JPH05341902A - Cordless digitizer - Google Patents

Abstract

PURPOSE:To detect not only the position but also the stylus pressure of an input pen with a relatively simple constitution by continuously varying the relative distance between two resonance circuit systems in the input pen in accordance with the stylus pressure. CONSTITUTION:A ferrite core 23 is attached on a penpoint 24. This ferrite core 23 is attached through a spring 25 and is vertically movably held. A first coil 211 constituting a first resonance circuit is fixed to the lower part of the ferrite core 23. A second coil 221 constituting a second resonance circuit system attached to a housing 2 is attached above the first coil 211. Consequently, the distance between the coil 211 of the first resonance circuit system and the coil 221 of the second resonance circuit system is changed in accordance with the stylus pressure at the time of bringing the penpoint 24 into contact with the tablet surface. This change changes the resonance frequency of the whole of two resonance circuit systems, and therefore, the frequency of this output signal is measured to detect the stylus pressure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digitizer for reading designated position coordinates on a surface, and more particularly to a so-called cordless digitizer in which a position pointing device for pointing a position to be read is not connected to a tablet body.

[0002]

2. Description of the Related Art A conventional cordless digitizer of this type is
Both systems had an oscillator that operated independently. For example, in an electromagnetic induction type cordless digitizer, magnetic field coupling between the position indicator and the tablet is used. Therefore, even when the position indicator generates a magnetic field, or the tablet generates a magnetic field. In both cases, the system had an oscillator for generating a magnetic field.

[0003]

Therefore, in such a device, it is necessary to provide an oscillator, and there is a drawback that the device becomes complicated accordingly. To eliminate this drawback,
The present applicant proposed a self-oscillation type cordless digitizer in the "cordless digitizer" filed on February 21, 1992. In this device, at least two of, for example, a loop coil group provided on a tablet are connected by an amplifier, and a self-oscillation system is configured with a position indicator having either or both of a coil and a capacitor. .. When the position indicator is brought close to the tablet, the coil of the position indicator is excited by ambient noise radio waves, etc., and this triggers continuous and stable oscillation as if each of the above elements constitutes an oscillator. To do. The output level of the amplifier in this oscillation is
Since the position changes according to the distance between the position indicated by the position indicator and the loop coil, it is possible to detect the indicated position. Further, the oscillation frequency at this time has a value specific to this self-oscillation system. Therefore, the operation state of the position indicator can also be detected by changing the constant of the coil or the capacitor of the position indicator according to the operation state of the position indicator.

By the way, in such a digitizer, there is a digitizer in which a pen type is used as a position indicator so that various kinds of data can be input with a feeling similar to a writing feeling. It is desirable that such a device be capable of drawing thick and thick when writing with a strong force and drawing thin and thin when a force is weak, similar to drawing a character on paper. For this reason, in the conventional device of this type, the pen pressure information of the input pen is configured to be input together with the input of the position data by some means.

In the digitizer disclosed in Japanese Examined Patent Publication No. 3-68408, the antenna coil provided on the tablet plate intermittently emits a radio wave, and the radio wave is received by the LC tuning circuit of the input pen and the antenna coil does not operate. In the state, the electric wave is returned in reverse, and the pen pressure of the input pen is detected by examining the property of the electric wave. Specifically, the inductance or the capacitance of the coil or the capacitor of the LC tuning circuit of the input pen is continuously variable according to the pen pressure of the input pen, and the change in the phase of the returned radio wave is detected. Then, the writing pressure is detected. As described above, this device is an excellent method capable of detecting the pen pressure of the input pen with high accuracy. However, an antenna coil is provided on the tablet, and the antenna coil intermittently generates radio waves and There is a drawback that a complicated operation of receiving a so-called reflected radio wave from the input pen and checking its phase during operation is required. The present invention is made to improve this point, and an object thereof is to provide a cordless digitizer capable of detecting the position of the input pen and the writing pressure with a relatively simple operation.

[0006]

Therefore, according to the present invention, a plurality of conductors arranged on the tablet are connected by an amplifier, and a plurality of resonance circuit systems are arranged on an input pen as a position indicator. When the pen is brought close to the tablet, the plurality of conductors of the tablet, the amplifier, and the resonance circuit system of the input pen form a self-oscillation system having an inherent frequency characteristic, and at least one resonance circuit system of the input pen. Is configured so that its position is changed according to the pressure (writing pressure) of the input pen on the tablet, and the resonance frequencies of the plurality of resonance circuit systems are changed according to the writing pressure.
A means for identifying the frequency of a signal induced in the conductor or another conductor of the tablet when the self-oscillation system is in an oscillating state is provided, and the writing pressure of the input pen is detected by detecting the frequency change of the self-oscillation system. Is configured to detect.

[0007]

Since the frequency of the output signal from, for example, the amplifier of the digitizer constituting the self-oscillation system may be measured, the writing pressure of the input pen can be detected with a simple structure.

[0008]

1 to 5 show the structure of an electromagnetic induction type cordless digitizer according to the present invention. FIG. 1 is an explanatory view showing the structure of the main part of an input pen used in this digitizer. Is a graph showing the relationship between the output frequency and the writing pressure of the cordless digitizer using this input pen, FIG. 3 is an explanatory diagram showing the overall configuration of this cordless digitizer, and FIG. 4 is a diagram of each loop coil group shown in FIG. FIG. 5 is an explanatory diagram showing a scanning operation, and FIG. 5 is an explanatory diagram showing an example of a position detecting method of the digitizer shown in FIG.

First, the structure and operation of the digitizer according to the present invention will be described with reference to FIGS. Please refer to FIG. On the tablet 1, Xs sequentially arranged in the X direction
The side loop coil groups X1, X2, X3, ... And the Y side loop coil groups Y1, Y2, Y3, which are sequentially arranged in the Y direction,
... is provided. The X-side loop coil group is connected to the X-axis scanner 11, and the Y-side loop coil group is connected to the Y-axis scanner 12. X-axis scanner 11
Is connected to the input side of the voltage amplifier 13 by selecting one of the X-side loop coils at each timing of measurement based on the X-address signal from the control circuit (not shown). One of the Y-side loop coils is selected below at each measurement timing and connected to the output side of the current amplifier 14. The output signal of the voltage amplifier 13 becomes the input signal of the current amplifier 14. Therefore,
In this device, the selected loop coil of the X side loop coil group, the voltage amplifier 13, the current amplifier 14 and the Y
The selected loop coil of the side loop coil group is connected at any measurement timing. Then, the output e0 of the voltage amplifier 13 is taken into the utilization circuit 15 and is used for the position determination of the position indicator 2, and the output e0 of the current amplifier 14 is used.
The d is also subjected to a predetermined process and taken into the utilization circuit 15 to be used for switch identification or for detecting the height (writing pressure) of the position indicator.

In this device, the above-mentioned voltage amplifier 13 is selected to be in a non-saturation region in this self-oscillation system, and the current amplifier 14 is used in a saturation region or saturates in a short time. Is desirable. Since the output e0 of the voltage amplifier 13 is used for position determination, it is desirable to use the output e0 of the current amplifier 14 in the non-saturation region in order to improve the reproducibility of the position, and the output ed of the current amplifier 14 is one loop coil of the self-oscillation system. This is because it becomes an output that drives the system, and a fast rise is desired for stable oscillation of the system. On the other hand, the position indicator 2 in this embodiment has a pen-shaped housing, is configured as a so-called input pen, and has a first resonance circuit system 21 and a second resonance circuit system 22. The first resonance circuit system 21 includes a first coil 211 and a first capacitor 212, and the second resonance circuit system 22 includes a second coil 221 and a second coil 221.
Of the capacitor 222. The second resonance circuit system 22 of the position indicator 2 is attached so that its position is continuously variable according to the contact pressure of the position indicator 2 on the tablet 1. When the position indicator is positioned on the tablet configured as described above, the coil 21 of the position indicator 2 starts oscillating operation in this system due to ambient noise or radio waves or the shock of switching between the scanners 11 and 12. To do.

As shown in FIG. 4, in this device,
The Y-axis scanner 12 sequentially connects each Y-side loop coil to the output side of the amplifier 13 at a predetermined timing. When the Y-axis scanner 21 selects any Y-side loop coil, the X-axis scanner 11 operates to sequentially connect each X-side loop coil to the input side of the amplifier 13. Here, one timing when the X-axis scanner 11 selects each X-side loop coil is one measurement timing.

Then, at each measurement timing, the utilization circuit 15 fetches the output e0 of the voltage amplifier 13 and performs the processing shown in FIG. FIG. 5 shows a utilization circuit 15
3 is a schematic diagram showing one method for determining the pointing position of the position pointing device 2 on the tablet 1, which is one of the processes of FIG. As shown in FIG. 4, each output level of the amplifier 13 when the Y-axis scanner 12 selects the loop coil Y1 and the X-axis scanner 11 selects each X-side loop coil (see FIG. 5).
), The Y-axis scanner 12 selects the loop coil Y2,
Each output level of the voltage amplifier 13 when the X-axis scanner 11 selects each X-side loop coil (FIG. 5), the Y-axis scanner 12 selects the loop coil Y3, and the X-axis scanner 1
1. Voltage amplifier 1 when 1 selects each X side loop coil
3, the output level of the voltage amplifier 13 at each measurement timing is used as data, and the utilization circuit 15 determines the position indicated by the position indicator 2 on the tablet 1. ..

Next, a specific method of detecting the pen pressure of the input pen in this cordless digitizer will be described with reference to FIGS. FIG. 1 is an explanatory diagram of a specific configuration of the input pen 2 having the same electrical configuration as the above-described position indicator. The ferrite core 23 is attached to the upper portion of the pen tip 24. The ferrite core 23 is attached via a spring (elastic member) 25 and is held so as to be vertically movable. Below the ferrite core 23, the first coil 21 constituting the first resonance circuit system 21 is formed.
1 is fixed. A second coil 221 constituting the second resonance circuit system 22 attached to the housing 20 is attached above the first coil 211. Therefore, depending on the magnitude of the writing pressure when the pen core 24 comes into contact with the tablet surface, the coil 2 of the first resonance circuit system 21
The distance between 11 and the coil 221 of the second resonance circuit system 22 changes. This change changes the overall resonant frequency of these two resonant circuits.

FIG. 2 shows the relationship between the writing pressure of the input pen 2 and the frequency of the output signal of the amplifier 13 or 14 shown in FIG. By continuously increasing the writing pressure, the distance between the two resonance circuit systems of the input pen 2 becomes smaller, and the coupling between these resonance circuits becomes stronger. Therefore, the frequency of the signal output thereby changes continuously. As a method of detecting the frequency of the output signal of the amplifier 13 or 14, a method of detecting the number of rising edges of the output signal e0 or ed within the fixed time T can be used. It is also possible to measure, for example, one cycle time of the measured waveform and obtain the frequency of the measured waveform based on this. For example, in the former method, a time base circuit that generates a fixed time and a rising edge detection circuit that detects the rising edge of the waveform to be measured are provided, and the rising edge detection circuit is activated by the start signal of the time base circuit, Output signal ed (or e0)
The rising edge of is detected. The number of rises is counted by using a rise counter and the count result is sent to the utilization circuit 15. The utilization circuit 15 can detect the frequency by performing a predetermined process based on the counting result.

A capacitor is added to one of the resonance circuit systems of the input pen 2 depending on the operating state of the switch, and the same structure as above is adopted so that the frequency change of the output data due to the addition of the capacitor can be measured. As a result, the switch operating state of the input pen 2 can also be detected. Further, as described above, by constructing such frequency analysis based on the output signal ed of the current amplifier 14, there is an advantage that a sufficiently large output signal can be used for frequency analysis, and it is possible to determine the position. Since the signal is different from the signal, the operation state of the input pen 2 can be detected independently of the position determination, and there is an advantage that the circuit configuration is simplified.

In the above apparatus, the conductor constituting the self-oscillation system is also used as the position determining grid conductor, but the position determining grid conductor and the oscillation conductor may be provided independently.

[0017]

As described above, according to the present invention,
The two resonant circuit systems inside the input pen are configured so that their relative distances are continuously variable according to the writing pressure, and the signal supplied to one conductor of the self-oscillation system is amplified by a current amplifier. Therefore, a high level output signal can be obtained. Therefore, the pen pressure of the input pen can be detected together with the position detection with a relatively simple configuration.

[Brief description of drawings]

FIG. 1 is a structural explanatory view showing an input pen of a digitizer showing one embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a relationship between a writing pressure of an input pen and a frequency of an output signal.

FIG. 3 is a block diagram showing an overall configuration of a digitizer showing one embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a scanning operation of the digitizer shown in FIG.

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

[Explanation of symbols]

 1: Tablet 2: Position indicator

Claims (1)

[Claims] 1. A plurality of conductors arranged on a tablet are amplified.
Connected to each other, and multiple input pens as position indicators
The resonance circuit system is arranged, and the input pen is the tablet described above.
The multiple conductors of the tablet, the amplifier when brought into close proximity to
And the resonance circuit system of the input pen has a unique frequency characteristic.
A self-oscillation system, wherein at least one resonance circuit system of the input pen is
Position according to the pressure (writing pressure) on the tablet
Is changed and the resonance frequency of the above multiple resonance circuit systems is
It is configured to vary according to the above, and when the self-oscillation system is in the oscillation state,
Identify the frequency of a signal induced in a conductor or another conductor
Means for detecting the frequency change of the self-oscillation system,
A cordless digitizer configured to detect pen pressure.