JPS63276621A - Position detector - Google Patents

Abstract

PURPOSE:To detect a position with high accuracy by providing a selecting circuit of coils arranged in the position detecting direction, a transmitting circuit of a prescribed frequency, a receiving circuit and a transmission/reception switching circuit,a position indicator for setting the prescribed frequency to a tuning frequency, and an arithmetic processor. CONSTITUTION:One of coils 11 is selected by a selecting circuit 2 and connected to a transmitting circuit 5 by a transmission/reception switching circuit 3, a current being proportional to an AC voltage of a prescribed frequency (f) is allowed to flow and a radio wave is generated. In a coil 41 of a position indicator 4, an inducted voltage is generated. When the coil 11 is switched to a receiving circuit 6, the induced voltage is brought to an electric conduction to the receiving circuit and attenuated. A current of the coil 41 generates a radio wave of the same frequency as a current of the coil 11 and excites in reverse the coil 11, therefore, a similar induced voltage is generated in the coil 11. An induced voltage value depends on only a distance of the coil 11 and the coil 41 of the position indicator 4 and the nearer the distance is, the higher the value is. By calculating the induced voltage value by a processor 7, the maximum value of the voltage value, namely, a coordinate of the position indicator 4 is derived. Also, in the X and Y directions, an induced voltage based on the resonance of the coil 11 and the coil 41 of the position indicator is derived, and a coordinate of a two-dimensional designated position can also be derived.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a position detection device for detecting a specified position of a cordless position indicator.

(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. There was something I did.

In addition, as other conventional position detection devices, a plurality of drive lines and detection lines are arranged perpendicularly to each other, and a current is sequentially passed through the drive lines and the detection lines are sequentially selected to detect the induced voltage. There is a device in which a position specified by a position indicator having a magnetic material such as the above is detected from the position of a detection line where a large induced voltage is 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. Handling is severely restricted and the position indicator must be held perpendicular to the magnetostrictive transmission medium and used in close proximity.

In addition, although the position indicator can be made cordless in the latter device, the resolution of the coordinate position is determined by the line spacing,
If the distance between the lines is reduced in order to increase the resolution, the signal-to-noise ratio and stability will deteriorate, and therefore it is difficult to increase the resolution, and it is also difficult to detect the position directly above the intersection of the drive line and the detection line. Another problem was that the position indicator had to be placed very close to the line.

SUMMARY OF THE INVENTION An object of the present invention is to provide a device in which a position indicator is not connected anywhere, has good operability, and can detect the designated position of the position indicator with extremely high accuracy.

(Means for Solving the Problems) In order to solve the above problems, as a first invention, a position detection unit is provided in which a large number of loop coils are arranged in parallel in the position detection direction;
a selection circuit that sequentially selects one loop coil from the plurality of loop coils, a transmission circuit that drives the selected one loop coil with a current signal proportional only to an alternating current voltage of a predetermined frequency, and a coil and a capacitor. a position indicator whose tuning frequency is the predetermined frequency; a receiving circuit which detects an induced voltage having a frequency substantially the same as the predetermined frequency among the voltages generated in the selected one loop coil; and the selected one. A position detection device comprising: a transmission/reception switching circuit that alternately connects one of the loop coils to the transmission circuit and the reception circuit; and a processing device that calculates the specified position of the position indicator from the induced voltage generated in each loop coil. suggest,
Further, as a second invention, there is provided an X-direction and Y-direction position detecting section in which a plurality of loop coils are arranged in parallel in the X-direction and the Y-direction, respectively; an X-direction and Y-direction selection circuit that sequentially selects one loop coil in the Y direction;
a transmission circuit that drives one loop coil in the direction and the Y direction with a current signal proportional only to an alternating current voltage of a predetermined frequency;
a position indicator that includes a coil and a capacitor and has the predetermined frequency as a tuning frequency;
A receiving circuit detects an induced voltage of approximately the same frequency as the predetermined frequency among voltages generated in one loop coil in the direction, and a receiving circuit that connects the selected one loop coil in the X direction and the Y direction to the transmitting circuit and the receiving circuit. The position indicator's
We propose a position detection device that includes a processing device that calculates a designated position in the direction and the Y direction.

(Function) According to the first invention, one of the many loop coils is selected by the selection circuit, a transmission circuit is connected to it by the transmission/reception switching circuit, and the voltage is proportional only to the alternating current voltage of a predetermined frequency. When a current signal is applied, radio waves are generated from the loop coil. The radio wave excites the coil in the tuned circuit of the position indicator that specifies the position on the position detection unit,
The tuned circuit generates an induced voltage synchronized with the current signal. Thereafter, when a receiving circuit is connected to the selected one loop coil by the transmission/reception switching circuit and the current signal is cut off, the radio wave disappears, but the induced voltage generated in the tuned circuit of the position indicator remains in the selected loop coil. As the current flows through the circuit, it gradually attenuates based on internal losses. The current flowing through the tuned circuit causes the coil in the tuned circuit to generate radio waves having approximately the same frequency as the frequency of the current signal applied to the one loop coil. Since the radio waves reversely excite the first loop coil connected to the receiving circuit, an induced voltage similar to the induced voltage in the tuned circuit is generated in the first loop coil. The transmission and reception of the radio waves is repeated sequentially by switching the loop coils, but this is done by resonance between the loop coil and the coil of the position indicator, and the current signal flowing through each loop coil is proportional only to the AC voltage of a predetermined frequency. The voltage value of the induced voltage depends only on the distance between the loop coil and the coil of the position indicator, and the smaller the distance, the larger the voltage value of the induced voltage is.

Therefore, the induced voltage generated in the loop coil closest to the position where the position indicator is placed (designated position) is the maximum, and the induced voltage that gradually decreases as the distance from the designated position increases is generated in each loop coil.

The voltage value of each of the induced voltages is processed by a processing device, and the coordinate values of the position where the voltage value becomes the maximum value, that is, the designated position of the position indicator, are determined.

Note that even if the position indicator is moved along the direction perpendicular to the position detection direction, the distance between each loop coil and the position indicator does not change, so the same coordinate values can be obtained.

Further, according to the second invention, in the X direction and the Y direction,
An induced voltage based on the resonance between the loop coil and the coil of the position indicator is determined, and from this, the coordinate values of the so-called two-dimensional specified position of the position indicator in the X direction and the Y direction are determined.

(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 circuit, 3 is a transmission/reception switching circuit, and 4 is a position indicator. , 5 is a transmitting circuit, 6 is a receiving circuit, and 7 is a processing device.

The position detection unit 1 includes a plurality of loop coils 11-1, 11-2, and 48 loop coils, for example, having conductors parallel to each other.・・・・・・
. . 11-48 are arranged in parallel in the direction of arrow A (hereinafter referred to as position detection direction) in the figure. Further, the loop coils 11-1 to 11-48 are arranged parallel to each other and overlapping each other. Although each of the loop coils 11-1 to 11-48 is configured with one turn here, it may be configured with multiple turns if necessary. The position detection section 1
For example, a plurality of loop coils can be used by connecting a large number of parallel conductors formed by etching a well-known printed circuit board with jumper wires or the like.

The selection circuit 2 includes the plurality of loop coils 11-1 to 11.
One end of the loop coils 11-1 to 11-48 is connected to one terminal group 21, and the other end is connected to another terminal group 22, respectively. It is connected. A selection contact 23 corresponding to the terminal group 21 and a selection contact 24 corresponding to the terminal group 22
are interlocked with each other, operate based on information from the processing device 7, and select one loop coil. The selection circuit 2 is realized by combining a large number of well-known multiplexers.

The transmission/reception switching circuit 3 alternately connects one loop coil selected by the selection circuit 2 to the transmission circuit 5 and the reception circuit 6, and the selection contacts 23 and 24 of the selection circuit 2 are connected to the selection contact 31. and 32, respectively. Further, the two output terminals of the transmitting circuit 5 are terminals 33.
35, and the two input terminals of the receiving circuit 6 are connected to terminals 34, 36. Said terminal 33°34
The selection contacts 31 corresponding to the terminals 35 and 32 and the selection contacts 32 corresponding to the terminals 35 and 36 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 transmission/reception switching circuit 3 is also realized by a well-known multiplexer.

The position indicator 4 is a stylus pen (hereinafter simply referred to as a pen), and has a built-in tuning circuit 41 including a coil and a capacitor.

FIG. 2 shows the detailed structure of the pen 4, in which a core 43 of a ballpoint pen or the like is slid into a pen shaft 42 made of a non-metallic material such as synthetic resin from near the tip. A ferrite core 44 with a through hole that can be freely accommodated, a coil spring 45, and a switch 411. Ferrite core 44
A coil 412. A tuning circuit 41 consisting of capacitors 413 and 414 is integrated and built in, and a cap 46 is attached to the rear end.

As shown in FIG. 3, the coil 412 and capacitor 413 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 414 is connected in parallel to both ends of the capacitor 413 via a switch 411.
When 11 is turned on, it delays the phase of the current in the above-mentioned resonant circuit and delays the phase of the received signal, which will be described later, by a predetermined angle. Note that the switch 411 is connected to the pen barrel 4.
2 is held by hand or the like, and when the tip of the core body 43 is pushed into the pen barrel 42 by pressing it against the input surface (not shown) of the position detection unit 1, the pen body 43 is pressed by the rear end via the coil spring 45. , it's like it's on.

FIG. 3 shows the details of the tuning circuit 41, the transmitting circuit 5, and the receiving circuit 6, as well as the overall configuration of the device. In the figure, 51 is a timing circuit, and 52 is a voltage-current conversion circuit. 61 is an amplifier, 62 is a reception timing switching circuit, and 63 is a bandpass filter (BPF).
), 64 is a detector, 65.66 is a phase detector (PSD)
, 67°, 68, and 69 are low-pass filters (L-PF), which constitute the receiving circuit 6.

The processing device 7 is composed of a well-known microprocessor, etc., and controls the timing circuit 51 and also controls the position detection section 1.
It also controls the switching of each loop coil of the
D) Convert and execute arithmetic processing to be described later to calculate the coordinate values of the position specified by the pen 4, identify the state of the switch, etc., and perform processing in accordance with this.

Next, the operation will be described. First, the manner in which radio waves are transmitted and received between the position detection section 1 and the pen 4, and the signals obtained at this time will be described with reference to FIG.

The timing circuit 51 has a predetermined frequency fO1, for example, 500.
kHz2 rectangular wave signal A1 A signal A- (not shown) obtained by delaying the phase of the rectangular wave signal A by a predetermined angle, a predetermined frequency fk,
For example, 15. A transmission/reception switching signal B and a reception timing signal C of l1i25kHz are generated.

The rectangular wave signal A is sent to the phase detector 65 and is converted into a sine wave signal by a low-pass filter (not shown) and sent to the voltage-current conversion circuit 52, and the rectangular wave signal A' is sent to the phase detector 66. Further, the transmission/reception switching signal B is sent to the transmission/reception switching circuit 3, and the reception timing signal C is sent to the reception timing switching circuit 62.

The voltage-current conversion circuit 52 converts the sine wave signal into a current signal proportional only to its voltage value and sends it to the transmission/reception switching circuit 3. Since either one of the voltage-current conversion circuit 52 and the amplifier 61 is switched and connected based on the transmission/reception switching signal B, the signal output from the transmission/reception switching circuit 3 to the selection circuit 2 has a time T (=1/2 fk), Here, the current signal is a signal of 500 kHz that is output or not output every 32 μsec.

The current signal is passed through the selection circuit 2 to the first loop coil 11-i (i=1.2°...) of the position detection section 1.
・48), but at this time, the loop coil 11
-1 generates radio waves based on the current signal.

At this time, if the pen 4 is held in a substantially upright state, that is, in a used state, near the loop coil 11-1 of the position detection unit 1, the radio wave excites the coil 412 of the pen 4, and the tuning circuit 41 of the pen 4 excites the pen 4. An induced voltage E synchronized with the current signal is generated.

Thereafter, as the current signal enters a no-signal period, that is, a reception period, either the loop coil 11-1 or the reception circuit 6
When switched to the side, the radio waves from the loop coil 11-i disappear immediately, but the induced voltage E is switched to the tuned circuit 41.
It gradually decays depending on the loss within.

On the other hand, the current flowing through the tuned circuit 41 based on the induced voltage E causes the coil 412 to emit radio waves. Since the radio waves reversely excite the loop coil 11-1 connected to the receiving circuit 6, the loop coil 11-1 includes a coil 412.
Induced voltage is generated by radio waves. The induced voltage is sent from the transmission/reception switching circuit 3 to the amplifier 61 only during the reception period, is amplified, becomes a reception signal F, and is further sent to the reception timing switching circuit 62.

A reception timing signal C, which is essentially an inverted signal of the transmission/reception switching signal B, is input to the reception timing switching circuit 62, and during a period when the signal C is at a high (H) level, the reception timing signal F is inputted to the reception timing switching circuit 62.
, and nothing is output during the low (L) level period, so the output contains signal G (substantially the same as received signal F)
is obtained, and the signal G is sent to the bandpass filter 63.

The bandpass filter 63 is a filter having a pass band centered at the frequency fO, and the frequency fO in the signal G is
A signal H having an amplitude corresponding to the energy of the component (strictly speaking, in a state in which several signals G are input to the bandpass filter 63 and converged) is passed through a detector 64 and a phase detector 65 .
66.

The signal H input to the detector 64 is detected and rectified,
After the signal is converted into a signal (■), a voltage value Vx corresponding to approximately 1/2 of the amplitude is passed through a low-pass filter 67 with a sufficiently low cutoff frequency.
The DC signal J is converted into a DC signal J having

The voltage value VX of the signal J is between the pen 4 and the loop cord 1b.
- It shows a value proportional to the distance between the loop coil 11-1 and changes when the loop coil 11-1 is switched. Therefore, the voltage value Vx obtained for each loop coil is converted into a digital value, and these values are By performing the calculation process to
The coordinate values of the position specified by the pen 4 are calculated.

On the other hand, the rectangular wave signal A is inputted to the phase detector 65 as a detected signal, and at this time, the switch 411 is off and the phase of the signal H almost matches the phase of the rectangular wave signal A. If so, a signal (substantially the same as signal I) which is exactly the positive inversion of signal H is output. This signal is passed through a low-pass filter 68 similar to the one described above.
2 (substantially the signal J
) and sent to the processing device 7.

Further, the rectangular wave signal A' is inputted to the phase detector 66 as a detection signal, but as described above, the switch 411
is off and the phase of the signal H leads the phase of the rectangular wave signal A by a predetermined angle, a signal having components on the positive side and the negative side is output. This signal is converted into a DC signal by the same low-pass filter 69 and sent to the processing device 7, or the output signal of the phase detector 66 has components on the positive and negative sides, so the low-pass filter 69 The output voltage value is considerably smaller than the output voltage value of the low-pass filter 68.

Here, when the switch 411 of the pen 4 is turned on, the phase of the current flowing through the tuning circuit 41 is delayed with respect to the induced voltage E, and the phase of the received signal F is also delayed by a predetermined angle, that is, it almost matches the phase of the rectangular wave signal A. I will do it. Therefore, the output H of the bandpass filter 63 at this time is converted into a signal having components on the positive side and the negative side by the phase detector 65, and the output of the low-pass filter 68 is converted into a signal having components on the positive side and the negative side. However, the output of the low-pass filter 69 has a predetermined voltage value corresponding to approximately 1/2 of the amplitude. It becomes a DC signal with

In this way, when the switch 411 is off, a predetermined voltage value is obtained at the output of the low-pass filter 68, and the switch 411 is turned off.
11 is on, a predetermined voltage value is obtained at the output of the low-pass filter 69. Therefore, in the processing device 7, by monitoring the output values of the low-pass filters 68 and 69, it is determined whether the switch 411 is off or not. It can be detected whether it is on or not.

Further, the information indicating the on (or off) state of the switch 411 identified here is used as information for specifying the value to be actually input among the coordinate values of the position specified by the pen 4.

Next, position detection and identification of the state of the pen 4, here the on/off state of the switch 411, in the apparatus of the present invention will be explained with reference to FIGS. 5 to 8.

First, when the entire device is powered on and enters the measurement start state, the processing device 7
~11-48, information for selecting the first loop coil 11-1 is sent to the selection circuit 2, and the loop coil 11-
1 is connected to the transmission/reception switching circuit 3. The transmission/reception switching circuit 3 switches the loop coil 11-1 based on the transmission/reception switching signal B mentioned above.
is controlled to be alternately switched to the transmitting circuit 5 and the receiving circuit 6.

At this time, the transmitting circuit 5 sends 16 sine wave current signals of 500 kHz as shown in FIG. 5(a) to the loop coil 11-1 during a 32 μsec transmission period. The switching between transmission and reception is repeated seven times for one loop coil, here 11-1, as shown in FIG. 5(b).

These seven transmission and reception repetition periods correspond to one loop coil selection period (448 μsec).

The output of the reception timing switching circuit 62 of the reception circuit 6 includes:
An induced voltage is obtained for one loop coil every seven reception periods, and as described above, this induced voltage is averaged by the bandpass filter 63, and then passed through the wave detector 64 and the phase detector 65.
．． 66 and low-pass filters 67 to 69 before being sent to the processing device 7.

At this time, the output value of the low-pass filter 67 is A/D converted,
A detected voltage proportional to the distance between the pen 4 and the loop coil 11-1 is temporarily stored as, for example, Vxl (actually, the output values of the low-pass filters 68 and 69 are also A/D converted, but at this point values are not accepted).

Next, the processing device 7 sends information for selecting the loop coil 11-2 to the selection circuit 2, connects the loop coil 11-2 to the transmission/reception switching circuit 3, and connects the loop coil 11-2 to the transmission/reception switching circuit 3 in proportion to the distance between the pen 4 and the loop coil 11-2. The detected voltage Vx2 is obtained and stored, and thereafter, the loop coils 11-3 to 11-48 are sequentially connected to the transmission/reception switching circuit 3 in the same way, and the voltage Vx2 for each loop coil as shown in FIG. 5(C) is Detection voltage Vx proportional to the distance from the pen 4
1 to Vx48 (however, only a part of it is shown in analog representation in FIG. 5(C)).

As shown in FIG. 6, the actual detected voltage is obtained only from several loop coils in front and behind the position (xp) where the pen 4 is placed as the center.

By the way, the on-resistance for each loop coil of the selection circuit 2 composed of a multiplexer varies (for example,
30±5Ω), and when each loop coil is driven with a voltage through the selection circuit 2, a difference occurs in the current value flowing through each loop coil based on the difference in resistance value. The strength of the radio waves generated by the loop coil is proportional to the value of the current flowing through the loop coil, and the strength of this radio wave is proportional to the voltage value of the induced voltage generated in the tuning circuit 41, which is ultimately generated in the loop coil during the reception period. As mentioned above, if there is a difference in the current value flowing through each loop coil, the detected induced voltage will be exactly proportional to the distance between the pen 4 and each loop coil. I won't.

In the present invention, by using the voltage-current conversion circuit 52,
The value of the current flowing through each loop coil is kept constant regardless of the variation in on-resistance in the selection circuit 2, and the detected induced voltage depends only on the distance between the pen 4 and each loop coil, and is accurately proportional to this. Fig. 7 shows that when the pen 4 is moved in a direction orthogonal to the position detection direction, the loop coil, for example 11-1.11-2.1
1-3. Induced voltages VRI and VR2 generated in 11-4
, VR3, and VR4. Figure 7(a) shows the values when the loop coil is driven by voltage, and Figure 7(b) shows the values when driven by current using a voltage-current conversion circuit. Show value.

In Figure 7(a), the deviation in the voltage direction of each induced voltage curve indicates that there is a difference in the current value flowing through each loop coil, and in Figure 7(b), each induced voltage curve shows a difference in the current value flowing through each loop coil. The fact that the voltage curves do not deviate in the voltage direction indicates that there is no difference in the current value flowing through each loop coil.

When the voltage value of the stored detection voltage is above a certain detection level, the processing device 7 calculates coordinate values representing the specified position of the ben 40 from these voltage values as described later.

Next, the loop coils 11-1 to 11-1 are placed in the processing bag.
48, the loop coil from which the maximum detected voltage was obtained is detected, information for selecting it is sent to the selection circuit 2, and the transmission and reception of the radio waves is repeated multiple times, for example, 7 times. The output values obtained from the filters 68 and 69 are A/
D conversion is performed, and as described above, it is detected which of these values is greater than or equal to a predetermined value, thereby identifying whether the switch 411 is on or off.

The result of identifying whether the switch 411 is on or off is transferred to a host device (not shown) together with the aforementioned coordinate values representing the specified position of the pen 4.

When the first position detection and state identification are completed in this way, the processing device 7 performs the second and subsequent position detection as shown in FIG.
Out of the 48 loop coils, information for selecting only a certain number of loop coils, for example 10, before and after the loop coil from which the maximum detected voltage was obtained is sent to the selection circuit 2, and the output value is determined in the same manner as described above. Then, the position of the pen 4 is detected and the on/off state of the switch 411 is identified, and the obtained coordinate values and identification results are transferred and updated, and these steps are repeated.

Therefore, when the pen 4 is operated on the position detection unit 1, all the coordinate values of the specified position by the pen 4 are transferred to the host device, and at this time, when the switch 411 is turned on,
The on-state identification information is transferred to the higher-level device, and the higher-level device can recognize the coordinate values at this point as the coordinate values to be input.

In addition, in Fig. 8, 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 it has not been reached, subsequent coordinate calculations, etc. are stopped, and the center of the loop coil to be selected in the next position detection operation and state identification 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. 5(e), the maximum detection voltage VX3
By approximating the detection voltages VX2 and Vx4 on both sides thereof by a quadratic function, it can be calculated as follows (however, the coordinate values of the center positions of each loop coil 11-1 to 11-48 are x48, and the interval is ΔX.)
. First, from each voltage and coordinate value, Vx2 = a (x2- xp) ''
・・・・・(1) Vx3= a (x3− xp)
2+ b ・・・・・・(2) Vx4=a
(x4-xp)2+b--43). Here, a and b are constants (a<0).

Also, x3 −x2 =Δx
--(4)x4 -x2 =2 ΔX
...(5). (4) , (
Substituting equations (5) into equations (2) and (3) and rearranging, we get xp-x2+Δx/2 ((3Vx2-4 VxS
+ Vx4) / (Vx2-2 Vx3+ Vx4)
1...(6)

Therefore, from each of the detection voltages Vxl to Vx48, extract the maximum detection voltage obtained during the level check and the detection voltages before and after it, and extract these and the detection voltage of the loop coil from which the maximum detection voltage was obtained. The coordinate value xp of the specified position of the pen 4 can be calculated by performing an operation corresponding to the above-mentioned equation (6) from the coordinate value (known) of the previous 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, and two sets of the position detecting sections 1 in the first embodiment are stacked so that their loop coils are orthogonal to each other. Further, 2a and 2b are selection circuits in the X direction and Y direction, 3a and 3b are transmission/reception switching circuits in the X direction and Y direction, 52a and 52b are voltage current conversion circuits in the X direction and Y direction, and 61a
and 61b are X-direction and Y-direction amplifiers, which correspond to the selection circuit 2, the transmission/reception switching circuit 3, and the transmission/reception switching circuit 3 in the first embodiment, respectively.
It has the same configuration as the voltage-current conversion circuit 52 and the amplifier 61.

53 is an XY switching circuit, which applies a sine wave signal inputted from the timing circuit 51 via a low-pass filter (not shown) to either one of the voltage-current conversion circuits 52a or 52b, and selects the direction of position detection. It is for the purpose of

Further, 62'' is a reception timing switching circuit, which selects the reception timing as well as the direction in which the reception signal from the amplifier 61a or the amplifier 61b is detected and applies it to the bandpass filter 63. 7a is a processing device. Yes, XY switching circuit 53 and reception timing switching circuit 62'
The processing device 7 is the same as the processing device 7 except that the processing device 7 controls the processing device 7 and performs position detection in the X direction and the Y direction alternately. Incidentally, the timing of the second and subsequent position detection operations and state identification operations in the processing device 7a is shown in FIG.

In this way, according to this embodiment, the position (coordinates) of the pen 4 in two directions, the X direction and the Y direction, can be easily detected.

Note that the other configurations and operations are the same as those of the first embodiment.

In addition, in the first or second embodiment, by attaching a microphone or the like to the position detection unit 1 or 1a and providing the processing device 7 or 7a with a voice recognition function, various commands can be given by voice. You can also
In the second embodiment, the processing device 7a or its host device can be provided with a character recognition function and used as a tablet for inputting handwritten characters.

Further, the number of loop coils and the arrangement thereof in the embodiments are merely examples, and it goes without saying that the present invention is not limited thereto.

(Effects of the Invention) As explained above, according to the present invention, the loop coil of the position detection section is driven with a current signal proportional only to an alternating current voltage of a predetermined frequency, and position indication is performed using the predetermined frequency as a tuning frequency. A radio wave is sent to the tuned circuit of the device, and the loop coil receives the radio wave sent in the opposite direction from the tuned circuit. At this time, the induced voltage that is generated is detected, and this is done for all of the many loop coils. As a result, an induced voltage that depends only on the distance between the position indicator and each loop coil can be obtained regardless of errors in resistance values in the selection circuit, etc., and therefore, the specified position of the position indicator can be accurately detected. In addition, it is only necessary to install a tuning circuit whose main elements are a coil and a capacitor on the position indicator side, eliminating the need for cords and heavy parts such as batteries and magnets. Improved operability. In addition, since the position detection unit does not require any special parts, it can be made larger and can be applied to electronic whiteboards, etc. In addition, by increasing the accuracy of calculation processing for the obtained induced voltage, position detection accuracy can be improved. You can also increase it further. In addition, the position detection section can be
Those provided in the X direction and the Y direction have advantages such as being able to detect positions in two directions, the X direction and the Y direction.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram showing a first embodiment of the position detection device of the present invention, Fig. 2 is a sectional view of the stylus pen, and Fig. 3 is a detailed diagram of the tuning circuit, transmitting circuit, and receiving circuit of the stylus pen, as well as the device. A diagram showing the overall configuration, FIG. 4 is a signal waveform diagram of each part in FIG. 3, and FIGS. 5 (a), (b), and (c) are timing diagrams showing the basic position detection operation in the first embodiment. , FIG. 6 is a diagram showing the detection voltage obtained from each loop coil during the first position detection operation, and FIG. 7(a)(b)
) is a diagram showing changes in the induced voltage generated in the loop coil when the pen 4 is moved in a direction perpendicular to the position detection direction,
FIG. 8 is a timing diagram showing the second and subsequent position detection operations and state identification operations, FIG. 9 is a diagram similar to FIG. 3 showing the second embodiment of the present invention, and FIG. It is a figure similar to FIG. 8 in an Example. DESCRIPTION OF SYMBOLS 1... Position detection part, 11-1 to 11-48... Loop coil, 2... Selection circuit, 3... Transmission/reception switching circuit,
4... Stylus pen, 5... Transmission circuit, 6...
Receiving circuit, 7...processing device, 41...tuning circuit.

Claims (2)

[Claims] (1) A position detection unit including a large number of loop coils arranged in parallel in the position detection direction; a selection circuit that sequentially selects one loop coil from the large number of loop coils; and a predetermined selection circuit for the selected one loop coil. a transmitting circuit driven by a current signal proportional only to an alternating current voltage having a frequency of; a position indicator including a coil and a capacitor and having the predetermined frequency as a tuning frequency; and a voltage generated in the selected one loop coil. a receiving circuit that detects an induced voltage of approximately the same frequency as the predetermined frequency; a transmission/reception switching circuit that alternately connects the selected one loop coil to the transmitting circuit and the receiving circuit; and a processing device that calculates a designated position of a position indicator from the induced voltage. (2) An X-direction and Y-direction position detection unit formed by arranging a plurality of loop coils in parallel in the X-direction and Y-direction, respectively; an X-direction and Y-direction selection circuit that sequentially selects one loop coil;
a transmitting circuit that drives a loop coil in one direction with a current signal proportional only to an alternating current voltage of a predetermined frequency; a position indicator that includes a coil and a capacitor and has the predetermined frequency as a tuning frequency; a receiving circuit for detecting an induced voltage having a frequency substantially the same as the predetermined frequency among the voltages generated in one loop coil in the X direction and the Y direction; The specified position of the position indicator in the X and Y directions is determined from the induced voltages generated in the X-direction and Y-direction transmission/reception switching circuits that are alternately connected to the transmitting circuit and the receiving circuit, and the loop coils in the X- and Y-directions. A position detection device comprising a processing device for calculating.