JPS59105183A - Coordinate reading device - Google Patents

Abstract

PURPOSE:To eliminate electrostatically induced malfunction in coordinate reading due to a stray capacity generated by the hand, by performing comparative subtraction at an arithmetic control section. CONSTITUTION:Scanning circuits 3X and 3Y scan each sense line Xn and Ym. A coordinate indicator 4 has a coil 5 while generates induction signals to the sense lines Xn and Ym. An amplifying filter circuit 7 applies waveform processing to an induction signal (l) from the sense lines Xn and Ym. An AD converter 8 performs AD conversion on a signal from the amplifying filter circuit 7. In short, the scanning circuits 3X and 3Y, amplifying filter circuit 7, and AD converter 8 constitute a scanning and detecting circuit. An arithmetic control section 9 operates the position of the coordinate indicator 4 by using a signal from the AD converter and, at the same time, controls the other external inputs and outputs.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a coordinate reading device, and more particularly, to a coordinate reading device that eliminates malfunctions in obtaining coordinates He from V by adding a subtracter section to an arithmetic control section.

Conventionally, when using a coordinate reading device for mounting, a hand H holding a coordinate indicator 4 is placed on a cover 2α made of an insulating material on a substrate 2 having a sense line
I have to put it on. At this time, stray capacitances C81 and C8□ are formed between the excitation coil 5 and the hand H, and between the hand H and the sense line Xn (Ym). Then, the potential of the stray capacitance cB oscillates due to the electromagnetic waves generated by the alternating magnetic field φ from the coil 5, and this potential oscillation causes the stray capacitance 082f! : is electrostatically coupled to the sense mXncYm). Therefore, sense gX
n(Ym) generates an electromotive force due to electrostatic induction from the hand H even though the coordinate indicator 4 is not near the tablet.

When this state is viewed in terms of the amplified F wave and NFC scanning waveform, it becomes as shown in FIG. 2, and the level of the scanning waveform increases by 70 minutes of the electromotive force due to electrostatic induction. A normal waveform is shown in FIG. 3, and the peak voltage Vp is about 6V, and vth is set to about 1°5. In contrast, the electrostatic induced voltage (■) in Figure 2. can reach up to 2v. Figure 4 shows the peak voltage Vp
The operation of the calculation control unit of the hansoku is shown in a flowchart. In the conventional calculation, as shown in FIG. 4, when the maximum value VfiAX of the voltage induced in the sense line exceeds the threshold voltage th, it is immediately determined to be the peak voltage Vp. Therefore, the voltage that is not detected in the normal state exceeds the threshold 'E voltage Vthf due to electrostatic induction, and when the arithmetic and control unit scans in FIG. The disadvantage was that the position was calculated and accurate coordinate reading was not possible.

The invention was made in order to promptly eliminate the above-mentioned drawbacks, and by performing comparison and subtraction in the arithmetic control section, it is possible to eliminate coordinate reading errors due to electrostatic induction caused by stray capacitance caused by hands. It is a reading device.

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

The non-standard mark reading device has a 1:1.7 configuration as shown in FIG. That is, 1 is a tablet, the sense line Xn,
It consists of an insulating plate 2 having Ym.

3x, 3y are scanning circuits for scanning each sense line Xn, Ymi, 4 is a coordinate indicator, and this indicator 4 is connected to a coil 5 for generating an induction signal to the sense lines x'yt, Ym.
It has at the tip. 6 is about 3 to the excitation circuit coil 5
\\Give KH2 excitation signal. 7 is the sense line Xn, Y
Amplifying p-wave circuits 7 and 8 for waveform processing the induced signal t from m
is A for A/D converting the signal from the amplifying p-wave circuit 7.
/D converter. The scanning circuits 3X and 3Y, the amplification/filtering circuit 7, and the A/D converter 8 constitute a scanning detection circuit.

9 is an arithmetic control unit, which includes a data memory and a CPU;
/ The signal from the D converter 8 calculates the 40th position of the coordinate indicator and controls all other external inputs and outputs. 1\ is an interface circuit with external equipment. Furthermore, if the entire flowchart of the peak determination operation of the detection signal obtained from the A/D converter of the arithmetic and control section is developed and described, the flowchart will be the same as shown in FIG. That is, A is a detection unit for detecting the maximum value VmAX and minimum value Vmin of the detection signal, and B detects a voltage difference △v6 between the maximum value VmAX and minimum value Vmin, and the threshold value △■τe, This is a comparison section with f. Calculation of part B by part A △V = VyLAz −V m1tL△V〉△Vre
f is made possible, and it is determined by this calculation whether or not the peak voltage is due to electrostatic induction.

According to experiments, the voltage difference △ due to electrostatic induction in Figure 2
■α is approximately ＼. It is about 2v. With respect to this nVC, the voltage difference △Vb due to the electromagnetic contact I of the actual coordinate indicator in Fig. 3 is
is as fake as the minimum IV. However, by setting the threshold value △Vref\, 5■, it is possible to eliminate the malfunction of the coordinate reading of the coordinate reading device due to the static visit by the embodiment shown in FIG.

As described above, according to the invention, the malfunction of coordinate reading, which is a basic function in a coordinate reading device, can be eliminated by adding a small step, and the reliability is significantly improved compared to the conventional device. Has a soothing effect

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing electrostatic induction in a conventional coordinate reading device, Fig. 2 is a scanning waveform diagram due to electrostatic induction, Fig. 3 is a normal Atsushita diagram, and Fig. 4 (α). (b) is a conventional beak judgment flowchart of a detection signal, FIG. 5 is a configuration diagram of a coordinate reading device, and FIG. 6(α) is a beak publication 5E flowchart showing an embodiment of the invention be. 1°. Taplet l-2°, insulating substrate 2α,. Cover 3x, 3y. scanning circuit
4°. Coordinate indicator 5. . Coil 6°. Exciting circuit
7°. Ruiba p-wave circuit 8...A,/D converter 9
0. Arithmetic control unit 1\1. Interface circuit and above Applicant Daini Sayakosha Co., Ltd. No. 1 (21 Fig. 2 Fig. 3F No. 4-Exit (sub) Layer 4 (1,) Question 6 (a) Fig. 6 (1,)

Claims (1)

[Claims] A tablet comprising a large number of sense wires laid at regular intervals; a coordinate indicator having a coil for instructing the tablet to a position CN k; an excitation circuit for generating an alternating magnetic field in the coil; In a coordinate reading device comprising a scanning detection circuit that sequentially scans and detects generated guidance signals, and an arithmetic control section that calculates the position of the coordinate indicator based on the detection signal, the arithmetic control section detects the detection signal; ＋iii Tablet and coordinate indicator and part 2''
Compare and subtract the noise signal due to the stray capacitance that exists between the hand of the person holding L, and use the signal above a certain value as the detection signal,
An indecent mark reading device characterized in that coordinate reading V is performed while distinguishing it from noise signals.