JPS5913074B2 - 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 the 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.

In order to read accurate coordinate values with a 10 coordinate reading device, the pitch of the conductive wires on the tablet must be arranged extremely accurately.

However, when the conductive wires are placed on the tablet by printed wiring, it is inevitable that slight irregular deformations during the manufacturing process will cause pin-point errors. In the case of printed wiring, pitch errors tend to be particularly large around the tablet. Even with other wiring methods, it is practically impossible to eliminate the pitch error, which causes a drop in coordinate reading accuracy (20). , a scanning line coordinate is obtained through a scanning line correction means for compensating for a pitch error of the scanning line by sending a scanning address signal to the scanning line laid on the tablet;
25, which eliminates the above-mentioned drawbacks and enables accurate coordinate reading.

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

FIG. 1 shows the tablet structure of the coordinate reading device according to the present invention, in which 1 and 2 are 30 flat plates made of insulating material, which are stacked on top of each other.

A plurality of folded scanning lines xl, x2...xn arranged in parallel and a plurality of scanning lines y1, y2...ym perpendicular to these are stretched over the flat plates 1 and 2. ,
Connect one end of each to the scanning circuits 3a and 3b (
・Ru. Furthermore, the other ends of the scanning lines X1, X2...Ψ are each connected to a rectifying element, such as a diode D.
D2...... is connected to Dm+n, and the other ends of these rectifying elements are all connected by a common line t to a common output terminal A.
A load resistor R is connected between this and the power supply.

Reference numeral 5 indicates an alternating magnetic field generator placed on the tablet, and the alternating magnetic field generator 5 winds a concentric excitation winding 5a.

This excitation winding 5a is connected to an alternating current signal source 6, and when an alternating current flows through the excitation winding 5a from the alternating current signal source 6, an alternating magnetic field is generated around the alternating magnetic field generator 5. Figure 2 shows
An example of the arrangement of the scanning line X on the tablet is shown. Incidentally, since the scanning line y has a similar arrangement to this, the detailed explanation will be omitted. The scanning lines X,, x2, . . . , Xn are arranged at a pitch with a distance r between adjacent scanning lines.

Note that this pitch γ is a unit of the basic length to be measured, for example, 0.01 [M, O.
For these scanning lines, the inner diameter of the excitation winding 5a of the alternating magnetic field generator 5 is set to an appropriate value of 2γ or more. These scanning lines X,, x2...Xn have square wave signals Sl, S2, S3... are outputted from the sequential scanning circuit 3a. Note that the square wave signals S,, S2, S3, and
As will be clear from the explanation given later, ... does not necessarily have to be a square wave (... The scanning signal S applied to the scanning line X,
, passes through the rectifying element D, and appears at the common terminal A. Below, when the scanning signals S2, S3... are applied to the scanning lines X2, X3, respectively, they appear sequentially at the common terminal A, but there is a deviation in the forward drop potential of each rectifying element D,, D2...Dn. Therefore, the output of the common terminal A has a random staircase waveform as shown in FIG. 3b. Here, when an alternating current signal is applied to the alternating magnetic field generator 5 from the alternating current signal source 6, the scanning line
, y, an induced voltage is generated. This induced voltage is most strongly induced near the alternating magnetic field generator 5. However, this induced voltage is caused by a voltage drop in the forward direction of the rectifying element (approximately 0.
6 to 0.7), so the scanning signal is not applied and does not appear at the output terminal A. Also, due to the unidirectionality of the rectifying element, for example, as shown in Figure 3a, When the scanning signals S, , s2...Sn shown in FIG.゛.If the scanning signal uses a signal with a negative direction waveform as opposed to the square waveform shown in Fig. 3a, the anode terminal of the rectifying element should be connected to the common one as shown in Figs. 1 and 2. If it is connected, it will not be scanned (・Reverse bias is applied to the rectifying element of the scanning line and it will be scanned in the same way (・) The induced voltage induced in the scanning line will not appear at the common terminal A (・.
The signal appearing in is the scanning signal and the flow of that scanning signal (・
Only the induced signal on the scanning line is generated. When the alternating magnetic field generator 5 is placed close to the first scanning line Xi on the tablet, the induced voltage superimposed on the scanning signal at the common terminal A becomes maximum at the scanning signal Xi, as shown in Figure 3c. .

The above induced voltage is between the center of the alternating magnetic field generator 5 and the scanning line
The closer the distance between the two is, the larger the voltage becomes, but the relationship between the distance and the induced voltage has a positive arc wave shape as shown in FIG.

That is, the voltage values Vl, 2, and 3 induced in the scanning lines Xl, X2, and X3, respectively, have a positive arc wave shape in which the center of the alternating magnetic field generator 5 reaches its maximum at each turning point Pl, P2, and P3 of the scanning line. A curve is drawn, and the center of the alternating magnetic field generator 5 is the scanning line X1.
At a distance t from , there is an induced voltage Vc on the scanning line X1,
A is induced in the scanning line X2, and b is induced in the scanning line X3. FIG. 5 shows a circuit block diagram for coordinate value detection according to the present invention, and FIG. 6 shows signal waveforms at various parts thereof.

That is, as shown in FIG. 5, the AC signal source 6 has an oscillation circuit (not shown) that generates a plurality of frequency signals F., fl, f2, . . . Fm. The output signal of this AC signal source 6 may be independent of the signal of the induced voltage detection circuit.・Figure 6a shows two types of frequency signals F.

．． 5f shows the output signal of the common output terminal A when the alternating magnetic field generator 5 is excited by combining the signals. This composite output signal is discriminated by a band waver 17 having a viscous band, and the output side of the band waver 76 is shown in FIG. Waveforms with suppressed scanning signal components as shown in FIG. 6c are output. The output signal of the band wave generator 7 is further passed through the AGC circuit 8 to the rectifier circuit 9 where it is full-wave rectified and becomes a waveform signal shown in FIG. 6C. This signal is further smoothed by a low-frequency wave generator 10, as shown in Fig. 6g.
This becomes a smooth waveform signal, which is converted into a digital signal by the A/D converter 11 at the next stage and is applied to the maximum value comparison circuit 12. The maximum value comparison circuit 12 has at least three stages of shift registers 64 as shown in detail in FIG.
, 65, and 66, to which a guiding signal digitized from the analog signal shown in FIG.
Each of the registers 64, 65, and 66 has a shift input terminal (not shown), and these input terminals are connected in parallel, so that a shift signal is input to them each time the scanning address signal of the counter 15b changes. te℃・ru. In addition,
This shift signal can also be obtained by extracting a differential value from the output signal of the low-frequency wave generator 10 and using it. Compare each stored value in the register 64 at the first stage and the maximum value detection register 65 at the next stage. While the scanning signal approaches the alternating magnetic field generator 5, the induced output voltage gradually increases, and the value stored in the register 64 is always larger than the value stored in the register 65. When the scanning signal passes through the alternating magnetic field generator 5, the value stored in the register 65 becomes larger than the value stored in the register 64.
When the stored value of becomes larger, this value is set to the maximum value Va
, and transmits the maximum detection signal to the next-stage division circuit 13. Further, the value stored in the register 64 and the value stored in the third stage register 66 are compared by a comparator 69, and the output thereof is transmitted to a selection circuit 67. 66 memorized values are input,
From here, the register 64,
66, the larger stored value (Vb) is selected and sent to the division circuit 13 as a divisor.On the other hand, the register 65
The stored value of is sent to the division circuit 13 as the dividend, and these divisor and dividend inputs are triggered by the maximum value detection signal of the comparator 68, and the division circuit 13 calculates Va/Vb.
A division is performed. Note that from the comparator 69,
When the stored value of the register 64 is greater than the output of the register 66, a signal of 1 is transmitted, and when the value is smaller than or equal to the output, a signal of + is transmitted to the adder 16a, which will be described later. By the above-mentioned division in the division circuit 13, the thickness of the reading medium such as paper placed between the tablet and the alternating magnetic field generator 5, the impedance of the scanning line, the fluctuation of the alternating magnetic field, and the thickness of the insulating flat plates 1 and 2 are calculated. The influence of deviation etc. is removed. That is, if the parameter giving the above deviations is α, and the theoretical reference induced voltage is Vs, then
The actual induced voltage Vα is Vα=αVs...
.........It is expressed as (1).

The induced voltages Va, Vb, . . . in FIG. are Vsa, Vsb..., then Va=αVsa・
・・・・・・・・・・・・・・・(2) Vb=αSb・・
(3) The output from the division circuit 13 is VaαVsaVsaV R=-[MeH=?・・・・・・・・・(4) VbαSbV
sb, which is the value after removing the influence of the deviation parameter α.

Although not shown in FIG. 7, the maximum value signal stored in the register 65 is transferred to the register 71 of the AGC circuit 8 shown in detail in FIG.
This signal is further converted into an analog signal by a DA converter 72, and then inverted and amplified by a differential amplifier 73 to an arbitrary scale of the difference value with respect to the reference voltage, and the bias signal of the amplifier 70 is The gain of the input signal of the AGC circuit 8 is controlled as follows.

This determines the thickness of the reading medium and the alternating magnetic field generator 5.
Fluctuations in induced voltage due to deviations in excitation voltage can be reduced. As is clear from FIG. 4, the division output VR in the division circuit 13 changes according to the position of the alternating magnetic field generator 5, as shown in FIG. 9, with the minimum value set to 1. That is, the scanning line x of the alternating magnetic field generator 5 (at a certain degree C.
The position with respect to y) and the above division output 8 have a non-linear relationship, and the division output. It is not possible to calculate the position of the alternating magnetic field generator 5 between scanning lines from that point. (For example, read-only memory, programmable logic array, etc.) Add to 14.

This nonvolatile memory circuit 14 stores the curve relationship shown in FIG. 10 in correspondence with the change curve shown in FIG. That is, in FIG. 10, the horizontal axis represents the above division output. , the distance d from the position of VRrnn in FIG. 9 on the vertical axis is d≦a(a-γ
/2), and d for VR at each point obtained by dividing this curve into appropriate intervals, for example, distance d at equal intervals, is written in the memory circuit 14 in advance so as to obtain the desired distance resolution. Therefore, the division circuit 13
When the division output VR of
(Yi), that is, the inter-scanning line coordinate values are output. Reference numeral 15a in FIG. 5 is a clock signal generator for scanning signals, and this output clock signal is counted by a counter 15b.
The output signal is sent to the scanning circuits 3a, 3 as a scanning address signal.
b and the scanning lines Xl, x2,...Xn, y,, y
2... is sequentially decoded into an output signal that scans Ym. That is, the scanning address signal of the counter 15b mentioned above is also sent to the gate 4b. The gate 4b is an address selection gate that selects the address signal for scanning the final scanning lines Xn and ym of each of the X and Y axes among the scanning address signals, and when the scanning address signals corresponding to the above-mentioned Xn and Ym are input. A trigger signal is output to the flip-flop circuit 4a. The output terminal Q of the flip-flop circuit 4a is connected to the scanning circuit 3b, and the output terminal σ is connected to the scanning circuit 3a. After the scanning address signal is input to the gate 4b, the scanning circuit 3b operates, and the other scanning circuit 3a does not operate.
After the scanning address signal corresponding to Ym is input to the gate 4b, the scanning circuit 3a operates and the other scanning circuits 3b do not operate. Then, as shown in FIGS. 1 to 3, the signals are superimposed on the scanning signals that are sequentially sent to the scanning lines and are output from the common output terminal as described above. f
The induced output signals having frequency components such as 1 are sent one after another to the band ▲ wave generators 7 and 17. In addition, the above counter 1
The scanning address signal 5b is sent to the comparator 68 of the maximum value comparison circuit 12 via an initial scanning signal liminator (described later).
The stored value (the previous address signal) is input to the latch register 20 with a two-stage shift register controlled by the output signal of the comparator 68, that is, the maximum value comparison circuit 12 When the maximum value is detected, it is output from the latch register 20, and is output to the X coordinate scanning line coordinate correction means 22 and the Y coordinate scanning line coordinate correction means 23, which will be described later.
sent to.

These correction means use the output of the flip-flop 4a to scan the X-coordinate scanning line (.
・The scanning line coordinate correction means 23 for the Y coordinate comes into operation when the above scanning line correction means 22 and 2
3 uses a non-volatile memory such as a programmable logic array (ROM), for example, to correct the accumulated pitch error of the scanning lines determined in advance to determine the theoretical scanning line coordinates. This is to get the value output.

In addition, if the single pitch error cannot be ignored with respect to the cumulative pitch error, the single pitch error correction means 24,
24V is provided, and the scanning address signal from the latch register 20 is input to a part of the address input terminal, and the output of the non-volatile memory circuit 14 (or the division circuit 13) is input to the remaining input terminal. A single pitch error correction value is output from the single pitch error correction means 24 or 24' depending on the combination. Single pitch error correction means 2
4 is for the X coordinate, and 24' is for the Y coordinate, and scanning line coordinate correction means 22 and 23 are respectively provided by the output of the flip-flop 4a.
controlled in the same way. The coordinate value output of the scanning line coordinate correction means 22 or 23, the inter-scanning line coordinate value output of the memory circuit 14, and the single pitch error correction value of the single pitch error correction means 24 or 24' are as follows: The signals are input to the adder 16a and added and subtracted.

That is, the coordinate value output is placed at the top, the inter-scanning line coordinate value output from the comparator 69 is placed at the bottom with a 2 sign, and the single pitch error correction value (with 2 sign) is also placed at the bottom. Then, the coordinate values of the alternating magnetic field generator 5 are calculated. The X and y coordinate values obtained from the adder 16a are stored in registers 16b and 16c.

Registers 16b and 16c are respectively
It stores the coordinate values of the axes and the Y-axis. That is, the above-mentioned flip-flop circuit 4af) QIσ output is also transmitted to the registers 16c and 16b, respectively, and when the scanning circuit 3a is operating and scanning the x-axis, the X-coordinate storage register 16b is transmitted, and vice versa. Scanning circuit 3b
When the is operating and scanning the y-axis, the y-coordinate storage register 16c receives the output signal of the adder 16a.
The signal is output through a converter to a display device for display, or sent to a processing device such as a computer. The signal f1 discriminated by the above-mentioned bandpass filter 17 (FIG. 6c)
) is greater than a predetermined level (.) by the level comparator 18, that is, the monostable circuit 19
This signal is transmitted to the alternating magnetic field generator 5 and converted into a signal with a constant pulse width.
It is used as a data acquisition signal for setting coordinate values at arbitrary positions.

That is, in the above description, the frequency at which the alternating magnetic field generator 5 is excited is F. , f, are used (・However, depending on the required signal type, various frequencies such as F2, f3, etc. are superimposed, and band f wave generators, level comparators, Install monostable circuits in parallel.Although not shown,
The frequency excitation for these data acquisition signals is turned on and off at appropriate times by operating a switch built in the alternating current signal source 6 of the alternating magnetic field generator 5. Note that the excitation signal frequency of the alternating magnetic field generator 5 is the frequency of the scanning signal (.
Since it is completely unrelated to the scanning period, the alternating current signal source 6 and the alternating signal generator 5 can be integrated and configured independently from each other, so that they can run wirelessly on the tablet 1. 25 is for the X coordinate and Y among the scanning address signals.
An initial scanning signal liminator that cuts off the first few (minimum 1 to 3) scanning line address signals for each coordinate, and the liminator is connected between the counter output of the counter 15b and the latch register 20. (・ru.

In other words, among the scanning lines laid out on the tablet, when the alternating magnetic field generator is located near the periphery of the tablet, the magnetic flux distribution state is different from when it is located at the center, causing an error in the reading coordinates. Peripheral 1~ depending on accuracy
It is preferable to read the coordinates of several scanning lines (・).Also, as mentioned above, since the maximum value is detected by comparing the output signals of the previous and succeeding scanning lines, One of them cannot read the coordinates (・. Therefore, the above-mentioned Liminator 2
When, for example, 1, 2, and 3 of the scanning address signals from the counter 15b are input to 5, this is treated as invalid and an invalid display signal (for example, 999) is sent to the latch register 20, and the scanning address signals of 4 or more are input. is passed through as is, or subtracted by 3 as necessary and converted so that the origin 0 is the starting point.

Note that errors also occur in the last few scanning lines, but in this embodiment, the set values of the signal selection gate 4b are subtracted by 2 from N and m in advance to obtain n-2.
, m-2. (If the n-2 and m-2 scan lines are not scanned, the n-3 and m-3 scan lines cannot be detected.) The operation of the apparatus of the present invention configured as described above will be explained below. do.

Place the alternating magnetic field generator 5 at any position on the tablet and press one of the switches of the alternating current signal source 6 equipped on the alternating magnetic field generator 5, for example, a point reading switch, and the excitation winding 5a will read the coordinates. signal F.

and point reading signal f1 are added. On the other hand, scanning signals are sequentially applied to the scanning lines X and y alternately in accordance with the scanning address signal from the clock signal generator 15a. is superimposed on this and appears sequentially at the output end A of the tablet, and when the scanning signal is applied to the scanning line closest to the center of the excitation winding 5a, the induced signal at the output end A becomes maximum, and the next closest scanning result is reached. The second largest temperature when a scanning signal is added
- The induced signals are obtained, with the third largest induced signal appearing in the scan line symmetrically to the second and opposite the largest induced signal. Of this induced signal, f1 passes through a band wave generator 17 and a level comparator 18, is transformed by a constant constant circuit, is inputted to a data acquisition signal control circuit (not shown), and is inputted into registers 16b and 16.
Set the device to extract the output of e by one point. F of the guidance signal. passes through the band wave generator 7, AGC circuit 8, etc., and compares the values of the guiding signals of the three scanning lines before and after in the maximum value comparison circuit 12, and scans until the next scanning line from which the maximum guiding signal is obtained. When the maximum value and the next largest value are detected, the maximum value and the next largest value are sent to the division circuit 13,
The divided value is further converted into an inter-scanning line coordinate value by the nonvolatile memory 14, and this is added to the adder 16a. Also, whether the second largest induced signal appeared before or after the largest induced signal, that is, whether the coil center of the alternating magnetic field generator 5 is to the left or right of the scanning line that produced the largest induced voltage. The + and - signs for the inter-scanning line coordinate values of the adder 16a are determined by . On the other hand, the scanning address signal from the clock pulse generation circuit passes through the initial value signal generator liminator 25 and enters the latch register 20 in response to the maximum value detection signal, and the scanning address signal from the previous scanning address signal, that is,
The scan address signal for the scan line that produced the maximum induced signal is sent to the scan line coordinate correction means 22,23.

During X-coordinate scanning, the X-coordinate scanning line correction means 22 is activated by a control signal from the flip-flop 4a, so that the coordinate value of the scanning line that produced the maximum guidance signal from the correction means 22 is corrected for cumulative pitch errors. Adder 1
Added to 6a. The output of the latch register 20 and the output of the non-volatile memory 14 are further coupled to the single pitch error correction means 2.
4, the single pitch error correction means 24 uses this as an address to add and subtract the correction value to the adder 16a, which adds and subtracts these input values to calculate the X coordinate value of the alternating magnetic field generator 5, and outputs the control signal of the flip-flop 4a. This is sent to the X coordinate register 16b which is in the activated state. When the scanning of the X coordinate is completed, the gate 4b operates, resets the counter 15b, inverts the flip-flop 4a, and inputs the Y coordinate value of the alternating magnetic field generator 5 into the register 16c in the same manner as in the case of the X coordinate described above.

In the above embodiment, the cumulative pitch error and single pitch error of the scanning line are corrected for each X coordinate and Y coordinate.
．． It is also possible to use a common Y correction means (・, and the single pitch error is generally relatively small (・ to use only the scanning line coordinate correction means (・).

In addition, the divisor for division that removes errors caused by variations in the thickness of the reading medium is the second largest (the same effect can be obtained by selecting the third or subsequent induced voltages instead of the induced voltage. It goes without saying that they may be placed on the front and back sides of a single tablet.As described above, according to the present invention, the pitch error of the scanning line can be corrected and accurate coordinate reading can be performed. If a non-volatile memory such as a ROM is used as the correction means, the correction can be performed at low cost and with high reliability.

Furthermore, if the maximum value of the guiding signal is divided by a specific signal value close to it and the coordinate position between the scanning lines is determined from the divided value, variations in the thickness of the reading medium on the tablet, and the scanning line Differences in impedance depending on the position of
The effects of variations in the magnetic field strength of the alternating magnetic field generator, deviations in the thickness of the insulating flat plate, etc. are eliminated, and more accurate coordinate reading can be performed regardless of the position of the alternating magnetic field generator and the reading medium.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the relationship between the tablet and the alternating magnetic field generator of the coordinate reading device according to the present invention, FIG. 2 is an explanatory diagram of its main parts, and FIG. 4 is a graph showing the relationship between the position of the alternating magnetic field generator and the induced voltage in each scanning line; FIG. 5 is a program diagram of the coordinate reading device of the present invention; FIG. 6 is a timing chart of the output terminal signal. is a timing chart of key signals in FIG. 5, FIG. 7 is a block diagram of the maximum value detection circuit in FIG. 5, and FIG. 8 is a block diagram of the AGC circuit in FIG. FIG. 9 is a graph showing the relationship between the alternating magnetic field generator position and the division value, and FIG. 10 is a graph showing a function for converting the division value into the inter-scanning line coordinates of the alternating magnetic field generator. 1, 2...tablet, X, y...scanning line, 5...
・Alternating magnetic field generator, 7, 17...Band ▲ wave generator, 11・
・・A/D converter, 12・・Maximum value comparison circuit, 13・
. . . Division circuit, 14 . . . Inter-scanning line coordinate value conversion means (non-volatile memory), 15a . . . Clock signal generator, 2
2...Scanning line coordinate correction means for X coordinate, 23...Y
Scanning line coordinate correction means for the coordinates, 24... single pitch error correction means for the X coordinate, 24/... single pitch error correction means for the Y coordinate.

Claims (1)

[Claims] 1. Scanning signals are sequentially applied to a plurality of scanning lines laid in parallel on a tablet, and a coordinate indicator having an excitation winding that generates an alternating magnetic field is brought close to the scanning lines. The coordinates of the scanning line closest to the coordinate indicator are determined by the scanning address signal when the maximum value of these guidance signals is detected, and the coordinates of the scanning line closest to the coordinate indicator are determined, and the maximum value and any adjacent guidance signal are determined. The inter-scanning line coordinate values of the coordinate indicator from the nearest scanning line are determined from the above, and the coordinates of the coordinate indicator are determined by adding the coordinates of the scanning line and the inter-scanning line coordinate value. In the coordinate reading device, a value corresponding to a scanning address signal is input to an adder via a scanning line coordinate correcting means for compensating pitch error of the scanning line, and the coordinates of the scanning line are corrected. coordinate reading device. 2. The coordinate reading device according to claim 1, wherein the scanning line coordinate correction means comprises a nonvolatile memory. 3. The maximum value of the guidance signal is divided by a specific guidance signal close to it by a division circuit, and this division value is converted into an inter-scanning line coordinate value by an inter-scanning line coordinate conversion means, and is input to an adder. A coordinate reading device according to claim 1 or 2. 4. The coordinate reading device according to claim 3, wherein the inter-scanning line coordinate value conversion means comprises a nonvolatile memory.