JP2513676B2 - Coordinate input device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a coordinate input device capable of detecting which of a plurality of position indicators is being used.

(Prior Art) Conventionally, as a position indicator used in a coordinate input device (digitizer), there is a stylus pen (hereinafter, simply referred to as a pen), a cursor, or the like.

Generally, a pen often has a built-in core for writing such as a ballpoint pen at its tip and is used for inputting handwritten characters.The cursor has a perspective indicator at one end. You can trace the shapes drawn in advance,
It was often used to specify a predetermined position, but the signals exchanged between the pen and tablet or the cursor and tablet for position (coordinate) detection, such as radio waves and magnetic bias, are not It was usually the same.

Therefore, for example, when the coordinate input device is used to alternately perform the handwriting character recognition process and the normal coordinate input process, conventionally, a command (information) indicating each of the processing modes is input from a keyboard or the like. Position detection by sending on / off of a switch or the like provided on the pen or cursor via a code, or by sending on / off of the switch or the like via a wireless signal such as infrared rays. The processing mode of the circuit or its upper device is specified.

(Problems to be Solved by the Invention) However, in the case of inputting a command, the input operation is required for each process, that is, every time when the pen and the cursor are replaced, the work becomes complicated, and the code is input from the pen or the cursor. In the case of transmitting an on / off signal of a switch or the like by using the cord, the code deteriorates the operability of a pen or a cursor, and ultrasonic waves or infrared rays are used to turn on or off the switch or the like.
In the case of a device that sends an off signal, it is necessary to install these transmitters, signal generation circuits, batteries, etc. on the pen or cursor itself, which complicates the configuration, makes it large and heavy, and frequently replaces and recharges the batteries. There is a problem in that they impair the operability of the pen and cursor.

An object of the present invention is to provide a coordinate input device capable of detecting which of a plurality of position indicators is being used without deteriorating the operability of each position indicator.

(Means for Solving the Problems) In order to achieve the above object, in the first invention, a plurality of positions each having one of a plurality of tuning circuits that are tuned to a radio wave of one frequency and have different internal losses from each other are provided. A coordinate input device for detecting which one of the indicators is being used, which is a radio wave transmitting means for transmitting a radio wave of the one frequency, and the position indicator synchronized with the radio wave transmitted from the radio wave transmitting means. The radio wave receiving means for receiving the radio wave caused by the tuning reflected from the tuning circuit and the attenuation detecting means for detecting the attenuation of the radio wave received by the radio wave receiving means are detected by the attenuation detecting means. A coordinate input device is proposed which detects which of the plurality of position indicators is being used based on the attenuation of radio waves.

Also, in the second invention, a plurality of position indications each having one of a plurality of tuning circuits that are tuned to a radio wave of one frequency and have mutually different internal losses and the resonance frequency slightly changes according to the state. A coordinate input device that detects which one of the devices is being used and the operating state of each position indicator, and a radio wave transmitting means for transmitting a radio wave of the one frequency, and the radio wave transmitting means. Radio wave receiving means for receiving the radio wave caused by the tuning reflected from the tuning circuit of the position indicator in synchronization with the transmitted radio wave, attenuation detecting means for detecting attenuation of the radio wave received by the radio wave receiving means, and A radio wave detected by the attenuation detection means, which has a phase difference detection means for detecting a phase difference between the radio wave transmitted from the radio wave transmission means and the radio wave received by the radio wave reception means. Among the plurality of position indicators than the attenuation, and detects one is being used,
A coordinate input device is proposed which detects the operation state of each position indicator from the phase difference of the radio waves detected by the phase difference detecting means.

(Operation) According to the first invention, when any one of the plurality of position indicators is used, the tuning circuit of the position indicator tunes to the radio wave of one frequency transmitted from the radio wave transmitting means, Reflects similar radio waves due to tuning. The radio wave reflected from the tuning circuit is gradually attenuated, and the decaying radio wave is received by the radio wave receiving means, but the attenuation follows the loss in the tuning circuit. Here, since the loss of each position indicator differs from each other, the attenuation of the radio wave received by the radio wave receiving means also differs for each position indicator. The attenuation difference between the radio waves is detected by the attenuation detecting means, which tuning circuit receives the radio wave, and which position indicator is used.

According to the second aspect of the invention, the resonance frequency of the tuning circuit changes when the operating state of the position indicator changes. At this time, since the phase difference between the radio wave transmitted from the radio wave transmitting means and the radio wave received by the radio wave receiving means follows the resonance frequency of the tuning circuit, the phase difference detecting means detects the change in the resonance frequency in the tuning circuit and The operating state of the indicator is detected.

(Embodiment) FIG. 1 shows an embodiment of the coordinate input device of the present invention, in which 1 is a tablet, 2 and 3 are position indicators, 4 is a position detection circuit, and 5 is a timing control circuit. is there.

The tablet 1 is composed of a non-magnetic metal casing 11 to which a tablet body 12 and an antenna coil 13 are attached. The tablet body 12 is connected to a position detection circuit 4, and the antenna coil 13 is connected to a timing control circuit 5. Has been done.

The tablet body 12 is driven by the position detection circuit 4 and constitutes a detection unit for detecting the position designated by the position indicator 2 or 3, and the tablet body 12 is housed in a substantially central portion of the housing 11. There is. The top panel 11 of the housing 11
A frame 14 drawn in a indicates the coordinate input range.

As the tablet body 12 and the position detection circuit 4,
For example, Japanese Patent Application No. 59-32244 “position detecting device” (see Japanese Patent Application Laid-Open No. 60-176133) or Japanese Patent Application No. 58-238532 “coordinate position detecting device” (Japanese Patent Application No. Kaisho
No. 60-129616) can be used.

The antenna coil 13 includes an insulating coated conductor, the coordinate input range of the tablet body 12, that is, the casing 11 around the frame 14.
It is arranged on the surface of the upper panel 11a. Although it is shown as a coil of one turn in the drawing, it is actually composed of a coil of several turns.

The position indicator 2 is a stylus pen and has a built-in magnetic generator for position specification, for example, a magnet 21 and a tuning circuit 22, and the position indicator 3 is a cursor, which is a magnet for position specification.
Built-in 31 and tuning circuit 32.

FIG. 2 shows the detailed structure of the pen 2. Inside the pen shaft 23 made of a non-metallic material such as synthetic resin, a writing core 24 such as a ballpoint pen and the core 24 are drawn from the tip end thereof. Bar magnet 21 having a through hole capable of slidably accommodating, a coil spring 25, a switch 221, a coil with core 222, and a capacitor 22.
A tuning circuit 22 composed of 3 and 224 is integrally combined and built in, and a cap 26 is attached to the rear end thereof.

The coil 222 and the capacitor 223 are connected to each other in series as shown in FIG. 4 so as to form a well-known resonance circuit, and the numerical values of the coil 222 and the capacitor 223 are a voltage at a predetermined frequency f0. The current phase is set to a value that causes resonance (tuning) in the same phase. Also capacitors
224 is connected in parallel to both ends of the capacitor 223 via the switch 221, and when the switch 221 is turned on, it delays the phase of the current in the above-mentioned resonance circuit and delays the phase of the reception signal described later by a predetermined angle. To do. In addition,
When the switch 221 is pushed into the pen shaft 23 by pressing the tip end of the core body 24 against the input surface of the position detection section 1, the switch 221 is pressed by the rear end thereof via the coil spring 25 and turned on.

FIG. 3 shows a detailed structure of the cursor 3. A ring-shaped magnet 31 is provided at one end of a housing 33 made of a non-metallic material such as synthetic resin, and plastic having a "+" mark on the bottom surface thereof. The transparent index device 34 is attached, and a switch 321 is provided on the side surface near the center. A coil 322 is provided around the index device 34 so as to surround the index device 34, and capacitors 323 and 324 are further incorporated therein. Although the coil 322 is shown as a two-turn coil in the drawing, it is actually composed of several tens of turns. The switch 321, coil 322, capacitors 323 and 3
The tuning circuit 32 is composed of 24.

The coil 322 and the capacitor 323 are connected in series with each other as shown in FIG. 4 to form a well-known resonant circuit. The numerical values of the coil 322 and the capacitor 323 are the voltage and the current at the frequency f0. Is set to a value that resonates (tunes) in the same phase. Also, the capacitor 32
The switch 4 is connected in parallel to both ends of the capacitor 323 via the switch 321, and when the switch 321 is turned on, it delays the phase of the current in the above-mentioned resonance circuit and delays the phase of the received signal by a predetermined angle.

When the coil 222 and the coil 322 are compared, the loss is different due to the presence or absence of the core, the ratio of the diameter of the coil to the length, the resistance value per unit length of the wire forming the coil, and the like. The loss of is much larger than that of the coil 222.

FIG. 4 shows a detailed configuration of the tuning circuits 22 and 32 and the timing control circuit 5. In the figure,
501 is a control circuit, 502 is a timing circuit, 503 is a drive circuit, 504 is a transmission / reception switching circuit, 505 is an amplifier, 506 is a reception timing switching circuit, 507 is a bandpass filter (BPF), 508 is a detector, and 509 and 510 are phase detectors. (PSD), 511, 512 and 513 are low pass filters (LPF).

FIGS. 5 (a), (b) and (c) are signal waveform diagrams in each part of FIG. The operation will be described in detail below.

The control circuit 501 is composed of a well-known microprocessor or the like, controls the timing circuit 502, and outputs the output values from the low-pass filters 511 to 513 in an analog / digital (A /
D) Convert, execute the arithmetic processing described later, and
And identify which one of the cursors 3 is used,
Moreover, the state of the switch 221 or 321 is identified, and this is sent to the position detection circuit 4.

The timing circuit 502 includes a rectangular wave signal A having a predetermined frequency f0 and a signal A ′ obtained by delaying the phase of the rectangular wave signal A by a predetermined angle.
(Not shown), a transmission / reception switching signal B and reception timing signals C1, C2, C3 having a predetermined frequency fk are generated. The rectangular wave signal A is sent to the phase detector 509, converted into a sine wave signal by a low-pass filter (not shown), and driven by a drive circuit 503.
, The rectangular wave signal A ′ is sent to the phase detector 510, the transmission / reception switching signal B is sent to the transmission / reception switching circuit 504, and further, based on the control of the control circuit 501, the reception timing signal C1. , C2, or C3 is sent to the reception timing switching circuit 506.

The sine wave signal sent to the drive circuit 503 is converted into a balanced signal and further sent to the transmission / reception switching circuit 504. The transmission / reception switching circuit 504, based on the transmission / reception switching signal B, drives the drive circuit 503.
And one of the amplifiers 505 alternately
Since the connection is switched to 3, the antenna coil 13 has time T
A signal D that outputs or does not output a sine wave signal having a frequency f0 is input every (= 1/2 fk), and the signal D is transmitted as a radio wave from the antenna coil 13.

At this time, within the coordinate input range 14 of the tablet 1,
When the pen 2 is held in a substantially upright state, that is, in a used state, the radio wave excites the coil 222 of the pen 2 and causes its tuning circuit 22 to generate an induction voltage E synchronized with the signal D.

After that, the antenna coil 13 is switched to the amplifier 505 side by the transmission / reception switching circuit 504, that is, when the reception period starts,
The radio wave from the antenna coil 13 disappears immediately, but the induced voltage E gradually attenuates according to the loss in the tuning circuit 22.

On the other hand, the current flowing through the tuning circuit 22 based on the induced voltage E causes the coil 222 to emit a radio wave. Since the radio wave excites the antenna coil 13 in the opposite direction,
An induction voltage due to the radio wave from the coil 222 is generated in the coil 13. The induced voltage is transmitted / received by the transmission / reception switching circuit 504 only during the reception period.
The signal is sent to the amplifier 505 and amplified to become the reception signal F, which is further sent to the reception timing switching circuit 506.

The reception timing switching circuit 506 has the following bandpass filter 5
07 is for controlling which part of the received signal F is output, and is for receiving the timing signal C1 or C2 or
The reception signal F is output while C3 is at the high (H) level, and nothing is output during the low (L) level.

The reception timing signal C1 is for extracting a signal corresponding to all periods of the reception signal F, and is substantially an inverted signal of the transmission / reception switching signal B. Also, the reception timing signal
C2 is the first predetermined period of the received signal F, for example t (= T /
The signal corresponding to 4) is taken out, and the received signal C3 is taken out for the signal corresponding to the last predetermined period t of the received signal F.

Here, when the reception timing signal C1 is input to the reception timing switching circuit 506, a signal G1 (substantially the same as the reception signal F) is obtained at the output. The signal G1 is sent to the bandpass filter 507, which has a frequency f0.
Is a filter having a pass band centered at, the signal H1 having an amplitude h1 corresponding to the energy of the frequency f0 component in the signal G1 (strictly, several signals G1 are band pass filter 50
(In the state where it is input to 7 and converged) is sent to the detector 508 and the phase detectors 509 and 510.

The signal H1 input to the detector 508 is detected and rectified to be a signal I1, and then a low-pass filter 511 having a sufficiently low cut-off frequency is used to obtain a voltage value Vc1 corresponding to approximately 1/2 of the amplitude h1.
Is converted into a direct current signal J1 having a value of, and sent to the control circuit 501.

On the other hand, the rectangular wave signal A is input to the phase detector 509 as a detection signal. At this time, the switch 221 is off, and the phase of the signal H1 substantially matches the phase of the rectangular wave signal A. Then, it outputs a signal (substantially the same as the signal I1) obtained by inverting the signal H1 to the positive side. This signal is a DC signal having a voltage value corresponding to approximately 1/2 of the amplitude h1 by the same low-pass filter 512 (substantially the same as the signal J1).
Is converted into the control signal and sent to the control circuit 501.

Further, although the rectangular wave signal A ′ is inputted to the phase detector 510 as a detection signal, as described above, the switch 221
Is off and the phase of the signal H1 leads the phase of the rectangular wave signal A'by a predetermined angle, a signal having components on the positive side and the negative side is output. This signal is converted into a DC signal by the low-pass filter 513 similar to the above and sent to the control circuit 501. Here, since the output signal of the phase detector 510 has components on the positive side and the negative side, the low-pass filter is used. 513
The voltage value of the output of is a value that is considerably smaller than the voltage value of the output of the low-pass filter 512.

Here, when the switch 221 of the pen 2 is turned on, the phase of the current flowing through the tuning circuit 22 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 '. Therefore, the output H1 of the band-pass filter 507 at this time is made a signal having components on the positive side and the negative side by the phase detector 509, and the low-pass filter 51
The output of 2 has almost the same voltage value as the output of the low-pass filter 513 when the switch 221 is turned off, but the phase detector 5
The signal is inverted to the positive side by 10 and the low-pass filter 51
Similarly to the above, the output of 3 becomes a DC signal having a predetermined voltage value corresponding to approximately 1/2 of the amplitude h1.

In this way, when the switch 221 is off, the low pass filter 5
A predetermined voltage value is obtained at the output of 12 and switch 221
When is on, a predetermined voltage value is obtained at the output of the low-pass filter 513, so in the control circuit 501, by monitoring the output values of the low-pass filters 512 and 513 when the reception timing signal C1 is selected, It can be detected whether the switch 221 is off or on. When the cursor 3 is used, the ON / OFF state of the switch 321 can be similarly detected.

In addition, the information indicating the on (or off) state of the switch 221 or 321 identified here is information for designating a value to be actually input among the coordinate values detected by the tablet 1 and the position detection circuit 4. used.

On the other hand, when the reception timing signal C2 is input to the reception timing switching circuit 506, a signal G2 is obtained at its output, and at this time, a signal H2 having an amplitude h2 (strictly, Several signals G2 pass bandpass filter 507
Is input and converged) is obtained. Furthermore, when the reception timing signal C3 is input to the reception timing switching circuit 506, a signal G3 is obtained at its output, and at this time, a signal H having an amplitude h3 is output at the output of the bandpass filter 507.
3 (strictly speaking, in the state where several signals G3 are input to the bandpass filter 507 and converged).

Similar to the above, these signals H2 and H3 are detected and rectified by the detector 508 to be signals I2 and I3, and then the low-pass filter 511 has voltage values Vc2 corresponding to approximately 1/2 of the amplitudes h2 and h3, respectively. , Vc3, and converted into DC signals J2 and J3, and sent to the control circuit 501.

Although the reception signal F gradually attenuates as described above, the voltage value Vc2 is proportional to the energy within the first predetermined period t of the reception signal F, and the voltage value Vc3 is the last predetermined period of the reception signal F. Since it is proportional to the energy in t,
The ratio between the voltage values Vc2 and Vc3 represents the degree of attenuation of the received signal F.

Therefore, in the control circuit 501, the reception timing signal C
When 2 is input to the reception timing switching circuit 506, the voltage value Vc2 obtained from the low-pass filter 511 and the reception timing signal
When C3 is input to the reception timing switching circuit 506, the voltage value Vc3 obtained from the low-pass filter 511 is converted into a digital value, and the ratio of these is calculated, whereby the degree of attenuation of the reception signal F can be known. it can.

On the other hand, when the cursor 3 is placed in place of the pen 2 in the coordinate input range 14 of the tablet 1, that is, in the use state, the radio wave emitted from the antenna coil 13 based on the signal D is generated by the cursor 3. Exciting the coil 322 of
The tuning circuit 32 generates an induced voltage K synchronized with the signal D. Similar to the above, the induced voltage K is gradually attenuated when the antenna coil 13 is switched to the amplifier 505 side, but the current flowing through the tuning circuit 32 based on the induced voltage K is the coil 32.
Transmit radio waves from 2.

Since the radio wave excites the antenna coil 13 in the opposite direction, an induced voltage due to the radio wave from the coil 322 is generated in the antenna coil 13. Similar to the above, the induced voltage is sent from the transmission / reception switching circuit 504 to the amplifier 505 to be amplified and becomes the reception signal L only during the reception period, and the reception timing switching circuit 50 is further provided.
Dispatched to 6.

As described above, the reception timing signals C1, C2, and C3 are switched and input to the reception timing switching circuit 506, and the signals M1, M2, and M3 are output corresponding to these. Furthermore, these signals M1, M2 and M3 are
Signal N sent to 07 and having amplitudes n1, n2 and n3 respectively
1, N2 and N3.

Similarly to the above, the signals N1, N2 and N3 are sent to the control circuit 501 via the detector 508, the phase detectors 509, 510 and the low pass filters 511, 512, 513, but the low pass filter 5 corresponding to the signal N1 is transmitted.
From the output values of 12 and 513, switch 321
Is detected, and the attenuation of the received signal L is obtained from the output value of the low pass filter 511 corresponding to the signals N2 and N3 as described above.

Here, the tuning circuit 22 of the pen 2 and the tuning circuit of the cursor 3
When compared with 32, the attenuations of the signals, that is, the induced voltages E and K, differ by the difference in the loss in the coil 222 and the coil 322 described above. Here, the attenuation of the induced voltage K in the tuning circuit 32 is the tuning circuit 22. Is larger than the attenuation degree of the induced voltage E at. The attenuations of the induced voltages E and K are directly reflected in the attenuations of the reception signals F and L, and these attenuations hardly change unless the ambient temperature or the like changes significantly.

Therefore, in the control circuit 501, the tuning circuit 22 of the pen 2
And the attenuation degree of the received signal corresponding to each of the tuning circuits 32 of the cursor 3 are stored in advance, the calculation of the attenuation degree is repeatedly executed during the use of the device, and these are compared to determine the position in use. It is identified whether the indicator is the pen 2 or the cursor 3. Further, the identification result is sent to the position detection circuit 4 together with information indicating the on / off state of the switch 221 or 321.

In the above description, it is described whether the position indicator in use is the pen 2 or the cursor 3 after identifying the on / off state of the switch 221 or 321. , When the reception timing signal C1 is input to the reception timing switching circuit 506, the predetermined voltage value obtained from the low-pass filter 512 or 513 often differs between the tuning circuit 22 and the tuning circuit 32. Timing signal C2
When C3 and C3 are input to the reception timing switching circuit 506, it is discriminated whether the position indicator in use is the pen 2 or the cursor 3 from the voltage values obtained from the low-pass filter 511, and then the tuning circuit. A predetermined voltage value stored in advance corresponding to each of the tuning circuit 22 and the tuning circuit 32 is selected according to the identification result, and when this and the reception timing signal C1 are input to the reception timing switching circuit 506, a low-pass filter 512. And 513 and the voltage value obtained from
It is designed to identify the on / off state of 221 or 321.

Further, the usage state of the pen 2 is defined as a handwriting character recognition processing mode, the usage state of the cursor 3 is defined as a normal coordinate input mode, and command information designating these modes is supplied from the control circuit 501 to the position detection circuit 4. (Or a device above it), the handwriting recognition mode is activated only by bringing the pen 2 held in a substantially upright state onto the coordinate input range 14 of the tablet 1, and the pen Press the tip of 2 against the tablet 1, switch 22
By activating 1 to draw a character, the coordinate value of the handwritten character can be read, and the normal coordinate input mode can be activated simply by placing the cursor 3 on the coordinate input range 14 of the tablet 1. Further, the coordinate value can be input only by moving the switch 321 by aligning the "+" mark of the index unit 34 of the cursor 3 with the position to be input.

In the above-mentioned embodiment, the attenuation degree of each tuning circuit is made different by using the coils having different losses. However, the loss is given by inserting a resistor between the coil and the capacitor, and the attenuation degree of each tuning circuit is increased. Can also be given a difference.

Further, in the above-described embodiment, the case where the pen and the cursor are distinguished has been described as an example. However, a plurality of pens, for example, a pen provided with markers of different colors in an electronic blackboard device or the like, or a plurality of cursors identified, Alternatively, it can be applied to the identification of a plurality of pens and a plurality of cursors.

(Effects of the Invention) As described above, according to the first invention, a plurality of position indicators each having one of a plurality of tuning circuits tuned to a radio wave of one frequency and having different internal losses are provided. , Transmitting and receiving the radio wave of the one frequency from the radio wave transmitting means and the radio wave receiving means, detecting the attenuation of the radio wave reflected from the tuning circuit to detect the loss in the tuning circuit. Since it is now possible to detect whether the position indicator is being used, there is no need to input the type of position indicator from a keyboard, etc. as in the past, and between the position indicator and other circuits. In addition to not requiring a code, each position indicator only needs to be provided with a tuning circuit including a coil and a capacitor, and a complicated signal generating circuit or battery as in the past is not required. Instruction Since it is possible to detect the position indicators in use among the devices, it is possible to specify the processing mode in the position detection circuit or its upper device, for example, according to each position indicator.

According to the second aspect of the invention, one of a plurality of tuning circuits that are tuned to a radio wave of one frequency and have mutually different internal losses and that the resonance frequency slightly changes according to the state
Loss in the tuning circuit by transmitting and receiving the radio wave of the one frequency from the radio wave transmitting means and the radio wave receiving means to the plurality of position indicators each having two, and detecting the attenuation of the radio wave reflected from the tuning circuit. And the change in the resonance frequency of the tuning circuit by detecting the phase difference with the radio wave transmitted from the radio wave transmitting means, and which position indicator is used and the operation based on the results of these detections. Since the state is detected, there is no need to input the type of position indicator from a keyboard, etc.
In addition to the fact that no code is required between the position indicator and other circuits, each position indicator only needs to be provided with a tuning circuit including a coil and a capacitor. A circuit, a battery, and the like are unnecessary, and moreover, the position indicator in use among the plurality of position indicators can be detected and the operation state thereof can be detected.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of a coordinate input device of the present invention, FIG. 2 is a sectional view of a stylus pen, FIG. 3 is a partially cutaway perspective view of a cursor, and FIG. Detailed configuration diagrams of the circuit and the timing control circuit, and FIGS. 5A, 5B, and 5C are signal waveform diagrams of the respective portions in FIG. 1 ... Tablet, 2 ... Stylus pen, 3 ... Cursor, 4 ... Position detection circuit, 5 ... Timing control circuit, 13 ... Antenna coil, 14 ... Coordinate input range, 22,3
2 ... Tuning circuit.

Claims (11)

(57) [Claims] 1. A coordinate input for detecting which of a plurality of position indicators is used, each of which has one of a plurality of tuning circuits tuned to a radio wave of one frequency and having different internal losses. A device, which receives a radio wave originating from the tuning, which is reflected from a radio wave transmitting means for transmitting a radio wave of the one frequency and a tuning circuit of the position indicator which is tuned to the radio wave transmitted from the radio wave transmitting means. The radio wave receiving means and the attenuation detecting means for detecting the attenuation of the radio wave received by the radio wave receiving means, and which one of the plurality of position indicators is detected from the attenuation of the radio wave detected by the attenuation detecting means. A coordinate input device characterized by detecting whether it is being used. 2. The coordinate input according to claim 1, wherein the processing mode designation information in the position detection circuit or its upper device is transmitted in accordance with the detected position indicator. apparatus. 3. The coordinate input device according to claim 1 or 2, wherein the radio wave transmitting means and the radio wave receiving means are operated alternately. 4. The coordinate input device according to claim 3, wherein the coil forming the radio wave transmitting means and the coil forming the radio wave receiving means are used in common. 5. The coordinate input device according to claim 1, wherein a magnet for generating a steady magnetic field is used as the position indicating means. 6. A plurality of position indicators each having one of a plurality of tuning circuits which are tuned to a radio wave of one frequency and have different internal losses and whose resonance frequency slightly changes according to the state. A coordinate input device that detects which one of them is being used and detects the operation state of each position indicator, and a radio wave transmitting unit that transmits a radio wave of the one frequency and a radio wave transmitting unit that transmits the radio wave of the one frequency. Radio wave receiving means for receiving the radio wave caused by the tuning reflected from the tuning circuit of the position indicator in tune with the radio wave; attenuation detecting means for detecting attenuation of the radio wave received by the radio wave receiving means; Means for detecting the phase difference between the radio wave transmitted from the means and the radio wave received by the radio wave receiving means, and reducing the radio wave detected by the attenuation detecting means. It is possible to detect which of the plurality of position indicators is being used, and to detect the operation state for each position indicator from the phase difference of the radio waves detected by the phase difference detecting means. A coordinate input device characterized by. 7. The coordinate input according to claim 6, wherein the designation information of the processing mode in the position detection circuit or its upper device is transmitted in accordance with the detected position indicator. apparatus. 8. The coordinate input device according to claim 6 or 7, wherein the radio wave transmitting means and the radio wave receiving means are operated alternately. 9. The coordinate input device according to claim 8, wherein the coil forming the radio wave transmitting means and the coil forming the radio wave receiving means are used in common. 10. The coordinate input device according to claim 6, wherein a magnet for generating a steady magnetic field is used as the position indicating means. 11. The pen down state is detected by using a tuning circuit in which the resonance frequency slightly changes only when the position indicator is pen down, and the pen down state is detected. A coordinate input device according to any one of paragraphs.