JPS63132324A - Reflection type position indicator - Google Patents

Abstract

PURPOSE:To send strong radio waves to a tablet side, to improve an SN ratio and to reduce the influence of radio waves applied from a reflection type position indicator to its periphery by providing the indicator with a circuit to be positively fed back to a tuning circuit built in the indicator itself. CONSTITUTION:Radio waves radiated from an unshown table are received by a coil 152 wound around a ferrite core 13 in the reflection type position indicator 1. A received signal is inputted to the tuning circuit 15 to detect tuning. The detected signal is amplified by an amplifier circuit 16 and positively fed back to the tuning circuit 15 through coils 161, 152. Thereby, an approximately constant inductive voltage is generated in the tuning circuit 15.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a position indicator of a position detection device that detects a position by exchanging radio waves between a tablet and a position indicator.

(Prior art) Prior to filing this application, the applicant filed the patent application No. 61-2139.
No. 70 (filed on September 12, 1986) (hereinafter referred to as the prior application) relates to a position detection device that detects the specified position of a position indicator by exchanging radio waves between a tablet and a position indicator. Proposed.

To briefly explain the content of the earlier application, it is a position detection unit (tablet) consisting of a large number of loop coils arranged in parallel in the position detection direction.
A signal of a predetermined frequency is applied to the negative loop coil to cause the negative loop coil to emit radio waves, and the radio waves are
The signal is received by a tuned circuit that includes a coil and a capacitor provided in the position indicator and has a tuning frequency that is almost the same as the frequency of the signal. The - loop coil whose supply has been stopped receives the signal, detects the induced voltage generated in the - loop coil, repeats this for all the loop coils, and calculates the induced voltage from the obtained large number of induced voltage values. It is designed to detect the position where the induced voltage is maximum, that is, the specified position of the position indicator.

(Problems to be Solved by the Invention) The tuned circuit of the position indicator in the above device consists only of passive elements such as a coil and a capacitor, and the signal generated in the tuned circuit attenuates over time and the coil could only transmit radio waves with a lower output than the radio waves emitted from the loop coil, so in environments with a lot of radio wave interference, noise entering the loop coil from the outside could cause malfunctions, making accurate position detection impossible. was there. In addition, in order to strengthen the radio waves emitted from the coil of the tuned circuit, if the radio waves emitted from the loop coil side are strengthened, the radio waves emitted around the tablet will become stronger, especially if the tablet is large such as an electronic whiteboard device. In this case, the radio waves from this device may adversely affect other devices, and there are also problems in that power consumption increases.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned conventional problems and provide a reflective position indicator capable of amplifying received radio waves and transmitting the amplified radio waves to the tablet side.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention is equipped with a tuning circuit that includes a coil and a capacitor and has a predetermined tuning frequency, and uses the tuning circuit to transmit radio waves emitted from the tablet side. At this time, the coil generates radio waves based on the signal generated in the tuning circuit, and the reflective position indicator amplifies the signal generated in the tuning circuit and sends it back to the tablet side. An amplifier circuit was installed to provide positive feedback to the circuit.

(Function) According to the present invention, the radio waves transmitted from the tablet side are
The signal is received by the tuning circuit of the position indicator, but at this time, the signal generated in the tuning circuit is amplified by an amplifier circuit, positively fed back to the tuning circuit, and sent back to the tablet side as a radio wave from the coil.

(Embodiment) FIG. 1 shows an embodiment of a reflective position indicator (hereinafter referred to as a manual pen) of the present invention.

In the figure, reference numeral 11 denotes a pen-shaped shaft made of a non-metallic material such as synthetic resin, into which a core 12 of a ballpoint pen or the like can be slidably housed. It includes a ferrite core 13 with a through hole, a coil spring 14, a switch 151, a tuning circuit 15 including a coil 152 wound around the ferrite core 13, and a coil 181 wound around the ferrite core 13. An amplifier circuit 16 and a battery 17 are integrally combined and built-in,
A cap 18 is attached to the rear end to constitute the input vent 1.

FIG. 2 shows details of the tuning circuit 15 and the amplifier circuit 16.

The tuning circuit 15 includes a switch 51, a coil 152, capacitors 153, 154, and a semi-fixed capacitor 155. The semi-fixed capacitors 155 are connected in parallel with each other to form a well-known parallel resonant circuit.
The values of the coil 152 and the capacitors 153 and 155 are set to values such that the phases of the voltage and current resonate (synchronize) in the same phase at a frequency fO of an AC signal, which will be described later.

Further, the capacitor 154 is connected to both ends of the coil 152 and the capacitors 153 and 155 via the switch 151, and when the switch 151 is turned on, the phase of the current in the parallel resonant circuit described above is changed by a predetermined angle, for example, 9
The switch 151 has a capacity to delay 0''.
When the core 12 is pushed into the shaft 11 by pressing the tip of the core 12 against the manual surface of the tablet, the core 12 is pressed by the rear end via the coil spring 14 and turned on.

Further, the amplifier circuit 16 includes a coil 181, a FET 162, a transistor 163, and other capacitors, resistive elements, choke coils, and the like. Said FET
As shown in FIG. 3, the operating point of Lfi2 is set at point a in the class C operating range, and when the tuning circuit 15 receives a radio wave of frequency fO, the tuning circuit 15 receives a signal of a predetermined level or higher. Only when the signal is generated, the signal is passed to the FET 182. It is amplified by a transistor 163, etc., and then connected to a coil 181.
, 152, positive feedback is made to the tuning circuit 15.

FIG. 4 shows the main structure of a coordinate human-powered device using the human-powered Ben 1. In the figure, 2 is a tablet, 3 is a position detection circuit, and these constitute the main body of the device.

FIG. 5 shows details of the tablet 2 and the position detection circuit 3. In the figure, 21 is a position detection section, 22.23 is a selection circuit, and 24.25 is a connection switching circuit, which constitute the tablet 2. In addition, 301 is a processing device, 302 is a waveform shaping circuit, 303 is a phase shifter, 304 is an XY switching circuit, 305 and 308 are drive circuits, 307 and 308 are amplifiers, 309 is a bandpass filter (BPF), 310
, 311 is a phase detector (PSD), 312 , 313
is a low pass filter (LPF), 314.

315 is an analog-to-digital converter (AD converter), which constitutes the position detection circuit 3.

The position detection unit 21 includes a large number of loop coils 2, for example, 48 loop coils 2 arranged in parallel along the X direction as shown in FIG.
1-xi, 21-x2.・・・・・・2l-x48
and a large number, for example, 48 loop coils 21-yl, 21-y2, arranged in parallel along the Y direction.・・・・・・
- 21-74g are superimposed very close to each other (however, they are shown separated in the drawing for ease of understanding). Loop coil 2l-x1 ~ 2l-x4
8 and 21"-yl to zi-74g, each loop coil is arranged parallel to each other and overlapping each other. Note that each loop coil is configured with one turn here, but multiple turns may be used as necessary. The position detection unit 21 may be formed by connecting a large number of parallel conductors formed by etching a well-known printed circuit board with jumper wires, etc., to connect the above-mentioned large number of loop coils. You can use what you have created.

The selection circuit 22 selects the loop coils 21-x, 1 to 21.
The selection circuit 23 sequentially selects the loop coils from -x4g to -x4g, and the selection circuit 23 selects the loop coils 2l-y1
~2l-y48 are selected in sequence, and these operate based on information from the processing device 301.

The connection switching circuit 24 connects the loop coil selected by the selection circuit 22 to the drive circuit 305 and the amplifier 3.
07, and the connection switching circuit 25 alternately connects the loop coils selected by the selection circuit 23 to the drive circuit 306 and the amplifier 308, which will be described later. It operates based on the transmission/reception switching signal.

Next, the operation will be described. First, the manner in which radio waves for position detection are transmitted and received between the position detection section 21 and the input pen 1, and the signals obtained at this time will be described with reference to FIG.

The processing device 301 generates an AC signal with a frequency fO1 of, for example, 500 kHz based on a clock from an oscillator (not shown).
For example, a square wave signal A is generated, and a frequency of 15. [1
Generates a 25kHz transmission/reception switching signal B.

The rectangular wave signal A is sent to a waveform shaping circuit 302, where the waveform is shaped, and further sent to a phase shifter 303. Phase shifter 3
02 creates a signal with the phase of the rectangular wave signal A unchanged (0') and a signal C delayed by 90 degrees, and sends these to phase detectors 310 and 311, respectively.

On the other hand, the rectangular wave signal A is sent via the XY switching circuit 304 to either the drive circuit 305 or 30B, for example, the drive circuit 305, where it is converted into a balanced signal and sent to the connection switching circuit 24. Since the connection switching circuit 24 is switched and controlled by the signal B, the signal output from the connection switching circuit 24 to the selection circuit 22 is 32 μsec.
It is a signal that outputs or does not output a 500kHz pulse signal every time.

The signal is passed through the selection circuit 22 to the - loop coil of the position detection unit 21, for example 2l-xi (i-1, 2, 3, . . .
...48), but at this time, the loop coils 2l-xl generate radio waves based on the signal.

At this time, if the input pen 1 is held in a substantially upright state near the loop coil 2l-xi of the position detection section 21, the radio wave excites the coil 152 of the input pen 1, and the tuned circuit 15 receives the signal. It generates an induced voltage that is synchronized with the current.

Thereafter, as the signal enters a no-signal period, that is, a reception period, the loop coil 21-x1 is connected to the amplifier 30.
When switched to the T side, the radio waves from the loop coil 2l-xi disappear immediately, but the voltage E is amplified by the amplifier circuit 16 and sent to the tuning circuit 15 via the coils 161 and 152.
As a result, an induced voltage E of approximately constant voltage is generated in the tuned circuit 15.

On the other hand, the current flowing through the tuned circuit 15 based on the induced voltage E causes the coil 152 to emit radio waves. Since the radio wave reversely excites the loop coil 2l-xl connected to the amplifier 307, an induced voltage F due to the radio wave from the coil 152 is generated in the loop coil 2l-xi.

Since the connection switching circuit 24 is switched by the transmission/reception switching signal B, it receives the induced voltage F from the loop coil 2l-xi only during the transmission stop period. The induced voltage F
is amplified by an amplifier 307 and sent to a bandpass filter 309 having a passband centered at the frequency fO to remove noise components, and then passed through phase detectors 310 and 31.
1, respectively.

The rectangular wave signal A is input to the phase detector 310 as a detection signal, and at this time, if the phase of the signal F matches the phase of the rectangular wave signal A, the signal F has just been inverted to the positive side. Outputs signal G. The signal G is converted into a flat signal H of voltage VH by a low-pass filter 312 having a sufficiently low cutoff frequency.

Further, the rectangular wave signal C is inputted to the phase detector 311 as a detection signal, and at this time, if the phase of the signal F matches the phase of the rectangular wave signal C, the signal F is shifted to the positive side as described above. The inverted signal I is output. The signal I is converted into a flat signal J of voltage VJ by a low-pass filter 313 similar to the above.

Here, when the switch 151 is off at the input bench 1, the phases of the voltage and current at the resonant frequency of the tuning circuit 15 match, as described above, and the received signal F and the rectangular wave signal A The phases of the two also match. Therefore, at this time, a voltage appears only at the output of the low-pass filter 312, and no voltage appears at the output of the low-pass filter 313.

In addition, when the switch 151 is on in the input Ben 1, the phase of the current at the resonant frequency of the tuned circuit 15 will lag the phase of the voltage by 90'' as described above, and the received signal F will be delayed by 90''. The phase also lags behind the phase of the rectangular wave signal A by 90 @, that is, it matches the phase of the rectangular wave signal C. Therefore, at this time, the low-pass filter 31
A voltage appears only at the output of 3 (note that if the phase delay at this time is less than 90°, the low-pass filter 31
A voltage value corresponding to the phase delay amount appears at both the outputs of 2 and 313. ).

The outputs of the low-pass filters 312 and 313 are A
The data are converted into digital values by D converters 314 and 315, and sent to the processing device 301. The processing device 301 performs arithmetic processing shown in the following equations (L) and (2) on the output values of the AD converters 814 and 315.

Vx-(VP +VQ2)l12-=(L)-1
......(2) V o-wt a n (V Q / VP) Here, VP is the output value of the AD converter 314, and VQ is the A
This is the output value of the D converter 315. Further, the voltage Vx shows a value proportional to the distance between the input bend 1 and the loop coil 2l-xi, and the voltage V shows a value proportional to the phase difference between the voltage and current in the tuning circuit 15 of the input bend 1.

The value of the voltage VX changes when the loop coil 2l-xi is switched and the distance between the loop coil 2l-xi and the input vent 1 changes, and from this, the position of the input vent 1 is detected as described later. Ru.

The voltage V. Since the value of V changes only depending on whether the switch 151 is turned on or off, the voltage V. By comparing the voltage with a predetermined threshold voltage, whether the switch 151 is on or off is identified.

Next, the manner of inputting coordinates in the apparatus of the present invention will be explained according to FIGS. 8 to 10.

First, when the entire device is powered on and enters the measurement start state, the processing device 301 sends an X direction selection signal to the XY switching circuit 304, and further the -x48, information for selecting the first loop coil 2l-xi is sent to the selection circuit 22, and the loop coil 2l-xi is connected to the connection switching circuit 24. The connection switching circuit 24 alternately controls switching of the loop coils 2l-xi to the drive circuit 305 and the amplifier 307 based on the transmission/reception switching signal B described above.

At this time, the drive circuit 305 sends 16 pulse signals of 500 kHz as shown in FIG. ) is connected to the loop coil 2l-
Send to xi. The switching between transmission and reception is shown in FIG. 8(b).
As shown in the figure, the - loop coil is repeated seven times for 2l-xi.

This seven-time transmission and reception repetition period corresponds to the - loop coil selection period (448 μsec).

At the output of the phase detectors 310 and 311, an induced voltage is obtained for the - loop coil every seven reception periods, but this induced voltage is passed through the low-pass filter 312 as described above.
, 313, AD Konnoku Ichiyo 314,
It is converted into a digital value at 315 and sent to the processing device 301. At this time, AD converters 314', 31
The output value of 5 is converted into a detected voltage, for example Vxl, which is proportional to the distance between the input vent 1 and the loop coil 2l-xi, and is temporarily stored.

Next, the processing device 301 sends information for selecting the loop coil 2l-X2 to the selection circuit 22, and
2 is connected to the connection switching circuit 24, a detection voltage Vx2 proportional to the distance between the input vent 1 and the loop coil 2l-x2 is obtained, and this is stored.
~2l-x48 are sequentially connected to the connection switching circuit 24, and the 8th
Detection voltages Vxl to VX48 are proportional to the distance between each loop coil and the human-powered bend 1 as shown in FIG. ).

As shown in FIG. 9, the actual detected voltage is obtained only in several loop coils around the position (xp) where the input vent 1 is placed.

When the voltage value of the stored detection voltage is equal to or higher than a certain detection level, the processing device 301 calculates a coordinate value representing the position of the input vent l in the X direction from these voltage values as will be described later. The data is transferred to a storage unit (not shown).

Next, the processing device 301 sends a selection signal in the Y direction to the XY switching circuit 304, and the AD converter 314 when switching the selection circuit 23 and the connection switching circuit 25 in the same manner as described above.
, 315, each loop coil 2l-yl in the Y direction is obtained by performing the arithmetic processing of equation (1) above on the output value of 315.
The detected voltage proportional to the distance between ~2l-y48 and the manual pen 1 is temporarily stored, a coordinate value representing the position of the input pen 1 in the Y direction is calculated, and this is transferred to the storage section.

When the first position detection is completed in this way, the processing device 301 performs the second and subsequent position detection as shown in FIG.
8 and 2l-yl to 2l-y48, the selection circuits 22 and 23 are provided with information for selecting only a certain number of loop coils, for example, 10, around the loop coil from which the maximum detected voltage was obtained. The output value is obtained in the same manner as described above, and the position relative to the input bench 1 is detected.The obtained coordinate value is transferred to the storage section and the value is updated.

In Fig. 10, the level check refers to whether the maximum value of the detected voltage and several voltage values before and after it have reached the detection level, and which loop coil has the maximum detected voltage. If the detection level has not been reached, the coordinate calculation is stopped, and the center of the loop coil to be selected in the next detection operation is set.

On the other hand, the processing device 301 calculates the detection voltage V proportional to the phase difference between the voltage and current in the tuning circuit 15 of the input vent 1, as well as the detection voltages for the input vent 1, by the calculation process of the equation (2), The detected voltage (2) is constantly compared with a predetermined threshold voltage. Therefore, at this time, when the switch 151 of the input bench 1 is turned on, the processing device 301 detects this from the comparison result and uses the coordinate values in the X and Y directions at this point as the coordinate values of the specified position. The data is sent to an electronic computer, etc.

One calculation method for determining the coordinate value xp is to approximate the waveform near the maximum value of the detected voltages VXI to VX48 by an appropriate function, and then determine the coordinates of the maximum value of the function.

For example, in FIG. 8(C), the maximum detection voltage Vx3
, and the detection voltages VX2 and Vx4 on both sides thereof can be approximated by a quadratic function, it can be calculated as follows (
However, the coordinate values of the center positions of the loop coils 2l-xi to 2l-x48 are assumed to be X1 to x48, and the interval therebetween is assumed to be ΔX. ). First, from each voltage and coordinate value, Vx2-a(x2-xp) 10b -=-(3
)Vx3-a (x3-xp) +b...
...14) Vx4-a (x4-xp) 10b
-----=<5). Here, a and b are constants (a
< O).

Also, x37x2−Δx −−−−・−(
8) x4 - x2 = 2 ΔX
......(7). Expressions (6) and (7) are converted into (
4), Substituting into equation (5) and rearranging, xp-x2+Δx/2 ((3Vx2-4 Vxa
10Vx4) / (Vx2-2 VX3+VX4)
1...(8)

Therefore, from each detection voltage Vxl to Vx48, extract the maximum detection voltage obtained at the time of the level check and the detection voltages before and after the maximum detection voltage, and extract these and the detection voltage of the loop coil from which the maximum detection voltage was obtained. By performing an operation corresponding to the above-mentioned equation (8) from the coordinate values (known) of the previous loop coil, the coordinate values of the designated position of the input ben 1 can be calculated.

In the above embodiment, the coordinate values of the designated position were specified by changing the phase of the radio waves sent from the tuning circuit 15 of the input bench 1 to the position detecting section 21 in accordance with the operation of the switch 151. 1 is provided with a known signal generator, and when the switch 151 is operated, the signal generator generates a signal having a specific pattern, and the signal is transmitted from the input vent 1 using infrared rays, ultrasonic waves, radio waves, etc. This may be detected on the position detection circuit 3 side.

Further, as described above, when specifying the coordinate value of a designated position without using a change in the phase difference in the tuning circuit 15, a tuning circuit with a tuning frequency fO and a phase difference θ° between voltage and current,
Position indicators each having a tuning circuit with a tuning frequency fO and a phase difference of 90'' are prepared, and the processing unit 301 performs the calculation process of equation (8) for each output value of the AD converters 314 and 315. Then, the positions of the two position indicators can be detected simultaneously without changing other configurations.

Further, the number of loop coils and the arrangement thereof in the embodiments are merely examples, and it goes without saying that the present invention is not limited thereto.

- (Effects of the Invention) As explained above, according to the present invention, the radio wave received by the tuning circuit of the position indicator is amplified by the amplifier circuit and positively fed back to the tuning circuit, and the amplified signal is Since radio waves are transmitted from the coil of the tuned circuit based on the antenna, stronger radio waves can be sent to the tablet side than in the conventional case, allowing accurate position detection to be performed at all times without being affected by external interference radio waves. Furthermore, compared to increasing the strength of the radio waves on the tablet side, it has the advantage of reducing the influence of radio waves on the surroundings and requiring less power consumption.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the reflective position indicator of the present invention, Fig. 2 is a diagram showing details of the electric circuit section of the reflective position indicator, and Fig. 3 is a diagram showing the details of the electric circuit section of the reflective position indicator. 4 is a diagram showing the outline of the coordinate input device using the reflective position indicator of the present invention, FIG. 5 is a diagram showing the detailed configuration of the tablet and the position detection circuit, and FIG. 6 is a diagram showing the operation state. The figure is a detailed configuration diagram of the position detection section, Figure 7 is a waveform diagram of each part in Figure 5, Figure 8 (a) (b) (c) is a timing diagram showing the basic detection operation, and Figure 9 10 is a diagram showing detection voltages obtained from each loop coil during the first detection operation, and FIG. 10 is a timing diagram showing the second and subsequent detection operations. DESCRIPTION OF SYMBOLS 1... Input pen, 2... Tablet, 3... Position detection circuit, 15... Tuning circuit, 16... Amplification circuit.

Claims (1)

[Claims] A tuning circuit including a coil and a capacitor and having a predetermined tuning frequency is provided, and the tuning circuit receives radio waves transmitted from the tablet side, and at this time, based on the signal generated in the tuning circuit. A reflective position indicator that generates radio waves from the coil and sends them back to the tablet side is characterized by being provided with an amplification circuit that amplifies the signal generated in the tuned circuit and positively feeds it back to the tuned circuit. Reflective position indicator.