WO2016121126A1

WO2016121126A1 - Two-dimensional code, two-dimensional code read device, and encoding method

Info

Publication number: WO2016121126A1
Application number: PCT/JP2015/052775
Authority: WO
Inventors: 信博知原; 宣隆木村
Original assignee: 株式会社日立製作所
Priority date: 2015-01-30
Filing date: 2015-01-30
Publication date: 2016-08-04

Abstract

Provided is a two-dimensional code, comprising a symbol region including a plurality of effective cells which retains user data, and a location detection pattern which is positioned externally to the symbol region. The location detection pattern signifies the location and range of the two-dimensional code. Each of the plurality of effective cells has a first color when retaining first information, and, when retaining second information, has a color, different from the first color, which is selected from a prescribed plurality of colors according to the location of the effective cell. The smallest value of a gap in the symbol region in a first direction of the effective cells which retain the second information and have the same color is one or more cells.

Description

Two-dimensional code, two-dimensional code reader, and encoding method

The present invention relates to a two-dimensional code, a two-dimensional code reader, and an encoding method.

In recent years, the use of barcode symbols has been expanding for various purposes. For example, barcode symbols are used for self-position recognition of mobile robots and information transmission in portable devices equipped with cameras.

As background art in this technical field, there are JP-A-7-254037 (Patent Document 1) and JP-A-63-255783 (Patent Document 2). Patent Document 1 describes a two-dimensional code in which an error correction code is embedded. According to the technique described in Patent Document 1, even when the two-dimensional code reader cannot read a part of the two-dimensional code due to dirt on the image, correct information is obtained by the error correction code embedded in the two-dimensional code. Can be read out. Patent Document 2 describes a one-dimensional code in which information about color change in the scan direction is provided by cells that are painted in a plurality of colors. According to the technique described in Patent Document 2, when a motion blur occurs in the scanning direction of a one-dimensional code, the two-dimensional code reader can read information correctly according to a predetermined color change pattern.

Japanese Patent Laid-Open No. 7-254037 Japanese Unexamined Patent Publication No. 63-255783

As mentioned above, barcode symbols are often taken by a high-speed moving camera such as a mobile robot or portable device. Since an image taken by a camera that moves at high speed causes motion blur throughout, there is a problem that barcode symbols cannot be read out correctly. Since the mobile robot reads the barcode symbol attached to the floor surface while moving at high speed, motion blur occurs. In addition, motion blur due to camera shake occurs in a barcode symbol photographed by a camera mounted on a handheld portable device.

FIG. 1 shows the effect of motion blur on the two-dimensional code of Patent Document 1. The two-dimensional code 20 has a motion blur with respect to the two-dimensional code 10. Since motion blur caused by the movement of the camera itself occurs in the entire image, the cut-out symbol 30 of the two-dimensional code 20 is crushed, and it is difficult to cut out the two-dimensional code area from the two-dimensional code 20. Even if the two-dimensional code area is cut out, many read errors occur in the information read for motion blur, so that even the error correction code cannot be corrected, and as a result, correct information cannot be read.

Although the technique described in Patent Document 2 improves the robustness of barcode symbols with respect to motion blur, it is a method of encoding information by color change in a one-dimensional scan direction. Can only be implemented in A one-dimensional code has a lower information density in principle than a two-dimensional code, and cannot contain much information. One embodiment of the present invention provides a barcode symbol that can be correctly recognized even from an image having motion blur of a predetermined width as a whole and can store information at high density.

The following configuration is employed in one aspect of the present invention. A two-dimensional code including a symbol area including a plurality of valid cells holding user data and a position detection pattern arranged outside the symbol area, wherein the position detection pattern is a position of the two-dimensional code. Each of the plurality of valid cells has a first color when holding the first information, and has a predetermined plurality of colors according to the position of the valid cell when holding the second information. In the symbol area, the minimum value of the interval in the first direction of the effective cells having the same color and having the color different from the first color selected from the first color is 1 cell or more. , Two-dimensional code.

According to one aspect of the present invention, it is possible to provide a barcode symbol that can be correctly recognized even from an image in which motion blur having a width of 1 cell or less has occurred as a whole and can store information at high density. Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

It is a figure which shows the influence of a motion blur in the conventional two-dimensional code. In Example 1, it is a figure showing an example of the structure of a two-dimensional code. In Example 1, it is a figure which shows an example of the structure of a position detection pattern. In Example 1, it is a figure which shows an example of the structure of a symbol area | region. In Example 1, it is a block diagram which shows the structural example of the barcode symbol reader. 6 is a flowchart illustrating an example of a barcode area detection process in the first embodiment. 6 is a flowchart illustrating an example of color separation processing in the first embodiment. In Example 1, it is a figure which shows the example of an outline | summary of a color separation algorithm. 5 is a flowchart illustrating an example of a cell reading process in the first embodiment. In Example 1, it is a figure which shows the example of the concept of a cell reading algorithm. 6 is a flowchart illustrating an example of a direction determination process in the first embodiment. In Example 1, it is a figure which shows the example of the concept of a direction determination algorithm. 6 is a flowchart illustrating an example of information decoding processing in the first embodiment. In Example 1, it is a figure which shows the example of the concept of an information decoding algorithm. In Example 1, it is a figure which shows the example of the order which references cell color information with respect to each direction of two-dimensional direction information. In Example 1, it is a figure which shows an example of the structure of a two-dimensional code. In Example 2, it is a figure which shows an example of the structure of a two-dimensional code. In Example 2, it is a figure which shows an example of the structure of a position detection pattern. In Example 2, it is a figure which shows an example of the structure of a symbol area | region. 10 is a flowchart illustrating an example of a barcode area detection process in the second embodiment. In Example 3, it is a figure explaining the example of an outline | summary of the self-position recognition of a mobile robot. In Example 3, it is a figure which shows an example of the structure of a two-dimensional code. In Example 3, it is a figure which shows an example of the structure of a position detection pattern. In Example 3, it is a figure which shows an example of the structure of a symbol area | region. In Example 4, it is a figure which shows an example of a cell color pattern. In Example 4, it is a flowchart which shows an example of an encoding process.

Hereinafter, an example of an embodiment of the present invention will be described with reference to the accompanying drawings. It should be noted that this embodiment is merely an example for realizing the present invention, and does not limit the technical scope of the present invention. In each figure, the same reference numerals are given to common configurations.

FIG. 2 shows an example of the structure of the two-dimensional code of this embodiment. The two-dimensional code 100 includes a position detection pattern 110 that defines the position and range of the two-dimensional code 100, and a symbol area 120 that is arranged inside the position detection pattern 110 and holds information. In FIG. 2 and other figures to be described later, the part indicated as R is red, the part indicated as G is green, the part indicated as B is blue, and the part filled with dots is Black, the color is not applied, and the portion where no character is written is white.

FIG. 3 shows an example of the structure of the position detection pattern of this embodiment. FIG. 3 shows only the position detection pattern 110 portion extracted from the two-dimensional code 100. The position detection pattern 110 includes, for example, a white frame 111 outside a rectangle having a predetermined width (a rectangle is a concept including a square) and a black frame 112 inside the rectangle having a predetermined width. The predetermined width indicates, for example, the length of one side of the cell when the cell is a square, and the length of the long side when the cell is a rectangle (a rectangle other than a square). The predetermined width may be longer than these lengths.

For example, when a motion blur with a blur width of 1 cell or less occurs, the color outside the two-dimensional code 100 is not mixed into the symbol area 120 inside the black frame 112, and the color of the symbol area 120 is the black frame 112. It does not mix outside. Therefore, the position and range of the two-dimensional code 100 can be detected by the position detection pattern 110 even when a motion blur having a blur width of 1 cell or less occurs. The motion blur whose blur width is equal to or less than x cells refers to a motion blur that extends from a certain cell up to x cells in a cell group in which cells are arranged without a gap.

It should be noted that the position detection pattern 110 may be a shape that can be detected even when motion blur occurs and can have a direction pattern that can be defined later. For example, in the position detection pattern 110, the color of the outer frame may be black and the color of the inner frame may be white. For example, the position detection pattern 110 may include a marker having a predetermined shape for position detection. The same applies to the position detection pattern 110 in other embodiments.

FIG. 4 shows an example of the structure of the symbol area of this embodiment. FIG. 4 shows only the symbol region 120 extracted from the two-dimensional code 100. The symbol area 120 has, for example, a rectangular structure composed of a plurality of basic cell patterns 150 connected in the same direction without gaps. The basic cell pattern 150 includes, for example, congruent rectangular cells 151 to 154 that are minimum units for holding information. The cell 151 is arranged at the upper left in the basic cell pattern 150, the cell 152 is arranged at the upper right in the basic cell pattern 150, the cell 153 is arranged at the lower right in the basic cell pattern 150, and the cell 154 is arranged at the lower left in the basic cell pattern 150.

The symbol area 120 includes cells 130 to 133 at four corners, and includes a direction pattern 160 indicating a direction of a two-dimensional code, that is, a rotation angle, and a code area 140 including other areas. Note that the direction pattern 160 does not have to be a cell at the four corners of the symbol area 120, and may be composed of, for example, four cells in the center of the symbol area 120. In addition, since the direction pattern 160 includes the cells 130 to 133 at the four corners, the color mixture from the outside of the direction pattern 160 by the motion blur is only black, so that the accuracy of the direction determination process described later is increased.

The basic cell pattern 150 has a structure in which 2 × 2 cells are arranged, and each cell in the basic cell pattern 150 is applied with, for example, black, or three primary colors of red, green, or blue, which are additive colors. ing. Each color applied to the cells in the basic cell pattern 150 may be any color that can separate the areas where the colors are generated even when the colors are mixed with each other. The cell 151, the cell 152, and the cell 154 hold user data, and the cell 153 does not hold user data. However, the cells constituting the direction pattern 160 do not hold user data. A cell holding user data is called a valid cell, and a cell not holding user data is called an invalid cell.

The color of the cell 151 is blue or black. When the color of the cell 151 is blue, the cell 151 holds 1 information, and when the color of the cell 151 is black, the cell 151 holds 0 information. The color of the cell 152 is green or black. When the color of the cell 152 is green, the cell 152 holds 1 information, and when the color of the cell 152 is black, the cell 152 holds 0 information. The color of the cell 154 is red or black. When the color of the cell 154 is red, the cell 154 holds 1 information, and when the color of the cell 154 is black, the cell 154 holds 0 information. The color of the cell 153 is black. For example, the cell 153 does not hold information. The cell 153 may hold, for example, a value of 1 or 0 as a fixed value.

In the symbol area 120, the plurality of basic cell patterns 150 are connected so that the colors of the effective cells holding one piece of adjacent information are not the same. That is, the plurality of basic cell patterns 150 are connected such that any two effective cells having the same color (red, blue, or green) are spaced by one cell in both the vertical and horizontal directions. Note that, in the symbol area 120, the minimum value of the interval in both the vertical and horizontal directions of the effective cell that holds one information and has the same color may be one cell or more. In addition, the space | interval of the cells in a certain direction points out the minimum thing among the lengths of the arbitrary virtual line segments of the said direction drawn from the point on the side of one cell to the point on the side of the other cell. . When there is a portion overlapping two cells, the interval between the two cells is assumed to be zero. As a result, when motion blur with a blur width of 1 cell or less occurs, only the colors of adjacent cells are mixed, and the colors of adjacent cells can be separated from each other, so that correct information is read from each cell. Can do.

For example, in the symbol area 120, each basic cell pattern 150 may be arranged with a predetermined interval from the adjacent basic cell pattern 150. In addition, each cell in the basic cell pattern 150 may be arranged at a predetermined interval from a cell in the same basic cell pattern 150. As the interval between the basic cell patterns 150 or between the cells in the basic cell pattern 150 is larger, the two-dimensional code 100 can accept a motion blur having a larger blur width. The smaller the interval is, the two-dimensional code 100 is. The information density is improved. The same applies to other embodiments described later.

The arrangement of the basic cell pattern 150 in the symbol area 120 of the present embodiment is not limited to the above-described arrangement, and may be any arrangement as long as the colors of the effective cells holding one adjacent information are not the same. That is, an interval of one cell is provided between effective cells of the same color that hold one information. The same applies to the arrangement of the cells 151 to 154 in the basic cell pattern 150. Further, the color of the invalid cell may be a color other than black as long as it is different from the color of the valid cell holding the information of 1.

In addition, the effective cell of the basic cell pattern 150 of the present embodiment holds 1 information by any of red, green, and blue. However, even when colors are mixed, colors that are correctly separated (for example, a camera described later) Other colors may be used as long as the color corresponds to the filter. Instead of red, blue, and green, for example, a combination of cyan, magenta, and yellow, a pattern generated from infrared light or ultraviolet light, or a color pattern determined by brightness, color, hue, etc. Information may be expressed. The above-described arrangement and colors are the same in the colors of the basic cell patterns of the other embodiments.

The effective cell in the basic cell pattern 150 of the present embodiment holds information of 1 when each cell is red, green, and blue, and 0 when black, but when each cell is red, green, and blue. In the case of 0 and black, information of 1 may be held. The same applies to the basic cell patterns of the other embodiments.

The direction pattern 160 includes, for example, cells 130 to 133 at four corners of the symbol area 120c. If the two-dimensional code 100b is in the correct orientation, the upper left cell 130 in the direction pattern 160 is blue, the upper right cell 132 is green, the lower left cell 131 is red, and the lower right cell 133 is black. The direction pattern 160 shown in the figure is composed of cells of four colors that may be included in the basic cell pattern 150. However, if the color of an effective cell holding one information is included, two or three colors are included. It may consist of colored cells. For example, one or two of the upper left cell 130, the upper right cell 132, and the lower left cell 131 may be black. The greater the number of colors included in the direction pattern 160, the more accurate the direction determination process described later.

Therefore, the barcode symbol reader described later can estimate the orientation when the two-dimensional code is rotated by reading the colors of the cells 130 to 133 corresponding to the position of the direction pattern 160. The code area 140 includes cells other than the direction pattern 160 of the symbol area 120. The valid cell in the code area 140 holds information of 1 and 0, and the information held by the two-dimensional code 100 is expressed by collecting the information of all the cells in the code area 140.

FIG. 5 shows an example of the configuration of the barcode symbol reader of this embodiment. The camera 210 is connected to the barcode symbol reader 200, acquires the captured image 300, and outputs it to the barcode symbol reader 200. Bar code symbol reader 200 receives captured image 300 from camera 210 and outputs two-dimensional code information 370 to data processor 220. The data processing device 220 receives the two-dimensional code information 370 from the barcode symbol reader 200, performs information processing, and presents it to the user or the like.

The barcode symbol reader 200 is configured on a computer including a CPU 201, a memory 202, and an input / output interface 203, for example. The CPU 201 includes a processor and / or a logic circuit that operates according to a program, inputs / outputs data, reads / writes data, and executes each program to be described later. The memory 202 temporarily loads and stores a program and data executed by the CPU 201, and holds each program and each data. The input / output interface 203 is an interface that inputs data from an external device such as the camera 210 and outputs data to the external device.

The memory 202 includes a frame buffer 230 and a barcode area detection unit 240, a color separation unit 250, a cell reading unit 260, a direction determination unit 270, and an information decoding unit 280, which are programs. The program is executed by the CPU 201 to perform a predetermined process using the memory 202 and the input / output interface 203. Therefore, in the present embodiment and the other embodiments, the description with the program as the subject may be the description with the CPU 201 as the subject. Alternatively, the process executed by the program is a process performed by a computer and a computer system on which the program operates.

The CPU 201 operates as a functional unit that realizes a predetermined function by operating according to a program. For example, the CPU 201 functions as a barcode area detection unit by operating according to the barcode area detection unit 240 as a program, and functions as a color separation unit by operating according to the color separation unit 250 as a program. Further, the CPU 201 also operates as a functional unit that realizes each of a plurality of processes executed by each program. A computer and a computer system are an apparatus and a system including these functional units.

The frame buffer 230 holds the captured image 300 input from the camera 210. The frame buffer 230 outputs the captured image 310 to the barcode area detection unit 240 and the color separation unit 250. The barcode area indicates an area occupied by the two-dimensional code 100. The barcode area detection unit 240 receives the captured image 310 from the frame buffer 230, detects the barcode area from the captured image 310, and uses the position and range of the two-dimensional code 100 as the two-dimensional code position information 320 as a color. Output to the separation unit 250.

FIG. 6 shows an example of barcode area detection processing by the barcode area detection unit 240. When the bar code area detection unit 240 inputs the captured image 310 from the frame buffer 230, the barcode area detection unit 240 executes binarization processing on the captured image 310 (S400). The barcode area detection unit 240 generates a binary image obtained by binarizing the captured image 310.

The barcode area detection unit 240 executes contour extraction processing on the binary image (S410). In the contour extraction process, the barcode area detection unit 240 extracts the contour of the black frame 112 of the position detection pattern 110 from the binary image, and acquires contour information. The barcode area detection unit 240 executes shape evaluation processing using the contour information (S420). In the shape evaluation process, the barcode area detection unit 240 determines whether the shape of the contour information is a convex shape or a concave shape, discards the contour information of the concave shape, and uses the contour information remaining without being discarded as the convex shape contour information. And

The barcode area detection unit 240 executes a contour length determination process (S430). In the contour length determination process, the barcode area detection unit 240 obtains the contour length for all the convex contours, and discards the convex contour information whose contour length is not within the predetermined contour range. Then, convex contour information whose contour length is within the contour range is set as two-dimensional code candidate contour information.

Note that the contour range is a range determined by the contour length upper limit and the contour length lower limit, and defines the range of the size of the two-dimensional code 100 that may appear in the captured image 310. For example, when the size of the two-dimensional code 100 to be photographed is limited, the difference between the contour length upper limit and the contour length lower limit is set to be small, that is, the contour range is set to be narrow. The code area detection process can be greatly speeded up.

Subsequently, the barcode area detection unit 240 executes a quadrangle approximation process (S440). In the quadrature approximation process, the barcode area detection unit 240 performs approximation to each quadrilateral for each of the two-dimensional code candidate contour information based on a predetermined approximation threshold, and a two-dimensional code candidate that cannot be approximated to a quadrangle. Discard the contour information. The approximate threshold value is set to a value representing the number of pixels having a blur width that can be generated by motion blur. When motion blur occurs, the position detection pattern 110 of the two-dimensional code 100 does not have a rectangular shape due to blurring. Therefore, the barcode area detection unit 240 can detect the position detection pattern 110 even when blurring occurs by performing the quadrangle approximation process.

The barcode area detection unit 240 executes position calculation processing (S450). In the position calculation process, the barcode area detection unit 240 calculates the coordinates of the four corners of the black frame 112 inside the position detection pattern 110 from the two-dimensional code contour information, and outputs it as the two-dimensional code position information 320.

Returning to the explanation of FIG. The color separation unit 250 inputs the photographed image 310 from the frame buffer 230 and the two-dimensional code position information 320 from the barcode region detection unit 240, respectively, and converts the two-dimensional code region in the photographed image 310 into red, blue, The green color images 340 are separated and output to the cell reading unit 260.

FIG. 7 shows an example of color separation processing. FIG. 8 shows an outline example of the color separation algorithm. The color separation unit 250 first performs a frame cutout process on the two-dimensional code 100 (S500). In the frame cutout process, the color separation unit 250 inputs the two-dimensional code position information 320 and cuts out a two-dimensional code image based on the coordinates of the four corners of the two-dimensional code position information 320. Subsequently, the color separation unit 250 executes a luminance value calculation process (S510). In the luminance value calculation process, the color separation unit 250 acquires, for each pixel of the two-dimensional code image, a red pixel value R, a green pixel value G, and a blue pixel value B of each pixel. The luminance value Y is calculated using the following formula 1.

Subsequently, the color separation unit 250 executes color extraction processing (S520). In the color extraction process, the color separation unit 250 performs a predetermined color threshold Cth, a red pixel value R, a green pixel value G, and a blue pixel value B for each pixel of the two-dimensional code image. , And the luminance value Y, a red region image sR620, a green region image sG630, and a blue region image sB640 are generated based on the values calculated by the following formula 2. The color separation unit 250 collectively outputs the generated area images of the respective colors to the cell reading unit 260 as a color image 340.

According to the color separation algorithm according to the present embodiment, even when motion blur occurs in the two-dimensional code image 600 and colors are mixed as in the two-dimensional code image 610, the color separation unit 250 can perform the two-dimensional code. The image 610 can be separated into a color image 340 composed of a red region image sR620, a green region image sG630, and a blue region image sB640.

Returning to the explanation of FIG. The cell reading unit 260 receives the color image 340 from the color separation unit 250, derives cell color information 350 indicating which color of red, blue, or green is reacting at each cell position in the barcode area, Cell color information 350 is output to direction determining section 270 and information decoding section 280.

FIG. 9 shows an example of the cell reading process. FIG. 10 shows an example of the concept of the cell and reading algorithm. The cell reading unit 260 receives the color image 340 from the color separation unit 250 and executes a cell reading process. First, the cell reading unit 260 performs cell division processing (S700). In the cell division process, the cell reading unit 260 divides the color image 340 input from the color separation unit 250 into cells according to a predetermined two-dimensional code size, and generates a divided color image 800 for each color. The two-dimensional code size is a value that defines the entire two-dimensional code 100, the size of each cell of the two-dimensional code 100, and the number of vertical and horizontal cells of the two-dimensional code 100. It is assumed that it is prescribed in advance.

The cell reading unit 260 executes the effective cell ratio calculation process 710 (S710). In the effective cell ratio calculation process 710, the cell reading unit 260 acquires the effective pixel number E and the cell pixel number C from each cell of the divided color image 800, and calculates the effective cell ratio eR by the following equation 3, for example.

Subsequently, the cell reading unit 260 executes a cell information reading process (S720). In the cell information reading process 720, the cell reading unit 260 calculates the cell color determination result CCI in each cell by, for example, the following equation 4. Specifically, the cell color determination result CCI in each cell of each cell information color is 1 when the effective cell ratio eR is larger than the cell determination threshold Rth, and 0 otherwise. The cell reading unit 260 outputs cell color information 350 including cell color determination results CCI in all cells of each color.

Returning to the explanation of FIG. The direction determining unit 270 receives the cell color information 350 from the cell reading unit 260, determines the two-dimensional code direction from the color information of the cell corresponding to the position of the direction pattern 160, and the information decoding unit as the two-dimensional code direction information 360 Output to 280.

FIG. 11 shows an example of direction determination processing. FIG. 12 shows an example of the concept of the direction determination algorithm. The direction determining unit 270 first performs a voting process (S900). In the voting process, the direction determination unit 270 refers to the color information of the cell position of the direction pattern 160 of the cell color information 350 and performs voting on the direction patterns of the four direction candidates that match the cell holding the information of 1. The voting result is set as direction voting information 1000 (S900). The bar code symbol reading apparatus 200 holds information on the direction patterns of the four direction candidates in advance.

A specific example of the voting process will be described with reference to FIG. In the example of FIG. 12, only the lower left cell among the cells of the direction pattern 160 of the red cell color information 350 holds 1 information. Since the direction in which the lower left cell is red in the direction voting information 1000 is the direction 1, the direction determination unit 270 votes one vote in the direction 1. Similarly, the direction determination unit 270 refers to the direction pattern 160 of the green cell color information 350 and votes one direction in the direction 1 in which the cell holding the information of 1, that is, the upper right cell is green. The direction determining unit 270 refers to the direction pattern 160 of the blue cell color information 350, and holds one piece of information in the direction 1 and the direction 4 in which the cells holding one information, that is, the upper left cell and the lower left cell are blue. Vote one by one.

Subsequently, the direction determining unit 270 executes a cell validity determination process (S910). In the cell validity determination process, the direction determining unit 270 determines that all of the four direction voting information 1000 is smaller than a predetermined direction voting threshold or that two or more directions are equal to or higher than a predetermined direction voting threshold. In this case, it is determined that the two-dimensional code is erroneously detected, that is, it is determined that the two-dimensional code is not included in the captured image 310, and the process is interrupted. When the direction determining unit 270 determines that the two-dimensional code is erroneously detected in the above case, the processing speed and the detection accuracy of the two-dimensional code are improved.

The direction determination unit 270 performs a direction determination process in cases other than these (S920). In the direction determination process, the direction determination unit 270 outputs, as the two-dimensional code direction information 360, a direction that is equal to or greater than the direction vote threshold among the four-direction direction vote information 1000. In FIG. 12, the direction voting threshold is set to 3 in advance, but may be designated by the user or the like from outside the apparatus.

Returning to the explanation of FIG. The information decoding unit 280 receives the cell color information 350 from the cell reading unit 260 and the two-dimensional code direction information 360 from the direction determining unit 270, decodes the two-dimensional code information, and converts the two-dimensional code information 370 into the data processing device. To 220.

FIG. 13 shows an example of the information decoding process. FIG. 14 shows an example of the concept of the information decoding algorithm. The information decoding unit 280 performs a cell reading process (S1100). In the cell reading process, the information decoding unit 280 reads the cells of the cell color information 350 for each color in the order corresponding to the two-dimensional code direction information 360, and outputs two-dimensional code information 370 that summarizes the decoding results for each color.

FIG. 15 shows an example of the order of reading each cell of the cell color information 350 according to the two-dimensional code direction information 360. The cell reading unit 260 reads cells in the order corresponding to the direction specified by the two-dimensional code direction information 360 in the cell reading process of step S1100. For example, the bar code symbol reading apparatus 200 holds in advance the information shown in FIG. 15, that is, information indicating the correspondence between the cell position and the color in each direction, and information indicating the order of reading each cell. .

FIG. 16 shows an example of the structure of the two-dimensional code in this embodiment. The two-dimensional code 2010 is different from the two-dimensional code 100 in that the position detection pattern white and black are reversed, and in the symbol area, cells holding 0 information and invalid cells are white.

Also, as in the two-dimensional code 2020, the color of the lower right cell of the basic cell pattern may be white or black. At this time, information 1 may be held when the color of the lower right cell is white, and information 0 may be held when the cell is black. The two-dimensional code 2010 can hold 1-bit information also in the lower right cell, that is, the lower right cell is also an effective cell, so the two-dimensional code 2020 can realize a high information density.

The barcode symbol reader 200 according to the present embodiment can read correct information even from a two-dimensional code in a captured image generated by a motion blur that is captured by a camera moving at a high speed, for example. Further, the two-dimensional code 100 can realize a high information density on the principle of the two-dimensional code.

FIG. 17 shows an example of the structure of the two-dimensional code of this embodiment. The two-dimensional code 1200 of this embodiment includes a position detection pattern 1210 that defines the position and range of the two-dimensional code 1200, and a symbol area 1220 that is arranged inside the position detection pattern 1210 and holds information. The shape of the two-dimensional code 1200 of the present embodiment is, for example, a triangle, and the shape of each cell included in the symbol area 1220 is, for example, a regular hexagon.

FIG. 18 shows an example of the structure of the position detection pattern of this embodiment. FIG. 18 shows only the position detection pattern 1210 of the two-dimensional code 1200 extracted. The position detection pattern 1210 includes, for example, an outer triangular white frame 1300 having a predetermined width, and an inner triangular black frame 1310 having a thinnest portion having a predetermined width. The predetermined width may be, for example, the length of one side of a regular hexagonal cell.

In the position detection pattern 1210, even when motion blur with a blur width of 1 cell or less occurs, colors other than the two-dimensional code 1200 are not mixed in the symbol area 1220 inside the black frame 1310, and the color of the symbol area 1220 is It does not mix outside the black frame 1310. Therefore, the position and range of the two-dimensional code 1200 can be detected by the position detection pattern 1210 even when a motion blur having a blur width of 1 cell or less occurs.

It should be noted that the position detection pattern 1210 may be a shape that can be detected even when motion blur occurs, and may be a shape that can define a direction pattern described later. The shapes of the white frame 1300 and the black frame 1310 of the position detection pattern 1210 may be regular hexagons, for example.

FIG. 19 shows an example of the structure of the symbol area in this embodiment. FIG. 19 shows only the symbol region 1220 portion extracted from the two-dimensional code 1200. The symbol area 1220 has, for example, a structure in which a plurality of basic cell patterns 1400 are connected in the same direction without a gap. The basic cell pattern 1400 includes, for example, congruent regular hexagonal cells 1401 to 1403 that are minimum units for holding information.

The basic cell pattern 1400 is configured, for example, by connecting one cell so as to share one side with each of the other two cells. The cell 1401 is arranged in the upper part of the basic cell pattern 1400, the cell 1402 is arranged in the lower part of the basic cell pattern 1400, and the cell 1403 is arranged in the left part of the basic cell pattern 1400.

The symbol area 1220 is composed of a direction pattern 1420 including corner cells 1430 to 1432 and a code area 1440 including other areas. Note that the cell at the corner of the symbol region 1220 indicates a cell having the maximum number of sides facing the position detection pattern 1210 among the cells included in the symbol region 1220c. Note that the position detection pattern 1210 does not have to be a cell at the corner of the symbol area 1220, and may be any basic cell pattern 1400 included in the symbol area 1220, for example.

The basic cell pattern 1400 has a structure in which regular hexagonal cells are arranged, and each of the cells in the basic cell pattern 1400 is applied with black, or one of three primary colors red, green, or blue, which is an additive color mixture. . Each color applied to the cells in the basic cell pattern 1400 may be any color that can separate the areas where the colors are generated even when the colors are mixed. The cells 1401 to 1403 all hold user data. However, the cells constituting the direction pattern 1420 do not hold user data.

The color of the cell 1402 is blue or black. When the color of the cell 1402 is blue, the cell 1402 holds 1 information, and when the color of the cell 1402 is black, the cell 1402 holds 0 information. The color of the cell 1401 is green or black. When the color of the cell 1401 is green, the cell 1401 holds 1 information, and when the color of the cell 1401 is black, the cell 1401 holds 0 information. The color of the cell 1403 is red or black. When the color of the cell 1403 is red, the cell 1403 holds 1 information, and when the color of the cell 1403 is black, the cell 1403 holds 0 information.

In the symbol area 1220, the plurality of basic cell patterns 1400 are connected so that the colors of the effective cells holding one piece of adjacent information are not the same. As a result, when motion blur with a blur width of 1 cell or less occurs, only the colors of adjacent cells are mixed, and the colors of adjacent cells can be separated from each other, so that correct information is read from each cell. Can do.

Since the cells included in the basic cell pattern 1400 of the present embodiment are regular hexagons, the basic cell pattern 1400 can be arranged so that adjacent cells have different colors even if the symbol area 1220 does not include invalid cells. Therefore, the two-dimensional code 1200 of the present embodiment can realize a high information density.

The direction pattern 1420 includes cells 1430 to 1432 at the corners of the symbol area 1220. If the two-dimensional code 1200b is in the correct orientation, the upper cell 1431 in the direction pattern 1420 is green, the lower right cell 1432 is blue, and the lower left cell 1430 is red. The direction pattern 1420 shown in the drawing is composed of cells of three colors, but may be composed of cells of two colors, for example. Therefore, the barcode symbol reader 200 can estimate the direction when the two-dimensional code is rotated by reading the colors of the cells 1430 to 1432 corresponding to the position of the direction pattern 1420.

The code area 1440 includes cells other than the direction pattern 1420 of the symbol area 1220. Each cell in the code area 1440 holds information of 1 and 0, and the information held by the two-dimensional code 1200 is represented by collecting the information of all the cells in the code area 1440.

Hereinafter, the barcode symbol reading process in this embodiment will be described. In the present embodiment, the difference from the barcode symbol reading process of the first embodiment will be described. FIG. 20 shows an example of barcode area detection processing in the present embodiment. The binarization process to the contour length determination process, that is, the processes from step S400 to step S430 are the same as those in FIG.

The barcode area detection unit 240 executes a triangle approximation process (S1540) following the contour length determination process (S430). In the triangle approximation process, the barcode area detection unit 240 performs approximation to a triangle based on a predetermined approximation threshold for each piece of 2D code candidate outline information, and a 2D code candidate outline that cannot be approximated to a triangle. Discard information.

When the motion blur occurs, the position detection pattern 1210 of the two-dimensional code 1200 is not in a triangular shape due to blurring. Therefore, the barcode area detection unit 240 can detect the position detection pattern 1210 even when blurring occurs by performing the triangle approximation process. Subsequently, the barcode area detection unit 240 executes a position calculation process (S1550). In the position calculation process, the barcode area detection unit 240 calculates the coordinates of the three corners of the position detection pattern 1210 and outputs the calculated coordinates as two-dimensional code position information 320.

Note that the color separation process and the cell reading process of the present embodiment are the same as those of the first embodiment even if the bar code symbol has a different shape, and thus the description thereof is omitted here.

Hereinafter, the direction determination process in the present embodiment will be described with reference to FIG. In the voting process (S900), the direction determination unit 270 refers to the color information of the cell position of the direction pattern of the cell color information, performs voting on each direction pattern of the three matching direction candidates, and determines the voting result as the direction. Voting information.

In the cell validity determination process (S910), the direction determining unit 270 has all three direction voting information smaller than a predetermined direction voting threshold, or two or more directions are equal to or higher than a predetermined direction voting threshold. If it is determined that the two-dimensional code is erroneously detected, the process is interrupted. The direction determination unit 270 performs direction determination processing in cases other than these. In the direction determination process (S9620), the direction determination unit 270 outputs, as two-dimensional code direction information, a direction that is equal to or greater than the direction vote threshold among the three-direction direction vote information.

Note that the information decoding process of the present embodiment is the same as that of the first embodiment even if the shape of the bar code symbol is different, and thus the description thereof is omitted here.

Since the cell shape of the two-dimensional code 1200 of this embodiment is a regular hexagon, it can be arranged so that the colors between adjacent cells are different without using invalid cells. Therefore, the two-dimensional code 1200 of the present embodiment can increase the information density per area compared to the two-dimensional code 100 of the first embodiment.

FIG. 21 shows a schematic example of self-position recognition of a mobile robot, which is an example of a two-dimensional code operation mode. For example, the mobile robot 1700 and the mobile robot 1710 execute a given task while autonomously moving. Two-

dimensional codes

1730 and 1750 are affixed to the floor 1720. The mobile robot 1700 and the mobile robot 1710, for example, recognize a two-dimensional code on the floor surface with a camera facing the floor surface installed on the mobile robot 1700 and move the encoded position information in the two-dimensional code. Self-position recognition is performed by reading.

The two-dimensional code 1730 is attached to an area where the mobile robot 1700 and the mobile robot 1710 can move from a plurality of directions. Therefore, since the two-dimensional code 1730 needs to correspond to motion blur generated in various directions, for example, it may have the same structure as the two-dimensional code shown in the first and second embodiments. On the other hand, the two-dimensional code 1750 is affixed to an area surrounded by the shelf 1740, that is, an area where the mobile robot 1700 and the mobile robot 1710 can move from only one direction. Accordingly, the two-dimensional code 1750 only needs to be able to handle motion blur that occurs only in one direction.

In this embodiment, a two-dimensional code suitable for dealing with motion blur that occurs only in one direction, such as a two-dimensional code 1750, will be described. FIG. 22 shows an example of the structure of the two-dimensional code of the present embodiment. The two-dimensional code 1800 includes a position detection pattern 1820 that defines the position and range of the two-dimensional code 1800, and a symbol area 1810 that holds information.

FIG. 23 shows an example of the structure of the position detection pattern of this embodiment. FIG. 23 shows only the position detection pattern 1820 portion extracted from the two-dimensional code 1800. The position detection pattern 1820 includes an outer rectangular white frame 1900 having a predetermined width and an inner black frame 1910 having a predetermined width. The predetermined width indicates, for example, a length twice as long as one side of the cell when the cell is a square, and a length twice as long as the long side when the cell is a rectangle. The predetermined width may be longer than these lengths.

When a motion blur with a blur width of 2 cells or less occurs in the position detection pattern 1820, the direction of motion blur generation is limited to the moving direction of the camera, so colors other than the two-dimensional code 1800 are symbol areas inside the black frame 1910. The color of the symbol area 1810 is not mixed outside the black frame 1910. Accordingly, the position and range of the two-dimensional code 1800 can be detected by the position detection pattern 1820.

FIG. 24 shows an example of the structure of the symbol area of this embodiment. FIG. 24 shows only the symbol area 1810 portion of the two-dimensional code 1800 extracted. The symbol area 1810 is, for example, a rectangle composed of a plurality of basic cell patterns 1860 that are connected in such a way that the effective cells arranged in the vertical direction (the direction perpendicular to the camera movement direction in the figure) in the same direction with no gaps are one color. It has a structure. The basic cell pattern 1860 is composed of, for example, congruent rectangular cells 1970 to 1972 which are minimum units for holding information. The cell 1970 is arranged on the left side in the basic cell pattern 1860, the cell 1971 is arranged in the center in the basic cell pattern 1860, and the cell 1972 is arranged on the right side in the basic cell pattern 1860. The symbol area 1810 includes a direction pattern 1980 composed of cells 1950 to 1953 at four corners, and a code area 1940 composed of other areas.

The basic cell pattern 1960 has a structure in which, for example, three cells are arranged, and each cell in the basic cell pattern 1960 is applied with, for example, black, or three primary colors of red, green, or blue, which are additive colors. ing. Each color applied to the cells in the basic cell pattern 1960 may be any color that can separate the region where each color is colored even when the colors are mixed. Cells 1970 to 1972 hold user data. However, the cells constituting the direction pattern 1980 do not hold user data.

The color of the cell 1970 is red or black. When the color of the cell 1970 is red, the cell 1970 holds 1 information, and when the color of the cell 1970 is black, the cell 1970 holds 0 information. The color of the cell 1971 is green or black. When the color of the cell 1971 is green, the cell 1971 holds 1 information, and when the color of the cell 1971 is black, the cell 1971 holds 0 information. The color of the cell 1972 is blue or black. When the color of the cell 1972 is blue, the cell 1972 holds 1 information, and when the color of the cell 1972 is black, the cell 1972 holds 0 information.

In the symbol area 1220, a plurality of basic cell patterns 1960 are connected so that a cell holding one information adjacent in the camera moving direction and a cell holding one information adjacent thereto are not the same in color. Yes. As a result, when motion blur with a blur width of 2 cells or less occurs in the camera movement direction, only the colors of the adjacent cell and the two adjacent cells are mixed, and the colors of the mixed cells can be separated from each other. Therefore, correct information can be read from each cell. For example, if the number of cells of the basic cell pattern 1960 is increased and the same number of colors as the number of cells are applied, the allowable blur width of the motion blur becomes longer according to the number of colors.

The direction pattern 1980 includes cells 1950 to 1953 at the four corners of the symbol area 1810. If the two-dimensional code 1800 has the correct orientation, the upper left cell 1950 and lower left cell 1951 in the direction pattern 1980 are red, and the upper right cell 1952 and lower right cell 1953 in the direction pattern 1980 are green. Therefore, the barcode symbol reader 200 can estimate the direction when the two-dimensional code is rotated by reading the colors of the cells 1950 to 1952 corresponding to the position of the direction pattern 1980.

The code area 1940 includes cells other than the direction pattern 1980 of the symbol area 1810. Each cell in the code area 1940 holds information of 1 and 0, and the information held by the two-dimensional code 1800 is expressed by collecting the information of all the cells in the code area 1940. Note that when the vertical width (direction perpendicular to the camera movement direction in the figure) in the two-dimensional code 1800 of this embodiment is one cell, it can be handled as a one-dimensional code substantially.

Note that the barcode symbol reading process in the present embodiment is the same as that in the first embodiment, and a description thereof will be omitted here.

The two-dimensional code 1800 of this embodiment is composed of basic cell patterns 1960 in which the colors of the cells located in the camera movement direction are different colors. In applications where it is known that the moving direction of the camera is one direction, the two-dimensional code 1800 of this embodiment can be used, even if the number of colors used is the same as the two-dimensional code of other embodiments. A motion blur with a wide blur is acceptable. Therefore, the two-dimensional code 1800 of the present embodiment realizes downsizing of the two-dimensional code, and the barcode symbol reader 200 can correctly read the barcode even from an image taken by a camera that moves faster. Can do.

This embodiment shows an example of a process for encoding input data into the two-dimensional code 100 including the symbol area 120 made up of 6 × 6 square cells in the first embodiment. Specifically, the processing for determining the color of the effective cell in the symbol area 120 from the input data will be mainly described.

The encoding of the present embodiment is performed by, for example, an encoding device 2501 (not shown) having a hardware configuration similar to that of the barcode symbol reading device 200 of FIG. That is, for example, the processor performs an encoding process by operating as a function unit that realizes a predetermined function by operating according to a predetermined program.

FIG. 25 shows an example of a cell color pattern 2502 indicating the correspondence between each digit of the input numeric string, the position of the valid cell that stores the value of the digit, and the color of the valid cell at that position. The cell color pattern 2502 is stored in advance in the encoding device 2501, for example. A digit column 2503 indicates the digit number of the numeric string, that is, the position of the numeric value in the numeric string. The cell position column 2504 indicates the cell position of a valid cell that stores the value of the corresponding digit number. The cell position (x, y) in the figure means the cell that is x right and y lower than the cell in the upper left corner of the symbol area (the cell indicated as “B” in the two-dimensional code 100 in FIG. 15). To do. A color column 2505 indicates the color of the valid cell at the corresponding cell position when the value of the corresponding digit is 1. Note that the cell color pattern 2502 is determined so that an interval of one cell is provided between valid cells of the same color that hold one piece of information.

Note that the encoding device 2501 determines the color of the cell holding the information of 0, the position and color of the invalid cell, the position and color of the position detection pattern 110, and the position and color of each cell constituting the symbol area 120. Are held in advance. In this embodiment, it is assumed that the color of the cell holding the information of 0 and the color of the invalid cell are both black. The position of the invalid cell is assumed to be the position of the black cell in the symbol area 120 of the two-dimensional code 100 shown in FIG. The position detection pattern 110 is located outside the symbol area 120, and includes a white frame 111 outside the width of one cell and a black frame 112 inside the rectangle having a width of one cell. The direction pattern 160 is composed of cells at the four corners of the symbol area 120, and the upper left cell is blue, the upper right cell is green, the lower left cell is red, and the lower right cell is black.

FIG. 26 shows an example of the encoding process. The encoding device 2501 accepts data input (S2601). Specifically, the encoding device 2501 accepts an input of a 24-digit numeric string expressed in binary numbers, for example. The encoding device 2501 may generate a 24-digit numerical sequence by receiving a numerical sequence of less than 24 digits and adding a fixed value to the input.

The encoding device 2501 refers to the cell color pattern 2502 (S2602). The encoding apparatus determines the color of the effective cell at the cell position corresponding to the value of each digit of the input numerical sequence according to the cell color pattern 2502 (S2603). Specifically, the encoding device 2501 determines that the color of the effective cell at the cell position corresponding to the digit indicated by the cell color pattern 2502 is black when the value of a digit in the input numerical sequence is 0. To do.

In addition, when the value of a certain digit of the input numeric string is 1, the encoding device 2501 indicates the color of the effective cell at the cell position corresponding to the digit indicated by the cell color pattern 2502 by the cell color pattern 2502. The color corresponding to the indicated digit is determined. In the example of FIG. 25, for example, when the 0th digit of the input numerical sequence is 1, the color of the cell at the cell position (1, 0) is determined to be green, and the first digit of the input numerical sequence is Is 1, the color of the cell at the cell position (2, 0) is determined to be blue. The encoding method of the present embodiment can generate a two-dimensional code that allows motion blur with a blur width of one cell or less.

In addition, this invention is not limited to the above-mentioned Example, Various modifications are included. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Further, a part of the configuration of a certain embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of a certain embodiment. Further, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

In addition, each of the above-described configurations, functions, processing units, processing means, and the like may be realized by hardware by designing a part or all of them with, for example, an integrated circuit. Each of the above-described configurations, functions, and the like may be realized by software by interpreting and executing a program that realizes each function by the processor. Information such as programs, tables, and files that realize each function can be stored in a memory, a hard disk, a recording device such as an SSD (Solid State Drive), or a recording medium such as an IC card, an SD card, or a DVD.

Also, the control lines and information lines indicate what is considered necessary for the explanation, and not all the control lines and information lines on the product are necessarily shown. Actually, it may be considered that almost all the components are connected to each other.

Claims

A symbol area containing a plurality of valid cells holding user data;
A two-dimensional code including a position detection pattern arranged outside the symbol area,
The position detection pattern indicates the position and range of the two-dimensional code,
Each of the plurality of valid cells is
When holding the first information, it has the first color,
When holding the second information, it has a color different from the first color, selected from a plurality of predetermined colors according to the position of the valid cell,
A two-dimensional code in which, in the symbol area, the minimum value of the interval in the first direction of the effective cells holding the second information and having the same color is one cell or more.
The two-dimensional code according to claim 1,
The symbol area has a rectangular shape in which a plurality of basic cell patterns are arranged in the same direction,
Each of the plurality of basic cell patterns is composed of two congruent rectangular cells in the vertical and horizontal directions,
The plurality of basic cell patterns includes a plurality of first basic cell patterns including three valid cells and one invalid cell that does not hold user data.
The effective cells holding the second information of each of the plurality of basic cell patterns have different colors,
The invalid cell has a second color different from the plurality of colors of the valid cell holding the second information.
The two-dimensional code according to claim 2,
The first color is black or white;
The plurality of colors includes red, green, and blue,
A two-dimensional code in which the color of the invalid cell is black or white.
The two-dimensional code according to claim 1,
The symbol area includes a plurality of cells that do not hold user data, and includes a direction pattern indicating a rotation angle of the two-dimensional code,
The direction pattern includes a first cell having a color selected from the plurality of colors and a second cell having a color different from the first cell.
The two-dimensional code according to claim 4,
The two-dimensional code in which the cells included in the direction pattern have different colors selected from the plurality of colors.
The two-dimensional code according to claim 2,
The symbol area includes four cells that do not hold user data, and includes a direction pattern indicating a rotation angle of the two-dimensional code,
The direction pattern includes a first cell having a color selected from the plurality of colors, and a second cell having a color different from the first cell,
Each of the cells included in the direction pattern is a cell other than the cells of the plurality of first basic cell patterns,
Each of the four cells is a two-dimensional code arranged at four corners of the symbol area.
The two-dimensional code according to claim 1,
The symbol area has a rectangular shape in which a plurality of basic cell patterns are arranged in the same direction,
Each of the plurality of basic cell patterns is composed of two congruent rectangular cells in the vertical and horizontal directions,
The plurality of basic cell patterns includes a plurality of second basic cell patterns composed of four effective cells,
A valid cell that holds the second information of each of the plurality of basic cell patterns is a two-dimensional code having different colors.
The two-dimensional code according to claim 7,
The first color is one of black and white;
The plurality of colors are red, green, blue, and the other of black and white.
The two-dimensional code according to claim 1,
The symbol area is composed of a plurality of basic cell patterns arranged in the same direction,
Each of the plurality of basic cell patterns is
It consists of three congruent regular hexagonal cells,
Each of the three congruent regular hexagonal cells is configured to share one side with each of the other two regular hexagonal cells,
The plurality of basic cell patterns includes a plurality of third basic cell patterns composed of three effective cells,
A valid cell that holds the second information of each of the plurality of basic cell patterns is a two-dimensional code having different colors.
The two-dimensional code according to claim 1,
The symbol area has a rectangular shape in which a plurality of basic cell patterns are arranged in the same direction,
Each of the plurality of basic cell patterns is composed of three congruent rectangular cells arranged in one direction,
The plurality of basic cell patterns includes a plurality of fourth basic cell patterns composed of three effective cells,
A valid cell that holds the second information of each of the plurality of basic cell patterns is a two-dimensional code having different colors.
A two-dimensional code reader that receives input of an image composed of a plurality of pixels and reads information held by a two-dimensional code in the image,
The two-dimensional code is
A symbol area containing a plurality of valid cells holding user data;
A position detection pattern arranged outside the symbol area,
The position detection pattern indicates the position and range of the two-dimensional code,
The two-dimensional code reader is
A barcode area detection unit that detects the position detection pattern from the image, and identifies the position and range of the two-dimensional code from the detected position detection pattern;
A color separation unit that generates pixel color information indicating a color of each pixel based on a pixel value of each of the plurality of colors in each pixel in the two-dimensional code;
The two-dimensional code is divided into cells of a predetermined size, and is included in each cell based on the total number of pixels in each cell and the number of pixels in each of the plurality of colors in each cell indicated by the pixel color information. A cell reading unit for generating cell color information indicating the above colors;
A cell position of a valid cell; a color of a valid cell holding first information; and a correspondence between a cell position of the valid cell and a color of a valid cell holding second information. The minimum value of the interval in the first direction of the effective cells that hold the two information and have the same color is a predetermined value, cell color correspondence information,
A two-dimensional code reader, comprising: an information decoding unit that decodes information held by each valid cell based on the color of each valid cell indicated by the cell color information and the cell color correspondence information.
The two-dimensional code reader according to claim 11,
The two-dimensional code is
The symbol area includes a plurality of cells that do not hold user data, and includes a direction pattern indicating a rotation angle of the two-dimensional code,
The direction pattern includes a first cell having a color selected from the plurality of colors, and a second cell having a color different from the first cell,
The two-dimensional code reader is
A direction determining unit that estimates a rotation angle of the two-dimensional code;
Rotation direction candidate information indicating correspondence between a plurality of rotation angles of the two-dimensional code and a color arrangement of cells of the direction pattern at each of the plurality of rotation angles;
The direction determining unit
With reference to the cell color information, one or more colors included in each cell of the direction pattern in the symbol area are specified,
Each of the color arrangements is compared with one or more colors of each of the direction pattern cells in the symbol area, and the number of votes for each of the color arrangements is determined according to the number of matching cell positions and colors. And
A two-dimensional code reading device that estimates a rotation angle of a color arrangement having the maximum number of votes as a rotation angle of the two-dimensional code.
The two-dimensional code reader according to claim 12,
When the number of votes at all rotation angles included in the rotation direction candidate information is less than a first threshold, or when the number of votes at a plurality of rotation angles is greater than or equal to the first threshold, A two-dimensional code reader that determines that the two-dimensional code is not included therein.
The two-dimensional code reader according to claim 11,
The color separation unit is
Based on the pixel value of each of the plurality of colors in each pixel in the two-dimensional code, the luminance value of each pixel is calculated,
A two-dimensional code reading device that determines, for each of the plurality of colors, that the pixel has the color when the difference between the luminance value of each pixel and the pixel value of the color of the pixel is greater than a second threshold value.
A method of encoding user data into a symbol area included in a two-dimensional code,
The symbol area includes a plurality of valid cells that store user data;
Each of the plurality of valid cells is
Stores numbers,
If it holds the first number, it has the first color,
In the case of holding the second numerical value, it has a color different from the first color, selected from a plurality of predetermined colors according to the position of the effective cell,
The method
Obtaining cell position information indicating the relationship between the position of the numerical value in the numerical sequence and the cell position of the valid cell storing the numerical value;
The first color and the correspondence between the cell position of the effective cell and the color of the effective cell holding the second numerical value, and the first direction of the effective cell holding the second numerical value and having the same color The minimum value of the interval in the cell color correspondence information that is greater than or equal to a predetermined value,
Receiving user data that is a numerical string composed of a plurality of numerical values, each of the plurality of numerical values being the first numerical value or the second numerical value;
Determining a cell position of each of the plurality of numerical values of the user data with reference to cell position information;
A method of determining a color of each of the effective cells storing the plurality of numerical values with reference to cell color correspondence information based on a cell position and a numerical value of each of the effective cells.