reception repetition periods correspond to the selection period (448 usec) of the loop coils for transmission and reception.

At this time, the output of the reception timing switching circuit 405 is -
An induced voltage is obtained for the reception loop coil every seven reception periods, and as described above, this induced voltage is averaged by the bandpass filter 40B, and the wave detector 407, phase detector 408, 4 .09 and low pass filter 410-4
12 and sent to the microprocessor 401.

The microprocessor 401 A/D converts the output value of the low-pass filter 410 and converts it into a detected voltage depending on the distance between the input vent 5 and the receiving loop coil 12-1, for example, Vx.
Temporarily stored as l.

Next, the microprocessor 401 controls the loop coil 11-
The information for selecting the loop coils 11-2 and 12-2 is sent to the selection drive section 2 and the selection amplification section 3.
is connected to the transmission timing switching circuit 404 and the reception timing switching circuit 4.05, and the input vent 5 and the loop coil 1
2-2 is obtained and stored, and thereafter the loop coils 11-3 to 11-4 are
8 and 12-3 to 12-48 are sequentially connected to the transmission timing switching circuit 404 and the reception timing switching circuit 405, and the input vents 5 and 5 for each receiving loop coil are connected as shown in FIG. 6(C). Distance-dependent detection voltage Vxl ~
Vx4g (however, only a part of it is shown in analog representation in FIG. 6(c)).

As shown in FIG. 7, the actual detected voltage is obtained only in several loop coils around the position (xp) where the input vent 5 is placed.

The microprocessor 401 checks whether the voltage value of the stored detection voltage is above a certain detection level. At this time, if it is below a certain detection level, the selection of the loop coils for each transmission and reception and the detection of the induced voltage are repeated again, and if it is above a certain detection level,
From the stored voltage value, the coordinate values of the position indicated by the input sensor 5 are calculated as will be described later.

Next, the microprocessor 401 executes the loop coil 1
Sending information for selecting the loop coil set from which the maximum detected voltage was obtained from the sets of 1-1 to 11-48 and 12-1 to 12-48 to the selection drive unit 2 and the selection amplification unit 3; The transmission and reception of the radio waves is repeated a plurality of times, for example, 7 times, and at that time, the output values obtained from the low-pass filters 411 and 412 are A/D converted, and the arithmetic processing of the above formula (1) is performed on them. , calculate the phase difference θ.

The microprocessor 401 then transfers the phase difference θ together with the coordinate values of the position indicated by the input valve 5 to the host computer.

When the first position detection operation and phase detection operation are completed in this way, the microprocessor 401 performs the second and subsequent position detection operations on the loop coils 11-1 to 11-48 as shown in FIG. and 12-1 to 12-
Among the 48 sets, the selection drive unit 2 selects information for selecting only a certain number of loop coil sets before and after the loop coil set for which the maximum detected voltage was obtained, for example, 10 loop coil sets.
and the selective amplification section 3, obtain an output value in the same manner as described above, perform a position detection operation and a phase detection operation on the input Ben 5, transfer the obtained coordinate values and phase information of the indicated position to the host computer, Repeat these steps below.

Therefore, when the input bezel 5 is operated on the position detecting section 1, all the coordinate values of the position indicated by the input bezel 5 during that time are transferred to the host computer. Also, at this time, switch 5
When 11 is turned on, the -45° phase information is transferred to the host computer, so that the host computer can recognize the coordinate values at this point as, for example, the coordinate values to be input.

To explain the level check mentioned above in detail, it checks whether the maximum value of the detected voltage has reached the detection level and which loop coil set has the maximum detected voltage. , if the detection level has not been reached, the subsequent coordinate calculations, etc. are stopped, and the center of the set of loop coils to be selected in the next position detection operation and phase detection operation is set.

One method of calculating the coordinate value xp is to approximate the waveform near the maximum value of the detected voltages Vxl to Vx4g by an appropriate function, and calculate the coordinates of the maximum value of the function.

For example, in FIG. 6(C), the maximum detection voltage Vx3
By approximating the detected voltages Vx2 and Vx4 on both sides thereof using a quadratic function, it can be calculated as follows (however, the coordinate values of the center positions of the loop coils 12-1 to 12-48 for each reception is xi −x4g, and the interval is ΔX
shall be. ). First, from each voltage and coordinate value, Vx2- a (x2- xp) 2+ b
---(2>Vx3=a (x3-xp) 2+b
=-(3)Vx4=a (x4-xp) 2+
b -------(4). Here, a, b
is a constant (a < 0).

Also, x3−x2−ΔX −−−−−−(
5) x4-x2-2ΔX ------
−(8). (5), ([i) equation (3), (
4) Substituting into the formula and rearranging it, we get xp -x'l +Δx/2 ((3Vx2-4VX
3+Vx4) / (Vx2-2VX3+VX4))
・・・・・・(7)

Therefore, from each detection voltage Vxl to V The coordinate value xp of the position indicated by the input pen 5 can be calculated by performing an operation corresponding to the above-mentioned equation (7) from the coordinate value (known) of the receiving loop coil immediately before the loop coil.

FIG. 9 shows a second embodiment of the present invention, in which an example is shown in which position detection is performed in the X direction and the Y direction. That is,
In the figure, reference numeral 1a denotes a position detecting section in the X direction and the Y direction, which consists of two sets of the position detecting sections 1 in the first embodiment, superimposed so that their loop coils are orthogonal to each other. In addition, 2a and 2b JiX direction and Y direction selection drive units,
3a and 3b are selective amplification sections in the X direction and Y direction;
Each has the same configuration as the selection drive section 2 and the selection amplification section 3 in the first embodiment.

Further, 404a and 404b are transmission timing switching circuits in the X direction and Y direction, which change the sine wave signal inputted from the signal generation circuit 402 via the low-pass filter 403 based on the transmission timing signal and position detection direction selection information. This is to be added to either the selection drive section 2a or 2b.

Further, 405a is a reception timing switching circuit, which selectively sends the reception signal from the selective amplification section 3a or 3b to the bandpass filter 40B based on the reception timing signal and the selection information of the position detection direction. .

Further, 40La is a microprocessor, which controls the transmission timing switching circuits 404a, 404b and the reception timing switching circuit 405a, and performs position detection in the X direction and the Y direction alternately. This is similar to 401. The flow of processing in the microprocessor 401a is shown in FIG.
Further, the timing of the second and subsequent position detection operations and phase detection operations is shown in FIG.

As described above, according to this embodiment, the position i! in the two directions of the X direction and the Y direction with respect to the input bench 5! (coordinates) can be detected easily. Note that the other configurations and operations are the same as those of the first embodiment.

(Effects of the Invention) As explained above, according to the present invention, radio waves are sent and received between an input indicator having a tuned circuit and a tablet having a plurality of loop coils, This is a position detection device that detects a position, and has separate loop coils for transmitting radio waves and loop coils for receiving radio waves, and the loop coil for transmitting radio waves is driven by a circuit capable of supplying a large current. Therefore, the strength of the radio waves transmitted from the tablet side can be increased, and as a result, the strength of the radio waves reflected from the tuning circuit of the input indicator can also be increased, and the loop coil that receives the radio waves from the tablet side can be connected to the input indicator. A large induced voltage can be generated by radio waves from a tuned circuit. Therefore, even if noise induced by other radio waves occurs, position detection accuracy will not be reduced or malfunctions will occur.As a result, the readable height can be improved and display devices driven by high voltage It has advantages such as being able to be used in combination with the backlight.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing a first embodiment of the position detection device of the present invention, FIG. 2 is a sectional view of an input pen, FIG. 3 is a diagram showing details of the control section and the overall configuration of the device, and FIG. Figure 4 is the third
Signal waveform diagrams of each part in the figure, Figure 5 is a flowchart of processing in the microphone a processor, and Figures 6 (a), (b), and (c) are timings showing the basic position detection operation in the first embodiment. 7 is a diagram showing the detection voltage obtained from each loop coil during the first position detection operation, and FIG. 8 is a timing diagram showing the position detection operation and phase detection operation from the second time onward. 9 is a diagram similar to FIG. 3 showing a second embodiment of the position detection device of the present invention, FIG. 10 is a diagram similar to FIG. 5 in the second embodiment of the present invention, and FIG. 11 is a diagram similar to FIG. FIG. 8 is a diagram similar to FIG. 8 in a second embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Position detection part, 2... Selection drive part, 3... Selection amplification part, 4... Control part, 5... Input pen, 11-
1 to 11-48...Loop coil for transmission, 12-1
~12-48...Loop coil for reception, 21-1~
21-48... Current driver, 51... Tuning circuit. Figure 1: Cross-sectional view of the input pen Figure 20: Flowchart of processing in the micro-prosthesis Figure 10: Similar diagram to Figure 5 in the second embodiment

Claims (1)

[Scope of Claims] A position detection device that transmits and receives radio waves between an input indicator having a tuned circuit and a tablet having a plurality of loop coils, and detects a position indicated by the input indicator. , A position detection device characterized in that it has separate loop coils for transmitting radio waves and loop coils for receiving radio waves, and the loop coil for transmitting radio waves is driven by a circuit capable of supplying a large current.