JPS6035684B2 - Coordinate detection device - Google Patents

Description

[Detailed Description of the Invention] '1} Technical Field of the Invention The present invention relates to a coordinate interpretation device, a so-called digitizer;
The present invention relates to a coordinate measuring device that obtains the coordinates of a specified position from the phase of a rotating magnetic field formed on a flat plate by a plurality of drive coils.

[2] Background of the technology A coordinate reading device is a device that reads the coordinates of a pen placed on a flat board, and is used, for example, in graphical information processing systems that play an important role in the fields of automatic design and drafting technology. be.

As this type of coordinate reading device, the first method is an electrostatic coupling method,
A second method is an electromagnetic induction method, and a third method is an ohmic method. The present invention is based on the second electromagnetic induction method, and in particular, coordinate theory that detects a position from the phase of a rotating magnetic field. Refer to equipment.

{3} Prior Art and Problems The conventional coordinate sampling device of the above type has a plurality of coils arranged in parallel on a plane slope, and each transmits a plurality of drive signals out of phase with each other. There is an alternating current magnetic field generator above the plane plate that generates a rotating magnetic field with a different phase depending on the position on the plane slope by energizing a coil, and is located above the plane plate to detect the rotating magnetic field. It consists of a magnetic field detector.

In this case, from one end of the flat slope to the pond end,
Since it forms a rotating magnetic field whose phase changes continuously from o to 360 o, it is possible to know the phase of the magnetic field detected by the magnetic field detector (the aforementioned pen) and thereby know the coordinates where it is located. can. However, the above-mentioned type of coordinate negotiating device still does not have sufficient accuracy.

That is, although the phase of the rotating magnetic field should change linearly from one end of the plane slope toward the pond end, in reality it included undulations in a roughly S-shape, and perfect linearity could not be expected. However, the central portion of the flat plate exhibits a good to poor quality. For this reason, the present applicant previously proposed a coordinate measuring device capable of highly accurate position detection anywhere on a flat plate from one end to the other from Tokusho Sho 56-20978 No. 1. The prior application will be explained below with reference to the drawings.

FIG. 1 is a schematic diagram showing the first embodiment of the prior application. In this figure, the discussion device 10 includes an AC magnetic field generator 11 and a drive section 1 that supplies a drive signal out of phase to the generator 11.
3 and a magnetic field detector 12 forming a so-called pen.
The other blocks are those that process the output from the detector 12 and generate coordinate output. A rotating magnetic field M is formed above the flat plate provided in the generator 11, and the phases thereof differ as indicated by arrows. The position of the pen 12 can be determined from this change in phase. In order to distribute the rotating magnetic field M as described above, the generator 11 includes a plurality of coil groups. FIG. 2 is a plan view showing the arrangement of a plurality of coils forming a rotating magnetic field in terms of one-dimensional coordinates.

In FIG. 2, reference numerals 21 to 25 represent a plurality of drive coil groups, which receive drive signals ◇ and 5 whose phases are shifted from each other. FIG. 3 shows these mutually phase-shifted drive signals.

FIG. 3 is a waveform diagram showing the waveforms of drive signals G to G5 shown in FIG. As is clear from this figure; the phases of the respective drive signals are mutually shifted by a certain amount. This phase shift causes the phase of the rotating magnetic field M to change continuously. However, in the past, the alignment between the phase and the position on the plane slope was not good, resulting in poor accuracy. Fourth
Fig. A, Fig. 4B, Fig. 4C, and Fig. 40 are graphs used to explain the principle of the coordinate sampling device according to the earlier application.

Of these, the graph in FIG. 4B shows a curve corresponding to the above-mentioned nullity, and corresponds to an ideal case. In other words, linearity is the best. If the linearity is thus good, the position x can be accurately determined from the detection phase ox (the phase of the rotating magnetic field M). However, in reality,
The curve has undulations near both ends as shown by the dotted line in FIG. 4B, making it difficult to obtain an accurate position x over the entire plane plate. Therefore, in the prior application, in addition to the fundamental wave (FIG. 3) component (for example, 4k) used to obtain the curve in FIG. 4B, an n-th harmonic component is introduced.

When looking at the case where the frequency is n times higher, a curve similar to that shown in Fig. 4B appears repeatedly n times, and the areas 1 and 1 shown in Fig. 4A appear.
2...n is defined. The peak in each region corresponds to a phase of 2m, and changes sequentially from the left to 2 waves, 2×2 waves, and so on. The force segmented in this way is the 4th B
The linearity is much better than the curve shown in the figure. Fourth
Diagram C shows the changes in the 2 rows, 2×2 rows, etc. by stretching them linearly. Therefore, first, it is known exactly where Ben 12 is located within each area.

However, in this case, it is not known which region the region is located in as a whole. For this reason, a fundamental wave component signal with poor linearity is again used. Fig. 4D briefly shows the detection principle of the present invention. If the position where Ben 12 is placed is 8x (single dot silver line) in phase display, the position can be accurately determined from the curve C of the corresponding area due to the harmonic component. Read x, and then find out what number the region is from the curve C' based on the fundamental wave component (see the intersection marked with ○ in the figure)
. In this way, which position within which region is determined with high precision. Returning to FIG. 1 again, the detection winding 14 in the magnetic field detector 12 is sensitive only to the fundamental wave component, and the curve 〇 shown in FIG. 4D is extracted from the first detector 16 (this is the same as before). . On the other hand, the detection winding 15 in the magnetic field detector 12 is
Curve C shown in Figure 40 is sensitive only to harmonic components.
is extracted by the first detector 17. The processing circuit 18 determines the target coordinate position based on the information on these curves C and C'. What the detection winding 14 should be sensitive to is only the fundamental wave component (for example, 4K ship) of the drive signal.

Since this drive signal is a rectangular wave as shown in FIG. 3, it necessarily contains many harmonics. A part of it, for example, the 8th harmonic (3kHz for the 4kHz fundamental wave)
2k generation) from the detection winding 15. By the way, in the above-mentioned prior application, in order to detect the phase of the n-th harmonic component, the n-th harmonic component of the output signal of the detection winding is extracted by a bandpass filter, and the zero-crossing point of the reference signal is extracted. The time difference from to the zero-crossing point of the harmonic component is expressed as the phase, but the temperature characteristics of the waveform filter or the comparator that detects the zero-crossing point and the S/N of the output signal are dependent on the overall device. It has the disadvantage of being highly dependent on accuracy.

(2) Purpose of the Invention The object of the present invention is to eliminate such drawbacks, to provide a coordinate detection device that does not require a waveform device or the like and does not depend on temperature characteristics.

{5} Structure of the Invention According to the present invention, the present invention has a plurality of coils arranged in parallel on a plane slope, and energizes each of the plurality of coils with a plurality of mutually phase-shifted drive signals. an alternating current magnetic field generator that forms a rotating magnetic field with a different phase depending on the position on the plane plate above the plane plate; and a magnetic field detector that is located above the plane plate and detects the rotating magnetic field. extracts the fundamental wave component of the drive signal and its n-th harmonic component (n is an integer of 2 or more) from the output of the magnetic field detector, and determines the position on the flat plate from the n-th harmonic component. is divided into n consecutive regions and the position within each region is read, while the fundamental wave component is used to divide the region into n consecutive regions.
A coordinate detection device includes a processing circuit that reads the position of the plane plate on which the magnetic field detector is placed by determining the number of the area in the area, and a processing circuit that reads the position of the flat plate on which the magnetic field detector is placed. , two Fourier coefficients an and bn are obtained, and the Fourier coefficients an and bn are used as the n-th harmonic components to read the position on the plane plate.

(6} Examples of the Invention The present invention will be described below based on Examples.

FIG. 5 is a diagram showing an embodiment of the present invention, in which 14 is an amplifier, 15 is an AD converter, 16 is a Fourier transform circuit, and 17 is a diagram showing an embodiment of the present invention.
18 is a phase detection circuit, 18 is a subtraction circuit, 19 is a discrete value generation circuit that generates a discrete value from an input phase, 20' is a multiplication circuit, and 21 is an addition circuit. In the present invention, the output signal Vj of the detection winding is an n-1, n-th order harmonic component extracted by a filter (not shown), which is amplified by an amplifier 14 and converted into N data by an A/D converter 15. Sk(K:
0, 1...N-1).

The digitally converted signal Sk is sent to the Fourier transform circuit 16
A discrete Fourier transform is performed according to m formula, and n
The Fourier coefficients an and bn of the harmonics are determined.

an = Kisaburo Koetaku - COS or bitter bamboo bn = Yoshimo Toru - mother N Kajiten...I1' Next, find the phase Jn from the Fourier coefficients an and bn, but the phase ◇n is
It is determined by the {2} formula from the m formula.

◇n= is n-, Namahaho an Here, the trigonometric function of the {1', ■ formula can be found by referring to a table for simplicity.

In addition, the Fourier coefficients an-1 and bn-1 of the n-1th harmonic
is obtained in the same manner, and the phase n-1 is obtained from this Fourier coefficient by the phase detection circuit 17.

Here, as explained in Fig. 4, the phase of the nth harmonic? n
(0 to 2 bamboo rad) in all tablet areas,
Since it rotates n times and cannot be distinguished, the phase of the fundamental wave component is used to distinguish the region. Therefore, the subtraction circuit 18 performs subtraction of n-1 by n-1 to obtain the phase 0.

At this phase, is input to the discrete value generation circuit 19, and depending on the magnitude of the phase, values of 0, 1, 2, .

The multiplication circuit 20 multiplies the output of the discrete value generation circuit 19 by 2m. Therefore, the output of the multiplier circuit 20 indicates the above region.

Then, the coordinates are determined by adding the phase gn and the adder circuit 21.

{7) Effects of the Invention As described above, according to the present invention, the phase is determined using Fourier coefficients, so there is no need for a monkey waver, a comparator, etc. as in the past, and the influence of temperature etc. can be eliminated. It becomes possible to eliminate it.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the embodiment of the earlier application, Figure 2 is a diagram showing the coil arrangement, Figure 3 is a diagram showing the drive signal, Figure 4 is a diagram showing the principle of the earlier application, and Figure 5 is a diagram of the present invention. It is a figure showing an example of the invention. In the figure, 14 is an amplifier, 15 is an AD converter, 16 is a Fourier transform circuit, 17 is a phase detection circuit, 18 is a subtraction circuit,
19 is a discrete value generation circuit that generates a discrete value from an input phase, a Futagawa multiplication circuit, and 21 is an addition circuit. *Figure 2Figure 3Figure 4AFigure 48Figure 4CFigure 4DFigure Tsutomu J figure

Claims (1)

[Claims] 1 It has a plurality of coils arranged in parallel on a plane plate, and by applying a plurality of mutually phase-shifted drive signals to the plurality of coils, the plane plate is placed above the plane plate. an alternating current magnetic field generator that forms a rotating magnetic field with a different phase depending on the position of the plane, a magnetic field detector that is located above the plane plate and detects the rotating magnetic field, and a basis for generating the drive signal from the output of the magnetic field detector. A wave component and its n-th harmonic component (n is an integer of 2 or more) are extracted, and the position on the plane plate is divided into n consecutive regions based on the n-th harmonic component, and each region is divided into n consecutive regions. A process of reading the position of the flat plate on which the magnetic field detector is placed by determining which region out of n the region is, using the fundamental wave component. At a coordinate detection position having a circuit, the output of the magnetic field detection circuit is Fourier transformed to obtain two Fourier coefficients a_n, b_n, and the Fourier coefficients a_n,
A coordinate reading device characterized in that b_n is used as the n-th high frequency component to read a position on the plane plate.