JPH0772968A - Coordinate reader - Google Patents

Abstract

PURPOSE:To simplify the manufacturing process, and to detect the inclination of a coordinate indicator by simplifying a circuit, and besides, eliminating necessity for adjusting the coordinate indicator in a wireless coordinate reader. CONSTITUTION:The coordinate indicator 8 is provided with a resonance circuit. A first sense line group S1 and a second sense line group S2 are installed so as not to cause direct electromagnetic coupling with each other. A first and a second scanning circuits 1, 2 select successively the sense line groups S1, S2. When the coordinate indicator 8 approaches the sense line groups S1, S2, a positive feedback loop circuit is constituted of these and an amplifier circuit 4 and a position inversion circuit 3, and an oscillation signal 101 is generated. Since the amplitude of an input signal 102 which is the oscillation signal 101 coupled with the second sense line group S2 through the resonance circuit has the indicated position information of the coordinate indicator 8, a coordinate detection circuit 5 inputs this, and calculates the indicated position. Besides, the inclination is detected by executing antiphase detection by the position inversion circuit 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coordinate reading device for inputting coordinate information to an electronic device such as a computer, and more particularly to a wireless coordinate reading device applying an electromagnetic induction phenomenon.

[0002]

2. Description of the Related Art As a conventional coordinate reading device, there is JP-A-04-7720 invented by the present applicant. This coordinate reading device excites a sense line with an excitation signal generated from an excitation circuit, resonates a resonance circuit provided in the position indicator with a magnetic field generated from the sense line, and causes a magnetic field generated from the resonance circuit to occur on another sense line. The position information is obtained from the amplitude of the detected signal by detecting and amplifying the detected signal.

Further, as means for detecting the setting state of the state setting means such as a switch provided in the position indicator on the main body side,
The resonance frequency of the resonance circuit provided in the position indicator is slightly changed by the state setting means, and the setting state is detected by detecting the phase difference between the reference excitation signal and the detection signal from the sense line on the position input device body side. Has been realized.

A number of switches are mounted on the position indicator,
When a large number of status settings are required or the status indication needs to be expanded by providing a pen pressure detection function, a slight phase change on the main body side can be detected accurately and stably. Is equipped with a detection circuit that can be used to ensure detection accuracy, and the resonance frequency of the resonance circuit is accurately adjusted during manufacturing of the position indicator, and even after adjustment, changes in the ambient environment such as temperature changes and changes over time. It was realized by using parts with good stability so that high stability could be obtained.

[0005]

However, in the conventional coordinate reading apparatus of such a system, it is necessary to constantly generate an alternating magnetic field of a predetermined frequency from the exciting sense line, so that a dedicated exciting circuit is required. Was needed. Further, since the resonance frequency of the resonance circuit of the coordinate indicator needs to be adjusted to the vicinity of the frequency of the AC magnetic field generated by the exciting circuit, it is necessary to adjust the coordinate indicator by providing a trimmer capacitor, which reduces the manufacturing cost. It was one of the factors that raised it. Also, maintaining a stable resonant frequency for a long period of time has been a difficult task. As described above, the conventional coordinate reading device has problems to be solved in terms of circuit scale, manufacturing cost, product stability, and the like.

The present invention has been made to solve the above problems, and its first object is not to rely on the conventional method of exciting a resonant circuit with a reference signal such as an exciting signal and detecting its response. The purpose of the present invention is to provide a coordinate reading device in which the excitation circuit is eliminated and the circuit is simplified.

A second object of the present invention is to provide a coordinate reading device which can be stably used for a long period of time while the coordinate indicator is not adjusted to reduce the manufacturing cost. A third object is to provide a coordinate reading device capable of detecting the tilt angle of the coordinate indicator.

[0008]

In order to solve the above problems, according to the present invention, there is provided a first phase inverter circuit, an amplifier circuit, and a first sense line which is parallel to one of the XY orthogonal coordinate axes. A sense line group, a first scanning circuit for sequentially selecting the first sense line group, a second sense line group parallel to the other axis and including a plurality of sense lines, and the second sense line A second scanning circuit for sequentially selecting a group, a coordinate detection circuit, and a coordinate indicator having a resonance circuit. The coordinate detection circuit includes first and second coordinate circuits.
Scanning the scanning circuit to select the first and second sense lines, and the resonant circuit electromagnetically couples with both the first and second sense lines to thereby provide the phase inversion circuit, the amplifier circuit, the first and second sense lines. The coordinate reading device is configured to calculate the coordinate information of the coordinate indicator from the amplitude information of the oscillation generated by the oscillation circuit when the oscillation circuit is formed by the positive feedback loop together with the two sense lines.

[0009]

In the coordinate reader according to the present invention, the resonance circuit is magnetically coupled to both the first sense line selected by the first scanning circuit and the second sense line selected by the second scanning circuit. As a result, a positive feedback loop having a series of paths including the phase inversion circuit, the amplification circuit, the first sense line, the resonance circuit, and the second sense line is formed, and oscillation occurs at the resonance frequency of the resonance circuit. Oscillation by the positive feedback loop is excited by noise, natural noise, etc. generated by the circuit that constitutes this loop.

When the coordinate indicator tilts, the magnetic field distribution of the anti-phase component generated from the resonance circuit of the coordinate indicator changes greatly. At this time, the phase is inverted by the phase inversion circuit, and this inverse Oscillation due to the phase component becomes possible. Since the amplitude information of this oscillation changes according to the feedback amount determined by the distance between the first and second sense lines and the resonance circuit,
The coordinate detection circuit can input this amplitude information to obtain the coordinate information of the coordinate indicator.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a first embodiment of the present invention will be described with reference to FIGS.
It will be explained based on. FIG. 1 is a configuration diagram of this embodiment. In the figure, S1 is a first line having sense lines y1 to yn
Is a sense line group. Each sense line is a coil having a rectangular shape, the long sides of which are parallel to the X axis of the XY orthogonal coordinate axes and are laid at equal intervals in the Y axis direction. Reference numeral 1 is a first scanning circuit for sequentially selecting the first sense line group S1. S2 is sense lines x1 to x
It is a second sense line group having m. These have the same shape as the first sense line group S1 and are laid orthogonal to them. A second scanning circuit 2 sequentially selects the second sense line group S2. Reference numeral 3 is a phase inverting circuit, the input of which is connected to the second scanning circuit 2 and the output of which is connected to the amplifier circuit 4. Phase inversion circuit 3
The phase characteristic is controlled by the control signal 104, and outputs a signal 103 that is substantially in-phase or anti-phase with the input signal 102. Reference numeral 4 is an amplifier circuit for obtaining an oscillation signal 101 having a predetermined amplitude, and its output is connected to the first scanning circuit 1. Reference numeral 5 is a coordinate detection circuit, which selects the first and second scanning circuits 1 and 2 and also receives the input signal 1 from the second scanning circuit 2.
02 is input and the coordinate value is calculated based on this. The coordinate detection device main body is configured by the above circuits.

On the other hand, 8 is a coordinate indicator, which has a resonance circuit (not shown) including a coil. In this embodiment,
A parallel resonant circuit in which a coil and a capacitor were connected in parallel was used. This is used to indicate the coordinate reading position on the main body of the coordinate detecting device. FIG. 2 shows a configuration diagram of the first scanning circuit 1. The first scanning circuit 1 includes a plurality of electronic switches 211 to 21n such as analog switches and a decoder 20.
1 and is configured to close one circuit of the switch by the selection signal 105 output from the coordinate detection circuit 5 and connect one sense line of the first sense line group S1 to the output of the amplifier circuit 4. ing. Although details of the second scanning circuit 2 are not shown, they have the same configuration as the first scanning circuit 1 and are different in that they are connected to the input of the phase inverting circuit 3.

FIG. 3 shows a block diagram of the phase inversion circuit 3.
30 is an analog switch, 31 is an operational amplifier, 32 to 3
Reference numeral 5 is a resistance element. The phase inverting circuit 3 is a known circuit and switches the input signal 102 by the control signal 104 to operate the operational amplifier 31 as an inverting or non-inverting amplifier.

FIG. 4 shows a configuration diagram of the coordinate detection circuit 5.
50 is an amplifier circuit, 51 is a rectifier circuit, 52 is a smoothing circuit, 5
Reference numeral 3 is an A / D conversion circuit, and 54 is a control circuit composed of a general CPU circuit. The input signal 102 guided from the second scanning circuit 2 is detected by these circuits, converted into an envelope signal, and the magnitude thereof is converted into a digital signal and input to the control circuit 54. The control circuit 54 calculates the coordinates based on this signal.

The operation of this embodiment will be described below. 5 to 6 show a waveform diagram of the oscillation signal and an explanatory diagram for calculating coordinates. The first scanning circuit 1 is the coordinate detection circuit 5
First, the sense line y1 of the first sense line group S1 is selected by the selection signal 105 output from the above. That is, in FIG. 2, the decoder 201 turns on the analog switch 211 by the selection signal 105 and connects the output of the amplifier circuit 4 to the first sense line y1. On the other hand, the second scanning circuit 2 sets the second sense line group S2 to x1, by the selection signal 106 output from the coordinate detecting circuit 5 during this period.
x2 ... xm are sequentially selected.

When the scanning of the second sense line group has been completed, the first scanning circuit 1 then selects the sense line y2 of the first sense line group S1, and the second scanning circuit 2 Similarly to the previous time, set the second sense line group S2 to x1, x2.
... sequentially select xm.

This scanning is repeated in the same manner, and finally, the first scanning circuit 1 selects the sense line yn of the first sense line group S1, and the second scanning circuit 2 receives the second sense line group in the meantime. S2 is sequentially selected as x1, x2 ... xm. The coordinate detection circuit 5 uses the input signal 10 obtained by sequentially selecting each sense line as described above.
2 is amplified and waveform-shaped by the amplifier circuit 50, the rectifier circuit 51, and the smoothing circuit 52 shown in FIG. 4, and the magnitude (amplitude) is sequentially digitized by the A / D converter circuit 53, and further sequentially by the control circuit 54. To process.

Next, the input signal 102 generated in this case
Details of the size will be described with reference to FIG. Figure 5
1 is a waveform diagram when the coordinate indicator 8 is located at the portion A of FIG. 1, and shows selection signals 105 and 106 input to the first scanning circuit 1 and the second scanning circuit 2 and the coordinate detection circuit 5. Oscillation signal before AD conversion (signal 151 in FIG. 4)
Indicates.

Symbol a is an oscillation signal immediately below the section A, that is, when the first sense line y4 and the second sense line x4 are selected, and is the largest signal generated during scanning. This is the first sense line y4 and the second sense line y4.
This is because the sense line x4 and the sense line x4 are both the closest to the coordinate indicator 8 and thus have the largest degree of coupling with the resonance circuit, and thus the largest feedback amount.

B and c are on the left and right of the section A, that is, when the first sense line y4 and the second sense line x3 are selected, and the first sense line y4 and the second sense line x5 are selected. Is the oscillation signal. In this case, the resonance circuit of the coordinate indicator 8 and the first sense line y4
However, the magnitudes of the oscillation signal d and the oscillation signal e are smaller than that of the oscillation signal a because the second sense lines are separated from each other.

Further, d and e are above and below the section A, that is, when the first sense line y3 and the second sense line x4 are selected, and the first sense line y5 and the second sense line x4 are selected. This is the oscillation signal when In this case, the degree of coupling between the resonance circuit of the coordinate indicator 8 and the second sense line x4 is the same, but the magnitudes of the oscillation signal b and the oscillation signal c are large due to the distance of the first sense line. It becomes smaller than the oscillation signal a.

Although the oscillation signals a to e have been described above, the position of the sense line selected from the first sense line group S1 and the second sense line group S2 and the coordinate indicator 8 for other signals as well. The size is determined by the positional relationship of. Since the first sense line group S1 and the second sense line group S2 are orthogonal to each other, there is basically no coupling between the first sense line group S1 and the second sense line group S2. In the absence of the coordinate indicator 8, oscillation does not occur. Therefore, as described above, the magnitude of the oscillation signal changes depending on the positional relationship between the position of the sense line selected from the first sense line group S1 and the second sense line group S2 and the coordinate indicator 8.

Next, paying attention to the above five oscillation signals a to e,
A method of calculating coordinates will be described. First, a method of calculating the X coordinate will be described focusing on the oscillation signals a, b, and c.
FIG. 6 (1) is an enlarged view of the periphery of the portion A shown in FIG. 1. Based on this figure, the coordinate indicator 8 moves from the center L0 of the sense line x4 to the sense line x on the center of the sense line y4.
Consider the case of moving to the intermediate L1 between 4 and the sense line x5. 6 (2) and 6 (3) show the oscillation signals a, b, and c when the coordinate indicator 8 is located at L0 and L1.

First, the case where the coordinate indicator 8 is located at L0 will be described. As described above, the oscillation signal a is applied to the sense line x4 while selecting the sense line y4.
The oscillation signal b is a signal when the sense line x3 is selected and the oscillation signal c is a signal when the sense line x5 is selected. At this time, the oscillation signal a has the largest value, and the oscillation signals b and c are equal because the distance between the coordinate indicator 8 and the sense line x3 and the distance between the coordinate indicator 8 and the sense line x5 are the same.

Next, the case where the coordinate indicator 8 is located at L1 will be described. At this time, the oscillation signals a and c are equal because the distance between the coordinate indicator 8 and the sense line x4 and the distance between the coordinate indicator 8 and the sense line x5 are the same. Here, the method proposed by the present applicant (Japanese Patent Laid-Open No. 55-96411).
No.) can be applied to calculate the coordinates. That is, the calculation defined by the following equation is performed based on the oscillation signal.

Q = (V _p −V _{p + 1} ) / (V _p −V _p-1 ) Formula-1 where V _{p + 1} > V _{p-1 In the} above formula, the oscillation signal a is oscillated to Vp. Signal b is Vp-1
Substitute the oscillation signal c into Vp + 1 and set the coordinate indicator 8 to L0.
FIG. 6 (4) shows the change in Q shown in Expression-1 when moving from Q1 to L1. Q = 1 when the coordinate indicator 8 is at the position L0, and Q when the coordinate indicator 8 is at the position L1.
It is clear from the above description that = 0. Also,
When the coordinate indicator 8 is located between L0 and L1, Q takes a value in the range of 0 <Q <1 corresponding to this position on a one-to-one basis. Therefore, the characteristic of this Q is experimentally obtained in advance to calculate Q from the oscillation signals a, b, and c, and the detailed position of the coordinate indicator 8 between L0 and L1 on the sense line is calculated from this Q. Can be asked. Further, the X coordinate can be obtained from this Q and the position of the sense line where the oscillation signal a is detected. Details of this coordinate calculation method are described in JP-A-55-96411.

The Y coordinate can be considered in the same manner as the X coordinate described above. In FIG. 6A, consider a case where the coordinate indicator 8 moves on the center of the sense line x4 from the center L0 of the sense line y4 to the middle L2 of the sense lines y4 and y5. 6 (5) and (6)
Shows the oscillation signals a, d, and e when the coordinate indicator 8 is located at L0 and L2.

First, the case where the coordinate indicator 8 is located at L0 is as described in the method of calculating the X coordinate. When the coordinate indicator 8 is located at L2, the oscillation signals a and e are equal at this time because the distance between the coordinate indicator 8 and the sense line y4 and the distance between the coordinate indicator 8 and the sense line y5 are the same.

Therefore, the characteristic of Q when the coordinate indicator 8 is moved from L0 to L2 as in the case of the above-mentioned X coordinate is as shown in FIG. 6 (7). Similar to the case of the X coordinate, the Y coordinate can be obtained by using the characteristic of Q. Note that the above processing is performed by the control circuit 54 (shown in FIG. 4) configured by a general CPU circuit.

Next, a method of detecting the tilt angle will be described. FIG. 7 shows the distribution of the magnetic field generated from the coordinate indicator 8, and the up and down directions respectively indicate the magnitudes of the magnetic fields of the positive phase / negative phase components. When the coordinate indicator 8 is vertical, the magnetic field distribution is symmetrical as shown in Fig. 7 (1),
When the coordinate indicator 8 is tilted to the right as shown in FIG. 7 (2), the left and right distributions of the anti-phase component shown by the diagonal lines change greatly. Therefore, it is possible to detect the magnitude of this anti-phase component and detect the inclination of the coordinate indicator 8. In the above description, the coordinates are calculated by detecting the magnetic field of the positive phase component in FIG.

Here, paying attention to the phase condition of the oscillation in the positive feedback loop, for example, when the phase inverting circuit 3 performs the non-inverting amplification operation by the control signal 104 and the oscillation of the signal of the positive phase component is performed, Oscillation does not occur in the antiphase component of the magnetic field because the phases differ by 180 degrees. Therefore, when the phase inverting circuit 3 is made to perform the inverting amplification operation by the control signal 104, this time, the phase is rotated by 180 degrees in the phase inverting circuit 3, so that oscillation occurs in the anti-phase component and the magnitude of the anti-phase component is coordinated. This can be detected by the detection circuit 5, and the inclination of the coordinate indicator 8 can be detected by comparing the magnitudes of the left and right antiphase components.

In the present embodiment, the phase inverting circuit 3 is placed before the amplifier circuit 4, but the order may be changed. Further, the amplifier circuit 4 may be saturated so that the oscillation signal 101 has a predetermined amplitude, but the amplifier circuit 4
A more stable oscillating operation can be obtained by adding the AGC circuit to and operating.

Next, a second embodiment of the present invention will be described with reference to FIGS. FIG. 8 is a block diagram of this embodiment. In the figure, 3a is the phase inversion circuit of the second embodiment, and the other parts are the same as those in FIG. FIG. 9 is a configuration diagram of the phase inversion circuit 3a, and shows the first sense line group S1 and one sense line yk of the first scanning circuit 1 (shown in FIG. 2). Phase inversion circuit 3a
Is constituted by, for example, an analog switch 74HC4052, and the connection of the sense line yk is switched by the control signal 104.

As is clear from the figure, the phase inversion circuit 3a
By switching the connection of the sense line yk, the phase in the positive feedback loop can be rotated by 180 degrees, and as in the first embodiment described above, oscillation in the negative phase component is possible and the magnitude of the negative phase component is large. Therefore, the tilt detection can be detected by the coordinate detection circuit 5.

Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 10 is a block diagram of this embodiment, and the symbols are the same as those in FIG. In this embodiment, the phase inversion circuit 3a is inserted between the second sense line S2 and the second scanning circuit 2, and the operation is the same as in the second embodiment.

Not limited to the embodiment described above, the output of the amplifier, the first sense line, the resonance circuit, the second sense line, and the input of the amplifier can be used in any place of the positive feedback loop. Obviously, the inclination can be detected by providing the phase inversion circuit that can change the phase by 180 degrees.

Further, in these embodiments, the first sense line group and the second sense line group are laid so as to be orthogonal to each other so as not to be directly coupled. However, as described above, in the coordinate reading apparatus of the present invention, various laying methods can be considered in which the oscillation frequency of the oscillation signal does not cause direct coupling between both sense line groups.
Although not shown, for example, if two sense lines laid in the same direction are laid so as to partially overlap each other, direct coupling can be canceled. In this case as well, coupling occurs when the resonance circuits are close to each other, so that the coordinates can be detected by the principle described here. The coordinate reading device can be configured by laying a plurality of such sense lines.

[0038]

As described above, according to the present invention, the oscillation signal related to the position of the coordinate indicator is obtained by the simple structure of inserting the resonance circuit of the coordinate indicator in the positive feedback loop of the amplifier circuit. Then, the coordinate reading device was configured to calculate the coordinates from this. Therefore, the excitation circuit is not required and the circuit can be simplified.

Further, since the oscillation frequency of the oscillation signal becomes the resonance frequency of the resonance circuit of the coordinate indicator, the resonance frequency can be arbitrarily set, and therefore the coordinate indicator can be adjusted without any adjustment. I was able to measure simplification. Further, even if the resonance frequency fluctuates, it does not affect the coordinate calculation, so that a stable coordinate reading device can be realized for a long period of time.

Further, since the signal of the anti-phase component can be detected by the phase inverting circuit, it is possible to realize the coordinate reading device capable of detecting the inclination.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a first embodiment of a coordinate reading device according to the present invention.

FIG. 2 is a configuration diagram of a first scanning circuit in the first embodiment of the coordinate reading device of the present invention.

FIG. 3 is a configuration diagram of a phase inversion circuit in the first embodiment of the coordinate reading device of the present invention.

FIG. 4 is a configuration diagram of a coordinate detection circuit in the first embodiment of the coordinate reading device of the present invention.

FIG. 5 is a waveform diagram of an oscillation signal in the first embodiment of the coordinate reading device of the present invention.

FIG. 6 is an explanatory diagram for calculating coordinates in the first embodiment of the coordinate reading device of the present invention.

FIG. 7 is a distribution diagram of a magnetic field generated from the coordinate indicator in the first embodiment of the coordinate reading device of the present invention.

FIG. 8 is a configuration diagram of a second embodiment of the coordinate reading device according to the present invention.

FIG. 9 is a configuration diagram of a phase inversion circuit in a second embodiment of the coordinate reading device of the present invention.

FIG. 10 is a configuration diagram of a coordinate reading device according to a third embodiment of the present invention.

[Description of Reference Signs] 1 first scanning circuit 2 second scanning circuit 3 phase inversion circuit 4, 50 amplification circuit 5 coordinate detection circuit 8 coordinate indicator 51 rectification circuit 52 smoothing circuit 53 A / D conversion circuit 54 control circuit 101 Oscillation signal 102 Input signal 104 Control signal 105, 106 Selection signal S1 First sense line group x1, x2, x3, x4 to xm-1, xm Second sense line y1, y2, y3, y4 to yn-1, yn first sense line

Claims (1)

[Claims] 1. A phase inversion circuit, an amplification circuit, a first sense line group which is parallel to one of the XY orthogonal coordinate axes and is composed of a plurality of sense lines, and the first sense line group is sequentially selected. A first scanning circuit, a second sense line group that is parallel to the other axis and is composed of a plurality of sense lines, a second scanning circuit that sequentially selects the second sense line group, and a coordinate detection circuit. And a coordinate indicator having a resonance circuit. The coordinate detection circuit controls the first and second scanning circuits to detect the first and second sense circuits. A line is selected, and the resonant circuit is electromagnetically coupled to both the first and second sense lines to form a positive feedback loop together with the phase inversion circuit, the amplifier circuit, and the first and second sense lines. A coordinate reading device configured to calculate coordinate information of the coordinate indicator from amplitude information of oscillation generated by the oscillator circuit when the oscillator circuit is formed.