JPH0628093A - Cordless digitizer - Google Patents

Abstract

PURPOSE:To dispense with an independent oscillator and to simplify the constitution of a device by constituting a self-oscillation system by a coil provided on a position indicator together with, a resonating circuit and an amplifier arranged on a table on a tablet. CONSTITUTION:At the time of measuring the indicating position of the position indicator 1, the self-oscillation system is constituted of two loop coils X, Y connected to the amplifiers 23, 24 among plural coils X1 to Xn, Y1 to Yn on the tablet 20 and the coil 11 of the indicator 1. The indicating position of the indicator 1 on the tablet 20 is determined by fetching the output of the amplifiers 23, 24 in the self-oscillation system into a processor 25 of the device and by processing them. When a switch 13 of the indicator 1 is operated, the frequency of a signal oscillated from the self-oscillation system formed is changed to a frequency which depends upon the capacity of a capacitor 12 of the indicator 1 and the ON/OFF state of the switch 13 in the indicator 1 can detected by detecting the changed frequency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digitizer for detecting position coordinates and the like of a position indicator mounted on a tablet, and more specifically, a position indicator for indicating a position is provided on a tablet body. It relates to so-called cordless digitizers that do not connect.

[0002]

2. Description of the Related Art In a conventional cordless digitizer of this type, for example, in the case of an electromagnetic induction type cordless digitizer, a transmission coil group arranged in the X direction on the tablet side and a Y direction orthogonal to the transmission coil group are arranged. In the case where the receiving coil group and the oscillator for applying a current signal of a constant frequency to the transmitting coil group are provided, the current signal from the oscillator is sequentially applied to the transmitting coil group, and the position indicator is placed on the tablet. In addition, the position of the position indicator is detected by detecting an induced voltage generated on the side of the receiving coil group by electromagnetic coupling with the transmitting coil group. That is, when the position indicator is placed on the tablet, the transmitting coil to which the current is supplied and the position indicator are electromagnetically coupled to each other, whereby an induced voltage is generated in the receiving coil group.
The generated induced voltage is detected by sequentially scanning the receiving coil group, and the position coordinate of the position indicator on the tablet is determined from the X direction position of the transmitting coil to which the current is supplied and the Y direction position of the receiving coil that generated the induced voltage. Configured to detect. In addition, an oscillator is provided in the position indicator, a current signal of a constant frequency is applied to the coil in the position indicator to generate a magnetic field,
In some cases, the coordinate position or the like of the position indicator is detected from the induced voltage generated in the receiving coil group on the tablet side.

[0003]

However, in the case of detecting the coordinate position of the position indicator by the electromagnetic induction method as described above, there is a method of generating a magnetic field by the position indicator or a method of generating a magnetic field from the tablet. In either case, there is a drawback in that the oscillator has an oscillator for generating a magnetic field, and the configuration of the device becomes complicated accordingly. The present invention has been made to solve the above drawbacks, and in particular, in exchanging signals between the tablet and the position indicator, an independent oscillator is not required, that is, the entire measurement system has one oscillator configuration. The purpose is to provide a cordless digitizer.

[0004]

In order to solve the above problems, in the cordless digitizer of the present invention, the position indicator has a coil, a capacitor, and a switch for connecting or insulating the coil and the capacitor. A plurality of loop coils which are configured to form a resonance electric circuit by operation and are mutually insulated on the tablet, and a changeover switch which connects two loop coils of the plurality of loop coils through an amplifier. And a capacitor having a predetermined capacitance value is connected to at least one of the loop coils connected to the amplifier, and when measuring the position indicated by the position indicator, a plurality of loop coils of the tablet are connected. Self-oscillation by two loop coils connected to the amplifier and the coil of the position indicator The output of the amplifier of the self-oscillation system is taken into the processing device of the device and processed to determine the pointing position on the tablet of the pointing device, and the switch of the pointing device is operated. In this case, the frequency of the signal transmitted from the formed self-oscillation system changes to a frequency that depends on the capacitance of the capacitor of the position indicator, and the switch of the position indicator is detected by detecting this changed frequency. Configured to detect the condition.

[0005]

In the cordless digitizer configured as described above, the self-oscillation system is configured by the coil provided in the position indicator, the resonance circuit including the loop coil and the capacitor disposed on the tablet, and the amplifier.
The pointing position of the pointing device is detected based on the output of the amplifier. When the switch of the position indicator is operated, a resonance system electric circuit is formed in the position indicator, and the frequency of the output signal transmitted by the self-oscillation system depends on the capacitance of the capacitor of the position indicator. Then, the state of the position indicator is detected by detecting the frequency of this output signal.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A cordless digitizer of the present invention will be described below with reference to the drawings. 1 to 6 show the configuration of a cordless digitizer according to the present invention, FIG. 1 is an explanatory diagram showing the configuration of the entire digitizer, and FIG. 2 shows the scanning operation of each loop coil group shown in FIG. Explanatory diagram, FIG. 3 is an explanatory diagram showing an example of the position detecting method of the digitizer shown in FIG. 1, FIG. 4 is an explanatory diagram showing the principle of a self-oscillation system formed by the cordless digitizer of the present invention, and FIG. FIG. 6 is an explanatory view showing an embodiment of the position indicator used in the cordless digitizer of the invention, and FIG. 6 is a flowchart showing the operation of the cordless digitizer of the invention.

First, the configuration and operation of the digitizer according to the present invention will be described with reference to the drawings. In Figure 1 (a)
Shows the structure of the position indicator 1, and (b) shows the structure of the tablet. In FIG. 1A, the position indicator 1 includes a coil 11, a variable capacitor 12, and a switch 1.
3, and a ferrite 14 made of a magnetic material. When the switch 13 is closed, the position indicator 1 forms a non-resonant electric circuit including the coil 11, and when the switch 13 is opened, the position indicator 1 is a resonance circuit including the coil 11 and the capacitor 12. Configured to form a system electrical circuit. FIG. 5 is a specific example of the position indicator 1, which is a so-called pen-type position indicator, and 14 is a rod-shaped magnetic body that is provided in the central portion of the coil 11 and is formed of a cylindrical ferrite.
Reference numeral 15 is a core body provided in the central portion of the magnetic body, and 11 is a variable capacitor that changes its capacitance according to the movement of the core body 14 via a spring. In this position indicator, when the core body is grounded on the tablet surface, the switch 13 is opened to connect the coil 11 and the variable capacitor 12, and according to the pressing force of the core body 15 against the tablet, It is configured such that the capacitance of the variable capacitor 12 changes.

In FIG. 1 (b), the tablet 20 has X-side loop coil groups X1, X2, X3, ... Formed on a grit plate and insulated from each other in the X direction and sequentially arranged.
., Xn and the Y-side loop coil group Y1, Y2, Y3, ..., which are formed on a grid plate different from the X-side loop coil group and which are sequentially insulated from each other in the Y direction.
Yn and are provided. Further, capacitors C1, C2, C3, ..., Cn each having a predetermined capacitance value are connected to the X-side loop coil group, and one terminal of each loop coil has an X-axis scanner. 21, the other terminal is connected to the ground. Further, one terminal of each loop coil of the Y-side loop coil group is connected to the Y-axis scanner 22, and the other terminal is connected to the ground. Here, the input side of the voltage amplifier 23 is connected to the output from the X-axis scanner 21, and further the amplifier 2
The output of 3 is connected to the input side of the Y-axis scanner 22. A current amplifier 24 is connected to the input side of the Y-axis scanner 22. In this device, when the position indicator 1 is mounted on the loop coils connected to the two amplifiers 23 and 24, respectively, the amplifier, the Y-side loop coil, the position indicator, the X-side loop coil, and the capacitor are connected. A self-oscillation system is formed.

That is, as shown in FIG. 4, two coils from each loop coil group provided on the tablet 20 are connected by an amplifier, and the coil and the coil of the position indicator constitute a self-oscillation system. Then, when the position indicator is brought close to the tablet, the coil of the position indicator is excited by noise from the amplifier or changeover switch, etc., and this triggers each of the above-mentioned components to continue as if they constitute an oscillator. And it oscillates stably. In this case, the output level of the amplifier changes depending on the position of the position indicator and the distance between the loop coil, and therefore the position of the position indicator can be determined by comparing the output levels when the loop coils are connected. Can be detected.

Further, FIG. 4A shows a self-oscillation system formed when the capacitor 12 and the coil 11 are insulated by the switch 13 of the position indicator, and FIG. 4B shows the switch of the position indicator. 1 shows a self-oscillation system in which a capacitor 12 and a coil 11 are connected by 13, that is, a resonance system electric circuit is formed in the position indicator 1. The signal oscillated by the self-oscillation system in FIG. 4A has a frequency dependent on the capacitance of the capacitor Cn connected in parallel to the loop coil Xn, and the switch 13 of the position indicator is operated to operate the coil. When the capacitor 12 is connected to 11, that is, the frequency of the signal transmitted by the self-oscillation system in FIG. 4B becomes a frequency depending on the capacity of the connected capacitor 12. The capacitance of the capacitor 12 of the position indicator and the capacitance of the capacitor Cn connected to the loop coil are such that the frequency components of the signals output by the above two self-oscillation systems are clearly different,
Set in advance.

In the cordless digitizer of the present invention,
When detecting the pointing position of the position pointing device 1, first, the processing device 25 outputs the Y side loop coil Y to the output side of the current amplifier 24.
The Y-axis scanner 22 is controlled so that 1 is connected. With the Y-side loop coil Y1 connected, the processor 25 controls the X-axis scanner 21 so that the input side of the voltage amplifier 23 receives the X-axis.
The side loop coil is sequentially X1-X at a predetermined measurement timing.
Switch and connect up to n. At the same time, the processing device 25 fetches and stores the output of the voltage amplifier 23 at each measurement timing. After detecting the output of the X-side loop coil Xn, the processing device 25 controls the Y-axis scanner 22 to connect the Y-side loop coil Y2 to the output side of the current amplifier 24, and similarly set the X-side loop coil to a predetermined value. Switching from X1 to Xn in sequence at the measurement timing, voltage amplifier 2
3 output is detected. These operations are repeated up to the Y side loop coil Yn. As a result of the above position detection operation, the voltage amplifier 23 obtains an output result as shown in FIG. The graph of FIG. 3 shows the level of the output signal at each measurement timing, and the vertical axis shows the voltage level of the measured output. Based on the obtained data, the address signals of the X-side loop coil and the Y-side loop coil when the maximum voltage level is generated are detected, and the area where the position indicator is placed (the loop coils are formed to overlap each other). Area). (Outline position determination operation)

Next, the two loop coils determined in the above-mentioned rough position determination operation and the adjacent loop coils (three X-side and three Y-side, totaling six loop coils) are selected, and the X-axis, The Y-axis scanner is sequentially switched to detect the output of each voltage amplifier 23. By comparing and computing the data obtained here,
The position of the center of the coil of the position indicator 1 is determined in which part of the area specified by the rough position determination operation. (Precision position determination operation)

Further, in the cordless digitizer of the present invention, when detecting the switch state of the position indicator, the processing unit 25 connects the X-axis and Y-axis loop coils specified by the rough position determining operation to the amplifiers, respectively. X
Controls the Y-axis and Y-axis scanners. At this time, the current amplifier 2
The signal output from 4 is taken in and its frequency component is measured. When detecting the on / off state of the switch 13 of the position indicator, it suffices to detect whether the frequency component of the output signal depends on the capacitor Cn connected to the loop coil or the capacitor 12 of the position indicator. This can be detected in a short time and with a simple device. Further, when detecting the capacitance change of the variable capacitor 12 of the position indicator, particularly when the pressing force of the position indicator 1 is continuously and accurately detected, the measurement time of the output signal is set to be long and within this measurement time. It is possible to detect the number of changes of the output signal in the above by comparing with the high frequency reference signal.

Further, in the cordless digitizer of the present invention, the processing device 25 repeats each of the above-mentioned rough position determining operation, fine position determining operation, and switch state detecting operation in the procedure shown in the flowchart of FIG. Control. In step 1, the processing device 25 detects the approximate position of the position indicator 1 by the above-described operation, moves to step 2, detects the precise position of the position indicator 1, and moves to step 3. In step 3, it is detected whether or not the voltage level of the signal detected in the precision position detection operation has reached a predetermined amount. At this time, if the voltage level of the detected signal is less than or equal to the predetermined amount, the processing device 25 determines that the position indicator 1 has moved to the outside of the area specified by the rough position determination operation, returns to step 1, Position indicator 1
The rough position determination operation is performed. If it is determined in step 3 that the position indicator 1 exists in the area, the process proceeds to step 4.

In step 4, it is detected whether the frequency component of the detected signal depends on the capacitor Cn connected to the loop coil of the tablet or the capacitor 12 of the position pointing device, and thereby the position pointing is performed. The on / off state of the switch 13 of the container is detected. When it is detected that the frequency component of the detected signal depends on the capacitor Cn connected to the loop coil of the tablet, that is, when the switch is turned on, the process returns to step 2 and the precision position detecting operation is performed. When the frequency component of the detected signal depends on the capacitor 13 of the position indicator, that is, when the switch is off, the process proceeds to step 5, the output component is precisely detected, and the precision position of step 2 is detected. Return to detection operation.

[0016]

As described in detail above, according to the present invention, when the pointing position of the pointing device is detected, the electric circuit of the pointing device, the amplifier of the tablet, and the two loops connected to the amplifier. Since the self-oscillation system is formed by the coil and the pointing position of the position pointing device is detected based on the output of the amplifier, the oscillator for driving the loop coil can be omitted, which simplifies the device configuration. At the same time, since the self-oscillation system is formed and operates only when the position indicator is brought close to the tablet,
Power consumption can be suppressed, and when detecting the switch state of the position indicator, it is performed by detecting the frequency component of the signal generated from the self-oscillation system, and at the same time, the tablet and position indicator respectively. Since the on / off state of the switch can be clarified by providing the capacitor, the on / off state of the switch of the position indicator can be identified in a short time by a simple device that does not require precision, and at the same time, it can be comparatively performed. When the time-consuming switch state detection is not necessary (when the switch is not operated), this operation can be omitted, and the pointing position of the position pointing device can be quickly detected.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a cordless digitizer according to the present invention.

FIG. 2 is an explanatory diagram showing a scan operation of the digitizer shown in FIG.

FIG. 3 is a schematic diagram showing an example of a position determining method of the digitizer shown in FIG.

FIG. 4 is a diagram showing a principle of detecting a position and the like of a position indicator according to the present invention.

FIG. 5 is an explanatory diagram showing an embodiment of a position indicator according to the present invention.

FIG. 6 is a flowchart showing the operation of the digitizer of the present invention. .

[Explanation of symbols]

 1 Position Indicator 11 Coil 12 Variable Capacitor 13 Switch 14 Ferrite 15 Core 20 Tablet 21 X-Axis Scanner 22 Y-Axis Scanner 23 Voltage Amplifier 24 Current Amplifier 25 Processing Device

Claims (1)

[Claims] 1. A first coil group arranged in a first direction, and a first coil group arranged in a second direction orthogonal to the first direction,
And a second coil group in which capacitors are connected in parallel for each unit coil pattern, the first coil group and the second coil group.
Position indicator including a tablet that selectively connects two unit coil patterns from the coil group of 1 through an amplifier, at least a coil, and a switch that enables or disables the load to the coil. In a cordless digitizer having a device, when the position indicator is brought close to the tablet, the position indicator, the first coil pattern, the amplifier, and the second coil pattern form a self-oscillation system, and the self-oscillation system. The output signal of the self-oscillation system when the pointing position on the tablet of the position pointing device is detected based on the signal output by and the coil and load of the position pointing device are enabled by the operation of the switch. By detecting the change in
A cordless digitizer characterized by being configured to detect a switch operating state of the position indicator.