JP2583508B2 - Position detection device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to an improvement in a position detection device for digitizing a position on a tablet pointed by a position indicator.

(Prior Art) As a conventional position detecting device of this type, there are a tablet having a flat plate shape and generating an alternating magnetic field having different phases depending on positions, a coil and a capacitor set so as to be tuned to a fundamental frequency of the tablet. A drive circuit for generating an alternating magnetic field having a different phase on the tablet, and a reference excitation phase connected to the resonance circuit of the position indicator and supplied with a detection signal from the drive circuit. And a processing device that identifies the coordinates of the position indicated by the position indicator from the detection output of the phase detector and outputs the coordinate information (Japanese Patent Application Laid-Open No. 57-57). No. 94890).

Other conventional position detecting devices include a tablet in which conductor groups arranged at regular intervals are insulated from each other and arranged in rows and columns, a driving battery, a control circuit, a variable frequency oscillator, a frequency changeover switch, and an AC magnetic field generation. A position indicator having a frequency change switch which is turned on / off by pressing or releasing the tablet from or to the tablet to switch the frequency of the variable frequency oscillator; and an AC magnetic field generated by the position indicator. And a means for detecting the induced electromotive force and the frequency thereof, calculating the coordinate value of the position indicator on the tablet, and converting the frequency of the induced electromotive force to a predetermined value. JP-A-60-21
No. 5230).

Further, as another conventional position detecting device, a drive line is arranged in correspondence with each row of a dial (tablet) in which information such as a plurality of characters and symbols are arranged in a matrix, and each line is associated with each column. A position indicator having a resonance circuit in which a sense line is arranged and a high-frequency current is sequentially passed through each of the drive lines, and does not normally resonate with the high-frequency current, but resonates with the high-frequency current only when the tip is pressed. Then, when any information on the tablet is pressed and indicated, the position of the sense line at which an induced voltage is generated by mutual induction between the resonance circuit formed in the position indicator, the drive line and the sense line. In some cases, the row and column of information designated by the position indicator, that is, the pressed coordinates of the position indicator, are detected from the position of the drive line at that time (Japanese Patent Laid-Open No. 59-3537). Gazette).

(Problems to be Solved by the Invention) However, in the above-mentioned conventional first device, a cord for connection is required between the resonance circuit of the position indicator and the phase detector, and it becomes obstructive. In addition to troublesome handling such as disconnection due to fatigue, etc., the operation state of the position indicator, for example, the operation state of determining the position to be measured by pressing the position indicator against the tablet (pen down state) is detected. There was a problem that I could not do it at all. Further, in the second conventional device, it is possible to be cordless. However, in order to detect an operation state of the position indicator, a drive battery, a control circuit, a variable frequency oscillator, and the like are provided in the position indicator. Therefore, there is a problem that the position indicator is heavy and large in size, resulting in poor operability, and also requires replacement and charging of a driving battery, which is troublesome to handle. Furthermore, in the conventional third device, it is possible to be cordless, and a driving battery, a control circuit, a variable frequency oscillator, and the like are provided in the position indicator to detect a state in which the position indicator is pressed against the tablet. Although it is not necessary to provide the position indicator, on the other hand, if the position indicator is not pressed against the tablet, the position cannot be detected at all, and the position cannot be confirmed before the position to be measured is determined.

The present invention provides a position detecting device that can detect a position to be measured irrespective of an operation state of an operator with respect to a position indicator, and that can detect an operation state of an operator. It is intended to provide a device.

(Means for Solving the Problems) In order to achieve the above object, according to the present invention, a signal is transmitted and received between a position indicator and a tablet, and a position for detecting a coordinate value on the tablet indicated by the position indicator. A first tuning circuit which is constantly closed and instructs the tablet to indicate a position to be measured and informs a state in which an operator does not operate; and A position indicator having a second tuning circuit that has a tuning frequency different from that of the first tuning circuit and that indicates a position to be measured to the tablet and notifies the operator of the state of the operation; and a plurality of loop coils. The first and second tuning circuits are configured to generate a radio wave that can be tuned, and the radio waves caused by the tuning reflected from the first or second tuning circuit are transmitted to the first or second tuning circuit. A tablet having a radio wave detecting means for sequentially switching and detecting a plurality of loop coils, and a plurality of induced voltages induced by the reflection in a plurality of loop coils constituting the radio wave detecting means at a predetermined timing synchronized with the switching; A voltage holding means for holding, and an accuracy finer 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 and held by the voltage holding means. A coordinate calculation means for obtaining a coordinate value of a position indicated by the position indicator on the tablet regardless of whether the operation is performed, and the voltage holding induced by the reflection in a loop coil constituting the radio wave detection means. The radio wave reflected from the position indicator to the tablet from the induced voltage held by the means is 1 or to detect a radio wave reflected from any of the second tuning circuit, proposes a position detecting device that includes a tuned circuit determining means for detecting whether the operation of the operator has been made.

(Operation) According to the present invention, when a radio wave is generated from the radio wave generating means composed of a plurality of loop coils of the tablet, the radio wave is used for the first or second tuning circuit of the position indicator for specifying the position on the tablet. The first or second tuning circuit that has received the radio wave transmits or reflects the same radio wave. The radio wave caused by the tuning reflected from the first or second tuning circuit is detected by the radio wave detecting means composed of a plurality of loop coils of the tablet in accordance with the switching of the plurality of loop coils, and further the voltage is held. A plurality of induced voltages induced in the plurality of loop coils by the means are held at predetermined timings synchronized with the switching. The coordinate value of the position indicated by the position indicator on the tablet is finer than the arrangement interval of the plurality of loop coils irrespective of whether or not the operation is performed by the coordinate calculation means from the plurality of induced voltages held. While being calculated with accuracy, the tuning circuit discriminating means detects whether the radio wave reflected from the position indicator to the tablet is a radio wave reflected from the first or second tuning circuit,
It is detected whether or not an operation has been performed by the operator.

(Embodiment) FIG. 1 shows a first embodiment of a position detecting device according to the present invention. In FIG. 1, 1 is a position detecting unit, 2 is a selection circuit, 3 is a transmission / reception switching circuit, and 4 is a position indicator. Reference numeral 5 indicates a transmission circuit, reference numeral 6 indicates a reception circuit, and reference numeral 7 indicates a processing device.

In the position detecting section 1, a large number, for example, 48 loop coils 11-1, 11-2,..., 11-48 having conductors parallel to each other, are shown in the direction of arrow A in FIG. ). Further, each of 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 1, for example, a plurality of parallel conductors formed by performing etching on a known printed board or the like and connecting them with jumper wires or the like to form the plurality of loop coils is used. Can be.

The selection circuit 2 includes the plurality of loop coils 11-1 to 11-.
48 to select one loop coil sequentially,
One end of each of the loop coils 11-1 to 11-48 is connected to one terminal group 21.
, And 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 are linked 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 number of 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 And 32 respectively.
Two output terminals of the transmission circuit 5 are connected to terminals 33 and 35, and two input terminals of the reception circuit 6 are terminals 34 and 36.
It is connected to the. Selection contacts 3 corresponding to the terminals 33 and 34
1 and the selection contacts 32 corresponding to the terminals 35 and 36 are interlocked with each other,
It operates based on a transmission / reception switching signal described later, and switches between transmission and reception. The transmission / reception switching circuit 3 is also realized by a known multiplexer.

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

FIG. 2 shows a detailed structure of the pen 4. A pen 43 such as a ball-point pen and a core 43 are slid from the tip of a pen shaft 42 made of a non-metallic material such as a synthetic resin. A tuning circuit including a ferrite core 44 having a freely accommodating through hole, a coil spring 45, a switch 411, a coil 412 wound around the ferrite core 44, capacitors 413 and 414.
41 and 41 are integrally combined and built in, and a cap 46 is attached to the rear end.

The coil 412 and the capacitor 413 are connected in series with each other as shown in FIG. 3 so as to constitute a well-known resonance circuit, and the values of the coil 412 and the capacitor 413 are different from the voltage and the voltage at a predetermined frequency f0. The phase of the current is set to a value that resonates (tunes) in phase. Also the capacitor
414 is connected in parallel to both ends of the capacitor 413 via a switch 411, and when the switch 411 is turned on,
The phase of the current in the above-described resonance circuit is delayed, and the phase of the received signal described later is delayed by a predetermined angle. The switch 411 holds the pen shaft 42 by hand or the like, and pushes the tip of the core body 43 into the pen shaft 42 by pressing the tip of the core 43 against an input surface (not shown) of the position detection unit 1. It is pressed via the coil spring 45 and is turned on.

Here, a first tuning circuit is provided, in which the circuit including the coil 412 and the capacitor 413 described above is constantly closed and instructs the tablet to indicate the position to be measured and notifies the operator that the operation is not performed. And also switch 41
1. A circuit composed of a coil 412 and capacitors 413 and 414 is configured by an operator's operation (here, the switch 411 is turned on by pushing the core 43 into the pen shaft 42) and is tuned to the first tuning circuit. A second tuning circuit is provided for indicating the position to be measured to the tablet having a different frequency and for notifying the operator of the state of the operation.

FIG. 3 shows the configuration of the entire device together with details of the tuning circuit 41, the transmission circuit 5 and the reception circuit 6. In FIG. 3, reference numeral 51 denotes a timing circuit, and 53 denotes a drive circuit. 601 is an amplifier, 602 is a reception timing switching circuit, 603 is a bandpass filter (BPF), 604 is a detector, 605 and 606 are phase detectors (PSD), and 607, 608 and 609 are low-pass filters (LP
F), 610, 611, and 612 are sample and hold (SH) circuits, which constitute the receiving circuit 6. 81 is a D-flip-flop (FF), and 82 is an inverter.

The processing device 7 is composed of a well-known microprocessor or the like, controls the timing circuit 51, sends selection information for the selection circuit 2 to the D-FF 81, and outputs the information to the SH circuit 610.
Analogue digital (A / D)
D) Convert and calculate the coordinate value of the position pointed by the pen 4 by executing an arithmetic process described later on this value, and identify the tuning circuit to identify the operation state of the switch.

Here, the above-described position detection unit 1, selection circuit 2, connection switching circuit 3, and transmission circuit 5 constitute a radio wave generating unit, and the position detection unit 1, selection circuit 2, connection switching circuit 3, and reception circuit 6 include Constituting radio wave detecting means and voltage holding means,
Further, the processing device 7 constitutes coordinate calculation means and tuning circuit determination means.

Next, the operation will be described. First, a description will be given of how the radio wave is transmitted and received between the position detecting unit 1 and the pen 4 and the signals obtained at this time with reference to FIG.

The timing circuit 51 outputs a rectangular wave signal A having a predetermined frequency f0,
A signal A '(not shown) obtained by delaying the phase of the rectangular wave signal A by a predetermined angle, a transmission / reception switching signal B having a predetermined frequency f1, a reception timing signal C, and a predetermined timing signal described later are generated.

The rectangular wave signal A is transmitted to the phase detector 605, converted into a sine wave signal by a low-pass filter (not shown) and transmitted to the drive circuit 52, and the rectangular wave signal A 'is transmitted to the phase detector 606. The transmission / reception switching signal B is transmitted to the transmission / reception switching circuit 3, and the reception timing signal C is transmitted to the reception timing switching circuit 602.

The sine wave signal sent to the drive circuit 52 is converted into a balanced signal and sent to the transmission / reception switching circuit 3. The transmission / reception switching circuit 3 uses the driving circuit 52 and the amplifier 60 based on the transmission / reception switching signal B.
The transmission and reception switching circuit 3
The signal output to the selection circuit 2 is time T (= 1 / 2f1)
The signal D is a signal D for outputting or not outputting a sine wave signal of the frequency f0 every time.

The signal D is transmitted to one loop coil 11-i (i = 1, 2,..., 48) of the position detection unit 1 via the selection circuit 2, and at this time, the loop coil 11-i A radio wave based on the signal D is generated.

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

Thereafter, when the signal D enters a period in which there is no signal, that is, a reception period, and the loop coil 11-i is switched to the receiving circuit 6, the radio wave from the loop coil 11-i disappears immediately, but the induced voltage E Gradually attenuates according to the loss in the tuning circuit 41.

On the other hand, the current flowing through the tuning circuit 41 based on the conductive voltage E causes the coil 412 to emit radio waves. Since the radio wave excites the loop coil 11-i connected to the receiving circuit 6 in reverse, an induced voltage due to the radio wave from the coil 412 is generated in the loop coil 11-i. The induced voltage is sent from the transmission / reception switching circuit 3 to the amplifier 601 and amplified by the transmission / reception switching circuit 3 only during the reception period to become a reception signal F.
602.

The reception timing switching circuit 602 receives a reception timing signal C, which is substantially an inverted signal of the transmission / reception switching signal B, and outputs the reception signal F while the signal C is at a high (H) level, and outputs a low ( Since nothing is output during the L) level period, a signal G (substantially the same as the received signal F) is obtained at the output, and the signal G is sent to the bandpass filter 603.

The band-pass filter 603 is a filter having a pass band centered on the frequency f0, and has a signal H having an amplitude h corresponding to the energy of the frequency f0 component in the signal G (the amplitude of the signal H is initially Here, a predetermined number, for example, 7 to 8 signals having the same energy, that is, the signal G having the same amplitude is input, and the signal G substantially converges to show a state where the amplitude becomes a constant h.) 604 and phase detectors 605 and 606.

The signal H input to the detector 604 is detected and rectified to be a signal I, and has a voltage value Vx corresponding to almost half of the amplitude h by a low-pass filter 607 having a sufficiently low cutoff frequency. It is converted to a DC signal J, and the SH circuit 610 is used as described later.
And is sent to the processing device 7.

The voltage value Vx of the signal J is determined by the pen 4 and the loop coil 11-i.
Indicates a value proportional to the distance between the loop coil 11-i
Is switched when is switched, the voltage value Vx obtained for each loop coil is converted into a digital value, and the arithmetic processing described later is performed on the voltage value Vx to calculate the coordinate value of the position specified by the pen 4.

On the other hand, the rectangular wave signal A is input to the phase detector 605 as a detection signal. At this time, the switch 411 is off, and the phase of the signal H substantially matches the phase of the rectangular wave signal A. In this case, a signal (in substantially the same as the signal I) obtained by inverting the signal H to the positive side is output. This signal is converted into a DC signal (substantially the same as the signal J) having a voltage value corresponding to almost half of the amplitude h by the low-pass filter 608 as described above, and is temporarily stored in the SH circuit 611 for processing. It is sent to the device 7.

The rectangular wave signal A 'is input to the phase detector 606 as a detection signal.
Is off and the phase of the signal H is advanced by a predetermined angle with respect to the phase of the rectangular wave signal A ', a signal having components on the positive side and the negative side is output. This signal is converted to a DC signal by the low-pass filter 609 as described above, temporarily stored in the SH circuit 612, and sent to the processing device 7, but the phase detector 60
Since the output signal of FIG. 6 has components on the positive side and the negative side, the voltage value of the output of the low-pass filter 609, that is, the output of the SH circuit 612 is considerably smaller than the voltage value of the output of the low-pass filter 608, that is, the output of the SH circuit 611. Value.

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,
The phase of the received signal F is also delayed by a predetermined angle, that is, almost coincides with the phase of the rectangular wave signal A '. Accordingly, the output H of the bandpass filter 603 at this time is converted into a signal having components on the positive side and the negative side by the phase detector 605, and the lowpass filter 60
8, that is, the output of the SH circuit 611 has substantially the same voltage value as the output of the low-pass filter 609 when the switch 411 is turned off, that is, the output of the SH circuit 612, but the signal inverted to the positive side by the phase detector 606. As a result, the output of the low-pass filter 609, that is, the output of the SH circuit 612 becomes a DC signal having a predetermined voltage value corresponding to almost half of the amplitude h, as described above.

As described above, when the switch 411 is off, a predetermined voltage value is obtained at the output of the SH circuit 611, and when the switch 411 is on, a predetermined voltage value is obtained at the output of the SH circuit 612. At 7, the output value of the SH circuits 611 and 612 can be monitored to detect whether the switch 411 is off or on.

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

Next, referring to FIGS. 5 to 7, the position detection and the state of the pen 4 in the apparatus of the present invention, that is, the identification of the ON / OFF state of the switch 411, will be described below.
This will be described together with the operation of the FF81 and the inverter 82.

When the power of the entire device is turned on and the measurement starts,
The processing device 7 includes the loop coil selection information 10 of the position detection unit 1.
0 is sent to D-FF81. D-FF81 has a timing circuit 5
Timing signal 1 of frequency f2 (= f1 / 4) output from 1
01 Timing signal 102 inverted by inverter 82
Is input as a strobe signal, and the information 100 is latched at the rising edge of the signal and sent to the selection circuit 2 as information 103. The selection circuit 2 receives the information 103 and connects one of the loop coils 11-1 to 11-48, here the loop coil 11-1, to the transmission / reception switching circuit 3. The transmission / reception switching circuit 3 alternately controls the switching of the loop coil 11-1 to the transmission circuit 5 and the reception circuit 6 based on the transmission / reception switching signal B described above.

At this time, during the transmission period of time T, the transmission circuit 5 transmits the sine wave signal of the frequency f0 as described above to the loop coil 11.
Send to -1. The switching between transmission and reception is repeated four times for one loop coil, here 11-1. The repetition period of the four times of transmission and reception corresponds to a selection period of one loop coil, that is, one cycle of the timing signal 100 or 101.

In the output of the reception timing switching circuit 602 of the reception circuit 6, an induced voltage 104 having the same amplitude is obtained for each loop coil every four reception periods. The induced voltage 104 is sent out to the bandpass filter 603, is converted into an output voltage 105 corresponding to the energy of the frequency f0 component, is detected and rectified by the detector 604, and is further composed of the envelope component by the low-pass filter 607. The signal 106 is used.

Incidentally, the signal 106, in other words, the output voltage 105 initially gradually increases each time the induced voltage 104 having the same amplitude is applied, and then the induced voltage 104 having the same amplitude becomes 7 according to the transient response characteristic of the bandpass filter 603. When about 8 pieces are input, they almost converge and become a constant voltage value. Here, the induced voltage 104 with the same amplitude, that is, the same loop coil is 4
Since the number is limited to individual pieces, it does not sufficiently converge.

On the other hand, the timing at which the processing device 7 reads the induced voltage for one loop coil from the receiving circuit 6 and performs A / D conversion differs depending on internal processing conditions, and is not always constant for each loop coil. Therefore, the low-pass filter 607
Is output to the treatment device 7 as it is, and the processing device 7 reads the output at a timing corresponding to the internal processing state.
When D conversion is performed, a voltage that is not proportional to the distance between the pen 4 and each loop coil may be obtained.

Therefore, in this embodiment, one loop coil is selected, and the output 106 of the low-pass filter 607 at the time when a certain time has elapsed since the start of transmission / reception of radio waves is held in the SH circuit 610. To obtain a voltage proportional to the distance between the pen 4 and each loop coil (note that the number of times of transmission / reception of radio waves is increased, and after the induced voltage has sufficiently converged, the processing device 7, the voltage proportional to the distance between the pen 4 and each loop coil can be obtained. In this case, however, the time during which one loop coil is selected becomes longer, and accordingly, ,
The position detection speed will be reduced. ).

The timing signal 101 is input to the SH circuit 610 as a sample and hold signal. When the timing signal 101 falls, that is, immediately before the loop coil is switched, the voltage value of the signal 106 is changed to a low level period t (= 1
/ 2f2).

The timing signal 101 is also input as an interrupt signal to the processing device 7, and the processing device 7 outputs a signal during the period when the timing signal 101 is at a low level, that is, when the SH circuit 610
While holding the voltage value of 106, read its output 107,
A / D converted and the loop coil of pen 4 and one, here 11-
It is temporarily stored as a detection voltage proportional to the distance from the control signal 1, for example, Vx1.

Further, the processing device 7 sends the information 100 for selecting the loop coil 11-2 before the next rise of the timing signal 102 to the D / FF8.
1, the loop coil 11-2 is connected to the transmission / reception switching circuit 3, and the pen 4 and the loop coil 11-2 are transmitted.
, A detection voltage Vx2 proportional to the distance between the loop coils 11-3 to 11-
48 are sequentially connected to the transmission / reception switching circuit 3, and the detection voltages Vx1 to Vx48 are proportional to the distance between each loop coil and the pen 4 (however, only a part thereof is shown in an analog-like expression in FIG. 5). Is stored.

The actual detected voltage is obtained only in the several loop coils before and after the position (xp) where the pen 4 is placed as a center, as shown in FIG.

When the voltage value of the stored detection voltage is equal to or higher than a predetermined detection level, the processing device 7 calculates a coordinate value indicating the designated position of the pen 4 from these voltage values as described later.

Next, the processing device 7 controls the loop coils 11-1 to 11-48.
Among them, the information 100 for selecting the loop coil for which the maximum detection voltage is obtained is transmitted to the D-FF 81, and the transmission and reception of the radio wave is repeated a plurality of times, for example, four times.
A / D conversion of the output values output from 8 and 609, and held in the same manner as in the SH circuits 611 and 612, to detect which of these values is greater than or equal to a predetermined value as described above, On / off of the switch 411 is identified.

The on / off identification result of the switch 411 is transferred to a host device (not shown) together with the coordinate value indicating the designated position of the pen 4 described above.

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.
Among them, the constant value before and after the loop coil at which the maximum detection voltage was obtained, for example, information 100 for selecting only 10 loop coils is sent to the D-FF81, and the output value is set 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 the identification result are transferred and updated.

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

Also, in FIG. 7, the level check is to check whether the maximum value of the detection voltage has reached the detection level and to determine which loop coil has the maximum value of the detection voltage, and determine the detection level. If it has not reached, the subsequent coordinate calculation and the like are stopped, and the center of the loop coil to be selected in the next position detection operation and state identification 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 Vx1 to Vx48 by an appropriate function, and obtaining the coordinates of the maximum value of the function.

For example, in the signal 107 in FIG. 5, when the detection voltage Vx2 of the maximum value and the detection voltages Vx1 and Vx3 on both sides thereof are approximated by a quadratic function, it can be calculated as follows (however, each loop coil The coordinate values of the center positions of 11-1 to 11-48 are x1 to x48, and the interval is Δx.) First, from the respective voltages and coordinate values, Vx1 = a (x1-xp) ² + b (1) Vx2 = a (x2-xp) ² + b (2) Vx3 = a (x3-xp) ² + b ... ... (3) Here, a and b are constants (a <0). X2−x1 = Δx (4) x3−x1 = 2Δx (5) Substituting the equations (4) and (5) into the equations (2) and (3) and rearranging it, xp = x1 + Δx / 2 ｛(3Vx1-4Vx2 + Vx3) / (Vx1-2Vx2 + Vx3)｝ (6) .

Therefore, the maximum value of the detection voltage obtained at the time of the level check and the detection voltages before and after that are extracted from each of the detection voltages Vx1 to Vx48, and these and the one of the loop coil from which the maximum value of the detection voltage is obtained are extracted. The coordinate value xp of the designated position of the pen 4 can be calculated by performing an operation corresponding to the above-described equation (6) from the coordinate value (known) of the previous loop coil.

FIG. 8 shows a second embodiment of the present invention. Here, an example in which position detection in the X direction and the Y direction is performed is shown. That is, in the figure, reference numeral 1a denotes a position detection unit in the X direction and the Y direction.
In this embodiment, two sets of position detectors 1 are superposed such that their loop coils are orthogonal to each other. 2a and 2b are selection circuits in the X and Y directions, 3a and 3b
Is a transmission / reception switching circuit in the X and Y directions, 52a and 52b are drive circuits in the X and Y directions, 601a and 601b are X and Y
Directional amplifiers, each having the same configuration as the selection circuit 2, transmission / reception switching circuit 3, drive circuit 52, and amplifier 601 in the first embodiment.

Reference numeral 53 denotes an XY switching circuit which applies a sine wave signal input from the timing circuit 51 via a low-pass filter (not shown) to one of the driving circuits 52a and 52b and selects a direction for position detection. belongs to. Reference numeral 613 denotes a reception timing switching circuit for selecting a reception timing together with a direction in which a reception signal from the amplifier 601a or 601b is detected and adding the reception timing to the bandpass filter 603. Also, 7
a is a processing device, which is the same as the processing device 7 except that the XY switching circuit 53 and the reception timing switching circuit 613 are controlled so that position detection in the X direction and the Y direction is performed alternately. . Note that the timing of the second and subsequent position detection operations and state identification operations in the
Shown in the figure.

As described above, according to the present embodiment, it is possible to easily detect the positions (coordinates) of the pen 4 in the two directions of the X direction and the Y direction. Other configurations and operations are the same as those of the first embodiment.

In the first or second embodiment, the position detector 1
Alternatively, by attaching a microphone or the like to 1a and providing the processing device 7 or 7a with a voice recognition function, various instructions can be performed by voice. In the second embodiment, the processing device 7a Alternatively, a higher-level device having a character recognition function can be used as a tablet for inputting handwritten characters.

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

(Effects of the Invention) As described above, according to the present invention, the first and second tunings are performed on the position indicator having the first and second tuning circuits having different tuning frequencies from the radio wave generating means of the tablet. The circuit generates a radio wave that can be tuned, and is reflected from a first tuning circuit that is normally closed among the first or second tuning circuits or a second tuning circuit that is configured by an operation of an operator. Radio waves resulting from the tuning are detected by the radio wave detection means of the tablet, and a plurality of induced voltages induced by the voltage holding means to the plurality of loop coils constituting the radio wave detection means are synchronized with the switching of the plurality of loop coils. And the coordinate value of the position indicated by the position indicator on the tablet regardless of whether the operation is performed by the coordinate calculation means. It is calculated with finer accuracy, and the tuning circuit discriminating means detects whether the radio wave reflected from the position indicator to the tablet is the radio wave reflected from the first or second tuning circuit. Since it detects whether or not the operator's operation has been performed, even if each loop coil is switched at a short interval such that the induced voltage does not sufficiently converge, a radio wave is detected for each loop coil for a certain period of time. A voltage value at that time, that is, an induced voltage value depending only on the distance between the position indicator and each loop coil can be obtained, and therefore, the position detection speed can be increased without deteriorating the position detection accuracy. Also, the position indicator only needs to be provided with a passive element such as a coil or a capacitor for forming a tuning circuit, and the cord is not required. In addition, heavy parts such as batteries and magnets are not required, so that the weight and cost are reduced, the burden of replacing batteries is eliminated, the operability is extremely improved, and the coordinate values on the tablet are reduced. It is possible to detect whether or not the operation has been performed, and to detect whether or not the operator has operated the position indicator together with the detection of the coordinate value based on which tuning circuit has reflected the radio wave. There are advantages.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of a position detecting device of the present invention, FIG. 2 is a cross-sectional view of a stylus pen, and FIG. 3 is a device together with details of a tuning circuit, a transmitting circuit and a receiving circuit of the stylus pen. FIG. 4 is a signal waveform diagram of each part in FIG. 3, FIG. 5 is a timing chart showing a basic position detecting operation in the first embodiment, and FIG. FIG. 7 is a diagram showing a detection voltage obtained from each loop coil at the time of the position detection operation, FIG. 7 is a timing chart showing the second and subsequent position detection operations and state identification operations, and FIG. 8 is a second embodiment of the present invention. FIG. 9 is a view similar to FIG. 3 showing an example, and FIG. 9 is a view similar to FIG. 7 in the second embodiment. 1. Position detecting unit, 11-1 to 11-48 Loop coil,
2 selection circuit, 3 transmission / reception switching circuit, 4 stylus pen, 5 transmission circuit, 6 reception circuit, 7 processing unit, 41 tuning circuit.

Continued on the front page (72) Inventor Toshihide Senzu 5-23-4 Sakurada, Washinomiya-cho, Kita-Katsushika-gun, Saitama

Claims (3)

(57) [Claims] 1. A position detecting device for transmitting and receiving signals between a position indicator and a tablet, and detecting a coordinate value on the tablet indicated by the position indicator, wherein the position detecting device is constantly closed and connected to the tablet. On the other hand, a first tuning circuit for designating the position to be measured and notifying that the operator does not operate, and a tuning frequency different from the first tuning circuit which is constituted by the operation of the operator and which is different from that of the first tuning circuit. A position indicator having a second tuning circuit for designating a position to be performed and notifying the operator of the operation, and a plurality of loop coils, wherein the first and second tuning circuits are tuned. Radio wave generating means for generating a radio wave which can be generated, and radio wave detection for detecting a radio wave caused by the tuning reflected from the first or second tuning circuit by sequentially switching the plurality of loop coils A tablet having a step, voltage holding means for holding a plurality of induced voltages induced by the reflection in a plurality of loop coils constituting the radio wave detection means at a predetermined timing synchronized with the switching, and the radio wave detection means Regardless of whether or not the operation is performed with a finer accuracy than the arrangement interval of the plurality of loop coils, the plurality of induced voltages induced by the reflection in the plurality of loop coils to be configured and held by the voltage holding unit, A coordinate calculating means for obtaining a coordinate value of a pointing position of the position indicator on the tablet; and a position indication based on an induced voltage induced by the reflection in a loop coil constituting the radio wave detecting means and held by the voltage holding means. The radio wave reflected from the device to the tablet is the radio wave reflected from either the first or second tuning circuit. And a tuning circuit discriminating means for detecting whether or not the operator has performed the operation. 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.