JP2010237913A - Coordinate correction method - Google Patents

Abstract

PROBLEM TO BE SOLVED: In a conventional coordinate correction method in which a coordinate input area is divided into a lattice shape, when an input that moves continuously across a plurality of cells of a lattice is performed, the correction result is obtained when a plurality of cells are corrected. It was not possible to correct it so that it was smoothly continuous at the boundary.
A coordinate input area is divided into a grid, and for each of two pairs of opposing sides constituting a cell, each of the two sets of opposite sides constituting the cell with respect to a detection coordinate existing in a specific cell of the grid, By finding the position between two sides that coincides with the detected coordinates when the slope is continuously changed to the side, there is no discontinuity or non-uniformity at the boundary between multiple cells. A correction result that is smoothly continuous can be obtained.
[Selection] Figure 1

Description

The present invention relates to a coordinate correction method for a coordinate input system that detects a position indicated by a coordinate indicator such as a finger or a pen.

As a coordinate input system for detecting a position indicated by a coordinate indicator such as a finger or a pen, for example, a touch panel or a pen tablet using capacitive coupling between a surface resistor and the finger or pen, or infrared and ultrasonic wave For example, a digital pen that determines coordinates by triangulation using a distance measured using a speed difference or the like. In such a coordinate input system, the detected coordinate value does not necessarily match the exact coordinate value.
For example, in a coordinate input system using capacitive coupling, the detection coordinates may deviate from the correct position due to the relationship between the surface resistance and the electrical resistance of the resistive surrounding electrode surrounding the surface resistance. is there. In addition, in a coordinate input system using infrared rays and ultrasonic waves, detection coordinates may deviate from an accurate position if the temperature-related processing is not sufficient or impossible.

As described above, as a method for correcting the detected coordinates shifted from the accurate position, for example, a method disclosed in Japanese Patent No. 3505970 (Patent Document 1) is known. In the method disclosed in Patent Document 1, the input range is divided into a grid having square cells, and when the accurate reference coordinate value of the grid point position and the position of the reference coordinate are indicated by the coordinate indicator, the method is actually performed. The reference detection coordinate value to be detected is stored in advance (for the reference coordinate value, the cell size of the lattice may be calculated as constant), and the lattice that is formed (distorted) using the reference detection coordinate as the lattice point is specified. For the detected coordinates detected in the cell, the detected coordinates are corrected based on the information of the points where the horizontal and vertical lines passing through the detected coordinates intersect with the four sides of the cell.

In this method, the detected coordinates are corrected by Equation (8) and Equation (9) of Patent Document 1. Depending on how the reference detection coordinates are distorted, even if all the cells are convex squares, for example, bc> ad and g / h <(bc-bd) / (bc-ad) or bc in the vicinity of the right side of the cell. If there is a region satisfying the condition of <ad and g / h> (bd-bc) / (ad-bc) (the notation conforms to the cited reference 1), the coordinates detected in the region are lattice coordinates. It is corrected outside the corresponding cell of the grid formed as a point. For this reason, depending on how the reference detection coordinates are distorted, when the coordinate indicator performs an input to move continuously across a plurality of cells of the grid formed using the reference detection coordinates as grid points, the coordinates are changed. In some cases, unnatural correction was made between cells of the lattice. Incidentally, the convex quadrangle means a quadrangle whose inner angle is less than 180 degrees.

Further, the method disclosed in Patent Document 1 is a method of performing linear correction within each cell, and depending on how the reference detection coordinates are distorted, there is an input that moves continuously across a plurality of cells. When done, the correction results could appear to bend at cell boundaries.

Patent 3505970

The present invention has been made in consideration of such points, and if all the cells constituting the grid formed using the reference detection coordinates as grid points are convex polygons, the coordinates detected in the cells are determined. , The correction is always corrected within the corresponding cell of the grid formed with the reference coordinates as the grid point, and when the input moves continuously across multiple cells, the correction result is the boundary of multiple cells. It is an object of the present invention to provide a correction method for correcting so as to be smoothly continuous.

The present invention relates to a coordinate correction method for correcting a detected coordinate value in a coordinate input system for detecting a position indicated by a coordinate indicator such as a finger or a pen, wherein the input range is a grid having at least a plurality of rectangular cells. The reference reference coordinate value of all the grid point positions and the reference detection coordinate value actually detected when the position of the reference coordinate is indicated by the coordinate indicator are stored in advance. Detection coordinates detected in a specific cell of a lattice formed with detection coordinates as lattice points are transferred from one side to the other side for each of two sets of opposite sides constituting the rectangular cell. A straight line passing through the detection coordinates when the slope is continuously changed is obtained, and the two straight lines are obtained in the corresponding cells of the lattice formed using the reference coordinates as lattice points. To coordinate transformation into two straight intersection of coordinates corresponding to the gist of the coordinate correcting method comprising.

In the coordinate correction method according to the present invention, if all the cells constituting the grid formed using the reference detection coordinates as the grid points are convex polygons, each cell of the grid formed using the detection coordinates as the grid points is included in each cell. The detected coordinates are converted into coordinates in the corresponding cells of the grid formed with the reference coordinates as the grid points, and the coordinates detected on the sides of the grid formed with the detected coordinates as the grid points are converted into the reference coordinates. Is a coordinate conversion function that converts to a coordinate on a side of a grid formed as a grid point. For this reason, discontinuity and non-uniformity at the boundaries of a plurality of cells do not occur.

In addition, regarding two cells sharing an edge connecting two adjacent lattice points, the differential of the coordinate transformation function in the direction orthogonal to the edge is equal regardless of which cell approaches the edge from the inside. Therefore, the correction result is smoothly continued at the cell boundary.

Furthermore, the coordinate transformation is based on a procedure for selecting a simple calculation when the result can be determined only by a simple calculation based on a plurality of condition determinations, and the calculation resources including the calculation time can be consumed. It can be reduced as much as possible.

The figure which shows the cell extracted from the grid | lattice of a reference | standard detection coordinate and a normalization reference | standard coordinate The figure which shows the concept of the mapping between (u, v) and (x, y) Flow chart showing the calculation procedure of u Flow chart showing the calculation procedure of v Diagram showing the positional relationship on the side connecting grid points The figure which shows the structure of Example 1. The figure which shows the experimental result of Example 1 and Comparative Example 1

Hereinafter, preferred embodiments of a coordinate correction method according to the present invention will be described in detail with reference to the accompanying drawings.
The input range is divided into a grid having at least a plurality of rectangular cells. Here, it is assumed that the horizontal and vertical lengths of the cells are constant in a certain input system. A geometrically accurate position of the grid point position configured in the input range is referred to as a reference coordinate. A position actually detected when the position of the reference coordinate is indicated by a coordinate indicator such as a finger or a pen is referred to as a reference detection coordinate. Further, for the purpose of explaining the correction method, the standard coordinate obtained by normalizing the horizontal length and vertical length of the cell to 1 is referred to as a normalized reference coordinate. The normalized reference coordinates can be easily converted to the coordinates of the actual coordinate input system by multiplying the cell size. Therefore, a method for converting coordinates detected on the grid formed by the reference detection coordinates into coordinates on the grid formed by the normalized reference coordinates will be described below.
The reference detection coordinates are determined in advance by measurement and stored. Since the reference coordinates are fixed for a known and specific input system, they may be stored in the same manner, or may be calculated during operation using the known horizontal and vertical lengths of the cell. Good.

FIG. 1 illustrates a corresponding cell extracted from a lattice formed with reference detection coordinates and normalized reference coordinates as lattice points in order to explain a coordinate correction method according to the present invention. . FIG. 1A shows reference detection coordinates (x ₁ , y ₁ ), (x ₂ , y ₂ ), (x ₃ , y ₃ ), and (x ₄ , y) in the coordinate system (x, y). ₄ ) shows the cell formed. The detected coordinate 1 is (x, y) and represents a coordinate detected when a certain point is indicated by the coordinate indicator. In general, the cells formed by the reference detection coordinates are not generally rectangular or square due to the influence derived from the method of the coordinate input system as described above. However, in a grid formed using the reference detection coordinates as grid points, all cells need to be convex quadrangles.

FIG. 1B shows the normalization reference coordinates of the corresponding cell in the coordinate system (u, v). Since the grid constituted by the normalized reference coordinates is a square grid with the horizontal length and vertical length of the cell being 1, (u ₁ , v ₁ ) is changed to (x ₁ , y ₁ ), (u ₁ +1, v ₁ ) corresponds to (x ₂ , y ₂ ), (u ₁ +1, v ₁ +1) corresponds to (x ₃ , y ₃ ), and (u ₁ , v ₁ +1) corresponds to (x ₄ , y ₄ ) To do. The normalized correction coordinate 2 is (u ₁ + u, v ₁ + v). The normalized correction coordinate 2 is a normalized coordinate corresponding to the detected coordinate 1 (x, y), and an accurate coordinate in the coordinate input system can be obtained by multiplying this by the cell size. By definition, 0 ≦ u ≦ 1, 0 ≦ v ≦ 1.

The purpose is to convert the detected coordinates 1 (x, y) into normalized correction coordinates 2 (u, v). As a conversion method, detection coordinates 1 detected in a specific cell of a lattice formed with reference detection coordinates as lattice points are converted into two pairs of opposite sides constituting a rectangular cell. A straight line passing through the detection coordinate 1 is obtained when the inclination is continuously changed from one side to the other side. Then, the coordinates of the intersection of the two straight lines corresponding to the two straight lines obtained earlier are obtained in the corresponding cells of the lattice formed using the normalized reference coordinates as the lattice points. Hereinafter, a procedure equivalent to this coordinate transformation will be described in more detail.

FIG. 2 shows how the mapping between the coordinate system (u, v) and the coordinate system (x, y) is performed. As shown in FIG. 2A, u is 0 on the left side of the cell and 1 on the right side, and takes a constant value on a line that continuously changes the slope from the left side to the right side. . In the lower side and the upper side, u increases evenly from the left end to the right end over the entire length of each side. Similarly, as shown in FIG. 2B, v is 0 on the lower side of the cell and 1 on the upper side.

In order to investigate which cell the detection coordinate 1 (x, y) is in an irregular shape on the grid formed by using the reference detection coordinate as a grid point, for example, it is well known. The following method can be used. In general, if a point is inside a convex polygon, for example, if it is considered to rotate around the side of the convex polygon counterclockwise, the point exists on the left side of the side for all sides. You can know by making sure you do. If a point exists on the right side of at least one of the sides, the point does not exist inside the convex polygon. Which side a point is on can be known by examining the sign of the outer product of the vector from the start point of the side to the point and the vector of the side. If the sign of all the outer products is negative, the point is inside the convex polygon. If there are one or two zeros in the outer product and the remaining outer products are all negative, the point is on the side of the convex polygon.

The purpose is to convert the detected coordinate 1 (x, y) to the normalized correction coordinate 2 (u, v), but the conversion is based on the distorted one (detected coordinate 1 (x, y)). Therefore, as a derivation of the conversion method, it is better to consider the conversion from the normalized correction coordinate 2 (u, v) on the square lattice to the detection coordinate 1 (x, y) and obtain the inverse conversion. If the mapping of (u, v) and (x, y) as shown in FIG. 2 is considered, x and y can be expressed as in the following Equation 1 using u and v.

In order to obtain the inverse transformation, when Equation 1 is solved for u and v, the quadratic equations for u and v are obtained. Considering that 0 ≦ u ≦ 1, 0 ≦ v ≦ 1, etc., u and v can be calculated by procedures as shown in the flowcharts of FIGS. 3 and 4, respectively. In the calculation, the value shown in the following formula 2 is used as an intermediate numerical value.

In order to calculate u, a, b, and c are first calculated (S1). If a = 0 (S2), u is determined by u = −c / b (S3). When a is not 0, if b ² -4ac = 0 (S4), u is determined by u = −b / (2a) (S5). When b ² -4ac is not 0, a value in the range of 0 ≦ u ≦ 1 is selected from u as a solution of the quadratic equation of au ² + bu + c = 0 (S6).

Similarly, to calculate v, first, d, e, and f are calculated (S11). If d = 0 (S12), v is determined by v = −f / e (S13). If not d = 0, if e ² −4df = 0 (S14), v is determined by v = −e / (2d) (S15). If not e ² −4df = 0, a value in the range of 0 ≦ v ≦ 1 is selected from v as a solution of the quadratic equation of dv ² + ev + f = 0 (S16).

Using the calculated u and v, a normalized coordinate can be obtained by (u ₁ + u, v ₁ + v), and by multiplying the cell size by this, an accurate coordinate in the coordinate input system can be obtained. be able to.

Next, with respect to two cells sharing an edge connecting two adjacent lattice points, the differential of the coordinate transformation function in the direction orthogonal to the edge should be the same regardless of which cell approaches the edge. Will be explained. FIG. 5 shows cell 3 formed by reference detection coordinates (x ₁ , y ₁ ), (x ₂ , y ₂ ), (x ₃ , y ₃ ), and (x ₄ , y ₄ ), reference detection coordinates ( x _{2, y 2),} it shows a _{(x 5,} y _5), the cell 4 formed by the (x _{6, y 6),} and _(x 3, _{y 3).} Cell 3 shares its right side with the left side of cell 4.

In Equation 1, x and y are shown as functions of u and v. If the result of differentiating y by v inside each of cell 3 and cell 4 is equal on the side shared by cell 3 and cell 4, the inclination will not change when crossing that side, so that sharing It can be said that a smooth line that crosses the side to be converted into a smooth line. If y is differentiated by v and u → 1 (right side) in cell 3, (dy / dv) (right side of cell 3) = − y ₂ + y ₃ and u → 0 (left side) in cell 4 Then, (dy / dv) (the left side of the cell 4) = − y ₂ + y ₃ and becomes equal. Similarly, if two cells sharing the upper side and the lower side are calculated with respect to the result obtained by differentiating x by u, the same result is obtained. Therefore, the correction result by this correction method is guaranteed to be smoothly continuous at the cell boundary.

Hereinafter, the present invention will be described with reference to examples and comparative examples. The present invention is not limited to the following examples, and includes various modifications within the technical scope of the present invention.

Example 1
The present embodiment relates to a coordinate correction method of a capacitively coupled coordinate input system that inputs using a pen. FIG. 6 shows the configuration of the coordinate input system. The coordinate indicator (input pen) 11 detects the coordinates (x, y) of the position indicated in the coordinate input area 13 of the input panel 12. The shape of the coordinate input area 13 of the input panel 12 is a rectangle. The surface resistor 14 was formed by forming a NESA (tin oxide) film in a rectangular shape on a square glass substrate. The resistive surrounding electrodes 15 were formed on the four sides of the coordinate input area 13 by screen printing with silver carbon ink. Further, the coordinate input area 13 is insulated with a glass coating agent to transmit signals by capacitive coupling between the input pen 11 and the surface resistor 14.

The four vertices of the coordinate input area 13 are set as drive electrodes 16 to 19, and lead lines 20 to 23 are connected to the drive electrodes 16 to 19, respectively. Lead wires 20-23 were connected to switches 24-27, respectively.

In order to detect the coordinates, an AC potential gradient is applied to the surface resistor 14 by the signal generator 28. In order to apply the potential gradient, first, one drive electrode 16 is selected from the drive electrodes 16 to 19, the switch 24 connected through the lead-out line 20 is connected to the output side of the signal generator 28, and the remaining voltage is applied. The switches 25 to 27 connected to the drive electrodes 17 to 19 are connected to the ground side. At this time, the AC signal level of the surface resistor 14 at a position close to the tip of the input pen 11 is transmitted to the input pen 11 through capacitive coupling, and further transmitted to the analog signal processing unit 30 through the cable 29. . Although not shown, the analog signal processing unit 30 includes an amplifier, a band pass filter, an AC / DC converter (AM detector), and the like, and outputs a DC signal level proportional to the input AC signal level. The A / D converter (analog / digital converter) 31 converts the DC signal level output from the analog signal processing unit 30 into a digital value and outputs it to the CPU 32.

The CPU 32 has a function of setting the connection of the switches 24 to 27 to an arbitrary combination (not shown), and when the data of the DC signal level output from the A / D converter 31 is read, next, the drive electrode 16 -19, the next drive electrode 17 is selected, only the corresponding switch 25 is connected to the output side of the signal generator 28, and the switches 24, 26 and 27 corresponding to the remaining drive electrodes 16, 18 and 19 are connected. Are connected to the ground side and similarly processed by the analog signal processing unit 30, and the CPU 32 reads the data output from the A / D converter 31.
The CPU 32 repeats this operation as many times as the number of drive electrodes, and calculates the coordinates of the indicated position of the input pen 11 based on those data. The coordinates can be calculated by Equation 3 assuming that the detected values when the drive electrodes 16 to 19 are selected are V _{16 to} V ₁₉ , respectively. The coordinates calculated in this way are obtained by adjusting the entire coordinate input area 13 to the range of −1 ≦ x ≦ 1, −1 ≦ y ≦ 1, and are converted into normalized reference coordinates once by the subsequent correction process. Finally, the coordinates are converted into coordinates corresponding to the physical size of the coordinate input area 13.

The detected coordinate value calculated by Expression 3 is output from the CPU 32 and is taken into the personal computer by serial communication.
On the other hand, the coordinate input area 13 is divided into grids having cells of appropriate constant horizontal and vertical lengths, and the coordinates detected when the input pen 11 is placed in advance at the respective grid points are used as reference detection coordinates. Was memorized in a personal computer. At this point, it was confirmed that all the cells of the lattice formed by the reference detection coordinates are convex quadrangles.

In this embodiment, the CPU 32 does not perform the correction process, but implements the correction process on the personal computer. And the coordinate which CPU32 output was taken in into the personal computer, and the result of the correction process was evaluated. The procedure of the correction process is as follows. First, as described above, the coordinates acquired in the personal computer exist in any cell or side of the grid formed by the reference detection coordinates stored in advance in the personal computer, and as described above, the four reference detection coordinates constituting the cell and The determination is made by the vector cross product calculation using the coordinates output by the CPU 32. This calculation is performed for all the cells in order, and ends when a cell whose coordinates output by the CPU 32 are inside or on the side is found.

Next, using the coordinates output by the CPU 32 and the four reference detection coordinates constituting the cell whose coordinates are inside or on the side, the procedure as shown in the flowcharts of FIGS. 3 and 4 is used. u and v are determined. Finally, the coordinates in the coordinate input area 13 are calculated using the position in the grid and the horizontal and vertical lengths of the cells.

FIG. 7A shows an example of the result of applying the correction process when the input pen 11 is moved across a plurality of cells. A dotted line shows 2 × 2 cells extracted from a grid formed by normalized reference coordinates. The solid line is the result of applying correction processing to the detected coordinates.

(Comparative Example 1)
Using the system of Example 1, the correction process of Patent Document 1 was applied to the same data to which the correction process was applied in Example 1. The results are shown in FIG.

As a result, in the configuration shown in Example 1, when the input pen 11 was moved across a plurality of cells, it could be corrected as a smooth line. On the other hand, in the first comparative example, especially the third coordinate from the top is actually on the line connecting the lattice points, but is corrected to the inside of the left cell, and the correction is not smooth at that portion. The result was obtained.
Therefore, the coordinate correction method according to the present invention always corrects the coordinates detected in the cells within the corresponding cells of the grid formed with the reference coordinates as the grid points, and continues across multiple cells. It was confirmed that the correction result can be corrected so that the correction result is smoothly continuous at the boundary of a plurality of cells.

DESCRIPTION OF SYMBOLS 1 Detection coordinate 2 Normalization correction coordinate 3, 4 Cell 11 Coordinate indicator 12 Input panel 13 Coordinate input area 14 Surface resistor 15 Resistive surrounding electrode 16, 17, 18, 19 Drive electrode 20, 21, 22, 23 Leader line 24, 25, 26, 27 Switch 28 Signal generator 29 Cable 30 Analog signal processor 31 A / D converter 32 CPU

Claims (1)

In a coordinate input system for detecting a position indicated by a coordinate indicator such as a finger or a pen, a coordinate correction method for correcting a detected coordinate value, wherein an input range is divided into a grid having at least a plurality of rectangular cells, Accurate reference coordinate values of all grid point positions and reference detection coordinate values actually detected when the position of the reference coordinates is indicated by the coordinate indicator are stored in advance, and the reference detection coordinates are The detected coordinates detected in a specific cell of the grid formed as a point are continuously inclined from one side to the other side for each of the two sets of opposite sides constituting the rectangular cell. A straight line that passes through the detected coordinates when the position is changed is determined, and in the corresponding cells of the lattice formed with the reference coordinates as the lattice points, the straight lines correspond to the two straight lines. Coordinate correction wherein the coordinate transformation into the two straight intersection coordinates.

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