JPS59142684A - Electromagnetic induction type digitizer - Google Patents

Abstract

PURPOSE:To reduce the detection error of coordinates for the inclination of an electromagnetic pen, by using a magnetic core in the electromagnetic pen. CONSTITUTION:The tip part 17 of a magnetic core 16 has a curved surface of a curvature radius R. When a current is flowed to a pen coil 9, the magnetic core 16 is excited, and a magnetic flux is generated from a part near the tip part 17. That is, the magnetic flux is generated near a contacting part 18 between the surface 12 of a digitizer and the electromagnetic pen, and consequently, the deviation between an entered character and a pattern and a character and a pattern monitored on a display is reduced independently of the inclination angle theta of a pen 30 to make the input easy.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electromagnetic induction digitizer in which the deviation of detected coordinates does not increase even if the electromagnetic pen is tilted.

FIG. 1 is a circuit diagram showing an example of an input panel and an electromagnetic pen of a conventional electromagnetic induction digitizer. In this figure, 1 and 2
is a group of sense fills formed using parallel conductors, arranged at a constant pitch and having one turn, respectively.
...11. l m sense coils and 2se z
, 2s, i+, 2q...4n sense coils.

One end of each sense coil 11-IIrI+21-2n is grounded, and the other end is connected to the amplifier 5 via each switch of the switch group 3.4. Switch groups 3 and 4 are 31132+ 33+..., 3p...'3m and '1*4N+ 4as..., 4. ... Consists of 47 m and n switches (p+
me q#n is a positive integer). Each switch 31 to 3□ of switch groups 3 and 4, 4. ~4n are each decoder 6
．． They are closed one by one by the signal from 7. 8 is an electromagnetic pen having a pen coil 9 near its tip. The pen coil 9 is excited by an oscillator 10 connected thereto and generates an alternating magnetic field.

Connect the tip of the electromagnetic pen 8 to the sense coil 1p, 2. The magnetic flux of the pen filter 9 interlinks with the sense coils 1p and 2q and the nearby sense coils, and the sense coil '1l1
A voltage is induced in 2Q and the sense coil in its vicinity. The induced voltage of the sense coil is applied to the amplifier 5 when the switch connected to each sense coil is closed, and is transmitted to the signal processing circuit 11. The voltage transmitted to the signal processing circuit 11 becomes maximum when the switch connected to the sense coil on which the tip of the electromagnetic pen 8 is placed is closed. That is, sense coil 1.12. The induced voltage of is maximum.

The signal processing circuit 11 scans each switch of the switch groups 3 and 4 and detects the induced voltage of the sense coil and its maximum value. Therefore, which sense coil the tip of the electromagnetic pen 8 is on is identified from the signal sent to the decoder 6.7 when the maximum voltage is detected.

The detailed coordinate X of the tip of the Tt electromagnetic pen in the sense coil can be determined from the induced voltage of the sense coil where the tip of the electromagnetic pen 8 is placed and the adjacent sense coil. The tip of the electromagnetic pen 8 is the sense coil 1. When it is on top, there is 1 sense coil.

The induced voltage of 'fl#'111+1 is Vp-H, respectively.
Vp*Vp+1, V is the maximum among all the sense coils in sense coil group 1. The coordinate X is determined based on the following formula.

V(xl= (V, Vfl-1)/(VpVp+
1 ) (vp-t (when v, +) vll"'l l vll 1 v in equation (1)
p+t may be the corresponding output voltage of the amplifier 5.

Since there is a certain relationship between the coordinates When the above ROM is accessed using the calculation result as an address signal, V
The coordinate X corresponding to (x) is determined.

The y-coordinate of the tip of the electromagnetic pen 8 is similarly determined from the induced voltage of the sense fill group 2.

When determining the coordinates of the tip of the electromagnetic pen 8 using the above digitizer, the error is small when the electromagnetic pen 8 is not tilted, but the error is large when it is tilted. 3 is a diagram showing an electromagnetic pen 8. FIG. In this figure, 12 is the surface of the input panel of the digitizer, with which the tip of the electromagnetic pen 8 is in contact. A position 13 where the tip of the electromagnetic pen 8 is in contact with the surface 12 is a pen coil 9
It is shifted by a distance d from the position 14 of the tip of. The magnitude of the distance d is d=hslnθ, where θ is the inclination of the electromagnetic pen 8 and h is the distance between the tip of the pen coil 9 and the tip of the electromagnetic pen 8.

For example, when h=lom+θ=45°, d=7.0
7m + roar. Since the electromagnetic induction digitizer detects the position of the magnetic flux generating part, if the position of the pen coil 9, which is the magnetic flux generating part, shifts, the detected coordinates will shift and d
When =7.0711f+11, the error is also several ■.

Considering that the error when θ=06 is about ±0.2 degrees or less, this error is abnormally large. When holding the electromagnetic pen 8 in your hand, it is inevitable that it will tilt, so the conventional electromagnetic pen 8
When inputting handwritten characters and figures using an electromagnetic induction digitizer using an electromagnetic induction digitizer, the inevitable disadvantage is that the error between the written position and the input position becomes extremely large.

This invention was made to eliminate the above-mentioned drawbacks, and by using a magnetic core in an electromagnetic pen, the errors caused when the electromagnetic pen is tilted are significantly reduced. The present invention will be described in detail below based on the drawings.

FIG. 3 is a cross-sectional view of a portion of the electromagnetic pen used in the electromagnetic induction digitizer of the present invention.

This invention can be constructed from the input panel shown in FIG. 1 and the electromagnetic pen 30 shown in FIG. 15 is a housing of the electromagnetic pen 30;
1B is a magnetic core made of ferrite or the like. The tip 17 of the magnetic core 16 is a curved surface with a radius of curvature of about 1. When a current is passed through the pen fill 9, the magnetic tube 716 is excited, and a magnetic flux is generated near the tip 1T. That is, since magnetic flux is generated near the contact portion 18 between the surface 12 of the digitizer and the electromagnetic pen 30, regardless of the value of the tilt angle θ of the electromagnetic pen 30,
Only a deviation of 5 as the distance d in FIG. 2 occurs.

Therefore, even if the electromagnetic pen 30 is held by hand, the error caused by the tilt is extremely small. According to actual measurements, the error when θ=400 determined based on equation (1) was 0.2 to 0.3, although it varied somewhat depending on the coordinates and height of the electromagnetic pen 30. . An error of this magnitude is such that it hardly causes any practical problems. The reason why this error occurs is that when the electromagnetic pen 30 is tilted, there is a difference in the distribution of magnetic flux between the tilted side and the opposite side, and the magnitude of the above-mentioned Vp-1 #Vp+1 is θ=θ°
This is because it is different from when . The direction of shift is electromagnetic pen 30
This is the side that is tilted.

In Figure 3, the tip 17 of the magnetic core 16 and the center line 19
If the position of the intersection is 20, then the position 20 and the contact part 1B
The difference a is a=几s1nθ. That is, the contact portion 1B where the electromagnetic pen 30 actually contacts the digitizer is shifted by 1 (sino) from the position 20 of the tip of the electromagnetic pen 30 toward the side where the electromagnetic pen 30 is inclined.
If the error caused by the deviation of -@@Vp+l from the value when θ=06 is D, the error can be canceled by adjusting the value of the radius of curvature R. Specifically, D
=RsLnθ.几” 0.3 wa, when θ=40°, fLsInθ≧0.2−,
Errors in the detection position when the electromagnetic pen 30 is tilted can be almost canceled out.

FIG. 4 is a circuit diagram showing an example of an input panel for another electromagnetic induction digitizer according to the present invention. This invention can also be constructed by the electromagnetic pen 30 shown in FIG. 3 and the input panel K shown in FIG.

In FIG. 4, 21 is a first parallel conductor group arranged at equal intervals, 211e 21ts 21s...21p-1
* Consists of m conductors of 21□21p+1...211n. Each conductor 21. 214 are electrically coupled by the common line 22. Further, each switch 23. of the switch group 23 is connected to the other end of each conductor 211-21□. ,,,23
．． .

23,...2 ap-, *23pe 239+1
...23ffi is connected. 24 is a second parallel conductor group having a direction perpendicular to the first parallel conductor group 21 and arranged at equal intervals, 2416241e 2'
l...24. -, ,24. .

It consists of n conductors of 24, +, . . . 2411. 1st
．． The second parallel conductor groups 21 and 24 are separated by an insulating film such as a transparent glass plate. One end of each of the conductors 241 to 2dll of the second parallel conductor group 24 is electrically coupled by a common line 25.

And the common lines 22, 25 are grounded. The other end of the second parallel conductor group 24 is connected to each switch 2 of the switch group 26.
61 m 26@e 2 J...26q-1e 2
6qs28q-,...28n are connected.

The terminals of the switches in the switch group 23 and 26 on the opposite side from each parallel conductor are connected in common for even numbered terminals and odd numbered terminals, respectively, and are connected to the input side of the differential amplifier 2T. Each switch in switch group 23.26 is connected to decoder 2.
It opens and closes according to the signal from 8.29. switch group 23
Or, in step 26, if any one odd-numbered switch and one even-numbered switch are selected and closed, a sense coil with one turn of parallel conductors connected to the switch is formed, and the differential amplifier 27.

Various methods are possible for selecting each switch, such as selecting two switches with a gap between them.

For the switch group 23, this is 23. and 23,
,．． 23. and 23. ．． 23. and 23. ...23N-t
and 231++1...23n-, and 2 of the combination of 230
This is a method of driving each switch (positive integer) s At this time, a coil with one turn formed from a parallel conductor I [K sense coil 5C-1, 5C-2...
・SC-1・-8G-(n-2)/2. (l
and (n-2)/2 is a positive integer). When the tip of the electromagnetic pen 30 is brought close to these sense coils SC (no suffix is added when they are referred to collectively), the magnetic flux generated from these sense coils 5CVc pen coils 9 interlinks.
voltage induced. Sensefil 5C-t-1,5c-
The induced voltage of it sc-ben+1 is Vl-1#, respectively.
Let vl e Vl+1. The switch group 26 is similarly selected and driven, and the induced voltage of the O sense coil SC that selects the second sense coil group composed of the parallel conductor group 24 is detected by the differential amplifier 2T, and the induced voltage is detected by the signal processing circuit 3.
1. The signal processing circuit 31 is a decoder 28.2
9 to select and close the switches in the switch groups 23 and 28, and to measure and process the induced voltage in each sense coil SC. When the signal processing circuit 31 measures the maximum voltage, the signal processing circuit j! From the signal sent by f%31 to decoder 2B or 29, it is possible to identify which sense coil SC has the maximum induced voltage.

When the tip of the electromagnetic pen 30 is located inside the sense coil SC-■, the induced voltage of the sense coil SC- is the maximum, so the signal processing circuit 31 identifies the maximum voltage. This makes it possible to determine which sense coil SC the tip of the electromagnetic pen 30 is located on.

The method of determining detailed coordinates within the sense coil when using the electromagnetic pen 30 shown in FIG. 3 is the same for the input panels shown in FIGS. 1 and 4. A ROMK with the relationship between V(x) in equation (1) and the coordinate X is stored, and Vp-1+V p *
The above method of accessing the ROM with a signal corresponding to the calculated value of V (x) based on Vp+1 may be used, but since the relationship between V (x) and X is almost linear, linear approximation is possible. Alternatively, a method may be used in which X is determined by calculation.

For example, when approximated by V (xl '' - xll + 1), the coordinates can be obtained from X = l (1 - Vlxl) K.

Also, x = Alog (vp+s/vp-t) Ic
Therefore, X may be calculated. The y-coordinate can be determined by performing similar processing or calculation based on the induced voltage of the second sense coil group 2. Switch group 3, 4.23
A CMOS switch or the like can be used for ゜26. amplifier 5
is connected to switch group 3.4, but switch group 3
Separate amplifiers may be used for and 4.

Similarly, separate amplifiers may be used for switch groups 23 and 26.

The input panel shown in FIG. 4 has a structure suitable for making a sense coil by vapor deposition, and is advantageous when a transparent digitizer is required.

Since the digitizer of the present invention uses a magnetic core 16 made of ferrite or the like for the electromagnetic pen 30, it is difficult to write on paper during input. However, if the human input section is made transparent, a display is placed on the underside of the input section, and the lines drawn on the input panel are displayed in real time on the digitizer underneath, it is possible to monitor them in the same way as if they were written on paper.

Therefore, for such uses, there is no problem even with a pen that cannot write on paper.

As explained above, in the electromagnetic induction digitizer of the present invention, since the magnetic flux is generated near the tip of the electromagnetic pen, there are fewer errors in detecting coordinates when the pen is tilted.

Furthermore, by setting the curvature of the tip of one core to an appropriate value, it is possible to further reduce the detection error. Therefore, when inputting a handwritten character shape using an electromagnetic induction digitizer while holding a pen in the hand, it is possible to input a character shape with little deformation. When the digitizer is made transparent and the display is stacked on the bottom display to monitor handwritten text and figures on the bottom display, there is less misalignment between the letter 1 figure being filled in and the letter 1 figure being monitored on the display, making input easier. becomes. Furthermore, since a magnetic core is used, compared to the case of an air core, it has advantages such as being able to generate a large magnetic flux with a small current, reducing the heat generation of the electromagnetic coil, and reducing the output of the oscillator.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing an example of the input panel and electromagnetic pen of a conventional electromagnetic induction digitizer, Figure 2 is a configuration diagram showing the main parts of a conventional electromagnetic pen for an electromagnetic induction digitizer, and Figure 3 is a circuit diagram of this example. FIG. 4 is a block diagram of the main parts of the electromagnetic pen used in the digitizer of the invention, and is a circuit diagram showing another embodiment of the invention. In the figure, 1.2 is a sense fill group, 3.4 is a switch group,
6. T is a decoder, 9 is a pen fill, 11 is a signal processing circuit, 12 is a surface, 15 is a housing, 16 is a magnetic core, 1T is a tip, 18 is a contact part, and 30 is an electromagnetic pen.

Claims (1)

[Claims] To select an electromagnetic pen with a magnetic core placed at the tip and a coil wound around this magnetic core, a sense coil group formed using parallel conductors with one turn, and a sense coil of this sense coil group. a group of switches, a decoder for selecting and closing the group of switches, a decoder for scanning and selecting the group of sense coils, and linking the sense coil with the magnetic flux generated from the magnetic core of the electromagnetic pen to close the sense coil. and a signal processing circuit for detecting the position of the tip of the electromagnetic pen by processing the signal based on the voltage induced in the electromagnetic pen.