JP2007148558A - Two-dimensional code, two dimensional code detection method and two-dimensional code detection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To highly densely embed bit information in a two-dimensional code for detecting the two-dimensional code from not only a direction which is almost counter to the two-dimensional code but also an arbitrary direction. <P>SOLUTION: This two-dimensional code is provided with the outside shape of a square which can be identified from a background based on brightness or color, wherein the inside of the two-dimensional code is divided into specific sizes by setting a fixed interval in the outer periphery of its inside, and information is expressed according to the brightness or color of each of the divided regions. In this case, the respective regions obtained by dividing the inside of the two-dimensional code are made adjacent to each other so that a hexagonal can be configured. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a configuration of a two-dimensional code that can be detected from an image, and a method and apparatus for detecting a two-dimensional code from an image.

[Prior art 1]
A two-dimensional code called “MaxiCode” shown in FIG. 10 is conventionally known. This two-dimensional code has a structure in which a central black area and a black area and a white area having different radii are arranged concentrically and minute regular hexagonal areas are regularly arranged around the area. By representing each regular hexagon as black or white, binary information is expressed, and the information is read out by photographing it with a camera. Hereinafter, this is referred to as a two-dimensional code 1.

  Further, the two-dimensional code shown in FIGS. 11 and 12 is also conventionally known. These two-dimensional codes have square areas that can be separated according to the background and brightness, and express information by the brightness of each small square area that is equally divided inside. Usually, these codes are photographed by a camera, the outline of the two-dimensional code is identified and detected from the background, and information is read based on the brightness of each divided area assigned to the inside. Hereinafter, this type of two-dimensional code is referred to as a two-dimensional code 2.

  The two-dimensional code 1 and the two-dimensional code 2 are affixed to an article, etc., and information on the article, for example, information related to manufacturing such as a product number, an individual number, and a manufacturing date, a shipping source, a shipping destination, and a shipping date and time. It is usually used to manage information related to transportation. These codes are usually imaged by a camera from a direction almost opposite to the surface on which the code is pasted, and are photographed so as to appear sufficiently large on the imaging surface of the imaging device. It is assumed that it can be recognized.

[Prior Art 2]
In the mixed reality (hereinafter referred to as MR) technology in which a virtual object is superimposed and displayed in the real space, the following processing is performed to draw a virtual image. A square marker in the real space is used, and the position and orientation of the real camera based on the marker are estimated. Then, the virtual object is drawn by setting the parameters of the virtual camera based on the obtained position and orientation of the real camera.

  A typical example is ARTToolKit shown in Non-Patent Document 1. In ARTToolkit, markers as shown in FIG. 13 are used. This marker detects from the image a quadrangle formed by imaging the square as the outer shape of the image. Then, the position and orientation of the camera are estimated using as an information source how the square is deformed with respect to the original shape which is a square in the three-dimensional space (distorted by the influence of perspective projection). Further, when a plurality of markers are used at the same time, the inside of each marker is painted with a different graphic pattern in order to identify each marker. The identification of the marker is performed using a pattern matching technique with a pattern in which a rectangular internal pattern obtained from an image is prepared in advance. Hereinafter, this is referred to as a two-dimensional code 3.

  Further, as a marker for MR, there is a marker as shown in FIG. This marker is different from the two-dimensional code 3 in that the inside is divided into a 4 × 4 grid and the function of individually identifying the circle is determined by whether or not the circle centered on each grid point is black. However, it is the same as the two-dimensional code 3 in that the position and orientation of the camera is estimated with reference to the outer shape of the square. This is called a two-dimensional code 4.

  In the MR field, other markers having various square outlines have been proposed. For example, there is a marker as shown in FIG. This marker has a plurality of small square areas for specifying the rotation direction in the square plane outside the square. The interior is divided into 4 × 4 areas, each of which is a small square, and individual identification information is expressed by the brightness of each small square. This is called a two-dimensional code 5.

The markers used for MR such as the above-described two-dimensional code 3, two-dimensional code 4, and two-dimensional code 5 have a common feature in that they have a square as an outer shape.
X. Zhang, S.M. Fronz, N.M. Navab: Visual marker detection and decoding in AR systems: A comparative study, Proc. of International Symposium on Mixed and Augmented Reality (ISMAL'02), 2002.

  The two-dimensional code 1 described in the prior art 1 has a concentric circle at the center of the entire region, and a small regular hexagonal region surrounds the concentric circle. The regular hexagonal regions are joined to each other without a gap, and are divided depending on whether they are white or black. The binary value is expressed by white or black, and is photographed and read by the camera. At that time, the location of each regular hexagonal region is specified based on the concentric circle at the center and the line for each angle of 60 degrees. In other words, the index can be detected only when shooting with the two-dimensional code 1 facing almost directly (when shooting with a camera having an optical axis substantially equal to the normal of the surface to which the two-dimensional code is attached). Can not. The same applies to the two-dimensional code 2. The two-dimensional code of the prior art 1 is based on the premise that the image is taken in a state of being almost directly facing the index, and is taken from any direction that is not directly opposed. Is not taken into account.

  Each of the two-dimensional codes 3, 4, and 5 disclosed in the prior art 2 has a low-lightness square as an outer shape against a high-lightness background. In the conventional technique 2, the position and orientation of the camera with respect to the two-dimensional code are estimated and calculated using the deformation method of the square of the outer shape in the image as an information source. The deformation when the outer shape square is captured in the image is caused by the influence of the projective transformation for projecting the three-dimensional space onto the two-dimensional image performed in the photographing process of the camera. That is, the index of the conventional technique 2 is not premised on shooting from a direction almost facing the index, but on the contrary, it is premised on shooting from a visual axis direction different from the normal direction of the index. It is an indicator.

  With respect to the two-dimensional code 3, an arbitrary pattern within the square area is identified by a pattern matching technique in order to identify an individual indicator. The pattern inside the index is stored separately in advance for use in pattern matching. Then, after normalizing the image obtained by cutting out the inside of the index from the photographed image, the image is compared with the stored pattern, and the individual is identified based on whether or not it is similar. This method has a problem that the calculation time becomes enormous as the number of types of patterns to be used and the number of indices to be photographed at a time increase the number of combinations that must be pattern-matched. . In addition, when the number of patterns is increased, the number of similar patterns inevitably increases, which causes a problem of erroneous recognition, and the number of patterns that can be used at one time is about several tens.

  On the other hand, the two-dimensional code 4 and the two-dimensional code 5 are methods in which one square is expressed by the lightness (black and white) of a small square area obtained by dividing the inside of the square at equal intervals. With this method, the problem that occurs in the two-dimensional code 3 does not occur. However, there was room for improvement as shown below.

  In order to put as much information as possible on the two-dimensional code, it is necessary to increase the bit area. However, since the bit area needs to be recognized from the image, there is a limit to reducing the size of each bit area. In other words, whether or not the two-dimensional code can be recognized is determined according to the size when one bit area is captured and projected on the image. In general, in MR applications, it is desirable to use as small a two-dimensional code as possible. However, if the information to be put on the two-dimensional code is increased, the two-dimensional code must be physically large so that it appears sufficiently large on the image. Therefore, the size of the two-dimensional code and the amount of information to be placed are in a trade-off relationship. For this reason, in order to reduce the overall size as much as possible and increase the amount of information, it is desirable to arrange the bit areas in the two-dimensional code minutely.

  The two-dimensional code 4 has a circular inner bit area. The circular areas that are bit areas are arranged in a square lattice pattern. In this method, a gap between the circular regions becomes a problem when one circular region becomes small. For example, when a certain area is painted in black and the circular area is reduced to a value close to one pixel width in the image, it is observed as intermediate brightness mixed with the white area in the surrounding gap on the image. Will end up. This means that errors are increased during bit reading. That is, it is desirable that the inner regions are arranged adjacent to each other without providing a gap.

  In the two-dimensional code 5, the internal bit areas are divided as squares and are adjacent to each other, so that the problem does not occur. This index is characterized in that it can be detected even if it is taken from a direction not necessarily facing the index. The orientation of the small square obtained by dividing the inside of the square at equal intervals is undefined on the image. In other words, it is indefinite what type of quadrangle projection image will be. The two-dimensional code 5 performs a process of converting into a bit value based on the brightness of each small square area captured on the image. Therefore, when reading the lightness, the lightness at that position is read with reference to the center point of each small square. At that time, in order to correctly read out the brightness, the projected small square area in the image must be photographed so as to have a sufficient fixed distance from the center of the readout position, regardless of the direction of photographing. . In other words, when the small area on the original index is reflected in the image, the smaller the projected image of the small area is on the image plane, the smaller the small area on the index. This means that the area of the region can be reduced. This is because the smaller the area of a small region that represents each bit, the larger the number of bits allocated to the entire index area. On the other hand, if each of the small areas is a square, the projected image is a square with a corner, so it cannot always be said that the projections are efficiently and densely arranged.

  On the other hand, in the two-dimensional code 4, although each region is circular, there is a useless gap between the regions, and it cannot be said that the bit regions are arranged at high density.

  From these facts, the two-dimensional code 4 and the two-dimensional code 5 have room for improvement in increasing the density of the bit area.

  The two-dimensional code according to claim 1 of the present application includes a polygonal outer shape that can be identified by the background and brightness or color, and an inner region that is arranged at a predetermined interval on the outer periphery of the outer shape. A two-dimensional code that divides the inner region into a specific size and expresses information by brightness or color of each of the divided regions, wherein the divided regions are adjacent hexagons .

  The two-dimensional code detection method according to claim 5 of the present application includes an outer polygon detection step for detecting a two-dimensional coat reflected in an image from the background, and an internal shape according to the shape of the outer polygon in the image. A bit region specifying step for specifying the position of the bit region, and a bit value acquiring step for acquiring a bit value based on the lightness or color of the specified bit region, wherein the two-dimensional code includes a background and a lightness Alternatively, it has a hexagonal outer shape that can be identified by color, and an inner region that is arranged at a certain interval on the outer periphery of the outer shape, and the inner region is composed of adjacent hexagons. It has a plurality of information areas.

  According to the present invention, it is possible to embed bit information at a high density while enabling detection of a two-dimensional code not only from a direction almost facing the two-dimensional code but also from an arbitrary direction. .

  Hereinafter, the present invention will be described in detail according to preferred embodiments with reference to the accompanying drawings.

[First Embodiment]
FIG. 1 shows a two-dimensional code in this embodiment. 101 in FIG. 1A is a black background as a background of the two-dimensional code, and a two-dimensional code is formed as a white regular hexagonal outline on the black background 102. An area for dividing the interior into regular hexagons at a certain distance from the outer frame is provided, and each area is painted black or white. The relationship between each divided area and the outer frame is as shown in FIG. In this case, the internal small regular hexagonal region and the hexagonal region of the outer frame are inclined by 30 degrees, and the gap between the internal regular hexagon and the hexagon of the outer frame is the same as that of the internal regular hexagon. It is set to half the length between diagonal vertices. FIG. 1C is a diagram showing these relationships in an easy-to-understand manner. FIG. 1C is a diagram in which equilateral triangular meshes obtained by rotating parallel line groups at equal intervals by 120 degrees as auxiliary lines in the background of FIG. 1B are drawn with dotted lines.

  As described above, in the two-dimensional code shown in FIG. 1, the straight line connecting the diagonal vertices of the hexagonal outer shape and one of the opposing sides of the regular hexagon that is the shape of the internal small regular hexagon region are orthogonal to each other. Thus, a small regular hexagonal region is arranged with respect to the outer shape.

  A preferred configuration example of a two-dimensional code detection device that reads this two-dimensional code will be described below. FIG. 3 is a block diagram illustrating a configuration example of the two-dimensional code detection apparatus that detects the two-dimensional code illustrated in FIG. 1.

  Reference numeral 301 in FIG. 3 denotes a camera that images the two-dimensional code shown in FIG. The captured image is written into the memory 305 under the arbitration of the bus controller 304 through the image capturing unit 302. A processing procedure of the present embodiment is stored in the memory 305, and a CPU 303 performs processing according to the processing procedure. A bus controller 304 performs data input / output and arbitration between the CPU 303, the image capturing unit 302, and the memory 305.

  FIG. 4 is a flowchart showing a processing procedure of the two-dimensional code detection apparatus configured by the block diagram shown in FIG. 3, and the processing procedure will be described with reference to FIG.

  First, in step S401, the two-dimensional code shown in FIG. 1 is photographed by the 301 camera, and the photographed image is acquired through the image capturing unit 302. In step S402, a hexagon that is the outer shape of the two-dimensional code shown in the image is detected from the obtained image. Shooting with a camera is not always performed with a posture facing the index (rather, when used in MR applications, shooting is performed from various angles). Further, the horizontal axis of the image is not aligned with the direction of the side of the regular hexagon that is the outer shape of the index.

  The process of detecting the outer shape in step S402 will be described with reference to FIG. FIG. 5 (a) is a view from the position where the index is directly facing, and is drawn with the internal bit area omitted. Here, the internal bit area will be ignored for explanation. When this index is photographed with an actual camera, for example, an image as shown in FIG. 5B is obtained. Even if the index is a regular hexagon as a figure, it will be observed as a convex hexagon that is not a regular hexagon as long as it is not photographed from the opposite position when photographed with a camera. The direction can take any direction. Further, the white area and the black area on the figure are respectively regarded as high and low brightness, and are obtained as halftone brightness in the boundary area. Therefore, the image of FIG. 5B is binarized to form a binary image as shown in FIG. Any method of binarization may be used, but it can be realized by simple threshold processing. When the pixels forming the outer periphery of the white region are tracked and detected from this binary image, an array of pixels forming a closed loop with a single pixel width as shown in FIG. 5D can be obtained. When a polygonal line approximation process is performed on this pixel arrangement, a hexagon shown in FIG. 5E is obtained. At this time, if the original figure is a figure other than a hexagon, the number of break points does not become six as a result of the polygonal line approximation, so it can be determined whether or not the original figure is a hexagon.

  In the above description of S402, the bit area inside the index is ignored. However, since an interval is provided between the internal bit area and the hexagonal shape, when the size of the index in the image is a certain value or more (in the state where the interval is 1 pixel width or more on the image). In the case of shooting), the internal area does not affect the processing of S402.

  In step S403, the center position of each internal bit area is calculated based on the detected hexagonal outer shape. This will be described with reference to FIG. As shown in FIG. 6, each vertex of the regular hexagon that is the original figure shape of the index is represented as (Xn, Yn) (n = 0, 1, 5, 5), and is the outer shape detected on the screen. When each vertex of the square is represented as (xn, yn), the relationship of the two-dimensional projective transformation represented by the following formula is established between them.

  This relational expression can also be described by matrix operation by homogeneous coordinate transformation as follows.

  At this time, the matrix

Is called a homography matrix. Since (Xn, Yn) and (xn, yn) have six corresponding points, six relational expressions shown in Equation 1 or Equation 2 hold. In other words, by solving the simultaneous equations, the homography matrix shown in Equation 3 or the eight parameters H11, H12, H13, H21, H22, H23, H31, and H32 in Equation 1 are obtained from the relationship between the six points. Can do. Since there are eight unknowns, the number is uniquely determined if there is a correspondence of four points. Therefore, when obtaining these eight parameters from the correspondence of six points, it is better to obtain them by the least square method or the like because the simultaneous equations are redundant.

  As described above, once the relational expression 1 or 2 is obtained, an arbitrary point on the space (X, Y) can be mapped to the space (x, y). That is, it is possible to determine at which position the center point of an arbitrary bit area inside the index is projected on the image. For example, it is possible to determine on which coordinates on the image the point 701 shown in FIG. 7 is projected. Step S403 is a step of calculating the position when the center point of the internal bit area of the index appears in the image by the above method.

  Subsequently, the brightness value of the center position of each bit area on the image obtained in step S404 is acquired. The position of the point obtained in step S403 is calculated by projective transformation that occurs when the hexagon is imaged based on the imaged hexagonal outer shape. Don't be. Therefore, the corresponding pixel is not directly represented. Therefore, the lightness at that position is set to the pixel value that is the nearest neighbor, or is obtained by interpolation by a method such as linear interpolation based on the values of the four neighboring pixels. This will be described with reference to FIG. Assume that the center position on the image of the bit area obtained in step S403 is 801. Since the coordinate value 801 is not an integer value, it is not the center of the pixel of the image. The process of obtaining the brightness value of the point 801 is the process of step S404. The process of setting the pixel value of the nearest neighbor point means that the brightness value of 801 is substituted by the pixel value of the pixel 802 that is the closest pixel of the center of 801. The process of interpolating from the pixel values of the four neighboring pixels by a method such as linear interpolation means that the brightness value is interpolated from the pixel values of the pixels 802, 803, 804, and 805.

  In step S405, the obtained brightness value is converted into a bit value. The simplest method is a method of determining whether it is 1 or 0 by comparison with a predetermined threshold value. As the predetermined threshold value, the threshold value used in the binarization of the image performed in step S402 may be used, or any other method may be used. In addition, step S405 may be incorporated not in the interval between step S404 and step S406 but in the step after the processing in all the bit areas is completed in step S406. In that case, in Steps S403, S404, and S406, the brightness value of each internal bit area is acquired over all the internal bit areas, and then the distribution of the obtained brightness values is used as a reference. It is also possible to perform processing such as conversion to a bit value.

  As described above, the process of reading the bit value from the two-dimensional code in which the regular hexagon in this embodiment is the outer shape and the inside is divided by the adjacent small regular hexagonal regions has been described. Here, since the regular hexagon is a rotationally symmetric shape, it is not possible to specify which direction the index shown in the image is upward only by the processing so far. As a solution to this problem, a method in which a plurality of specific bit areas in the internal bit area are used to determine the rotation direction, and white and black are determined in advance as a predetermined color can be considered. Further, like the two-dimensional code 5, it may be realized by providing another region for determining the directionality outside the hexagonal outer shape.

  The above explains how to read bits from a two-dimensional code that has a regular hexagonal outer shape and has hexagonal bit areas adjacent to each other inside. The reason why such a two-dimensional code can solve the problems in the prior art will be described below in detail with reference to FIG.

  FIG. 9A is the same diagram as FIG. 1B, and is a diagram in which regular hexagonal bit regions adjacent to each other are arranged inside the regular hexagonal outline used in the present embodiment. On the other hand, FIG. 9B shows a case where a bit area is provided by the same method as that of the two-dimensional code 5 of the prior art 2, and the inside is composed of squares adjacent to each other. As shown in FIG. 7C, one region in FIG. 7A and one region in FIG. 7B have the same distance between opposing sides when drawn in an overlapping manner. Since these two-dimensional codes are photographed by the camera from an arbitrary direction as described above, when the respective images taken by the camera are overlaid, for example, as shown in FIG. It becomes like this. Here, the camera usually has pixels arranged in a grid pattern, and acquires the brightness and color of the outside world as the pixel value of each pixel. Therefore, as described in the explanation of step S403 with reference to FIG. 8, the brightness and color of this bit area are obtained from the pixel values of the nearest neighbor point and the four neighboring points with reference to the center of the projection area. Become. As shown in FIG. 7 (d), when the bit area is a square, the area where the area increases on the image compared to the case where the bit area is a hexagon is a vertex of a rectangle away from the center. Nearby. This means that there is little effect when obtaining the central brightness value or color. Since the two-dimensional code is premised on being photographed at various angles with respect to the camera, a certain distance from the center point is set as one bit area, that is, the one near the circle as much as possible It is possible to reduce the area of the bit region. Although the area of one bit region in FIG. 7 (a) is about 0.866 times that of one bit region in FIG. 7 (b), the minimum readable size of the bit is determined from various angles. It is almost the same when it is assumed that it will be photographed. In FIG. 7A, there are 19 bit areas, whereas in FIG. 7B there are only 16 bit areas, but the combined area is almost equal. As described above, according to the present invention, it is possible to record a large number of bits without increasing the size of the two-dimensional code.

[Modification]
The two-dimensional code according to the first embodiment shown in FIG. 1 is composed of a regular hexagonal outer shape and a regular hexagonal internal bit region. Further, the outer shape of the two-dimensional code of the first embodiment shown in FIG. 1 may be a rectangle as shown in FIG. The two-dimensional code may have a bit area arranged at a certain interval from the outer shape, and specify the position of the inner bit region on the image with reference to the outer shape reflected in the image. If the internal bit regions are hexagonal regions adjacent to each other, the essence of the present invention is not lost.

  In addition, as an example of the embodiment, a method has been described in which individual bit areas are separated into black and white, and the brightness is converted into a binary value of 1 or 0 by determining a threshold value. As a modification, a method of converting to an n value using a plurality of brightness values may be used, or individual bit areas may be separately colored by a plurality of colors. Even in such a case, the color of each region can still be acquired by the interpolation method from neighboring pixels such as the nearest neighbor method or the bilinear interpolation method. By selecting the obtained color as the most probable color from a plurality (m) of registered color candidates, it is possible to convert it to m states.

[Other embodiments]
Moreover, you may implement | achieve the function equivalent to the parameter | index identification apparatus demonstrated by the above-mentioned embodiment with the system comprised from several apparatus.

  A software program that realizes the functions of the above-described embodiments is supplied directly from a recording medium or to a system or apparatus having a computer that can execute the program using wired / wireless communication. The present invention includes a case where an equivalent function is achieved by a computer executing the supplied program.

  Accordingly, the program code itself supplied and installed in the computer in order to implement the functional processing of the present invention by the computer also realizes the present invention. That is, the computer program itself for realizing the functional processing of the present invention is also included in the present invention.

  In this case, the program may be in any form as long as it has a program function, such as an object code, a program executed by an interpreter, or script data supplied to the OS.

  As a recording medium for supplying the program, for example, a magnetic recording medium such as a flexible disk, a hard disk, a magnetic tape, MO, CD-ROM, CD-R, CD-RW, DVD-ROM, DVD-R, DVD- There are optical / magneto-optical storage media such as RW, and non-volatile semiconductor memory.

  As a program supply method using wired / wireless communication, a computer program forming the present invention on a server on a computer network, or a computer forming the present invention on a client computer such as a compressed file including an automatic installation function A method of storing a data file (program data file) that can be a program and downloading the program data file to a connected client computer can be used. In this case, the program data file can be divided into a plurality of segment files, and the segment files can be arranged on different servers.

  That is, the present invention includes a server device that allows a plurality of users to download a program data file for realizing the functional processing of the present invention on a computer.

  In addition, the program of the present invention is encrypted, stored in a storage medium such as a CD-ROM, distributed to the user, and key information for decrypting the encryption for a user who satisfies a predetermined condition is provided via a homepage via the Internet, for example. It is also possible to realize the program by downloading it from the computer and executing the encrypted program using the key information and installing it on the computer.

  In addition to the functions of the above-described embodiments being realized by the computer executing the read program, the OS running on the computer based on the instruction of the program is a part of the actual processing. Alternatively, the functions of the above-described embodiment can be realized by performing all of them and performing the processing.

  Furthermore, after the program read from the recording medium is written in a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, the function expansion board or The CPU of the function expansion unit performs part or all of the actual processing, and the functions of the above-described embodiments can also be realized by the processing.

It is a block diagram of the two-dimensional code of 1st Embodiment. It is another block diagram of the two-dimensional code of 1st Embodiment. It is a block diagram showing the two-dimensional code detection apparatus of 1st Embodiment. It is a flowchart of the process which the two-dimensional code detection apparatus of 1st Embodiment performs. It is a schematic diagram for demonstrating the method to detect the external shape square of a two-dimensional code. It is a schematic diagram for showing the correspondence between the original external hexagon of the two-dimensional code and the shape when the image is projected, and explaining the projective transformation between them. It is a schematic diagram for demonstrating the method of calculating the center position of each internal bit area | region on the basis of the detected hexagon outer shape. It is a schematic diagram which shows the relationship between the center point of a certain specific bit area on a two-dimensional code surface, and its vicinity pixel. It is a schematic diagram explaining the comparison of the bit area | region per one of the two-dimensional code of 1st Embodiment, and the two-dimensional code of a prior art. It is an example of an index based on a square shape that has been conventionally used, and is a kind of two-dimensional code. It is an example of an index based on a square shape that has been conventionally used, and is a kind of two-dimensional code. It is an example of an index based on a square shape that has been conventionally used, and is a kind of two-dimensional code. It is an example of an index based on a square shape that has been conventionally used, and is a kind of two-dimensional code. It is an example of an index based on a square shape that has been conventionally used, and is a kind of two-dimensional code. It is an example of an index based on a square shape that has been conventionally used, and is a kind of two-dimensional code.

Claims (9)

A polygonal outer shape that can be identified by the background and brightness or color, and an inner region arranged at a predetermined interval on the outer periphery of the outer shape, and dividing the inner region into a specific size , A two-dimensional code expressing information by brightness or color of each of the divided areas,
A two-dimensional code, wherein the divided areas are adjacent hexagons.   The two-dimensional code according to claim 1, wherein the outer shape of the polygon is a hexagon.   The two-dimensional code according to claim 2, wherein the shape of each split region is a regular hexagon.   The divided region is arranged with respect to the outer shape so that a straight line connecting the diagonal vertices of the outer shape of the hexagon and one of the opposing sides of the regular hexagon that is the shape of the divided region are orthogonal to each other. The two-dimensional code according to claim 2, wherein the two-dimensional code is used. An outline polygon detection step of detecting a two-dimensional coat reflected in an image from the background;
According to the shape of the external polygon in the image, a bit area specifying step for specifying the position of the internal bit area;
A bit value acquisition step of acquiring a bit value based on the brightness or color of the identified bit region,
The two-dimensional code has a hexagonal outer shape that can be identified by background and brightness or color, and an inner region that is arranged at a predetermined interval on the outer periphery of the outer shape. A two-dimensional code detection method comprising: a plurality of information areas each formed of adjacent hexagons. The bit region specifying step calculates information corresponding to a two-dimensional projective transformation from the relationship between the rectangular outer shape detected from the image in the outer shape polygon detecting step and the physical outer shape,
6. The two-dimensional code detection method according to claim 5, wherein a position of each of the divided regions in the image is calculated using information corresponding to the two-dimensional projective transformation.   A computer program for causing a computer to execute the two-dimensional code detection method according to claim 5 or 6.   A computer-readable recording medium storing the computer program according to claim 7 in a computer-readable manner. Outline polygon detection means for detecting a two-dimensional coat reflected in an image from the background;
A bit area specifying means for specifying the position of the internal bit area according to the shape of the outer polygon in the image;
Bit value acquisition means for acquiring a bit value based on the brightness or color of the identified bit region;
The two-dimensional code has a hexagonal outer shape that can be identified by a background and brightness or color, and an inner region arranged at a predetermined interval on the outer periphery of the outer shape, and the inner region is A two-dimensional code detection device having a plurality of information areas composed of adjacent hexagons.

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