JP2608895B2 - Coordinate input method and device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a coordinate input method for digitizing and inputting a position on a tablet designated by a position indicator and an apparatus therefor.

(Prior Art) As a conventional coordinate input 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 coordinate input 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 coordinate input 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. In pressing and instructing any information on the tablet, the position of the sense line where an induced voltage is generated by mutual induction between the resonance circuit formed by the position indicator, the drive line and the sense line, and 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). reference).

(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.

Conventionally, an operation of an operator on a position indicator, particularly an operation of an operator capable of continuously changing parameters other than coordinate values, for example, in a case where pen pressure is detected, a configuration for detecting an indicated position is provided. Detecting pen pressure applied to a position indicator by providing a pressure sensor on the position indicator provided or by providing a pressure sensor on the entire coordinate input range of a tablet also provided with a configuration for detecting the indicated position However, this is output together with the coordinate value of the designated position.However, in the case where the pressure sensor is provided in the position indicator, a cable or the like for extracting the pressure-sensitive information from the position indicator becomes indispensable. Therefore, the operability at the time of the input operation is deteriorated, and when the pressure-sensitive sensor is provided over the entire coordinate input range of the tablet, the characteristics of the pressure-sensitive sensor over the entire range are made uniform. The is difficult, therefore, there is a problem that it is difficult to detect accurately in the entire range of the writing pressure applied to the position indicator.

Advantageous Effects of Invention According to the present invention, a position indicator is not connected anywhere, and operability is good, a position to be measured can be detected regardless of an operator's operation on the position indicator, and parameters other than coordinate values can be continuously changed. An object of the present invention is to provide a coordinate input method and a coordinate input method capable of accurately detecting an operation of an operator over the entire coordinate input range of a tablet.

(Means for Solving the Problems) In order to achieve the above object, according to the present invention, signals are transmitted and received between a position indicator and a tablet, and coordinates for detecting a coordinate value on the tablet pointed by the position indicator. An input method, wherein a radio wave is generated from radio wave generating means composed of a plurality of loop coils of a tablet, a frequency that can be tuned to the radio wave is indicated to a tuning frequency and a position to be measured for the tablet, and an operator is provided. The radio wave is reflected by a position indicator whose tuning frequency changes continuously according to the operation of the tablet, and the reflected radio wave is detected by radio wave detecting means composed of a plurality of loop coils of the tablet. From the plurality of induced voltages thus obtained, the coordinate value of the position indicated by the position indicator on the tablet is narrower than the interval between the plurality of loop coils by predetermined interpolation calculation processing. Calculated regardless of the operation with padding accuracy, detects the phase difference between the detected induced voltage and the radio wave generated by the radio wave generating means, detects the continuous change of the tuning frequency in the tuning circuit, and detects the position. A coordinate input method for detecting an operator's operation on the indicator is proposed.

A coordinate input device for transmitting and receiving signals between the position indicator and the tablet and detecting coordinate values on the tablet pointed by the position indicator, and instructing the tablet on the position to be measured; A position indicator having a tuning circuit for continuously changing the tuning frequency in accordance with the operation of the operator and notifying the operation of the operator, and a radio wave which is constituted by a plurality of loop coils and which can be tuned by the tuning circuit. And a tablet having a radio wave detecting means for detecting a radio wave caused by the tuning reflected from the tuning circuit, and a plurality of loop coils formed by the reflection on a plurality of loop coils constituting the radio wave detecting means. Irrespective of the operation from the induced voltage of the position indicator by a predetermined interpolation calculation process with a finer accuracy than the arrangement interval of the plurality of loop coils. A coordinate calculating means for obtaining a coordinate value of the designated position on the tablet; a position of a radio wave generated by a loop coil constituting the radio wave generating means and a position of an induced voltage induced by the reflection in the loop coil constituting the radio wave detecting means. A coordinate input device comprising: a phase difference detecting unit that detects a phase difference, detects a continuous change in a tuning frequency in the tuning circuit, and detects an operation of an operator on the position indicator.

(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 tuned to the tuning circuit of the position indicator for designating the position on the tablet, that is, received. However, the tuning circuit that has received the radio wave generates a similar radio wave, that is, reflects it. The reflected radio waves are detected by radio wave detecting means composed of a plurality of loop coils of the tablet, and the coordinate value of the position indicated on the tablet is changed by the plurality of loop coils regardless of the operation of the operator on the position indicator. Is calculated with a finer accuracy than the disposition interval. Sometimes, the induced voltage at this time is accompanied by a phase shift corresponding to a continuous change of the tuning frequency in the tuning circuit of the position indicator. From this, the operation of the operator on the position indicator is detected. .

(Embodiment) FIG. 1 shows an embodiment of a coordinate input method and an apparatus of the present invention, in which 10 is a tablet, 20 is a position indicator (input pen), 30 is a control circuit, and 31 is a control circuit. Signal generation circuit, 32
And 33 are selection circuits in the X and Y directions, 34 and 35 are transmission / reception switching circuits, 36 is an XY switching circuit, 37 is a reception timing switching circuit, 38 is a bandpass filter (BPF), 39 is a detector, and 40 is a low band. Filters (LPF), 41 and 42 are phase detectors (PSD), 43 and 44 are low-pass filters (LPF), 45 and 46 are driving circuits, 47 and 48 are amplifiers, 49 is a host computer, 50 is a display device, 51 is an output device.

Here, the tablet 10, the signal generation circuit 31, the selection circuits 32 and 33, the transmission / reception switching circuits 34 and 35, the XY switching circuit 36, and the driving circuits 45 and 46 constitute a radio wave generation unit. The circuits 32, 33, the transmission / reception switching circuits 34, 35, the reception timing switching circuit 37, the bandpass filter 38, and the amplifiers 47, 48 constitute a radio wave detection unit, and further include a detector 39, a low-pass filter 40.
And the processing in the control circuit 30 constitutes a coordinate calculation means,
The processing in the phase detectors 41 and 42, the low-pass filters 43 and 44, and the control circuit 30 constitutes a phase difference detecting means.

FIG. 2 shows details of the loop coil group 11 in the X direction and the loop coil group 12 in the Y direction that constitute the tablet 10. A large number of X-direction loop coil groups 11 are arranged in parallel with each other along the X-direction, for example,
It consists of 48 loop coils 11-1, 11-2, ... 11-48,
A large number of loop coils 12 arranged in the Y direction are arranged in parallel with each other and overlap with each other along the Y direction.
, 12-48, the X-direction loop coil group 11 and the Y-direction loop coil group 12
Are closely overlapped with each other (however, they are illustrated separately for easy understanding in the drawings), and further housed in a case (not shown) made of a nonmetallic material. Here, each loop coil is configured by one turn,
Multiple turns may be provided as needed.

FIG. 3 shows a specific structure of the input pen 20, in which a pen shaft 21 made of a non-metallic material such as a synthetic resin, a core 23 having a ferrite chip 22, and the core 23 are slid. It comprises a coil 24 that can be movably accommodated, a core holder 25 that holds the rear end of the core body 23, a spring 26 that supports the core holder 25 so that it can be slightly displaced with respect to the pen shaft 21, and a capacitor 27. ing.

As shown in FIG. 1, the coil 24 and the capacitor 27 are connected in series with each other to constitute a well-known tuning circuit 28. The inductance of the coil 24 and the capacitance value of the capacitor 27 are adjusted by the tuning ( (Resonance) frequency is set to a value that is substantially equal to a predetermined frequency f0. Here, the core 23
In the state where is held by the core holder 25, the ferrite chip 22 is located at the end of the coil 24, and when the input pen 20 is operated on the tablet 10, the core body 23, That is, the ferrite chip 22 moves, thereby changing the inductance of the coil 24, and slightly changing the tuning frequency in the above-described tuning circuit 28, thereby notifying the tablet 10 of the operation of the operator, here, the pen pressure. It looks like this.

Next, the operation of the apparatus will be described together with its configuration. First, how radio waves are transmitted and received between the tablet 10 and the input pen 20 and the signals obtained at this time will be described with reference to FIG.

The control circuit 30 includes a well-known microprocessor or the like, controls the signal generation circuit 31, and controls switching of each loop coil of the tablet 10 via the selection circuits 32 and 33 according to the flowchart shown in FIG. Also,
The switching of the coordinate detection direction is controlled for the XY switching circuit 36 and the reception timing switching circuit 37, and a low-pass filter is further provided.
Analog / digital (A / D) output values from 40, 43, 44
After the conversion, an interpolation calculation process described later is executed to obtain the coordinate value of the position indicated by the input pen 20, the phase of the received signal is detected, and these are sent to the host computer 49.

The selection circuit 32 sequentially selects one loop coil from the X-direction loop coil group 11, and the selection circuit 33 sequentially selects one loop coil from the Y-direction loop coil group 12. And operate according to the information from the control circuit 30.

The transmission / reception switching circuit 34 alternately connects the selected one loop coil in the X direction to the drive circuit 45 and the amplifier 47, and the transmission / reception switching circuit 35 connects the one loop coil in the selected Y direction. Are alternately connected to the drive circuit 46 and the amplifier 48, which operate according to a transmission / reception switching signal described later.

The signal generating circuit 31 has a predetermined frequency f0, for example, a rectangular wave signal A having a frequency of 500 kHz, a signal B obtained by delaying the phase of the rectangular wave signal A by 90 °, a transmission / reception switching signal C having a predetermined frequency fk, for example, 15.625 kHz, and a reception timing signal. D is generated. The rectangular wave signal A is sent to the phase detector 41 as it is, and is converted into a sine wave signal E by a low-pass filter (not shown).
Further, the rectangular wave signal B is transmitted to one of the driving circuits 45 and 46 via the XY switching circuit 36, and the rectangular wave signal B is transmitted to the phase detector 42.
The transmission / reception switching signal C is transmitted to transmission / reception switching circuits 34 and 35, and the reception timing signal D is transmitted to the reception timing switching circuit 37.

Now, assuming that information for selecting the X direction is input from the control circuit 30 to the XY switching circuit 36 and the reception timing switching circuit 37, the sine wave signal E is sent to the driving circuit 45 and converted into a balanced signal. The signal is transmitted to the transmission / reception switching circuit 34.The transmission / reception switching circuit 34 outputs the signal to the selection circuit 32 from the transmission / reception switching circuit 34 in order to switch and connect one of the driving circuit 45 and the amplifier 47 based on the transmission / reception switching signal C. The signal F is a signal F that outputs or does not output a 500 kHz signal every time T (= 1 / 2fk), in this case, every 32 μsec.

The signal F is transmitted to one of the loop coils 11-i (i = 1, 2,..., 48) in the X direction of the tablet 10 via the selection circuit 32. Generates radio waves based on

At this time, if the input pen 20 is held substantially upright, that is, in use, on the tablet 10, the radio wave excites the coil 24 of the input pen 20, and the tuning signal 28 is sent to the tuning circuit 28.
To generate an induced voltage G synchronized with the above.

Thereafter, when the signal F enters a period in which there is no signal, that is, a reception period, and the loop coil 11-i is switched to the amplifier 47 side, the radio wave from the loop coil 11-i immediately disappears, but the induced voltage G is reduced. It gradually attenuates according to the loss in the tuning circuit 28.

On the other hand, the current flowing through the tuning circuit 28 based on the induction voltage G causes the coil 24 to emit radio waves. The radio wave is an amplifier
In order to excite the loop coil 11-i connected to 47 in reverse, an induced voltage is generated in the loop coil 11-i by radio waves from the coil 24. The induced voltage is sent from the transmission / reception switching circuit 34 to the amplifier 47 and amplified to the reception signal H only during the reception period, and is further transmitted to the reception timing switching circuit 37.

In the reception timing switching circuit 37, either one of the selection information in the X direction or the Y direction, here, the selection information in the X direction,
A reception timing signal D, which is substantially an inverted signal of the transmission / reception switching signal C, is input. The reception signal H is output when the signal D is at a high (H) level, and the reception signal H is output during a low (L) level. Since nothing is output, a signal I (substantially the same as the reception signal H) is obtained at the output.

The signal I is transmitted to a band filter 38. The band filter 38 is a ceramic filter having a frequency f0 as a unique frequency, and a signal J having an amplitude corresponding to the energy of the frequency f0 component in the signal I. (Strictly, in a state where several signals I are input to the bandpass filter 38 and converged) are transmitted to the detector 39 and the phase detectors 41 and 42.

The signal J input to the detector 39 is detected and rectified,
Low-pass filter with sufficiently low cutoff frequency after signal K
At 40, a voltage value corresponding to almost half of the amplitude, for example, Vx
And transmitted to the control circuit 30.

The voltage value Vx of the signal L depends on the input pen 20 and the loop coil 11.
-A value dependent on the distance to i, here approximately 4 of the distance
Since the value indicates a value inversely proportional to the power and changes when the loop coil 11-i is switched, the control circuit 30 converts a voltage value Vx obtained for each loop coil into a digital value,
By performing the interpolation calculation processing described later on these,
The coordinate value of the position indicated by the input pen 20 in the X direction is obtained. The coordinate value of the position indicated by the input pen 20 in the Y direction is obtained in the same manner.

On the other hand, the rectangular wave signals A and B are input to the phase detectors 41 and 42 as detection signals. At this time, if the phase of the signal J substantially matches the phase of the rectangular wave signal A, the phase The detector 41 outputs a signal M1 (substantially the same as the signal K) obtained by inverting the signal J to the positive side, and the phase detector 42 outputs a signal M2 having a symmetrical waveform on the positive side and the negative side. I do.

The signal M1 is converted to a DC signal N1 (substantially the same as the signal L) having a voltage value corresponding to almost half the amplitude of the signal J, that is, Vx by the low-pass filter 43 similar to the above, and the control circuit 30
The signal M2 is sent to the control circuit 30 converted into the DC signal N2 by the same low-pass filter 44.Here, the positive and negative components of the signal M2 of the phase detector 42 are sent here. Are the same, the voltage value of the output of the low-pass filter 44 is 0 [V].

The control circuit 30 converts the output values of the low-pass filters 43 and 44, here the signals N1 and N2, into digital values, and further uses the digital values to perform the arithmetic processing of the following equation (1). The phase difference θ between the signal added to the signal 42, here, J and the rectangular wave signal A is obtained.

θ = −tan ⁻¹ (VQ / VP) (1) where VP indicates a digital value corresponding to the output of the low-pass filter 43 and VQ indicates a digital value corresponding to the output of the low-pass filter 44 . For example, in the case of the signal J described above, the signal
The voltage value of N1 is Vx, while the voltage value of signal N2 is 0 [V],
That is, since VQ = 0, the phase difference θ = 0 °.

By the way, the phase of the signal J is determined by the tuning circuit of the input pen 20.
It changes corresponding to the tuning frequency at 28. That is, when the tuning frequency in the tuning circuit 28 matches the predetermined frequency f0, an induced voltage having the frequency f0 is generated in the tuning circuit 28 during both the signal transmission period and the signal reception period, and the induced current is synchronized with this. Flows, the frequency and phase of the reception signal H (or I) match the rectangular wave signal A,
The phase of the signal J also matches the rectangular wave signal A.

On the other hand, the tuning frequency in the tuning circuit 28 is a predetermined frequency.
In the case where the frequency does not coincide with f0, for example, a frequency slightly lower than the frequency f0, for example, f1, an induced voltage having a frequency f0 is generated in the tuning circuit 28 during a signal transmission period. Induction current with phase lag flows,
In addition, during the signal receiving period, an induced voltage having a frequency f1 and an induced current synchronized therewith flow, so that the frequency of the received signal H (or I) is slightly lower than the frequency of the rectangular wave signal A. The phase is also slightly delayed. As described above, since the bandpass filter 38 uses only the frequency f0 as the frequency, the frequency shift of the input signal to the lower side is output as a phase delay,
Therefore, the phase of the signal J is further delayed than the received signal H (or I).

Conversely, when the tuning frequency in the tuning circuit 28 is a frequency slightly higher than the predetermined frequency f0, for example, f2, an induced voltage having a frequency f0 is generated in the tuning circuit 28 during a signal transmission period. An induced current with a phase advance flows through the tuning circuit 28, and an induced voltage having substantially the frequency f2 and an induced current tuned to the induced voltage flow during the signal receiving period. Therefore, the frequency of the received signal H (or I) is The frequency is slightly higher than the frequency of the rectangular wave signal A, and its phase is slightly advanced. In the band-pass filter 38, the shift of the frequency of the input signal to the higher side will be output as the phase advance contrary to the case described above.
The phase of the signal J is further advanced than the reception signal H (or I).

As described above, the tuning frequency of the tuning circuit 28 is
, The phase difference θ determined by the above equation (1) also changes in accordance with the pen pressure. In the present embodiment, the phase difference θ is preset to be about −60 ° when no writing pressure is applied to the input pen 20, and to be about 60 ° when the writing pressure is applied most.

The obtained phase difference θ is added by 40 °, −20 ° to 10
After being converted into phase information of a value in the range of 0 °, it is sent to the host computer 49 together with the coordinate values of the designated position in the X and Y directions (addition of 40 ° described above is performed by the host computer 49 side). You may do it.)

Next, according to FIGS. 5 to 9, the coordinate detection operation and the phase detection operation and the phase information representing the pen pressure are input to the input pen.
The method of converting into the spread information of the figure indicating the designated position by 20 will be described in detail.

First, when the power of the entire apparatus is turned on and the measurement is started, the control circuit 30 transmits information for selecting the X direction to the XY switching circuit.
36 and the reception timing switching circuit 37,
Among the loop coils 11-1 to 11-48 in the X direction of the tablet 1, information for selecting the first loop coil 11-1 is sent to the selection circuit 32, and the transmission / reception switching circuit 34 transmits the loop coil 11-1.
Connect to

The transmission / reception switching circuit 34 alternately connects the loop coil 11-1 to the driving circuit 45 and the amplifier 47 based on the transmission / reception switching signal C described above. At this time, the driving circuit 45 operates during the transmission period of 32 μsec in FIG. 500kHz 16 as shown in (a)
Are sent to the loop coil 11-1 (note that
FIG. 4 shows only five of them for convenience of the drawing. ).

The switching between transmission and reception is repeated seven times for one loop coil, here 11-1, as shown in FIG. 6 (b). The seven transmission and reception repetition periods correspond to one loop coil selection period (448 μsec).

At this time, an induced voltage is obtained from the output of the amplifier 47 every seven reception periods for one loop coil, and this induced voltage is applied to the bandpass filter 38 via the reception timing switching circuit 37 as described above. The signal is transmitted, averaged, and transmitted to the control circuit 30 via the detector 39, the phase detectors 41 and 42, and the low-pass filters 40, 43 and 44.

The control circuit 30 A / D converts and outputs the output value of the low-pass filter 40 and temporarily stores it as a detection voltage depending on the distance between the input pen 20 and the loop coil 11-1, for example, Vx1.

Next, the control circuit 30 sends information for selecting the loop coil 11-2 to the selection circuit 32, connects the loop coil 11-2 to the transmission / reception switching circuit 34, and sets the distance between the input pen 20 and the loop coil 11-2. A detection voltage Vx2 proportional to is obtained and stored. Thereafter, similarly, the loop coils 11-3 to 11-48 are sequentially connected to the transmission / reception switching circuit 34, and the respective loops as shown in FIG. Detected voltages Vx1 to Vx48 (although only a part thereof is shown in an analog expression in FIG. 6 (c)) are stored in proportion to the distance in the X direction between each coil and the input pen 20.

The actual detection voltage is obtained only in the several loop coils before and after the position (xp) where the input pen 20 is placed as a center as shown in FIG.

The control circuit 30 checks whether or not the maximum value of the plurality of stored detection voltages is equal to or higher than a predetermined fixed detection level, for example, the detection level shown in FIG. 7. The selection and voltage detection of each loop coil in the X direction are repeated again, and if it is equal to or higher than a certain detection level, the process proceeds to the next process.

Next, the control circuit 30 sends selection information in the Y direction to the XY switching circuit 36 and the reception timing switching circuit 37, switches the selection circuit 33 and the transmission / reception switching circuit 35 in the same manner as described above, The input pen 20 obtained by A / D converting the output value of the filter 40 and each of the Y-direction loop coils 12-1 to 12-
The detection voltage depending on the distance to 48 is temporarily stored. Thereafter, a level check is performed in the same manner as described above, and if the maximum value of the detected voltage is equal to or lower than a certain detection level, the process returns to the selection of each loop coil in the X direction and voltage detection again. If so, the coordinate values in the X and Y directions of the position pointed to by the pen 20 are calculated as described later than the stored voltage values.

Next, the control circuit 30 controls the loop coil 11-1 in the X direction.
~ 11-48 (or Y-direction loop coils 12-1 to 12-48)
The information for selecting the loop coil (peak coil) for which the maximum detection voltage is obtained is transmitted to the selection circuit 32 (or 33), and the transmission and reception of the radio wave is repeated a plurality of times, for example, seven times. The output values obtained from the bandpass filters 43 and 44 are A / D converted, and the phase difference θ is calculated as described above.

The phase difference θ is added by 40 °, is converted into phase information indicating the pen pressure, and is transferred to the host computer 49 together with the coordinate values in the X and Y directions of the position indicated by the input pen 20 described above.

When the first coordinate detection operation and the phase detection operation are completed in this way, the control circuit 30 performs the second and subsequent coordinate detection operations as shown in FIG. Of the loop coils 11-48, the information for selecting only a certain number of loop coils around the loop coil at which the maximum detection voltage is obtained, for example, only 10 loop coils, is selected by the selection circuit 32.
And the Y-direction loop coils 12-1 to 12-48
Out of the loop coil at which the maximum detection voltage is obtained, a fixed number of values before and after that, and information for selecting only the ten loop coils are sent to the selection circuit 33, and the output value is obtained in the same manner as described above. To perform a coordinate detection operation and a phase detection operation in the X and Y directions of the position indicated by the input pen 20;
The obtained coordinate values and phase information are transferred to the host computer 49, and thereafter, these are repeated.

In addition, if the level check described above is explained in detail,
Check whether the maximum value of the detection voltage has reached the detection level and which loop coil has the maximum value of the detection voltage, and if the detection level has not been reached, stop the subsequent coordinate calculation and the like. This is a process of setting the center of the loop coil to be selected in the next coordinate detection operation and phase detection operation.

As one of interpolation calculation methods for obtaining a coordinate value in the X direction or the Y direction, for example, the coordinate value xp, the detection voltages Vx1 to Vx4
There is a method of approximating the waveform near the maximum value of 8 with an appropriate function and finding the coordinates of the maximum value of the function.

For example, in FIG. 6 (c), the maximum detection voltage Vx3
, And the detection voltages Vx2 and Vx4 on both sides thereof can be calculated as follows by approximation by a quadratic function (however, the coordinate values of the center positions of the loop coils 11-1 to 11-48 are x1 to
x48, and the interval is Δx. ). First, from the voltages and coordinate values, Vx2 = a (x2-xp) ² + b (2) Vx3 = a (x3-xp) ² + b (3) Vx4 = a (x4-xp) ² + b ... (4) Here, a and b are constants (a <0). X3−x2 = Δx (5) x4−x2 = 2Δx (6) Substituting the equations (5) and (6) into the equations (3) and (4) and rearranging them, xp = x2 + Δx / 2 ｛(3Vx2−4Vx3 + Vx4) / (Vx2-2−Vx3 + V
x4)｝ …… (7)

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. The coordinate value xp of the input pen 20 can be calculated by performing an operation corresponding to the equation (7) from the coordinate value (known) of the previous loop coil.

On the other hand, according to the flowchart shown in FIG. 9, the host computer 49 stores only the data having the phase information of 1 ° or more among the data transmitted from the control circuit 30 as valid data, and further stores the phase information in the designated position ( Coordinate point)
Is converted to a diameter of a circle (for example, converted to a value proportional to phase information), and the diameter is converted to a coordinate position based on the coordinate values in the X direction and the Y direction in an image memory (not shown). An image of a circle having the circle is drawn, and this is displayed on the display device 50.

Since the above process is repeated while data is transferred from the control circuit 30, when the input pen 20 is moved while changing the pen pressure, the diameter differs along the locus 60 of the designated position as shown in FIG. The images 61 of the circles are continuously arranged, and an image as if using a brush is obtained. Note that the obtained image can be hard-copied by the output device 51 if necessary, and FIG. 11A shows an example of the output result. Further, if the process of filling the inside of the circle is performed,
As shown in FIG. 11A, a more natural output result can be obtained.

In the above-described embodiment, a circle is used as the graphic indicating the position indicated by the input pen 20.However, an ellipse, a rectangle, or the like may be used.Also, by changing the program of the host computer 49, the phase information can be any information, For example, it can be converted into information indicating hue and lightness (density) at the designated position, and can be applied to various designs and the like.

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 tuning circuit is tuned to a position indicator having a tuning circuit whose tuning frequency is continuously changed by the radio wave generating means of the tablet in accordance with the operation. A radio wave to be obtained is generated, and at this time, a radio wave due to the tuning reflected from the tuning circuit is detected by the radio wave detecting means of the tablet, and further, by the coordinate calculating means, regardless of the operation, on the tablet of the position indicator. The coordinate value of the indicated position is calculated with a finer accuracy than the spacing between the plurality of loop coils, and the position of the electric wave reflected from the position indicator by the phase difference detecting means on the tablet and the electric wave generated by the electric wave generating means is calculated. Since the operation of the operator is detected by detecting the phase difference, the position indicator may be provided with a passive element such as a coil or a capacitor to achieve a tuning circuit. There is no need for a cord, so that the cord is not entangled or broken due to fatigue, and heavy parts such as batteries and magnets are not required, resulting in light weight and low cost. In addition, the trouble of replacing the battery is eliminated, the operability is extremely improved, the coordinate value on the tablet can be detected regardless of the operation of the operator, and the radio wave generated for the tuning circuit and reflected from the tuning circuit are reflected. The operation of the operator that can continuously change parameters other than the coordinate value in addition to the detection of the coordinate value by the phase difference with the radio wave, for example, the pen pressure can be detected, and the change of the tuning frequency in the tuning circuit can be used. As described above, a pressure-sensitive sensor is not provided over the entire coordinate input range as in the related art, and the operator can accurately detect any part of the coordinate input range. There is an advantage of, or the like can detect the work.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a coordinate input method and an apparatus therefor according to the present invention, FIG. 2 is a detailed block diagram of a loop coil group in the X and Y directions of a tablet, and FIG. FIG. 4 is a signal waveform diagram of each part in FIG. 1, FIG. 5 is a flowchart of processing in the control circuit, and FIGS. 6 (a) and (b)
FIG. 7C is a timing chart showing a basic coordinate detecting operation in the control circuit, FIG. 7 is a diagram showing a detected voltage obtained from each loop coil at the time of the first coordinate detecting operation, and FIG. FIG. 9 is a timing chart showing a coordinate detection operation and a phase detection operation after the first time, FIG. 9 is a flowchart of processing in the host computer, FIG. 10 is a diagram showing an image when the input pen is moved while changing the pen pressure, FIG. (A), (b) is a figure which shows an example of an output result. 10 ... tablet, 11 ... loop coil group in X direction, 12
... Y-direction loop coil group, 20 ... Input pen, 24 ...
Coil, 27: Capacitor, 28: Tuning circuit, 30: Control circuit, 31: Signal generation circuit, 32: Selection circuit in X direction, 33: Selection circuit in Y direction, 34, 35 ... Switching circuit, 36 XY switching circuit, 37 Reception timing switching circuit, 38 Bandpass filter, 39 Detector, 40, 43, 44
Low-pass filters, 41, 42: Phase detector, 49: Host computer, 50: Display device.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Toshihide Sento 5-23-4 Sakurada, Washinomiya-cho, Kita-Katsushika-gun, Saitama

Claims (6)

(57) [Claims] 1. A coordinate input method for transmitting and receiving signals between a position indicator and a tablet and detecting coordinate values on the tablet indicated by the position indicator, comprising a plurality of loop coils of the tablet. A radio wave is generated from the generated radio wave generating means, and a frequency that can be tuned to the radio wave is set as a tuning frequency, a position to be measured is instructed to the tablet, and the tuning frequency changes continuously according to an operation of the operator. The radio wave is reflected by a position indicator, and the reflected radio wave is detected by radio wave detecting means composed of a plurality of loop coils of the tablet. A coordinate value of a position indicated by the position indicator on the tablet is calculated regardless of the operation with a precision finer than an arrangement interval of the plurality of loop coils, and the detection is performed. Detecting a phase difference between an induced voltage and a radio wave generated by the radio wave generating means, detecting a continuous change in a tuning frequency in the tuning circuit, and detecting an operation of an operator on the position indicator. Coordinate input method. 2. The coordinate input method according to claim 1, wherein a pen pressure applied to the position indicator is used as an operation of the operator. 3. A coordinate input device for transmitting and receiving signals between a position indicator and a tablet, and detecting coordinate values on the tablet indicated by the position indicator, wherein the position of the tablet to be measured is determined. And a position indicator having a tuning circuit for continuously changing the tuning frequency in accordance with the operation of the operator and notifying the operation of the operator, and a plurality of loop coils, wherein the tuning circuit is tuned. A tablet having radio wave generating means for generating a radio wave that can be generated and a radio wave detecting means for detecting a radio wave caused by the tuning reflected from the tuning circuit; and guiding the plurality of loop coils constituting the radio wave generating means by the reflection. In accordance with the plurality of induced voltages, the position finger is irrespective of the operation by a predetermined interpolation calculation process with a finer accuracy than the arrangement interval of the plurality of loop coils. A coordinate calculating means for obtaining a coordinate value of a designated position on the tablet of the device; a radio wave generated by a loop coil constituting the radio wave generating means; and an induced voltage induced by the reflection in a loop coil constituting the radio wave detecting means. And the phase difference between
A coordinate input device comprising: a phase difference detecting unit configured to detect a continuous change of a tuning frequency in the tuning circuit to detect an operation of an operator on the position indicator. 4. The coordinate input device according to claim 3, wherein the radio wave generating means and the radio wave detecting means are operated alternately. 5. The coordinate input device according to claim 4, wherein the loop coil constituting the electric wave generating means and the loop coil constituting the electric wave detecting means are used in combination. 6. A position indicator having a tuning circuit for indicating a position to be measured to the tablet and continuously changing a tuning frequency according to the pen pressure to notify the pen pressure is used. Claims 3 to 5
The coordinate input device according to any one of the above items.