JPS63280323A - State discriminating system for position indicator - Google Patents

Abstract

PURPOSE:To improve the detection precision by providing a position indicator with a changeable tuning circuit and transmitting/receiving the radio wave having its tuning frequency and discriminating the state of the position indicator in accordance with the degree of attenuation and the phase of the reflected signal. CONSTITUTION:A coordinate input device is provided with a tablet 1, a position indicator 2, a position detecting circuit 3, and a timing control circuit 4, and a tablet body 12 and an antenna coil 13 are attached to an enclosure 11 to constitute the tablet 1, and this table 1 is connected to the position detecting circuit 3 and the timing control circuit 4. The radio wave oscillated by the antenna coil 13 is received by a tuning circuit 22 of the position indicator 2 to generate an induced voltage. At this time, the reflected radio wave is transmitted from the tuning circuit 22 to induce a voltage accompanied with attenuation, the phase difference, or the like in said antenna coil 13. Thus, these attenuation and phase are detected to discriminate the state of the position indicator 2.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for identifying the state of a position indicator in a coordinate input device, particularly a cordless position indicator.

(Prior art) The present applicant has proposed a "position detection device" in Japanese Patent Application No. 59-32244 (see Japanese Patent Application Laid-open No. 176133/1982) or a "coordinate position detection device" in Japanese Patent Application No. 58-238532.
(Refer to Japanese Patent Application Laid-open No. 129616/1983),
Cordless position indicator (digitizer)
proposed.

All of the coordinate input devices mentioned above detect the position specified by a position indicator that has a constant magnetic bias source such as a permanent magnet within the coordinate input range of the tablet, so position detection is difficult. Therefore, there was no need to exchange signals, such as radio waves or optical signals, between the position indicator and the position detection circuit.

(Problem to be solved by the invention) However, in actual use, the state of the position indicator that specifies the coordinate position to be input on the tablet (hereinafter referred to as
This is called the pen-down state. ) to the position detection circuit or its higher-level device, the position indicator is equipped with a switch means, an ultrasonic or infrared transmitter, a signal generation circuit, a battery, etc.
Turning on (or off) the switch means when the pen is down
It is necessary to send a timing signal using ultrasonic waves, infrared rays, etc. based on However, there is a problem in that these impair the operability of the position indicator to some extent.

SUMMARY OF THE INVENTION An object of the present invention is to provide a system that can identify the state of a cordless position indicator without compromising its operability at all.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention includes a tablet constituting a coordinate input section, a position indicator such as a cursor, and a coordinate input position for driving the tablet and using the position indicator. In a coordinate input device equipped with a position detection circuit that detects
An antenna coil is provided around the coordinate input range of the tablet, and the position indicator includes a coil and a capacitor, a predetermined frequency is set as the tuning frequency, and the state of the position indicator is determined by internal loss and phase difference between voltage and current. A tuning circuit that can be changed according to the position indicator is provided, and an alternating current signal of a predetermined frequency is applied to the antenna coil to transmit radio waves, and when the transmission of the radio waves is stopped, the radio waves are reflected from the tuning circuit of the position indicator. The state of the tuning circuit is identified by causing the antenna coil to receive radio waves and detecting the attenuation and phase of the reflected signal.

(Function) According to the present invention, the radio waves emitted from the antenna coil are received by the tuned circuit of the position indicator, and at this time, the tuned circuit has an inductor of approximately the same frequency as the signal applied to the antenna coil. Voltage is generated. When the transmission of radio waves from the antenna coil stops, the induced voltage gradually attenuates due to internal loss in the tuned circuit, but at this time, reflected radio waves are reflected from the coil in the tuned circuit based on the current flowing in the tuned circuit. Sent. The reflected radio wave is received by the antenna coil that has stopped transmitting the radio wave, but at this time, the induced voltage generated on the antenna coil side has the same attenuation as the induced voltage in the tuned circuit, that is, the induced voltage in the tuned circuit of the position indicator. It also shows the phase based on the phase difference between the voltage and current in the tuned circuit, but the loss in the tuned circuit and the phase difference between the voltage and current depend on the state of the position indicator. Therefore, by detecting this attenuation and phase, the state of the tuned circuit that transmitted the reflected radio wave, that is, the state of the position indicator, can be identified.

(Example) FIG. 1 shows an outline of a coordinate input device to which the method of the present invention is applied. In the figure, 1 is a tablet, 2 is a position indicator, and 3
4 is a position detection circuit, and 4 is a timing control circuit.

The tablet 1 has a tablet main body 12 and an antenna coil 13 attached to a non-magnetic metal casing 11.
The tablet main body 12 is connected to the position detection circuit 3, and the antenna coil 13 is connected to the timing control circuit 4.

The tablet body 12 is driven by the position detection circuit 3 and constitutes a detection section that detects the position specified by the position indicator 2, and is housed approximately in the center of the housing 11.

Note that the frame 1 drawn on the top panel lla of the housing 11
4 indicates the coordinate input range.

The tablet main body 12 and the position detection circuit 3 may be of any type as long as the position indicator is cordless, but it is preferable to use the device disclosed in the application by the applicant mentioned above.

The antenna coil 13 is formed by disposing an insulated conductor on the coordinate input range of the tablet body 12, that is, on the surface of the top panel lla of the housing 11 around the frame 14. Although the coil is shown as one turn in the drawing, it actually consists of several turns.

The position indicator 2 indicates a cursor corresponding to the device according to the application of the present applicant, and includes a magnetic generator for specifying a position, for example, a magnet 21 and a tuning circuit 22.

FIG. 2 shows the detailed structure of the cursor 2, which includes a housing 23 made of a non-metallic material such as synthetic resin, a ring-shaped magnet 21 at one end, and a plastic material with a "+" indicator on the bottom. A transparent indicator 24 is attached, and switches 221 and 222 are provided on the top and side surfaces. Further, a coil 223 is provided around the indicator 24 so as to surround it, and a resistor 224 and capacitors 225 and 22B are also built in. In addition, although the coil 223 is shown as a two-turn coil in the drawing,
It actually consists of a coil with several tens of turns. The switches 221 and 222. Coil 223. resistance 224
The tuning circuit 22 is constituted by the capacitors 225 and 226.

The coil 223 and capacitor 225 are connected in series to each other via a switch 221, as shown in FIG.
The coil 2 constitutes a well-known resonant circuit.
The numerical values of the capacitor 23 and the capacitor 225 are membrane-distorted to values such that the phases of the voltage and current resonate (synchronize) in the same phase at a predetermined frequency fO. The switch 221 is connected to the coil 223.
and the capacitor 225 or the resistor 224
This is for selecting whether to connect via resistor 22.
When 4 is connected, the circuit loss is greater than when it is directly connected.

Further, a capacitor 226 is connected in parallel to both ends of the capacitor 225 via a switch 222, and when the switch 222 is turned on, the phase of the current in the above-mentioned resonant circuit is delayed by a certain angle, and the phase of the received signal, which will be described later, is delayed. It performs the action of delaying by a predetermined angle.

FIG. 3 shows the detailed configuration of the tuning circuit 22 and timing control circuit 4. In FIG. In the figure, 401 is a control circuit, 402 is a timing circuit, 403 is a drive circuit, 404 is a transmission/reception switching circuit, 405 is an amplifier, 40B is a reception timing switching circuit, and 407 is a bandpass filter (BPF).
), 408 is a detector, 409°410 is a phase detector (P
S D ), 411 , 412 , 41.3 are low pass filters (L P F).

4(a), 4(b), and 4(c) are signal waveform diagrams at each part of FIG. 3. The operation will be explained in detail below.

The control circuit 401 is composed of a well-known microprocessor, etc., and controls the timing circuit 402, performs analog-to-digital (A/D) conversion of the output values from the low-pass filters 4i1 to 413, and further performs arithmetic processing to be described later. , the states of the switches 221 and 222 of the cursor 2 are identified and sent to the position detection circuit 3 or its higher-level device (not shown).

The timing circuit 402 generates a rectangular wave signal A1 with a predetermined frequency fO, and a signal A″ in which the phase of the rectangular wave signal A is delayed by a predetermined angle.
(not shown), a transmission/reception switching signal B of a predetermined frequency fk, and a reception timing signal CI.

Generates C2 and C3. The rectangular wave signal A is sent to a phase detector 409, converted into a sine wave signal by a low-pass filter (not shown), and sent to a drive circuit 403, and the rectangular wave signal A' is sent to a phase detector 410. Further, the transmission/reception switching signal B is sent to the transmission/reception switching circuit 404, and furthermore, one of the reception timing signals C1, C2, C3 is sent to the reception timing switching circuit 40B under the control of the control circuit 401. Ru.

The sine wave signal sent to the drive circuit 403 is converted into a balanced signal and further sent to the transmission/reception switching circuit 404, which selects either the driving circuit 403 or the amplifier 405 based on the transmission/reception switching signal B. In order to alternately connect one side to the antenna coil 13, the antenna coil 1
3 is input with a signal that outputs or does not output a sine wave signal of frequency fO every time T (-1/2fk), and the signal is transmitted from the antenna coil 13 as a radio wave.

At this time, if the switch 221 is connected to the direct connection side and the cursor 2 with the switch 222 turned off is placed within the coordinate input range 14 of the tablet 1, that is, the position can be specified, the radio waves will be transmitted to the cursor. The second coil 223 is excited, and the tuned circuit 22 generates an induced voltage E synchronized with the signal.

After that, the antenna coil 13 is switched by the transmission/reception switching circuit 404.
When the signal is switched to the amplifier 405 side, that is, when the reception period begins, the radio wave from the antenna coil 13 immediately disappears, but the induced voltage E gradually attenuates in accordance with the loss within the tuning circuit 22.

On the other hand, the current flowing through the tuned circuit 22 based on the induced voltage E causes the coil 223 to emit radio waves. Since the radio waves reversely excite the antenna coil 13, an induced voltage is generated in the antenna coil 13 due to the radio waves from the coil 223. The induced voltage is sent from the transmission/reception switching circuit 404 to the amplifier 405 only during the reception period, is amplified, becomes a reception signal F, and is further sent to the reception timing switching circuit 40B.

The reception timing switching circuit 40B is for controlling which part of the reception signal F is output to the following bandpass filter 407, and during the period when the reception timing signal C1, C2, or C3 is at high (H) level, the reception timing switching circuit 40B is used to control which part of the reception signal F is output to the following bandpass filter 407. F, and nothing is output during the low (L) level period.

The reception timing signal C1 is for extracting a signal corresponding to the entire period of the reception signal F, and is substantially an inverted signal of the transmission/reception switching signal B. Further, the reception timing signal C2 is a predetermined period at the beginning of the reception signal F, for example, t (-
The received signal C3 is used to extract a 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 40B, the output is the signal Gl.
(substantially the same as the received signal F) is obtained. The signal Gl
is sent to a bandpass filter 407, which is a filter having a pass band centered at the frequency fO, and a signal H1 (strictly In this case, several signals Gl are input to a bandpass filter 407 and in a converged state) are sent to a detector 408 and a phase detector 409 and 410.

The signal H1 input to the detector 408 is detected and rectified to become a signal 11, and then passed through a low-pass filter 411 with a sufficiently low cutoff frequency to have a voltage value Vel corresponding to approximately 1/2 of the amplitude h1. It is converted into a DC signal J1 and sent to the control circuit 401.

On the other hand, the rectangular wave signal A is inputted to the phase detector 409 as a detected signal, but as described above, the switch 222 is off and the phase of the signal H1 is almost the same as the phase of the rectangular wave signal A. If the signal H is exactly
A signal obtained by inverting 1 to the positive side (substantially the same as signal 11) is output. This signal is converted by the same low-pass filter 412 to a DC signal (substantially the same as the signal Jl) having a voltage value corresponding to approximately 1/2 of the amplitude hl, and sent to the control circuit 401.

Further, the rectangular wave signal A' is inputted to the phase detector 410 as a detection signal, but as described above, the switch 22
2 is off and the phase of the signal H1 (almost the same as the phase of the received signal F) leads the phase of the square wave signal A' by a predetermined angle, then a signal having components on the positive side and the negative side Output. This signal is filtered through the same low-pass filter 413 as described above.
However, since the output signal of the phase detector 410 has components on the positive and negative sides, the voltage value of the output of the low-pass filter 413 is converted to a DC signal and sent to the control circuit 401. This value is considerably smaller than the voltage value of the output of 412.

Here, when the switch 222 of cursor 2 is turned on,
The phase of the current flowing through the tuned circuit 22 is delayed by a certain angle with respect to the induced voltage E. -The phase of the received signal F is delayed by a predetermined angle, that is, it almost matches the phase of the rectangular wave signal A-. Therefore, the output H1 of the bandpass filter 407 at this time is converted into a signal having components on the positive side and the negative side by the phase detector 409, and the output of the low-pass filter 412 is converted into a signal having components on the positive side and the negative side. The output of the low-pass filter 413 has almost the same voltage value as the output, but it is inverted to the positive side by the phase detector 410, and the output of the low-pass filter 413 has a predetermined voltage value corresponding to approximately 1/2 of the amplitude h1 as before. It becomes a DC signal with

In this way, when the switch 222 is off, a predetermined voltage value is obtained at the output of the low-pass filter 412, and when the switch 222 is on, a predetermined voltage value is obtained at the output of the low-pass filter 413. In the control circuit 401, the low-pass filter 41 when the reception timing signal C1 is selected.
By monitoring the output values of 2 and 413, it is possible to detect whether switch 222 is off or on.

Note that the information indicating the on (or off) state of the switch 222 identified here is used as information for specifying the value to be actually input among the coordinate values detected by the tablet 1 and the position detection circuit 3. be done.

On the other hand, when the reception timing signal C2 is input to the reception timing switching circuit 40B, the signal G2 is obtained at its output, and at this time, the output of the bandpass filter 407 is a signal H2 (strictly speaking, the number ) is obtained when the signals G2 are input to the bandpass filter 407 and converged. Furthermore, when the reception timing signal C3 is input to the reception timing switching circuit 406, the signal G3 is obtained at its output, and at this time, the output of the bandpass filter 407 is the signal H3 (strictly speaking, , several signals G3
is input to the bandpass filter 407 and in a converged state) is obtained.

These signals H2 and H3 are detected and rectified by the detector 408 as described above, and the signals 12. I3, then the low-pass filter 411 converts the amplitude h2. DC signal J2 having voltage values V C2 and V C3 corresponding to approximately 1/2 of h3, respectively.
．． J3 and sent to the control circuit 401.

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

Therefore, in the control circuit 401, the voltage value Vc2 obtained from the low-pass filter 411 when the reception timing signal C2 is input to the reception timing switching circuit 40G, and the voltage value Vc2 obtained from the low-pass filter 411 when the reception timing signal C3 is inputted to the reception timing switching circuit 40B, Voltage value Vc obtained from 411
3 into digital values and calculate the ratio of these values, it is possible to know the degree of attenuation of the received signal F.

Here, when the switch 221 of the cursor 2 is connected to the resistor 224 side, an induced voltage K synchronized with the signal is generated in the tuned circuit 22. As described above, the induced voltage gradually attenuates when the antenna coil 13 is switched to the amplifier 405 side, but the current flowing through the tuned circuit 22 based on the induced voltage K causes the coil 223 to emit radio waves, and the radio waves Since the antenna coil 13 is excited in the opposite direction, an induced voltage is generated in the antenna coil 13 by the radio waves from the coil 223. As described above, the induced voltage is sent from the transmission/reception switching circuit 404 to the amplifier 405 only during the reception period, where it is amplified and becomes a reception signal.
Sent to 0B.

As mentioned above, the reception timing switching circuit 40B has the reception timing signals C1, C2, and C3 switched input, and the signals M1, M2, and M3 corresponding to these are inputted to the reception timing switching circuit 40B.
is output. Furthermore, these signals Ml, M2 and M3 are sent to a bandpass filter 407, each with an amplitude n
This results in signals N1, N2 and N3 having 1, n2 and n3.

The signals Nl, N2 and N3 are detected by the detector 408 as before.
, phase detectors 409, 410 and low-pass filter 411
, 412 and 413 to the control circuit 401, but the low-pass filters 412 and 41 corresponding to the signal Nl
The on/off state of the switch 222 is detected as described above from the output value of No. 3, and the degree of attenuation of the received signal is obtained as described above from the output value of the low-pass filter 411 corresponding to the signals N2 and N3. It will be done.

Here, in the tuned circuit 22, when comparing the state where the switch 221 is connected to the direct connection side and the state where the switch 221 is connected to the resistor 224 side, the signal is increased by the difference in loss in the resistor 224, that is, the induced voltages E and K. Here, the degree of attenuation of the induced voltage is greater than the degree of attenuation of the induced voltage E. The degree of attenuation in the induced voltages E and K is directly reflected in the degree of attenuation of the received signals F and L, and these attenuation degrees hardly change unless the ambient temperature or the like changes significantly.

Therefore, in the control circuit 401, the degree of attenuation of the received signal corresponding to the state where the switch 221 of the tuning circuit 22 is connected to the direct connection side and the state where it is connected to the resistor 224 side is stored in advance, and the attenuation degree of the received signal is stored in advance. During use, by calculating the attenuation degree and comparing them, it is determined whether the switch 221 is on the direct connection side or on the resistor 224 side.

The information indicating the state of the switch 221 identified here is used as processing mode designation information in the position detection circuit 3 or its higher-level device, and the information indicating the on/off state of the switch 222 is used in the position detection circuit 3. Or sent to the higher-level device.

In addition, in the explanation so far, the on/off state of the switch 222 is identified, and then the state of the switch 221 is identified, but if the loss in the tuned circuit is different, capacitors with the same capacitance value Even if When the reception timing signals C2 and C3 are input to the reception timing switching circuit 40B, the switch 22 is selected from the voltage values obtained from the low-pass filter 411.
1 state is identified, and then a predetermined voltage value stored in advance corresponding to each state of the switch 221 is selected according to the identification result, and this and the reception timing signal CI are used to determine the reception timing. The on/off state of the switch 222 is determined by comparing the voltage values obtained from the low-pass filters 412 and 413 when the switching circuit 406 is manually operated.

Furthermore, in the embodiment described above, when identifying whether the switch 222 is on or off, the identification is made by paying attention to changes in the output values of the low-pass filters 412 and 413 based on changes in the phase of the voltage and current in the tuned circuit 22. , the rectangular wave signal A' is a signal delayed by 90 degrees from the phase of the rectangular wave signal A, and the output values of the low-pass filters 412 and 413 (actually, this is the A/D
By performing the arithmetic processing of the following equation (1) using the converted digital value), the rectangular wave signal A and the phase detector 40
9 and 410, that is, the phase difference θ with the received signal F (or K), in other words, the phase difference between the voltage and current in the tuning circuit 22 can be calculated, and from this it is possible to calculate whether the switch 222 is turned on or off. (Note that the phase difference between the received signal F (or K) and the rectangular wave signal A and the phase difference between the voltage and current in the tuning circuit 22 are not the same except in the case of θ°, but they are fixed. There is a certain relationship.)
.

θ−−t a n (VQ /VP ) −−(
1) (However, vP is the output value of the low-pass filter 412, VQ
is the output value of the low-pass filter 413) Furthermore, in the above embodiment, two states are set for the degree of attenuation, large and small, and two states are set for the phase difference between the voltage and current: an in-phase state and a certain angle delayed state. We have now set many more states and identified them, including the degree of attenuation and the phase difference between voltage and current. Information can be sent to the position detection circuit 3 or its higher-level device. In this case, the phase difference between voltage and current can be detected with high accuracy by using the above-mentioned equation (1).

(Effects of the Invention) As explained above, according to the present invention, the position indicator has a predetermined tuning frequency, and its internal loss and phase difference between voltage and current are changed according to the state of the position indicator. A tuning circuit is provided, which transmits and receives radio waves at the tuning frequency from an antenna coil arranged around the coordinate input range, detects the degree of attenuation and phase of the signal reflected from the tuning circuit, and determines the position. Since the status of the indicator can be identified,
Not only is there no need for a cord between the position indicator and other circuits, but only a tuning circuit including a coil and a capacitor is required, and there is no need for complex signal generation circuits or batteries as in the past. The present invention has advantages such as being able to provide a position pointing device with extremely good operability, being able to identify a large number of states in the position pointing device, and therefore being able to transmit a large amount of information to the position detecting device or its higher-level device.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an outline of a coordinate input device to which the method of the present invention is applied, FIG. 2 is a partially cutaway perspective view of a cursor, and FIG. 3 is a detailed configuration diagram of a cursor tuning circuit and timing control circuit. FIGS. 4(a), 4(b), and 4(c) are signal waveform diagrams of each part of FIG. 3. DESCRIPTION OF SYMBOLS 1... Tablet, 2... Cursor, 3... Position detection circuit, 4... Timing control circuit, 13... Antenna coil, 14... Coordinate input range, 22... Tuning circuit.

Claims (1)

[Scope of Claims] A coordinate input device comprising a tablet constituting a coordinate input section, a position indicator such as a cursor, and a position detection circuit that drives the tablet and detects a coordinate input position by the position indicator, An antenna coil is provided around the coordinate input range of the tablet, and the position indicator includes a coil and a capacitor, a predetermined frequency is set as the tuning frequency, and the internal loss and phase difference between voltage and current are used to determine the state of the position indicator. A tuning circuit that can be changed according to the position indicator is provided, and an alternating current signal of a predetermined frequency is applied to the antenna coil to transmit radio waves, and when the transmission of the radio waves is stopped, the signals reflected from the tuning circuit of the position indicator are transmitted. 1. A state identification system for a position indicator, characterized in that the state of the tuning circuit is identified by causing an antenna coil to receive radio waves and detecting the attenuation and phase of the reflected signal.