JPS6035682B2 - coordinate reading device - Google Patents

Description

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

'2} Technical Background A coordinate capture 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. Among these, the present invention is based on the second electromagnetic induction method, and in particular, a coordinate reading device that detects a position from the phase of a rotating magnetic field. mention.

'3} Follow-up technology and problems The general coordinate measuring device of the above type has a plurality of coils arranged in parallel on a plane slope, and sends a plurality of mutually phase-shifted drive signals to each of the plurality of coils. an alternating current magnetic field generator that forms a rotating magnetic field with a phase different depending on the position on the plane plate above the plane plate by energizing the coil;
It consists of a magnetic field detector positioned above the flat plate to detect the rotating magnetic field (see Japanese Patent Laid-Open No. 57-198081).

In this case, from one end of the flat slope to the pond end,
Since it generates a rotating magnetic field whose phase changes continuously from o to 3600 degrees, it is possible to know the position 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 type of coordinate reading device does not have sufficient accuracy.

In other words, the phase of the rotating magnetic field should change linearly from one end side to the other end side on the plane plate;
In reality, it included undulations in a roughly S-shape, and I couldn't expect a very perfect nuariness. However, in the central part of the flat slope, it shows a good grin. For this reason, there has been a desire for a coordinate reading device that can detect positions with high precision anywhere on a flat plate from end to end. In order to meet these demands, the following proposal (Mochiiso Sho 56-20978) has been made.

FIG. 1 is a schematic diagram showing a subordinate coordinate reading device that forms the premise of the present invention. In this figure, the coordinate reading device 10 cooperates with an alternating current magnetic field generator 11, a drive 13 that supplies phase-shifted drive signals to the generator 11, and a magnetic field detector 12, which forms a so-called pen. The other blocks are detector 1
This is the part that processes the output from 2 and generates coordinate output. Above the flat plate provided in generator 1 1 is a rotating magnetic field M.
are formed, and their phases differ as shown by the 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. 2A is a plan view showing the arrangement of a plurality of coils forming a rotating magnetic field with one-dimensional coordinates, and Fig. 2B is a plan view showing the arrangement of a plurality of coils forming a rotating magnetic field with two-dimensional coordinates. FIG.

In FIG. 2A, 21 to 25 are a plurality of drive coil groups,
Drive signals 0, ~? mutually out of phase? Receive 5. If it is carried out in x-y two dimensions, as shown in FIG. 2B, drive coil groups 21' to 25' are provided orthogonal to the drive coil, and drive signals J,' to J5' are applied to each group. For simplicity, the following explanation will be made using a one-dimensional case as an example. When these mutually phase-shifted drive signals are illustrated, the result is as shown in FIG.

FIG. 3 shows the drive signals ◇. shown in FIGS. 2A and 2B.
It is a waveform chart showing waveforms of ~◇5. 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. Figure 4A, Figure 4B, Figure 4
FIG. C and FIG. 4D are graphs used to explain the principle of the conventional coordinate calculation device, which is the premise of the present invention.

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. In this way, if the linearity is 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 addition to the component (for example, 4k ratio) of the fundamental wave (Fig. 3) used to obtain the curve shown in Fig. 4B,
Introduce harmonic components. When the frequency is n times higher, a curve similar to that shown in FIG. 4B appears repeatedly n times, and the regions 1, 2, 2, 3, 4, 2, 2, 2, 2, 2, 2, 2, and 2 shown in FIG. 4A are defined. The peak in each region corresponds to a phase of 2 m', and changes sequentially from the left to 2 waves, 2×2 waves, and so on. The curve segmented in this manner has much better linearity than the curve shown in FIG. 4B (the detailed reason will be explained later). Fourth
Diagram C shows the changes in 2 rows, 2 x 2 rows... Shochiku, stretched out linearly. Therefore, first, it is known exactly where Ben 12 is located within each area.

However, in this case, it is not known which area the area is in as a whole. For this reason, a fundamental wave component signal with poor linearity is again used. Fig. 4D simply shows the detection principle of the slave which forms the premise of the present invention. If the position where Ben 12 is placed is 8n (dotted chain line) in phase display, the curve C of the corresponding area due to harmonic components Accurately read the position x from , and then find out what number the region is from the curve C' of the fundamental wave component (see the intersection marked with a circle in the figure). In this way, which position within which area is determined. Returning to Figure 1 again, magnetic field detector 1
The detection winding 14 in 2 is sensitive only to the fundamental wave component, and the 4th D
The curve 〇 shown in the figure is extracted by the second detector 16 (this is the same as before).

On the other hand, the detection winding 15 in the magnetic field detector 12 is sensitive only to the n-th harmonic component, and the first detector 17 extracts the curve C shown in FIG. 4D. The processing circuit 18 determines the target coordinate position based on the information on the curve C and 0. What the detection winding 14 should be sensitive to is only the fundamental wave component (for example, 4 kHz) 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 ratio) is discarded and taken out from the detection winding 15. In other words, the harmonic components are simply those that are naturally occurring and are used after being filtered. The reason why the positions of the detection windings 14 and 15 are shifted in height in FIG. 1 is as follows.

In the above-mentioned coordinate reading device (Japanese Unexamined Patent Publication No. 57-1981 No. 081), which forms the basis of the present invention,
It has been proven that it is preferable to place the detection winding at a height h (measured from the tip of the bend) that satisfies a.h(d)1, where a is the phase change rate.

Favorable means that regardless of Ben's preferences, a fairly accurate reading can be made. In short, the larger the phase change rate of the magnetic field on the plane plate, the more preferably the position of the detection winding is lowered. Regarding the detection winding 15,
The phase change rate a that this should bear is the phase change rate shown in FIG. 4A, which is n times the phase change rate corresponding to the fundamental wave component shown in FIG. 4B. If the phase change rate a becomes n times,
From the above a and h-1, the height h of the detection winding 15 can be reduced to 1/n. In this way, the height of the detection winding 15 can be reduced to 1/n of the height of the detection winding 14.

Let us now consider the advantages of reducing the height of the detection winding. When the sense winding is at a high level, it will be influenced by a fairly wide range of drive coils (21-25 in Figure 2A). This will adversely affect reading accuracy. As a result, the lower the height of the detection winding, the less it is affected by the above-mentioned adverse effects, and the better the linearity becomes. The reason why the curves in each region shown in FIG. 4A have good linearity is because the output from the detection winding located at a low position is handled. To develop this further, it would be better not to have the detection winding 14 located at a high position as shown in FIG.

Therefore, the detection winding 14 is eliminated. In other words, we have proposed a method in which not only the n-th harmonic component but also the fundamental wave component can be handled using only the detection winding 15 located at a low position. Since this is not related to the gist of the present invention, the explanation will be omitted. However, an inconvenient problem has arisen in the above-mentioned conventional reading device.

This problem is related to the reading accuracy, and referring to Figure 4D above, reading errors may occur near the boundaries between the areas corresponding to the triangular waves defined by each curve C. It is something. The reason for this is that the fundamental wave component represented by the curve ○ in the figure is used to determine which area the position x to be read is located in. In this case, if the position x is near the boundary, The problem lies in the fact that it is often difficult to accurately distinguish which area it belongs to. That is, this is because the precision of the curve C' defined by the fundamental wave component is considerably inferior to the precision of the curve C defined by the harmonic components. If curve 0 were detected with perfect linearity, the above-mentioned problems would not occur, but in reality, it is extremely difficult to expect such perfect linearity from curve C'. [4] Purpose of the Invention In view of the above-mentioned problems, the object of the present invention is to propose a coordinate reading device that can read coordinates with high accuracy even if Ben is placed within such a range near the boundary. It is.

(5) Structure of the Invention In order to achieve the above object, the present invention provides read data of a position within a region that is made using a harmonic component (the first read data is a position of the region itself that is made using a fundamental wave component). Noting that the accuracy is sufficiently high compared to the read data (second read data) of the area position indicating the area position, a predetermined correction is made to the second read data based on the first read data, The present invention is characterized in that the second read data after correction and the first read data are combined to obtain the target coordinate read data.

[6] Embodiments of the Invention FIGS. 5A and 5B are graphs used to explain the principle of the present invention.

The vertical axes of A and B in this figure indicate position data within the region expressed using harmonic components, the vertical axis of A indicates the first read data, and the vertical axis of B indicates offset data (described later). )
shows. To summarize and conclude, the principle of the present invention is as follows. When the pen is placed near the boundary between regions, this fact can be accurately grasped by the above-mentioned first read data using harmonic components. Moreover, according to the first read data, the adjacent k-th area and (k11) (k
It is also known to which area the pen belongs among the areas (ISkSn, a natural number). This is because, near the boundary, if it belongs to the k-th area, the first read data will show a value close to the maximum possible value 'FFF', and conversely, if it belongs to the k-th area near the boundary, the (k+1)th area If it belongs to the first discussion data, the minimum possible value is '000.
' This is because it shows a value close to '. This can change continuously from the minimum value (one side) to the maximum value (tenth side) in any area outside the first rare data, and the area changes one after another. This is because the first reading data appears as a line return of similar data. Thus, according to the first read data, Ben is placed near the boundary, and the kth or (k+1)
It is accurately determined that it is placed in the th area.
Therefore, the second read data (
Since the area read data) is inaccurate near the boundary, offset data is forcibly added to the second read data and the final second read data is obtained. This offset data is used to change the second read data near the boundary to the second read data at a position further away from the boundary, and the second read data is used to determine only in which area the second read data is located. In general, it is clear that it is more accurate to determine the second read data as close to the center of each area (see the circle in FIG. 40) as possible. Specifically, when the area is on one side of a certain boundary, a predetermined amount of offset data is added to the second morotori data, and conversely, when it is on the 10th side of the boundary, a predetermined amount of offset data is added to the second morotori data. , a predetermined amount of offset data (plus) is added to the second interpretation data. This offset data amount is selected so that it becomes larger as it approaches the boundary (nearest). Even if it is near the boundary, if it is relatively far from the boundary, there is no need to add a large amount of offset data. Referring to FIGS. 5A and 5B, first, in A, the length of each region (region expressed using harmonic components) is assumed to be L. Note that the triangular waveform of A is the same as the triangular waveform shown in FIGS. 4A and 4D previously described. The above length L is calculated as IFFF'('
' means 16 ships). The count value referred to here is the analog-to-digital converted harmonic signal from the first detector 17 in FIG. 1, which is counted for a predetermined period. It will be done. The symbol ■ along the horizontal axis of FIG. 5A represents the tip position of the pen (magnetic field detection winding 12) described above.

The figure shows the case where the pen is placed on the boundary between areas. The range of variation in the second read data obtained using the fundamental wave component when the tip of the pen is placed at the position (■) is indicated by E and E2, and is the so-called error range of the second read data. E is an error that is noticeable when the pen is tilted to an area on the 10th side of the boundary, and E2 is a noticeable error when the pen is tilted to an area on one side of the boundary. In the count value conversion mentioned above, E is '000,~'600', and E2 is 'AO○,
~'FFF'. Usually the size of E, and E
2 have the same size. FIG. 5B schematically shows a method for determining the size of the offset data (OFS) described above. If, for example, it is found from the first read data that ■ is on the boundary, the maximum size of Y. , adds offset data of at least Y3 to the second read data. Here Y, is Y,
= L-E, and in terms of count value, Y, 2'FFF'-'600' = 'Team F'.

Y, is the maximum offset data and its (LE,)
shall not exceed. This Y applies because the pen in ■ has the highest error on the ten side, and the maximum error is
, is included in the second read data, and if offset data exceeding (L-E,) is added to the second read data in such a state, the second read data after adding this offset is This results in a situation where the second read data no longer indicates the area in question, but instead indicates an adjacent area on the 10th side.
The Y3 is the minimum offset data and corresponds to when Ben is standing upright on the square. In this case, Y3
=E, and Y3='600' by checking the count value.

In such an upright state, it is sufficient to simply add offset data sufficient to exceed the error range to the second read data. Next, the tip of the pen is '600, which is the end of the ten-side error.
' Consider a time when .

It can be seen from the first read data that it is at '600'. In such a case, the maximum offset data to be added to the second read data is Y2, and the minimum is 0. Here, Y2 is Y2=L-2E, and in terms of count value, Y2='FFF'-2×'600'='3FF'.

The reason for setting Y2=L-spot is that when the tip of the ben is at 600', if more offset data than this is added to the second read data, the second read data after adding this offset will be This results in a situation where the technique does not indicate the area in question, but instead indicates the area next to it on the 10th side. Note that when the tip of the ben is at a position exceeding '600', there is no need to add an offset. If this position is located near the center of the area, it is unlikely that the second read data will misidentify the area. In this way, the offset data is determined from the hatched area extending downward to the left surrounded by the line segment connecting Y and Y2 and the line segment connecting Y3 and 0 in FIG. 5A.

Assuming that the tip of the pen is placed at any position x between '000' and '6 side', the offset data for any x is E, 1 x < OFS 1 < (LE,) - Determined by ×.

OFS+ means adding an offset of 10 (plus), and means offsetting the second read data to the 10 side. Note that E and -X correspond to the linear equation of the line segment connecting Y3 and Y4. In the above explanation, the tip of the pen is
It is assumed that the pen is placed between '000 and '600' in the area, but if the offset data is one (minus) offset (OFS-), the tip of the pen will move from area 'AOO' to 'FFF'. The same is true when placed in '.

When the tip of the pen is placed at such a position ('AOO' to 'FFF'), offset data is added to the second read data to offset it further to one side. The range that the offset data OFS- should take is determined by ×10(E2-L)<OFS-<X-E2.

These linear equations x 10 (E2-L) and x-E2 are the fifth
This corresponds to the lower limit and upper limit line segments of the area indicated by downward hatching to the right in FIG. Since the principle of the present invention has been clarified through the above explanation, an example of its implementation will be shown at last.

FIG. 6 is a block diagram showing an example of a circuit for concretely implementing the principle of the present invention explained using FIGS. 5A and 5B.

In this figure, 61-1 is a first read data input register that temporarily stores the first read data (position data within each area) from the first detector 17 in FIG. 61-2
is an input register for the second reading data, and temporarily stores the second reading data (area reading data indicating the number of the area) from the second detector 16 in FIG. These read data are combined through an arithmetic circuit 64 (which can be composed of an adder) and become the final coordinate data OUT to be read.
7A and 7B are diagrams respectively showing a conventional data format and a data format based on the present invention for the coordinate data OUT. In FIG. 7A, 0' indicates the second read data area, and 1 indicates the first read data area J. For example, each bit has a configuration of 3 bits and 9 bits, and consists of 12 bits as a whole. In the data format shown in Figure B, the first read data area 1 is the same as before, but the second mystery data area has been corrected by the offset data OFS based on the first read data. This becomes new highly accurate second read data and is stored in the second read data area 0'. Returning to Figure 6, the offset data can be stored, for example, in a ROM (
read only memory) 62.

That is, by looking at the contents of the first read data in the input register 61-1, and from the certain relationship explained in FIG. 5B,
Offset data OFS corresponding to each first read data is taken out from the ROM 62 and added to the second read data from the registers 61-2 in an adder 63. however,
The configuration shown in FIG. 6 is an example, and it is of course possible to perform similar operations under program control by a microprocessor. '7} Effects of the Invention As described in detail above, according to the present invention, a coordinate reading device that can perform highly accurate reading even near the boundaries between regions is realized.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing a conventional coordinate reading device that forms the premise of the present invention, Fig. 2A is a plan view showing the arrangement of a plurality of coils forming a rotating magnetic field for one-dimensional coordinate reading, and Fig. 2B is a A plan view showing an example of the arrangement of a plurality of coils forming a rotating magnetic field for two-dimensional coordinate reading, and FIG. 3 shows the drive signals shown in FIGS. 2A and 2B. , ~◇5 waveform diagrams, Figures 4A, 4B, 4C, and 4D are graphs used to explain the principle of the conventional coordinate reading device that forms the premise of the present invention, and Figure 5A and B are graphs used to explain the principle of the present invention, FIG. 6 is a block diagram showing an example of a circuit for concretely implementing the principle of the present invention explained using FIGS. 5A and B, and FIG. A and B are coordinate data OU
FIG. 2 is a diagram showing a conventional data format of T and a data format based on the present invention, respectively. 10...Coordinate control device, 12...Magnetic field detector, 11...AC magnetic field generator, 13...
... Drive section, 21-25, 21', 25'...
・Drive coil, 18... Processing circuit 62...
・ROM, 63...Adder, 64... Arithmetic circuit, M
...Rotating magnetic field, ◇,~5,◇,'~low5'・
... Drive signal, OFS ... Offset data. Figure 1 Figure 2A Figure 2B Figure 3 Figure 4A Figure 4B Figure 4c Figure 40 Figure 5 Figure 6 Figure 7

Claims (1)

[Scope of Claims] 1. A device having a plurality of coils arranged in parallel on a plane plate, and applying a plurality of mutually phase-shifted drive signals to each of the plurality of coils, the plane plate is an alternating current magnetic field generator that forms a rotating magnetic field whose phase differs depending on the position on the plane plate above; a magnetic field detector located above the plane plate that detects the rotating magnetic field; and the magnetic field detector. a processing circuit that detects the phase of the rotating magnetic field by inputting the output from the magnetic field detector, and reads the position of the magnetic field detector placed on the flat plate, and the processing circuit detects the phase of the rotating magnetic field using the output of the magnetic field detector as an input. extracting the fundamental wave component of the drive signal and its n-th harmonic component (n is an integer of 2 or more), and dividing the position on the plane plate into n continuous regions from the harmonic component; , an intra-region position reading circuit for reading the position within each region, and a positioning circuit for determining the position of the magnetic field detector by determining which region among n regions the region is, using the fundamental wave component. an area reading circuit that reads the position of the flat plate that has been read; and an arithmetic circuit that synthesizes first read data from the intra-area position reading circuit and second read data from the area reading circuit and outputs coordinate data to be read. In a coordinate reading device consisting of,
A first means for detecting that the first read data is within a range near a boundary between the areas, and whether the first read data is in an area on one side of the boundary or an area on the + side of the boundary. and a second means for determining the negative offset data or positive offset data, respectively, depending on whether it is in the negative side region or the positive side region based on the determination result of the second means. a third means for adding the offset data to the second read data, and uses the second read data to which the offset data is added as the second read data to be synthesized in the arithmetic circuit. 2. The coordinate reading device according to claim 1, wherein in the third means, the value of the offset data is set smaller toward zero as the first read data indicates a position farther from the boundary. 3. The first means and the second means are constituted by a ROM that outputs the corresponding - offset data or + offset data specified by the first read data, and the third means is configured by an adder. The second claim constituted by
Coordinate reading device as described in section. 4. The coordinate reading device according to claim 2, wherein the first means, second means, and third means are constructed by a microprocessor controlled by a predetermined program.