JPH04109324A - Position detector - Google Patents

Abstract

PURPOSE:To supply a large current and to improve the SN ratio of a detection signal by selectively connecting one of optional loop coils in a sense part to an AC current supplying means and a guide voltage detecting means. CONSTITUTION:A selection circuit 2 consists of 1st and 2nd switching circuits 2-1, 2-2 capable of supplying a large current, and selects one of conductors in accordance with selection information inputted from a control part 6 to constitute a transmitting loop coil. On the other hand, a selection circuit 3 consists of multiplexers 3-1, 3-2 having high input impedance and selects one of conductors in accordance with selection information inputted from the control part 6 to constitute a receiving loop coil. The control part 6 is constituted of a microprocessor or the like, generates an AC signal of frequency fo, supplies the AC signal to a current driver 4, controls the circuits 2, 3 to switch the loop coils in the sense part 1, and finds out the coordinate position of an indicating position indicated by a position indicator 7.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a position detection device for detecting a position indicated by a position indicator.

(Prior Art) Prior to filing this application, the applicant filed Japanese Patent Application No. 61-213970.
No. 63-70326 (hereinafter referred to as the prior application), radio waves are sent and received between a position indicator and a sensing section to detect the position indicated by the position indicator. A position detection device was proposed.

The content of this prior application will be briefly explained. First, an alternating current of a predetermined frequency is supplied to the loop coil of the sensing section to transmit radio waves, and the radio waves are received by a tuning circuit provided in the position indicator. At this time, the loop coil of the sensing section receives the radio waves transmitted from the tuned circuit that received the radio waves, and generates an induced voltage in the loop coil. This is sequentially switched and repeated for a plurality of loop coils, and the position indicated by the position indicator is detected based on the induced voltage generated in each loop coil.

(Problem to be Solved by the Invention) However, in the above device, an analog switch is used to switch each loop coil because the circuit that supplies alternating current to all the loop coils and the circuit that detects the induced voltage are switched and connected. Since the current value that can be supplied to the loop coil is limited, the loop coil was made into a two-turn configuration to strengthen the transmitted radio waves and improve the S/N ratio, but the configuration of the sensing section became complicated and the However, there was a problem of rising costs.

They also proposed a method in which a transmitting loop coil and a receiving loop coil were provided separately, and the transmitting loop coil was driven by a circuit capable of supplying a large current. No. 32807), but in this case as well, there was a problem that the configuration of the sense section was complicated and the cost increased by 2.

Furthermore, in the above device, due to the difference in the relative distance between the position indicator and each loop coil, the strength of the radio waves reaching the tuned circuit differs each time each loop coil is selected, and induction occurs in the tuned circuit. Since the voltage values of the voltages also differ, when extracting power from the tuned circuit to drive other electronic circuits, the extracted power also changes depending on the magnitude of the induced voltage, and as a result, the amount of power emitted from the tuned circuit changes. There is a problem in that this changes the distribution of the strength of the radio waves caused by the position detecting device, which adversely affects the relationship between the induced voltage detected by the position detecting device and the position of the position indicator, that is, the position detection accuracy.

In view of the above-mentioned conventional problems, the present invention simplifies the configuration of the sensing section without reducing the S/N ratio, and also allows the extraction of power from the tuning circuit of the position indicator without affecting the position detection accuracy. The purpose of the present invention is to provide a position detection device that makes it possible.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a sensing section having a plurality of loop coils, an alternating current supply means for supplying alternating current to the loop coils, An induced voltage detection means for detecting an induced voltage generated in the loop coil is provided, and the indicated position of the position indicator is determined by transmitting and receiving radio waves between the loop coil of the sensing section and a tuned circuit provided in the position indicator. In a position detection device that seeks the following, the first selection means selectively connects any loop coil of the sense section to the alternating current supply means, and the first selection means selectively connects any loop coil of the sense section to the induced voltage detection means. A position detection device comprising a second selection means, and a position detection device comprising a plurality of mutually parallel conductors having one end connected in common, and a loop coil formed by any two of the conductors. a first selection means for selectively connecting any two of the other ends of the conductor of the sense part to the alternating current supply means; a second selectively connecting any two of them to the induced voltage detection means;
The position detection device according to claim (1), further comprising a first loop coil selectively connecting only a part of the loop coil of the sensing section to the alternating current supply means.
The position detection device according to claim (1) or (2), further comprising a selection means for selecting a plurality of induced voltage detection means and a plurality of arbitrary loop coils of the sensing section. The present invention proposes a position detection device according to any one of claims (1) to (3), further comprising a second selection means selectively connected to the induced voltage detection means of the invention.

(Function) According to claim (1) of the present invention, the loop coil of the sensing section is connected to the alternating current supply means via the first selection means, and the alternating current supply means is connected to the loop coil of the sensing section via the second selection means. Since the voltage detection means is connected, an alternating current with a large current value can be supplied to the loop coil of the sensing section from the alternating current supply means.

Further, according to claim (2), since the loop coil is constituted by two conductors whose other ends are connected to the alternating current supply means or the induced voltage detection means by the first or second selection means, the sensing section The number of conductors in the loop coil can be reduced, and the distance between the centers of the loop coils can be set arbitrarily.

Furthermore, according to claim (3), alternating current is supplied to only some of the loop coils of the sensing section and radio waves are transmitted, thereby eliminating differences in the strength of radio waves reaching the tuned circuit. It becomes less.

Moreover, according to claim (4), induced voltages in a plurality of loop coils can be detected simultaneously, and the time required for position detection can be shortened.

(Embodiment) FIG. 1 shows a first embodiment of the position detection device of the present invention, in which 1 is a sensing section, 2 is a first selection circuit, 3 is a second selection circuit, 4 is a current driver, 5 is a voltage amplifier,
6 is a control unit, and 7 is a position indicator.

The sensing section 1 includes a large number of conductors 1-1, 1-2, 61 in this case, which are arranged in parallel with each other at a predetermined interval in the direction of arrow A (hereinafter referred to as the position detection direction).・・・・・・
1-61 are connected in common.

The selection circuit 2 includes first and second switch circuits 2-1 and 2-2 that can supply a large current.

The switch circuit 2-1 includes the conductors 1-1.1-9, .
The other end of the conductor 1-57 is connected to the switch circuit 2-2, and the conductor 1-5.1-13° is connected to the switch circuit 2-2.
・The other end of 1-61 is connected, and each control unit 6
The - conductor is selected in accordance with selection information input manually, thereby configuring a loop coil for transmission. Further, the output of a current driver 4 that amplifies and supplies an AC signal of a predetermined frequency fo output from the control section 6 is connected to the switch circuits 2-1 and 2-2.

The selection circuit 3 consists of high-impedance multiplexers 3-1 and 3-2. The multiplexer 3
-1 is the conductor 1-1.1-3゜1-5.・・・・・・
- The other end of the conductor 1-57.1-59.1-61 is connected to the multiplexer 3-2.
1-4. . . . The other ends of 1-58° and 1-60 are connected, and the - conductor is connected to - according to the selection information input from the control unit 6, respectively.

A loop coil for reception is constructed by selecting one of the following. In addition, multiplexers 31 and 3-2
A voltage amplifier 5 that amplifies the induced voltage generated in the loop coil and outputs the amplified voltage to the control section 6 is connected to.

The control unit 6 is composed of a well-known microprocessor, etc.
An alternating current signal with the frequency fo is generated and supplied to the current driver 4, and as described later, the selection circuits 2 and 3 are controlled to switch the loop coil of the sensing section 1, and the output voltage of the voltage amplifier 5 is changed to an analog signal. The coordinate values of the position indicated by the position indicator 7 are determined by digital conversion and predetermined arithmetic processing.

The position indicator 7 includes a built-in tuning circuit 8 that includes a coil and a capacitor, and whose tuning frequency is the frequency fo.

Next, the operation of the device will be explained.

First, the control section 6 connects the selection circuit 2 to a negative loop coil for transmission, for example, as shown in FIG.
and 1-21, and connects the current driver 4 to the loop coil to supply alternating current of frequency fo to transmit radio waves. At this time, when the position indicator 7 is placed on the sensing section 1, for example at point A, the radio wave excites the tuned circuit 8, causing it to generate an induced voltage of frequency fo.

Next, the control unit 6 continues sending out the selection information to the selection circuit 2 for a certain period of time, then stops it and stops transmitting radio waves, and also causes the selection circuit 3 to use a negative loop coil for reception, e.g. As shown in Figure 3 (a), the sense section 1
information for selecting a loop coil consisting of conductors 1-12 and ]-15, and connects the voltage amplifier 5 to the loop coil. At this time, the induced voltage generated in the tuning circuit 8 of the position indicator 7 gradually attenuates in accordance with its loss and emits a radio wave with a frequency f○, but this radio wave passes through the above-mentioned negative loop coil for reception. Excite and generate induced voltage. The induced voltage is amplified by a voltage amplifier 5 and then sent to a controller 6.
will be sent to.

Next, the control unit 6 causes the selection circuit 3 to continue sending out the selection information for a certain period of time, then stops this and stops receiving radio waves, and also causes the selection circuit 2 to transmit the selection information as shown in FIG. It sends out information to select the - loop coil and causes it to transmit radio waves again.

Further, the control section 6 causes the selection information to be transmitted, that is, the transmission of radio waves, after continuing for a certain period of time as described above, and then stops this, and also causes the selection circuit 3 to use another loop coil for reception, for example, as shown in FIG. As shown in b), the conductor 1-1 of the sense part 1
3 and 1-16, and the voltage amplifier 5 is connected to the loop coil to receive radio waves.

Hereinafter, the transmission of radio waves by the negative loop coil for transmission, and the other loop coil for reception, that is, FIG. 3 (C
) The conductors 1-14 and 1-17 of the sense section 1 as shown in
and conductors 1-15 and 1- as shown in FIG. 3(d).
The reception of radio waves by the loop coil consisting of 18 loop coils is repeated.

FIG. 4 shows an example of the alternating current outputted from the current driver 4 when transmitting the aforementioned radio waves and the induced voltage outputted from the voltage amplifier 5 when receiving the radio waves. In the figure, Va, V
b, Vc, and Vd are the aforementioned conductors 1-12 and 1, respectively.
-15.1-13 and 1-16.1-14 and 1-17
．． This is the induced voltage when selecting the receiving loop coil consisting of 1-15 and 1-18.

After this, the control section 6 sends information for selecting another loop coil for transmission, for example, a loop coil consisting of conductors 1-13 and 1-25 of the sense section 1, and the corresponding loop coils for reception, that is, conductors. 1-16 and 1-19.1-1
7 and 1-20. Information for selecting the loop coils consisting of 1-18 and 1-21. Repeat.

The control unit 6 transmits and receives the radio waves using each loop coil (
However, in the vicinity of both ends in the position detection direction, both the transmitting and receiving loop coils are composed of conductors having different intervals from those described above. ), the voltage value of the obtained induced voltage is converted into a digital value, and the indicated position of the position indicator 7 is determined by performing predetermined arithmetic processing on these values. Note that the specific content of the calculation process is the same as that of the previous application mentioned above, so it will not be described in detail.

The transmission and reception of radio waves and the calculation of the indicated position described above are repeated at regular intervals, and the obtained information on the indicated position of the position indicator 7 is transferred to a host computer or the like (not shown).

In this way, according to the embodiment, a large current can be caused to flow through the loop coil of the sensing section 1 by the selection circuit 2,
In addition to being able to strengthen the transmitted radio waves, the selection circuit 3
As a result, the induced voltage of the loop coil of the sensing section 1 can be detected with high input impedance.
The N ratio can be improved. In addition, the sense section 1 has 6
Since it has a comb-teeth shape in which one end of one parallel conductor is connected in common, it can be formed on only one side of the board, which reduces costs, and allows forming a loop coil with arbitrary conductors. Here, out of all the conductors of the sense section 1, only every fourth conductor is connected to the selection circuit 2 to form a loop coil for transmission, and
Since four receiving loop coils are combined with one transmitting loop coil, it is possible to reduce the number of switch circuits that constitute the selection circuit 2, thereby reducing costs and positioning. Changes in the strength of radio waves reaching the tuning circuit 8 of the device 7 can be reduced.

In addition, although the above-mentioned embodiment performs position detection in one direction, the same sense section as above is arranged so that its conductors are orthogonal to each other, and the same selection circuit, current driver, and voltage amplifier as above are provided, By alternately detecting the positions, the indicated positions in two orthogonal directions can also be detected.

Furthermore, in the embodiment described above, by changing the information sent to the selection circuit 3, the combination of conductors constituting the receiving loop coil can be changed. That is, for example, as shown in FIG. 5(a), a loop coil of the receiver 11 consisting of conductors 1-9 and 114 is constructed, and then, as shown in FIG. It is also possible to configure a receiving loop coil consisting of -19. In this case, the distance between the centers of the loop coil increases, so the position detection accuracy deteriorates, but it is necessary to scan the entire sensing section 1. It takes less time. Therefore, at the start of position detection, the width of the receiving loop coil is widened in this way to scan the entire sensing section 1, and the rough position of the position indicator 7 is quickly detected. The width of the position indicator 7 may be set as described above, and scanning may be performed only near the area where the position indicator 7 of the sensing unit 1 is located, thereby detecting the detailed indicated position.

FIG. 6 shows a second embodiment of the present invention, in which four receiving loop coils are configured at the same time to detect induced voltages respectively. That is, in the figure,
3' is a selection circuit, 5-1°5-2.5-3.5-4 is a voltage amplifier, and each voltage amplifier 5-1 to 5-4 is connected to the sense section 1 through a selection circuit 3 Every fourth conductor is connected.

In the above configuration, when transmitting radio waves, for example, as shown in FIG.
), the selection circuit 2 selects conductor 1- of the sense section 1.
13 and 1-21 is connected to the current driver 4 to transmit radio waves, and when receiving radio waves, for example, as shown in FIG. 6(b), the selection circuit 3' selects the conductor 1- A loop coil consisting of conductors 1-13 and 1-17, a loop coil consisting of conductors 1-13 and 1-17, and a conductor 1-
Loop coil consisting of 14 and 1-18, conductor 1-15
and 1-19 are respectively connected to voltage amplifiers 5-1.5-2.5-3.5-4 to receive radio waves, that is, to detect induced voltage.

The alternating current output from the current driver 4 when transmitting the radio waves and the voltage amplifiers 5-1 to 5-4 when receiving the radio waves.
FIG. 7 shows an example of the induced voltages output from each of the two. In the figure, Va', Vb'Vc' and Vd' are respectively the conductors 1-12 and 1-16.
1-13 and 1-17.1-14 and 1-18.1-1
This is the induced voltage generated in the loop coil consisting of loop coils 5-1 and 1-19 and output from voltage amplifiers 5-1 to 5-4.

According to this embodiment, since the induced voltages generated in the four loop coils can be obtained simultaneously, the time required for position detection can be shortened simply by increasing the reading speed of each induced voltage in the control section 6. .

In the first and second embodiments, the positions of the transmitting loop coils with respect to the receiving loop coils are almost the same, and the resonance state in the tuning circuit of the position indicator is kept almost constant. Therefore, even if a rectifier circuit is connected to the tuned circuit and power is extracted to operate other electronic circuits installed in the position indicator, the distribution of the strength of the emitted radio waves, that is, the accuracy of position detection, will be affected. There isn't.

In addition, in the first and second embodiments, the frequency and phase of the tuned circuit are changed in accordance with changes in the operating state of the position indicator, and this is detected by the position detection device, thereby controlling the operation of the position indicator. It is also possible to identify the state.

(Effect of the invention) As explained below, according to claim (1) of the present invention,
A sensing section having a plurality of loop coils, an alternating current supply means for supplying an alternating current to the loop coils, and an induced voltage detection means for detecting an induced voltage generated in the loop coils, and the sensing section has a loop coil and a position indicating means. In a position detection device that determines the indicated position of the position indicator by transmitting and receiving radio waves to and from a tuned circuit provided in the sensor, a loop coil of the sensing section is selectively connected to an alternating current supply means. Since the present invention includes the first selection means and the second selection means for selectively connecting any loop coil of the sense section to the induced voltage detection means, it is possible to supply an alternating current with a large current value to the loop coil of the sense section. This makes it possible to strengthen the transmitted radio wave and improve the S/N ratio of the detection signal, and also allows the loop coil in the sense section to have a one-turn configuration, which reduces costs accordingly. I can do it.

Further, according to claim (2) of the present invention, a sensing portion is made up of a large number of mutually parallel conductors whose one ends are commonly connected, and a loop coil is formed by any two of the conductors; first selection means for selectively connecting any two of the other ends of the conductor of the sense section to alternating current supply means;
Since the second selection means selectively connects any two of the other ends of the conductors of the sense section to the induced voltage detection means, the number of conductors in the sense section can be reduced and the board Since it can be formed from only one side, the cost can be reduced accordingly, and the loop coil can be constructed from arbitrary conductors, and the distance between the centers of the loop coil can be set arbitrarily.

Further, according to claim (3) of the present invention, since the first selection means for selectively connecting only a part of the loop coils of the sensing section to the alternating current supply means is provided, the tuning circuit of the position indicator Differences in the strength of the arriving radio waves, that is, changes in the voltage value of the induced voltage generated in the tuned circuit, can be reduced, and therefore, power can be extracted from the tuned circuit without affecting position detection accuracy. It is also possible to reduce the number of switch circuits capable of supplying large currents constituting the first selection means, and the cost can be reduced accordingly.

Further, according to claim (4) of the present invention, a plurality of induced voltage detection means and a second selection means for selectively connecting a plurality of arbitrary loop coils of the sensing section to the plurality of induced voltage detection means. This has the advantage of being able to shorten the time required for position detection.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of the position detection device of the present invention, FIG. 2 is an explanatory diagram showing an example of a transmission state in the device of FIG. 1, and FIGS. 3(a) to (d) is a main part explanatory diagram showing a second embodiment of the explanation showing an example of the reception state in the device of FIG. 1, and FIG. 7 is a waveform diagram showing an example of alternating current and induced voltage in the device of FIG. 6. . 1...Sense part, 1-1 to 1-61...Conductor, 2゜3.3''...Selection circuit, 2-1.2-2...Switch circuit, 3-1.3- 2...Multiplexer, 4...
- Current driver, 5.5-1 to 5-4... Voltage amplifier, 6... Control section, 7... Position indicator, 8... Tuning circuit.

Claims (4)

[Claims] (1) A sense section having a plurality of loop coils, an alternating current supply means for supplying alternating current to the loop coils, and an induced voltage detection means for detecting an induced voltage generated in the loop coils, and the loop coils of the sense section In a position detection device that determines the indicated position of a position indicator by transmitting and receiving radio waves between the position indicator and a tuned circuit provided in the position indicator, an arbitrary loop coil of the sensing section is selectively used as an alternating current supply means. a first selecting means for connecting, and a second selecting means for selectively connecting an arbitrary loop coil of the sensing section to the induced voltage detecting means.
A position detection device comprising: selection means. (2) A sense section consisting of a large number of mutually parallel conductors whose one ends are commonly connected, and a loop coil is formed by any two of the conductors; and the other end of the conductor of the sense section. a first selection means for selectively connecting any two of the conductors to the alternating current supply means; and a second selection means for selectively connecting any two of the other ends of the conductors of the sense section to the induced voltage detection means. 2. The position detection device according to claim 1, further comprising: selection means. (3) The position detection device according to claim (1) or (2), further comprising a first selection means for selectively connecting only a part of the loop coil of the sense section to the alternating current supply means. . (4) A claim characterized by comprising a plurality of induced voltage detection means and a second selection means for selectively connecting any plurality of loop coils of the sensing section to the plurality of induced voltage detection means. The position detection device according to any one of (1) to (3).