JPS63136123A - Coordinate detector - Google Patents

Abstract

PURPOSE:To detect the accurate coordinate value despite a phase shift by detecting the corrected value proportional to the phase shift of a filter and correcting the detected coordinate value based on the corrected value. CONSTITUTION:A data processing circuit 11 switches a switch 10 and a clock signal (c) is inputted to a counter 8 via a filter 6 and a comparator 7. At the same time, another clock signal (c) is also supplied to the counter 8. Thus the signal (c) passed through the filter 6 is compared with the signal (c) passed through no filter 6. If the filter 6 has a phase shift, the number of output pulses sent from the counter 8 is proportional to the degree of the phase shift of the filter 6 and supplied to the circuit 11. Thus the number of the pulses is stored temporarily as the corrected value. Then the circuit 11 changes the switch 10 to a side where the waveform signals received from a waveform processing circuit 5 are selected to detect the XY coordinates. This detected XY coordinate value is corrected by the obtained corrected value.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a coordinate detection device using an electromagnetic drive method.

[Conventional technology]

There are various types of coordinate detection devices using an electromagnetic drive method. Among these, a coordinate detection device that is commonly used will be explained with reference to the drawings.

FIG. 3 is a block diagram of a conventional coordinate detection device. In the figure, 1 is a tablet, 2 is a magnetic field generating device such as an electromagnetic pen or cursor (hereinafter referred to as an electromagnetic pen), and 3 is a pen drive circuit for causing the electromagnetic pen 2 to generate a magnetic field.

The tablet 1 is wired with an X-axis circumference detection lead wire and a Y-axis detection lead wire for detecting the coordinates of the electromagnetic pen/2 on the tablet 1. Bene/drive circuit 3#'i is driven by a clock signal C from a clock generator (not shown), and supplies a sine wave current to the electromagnetic drive circuit 2 in synchronization with the clock signal C. The electromagnetic lever 2 generates a magnetic field in response to this, and a sinusoidal voltage corresponding to the position of the electromagnetic lever 2 is generated in each detection conductor of the tablet l.

4 is a waveform detection circuit, which is composed of a waveform processing circuit 5 and a filter 6. The waveform processing circuit 5 is a tablet l.
The sine wave voltage of each detection conductor is input, and a sine wave signal whose phase is shifted according to the magnitude of the voltage is output. The filter 6 is provided to remove noise mixed in from inside and outside the coordinate detection device, and is composed of a capacitor and a resistor. A comparator 7 converts the sine wave signal from the filter 6 into pulses corresponding to the sine wave signal.

8 is the ii of the clock signal C and the output signal from the comparator 7.
This is a counter that detects the phase difference of j and outputs a corresponding number of pulses. Reference numeral 9 denotes a data processing circuit composed of a microcomputer, which performs all necessary calculations and controls based on the output pulses of the counter 8, and calculates the coordinates of the output bench 2.

Since a coordinate detection device having such a configuration is already known,
A more detailed explanation will be omitted.

[Problem that the invention seeks to solve]

In the coordinate detection device described above, since the waveform detection circuit 4 is provided with the filter 6, the influence of noise is removed and accurate coordinate values can be detected. However, the filter 6 must prevent the phase shift 11 from occurring in the output signal of the waveform processing circuit 5 by itself. For this reason, the filter 6 has many restrictions, such as the need to use highly accurate capacitors and resistors that do not change much with respect to such changes. In particular, it is naturally effective to use a filter whose resonant circuit has a sharp kurtosis Q for noise removal, but it is difficult to use such a filter in the conventional coordinate detection device described above. The reason:
This will be explained using FIGS. 4(a) and 4(b)'e.

FIGS. 4(a) and 4(b) are frequency characteristic diagrams of the filter, with the horizontal axis in each figure representing frequency, and the vertical axis representing signal level and phase. The solid line curve in the figure shows the frequency characteristics of the filter at a certain temperature, and as shown in Figure 4 (a), if the sharpness KQ is sharp, the 1-magic signal that slightly deviates from the resonant frequency will be cut. Therefore, noise is sufficiently removed. Here, when the temperature changes from the above-determined temperature, the frequency characteristics of the filter change as shown by the broken line in the figure. Due to such fluctuations, the phase of the signal passing through the filter changes by a value Δθ, as shown in FIG. 4(b). This phase change Δθ is large even for a slight change in frequency characteristics, so a filter with a sharp sharpness Q cannot be used, and as a result, noise removal cannot be performed ideally. was occurring.

SUMMARY OF THE INVENTION An object of the present invention is to provide a coordinate detection device that solves the above-mentioned problems of the prior art and allows a filter to be arbitrarily configured without considering phase shifts.

[Means for solving problems]

In order to achieve the above object, the present invention includes a magnetic field generating device such as an electromagnetic pen or cursor that is driven by a drive signal of a predetermined frequency, and a plurality of detection leads that output signals according to the position of the magnetic field generating device. , a waveform processing circuit that processes the waveform of the output signal from these detection conductors, a filter, and a phase difference detection means that detects a phase difference between the waveform signal from the waveform processing circuit that has passed through the filter and the drive signal. In the coordinate detection device equipped with data processing means for processing the output signal of the phase difference detection means, the waveform signal from the waveform processing circuit and the drive signal for driving the magnetic field generation device are selected and applied to the filter. An input signal switching means, when the drive signal is input to the filter by the signal switching means, a correction value detection means for obtaining a correction value based on the output signal of the phase difference detection means, and a signal switching means, the waveform signal is The present invention is characterized by comprising a correction means for correcting the output signal of the phase difference detection means with the correction value obtained by the correction value detection means when input to the filter.

[For production]

During coordinate detection operation, when the signal switching means selects a drive signal of a predetermined frequency, this drive signal is input to the phase difference detection means through a filter, and the phase is compared with the drive signal directly input to this phase difference detection means. A signal corresponding to the phase difference between them is output from the phase difference detection means. Correction 1 [The detection means calculates a correction value based on the signal from the phase difference detection means.

This correction value is O when no phase shift occurs in the filter, and is proportional to (direct) when a phase shift occurs due to temperature change, etc. Next,
When the signal switching means selects a waveform signal from the waveform processing circuit, this waveform signal is inputted to the phase difference detection means through a filter, and the phase difference between it and the drive signal is detected.

This detected phase difference is corrected by the above-mentioned correction value by the correction means, and is output as an accurate sitting image.

〔Example〕

Hereinafter, the present invention will be explained based on illustrated embodiments.

FIG. 1 is a block diagram of a coordinate detection device according to an embodiment of the present invention. In the figure, parts that are the same as those shown in FIG. 3 are given the same reference numerals, and explanations thereof will be omitted. Reference numeral 10 denotes a switch that selectively switches between the waveform signal output from the waveform processing circuit 5 and the clock signal C.

This switch 1O is provided before the filter 6, so that even when either the waveform signal or the clock signal C is selected, the signal passes through the entire filter 6. 11 is shown in FIG. This data processing circuit corresponds to the data processing circuit 9 shown in FIG. 9, and its calculation and control means include a correction value detection means for obtaining a correction value fr, and a correction value for correcting the detected coordinate value using the obtained correction value. means, and the switching device 10 at 1tLI.
J# means is added.

Next, the operation of this embodiment is shown in the flowchart shown in FIG.
This will be explained with reference to. First, in this coordinate detection device, whether the filter 6 is in a state where a phase shift occurs or not, and if it is in a state where a phase shift is caused, what is the correction value for correcting the coordinate detection value according to the magnitude of the phase shift? Correction value detection is performed to detect whether the value is correct (step S1 shown in FIG. 2). This correction value detection is performed as follows. Already
The data processing circuit 11 outputs a signal to the switch lO to switch the switch lO to the side that selects the clock signal C. As a result, the clock signal C passes through the filter 6 and the comparator 7 and is inputted to the counter 8 by 8tL.

On the other hand, a clock signal C is simultaneously input to the counter 8, and the clock signal C that has passed through the filter 6 and the clock signal C that has not passed through the filter 6 are compared in this counter 8. As a result of this comparison, if there is no phase shift in the filter 6, the output pulse from the counter 8 is 0.
In addition, if there is a phase shift in the filter 6, the number of output pulses from the color/receiver 8 will be proportional to the magnitude of the phase shift. This number of output pulses is input to the data processing circuit, and the value is temporarily stored as a correction value.

Next, the data processing circuit 11 switches the switch 10 to the side that selects the waveform signal from the waveform processing circuit 5, and as a result, XYP four target detection is performed by the same means as in the conventional method (step 1).
@Sz). Next, the detected XY coordinate values are corrected using the correction values obtained in step S1 described above (step Ss), and the corrected values are output as XY coordinate values (step S4).
). In detecting the next XY coordinate value, +l1kI again
iSx-S4 is repeated.

In this way, in this embodiment, the phase shift in the coordinate detection device filter is detected, and based on this, a correction value proportional to the phase shift is determined, and the detected coordinate value is corrected using this correction value. Therefore, accurate coordinate values can be obtained regardless of whether or not there is a phase shift in the filter.

From this, it is possible to select a filter with a sharpness Q, which enables effective noise removal and highly accurate and reliable coordinate detection. Furthermore, since there is no need to consider the temperature characteristics of resistors, capacitors, etc., there is no need to use expensive resistors, capacitors, etc., and the cost of the device can be reduced.

Also, if you understand the temperature characteristics of the filter, you can determine the temperature by detecting the phase difference, and based on this, you can consider temperature compensation for other parts and equipment. can.

In addition, in the description of the above embodiment, an example was explained in which a correction value is detected every time coordinates are detected, but correction value detection can also be performed every several times.

〔Effect of the invention〕

As described above, in the present invention, a correction value proportional to the phase shift of the filter is detected, and the detected coordinate values are corrected using this correction value, so even if there is a phase shift, accurate coordinate values can be obtained. can be detected. Therefore, it is possible to configure a filter arbitrarily without considering phase shift, and as a result, effective noise removal is performed using a sharp filter with sharpness Q, further improving the accuracy and reliability of coordinate detection. can be improved. Furthermore, since there is no need to use expensive resistors, capacitors, etc. that have severe temperature characteristics, the cost of the device can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a 10-step diagram of a coordinate detection device according to an embodiment of the present invention, FIG. 2 is a flowchart explaining the operation of the device shown in FIG. 1, and FIG. 3 is a block diagram of a conventional coordinate detection device.
FIGS. 4(&) and 4(b) are frequency characteristic diagrams of the filter. 1...Tablet, 2...Electromagnetic Hen, 3.
... Hendrive circuit, 5... Waveform processing circuit,
6... Filter, 7... Comparator, 8...
-Counter, 10...Switcher, 11...Data processing circuit. (Representative Patent Attorney Masaru Ogawa

Claims (1)

[Claims] A magnetic field generator driven by a drive signal of a predetermined frequency, a plurality of detection leads that output signals according to the position of the magnetic field generator, and a waveform processing circuit that processes the waveforms of output signals from these detection leads, A filter, a phase difference detection means for detecting a phase difference between a waveform signal from the waveform processing circuit that has passed through the filter and the drive signal, and a data processing means for processing an output signal of the phase difference detection means. In the coordinate detection device, the signal switching means selectively inputs the waveform signal and the drive signal to the filter, and when the drive signal is selected by the signal switching means, the signal switching means selects the drive signal based on the output signal of the phase difference detection means. A coordinate system characterized by comprising a correction value detection means for obtaining a correction value, and a correction means for correcting an output signal of the phase difference detection means with the correction value when the waveform signal is selected by the signal switching means. Detection device.