JPS5816506B2 - coordinate reading device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is an improvement of a coordinate reading device that generates an alternating magnetic field from a coordinate indicator and detects a guiding signal induced in a sense line laid on a tablet to determine the position of the coordinate indicator. Regarding 1. More specifically, the present invention relates to a coordinate reading device that uses a secondary peak value of a guidance signal to correct calculation errors caused by the tilt of a coordinate indicator.

Conventionally, a coordinate indicator that generates an alternating magnetic field is placed close to a plurality of sense lines provided at equal intervals on a tablet, and the maximum value of the induced signal from the sense line group and the sense line that generated this maximum value are measured. There are coordinate reading devices that calculate the position of the coordinate indicator using the ratio of the difference between the guidance signals from the sense lines on both sides, but with the above configuration, if the pen-shaped coordinate indicator is tilted, the calculated position and the actual There was a drawback that the indicated position was different from the indicated position.

The present invention has been made to eliminate the above-mentioned drawbacks, and uses the secondary peaks existing on both sides of the primary peak of the induced signal from the sense line group to cancel the error in the calculated position due to the tilt of the coordinate indicator. It is an object of the present invention to provide a coordinate reading device with high accuracy by providing such calculation means and eliminating the difference between the actual indicated position and the calculated position.

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

FIG. 1 shows a block diagram of an embodiment of the present invention, and the content of the arithmetic control section 16 is the feature of the present invention.

The tablet 1 has an X-axis sense line X1. X2. X3. ......, Xn and the Y-axis sense line provided on the back side of the insulating substrate 2 ¥1. ￥2
．． Y3゜..., Ym.

The X-axis scanning circuit 3X and the Y-axis scanning circuit 3Y, each consisting of a decoder, perform a switching operation for each sense line together with a diode D connected to each sense line.

And the scanning circuits 3X and 3Y are X1→Y1→X2→Y2
...→Xn-+Yn The induction signals of each sense line are outputted to the common output line l in the following order.

An excitation winding 5 is attached to the tip of the pen-shaped coordinate indicator 4, and the output signal from the crystal oscillator 6 via the amplifier 7 generates a constant frequency f.

The structure is such that it generates an alternating magnetic field.

In addition, the pen switch 8 indicates that if the pen pressure exceeds a certain level, the coordinate indicator 4
It closes when it joins.

The Y-axis and Y-axis induced signals pass through the output line l, the amplifier 9, the band P wave device 10, the amplifier 11, the rectifier circuit 12, the low band P wave device 13, the amplifier 14, and the A/D converter 15. It is input to the calculation control section 16.

The arithmetic control unit 16 includes a microprocessor 17 and a memory 18.
, interfaces 19 and 20, and a scanning circuit 3X via a scanning address register 21.

3Y, and is configured to send a calculated coordinate signal to an external device 22 in accordance with an output signal from a pen switch 8 within the coordinate indicator 4.

The basic operations of the above-mentioned parts are as disclosed in Japanese Patent Application No. 51-13594 and Japanese Patent Application No. 5'4-5256.

That is, in terms of procedure, when the induced signal exceeds the noise level, that value is stored in the memory 18 as a temporary maximum value,
If the next sense line signal is thicker than the level detected immediately before, that value is rewritten as a temporary maximum value, and the previous value is stored in the memory 18 as the adjacent signal.

This process is repeated in sequence, and several sense lines before and after the maximum value signal are stored in the memory 18 with respect to the Y-axis and the Y-axis, respectively.

The level of the induced signal stored at this time is displayed as shown in Figure 2.As is clear from Figure 2, the secondary peak exists within several lines before and after the maximum value signal, so it is certain that the pair of It is stored in the secondary peak memory 18.

Next, a value Q corresponding to the coordinate position between the sense lines of the coordinate indicator 4 is calculated. In the present invention, the secondary peaks are compared and the difference is multiplied by α (0<α<1). The corrected amount is calculated as a β value that is added to the Q value.

In FIG. 2, since the guidance signals alternate between the Y-axis and the Y-axis as described above, only the shaded portion shows the signal from the Y-axis, and the others show the signals from the Y-axis.

Considering only the Y-axis, Vpx is the maximum signal value p
X P+IX is the value on both sides thereof, and ■ −1, ■ V−pX, and V+pX are the secondary peak values, respectively.

Here, the reason why the secondary peak occurs will be explained.

Figure 3 shows the magnetic flux φ generated from the excitation winding 5 of the coordinate indicator 4.
FIG. 2 is an explanatory diagram showing a state in which a sense line passes through a substrate 2 provided with a sense line.

Assuming that the X-axis sense line is placed in the vertical direction of the drawing, the Px part is the part that generates the maximum signal Vpx, and -P
x, 10Px is the secondary peak value V V+- on both sides
This is the part that generates 1 door.

In other words, the secondary peak is generated by the folding of the magnetic flux φ.

Now, if the pen-shaped coordinate indicator 4 is tilted by θ as shown in Fig. 3, there is a variation between the sense lines at the tip pointing position of the coordinate indicator 4, as disclosed in Japanese Patent Application No. 54-5256. The corresponding calculation value Q is V, +1X>V, when , -4-1x<v, , when X, the CPU
17.

However, as is clear from FIG. 2, v, +1x increases and Vp-1X decreases depending on the inclination angle of the coordinate indicator 4, so this calculated value Q decreases and the actual value of the coordinate indicator 4 increases. The value corresponds to the coordinate position D' shifted by ΔD from the indicated position.

However, in the present invention, attention is paid to the fact that the secondary peak value also increases or decreases depending on the inclination angle θ of the coordinate indicator 4, and an attempt is made to offset the reading error such as the above-mentioned ΔD.

Considering the case where the coordinate indicator 4 is located between the T points of adjacent sense lines, when θ-〇, V-2 V+O,
When tilted as shown in Figure 3, V gradually becomes <V+7 as shown in Figure 2, c, d, and e.

The maximum value Vpx stored in the memory 18 as described above,
■ -1X, ■ detected from the sense lines on both sides
+1x, secondary peak value v px, pp V+, the following calculation is performed.

That is, when the indicator 4 is tilted as shown in Figure 3, if the tilt is less than 45 degrees, then V, +, X>V, and V
+ >V, and p x p
Find the value of β as x −′−px.

The above equation clearly shows that it compensates for the increase in V + caused by the slope and the ~1x (7) decrease lX.

This is because the V, +1x value is detected larger in Figure 2 d than in Figure 2 a, but the amount subtracted too much from Vpx in the numerator is added by the correction amount, and the V that was not subtracted in the denominator This is because the -1x value is subtracted by the correction amount.

According to experiments, it has been found that the optimum correction value is when α in the above equation is 1/4.

This is because, as shown in Table 1, increasing α will reduce the reading deviation due to one slope, but since the secondary peak values are both low-level signals, the amount of fluctuation due to noise will have a large effect on the α value. This would further increase the amount of fluctuation, resulting in poor accuracy and increased variation in measured values.

Furthermore, division by 2n requires only a digit shift, and the algorithm is simple and has the advantage of high calculation speed.

Next, as shown in Table 2, α- The actual measured values are shown when the coordinates are calculated at 1/4.

From the coordinate position correspondence calculation value β calculated as described above, with the tilt correction of the coordinate indicator 4 added, the relationship between this calculation value β and the coordinate values between the sense lines was experimentally determined in advance. Conversion function (Japanese Patent Application 1983-13594, Japanese Patent Publication 1987-31
188)), find the coordinate values between the sense lines,
Further, from this value and the height of the sense line where the maximum value was detected, the coordinate value indicated by the coordinate indicator 4 is determined and output to the external device 22.

As described above, according to the present invention, the reading bed detects the secondary peak of the electromagnetic induction signal due to the sense line on the tablet and when the pen-shaped coordinate indicator is tilted.

Since it is configured to correct the amount of deviation in the target position, even if the coordinate indicator is tilted in a natural state and pressed against the tablet, there is not much reading error, and furthermore, the correction coefficient α has been reduced to approximately 1/4. This has the great effect of maintaining accuracy.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a scanning output waveform diagram. Regarding the inclination θ of the coordinate indicator, a is θ-00, b is θ-10°, and C is θ -20°, d
is θ-30°, and e is θ-45°i.
The figure shows the state of magnetic flux penetrating the tablet, where a shows the coordinate indicator perpendicular to the tablet and b shows the state where it is tilted by θ. 1-----Tablet, Xl, X2.・・・・・・
, Yl, Y2...Sense line, 3X, 3Y...
...Scanning circuit, 4...F coordinate indicator, ■...
... Output line, 10... Band r wave device, 13.
・°・°・Low frequency P wave device, 15...A/D converter, 16...P calculation control unit (calculation means), 17...
...Microprocessor (CPU), 21...
・Address register.

Claims (1)

[Claims] 1. A tablet formed by laying a large number of sense lines at regular intervals, a coordinate indicator equipped with a coil for indicating coordinates on the tablet, and means for generating an alternating magnetic field in the coil. a coordinate reading device comprising means for sequentially scanning and detecting guidance signals generated on the sense line; and calculation means for calculating the position of the coordinate indicator based on the detection signals, the calculation means detecting the guidance signals. comprising a secondary peak detecting means for detecting secondary peak values occurring on both sides of the maximum value signal and a correction amount calculating means for calculating a correction amount by comparing the secondary peak values, A coordinate reading device characterized in that it is configured to correct errors. 2. The coordinate reading device according to claim 1, wherein the correction amount calculation means is a correction amount calculation means that performs the following calculation, provided that Vp: the maximum induced signal value generated on the sense line ■ -1 and V +t:
Induction signal values generated on the sense lines before and after the sense line that generated Vp, V+: Secondary peak induction signal value appearing on the tilt side of the coordinate indicator -: Secondary peak appearing opposite to the inclination of the coordinate indicator Induction signal value α: Constant determined experimentally.