JP2009025992A - Two-dimensional code - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a two-dimensional code for improving a read rate by correcting expansion/reduction and distortion of an image obtained from a code reader by deformation of the formed two-dimensional code, while it is not easy for the code reader side to correct the distortion of an image obtained from the two-dimensional code reader. <P>SOLUTION: The two-dimensional code formed on a predetermined curved surface, and for representing information by a distribution pattern in a rectangle has a distribution pattern formed along the curved surface so that an image obtained by imaging the two-dimensional code from a predetermined position may have a predetermined rectangular shape. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a two-dimensional code.

An example of a conventional two-dimensional code is disclosed in Patent Document 1, for example. In the two-dimensional code, information to be recorded has a two-dimensional spread, and a much larger amount of information can be recorded as compared with a conventional barcode. The conventional two-dimensional code has three positioning symbols combined with squares having a specific size ratio in order to facilitate the determination of the existing position, and the inside of the two-dimensional code is an n × n square cell. The figure is divided into two.
JP-A-7-254037

  By the way, when the two-dimensional code as described above is formed on a cylindrical object such as a beverage container, there is a problem in that the reading rate by the two-dimensional code reader is remarkably lowered or the reading becomes impossible. is there. As a matter of course, the two-dimensional code is designed on the assumption that it is formed on a flat surface, but this decrease in the reading rate is due to the two-dimensional code being formed on a curved surface. This is caused by the expansion / contraction / distortion of the image in the means.

  The present invention has been made in view of such circumstances, and the distortion of the image obtained by the two-dimensional code reader is not easy to deal with on the code reader side. An object of the present invention is to provide a two-dimensional code capable of correcting expansion / contraction / distortion of an image obtained by a code reader and improving a reading rate.

  The present invention is a two-dimensional code that is formed on a predetermined curved surface and expresses information by a distribution pattern in a rectangle, and an image obtained by imaging the two-dimensional code from a predetermined position has a predetermined rectangular shape. The distribution pattern is formed along the curved surface.

  The present invention is a two-dimensional code expressing information by a distribution pattern in a rectangle, and when the two-dimensional code is attached to a predetermined curved surface, an image obtained by imaging the two-dimensional code from a predetermined position is predetermined. The distribution pattern is formed to be deformed so as to have a rectangular shape.

  The present invention is characterized in that the curved surface is a cylindrical curved surface.

  According to the present invention, when a two-dimensional code representing information by a distribution pattern in a rectangle is formed on a curved surface, the distribution pattern is curved so that an image captured from a predetermined position has an original rectangular shape. Therefore, since the obtained two-dimensional code image can be obtained as an original rectangular shape, it is possible to improve the reading rate of the two-dimensional code. In addition, when the two-dimensional code is not directly formed on the cylindrical surface but is formed on a sheet of paper and the paper is pasted on the cylindrical surface, an image obtained by capturing the two-dimensional code from a predetermined position is an original rectangle. Since the rectangular shape is deformed so as to have a shape, the reading rate of the two-dimensional code can be similarly improved.

  Hereinafter, a two-dimensional code according to an embodiment of the present invention will be described with reference to the drawings. Here, the two-dimensional code according to the present invention is formed on a cylindrical curved surface, and the file format of the two-dimensional code image is a bitmap format. For this reason, it is assumed that one pixel length is the rated width and the minimum unit width in image operations. The two-dimensional code according to the present invention prevents the captured image from being distorted when formed on the surface of a cylindrical beverage container.

  First, a correction method in the horizontal direction (circumferential direction of the cylinder; the horizontal direction of the two-dimensional code) will be described. A perspective projection is considered with the viewpoint position (the position of an imaging means such as a camera) as the origin. When a normal two-dimensional code is attached to a cylindrical object, as shown in FIG. 1, it contracts more than the two-dimensional code formed on the original plane from the center of the two-dimensional code to the ends of the left and right sides. The image becomes In order to modify this, as shown in FIG. 2, the original image is stretched so that the image is on the projection of the image that should be originally present on the cylindrical object.

  Here, the two-dimensional code image modification procedure will be described. First, let us consider an xy plane in which the position (viewpoint) of the imaging means is the origin O, the linear direction from the origin O to the center of the cylindrical object to be formed is the y axis, and the perpendicular direction relative to this is the x axis. Assuming one point B of the ideal two-dimensional code, if the intersection of the straight line extending from the origin O to point B and the side of the cylindrical object is C and the center point of the cylinder is D, then point C The horizontal position can be obtained by calculating the x-coordinate EC of, and obtaining Δ by a trigonometric function and obtaining the length of the arc AC by the arc degree method in ΔDCE. Note that the intersection of the perpendicular from the point C to the y axis and the y axis is a point E, and the angle ODC is θ.

  By this processing, a position (horizontal position) when formed on a cylindrical surface corresponding to an arbitrary position when formed on a plane can be obtained. The ideal horizontal position calculation is performed every time the length is increased by one pixel from the center of the two-dimensional code in the horizontal direction. During the sequential calculation, the difference between the calculated ideal horizontal width and the pixel arranged horizontal length is If there is a length that is an integral multiple of the pixel width, horizontal correction can be performed by duplicating an integral multiple of the number of pixels.

  Next, a detailed procedure for correcting an image of a two-dimensional code will be described with reference to FIG. First, the projection of the line of sight from the viewpoint O to B of unit pixel width (AB) onto the cylinder is defined as B ′, and the length a of the arc AB ′ is obtained (see FIG. 3A).

  Next, it is calculated how many pixel widths there are in the arc AB ′, and an integer number of pixels (area indicated by reference symbol P1 in FIG. 3B) is filled with the pixel pixels of the original two-dimensional bitmap image. . Then, the pixel unit width is increased (AC), the projection of the line of sight from the viewpoint O to the point C is set as C ″, and the length a of the arc AC ″ is obtained (see FIG. 3B).

  Next, the difference between the arc AC ″ and the width in which the pixels are already filled is calculated. The number of pixels in the width is calculated, and an integer number of pixels (area indicated by reference symbol P2 in FIG. 3C) is filled with the pixel of the original two-dimensional bitmap image. Then, the pixel unit width is increased (AD), and the projection of the line of sight from the viewpoint O to AC onto the cylinder is D ′, and the length a of the arc AD ′ is obtained.

  By repeating this procedure, the original pixel can be enlarged sequentially to the ideal point. As a result, it is possible to arrange pixels at a more precise position than simply obtaining the enlargement ratio all at once. The correction in the horizontal direction uses a unique enlargement determination value at a pixel lateral position of the bitmap image.

Here, with reference to FIG. 4, a derivation formula of the above-described correction method will be described. As shown in Fig. 4, from the simultaneous equations of straight lines and circles

Solving this,

From solution formulas and necessary elements

Therefore θ is

によって求めることができる。 The length of the arc AC is

Can be obtained.

  Next, a correction method in the vertical direction (vertical direction of the two-dimensional code) will be described. The reading process of the two-dimensional code reader first reads the part of the black frame: white frame: black square called the position specifier at the three end points of the two-dimensional code, and then reads the black frame horizontally and vertically. Pixels on the straight line in the extension direction are extracted. In the two-dimensional code formed on the plane, when the portion on the straight line is formed on the curved surface, the upper side of the two-dimensional code is convex on the camera lens of a portable terminal or the like used as a two-dimensional code reader as shown in FIG. In addition, the lower side is distorted to be concave. It is necessary to correct the two-dimensional code image for this distortion as shown in FIG.

  Next, the correction procedure in the vertical direction will be described. First, as in the horizontal correction, the xy plane is considered with the position of the imaging means of the camera as the origin O. Assuming one point B of the ideal two-dimensional code, the x component EC of the intersection C with the actual cylindrical shape on the half line OB is calculated. Note that an intersection of the perpendicular from the point C to the y-axis and the y-axis is a point E.

Next, consider the xyz axis space including the height. The height ans (z axis) at the lateral position can be obtained from the similarity between ΔOBI and ΔOCH on the surface OCH and the similarity between ΔOAB and ΔOEC on the surface OAB. Note that, on an ideal two-dimensional code, an x coordinate is B and a point having a height h is a point I. Further, an intersection of the half straight line OI and the actual cylindrical shape is defined as a point H.

  Next, the same operation as the horizontal direction enlargement determination is performed on the vertical direction. However, in the vertical direction enlargement determination, the height (lengthwise enlargement) is calculated by increasing the height and length independently for each pixel.

Here, with reference to FIG. 7, the derivation formula of the correction method described above will be described. As shown in FIG. 7, similarly to the horizontal correction, the value of x, which is one point of the cylindrical shape, is obtained.
From simultaneous equations of lines and circles,

From solution formulas and necessary elements

From the similarity of the triangle

From the above proportional expression, the product of the outer term and the product of the inner term are equal,

  Therefore, an ideal height at a certain point in the bitmap image can be obtained.

  Next, the calculation limit value will be described. In order for the mapping to appear at the original position, it is a precondition that a cylindrical object can be projected. Therefore, when the projection exceeds a possible range, the above-described correction method is not appropriate. However, since it is obvious that a limit point exists at a point where the projection does not physically fit in the cylindrical object, it is necessary to calculate this limit point as a calculation limit value.

With reference to FIG. 8, the procedure for deriving the calculation limit value will be described. A case where the straight line from the side surface of the target cylindrical object and the position O of the imaging means has a contact point is a calculation limit point, and the distance limit from the y axis at the limit point B on the line y = d is calculated. In △ OCD and △ OAB

Therefore, the distance l from the imaging means to the limit value point is

△ From the three-square theorem in OAB, the limit distance limit is

Therefore, when the one-side width size of the two-dimensional code is a, the limit point is not exceeded when the inclination is larger than the inclination of the half line OB.

  Next, a process for recognizing a two-dimensional code formed on a quadric surface will be described. The purpose of this processing is that the two-dimensional code analysis engine of the imaging means such as a camera recognizes the two-dimensional code formed on the curved surface as a plane.

  First, a process for analyzing a two-dimensional code formed on a plane is verified. When the 2D code analysis engine recognizes a 2D code formed on a plane, as shown in FIG. 9, the 2D code analysis engine is constructed on the basis that the distance from each point on the 2D code is different. To do. Based on this, when forming a two-dimensional code on a quadric surface, by providing an image similar to the two-dimensional code formed on the plane for the two-dimensional code recognition process, To improve the recognition rate. That is, as shown in FIG. 10, if a projection image from a data collection point (camera focal point) of the two-dimensional code recognition engine to a flat quadric surface is formed on the quadric surface, the recognition rate of the two-dimensional code is increased. Can be improved.

  However, due to the characteristic that the digital image has a resolution, when an arbitrary point on the two-dimensional code is corrected, the corrected point deviates from the point to be originally projected. In the implementation of this process, based on the assumption that it is within the range of the correction function of the two-dimensional code recognition engine, the correction for the deviation is corrected in a direction that suppresses the overflow of the data amount in the process. It is carried out. Based on these facts, when the two-dimensional code is converted to form a cylinder, it is deformed as shown in FIG.

  As described above, when a two-dimensional code representing information by a distribution pattern in a rectangle is formed on a cylindrical container or the like, the two-dimensional code is provided by a camera provided in a portable terminal or the like from a predetermined position. Since the distribution pattern is formed along the curved surface so that the image obtained by capturing the code has the original rectangular shape, the obtained two-dimensional code image can be obtained as the original rectangular shape. The reading rate of the dimension code can be improved.

  When the 2D code is not directly formed on the cylindrical surface but is formed on a sheet of paper and this sheet is attached to the cylindrical surface, an image obtained by imaging the 2D code from a predetermined position is the original image. If the rectangular shape is deformed so as to have a rectangular shape, the reading rate of the two-dimensional code can be similarly improved.

It is explanatory drawing which shows the state in which the cylindrical surface formed the two-dimensional code. It is explanatory drawing which shows the correction | amendment state of a two-dimensional code. It is explanatory drawing which shows the correction procedure of the two-dimensional code by this invention. It is explanatory drawing which shows the correction | amendment derivation formula of the two-dimensional code by this invention. It is explanatory drawing which shows the distortion state of a two-dimensional code. It is explanatory drawing which shows the correction state of the two-dimensional code by this invention. It is explanatory drawing which shows the correction | amendment derivation formula of the two-dimensional code by this invention. It is explanatory drawing for calculation limit value derivation | leading-out. It is explanatory drawing for demonstrating the recognition process of the two-dimensional code formed in the quadric surface. It is explanatory drawing for demonstrating the recognition process of the two-dimensional code formed in the quadric surface. It is explanatory drawing which shows the example of the two-dimensional code correct | amended based on the correction procedure of this invention.

Explanation of symbols

  O ... Origin (viewpoint; imaging means position)

Claims (3)

A two-dimensional code that is formed on a predetermined curved surface and expresses information by a distribution pattern in a rectangle,
The two-dimensional code, wherein the distribution pattern is formed along the curved surface so that an image obtained by imaging the two-dimensional code from a predetermined position has a predetermined rectangular shape. A two-dimensional code that represents information by a distribution pattern in a rectangle,
When the two-dimensional code is affixed to a predetermined curved surface, the distribution pattern is deformed so that an image obtained by imaging the two-dimensional code from a predetermined position has a predetermined rectangular shape. Two-dimensional code to do.   The two-dimensional code according to claim 1, wherein the curved surface is a cylindrical curved surface.

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