JPH054034Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to an input pen of a coordinate input device that can extract information according to pen pressure.

(Prior art) Conventional input pens of this type have a pressure sensor made of pressure-sensitive conductive rubber or the like installed at the rear end of a core body that is slidably housed in the pen axis direction. There was one in which the applied pressure (pen pressure) was detected by the pressure-sensitive sensor.

(Problem to be solved by the invention) However, the input pen requires a cable to retrieve the output information (resistance value, voltage value, current value, etc.) from the pressure-sensitive sensor, making it difficult to operate when inputting data. There was a problem.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned problems and provide an input pen for a coordinate input device that does not require a cable and can obtain information that accurately corresponds to pen pressure.

(Means for Solving the Problem) In order to achieve the above object, in claim 1 of the present invention, the coordinate input device is used in a coordinate input device to indicate the position to be measured to a tablet, and to continuously input data by operation. an input pen for transmitting a change in state to the tablet;
A ferrite having a ferrite tip, a core body which is held so as to be continuously displaced and recoverable in the direction of the pen axis according to writing pressure, and a through hole in which the core body can be slidably accommodated. A tuned circuit includes a coil wound around a core and a capacitor connected to the coil, the first and second ferrite chips are respectively disposed near both ends of the ferrite core, and the tuned circuit includes a tablet. In claim 2, there is provided an input pen for a coordinate input device, which is tuned to radio waves emitted from the tablet and notifies the tablet of the displacement of the core body due to pen pressure by the reflected radio waves. The ferrite chip is arranged so that when the core body is not displaced, approximately 2/3 of the entire chip is housed within the ferrite core, and when the core body is displaced the most, the entirety of the ferrite chip is housed within the ferrite core, and, When the core body is not displaced, one end of the second ferrite chip touches the end of the ferrite core, and when the core body is displaced the most, its one end is separated from the end of the ferrite core by the amount of displacement, and the entire body is An input pen for a coordinate input device according to claim 1, wherein the input pen is arranged outside the ferrite core.

(Function) According to claim 1 of the present invention, when writing pressure is applied to the pen, the core is displaced in the pen axis direction according to the writing pressure, and at this time, the first and second ferrite tips are coiled. is displaced relative to both ends of the ferrite core, and the magnetic permeability of the ferrite core, that is, the coil, changes according to the amount of displacement, and its inductance changes. As a result, the tuning frequency of the tuning circuit made up of the coil and capacitor changes slightly, which changes the phase and frequency of the induced voltage based on the radio waves transmitted from the coordinate input device.
Information corresponding to the displacement amount, that is, the pen pressure is extracted on the coordinate input device side from the radio waves transmitted from the coil based on the induced voltage after the change. Moreover, according to claim 2, the change in magnetic permeability corresponding to the amount of displacement of the core body can be made the largest, and the change in the tuning frequency can be made the largest.

(Embodiment) FIG. 1 shows an embodiment of the input pen of the present invention. In the figure, 11 is a pen shaft made of a non-metallic material such as synthetic resin, and 12 is a ferrite chip 13 and 1.
14 is a coil wound around a ferrite core 15 having a through hole in which the core 12 can be slidably accommodated; 16 is a coil that holds the rear end of the core 12; A lead holder, 17 is a spring that supports the lead holder 16 so as to be slightly displaceable with respect to the pen shaft 11, and 18 is a capacitor.

The coil 14 and capacitor 18 are connected in series with each other to constitute a well-known tuned circuit 19, and the inductance of the coil 14 and the capacitance of the capacitor 18 are such that the tuning (resonance) frequency thereof is approximately at a predetermined frequency. It is set to the value f0. Here, in a state where the core body 12 is held in the core holder 16, the ferrite chips 13 and 1
3' are located at both ends of the coil 14, and when the input pen is operated on a tablet (to be described later), the core 12, that is, the ferrite tips 13 and 13' move according to the writing pressure at that time. As a result, the inductance of the coil 14 changes, and the tuning frequency in the above-mentioned tuning circuit 19 changes slightly.

FIG. 2 shows in detail the positional relationship between the ferrite chips 13 and 13' and the coil 14.
FIG. 2a shows the state when the core body 12 is not pressed at all, and about 2/3 of the entire ferrite chip 13 is housed in the coil 14 (actually, the ferrite core 15), and 1/3 The ferrite chip 13' is arranged so as to protrude outside the coil 14, and the ferrite chip 13' is arranged so that one end thereof contacts the end of the coil 14 and the entire ferrite chip 13' is outside the coil 14. Figure 2b
indicates the state when the core body 12 is slid (pressed) to the maximum extent, and the ferrite chip 1
3 is entirely housed within the coil 14, and
The ferrite chip 13' has one end connected to the coil 14.
The coil 14 is arranged so that the entire coil 14 is spaced apart from the end by the slide amount. Note that the numerical values shown in the drawings are just examples, and it goes without saying that the present invention is not limited thereto.

Also, the reason why two ferrite chips are provided is to increase the amount of change in the inductance of the coil with respect to the sliding amount of the core body 12. The range of phase change can be expanded by about 1.5 to 2 times.

FIG. 3 shows an example of a coordinate input device using the input pen 10 described above, in which 20 is a tablet, 30 is a control circuit, 31 is a signal generation circuit, 3
2 and 33 are X-direction and Y-direction selection circuits, 3
4 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, 40 is a low pass filter (LPF), 41 and 42 are phase detectors (PSD),
43, 44 are low pass filters (LPF), 45, 46
1 is a drive circuit, 47 and 48 are amplifiers, 49 is a host computer, 50 is a display device, and 51 is an output device.

FIG. 4 shows a loop coil group 21 in the X direction and a loop coil group 2 in the Y direction, which constitute the tablet 20.
This figure shows the details of 2. The loop coil group 21 in the X direction consists of a large number, for example, 48 loop coils 21-1, 21-2, . . . 21-48, arranged parallel to each other and overlapping each other along the X direction. The loop coil group 21 and the Y-direction loop coil group 22 are a large number of 48 loop coils arranged parallel to each other and overlapping each other along the Y direction.
Book loop coil 22-1, 22-2,...22
-48 loop coil group 21 in the X direction.
and the Y-direction loop coil group 22 are closely stacked on top of each other (however, in the drawing, they are drawn apart for ease of understanding), and are further housed in a case (not shown) made of a non-metallic material. . Although each loop coil is configured with one turn here, it may be configured with multiple turns as necessary.

Next, the operation of the device will be described along with its configuration. First, the manner in which radio waves are transmitted and received between the input pen 10 and the tablet 20, as well as the signals obtained at this time, will be described with reference to FIG.

The control circuit 30 is composed of a well-known microprocessor or the like, and controls the signal generation circuit 31, and also switches each loop coil of the tablet 20 via the selection circuits 32 and 33 according to the flowchart shown in FIG. It also controls the switching of the coordinate detection direction for the XY switching circuit 36 and the reception timing switching circuit 37, and further converts the output values from the low-pass filters 40, 43, and 44 into analog/digital (A/ D) Convert and execute arithmetic processing to be described later to obtain coordinates input by the input pen 10, detect the phase of the received signal, and send these to the host computer 49.

The selection circuit 32 selects the loop coil group 2 in the X direction.
The selection circuit 33 sequentially selects one loop coil from the loop coil group 22 in the Y direction, and each selects one loop coil from the Y-direction loop coil group 22 according to information from the control circuit 30. It works.

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

The signal generating circuit 31 has a predetermined frequency of 0, for example
A 500kHz rectangular wave signal A, a signal B whose phase is delayed by 90 degrees of the rectangular wave signal A, a predetermined frequency k, e.g.
Generates a 15.625kHz transmission/reception switching signal C and reception timing signal D. The rectangular wave signal A is sent as is to the phase detector 41, and is converted into a sine wave signal E by a low-pass filter (not shown).
Furthermore, the rectangular wave signal B is sent to either the drive circuit 45 or 46 via the XY switching circuit 36, the rectangular wave signal B is sent to the phase detector 42, and the transmission/reception switching signal C is sent to the transmission/reception switching circuits 34 and 35. Furthermore, the reception timing signal D is sent to the reception timing switching circuit 37.

Now, information for selecting the X direction is received from the control circuit 30.
XY switching circuit 36 and reception timing switching circuit 3
7, the sine wave signal E
is sent to the drive circuit 45 and converted into a balanced signal,
Furthermore, the signal is sent to the transmission/reception switching circuit 34, but since the transmission/reception switching circuit 34 switches and connects either the drive circuit 45 or the amplifier 47 based on the transmission/reception switching signal C, the transmission/reception switching circuit 34 outputs the signal to the selection circuit 32. The signal to be generated is time T (=1/2k), here
The signal F is a 500kHz signal that is output and not output every 32μsec.

The signal F is passed through the selection circuit 32 to one loop coil 21-i (i=
1, 2, . . . 48), and the loop coil 21-i generates radio waves based on the signal F.

At this time, if the input pen 10 is held in a substantially upright state on the tablet 20, that is, in a used state,
The radio wave excites the coil 14 of the input pen 10, causing its tuning circuit 19 to generate an induced voltage G synchronized with the signal F.

Thereafter, when the loop coil 21-i is switched to the amplifier 47 side as the signal F enters a no-signal period, that is, the reception period, the radio wave from the loop coil 21-i immediately disappears, but the induced voltage G It gradually attenuates depending on the loss of the tuning circuit 19.

On the other hand, based on the induced voltage G, the tuning circuit 19
The current flowing through causes the coil 14 to emit radio waves. Since the radio waves reversely excite the loop coil 21-i connected to the amplifier 47, an induced voltage due to the radio waves from the coil 14 is generated in the loop coil 21-i. The induced voltage is sent from the transmission/reception switching circuit 34 to the amplifier 47 only during the reception period, is amplified, becomes a reception signal H, and is further sent to the reception timing switching circuit 37.

The reception timing switching circuit 37 has an X direction or a Y direction.
One of the direction selection information, here the X direction selection information, and the reception timing signal D, which is essentially an inverted signal of the transmission/reception switching signal C, are input, and the signal D is at a high (H) level. During the period, the received signal H is output, and during the low (L) level period, nothing is output, so that the signal I (substantially the same as the received signal H) is obtained as the output.

The signal I is sent to a band filter 38, which is a ceramic filter having a natural frequency f0, and the signal I is sent to a band filter 38.
A signal J (strictly speaking, in a state in which several signals I are input to the bandpass filter 38 and converged) having an amplitude corresponding to the energy of the frequency f0 component in the middle is sent to the detector 39 and the phase detectors 41 and 42. do.

The signal J input to the detector 39 is detected and rectified to become a signal K, and then passed through a low-pass filter 40 with a sufficiently low cutoff frequency to a voltage value corresponding to approximately 1/2 of the amplitude, for example, Vx. The DC signal L is converted into a DC signal L and sent to the control circuit 30.

The voltage value Vx of the signal L is a value that depends on the distance between the input pen 10 and the loop coil 21-i, here a value that is approximately inversely proportional to the fourth power of the distance, and when the loop coil 21-i is switched. Therefore, in the control circuit 30, the voltage value Vx obtained for each loop coil is converted into a digital value, and by performing arithmetic processing to be described later on these values,
The input coordinates in the X direction by the input pen 10 are determined. Note that the input coordinates in the Y direction by the input pen 10 are also 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, assuming that the phase of the signal J almost matches the phase of the rectangular wave signal A, the phase detector 41 just inverts the signal J to the positive side and outputs a signal M1 (substantially the same as the signal K). output, and also phase detector 42
outputs a signal M2 having a symmetrical waveform on the positive and negative sides.

The signal M1 is converted by the same low-pass filter 43 to a DC signal N1 (substantially the same as the signal L) having a voltage value corresponding to approximately 1/2 of the amplitude of the signal J, that is, Vx, and then sent to the control circuit 30. Also, the signal M2 is converted into a DC signal N2 by a similar low-pass filter 44 and sent to the control circuit 30, but here, the positive and negative components of the signal M2 from the phase detector 42 are Since they are the same, the output voltage of the low-pass filter 44 is 0 [V].

The control circuit 30 converts the output values of the low filters 43 and 44, here signals N1 and N2, into digital values, and further uses these digital values to perform arithmetic processing according to the following formula 1, and then converts the output values of the low filters 43 and 44 to phase detectors 41 and 4.
The phase difference θ between the signal added to J.2, here J, and the rectangular wave signal A is determined.

θ=-tan ^-1 (VQ/VP) ...(1) However, VP is the digital value corresponding to the output of the low-pass filter 43, and VQ is the digital value corresponding to the output of the low-pass filter 4.
The digital value corresponding to the output of 4 is shown. For example, in the case of the signal J mentioned above, the voltage value of the signal N1 is
Vx, but the voltage value of signal N2 is 0 [V], i.e.
Since VQ=0, the phase difference θ=0°.

Incidentally, the phase of the signal J changes in accordance with the tuning frequency in the tuning circuit 19 of the input pen 10. That is, when the tuning frequency in the tuning circuit 19 matches the predetermined frequency fO, the tuning circuit 19 has a frequency that is equal to the frequency in both the signal transmission period and the reception period.
An induced voltage of fO is generated, and an induced current synchronized with this flows, so that the received signal H (or I)
The frequency and phase of the signal J coincide with the rectangular wave signal A, and the phase of the signal J also coincides with the rectangular wave signal A.

On the other hand, if the tuned frequency in the tuned circuit 19 does not match the predetermined frequency 0, for example, if it is a frequency slightly lower than the frequency 0, for example 1, the tuned circuit 19 will receive an induced voltage at a frequency of 0 during the signal transmission period. occurs, but at that time, the tuning circuit 19
An induced current with a phase lag flows through the signal, and an induced voltage with a frequency of approximately 1 and an induced current synchronized with this flow during the signal reception period. Therefore, the frequency of the received signal H (or I) is a square wave signal. The frequency is slightly lower than that of A, and its phase is also slightly delayed. As mentioned above, the band filter 3
8 has only frequency 0 as its frequency, a shift in the frequency of the input signal toward the lower side will be output as a phase lag. Therefore, the phase of the signal J is equal to the received signal H ( Or it will be even later than I).

Conversely, if the tuning frequency in the tuning circuit 19 is slightly higher than the predetermined frequency 0, for example
2, during the signal transmission period, tuning circuit 1
9, an induced voltage with a frequency of 0 is generated, but at that time, an induced current with a phase lead flows through the tuned circuit 19, and during the signal reception period, an induced voltage with a frequency of approximately 2 and an induced voltage synchronized with this occur. Since a current flows, the frequency of the received signal H (or I) is slightly higher than the frequency of the rectangular wave signal A, and its phase is also slightly advanced. In the bandpass filter 38, a shift in the frequency of the input signal toward the higher side is outputted as a phase advance, contrary to the case described above, and therefore, the signal J
The phase of the received signal H (or I) is further advanced.

As mentioned above, since the tuning frequency of the tuning circuit 19 changes depending on the writing pressure applied to the input pen 10,
The phase difference θ determined by the above equation 1 also changes in accordance with the writing pressure. In this embodiment, when no writing pressure is applied to the input pen 10, the phase difference θ is -
The angle is approximately 80 degrees, and the angle is set in advance so that the angle is approximately 80 degrees when the most pen pressure is applied.

The phase difference θ obtained above is added by 60°, and -20°
After being converted to phase information with values in the range of ~140°,
It is sent to the host computer 49 together with the coordinate values in the direction and the Y direction (the addition of 60 degrees described above may be performed on the host computer 49 side).

Next, with reference to FIGS. 6 to 10, the coordinate detection operation, the phase detection operation, and the conversion of phase information into the spread of coordinate points will be explained in detail.

First, when the entire device is powered on and enters the measurement start state, the control circuit 30 sends information for selecting the X direction to the XY switching circuit 36 and the reception timing switching circuit 37, and also
Information for selecting the first loop coil 21-1 among the loop coils 21-1 to 21-48 in the direction is sent to the selection circuit 32, and the selection circuit 32 selects the first loop coil 21-1.
is connected to the transmission/reception switching circuit 34.

The transmission/reception switching circuit 34 switches the loop coil 21-1 to the driving circuit 45 based on the transmission/reception switching signal C described above.
and the amplifier 47, but in this case,
The drive circuit 45 transmits the seventh signal during the 32 μsec transmission period.
Sixteen sine wave signals of 500 kHz as shown in Figure a are sent to the loop coil 21-1 (only five of them are shown in Figure 4 for convenience of drawing).

The switching between transmission and reception is repeated seven times for one loop coil, here 21-1, as shown in FIG. 7b. The period in which these seven times of transmission and reception are repeated corresponds to the selection period (448 μsec) of one loop coil.

At this time, an induced voltage is obtained at the output of the amplifier 47 for one loop coil every seven reception periods, but this induced voltage is passed through the reception timing switching circuit 37 to the band filter 38 as described above. It is sent out, averaged, and passed through a detector 39 and a phase detector 4.
1 and 42 and low-pass filters 40, 43, and 44, and then sent to the control circuit 30.

The control circuit 30 inputs the output value of the low-pass filter 40 after A/D conversion, and temporarily stores it as a detected voltage depending on the distance between the input pen 10 and the loop coil 21-1, for example, Vx1.

Next, the control circuit 30 sends information for selecting the loop coil 21-2 to the selection circuit 32, connects the loop coil 21-2 to the transmission/reception switching circuit 34, and sets the distance between the input pen 10 and the loop coil 21-2. Obtain a detection voltage Vx2 proportional to and store it, and thereafter, similarly, sequentially connect loop coils 21-3 to 21-48.
The detection voltages Vx1 to Vx48 (however, the 7th
Figure c shows only a part of it in an analog representation. ).

As shown in FIG. 8, the actual detected voltage is obtained only from several loop coils in front and behind the position (xp) where the input pen 10 is placed as the center.

The control circuit 30 checks whether the voltage value of the stored detection voltage is above a certain detection level, and if it is below the certain detection level, selects each loop coil in the X direction and performs voltage detection again. Repeatedly, if the detection level is above a certain level, proceed 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, and switches the selection circuit 33 and the transmission/reception switching circuit 35 in the same manner as described above, thereby controlling the low frequency range when transmitting and receiving radio waves. The input pen 10 obtained by A/D converting the output value of the filter 40 and each loop coil 22-1 in the Y direction
The detected voltage depending on the distance to 22-48 is temporarily stored. After this, perform a level check in the same way as above, and if it is below a certain detection level, check again.
Returning to the selection of each loop coil in the X direction and voltage detection, if it is above a certain detection level, the coordinate values of the input pen 10 in the X and Y directions are determined from the stored voltage value as described later. calculate.

Next, the control circuit 30 selects a loop coil (peak sending information for selecting the coil) to the selection circuit 32 or 33;
The transmission and reception of the radio waves is repeated a plurality of times, for example seven times, and the output values obtained from the low-pass 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 60°, converted into phase information, and transferred to the host computer 49 together with the coordinate values of the input pen 10 in the X and Y directions.

When the first coordinate detection operation and phase detection operation are completed in this manner, the control circuit 30 performs the second and subsequent coordinate detection operations as shown in FIG. 21-
Among the 48 loop coils, a certain number of loop coils, for example 10, are placed around the loop coil where the maximum detected voltage was obtained.
Information for selecting only the main loop coil is sent to the selection circuit 32, and the loop coil 22 in the Y direction is also sent to the selection circuit 32.
Among -1 to 22-48, information for selecting only 10 loop coils, which are a certain number before and after the loop coil for which the maximum detected voltage was obtained, is sent to the selection circuit 33, and the same as above. The output value is obtained, coordinate detection operations in the X direction and Y direction, and phase detection operation are performed for the input pen 10, and the obtained coordinate values and phase information are transferred to the host computer 49, and these steps are repeated hereafter.

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

Coordinate values in the X direction or Y direction, for example, the above coordinate values
One method of calculating xp is to approximate the waveform near the maximum value of the detected voltages Vx1 to Vx48 by an appropriate function, and then find the coordinates of the maximum value of the function.

For example, in Figure 7c, the maximum detected voltage
By approximating Vx3 and the detection voltages Vx2 and Vx4 on both sides thereof by a quadratic function, it can be calculated as follows (however, each loop coil 21-1 to 21
The coordinate values of the center position of -48 are set as x1 to x48, and the interval between them is set as Δx. ). First, from each voltage and coordinate value, Vx2 = a (x2 - xp) ² + b ... (2) Vx3 = a (x3 - xp) ² + b ... (3) Vx4 = a (x4 - xp) ² + b ... …(4) becomes. Here, a and b are constants (a<0). Also, x3−x2=Δx ……(5) x4−x2=2Δx ……(6). Substituting equations 5 and 6 into equations 3 and 4 and rearranging, xp=x2+Δx/2{(3Vx2−4Vx3+Vx4)/
(Vx2−2Vx3+Vx4)} ...(7).

Therefore, from each detection voltage Vx1 to Vx48, extract the maximum detection voltage obtained during the level check and the detection voltages before and after it, and combine these with the loop coil from which the maximum detection voltage was obtained. The coordinate value xp of the input pen 10 can be calculated by performing an operation corresponding to the above-mentioned formula 7 from the coordinate value (immediately known) of the previous loop coil.

On the other hand, according to the flowchart shown in FIG. 10, the host computer 49 stores only the data of the phase information of 1° or more as valid data among the data sent out from the control circuit 30, and further stores the phase information as the coordinates. Convert point spread information, for example, to a diameter of a circle proportional to the coordinate information, draw an image of a circle having the diameter at a coordinate position based on the coordinate value in the X direction in an image memory (not shown), and display this on a display device. 50.

Since the above process is repeated while data is being transferred from the control circuit 30, when the input pen 10 is moved while changing the pen pressure, the diameters differ along the locus 60 of the coordinate points as shown in FIG. The circular images 61 are arranged continuously, and an image similar to that obtained when a brush is used is obtained. Note that the obtained image can be made into a hard copy from the output device 51 if necessary, and an example of the output result is shown in FIG. 12a. Moreover, if the inside of the circle is filled in, a more natural output result can be obtained as shown in FIG. 12b.

In the above embodiment, the change in pen pressure was converted to the spread of coordinate points, but it can be converted to any information by changing the program on the host computer side. For example, the change in pen pressure can be converted to arbitrary information. It is also possible to change the hue, brightness, etc. of a predetermined area according to the pressure of the pen, which can be applied to various designs.

(Effect of the invention) As explained above, according to claim 1 of the invention, the first and second ferrite chips are displaced with respect to both ends of the ferrite core of the coil in accordance with the displacement of the core, and The magnetic permeability of the fate core, that is, the coil, changes depending on the amount of displacement, which changes the tuning frequency of the tuning circuit made up of the coil and capacitor, so position detection is performed by transmitting and receiving radio waves from the tablet. It is possible to use the coordinate input device to extract information corresponding to the change in the tuning frequency, that is, the pressure of the pen. Therefore, there is no need for a cable between the coordinate input device and the cable, unlike in the past, when the cable moves. It will not get in the way or break due to fatigue, and since the change in the tuning frequency depends only on the amount of displacement of the core, accurate information according to the pen pressure can be obtained at any part of the tablet. can be obtained. Further, since it is composed of only small and lightweight parts such as a coil, a capacitor, a ferrite core, and a ferrite chip, it has the advantage that the above-mentioned cable is not required and the operability during input is extremely good.

Further, according to claim 2 of the present invention, when the core body is not displaced, about two-thirds of the first ferrite chip is housed in the ferrite core, and when the core body is displaced the most, the first ferrite chip is housed within the ferrite core. The second ferrite chip is arranged so that the whole is housed within the ferrite core, and one end of the second ferrite chip is in contact with the end of the ferrite core when the core is not displaced, and one end of the second ferrite chip is in contact with the end of the ferrite core when the core is displaced the most. Since the core is arranged so that it is separated from the end of the ferrite core by the amount of displacement and the entire core is outside the ferrite core, the amount of displacement of the core, that is, the change in magnetic permeability with respect to writing pressure, that is, the change in tuning frequency is maximized. This has the advantage that more information can be transmitted to the coordinate input device.

[Brief explanation of the drawing]

Figure 1 is a sectional view showing an embodiment of the input pen of the present invention, Figures 2 a and b are diagrams showing the positional relationship between the ferrite chip and the coil, and Figure 3 is coordinate input using the input pen of the present invention. A configuration diagram showing an example of the device, Figure 4 is a detailed configuration diagram of the loop coil group in the X direction and Y direction of the tablet, Figure 5 is a signal waveform diagram of each part of Figure 3, and Figure 6 is a diagram of the control circuit. Processing flowcharts, Figures 7a, b, and c are timing diagrams showing basic coordinate detection operations in the control circuit, and Figure 8 shows detection voltages obtained from each loop coil during the first coordinate detection operation. Figure 9 is a timing diagram showing the coordinate detection operation and phase detection operation from the second time onwards, Figure 10 is a flowchart of the process in the host computer, and Figure 11 is the case where the input pen is moved while changing the pen pressure. Figures 12a and 12b are diagrams showing an example of the output results. 10... Input pen, 12... Core body, 13,1
3'...Ferrite chip, 14...Coil, 1
8... Capacitor.

Claims (1)

[Claims for Utility Model Registration] (1) An input pen used in a coordinate input device to instruct a tablet as to the position to be measured and to transmit continuous state changes caused by operations to the tablet. a core body having first and second ferrite chips and held so as to be continuously displaced and recoverable in the direction of the pen axis in response to writing pressure; and a core body slidably housed inside the core body. the first and second ferrite chips each have a coil wound around a ferrite core having a through-hole to obtain the ferrite core, and a tuning circuit including a capacitor connected to the coil; an input coordinate input device, wherein the tuning circuit is tuned to radio waves emitted from the tablet, and notifies the tablet of displacement of the core body due to pen pressure by reflected radio waves. pen. (2) About 2/3 of the first ferrite chip is housed within the ferrite core when the core is not displaced, and the entire first ferrite chip is housed within the ferrite core when the core is displaced the most. The second ferrite chip has one end in contact with the end of the ferrite core when the core is not displaced, and one end that is in contact with the end of the ferrite core when the core is displaced the most. A claim characterized in that the ferrite core is arranged so as to be entirely outside the ferrite core at a distance of a certain amount.
(1) Input pen for the coordinate input device mentioned above.