JPH0424718A - Wireless coordinate reader - Google Patents

Abstract

PURPOSE:To detect coordinates at high speed by calculating the position of placing a coordinate indicator from a guide signal caused by electromagnet coupling between the coordinate indicator and a sense line, by detecting the coordinate detection by measuring time with a scanning counter. CONSTITUTION:A transmission circuit 4 to generate the fundamental clock of the reader, and a scanning counter 5 are provided. When a coordinate indicator indicator 10 is placed near an area where an exciting line crosses the selected sense line, the guide signal is generated in the selected sense line, and a comparator 8 detects a signal higher than a fixed level. According to this signal, a control circuit 9 stops the counting operation of the scanning counter 5. The count value at that time expresses the coordinate value in a scanning direction, and the coordinate value is decided. Thus, the coordinate value can be easily calculated at high speed in a wireless condition.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a coordinate reading device that inputs coordinates to an external device such as a computer, and particularly! Applying magnetic induction phenomenon! This invention relates to a magnetic induction type coordinate reading device.

[Conventional technology]

Conventional coordinate reading devices include Japanese Patent Application Laid-Open No. 52-96825 and Japanese Patent Application Laid-Open No. 55-9641, invented by the present applicant.
There is No. 1.

These coordinate reading devices will be briefly explained.

FIG. 8 is a configuration diagram of a conventional coordinate reading device.

A plurality of loop-shaped sense line groups 901 are laid out on the tablet, which is a coordinate reading board. In FIG. 8, the tablet is not explicitly shown.

These sense line groups 901 are selected one by one by a scanning circuit 902. The output of the scanning circuit 902 is connected to a signal processing circuit 905, and this output is further connected to a control circuit 9.
Connected to 06. The control circuit 906 is also configured to apply a scanning signal 3901 to sequentially select the scanning circuits 902. On the other hand, the coordinate indicator 907 has a built-in coil 907a, and is connected to an excitation signal generation circuit 904 built into the tablet through an excitation signal line 908.

With the above configuration, coordinate values are calculated as follows. The coordinate indicator 907 is placed on the sense line group 901 and constantly generates an alternating magnetic field in response to a signal from the excitation signal generation circuit 904. A control circuit 906 sequentially selects a scanning circuit 902 by applying a scanning signal 5901. Since an induced current corresponding to the position of the coordinate indicator 907 is generated in the sense line group 901, by selecting the sense line group 901 by the scanning circuit 902, the sense line group 901 is sent to the signal processing circuit 905. The guidance signals 5902 for each are sequentially input. The signal processing circuit 905 is adapted to generate envelope waveforms of these induced signals. The control circuit 906 inputs the amplitude of the induced signal for each sense line from this envelope waveform, and calculates coordinate values by comparing and calculating the amplitudes.

[Problem to be solved by the invention]

However, in this conventional coordinate reading device, in order to generate a magnetic field from the coordinate indicator, it was necessary to apply an alternating current signal to the coordinate indicator. For this purpose, it was necessary to connect the tablet and the coordinate indicator with a signal line.

In addition, in order to calculate the coordinate values, it is necessary to manually calculate the amplitude of the guidance signal and perform arithmetic processing on it, so a processor with an A/D converter as an input circuit is used in the control circuit to perform the calculation. Program processing was also required. There is a problem in that the processing becomes complicated and takes a long time, making it impossible to speed up the processing.

The present invention has been made to solve the above-mentioned problems in conventional coordinate reading devices, and its first purpose is to eliminate the need to connect a coordinate indicator and a tablet with a signal line. , to realize a wireless coordinate reading device. A second object is to realize a coordinate reading device that can calculate coordinate values simply and at high speed.

[Means to solve the problem]

In order to solve the above problems, the present invention has configured a coordinate reading device with the following configuration.

a plurality of sense line groups laid parallel to each other at equal intervals in the direction of detecting coordinates; an excitation line laid in a direction perpendicular to the sense line groups; and one of the sense line groups. A scanning circuit that selects the sense line, an oscillator circuit that generates the basic clock of the device, and a control circuit that receives counting permission and stop, counts the basic clock when permission is granted, and transmits the count value to the scanning circuit. a scanning counter that outputs to the circuit; an excitation circuit that divides the frequency of the basic clock signal and provides an excitation signal that is an alternating current signal to the excitation line; and an excitation circuit that is placed on the sense line group to , and a coordinate indicator configured of a resonant circuit having a coil and resonating with an alternating current signal generated by the excitation circuit so as to be electromagnetically coupled to the sense line group; a phase detection circuit that detects the phase of the induced signal induced in the sense line group by electromagnetic coupling with the sensor; a comparator that detects a signal output from the phase detection circuit that is at a certain level or higher; and a count of the scanning counter. A control circuit is provided that allows the scanning counter to operate and stops the counting operation of the scanning counter by inputting a detection signal output from the comparator.

[Effect]

The control circuit allows the scan counter to perform a counting operation, and the count value of the scan counter is provided to the scan circuit. Therefore, the sense line groups are sequentially selected and connected to the phase detection circuit. The excitation line is connected to an excitation circuit to generate an alternating magnetic field.

On the other hand, a coordinate indicator is placed on the sense line to indicate the position. When this coordinate indicator is placed near the head where the excitation line and the selected sense line intersect, the coordinate indicator is configured to resonate with the excitation signal, so the excitation line and the coordinate indicator Due to the coil and the electromagnetic coupling between the coil and the sense line, an induced signal is generated on the selected sense line. This induced signal is phase-detected, and a signal above a certain level is detected by a comparator. The control circuit stops the counting operation of the scan counter by inputting this detection signal. When the scanning counter stops counting, the count value represents the coordinate value in the scanning direction, and the coordinate value is determined.

〔Example〕

A first embodiment of the present invention will be described below with reference to FIGS. 1 to 7.

Although not clearly shown in the figure, the coordinate reading device is broadly divided into a coordinate reading board called a tablet and a coordinate indicator. The coordinate indicator can be moved freely on the tablet and is used to indicate the position where coordinate values are to be read.

(Configuration of coordinate reading device) First, the configuration will be explained. FIG. 1, FIG. 2, and FIG. 4 show configuration diagrams of a coordinate reading device according to the present invention.

In FIG. 1, 1 is a sense line group.

Each sense line is laid out in the tablet so that it is equally spaced and parallel to each other in the coordinate detection direction. The spacing between the sense lines is the sense line pitch p5, for example p5 = 5.4rnm
degree. One end of each sense line is connected to each other and grounded. The other ends are each connected to a scanning circuit 3.

Reference numeral 2 denotes an excitation line, which is laid orthogonal to the sense line group. One end of the excitation line is grounded, and the other end is connected to the excitation circuit 6.

The scanning circuit 3 is composed of a plurality of electronic switching elements such as analog switches, and one terminal of each switching element is connected to each other to serve as a common terminal. The selection signal closes one of the switch elements and connects one end of the switch element to the common terminal.

4 is an oscillation circuit that generates the basic clock a of the device.

The scanning counter 5 counts this basic clock a,
A part of the upper bits of the count value is given to the scanning circuit 3 as a sense address b.

The scanning counter 5 receives control of a scanning signal d from a control circuit 9, which will be described later, to enable/stop counting.

The excitation circuit 6 is a counter that divides the basic clock a, and supplies an excitation signal C to the excitation line.

The excitation circuit 6 and the scanning counter 5 need to have a specific frequency division ratio. This will be explained with reference to FIGS. 2 and 3. FIG. 2 is a configuration diagram of the scanning counter and excitation circuit, and FIG. 3 is a timing diagram of the basic clock a, excitation signal C, and sense address b.

In this embodiment, the basic clock a is set to 1.2MH2. The excitation circuit 6 divides the basic clock a by 1/4 to 30
Create an excitation signal C of 0kHz.

The scan counter 5 divides the frequency by 1/16 and sets it as the least significant bit bO of the sense address b. The number of focus points used as sense addresses can be determined by the number of sense lines group l. In the example of FIG. This shows that the sense line group can be scanned.

The number of bits below the bits used as the sense address b of the scanning counter 5 is determined by the desired number of divisions into four between the sense lines. Detailer: As will be described later, in this embodiment, the sense line pitch pS is set to 6.4 mm, and by dividing this into 3 bits, 6.4/8-0.
I am trying to find the thickness standard value in units of 8mm.

On the other hand, the frequency division number of the excitation circuit 6 is selected so that the period of the excitation signal C is smaller than the period of change of the sense address bo. Further, the frequency of the excitation signal C is selected so that 1tM1 coupling can be performed efficiently and does not require a special circuit. Approximately several tens of kHz to several 100 kHz is appropriate.

FIG. 4 shows the configuration of the 0 phase detection circuit 7 in which both the i1 terminals of the scanning circuit B3 are connected to the input of the phase detection circuit 7. The phase detection circuit 7 includes an amplifier circuit 71 and an analog switch 72.
, a filter circuit 73, and a phase shift circuit 74. The amplifying circuit 71 is an amplifying circuit which is guided to the sense line and has an appropriate gain set according to the level of the guided signal e selected by the scanning circuit. analog switch 7
2 detects the amplified induced signal using a signal obtained by phase-shifting the excitation signal C output from the MjJ magnetic circuit 6 by the phase shift circuit 74 as a reference signal. Filter circuit 7
3 generates an envelope of the detected signal.

The configuration of the phase detection circuit 7 can be similarly configured by using an analog multiplier in addition to this embodiment, but the explanation will be omitted. Considering cost, etc., it is better to use an analog switch.

The comparator 8 outputs a detection signal g to the control circuit 9 when the envelope signal f to which the phase has been passed exceeds a certain level.

The control circuit 9 allows or stops counting of the scan counter 5 in response to the scan signal d.

The coordinate indicator 10 constitutes a parallel resonant circuit by a coil 10 and a capacitor 102. The resonance frequency is the same as the frequency of the excitation signal C generated by the excitation circuit 6.

(Operation of coordinate reading device) Next, the operation will be explained.

The control circuit 9 outputs the scanning signal d to permit the counting operation of the scanning counter 5. Since the upper bit of the count value of the scanning counter 5 is the sense address b to the scanning circuit 3, the sense line group 1 is sequentially selected in accordance with the counting operation.

On the other hand, the excitation line 2 is an excitation signal C output from the excitation circuit 6.
generates an alternating magnetic field.

Here, the coordinate indicator 1 is placed near the selected sense line.
The nature of the induced signal induced to the sense line when 0 is placed will be explained with reference to FIG. The magnitude of the induced signal is a function of the position of the coil IO1 in the coordinate detection direction. Figure 5 shows the coil 10 along the coordinate detection direction.
1 illustrates the amplitude of the induced signal induced in the sense line sli with respect to the position of the coil 101 when the coil 101 moves.

Since the excitation line 2 generates an alternating magnetic field by the excitation signal C, when the sense line sli is selected, an induced signal is generated in this sense line by the Xi Em coupling between the excitation line - coil 01 - sense line pitch. do. The amplitude of this induced signal tends to be maximum when the coil 101 is directly above the sense line sl+, freeze once as it moves away from the coil 101, increase again, and then gradually decrease. The reason why the maximum value of the amplitude is observed not only near the coil 101 but also around it is due to the effect of the opposite phase magnetic field generated by the coil 101. The signal with the maximum value is called a peak, and the local maximum value due to the opposite phase is called a secondary peak.

Next, the operation up to calculating the coordinates from the guidance signal e is performed in the sixth step.
This will be explained with reference to the timing diagram shown in the figure.

When the sense line group I is sequentially selected while the position of the coil 101 is kept constant, the induced signal e induced to each sense line is sequentially input to the phase detection circuit 7.

This induced signal e is amplified to a certain level by an amplifier circuit 7I in the phase detection circuit 7, and then phase-detected by an analog switch 72.

The phase of the induced signal e is softened by the effect of electromagnetic coupling and the effect of circuit characteristics. Therefore, (as the reference signal used for S-phase detection, a signal obtained by phase-shifting the excitation signal C is used. The detected induced signal becomes the detected signal i. As shown in the figure, the peak and secondary peak Since the phase is opposite to that of the opposite phase, signals with different polarities are detected at the door.

The detected signal 1 is transformed into an envelope signal f by the filter circuit 73.

The comparator 8 manually inputs this envelope signal r, detects a signal that is higher than a certain level of reference voltage vth, and generates a detection signal g.
Output. The reference voltage vth is set to a level that can be detected when a coordinate indicator is placed on the sense line.

When the control circuit 9 receives the detection signal g, the scanning signal d causes the scanning counter 5 to stop counting. At this time, the count value of the scanning counter 5 indicates the coordinate value.

The configuration of the scanning counter 5 will be explained again with reference to FIG. 2 in relation to the principle of generating detailed coordinate values between sense lines. As shown in FIG. 6 (bl), this coordinate reading device attempts to obtain coordinate values by measuring the time from the start of scanning until the envelope line signal f rises with a counter.

When the scanning counter 5 stops counting, the sense address b indicates that the coil 101 is placed near the sense line indicated by this sense address. The sense line pitch pS is 6.4m as mentioned above.
Since the value is m, it is 6.4 mm depending on the sense address.
The position of the coil 101 can be known in units.

The detailed position between the sense lines is determined by utilizing the fact that the distribution of the envelope signal f changes depending on the position of the coil. For example, as shown in FIG. 7, the coil 101 moves from the center pI of the sense line sli to p3 between sll and s]i+l.
, the envelope line signal f moves along with it in the scanning direction. In terms of time, this movement is a change in time that is less than the period in which the sense address is updated, and this movement is expressed as the lower bit of the scan counter j
It is counted by. As described above, by counting using the lower bits, the sense lines can be divided into units of 0.8 mm.

Conventional coordinate reading devices require about 150 to 200 μsec per sense line to select a group of sense lines. Therefore, for example, a time of about 1.2 to 1.6 m5ec was required to scan eight sense lines.

According to the coordinate reading device according to this embodiment, as shown in FIG. 3, the period of change in the sense address is about 13 μsec, and even when scanning 8 trees, it is at most 104 μsec. It has become possible to detect coordinates at high speed.

[Effects of the Invention] As explained above, in the present invention, a plurality of sense lines and excitation lines are provided, the excitation line is excited, and the coordinate indicator is configured to resonate with the excitation signal. The position of the coordinate indicator is determined from the induction signal generated by electromagnetic coupling between the indicator, the coordinate indicator, and the sense line. Therefore, unlike conventional coordinate reading devices, it is no longer necessary to apply an excitation signal to the coordinate indicator, so a wireless coordinate reading device is realized that does not require a signal line to connect the coordinate indicator and the tablet. We were able to.

Furthermore, since coordinate detection is performed by time measurement using a scanning counter, it is possible to realize a coordinate reading device that can detect coordinates at a higher speed than in the past.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of an embodiment of a coordinate reading device according to the present invention;
Figure 2 is a configuration diagram of the scanning counter and excitation circuit, Figure 3 is a timing diagram of the basic clock/excitation signal and sense address, Figure 4 is a configuration diagram of the phase detection circuit, and Figure 5 is the distribution of the induced signal. 6V is a timing diagram, FIG. 7 is an explanatory diagram of an operation for detecting a detailed position, and FIG. 8 is a configuration of a conventional coordinate reading device. 1 ・ ・ 2 ・ ・ 3 ・ ・ 4 ・ ・ ・ 5 ・ 6 ・ ・ 7 ・ ・ 8 ・ ・ 9 ・ ・ 10 ・ ・ 101 ・ 102 ・ Sense line group excitation line scanning Circuit, transmitter circuit, scanning counter, excitation circuit, phase detection circuit, comparator, control circuit, coordinate indicator, coil, capacitor

Claims (1)

[Claims] a. At equal intervals from each other in the direction of detecting coordinates, and
a plurality of sense line groups laid in parallel; b. an excitation line laid in a direction perpendicular to the sense line groups; c. a scanning circuit for selecting one sense line of the sense line group; d. an oscillator circuit that generates a basic clock of the device; e. a scanning counter that receives counting permission and stop control, counts the basic clock when permission is granted, and outputs the count value to the scanning circuit; f; an excitation circuit that divides the frequency of the basic clock and provides an excitation signal that is an alternating current signal to the excitation line; a coordinate indicator configured of a resonant circuit having a coil and resonating with an alternating current signal generated by the excitation circuit; a phase detection circuit that detects the phase of the induced signal induced in the sense line group; i. a comparator that detects a signal output from the phase detection circuit that is at a certain level or higher; and j. a count operation of the scanning counter. a control circuit configured to permit and stop the counting operation of the scanning counter by inputting a detection signal output from the comparator.