JPS6086620A - Electromagnetic induction type coordinate reader - Google Patents

Abstract

PURPOSE:To enhance a coordinate read speed by making the switching speed of a switch higher if a comparison signal is not issued and making this switching speed lower if the comparison signal is issued and reading the induced electromotive force into a microcomputer through an A/D converter. CONSTITUTION:The other ends of every two adjacent conductors of plural conductors 2... whose one ends are connected to one another are connected by a switch 3 such as a multivibrator or the like to form loop coils X1-Xn. An induced electromotive force is generated in each of coils X1-Xn by an exciting coil of a cursor 1; and when one loop coil is selected by the switch 3, the electromotive force generated in this coil is outputted from an amplifier 4 and reaches a microcomputer 7 through a sample holding circuit 5 and an A/D converter 6. If the comparison signal is not issued from a comparator 8, this computer 7 switches the switch 3 in a high wpeed and ignores digital signals from the converter 6. If the comparison signal is issued, the computer 7 operates the switch 3 in a low speed and operates circuits 5 and 6 at a prescribed period to calculate coordinates. Thus, the coordinate read speed is enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electromagnetic induction type coordinate reading device that can improve coordinate reading speed.

As shown in Fig. 1, a conventional electromagnetic induction type coordinate reading device includes a cursor (or pen) 1 equipped with an excitation coil that excites an alternating magnetic field, and two sets of X and Y, in which an electromotive force is induced by this coil. Conductor #2... (Only one set of X and Y conductors is listed in the first section 1) It has a tablet insulated in a perpendicular manner, and the conductor #2... * are sequentially selected from two adjacent ones by a switch 3 such as a multiplexer to form loop coils X1 to Xn. Since an induced electromotive force f15 is generated in each of the nodes XI to Xn by the coil of cursor 1, this electromotive force is transferred to the amplifier 4. After amplification, the peak value of each loop coil X1-Xn detected by the sample and hold circuit 5 is converted into a digital signal by the AD converter 6, and this digital signal is temporarily stored in a memory etc. A computer 7 calculates the position of the coil, that is, the position of the cursor.

This coordinate reading percentage position is for all loop coils X1 to Xn.
Since the induced electromotive force generated in the coordinate system is detected and converted into a digital signal by an AD converter, the coordinate reading speed is affected by the conversion time of the AD converter, which poses a problem in terms of reading speed.

This invention was made in view of the above circumstances, and its purpose is to switch the loop coils at high speed until the induced electromotive force generated in each loop coil exceeds a predetermined value, and detect when the induced electromotive force exceeds the predetermined value. It is an object of the present invention to provide an electromagnetic induction type coordinate reading device that can read coordinates at a high angle by converting the induced electromotive force into a digital signal and performing coordinate reading processing.

The present invention will be described below based on embodiments shown in the accompanying drawings.

As shown in Figure 2, a grounded conductor 2 with one end connected
. . ., the other ends of two adjacent coils are sequentially switched by a switching device 3 such as a multiplexer to form loop coils X1 to Xn. Since an induced electromotive force is generated in each of the loop coils X1 to X by the excitation coil of the cursor 1, when the loop coils XI to Xn are sequentially selected by the switch 3,
The induced electromotive force generated in the loop coils X1 to X is transferred to the amplifier 4.
The signal is output from the microcomputer via the sample and hold circuit 5 and the AD converter 6. Further, the output voltage of the amplifier 4 is determined by a comparator 8 as a reference value.
If the output voltage of the amplifier 4 is greater than the reference voltage, the comparator 8 issues a comparison signal to the microcomputer ladder 1.

The microcomputer 7 switches the switch 3 at high speed and ignores the digital signal from the AD converter 6 if no comparison signal is issued from the comparator B; 3 is operated at low speed, and the sample-and-hold circuit 5 and the AD converter 6 are each operated at a predetermined period, and the induced electromotive force of the selected loop coil is generated through the amplifier 4, the sample-and-hold circuit 5, and the AD converter 6. can be read and the coordinates can be calculated. In addition, since the microcomputer śr stores the loop coil that first emitted the comparison signal from the comparator 8 during the previous measurement, the position of the loop coil that first emitted the comparison signal last time is a predetermined number of times. If switching is performed from the loop coil at the returned position, the loop coil switching time will be shortened and the coordinate reading speed will be improved. That is, if the loop coil that first emitted the comparison signal last time is Xk, this time it is ``-pu''4 k
In case (7), it is necessary to switch from X kz - X 1 ).

In the above embodiment, the comparison signal of the comparator 8 is sent to the microcomputer 7, but a control section is provided to input the comparison signal, and this control section changes the switching speed of the switching device 3, The hold circuit 5 and AD converter 6 may also be activated. Further, the sample and hold circuit 5 and the AD converter 6 may be always operated at a constant cycle, and the amplifier 4 may be omitted if the magnitude of the starting force does not pose a problem in the reading process. Furthermore, in the above embodiment, an AC voltage was applied to the coil of cursor 1, but a predetermined AC voltage may be applied to the loop coils X1-Xn, and the electromotive force induced in the coil of cursor 1 is detected. You may also do so.

As described above, the switching speed of the loop coil is set to high speed until the detected induced electromotive force exceeds a reference value, and when the detected induced electromotive force exceeds the reference value, the switching speed of the loop coil is set to low speed. Since the electromotive force is read into the microcomputer via the AD converter and the coordinates are read, the comparison signal is not emitted from the comparator.J!
There is an advantage that the switching speed of the 1-coupled loop coil is improved, and the coordinate reading speed is also improved in practical terms.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a conventional example, and Fig. 21! ! ! , l is a block diagram showing an example of the present invention.

Claims (1)

[Claims] 11) A coil provided on the cursor or pen and a plurality of loop coils provided on the tablet, generating an alternating magnetic field in either the coil or the loop coil, and switching the loop coil. In a device that reads coordinates by sequentially selecting an electromotive force induced in the other by reading it into a microcomputer via an AD converter, the device includes a comparator that issues a comparison signal when the electromotive force exceeds a reference value, and a comparator that issues a comparison signal when the electromotive force exceeds a reference value. If the signal is not being emitted, increase the switching speed of the switch,
An electromagnetic induction type coordinate reading device comprising a control section that reduces the switching speed of a switching device if a comparison signal is issued, and causes a microcomputer to read the electromotive force induced in the other via an AD converter. (2) The electromagnetic induction type coordinate reading device according to claim 1, wherein the control section is a microcomputer. (3) The microcomputer controls the switching device so that the switching is performed from the loop coil position that has returned to a predetermined position from the position of the loop coil where the comparison signal was first emitted from the comparator when measuring 1liJ times. An electromagnetic induction type coordinate reading device according to claim 2.