JPH05313808A - Cordless digitizer - Google Patents

Abstract

PURPOSE:To detect the position and the writing pressure of an input pen with a comparatively simple operation by detecting the change of frequency of a self-oscillation system caused by the change of inductance of the coil of a position pointer and then detecting the writing pressure of the input pen. CONSTITUTION:The 1st and 2nd ferrite cores 251 and 252 are attached at the upper part of a pen point 26 via an elastic substance 253. The core 251 moves back and forth in response to the pressure of an input pen applied to a tablet. Then, inductance of a coil 21 can be continuously changed in accordance with the vertical movement of the core 251. A capacitor 22 is connected to the coil 21. The position pointed by a position pointer on the tablet is detected by means of the output signal of an amplifier obtained while a self-oscillation system is working. At the same time, the change of frequency of the self-oscillation system caused by the change of inductance of the coil of the position pointer is detected. Thus, the writing pressure of the input pen is detected.

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, so that the device is complicated by that amount. To eliminate this drawback,
The present inventor has 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 has been made to improve this point, and an object of the present invention 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, in the present invention, a plurality of conductors arranged on the tablet are connected by an amplifier, and a coil arranged on an input pen as a position indicator is placed close to the tablet. At this time, the plurality of conductors of the tablet, the amplifier, and the coil of the input pen constitute a self-oscillation system having a unique frequency characteristic, and the magnetic core divided into two is interposed in the coil of the input pen and The magnetic core is arranged so that the relative distance to the other magnetic core is variable according to the writing pressure of the input pen, and the inductance of the coil is continuously changed according to the pressure (writing pressure) of the input pen on the tablet. It is configured to be variable and uses the output signal of the amplifier when the self-oscillation system is in the oscillating state to indicate on the tablet of the position indicator. Configured to detect the pen pressure of the input pen by detecting this frequency change of the self-oscillating system based on change in inductance of the position indicator coils of the output signal and detects the location.

[0007]

Since the frequency of the output signal from the amplifier of the digitizer which constitutes the self-oscillation system is simply measured, the writing pressure of the input pen can be detected by a simple operation.

[0008]

1 to 6 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 a cordless digitizer using this input pen, FIG. 3 is an explanatory diagram showing an example of a frequency detection method, and FIG. 4 is an explanatory diagram showing the overall configuration of this cordless digitizer. 5 is an explanatory view showing a scanning operation of each loop coil group shown in FIG.
FIG. 6 is an explanatory diagram showing an example of the 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 frequency detection 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 has a pen-shaped housing and is configured as a so-called input pen in this embodiment, and includes the coil 21, the first capacitor 221, the second capacitor 222, and the switch 23. There is. The coil 21 of the position indicator 2 is attached so that its inductance is continuously variable, for example, according to the contact pressure of the position indicator 2 on the tablet 1. The second capacitor 222 is connected in parallel to the position indicator 2 via the switch 23 and is used to identify the on / off operation of the switch 23.
When the position indicator is positioned on the tablet configured as described above, the coil 21 of the position indicator 2 picks up ambient noise radio waves and the like, and the oscillation operation is started in this system.

As shown in FIG. 5, 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. 6 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. 5, 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. 6).
), 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. 6), 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 pointing position of the position pointing device 2 on the tablet 1. ..

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 an electrical configuration similar to that of the position indicator described above. The housing 20 has a pen shape. A first ferrite core 251 and a second ferrite core 252 are attached to an upper portion of the pen tip 26 in a form in which an elastic body 253 is sandwiched between them. These two ferrite cores 2
The second ferrite core 252 of 51 and 252 is fixed to the housing 20. Therefore, the first ferrite core 251 has a structure that moves forward and backward according to the pressure (writing pressure) of the input pen 2 on the tablet. The coil 21 is provided around these two ferrite cores 251 and 252. The inductance of the coil 21 can be continuously changed as the vertical position of the first ferrite core 251 changes. This coil 21
A capacitor 22 is connected to. In this embodiment, the positional relationship of each element in the initial state of the input pen 2 (the state where the writing pressure is not applied) is as follows. That is, the length in the vertical direction of the elastic body 253 connecting between the first ferrite core (movable ferrite core) 251 and the second ferrite core (fixed ferrite core) 252 is 1 (el), and the vertical direction of the coil 21. When the length in the direction is m and the lengths of the lower end of the first ferrite core 251 and the upper end of the second ferrite core 252 are k, the midpoint position of l and the midpoint position of m match. It is arranged.
Now, assuming that the input pen 2 is in a state of no writing pressure as shown in FIG. 2, a relatively large leakage magnetic flux is generated between the two ferrite cores 251 and 252. This leakage magnetic flux affects the coil 21. When pen pressure is applied to the input pen 2, l
Since the distance is shortened, the leakage magnetic flux is reduced accordingly, and the influence on the coil 21 is reduced. In this way, since the influence of the leakage magnetic flux directly acts on the coil 21, it is possible to obtain a large inductance change of the coil 21 with a small displacement of l.

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. Since the inductance of the coil 21 of the input pen 2 is increased by increasing the writing pressure,
The output frequency decreases continuously. FIG. 3 is an explanatory diagram for detecting the frequency of the output signal of the amplifier 13 or 14 shown in FIG. As shown in FIG. 3, in this device, the number of rising edges of the output signal e0 or ed within a fixed time T is detected. Time base circuit 15 for generating a fixed time
The rise detection circuit 152 operates in response to the start signal of 1 to detect, for example, the rise portion of the output signal ed. The number of times of this rising is the rising counter 153
Is counted and sent to the utilization circuit 15 to detect the frequency.

The data taken in by the utilization circuit 15 also changes the capacitance of the capacitor by operating the switch 23 of the input pen 2. Therefore, also in this point, the utilization circuit 15 detects the operation state of the input pen 2 by measuring the frequency component of the output data. As described above, in this device, the contact pressure of the input pen 2 with respect to the tablet 1 or the on / off discrimination of the switch thereof can be identified. Further, as described above, by arranging such frequency analysis based on the output signal of the current amplifier 14, there is an advantage that a sufficiently large output signal can be used for frequency analysis and a signal for position determination. Since the signal is different from the above, 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.

Although the above-mentioned device belongs to the electromagnetic coupling type, it can also be applied to a so-called electrostatic coupling type digitizer. In this case, the loop coil as described above may be used as an electrode for electrostatic coupling, or a conductor may be simply used.

[0017]

As described above, according to the present invention,
The coil of the input pen is configured to continuously change its inductance according to the writing pressure, and the signal supplied to one conductor of the self-oscillation system is amplified by the current amplifier. Obtainable. Therefore, the pen pressure and the operation state 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 an explanatory diagram showing an example of frequency detection.

FIG. 4 is a block diagram showing an overall configuration of a digitizer showing one embodiment of the present invention.

5 is an explanatory diagram showing a scan operation of the digitizer in FIG. 1. FIG.

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

[Explanation of symbols]

 1: Tablet 2: Position indicator

Claims (1)

[Claims] 1. A plurality of conductors, an amplifier and an input of the tablet, when a plurality of conductors arranged on the tablet are connected by an amplifier and a coil arranged on an input pen as a position indicator is brought close to the tablet. A pen coil constitutes a self-oscillation system having a unique frequency characteristic, and a magnetic core divided into two is interposed in the input pen coil, and one of the magnetic cores depends on the pen pressure of the input pen. Is arranged such that the relative distance to the other magnetic core is variable, and the inductance of the coil is continuously variable according to the pressure (writing pressure) of the input pen against the tablet. The pointing signal on the tablet of the pointing device is detected using the output signal of the amplifier when in the oscillating state, and the position finger of the output signal is detected. By detecting this frequency change of the self-oscillating systems based on a change of the inductance of the vessels of the coil cordless digitizer configured to detect pen pressure of the input pen.