JPS584382B2 - coordinate reading device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention applies an alternating magnetic field generated from a coordinate indicator to a conducting wire laid on a tablet, detects the magnitude of induced voltage induced in this conducting wire, and determines the position of the coordinate indicator. The present invention relates to an automatic coordinate reading device for determining coordinates.

For coordinate reading devices used for certain purposes, 1
There is a need for a mechanism that can perform work using a plurality of coordinate indicators on a single tablet and obtain position coordinate outputs for each coordinate indicator.

In order to achieve this requirement, conventionally, the frequency mode of the alternating magnetic field generated by each coordinate indicator is different, and the induction signal detection system is equipped with a circuit that distinguishes each frequency mode. A method has been proposed that performs coordinate value detection processing by distinguishing between vessels.

However, this method requires multiple oscillation circuits and frequency mixing circuits to generate excitation signals, as well as filter circuits to discriminate between frequency modes, resulting in extremely high circuit costs and the accuracy of these circuits depending on each indicator. This method is impractical because it affects position detection accuracy and requires extremely troublesome circuit adjustment.

This invention was made in view of the above points, and it generates an alternating magnetic field by sequentially and selectively supplying excitation signals to a plurality of coordinate indicators, and at the same time generates a bundle of conductive wires of a tablet at a speed sufficiently higher than the excitation switching speed. The present invention provides a coordinate reading device configured to perform coordinate detection processing for each coordinate indicator in a time-sharing manner.

Embodiments of the present invention will be described in detail below with reference to the drawings.

As shown in FIG. 1, the basic structure of the tablet 1 is that a plurality of folded X-axis sense lines Xl (X1, The Y-axis sense lines Yl (¥1+Y2+...Ym) are arranged in parallel at a pitch of They are arranged in parallel.

One end of each X-axis sense line Xi is connected to each output end of an X-axis scanning circuit 3X consisting of a decoder, and one end of each X-axis sense line Xi is connected to each output end of an X-axis scanning circuit 3X consisting of a decoder.
Each end of j is connected to the Y-axis scanning circuit 3Y.

Further, the other ends of each sense line Xi, Yj are connected to a common output line l via a diode D, respectively.

As described later, the scanning circuits 3X and 3Y
A scanning signal is sequentially applied to each sense line in the order of ...→Xo→Y1→Y2...→Ym.

In this embodiment, there are three coordinate indicators 4a, 4b and 4c.
is available.

Of these, the coordinate indicators 4a and 4b are the same, each having an excitation winding 5 of a predetermined diameter attached to the tip of a pen containing a writing instrument such as a ballpoint pen.

These two indicators 4a and 4b are also simply referred to as pens.

The coordinate indicator 4c is a flat cursor that slides smoothly on the tablet 1 and has an excitation winding 5 of a predetermined diameter attached thereto, and is also simply referred to as a cursor.

In addition, when inserting any of these three indicators,
It is written as coordinate indicator 4.

Although not shown, each of the pens 4a and 4b has a built-in pen switch that operates when pressure (writing pressure) above a certain level is applied to the tip of the pen, and the output of the switch serves as a command signal for reading coordinates. .

Generally, coordinates are specified using the pens 4a and 4b in the same manner as when writing on the tablet 1.

Therefore, the cursor 4C is used when directly inputting information such as handwritten characters, etc. On the other hand, the cursor 4C is mainly used when reading the coordinates of a necessary point on a drawing placed on the tablet 1 with high precision. used.

As described above, there are coordinate indicators with various types of characteristics.

6 is a predetermined frequency f.

7 is an amplifier that amplifies the output of the oscillator 6; 8 is an excitation device that selectively switches and supplies the output of the amplifier 7 to the excitation windings 5 of the three coordinate indicators 4a, 4b, and 4c. It is a switching circuit.

This switching circuit 8 is composed of a C-MOS type analogue switch, and its switching operation is controlled by an arithmetic control section 16, which will be described later.

The coordinate indicator 4 supplies an excitation signal to the excitation winding 5 via the switching circuit 8 at a frequency f.

An alternating magnetic field is generated.

When the coordinate indicator 4 that generates an alternating magnetic field is placed on the tablet 1, an alternating current signal of frequency fo is induced in the sense lines Xi, Yj near the coordinate indicator 4 by the magnetic induction of the alternating magnetic field.

The induced signals induced in the sense lines Xi, Yj are superimposed on the scanning signals and passed through the diode D only when the scanning signals from the scanning circuits 3X, 3Y are applied to the sense lines Xi, Yj. It is led out to the output line l.

In other words, the induced signals from each sense line appear in order on the output line 1 as the sense line is scanned.

The signal appearing on the output line l is amplified by an amplifier 9 to a frequency f.

The pass band is supplied to the Oki transducer 10.

As a result, the induced signal caused by the alternating magnetic field is discriminated, and the band P wave device 10 outputs a signal of the form shown in FIG. 2a, for example.

This output is amplified by an amplifier 11, full-wave rectified by a rectifier circuit 12, and further smoothed by a low-frequency P wave generator 13, as shown in FIG.
The result is a signal with a smooth waveform as shown in .

Each voltage V,,V2,... in this Fig. 2b
corresponds to the induced signal level of each sense line.

The output of the low-pass p-wave converter 13 is input to an A/D converter 15 via an amplifier 14.

By the way, as mentioned above, the pens 4a, 4b and the cursor 4c
Since the shapes of the tablets and tablets differ greatly, in many cases, the diameter and number of turns of the excitation winding 5 are different, and the distance between the tablet 1 surface and the excitation winding 5 when pointing on the tablet 1 is also different.

Therefore, the electromagnetic coupling characteristics with respect to the tablet 1 are different between the pens 4a, 4b and the cursor 4c, and generally a larger induced signal can be obtained with the cursor 4c.

In order to compensate for the difference in the induction level between the pens 4a, 4b and the cursor 4c, the gain of the amplifier 9 is manipulated.

That is, 23 is a gain switching circuit that switches the return resistance value related to the gain of the amplifier 9 into two stages. It is controlled in conjunction with the excitation switching circuit 8.

To explain in detail, when the switching circuit 8 supplies an excitation signal to the pen 4a or 4b, the switching circuit 23 sets the gain of the amplifier 9 to a high value for processing the induced signal by the pens 4a, 4b, and the switching circuit 8 sets the gain of the amplifier 9 to a high value for processing the induced signal by the pens 4a, 4b. When an excitation signal is supplied to the switching circuit 23, the gain of the amplifier 9 is set to a low value for processing the induced signal by the cathode 4c.

The arithmetic control section 16 is mainly composed of a microcomputer that has been converted into firmware, and includes a microprocessor 17, a memory 18, and an interface 19.20.
Consists of etc.

In addition to controlling the switching circuits 8 and 23, the arithmetic control section 16 also controls the scanning of the sense lines via the address register 21, and at the same time performs processing to obtain coordinate values based on the output of the A/D converter 15. and then connect the external device 22.
Controls the main processing of this device, such as input/output processing between

An outline of the basic control operation by the arithmetic control section 16 will be explained according to the flowchart of FIG.

This flowchart shows three coordinate indicators 4a, 4b, 4.
This is the case when c is used concurrently.

First, in step 1, the switching circuit 8 is controlled to supply an excitation signal to the excitation winding 5 of the first pen 4a to generate an alternating magnetic field from the pen 4a. Set the gain to a high value.

The next step 2 is a routine for detecting the coordinates indicated by the pen 4a. Details will be described later, but in short, the sense line is scanned at high speed, and the induced voltage obtained from the A/D converter 15 is sequentially introduced at that time. This means that the coordinate values of the indicated point are determined from each voltage value.

Once the coordinate values are determined in the coordinate detection routine of step 2, the values are temporarily stored as the indicated position by the first pen 4a. 1 above is not specified), executes invalidation processing to be described later, and proceeds to the next step 3.

In step 3, the switching circuit 8 is controlled to switch the second pen 4b.
An excitation signal is supplied to the excitation winding 5 of the pen 4b to generate an alternating magnetic field from the pen 4b.

The next step 4 is the same coordinate detection routine as step 2, and when the indicated coordinate values are obtained by executing this routine, the values are temporarily stored as the indicated position by the second pen 4b.

In the next step 5, the switching circuit 8 is controlled to supply an excitation signal to the excitation winding 5 of the cursor 4c.
The switching circuit 23 generates an alternating magnetic field from c.
is controlled to lower the gain of the amplifier 9.

The next step 6 is the coordinate detection routine described above, and when the indicated coordinate values are obtained by executing this routine, the values are temporarily stored as the indicated position by the kernel 4c.

The next step 7 is an output routine in which the coordinate values obtained in the coordinate detection routines of steps 2, 4, and 6 are made to correspond to the first pen 4a, the second pen 4b, and the cursor 4c, respectively. The data is output to a predetermined external device 22 in the same format.

Then control is returned to the first step.

By repeating the above steps 1 to 7 at high speed,
An alternating magnetic field is generated selectively from the three coordinate indicators 4a, 4b, and 4c, and a coordinate detection routine is executed each time each coordinate indicator 4a, 4b, and 4c is excited, and the coordinates of each indicated position are detected. The value is output.

With recent technology, the processing speed described above can be made sufficiently high, and therefore, although it is a time-divisional process, it is possible to use the three coordinate indicators 4a, 4b, and 4c in parallel.
The sampling rate for each indicator can also be kept high enough.

In addition, when using both the pen 4a and the cursor 4c, it goes without saying that the two coordinate indicators may be alternately excited.

In other words, although not shown, the use or non-use of each coordinate indicator is input to the arithmetic control unit 16 by a predetermined input means, and the arithmetic control unit 16 changes the switching circuits 8 and 23 accordingly. This is why the control mode is selected.

Here, details of coordinate detection will be explained.

When pointing on the tablet 1 with the coordinate indicator 4, in the vicinity of the pointing point, a sense line with a small distance to the pointing point,
A large induced voltage can be obtained.

For example, regarding the X-axis, between the sense lines Xi and Xi+1,
1, the closest induced voltage Vp is obtained from the sense line Xi closest to the indicated point, and the induced voltages Vp-1 and Vp+1 are obtained from the sense lines Xi-1 and Xi+1 on both sides, respectively. (In this example, vp-1<Vp+1)
is obtained.

Here, the arrangement pitch of the sense lines is T, and the sense lines Xi
Letting the distance between and the indicated point be ΔX, the coordinate value X of the indicated point can be expressed as: X=TXi+ΔX.

Of these, data (TXl) can be easily obtained from the address of the sense line where the maximum value occurs.

ΔX is called an interpolation distance, and in this embodiment, it is determined as follows.

That is, the most induced voltage V obtained from the sense line Xi
Based on the induced voltages vp-1 and Vp+-1 obtained from the sense lines Xl-1 and Xi+1 on both sides, (Vp-
The distance ΔX is determined from the ratio of Vp-1) and (Vp-Vp+1).

Specifically, the voltage ratio Q defined by the following equation (1) is determined.

This Q is 0 for △X in the range 0≦△X≦T/2.
It is a negative function of ΔX that takes a value in the range of ≦Q≦1, and is expressed as follows.

If the function table of the above equation (2) is obtained experimentally in advance, Vi
, Vi-1, and Vi+1 are detected, the voltage ratio Q of equation (1) is calculated, and the interpolation distance ΔX is determined from the interpolation function table of equation (2).

In other words, the final coordinate values are as follows.

By the way, pen 4a. It was previously explained that the electromagnetic coupling characteristics to the tablet 1 are different between the cursor 4b and the cursor 4c, and this difference also affects the interpolation function.

Therefore, in this embodiment, the interpolation functions for the pens 4a and 4b and the interpolation function for the cursor 4c are determined experimentally, and the two types of function table data are stored in advance in the memory in the calculation control unit 16. .

Then, in steps 2 and 4 of FIG. 3, ΔX is determined based on the interpolation function table for the pen, and in step 6, ΔX is determined from the interpolation function table for the cursor.

FIG. 4 is a flowchart showing the contents of the coordinate detection routine.

According to this, the operation of the arithmetic control section 16 will be explained.

First, run the initializer routine in step 1,
Set internal registers (■o) and (Sx) to 0.

In the next step 2, the contents O of the register (Sx) are written into the address register 21.

As a result, a scanning signal is applied to the sense line X1, and the detection voltage 1 obtained from the sense line X1 is input to the A/D converter 15.

In the next step 3, the A/D converter 15 is activated at an appropriate timing when the detected voltage input is stabilized.

In the next step 4, wait for the conversion end signal from the A/D converter 15, and when the conversion is completed, in the next step 5, the digitally converted detection voltage ■1 is taken in, and the internal register (■ 1).

In the next step 6, it is determined whether the contents of the register (1), that is, the detected voltage (1) is larger than a preset threshold value Vn (slightly larger than the noise level).

(■1) If <(Vn), jump to step 10; if (Vt)≧(Vn), jump to the next step 7, (
(2) Determine whether the value of 1) is greater than the value of (Vo).

Since the value of (■o) is 0 as mentioned above, first (■1
)≧(■o).

In that case, in the next step 8, set the value of (VO) to the register (
v-i), and further in the next step 9, the value of (■1) is transferred to (Vo).

Then, in step 10, the X-axis sense line address (Sx)
is incremented, and in step 11 it is checked whether (Sx) is the final address of the X-axis sense line, and if it is not the final address, the process returns to step 2.

The X-axis scan progresses in the above manner.

At this time, if the coordinate indicator 4 that generates an alternating magnetic field is not present on the tablet 1, scanning proceeds to the final address on the X axis without obtaining a detection voltage equal to or higher than the threshold value (Vn).

Then, it is determined NO in step 11, in which case,
The invalidation processing routine of step 12 is executed, an invalidation signal is output to the external device, and a lamp or the like is turned on.

Furthermore, if the coordinate indicator 4 is pointing on the tablet 1, the detected voltage will increase as the X-axis scan approaches the specified position, and the detected voltage will decrease as the X-axis scan exceeds the specified position. .

This change in detection voltage from increase to decrease is detected in step 7.

In other words, when the detection voltage is increasing, the register (VO
) is always stored with the maximum value, and when the latest detected voltage (V1) becomes less than (■o), a negative determination is made in step 7.

At that point, the maximum value of the detected voltage is stored in the register (■o), and the sense line Xi-i, which is one address before the sense line Xi that generated the maximum value, is stored in the register (v-i). The detected voltage from 1 is stored and the register (■
+1) is the sense line X1 after one address of the sense line Xi.
The detected voltage from +1 is stored.

If the determination in step 7 is NO, the process proceeds to step 13, where the magnitude of the value of (V-1) and the value of (V+1) is determined. Calculate the ratio Q.

In the next step 15 or 15', the interpolation distance ΔX expressed by equation (2) is determined from the above-mentioned interpolation function table (so-called ROM table) based on the calculated Q.

Next, in step 16 or 16', the equation (
3) Calculate the X coordinate represented by and temporarily store it in a predetermined register.

Next, although shown as step 17 in the figure, the above control for detecting the X coordinate is performed on the Y axis, and the Y coordinate of the designated position is determined and temporarily stored.

Note that step 17 also includes the same invalidation processing routine as step 12 above.

Note that if the threshold value Vn in step 6 is constant, a so-called chattering phenomenon is likely to occur in a transient state in which the coordinate indicator 4 approaches and moves away from the tablet 1.

To prevent this, for each coordinate indicator, we remember whether the indicator is disabled (not on the tablet) or valid (pointing on the tablet) at the end of the latest scan. , At the time of the next scan, the threshold value Vn is set to an appropriately large value for the indicator in the invalid state, and the threshold value Vn is set to an appropriately small value for the valid indicator.

As a result, so-called hysteresis occurs between the approaching and separating movements of the coordinate indicator and the valid/invalid determination operation, making it possible to prevent chattering.

As explained in detail above, the coordinate reading device according to the present invention sequentially and selectively supplies excitation signals to a plurality of coordinate indicators to generate an alternating magnetic field, and senses the coordinates at a sufficiently higher speed than the excitation switching speed. Because it performs line scanning and detects the indicated coordinate value for each coordinate indicator, it requires less circuitry than the conventional method in which the frequency mode of the alternating magnetic field generated by each coordinate indicator is different. The configuration is very simple, and it is also easy to compensate for characteristics that vary depending on the type of coordinate indicator.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the overall configuration of a coordinate reading device according to the present invention, FIGS. 2a and 2b are waveform diagrams of guiding signals, and FIG.
The figure is a flowchart of the basic operation of this device, and FIG. 4 is a flowchart of the coordinate detection routine. 1...Tablet, Xi, Yj...Sense line, l...Output line, 3X, 3Y...
・Scanning circuit, 4a, 4b...Coordinate indicator (pen), 4c...Coordinate indicator (cursor), 5...
... Excitation winding, 6 ... Oscillator, 8 ...
...Excitation switching circuit, 16... Arithmetic control section, 23
...Gain switching circuit.

Claims (1)

[Claims] 1 A tablet formed by laying a large number of sense wires at regular intervals, a plurality of coordinate indicators having an excitation winding for applying an alternating magnetic field on the tablet, and an excitation winding of the plurality of coordinate indicators. an excitation switching circuit that sequentially and selectively supplies an excitation signal to the excitation switching circuit; and an excitation switching circuit that scans the sense lines at a sufficiently high speed than the switching operation of the excitation switching circuit, and detects induced signals induced in each sense line by the alternating magnetic field. A coordinate reading device comprising: an arithmetic control unit that detects and determines the position of a coordinate indicator generating an alternating magnetic field from the guidance signal level, and is capable of detecting the position coordinates of each coordinate indicator.