JP2004102348A - Recognition method of two-dimensional code - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a recognition method of two-dimensional codes for positively performing logical and integral light/dark discrimination without performing complicated processing. <P>SOLUTION: In printing the objective two-dimensional code 1, a determination code 2 composed of a combination of a dark code cells 10b and light code cells 10w whose array is known, is printed in a prescribed position in the printing region. The objective two-dimensional code 1 is read together with the determination code 2 by an optical reader, and the light-dark boundary value of the dark code cells and light code cells is obtained based on the optical characteristic value of the dark code cells and the optical characteristic value of the light code cells of the read determination code. The dark code cells and light code cells of the read objective two-dimensional code are recognized based on the obtained light-dark boundary value. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for recognizing an optically readable two-dimensional code for inputting information to a computer or the like, and more particularly, to a method in which data represented by a binary code is converted into cells and arranged as a pattern in a two-dimensional matrix. The present invention relates to a method for recognizing a dimension code.
[0002]
[Prior art]
When printing this kind of two-dimensional code 1 with a printer of a toner system or an inkjet system, as shown in FIG. 5, one code cell 10 is constituted by dots 100 of, for example, 4 columns × 4 rows. Then, by printing all the dots 100 in 4 columns × 4 rows in black, the dark (black) code cell 10b is printed, and all the dots 100 in 4 columns × 4 rows are printed in white (that is, ink is No ejection is performed), thereby printing the light (white) code cell 10w. In this manner, desired data represented by a light-dark (black and white) binary code can be printed on a sheet in a two-dimensional matrix.
[0003]
[Problems to be solved by the invention]
However, in the case of printing the black code cell 10b of the conventional two-dimensional code 1, the ink scatters around one dot 100 or the ink spreads on the paper due to the printing method and the influence of the paper. The black code cell 10b tended to expand. For this reason, in the two-dimensional code, as shown in FIG. 6, the area of the white code cell 10w surrounded by the black code cell 10b is reduced by the expansion of the black code cell 10b, and the area is read by the optical reader. Was sometimes erroneously recognized as gray close to black.
[0004]
On the other hand, even in the case of a black code cell, a difference in shading occurs depending on the condition of the paper and the printer. In some cases, the black code cell may be printed in black close to gray. In an extreme case, the white code cell 10w and the black code cell may be used. There has been a problem that it cannot be distinguished from the code cell 10b.
[0005]
In order to solve such a problem, for example, in Japanese Patent No. 2867904, a threshold value for binarization is adjusted according to the state of a scanning line signal from a two-dimensional image detection device, It has been proposed to adjust the current threshold value according to the state of value.
[0006]
However, in the former method, for example, if the whole image is dark, the threshold value is decreased by an arbitrary amount in the white direction, and if the entire image is dark, the threshold value is increased by an arbitrary amount in the black direction. The so-called trial-and-error method or the comparison method uses only the threshold value obtained as the threshold value to be obtained, and thus it takes a long time to adjust the threshold value.
[0007]
Further, the latter method is an empirical comparison method in which the past binarized state is fed back, and thus has a problem that it takes time to start until the recognition probability is stabilized. There is also a problem that the threshold value fed back becomes inappropriate when the printing status changes.
[0008]
[Means for Solving the Problems]
SUMMARY OF THE INVENTION An object of the present invention is to provide a two-dimensional code recognition method capable of logically and unitarily distinguishing light and dark without performing complicated processing.
[0009]
According to the present invention, there is provided a two-dimensional code recognizing method for recognizing a two-dimensional code arranged as a pattern in a two-dimensional matrix by converting data represented by a light and dark binary code into cells using an optical reading device. A step of printing, at a predetermined position in the printing area, a determination code composed of a combination of a dark code cell and a bright code cell, the arrangement of which is known, when printing a target two-dimensional code; Reading the target two-dimensional code together with the determination code by an optical reading device; extracting a determination code from the read target two-dimensional code and the determination code; and A light / dark boundary value between the dark code cell and the light code cell is calculated based on the optical characteristic value of the dark code cell and the optical characteristic value of the light code cell. And a step of recognizing a dark code cell and a light code cell of the read target two-dimensional code based on the obtained light / dark boundary value. You.
[0010]
In the two-dimensional code recognition method of the present invention, first, when printing a target two-dimensional code, at a predetermined position in the printing area, it is configured by a combination of dark code cells and bright code cells, and the arrangement thereof is A known judgment code is printed.
[0011]
Then, the target two-dimensional code is read together with the determination code by an optical reader, and the optical characteristic value of the dark code cell and the optical characteristic value of the bright code cell of the determination code in the read two-dimensional image data are determined. Then, based on these values, a light / dark boundary value between the dark code cell and the light code cell is obtained. It is desirable that the light / dark boundary value be logically defined so as to be uniquely determined by the optical characteristic value of the dark code cell and the optical characteristic value of the bright code cell.
[0012]
When the light / dark boundary value is obtained from the read data of the judgment code, the dark code cell and the light code cell of the target two-dimensional code in the previously read data are recognized based on this.
[0013]
In the present invention, a determination code in which the arrangement of dark code cells and light code cells is known is printed in the same two-dimensional code. The two-dimensional code to be executed is also equal. Then, using the two-dimensional image data read at the same time, the actual optical characteristic value of the dark code cell and the optical characteristic value of the bright code cell are detected by using a determination code having a known arrangement, and for example, the light / dark value such as an intermediate value is detected. The boundary value is uniquely determined. Since the thus determined light / dark boundary value is a value closest to the actual value for the currently read two-dimensional image data, the light / dark recognition of the target two-dimensional code is performed using this.
[0014]
As described above, in the present invention, since the judgment code is printed under the same printing conditions as the two-dimensional code to be recognized, a unified recognition method is used. As a result, the dark code cell Even if the optical characteristic value of the bright code cell fluctuates, it is possible to easily set a light / dark boundary value (threshold) suitable for the fluctuation, and the recognition accuracy is remarkably improved.
[0015]
Further, in the present invention, since the light / dark boundary value is logically determined from the detected optical characteristic value of the dark code cell and the optical characteristic value of the bright code cell, an appropriate threshold value can be obtained immediately without trial and error. Can be.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0017]
FIG. 1 is a diagram showing an example of a two-dimensional code and a determination code according to the present invention. The two-dimensional code 1 is data in which code cells 10 formed of dots of a two-dimensional matrix of four columns × 4 rows are arranged as a pattern in a two-dimensional matrix of 14 columns × 8 rows. The position of 3 columns × 3 rows at the upper left of the 14 columns × 8 rows is assigned as a print area of a determination code 2 described later. However, depending on the type of the determination code 2, it is not limited to the allocation area of 3 columns × 3 rows, and any m columns × n rows can be allocated.
[0018]
In the example shown in the figure, in the first row, from the left, from the left, the dark code cell 10b, the dark code cell 10b, the dark code cell 10b, the dark code cell 10b, the bright code cell 10w, the dark code cell 10b, and the bright code cell 10w. , 14 binary data of bright code cell 10w, dark code cell 10b, bright code cell 10w, dark code cell 10b, dark code cell 10b, bright code cell 10w, and dark code cell 10b are arrayed (of these, 1 to 10). The three dark code cells 10b in the three columns are those of the judgment code 2), and in the second row, from the left, the dark code cell 10b, the bright code cell 10w, the dark code cell 10b, the bright code cell 10w, and the bright code cell. 10w, bright code cell 10w, bright code cell 10w, dark code cell 10b, bright code cell 10w, bright code cell 10w, bright code cell 10w, dark 14 binary data, ie, a dark cell 10b, a dark code cell 10b, and a dark code cell 10b (two dark code cells 10b in one to three rows and one bright code cell 10w are included in the judgment code 2). Stuff). The two-dimensional code 1 of such a matrix method can have a large amount of information in a small area unlike the bar code method.
[0019]
FIG. 2 shows an example of the code cell 10 of the present embodiment. The code cell 10 shown in FIG. 1 is composed of a two-dimensional matrix dot pattern of 4 columns × 4 rows, and one dot corresponds to, for example, one pixel of the printer. The code cell shown in FIG. 3A is a dark code cell 10b, and the code cell shown in FIG. 3B is a bright code cell 10w.
[0020]
In the dark code cell 10b shown in FIG. 3A, all 16 dots of 4 columns × 4 rows are constituted by dark dots 100b. Specifically, printing is performed by turning on the ink at the dark dot 100b during printing.
[0021]
On the other hand, in the bright code cell 10w shown in FIG. 3B, all the dots 100 are composed of the bright dots 100w. Specifically, the bright code cell 10w is printed by turning off the ink ejection during printing. You.
[0022]
FIGS. 3A to 3C are diagrams showing examples of the determination code 2 according to the present invention. However, the determination code of the present invention is not limited to only these three forms. Combinations and the like can also be used.
[0023]
The determination code 2 shown in FIG. 3A is composed of nine code cells 10 in 3 columns × 3 rows, and only the cell located at the center is a bright code cell 10w, and the bright code cell 10w surrounds the bright code cell 10w. One of the code cells is a dark code cell 10b. In this determination code 2, there is a possibility that the bright code cell 10w located at the center is recognized as gray closest to black due to the influence of the scattering or bleeding of the ink of the dark code cells 10b arranged around. . Therefore, by using the determination code 2, the optical characteristic value of the bright code cell 10w which is the closest to black can be detected, and the optical characteristic value and the optical characteristic value detected from the surrounding dark code cell 10b can be detected. For example, by setting the intermediate value as a light / dark boundary value (threshold), the light code cell 10w is erroneously recognized as the dark code cell 10b, and conversely, the dark code cell 10b is erroneously recognized as the light code cell 10w. Can be prevented.
[0024]
On the other hand, the judgment code 2 shown in FIG. 3B is composed of nine code cells 10 in three columns and three rows, and the code cell located at the center and the code cells located at the four corners are bright code cells. 10w, and the other code cells are dark code cells 10b.
[0025]
The determination code 2 shown in FIG. 3C is composed of 18 code cells 10 in 6 columns × 3 rows, the code cells located on the outer periphery are dark code cells 10b, and the four code cells located in the center are Are three bright code cells 10w.
[0026]
In particular, the judgment code 2 illustrated in FIGS. 7A and 7C includes the dark code 10b in all of the outermost code cells. Not affected by code. Since the bright code cell 10w, which is entirely surrounded by the dark code cells 10b, generally has the lowest reflected light intensity, the judgment code 2 shown in FIGS. It is more preferable to use. In particular, when the bright code cell 10w surrounded by the dark code cell 10b is used as the determination code 2, it is preferable that a plurality of the code cells exist as shown in FIG. This is preferable because reading accuracy can be improved. In this case, the average value or the smaller value is used.
[0027]
Such a determination code 2 is printed at a predetermined position in the two-dimensional code 1 shown in FIG. 1 at the same time as a target two-dimensional code.
[0028]
Next, the processing procedure of the present embodiment will be described with reference to FIG.
[0029]
First, before entering the routine of FIG. 2, that is, when printing a two-dimensional code obtained by converting the target binarized data into cells, the above-described determination code 2 is also printed at a predetermined position of the two-dimensional code. In the example shown in FIG. 1, the determination code 2 is printed at the position of 3 columns × 3 rows at the upper left of the two-dimensional code 1. As described above, by simultaneously printing the determination code 2 in the two-dimensional code 1 to be read, the printing conditions such as scattering, bleeding, and blurring of the ink in the printing conditions at that time of the printer are not affected. However, the change is also reflected in the determination code 2.
[0030]
Next, in step 1 shown in the figure, the two-dimensional code 1 is read using an optical reading device. In this case, if the judgment code 2 is embedded in the two-dimensional code 1 as in this example, the judgment code 2 is automatically read simultaneously with the two-dimensional code 1. As described above, by simultaneously reading the two-dimensional code 1 and the determination code 2 by the optical reading device, it is possible to minimize the fluctuation of the reading conditions of the optical reading device.
[0031]
The read two-dimensional image data of the two-dimensional code 1 and the determination code 2 are temporarily stored in a memory or the like in step 2, but in the next step 3, only the determination code 2 is extracted from the two-dimensional image data. Extract. This process is performed by extracting information at the position from the two-dimensional image data because the print position of the determination code 2 is known. Then, the optical characteristic values of the dark code cell 10b and the bright code cell 10w are detected from the extracted two-dimensional image data of the determination code 2. The optical characteristic value can be obtained as digital data corresponding to the reflected light of the optical reading device. This is represented by a value of 0 to 255, for example.
[0032]
In the next step 4, in the determination code 2 of the example shown in FIG. 3A, the reflected light intensity of the bright code cell 10w positioned at the center is directly used as the optical characteristic value of the bright code cell 10w, The value closest to white (or the average value) among the reflected light intensities of the eight arranged dark code cells 10b is set as the optical characteristic value of the dark code cell 10b. Then, the median value (average value) of the optical characteristic value of the bright code cell 10w and the optical characteristic value of the dark code cell 10b is calculated, and the calculated value is set as a light-dark boundary value as a threshold value. Assuming that the reflected light intensity of the bright code cell 10w obtained from the two-dimensional image data of the determination code 2 is 180 and the reflected light intensity of the dark code cell 10b is 50, the light / dark boundary value is 115. Note that the method of obtaining the light-dark boundary value is not limited to the median value (average value), but may be any logical one. For example, various directions are conceivable, such as subtracting or adding a predetermined value to or from the optical characteristic value of the light code cell 10w or the dark code cell 10b to obtain a light / dark boundary value. In this manner, by using a logical expression that can be uniquely and immediately obtained from the optical characteristic values of the bright code cell 10w and the dark code cell 10b, it is possible to quickly shift to the subsequent steps.
[0033]
It should be noted that the two-dimensional image data that is the determination code 2 is recognized as, for example, all code cells are recognized as dark code cells, or it is recognized that there is a bright code cell in a position other than the position where it should be a bright code cell. If it does, error processing is performed as data without the judgment code 2.
[0034]
When the light / dark boundary value is obtained in step 4, two-dimensional image data other than the judgment code 2 temporarily stored in the memory is read out, and the light / dark boundary value is used as a threshold to determine light / dark (step 5). ).
[0035]
As described above, in this example, the optical characteristic values of the bright code cell 10w and the dark code cell 10b are detected using the determination code 2 printed under the same printing conditions, and the light / dark boundary value is set based on the detected values. Therefore, the threshold value is most suitable for the actual printing conditions. As a result, erroneous recognition of the bright code cell 10w and the dark code cell 10b is prevented even if the printing conditions fluctuate, and the recognition accuracy is significantly improved.
[0036]
When the light / dark determination of the two-dimensional image data of the two-dimensional code 1 is completed in step 5, the process proceeds to the next two-dimensional code determination (step 6). Here, the light-dark boundary value obtained in step 4 is used only for the two-dimensional code 1 read in step 1, and another two-dimensional code 1 is read in another opportunity in step 6. At that time, the optical characteristic value of the judgment code 2 at that time is used. That is, in this example, since the light-dark boundary value is determined in a unified manner, the recognition accuracy of the rising edge does not decrease unlike the trial-and-error method or the feedback method.
[0037]
The embodiments described above are described for facilitating the understanding of the present invention, and are not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.
[0038]
【The invention's effect】
As described above, according to the present invention, the erroneous recognition of a dark code cell as a bright code cell and the erroneous recognition of a bright code cell as a dark code cell are eliminated, and the reading accuracy is improved without performing complicated processing. Can be increased.
[Brief description of the drawings]
FIG. 1 is a diagram showing an example of a two-dimensional code and a determination code according to the present invention.
FIG. 2 is a diagram showing an example of one code cell (4 columns × 4 rows) according to a two-dimensional code according to the present invention.
FIG. 3 is a diagram showing an example of a determination code according to the present invention.
FIG. 4 is a flowchart showing a processing procedure of the present invention.
FIG. 5 is a diagram showing a conventional two-dimensional code.
FIG. 6 is a diagram showing a bright code cell for explaining a problem of a conventional two-dimensional code.
[Explanation of symbols]
1 2D code 10 code cell 10b dark code cell 10w bright code cell 100 dot 100b dark dot 100w bright dot 2 determination code

Claims (4)

A two-dimensional code recognizing method for recognizing a two-dimensional code arranged as a pattern in a two-dimensional matrix by converting data represented by a light and dark binary code into a cell using an optical reading device,
When printing a two-dimensional code of interest, at a predetermined position in the print area, configured by a combination of dark code cells and bright code cells, the step of printing a determination code whose arrangement is known,
Reading the target two-dimensional code with the determination code by an optical reading device,
Extracting a determination code from the read target two-dimensional code and the determination code,
Based on the optical characteristic value of the dark code cell and the optical characteristic value of the bright code cell of the extracted determination code, a step of obtaining a light-dark boundary value between the dark code cell and the bright code cell,
Recognizing a dark code cell and a bright code cell of the read target two-dimensional code on the basis of the determined light / dark boundary value. 2. The two-dimensional code recognition method according to claim 1, wherein the determination code is a two-dimensional code having three columns and three rows, in which a bright code cell is arranged in the center, and the bright code cell is surrounded by dark code cells. . 2. The two-dimensional code recognition method according to claim 1, wherein the determination code is a three-column × three-row two-dimensional code in which bright code cells are arranged at the center and four corners, and dark code cells are arranged at other positions. 2. The two-dimensional code recognizing method according to claim 1, wherein the determination code has dark code cells arranged on all outer circumferences and bright code cells arranged at a part of the center.

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