JPH0950480A - Two-dimensional code reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correct reading without rearranging the recording carrier of original, etc., in which the symbol of a two-dimensional bar code is recorded when the symbol is placed obliquely to the scanning direction of a line sensor. SOLUTION: When the two-dimensional bar code of a PDF-417 is decoded by utilizing the scanner of a digital copying machine, the buffer generating the T sequence of the symbol of the two-dimensional bar code for every scanning line is prepared for left and right T sequences. After this symbol is stored in a line buffer 3 for read data, a left T sequence is selected at a point of time when the starting pattern of the symbol is detected by a starting pattern detection means 6. At the point of time when the starting pattern is not detected by a left and right switching selection means 7, the sequence is switched to a right T sequence. The left and right T sequences are stored in a total T sequence memory 8 in a format that the sequences coexist, stitchings are performed for these sequences and decoding processings are performed for the sequences.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly uses a scanner of a digital image input / output device such as a digital copying machine, a facsimile device, a filing system, etc.
The present invention relates to a two-dimensional code reader for decoding a two-dimensional bar code of F-417, and more particularly to a diagonal reading correction of a two-dimensional code.

[0002]

2. Description of the Related Art Conventionally, as a prior art example proposed for the purpose of expressing data as a machine-readable graphic image as encoded information and recognizing it, Japanese Patent Laid-Open No. 5-29 is known.
No. 0204 and Japanese Patent Laid-Open No. 6-12515,
An apparatus is disclosed which optically reads a two-dimensional bar code recorded on a record carrier by a line sensor such as a handy scanner and executes the decoding.

By the way, a two-dimensional bar code is a symbol
A representative example is PDF-417 developed by Technologies. Hereinafter, description will be made assuming that PDF-417 is used as the two-dimensional barcode.
For details of PDF-417, refer to U on January 5, 1990.
It is described in SP07 / 461881, and its algorithm has already been published.

FIG. 12 illustrates different patterns of various sizes of PDF-417 symbols. 12 (B) (C)
As shown in, PDF-417 symbol is 30 × 60mil
There are two sizes, s and 24 × 24 mils, both of which have the same configuration. That is, as shown in FIG. 12, the PDF-417 symbol is erect by stacking bar coded data rows vertically, and each row in the symbol has a start pattern S and a left row indicator pattern in order from the left end.
RL, codeword data area D, right row indicator pattern R
An R and a stop pattern T are constructed in series.

The start pattern S and stop pattern T identify the start and end points of each row of symbols. The left and right line indicator patterns RL and RR include the line number and the number of symbols, the number of data columns, or the security level of the symbol. Further, codewords are the basic units for encoding numbers, letters, other symbols or their associated values, and the codewords within each row collectively form a data string. C represents the codeword in a digitized form. The black part in the symbol is called a bar and the white part is called a space.

FIG. 13 shows a basic pattern of the symbol structure of the PDF-417 two-dimensional bar code. As is clear from the pattern of this figure, the cell a is a minimum unit block that constitutes a data string. Further, a portion in which each cell is filled with black is called a bar, and a portion that remains white is called a space, and data is coded by the interval between these bars and spaces.

The set of alternating bars and spaces within this codeword is defined as an X-sequence of codewords, and this X-sequence is generated when data is encoded. On the other hand, when decoding, a sequence for obtaining the bar data and space interval data of coded data is defined as a T sequence.

In the conventional reading device constructed for the PDF-417 two-dimensional bar code having the above-mentioned configuration, the P sensor is used by a line sensor such as a handy scanner.
When reading the DF-417 symbol, it is premised that the start pattern S and the stop pattern T are detected at the same time, and when the reading is started, the left and right row marking patterns adjacent to the start and stop patterns S and T Only by solving RL and RR, the decoding of the code word data area D can be executed.

[0009]

As described above, in the case of the conventional apparatus, the PDF-417 symbol is usually read by the handy scanner and its decoding is executed, and the conditions at that time are both start and stop. Since it is premised that the patterns S and T can be found, there is a problem that the symbol cannot be decoded when the symbol is read diagonally.

That is, when reading the two-dimensional code with the line sensor, if the symbol is placed in parallel with the scanning direction of the line sensor, the start pattern S and the stop pattern T are simultaneously detected from the first scanning line. Therefore, there is no problem that the decoding is disabled, but it is usually possible to set a symbol at a slight inclination angle with respect to the scanning direction of the line sensor on a daily basis.

However, in the conventional apparatus, when the symbols are set in such a tilted shape, a range in which only the start pattern S or only the stop pattern T can be read inevitably occurs in any of the scanning lines. . In this scan line range, both the start and stop patterns S and T are not detected at the same time, resulting in a decoding error, and it is necessary to correctly reposition the record carrier on which the symbols are recorded, for example, the document. Becomes

As described above, in the case of the conventional apparatus having the working condition that the symbols must be arranged parallel to the scanning direction of the line sensor, for example, in the case of a digital copying machine, the symbols must be arranged parallel to the edge of the contact glass surface. There was a disadvantage and trouble that it took a lot of trouble to the user's symbolic work.

The present invention has been made in order to solve the above problems, and even when a symbol of a two-dimensional bar code is placed obliquely to the scanning direction of the line sensor, It is an object of the present invention to provide a two-dimensional code reading device having a function of correcting reading without repositioning a record carrier such as a document on which the symbol is recorded.

[0014]

In order to achieve the above object, according to the first aspect of the present invention, a line sensor for optically reading a two-dimensional bar code on a record carrier, and a line sensor for reading the line sensor are read. A line buffer for read data that stores a symbol of a two-dimensional bar code, a left T sequence generation buffer that generates a T sequence that reads the symbol from the left side for each scan line, and a T sequence that reads the symbol from the right side A right T-sequence generation buffer that generates each scan line, a start pattern detection unit that detects a start pattern provided at the left end of the symbol, and the left when the start pattern is detected by the start pattern detection unit. Select the T sequence, the symbol to be read is still present and the starting pattern is detected Left and right switching selecting means for switching to the right T sequence at the time when no longer, the left and right T sequence is assumed that and a decoding means for decoding the data of the scan lines to be mixed.

According to the first configuration, a left T sequence for left-reading a symbol and a right T-sequence for right reading are prepared in advance for each scanning line of the line sensor.
Since the timing to switch and mix the sequences is performed depending on the presence or absence of the start pattern, when the entire two-dimensional barcode symbol is obliquely arranged with respect to the scanning direction of the line sensor, after reading the symbol,
The left T sequence is generated during the period from the detection of the start pattern until the start pattern is not detected, and after the start pattern is not detected, the process is switched to the right T sequence generation.

Then, the code word conversion of the data of the scanning line in which the left and right T sequences are mixed is performed, and the left and right T sequences are rearranged to perform the stitching process for performing the diagonal correction to create the document code.

As a second configuration of the present invention, start pattern matching means for matching the presence or absence of a start pattern provided at the left end of the symbol for each scanning line stored in the same line buffer as described above, For each scanning line stored in the line buffer, a stop pattern collating means for collating the presence or absence of a stop pattern provided at the right end of the symbol, and one of the start pattern and the stop pattern detected first by collation A T sequence of symbols to be read from the pattern side is generated for each scanning line, and when the other pattern is detected during the generation of the T sequence, a T sequence of symbols to be read from the other pattern side is generated for each scanning line. The T-sequence generation buffer to generate and the data of the scanning line in which the left and right T-sequences are mixed are decoded. It is assumed that and a decoding means for de processing.

Further, in the above-mentioned second configuration, the T sequence generation buffer is arranged such that when the start pattern and the stop pattern are detected at the same time, that is, when the symbols are arranged in parallel, from the left end of the symbol, that is, the start pattern side. Only the left T sequence to read may be generated.

According to the second configuration, since the start or stop pattern is collated for each line in advance, when the entire symbol of the two-dimensional bar code is obliquely arranged with respect to the scanning direction of the line sensor, the symbol When the starting pattern is first detected after reading, the symbol is read from the left to generate the left T sequence. When the generation of the left T sequence for each scan line progresses and a stop pattern is detected, the symbol is read from the right at that time point and the right T sequence is generated.

In this case, when the stop pattern comes first, the order is reversed. Then, similar to the first configuration, the codeword conversion of the data of the scanning line in which the left and right T sequences are mixed is performed, and the left and right T sequences are rearranged to perform the stitching process for performing the diagonal correction to obtain the document code. create.

[0021]

1 to 6 show an embodiment of a two-dimensional code reading apparatus embodying the present invention. As shown in FIG. 1, this reading device includes a decoding device 1 which is configured in a central control unit of a digital copying machine, and reads a PDF-417 symbol using a scanner 2 attached to the copying machine. Is configured. Scanner 2 is CC
A two-dimensional bar code, which is composed of a D line sensor and is recorded on an original as a record carrier, is optically read,
The read data is output to the decoding apparatus 1.

The decoding device 1 performs the skew correction of the symbol due to the inclination of the document with respect to the scanning direction of the scanner 2 when the T sequence is generated after the symbol of the two-dimensional bar code shown in FIG. 12 is read. Then, Fig. 2
As shown in, the line buffer 3 for read data, left T
Sequence generation buffer 4, right T sequence generation buffer 5, start pattern detection means 6, left / right switching selection means 7,
All T sequence memory 8 and rearrangement (stitching)
The decoding is performed in the order of symbol input → T sequence generation → code word conversion → stitching → document code output, and the diagonal correction is performed by T.
It is performed when the sequence is generated.

The line buffer 3 stores the symbols of the two-dimensional bar code read by the scanner 2. Left T
The sequence generation buffer 4 reads the symbol from the left side T
A left T sequence for generating a sequence (hereinafter referred to as a left T sequence) is generated for each scanning line. Similarly, the right T sequence generation buffer 5 generates a T sequence (hereinafter referred to as a right T sequence) for reading symbols from the right side for each scanning line.

The start pattern detecting means 6 detects the start pattern S provided at the left end of the symbol. The left / right switching selection means 7 selects the left T sequence at the time when the start pattern S is detected by the start pattern detection means 6, and the right T sequence at the time when the symbol to be read is still present and the start pattern S is no longer detected. Switch to. The entire T sequence memory 8 stores the generated left and right T sequences. The rearrangement means 9 rearranges and combines the data of the scanning lines in which the left and right T sequences stored in the entire T sequence memory 8 are mixed, and creates correct read data.

Next, referring to the flowchart of FIG. 3, the reading operation of the PDF-417 symbol by the reading device will be described. In step # 5, the reading operation of the PDF-417 symbol is started. Here, L indicates the scanning line number of the scanner 2.

When the reading of the symbol is started, the read data line buffer 3 temporarily stores the data of the read symbol, and then in step # 10, the left T sequence and the right T sequence of the symbol L line are generated. , These are stored in the left and right T sequence generation buffers 4 and 5. In step # 15, the presence or absence of the start pattern S is checked from the T sequences on the left and right of the L line generated by the start pattern detecting means 6.

At this time, when the start pattern S is detected, the left T sequence is selected in step # 20, and thereafter,
In step # 30, an L line T sequence is generated and stored in the entire T sequence memory 8. Then, in step # 35, did you reach the last line of the symbol?
If not, the process from step # 5 to step # 30 is repeated for the next scan line, and thereafter, in step # 40, the generation of the T sequence for the entire symbol is similarly completed. Repeat the above process until each scan line.

The above is the PDF-417 recorded on the original.
When the symbols are arranged parallel to the scanning line of the scanner 2 and the generation of the T sequence is completed as described above, the data is converted into a codeword and rearranged as described later. , Finally document coded.

On the other hand, the PDF-4 recorded on the document
The 17 symbols may be obliquely arranged with a slight inclination angle with respect to the scanning line of the scanner 2. 4 and 5 show how the T-sequences are arranged (Fig. 4) and how to read when the symbols are set diagonally to the scanning line.
An example (FIG. 5) is shown.

That is, when the symbols B are obliquely arranged with respect to the scanning line as shown in FIG.
There is no T sequence data from the time of the first line (L = 1) when the scanning of the symbol B is started by the scanner 2 to immediately before the start pattern S appears (L = n−1), as shown in Is recognized as Note that scanning one cell corresponds to five scanning lines.

When the nth line in which the start pattern S appears appears, this is recognized in step # 15, and the left T sequence is selected in step # 20. The T sequence data at this time is, for example, as shown in FIG.
422 ... This T sequence data is, as is clear from the comparison with the PDF-417 symbol of FIG.
92222247 is the leftmost start pattern S, 422 ... Is the left row indicator pattern RL, and on the nth line, only the start pattern S and a part of the left row indicator pattern RL are present in the data. I understand.

Next, in the (n + 1) th line, 9222247 422
.. 223. Since a part of the code word data area D appears here for the first time, left T sequence data is generated in step # 30. While the start pattern S can be detected even after the (n + 2) th line, the left T sequence data is generated after the start pattern is detected.

At the m-th line, the starting pattern S which is the reference of the left T sequence disappears. Therefore, in step # 15, it is recognized that there is no start pattern S, and in step # 25, the so-called right T sequence, which is read from the stop pattern T already existing in the data by the operation of the left / right switching selection means 7, is selected, In # 30, the T sequence of the m-th line is generated in the form of reverse reading. Therefore,
4, 824422 is the T sequence data of the stop pattern T, 324 ... Is the T sequence data of the right row indicator pattern RR, and 587 ... Is the T sequence data of the right end of the data area D. From this point, the T sequence data is in a form in which the left T sequence and the right T sequence are mixed.

When the reading up to the last line is completed, the T sequences of the respective rows output from the entire T sequence memory 17 are rearranged, that is, stitching is performed. Figure 6
Shows an example of the stitching process. In this figure, S
Is a start pattern, R is a left / right row marking pattern RL, RR, T
Is a stop pattern.

The rearranging means 9 computes clusters and codewords from each T sequence and performs diagonal correction from the attribute data. A cluster is a set of codewords divided into three mutually exclusive subsets.
For the F-417 symbol, each row encodes data using only one of the three clusters, with each cluster repeating in sequence every third row. Since any two adjacent rows use different clusters, the decoder can distinguish clusters from different rows within the same scan line.

In this diagonal correction, when a codeword matrix is created, the table is filled with row information such as [1] [2] as shown in FIG. 6 (A). When [S] indicating the start pattern S first exists, the data is filled from the left as it is, and when [T] indicating the stop pattern T exists, the data is sequentially filled from the right,
Based on the line information read diagonally by this,
As shown in FIG. 6 (B), the correction can be performed without omission.

7 to 11 show another embodiment of the two-dimensional code reading apparatus embodying the present invention. Also in this embodiment, the decrypting device is constructed in the central control unit of the digital copying machine, and the scanner thereof is used to operate the PDF-41.
It is configured to perform 7-symbol decoding, and the above-mentioned implementation is performed in that a scanner including a CCD line sensor optically reads a two-dimensional bar code recorded on an original and outputs the read data to a decoding apparatus. It is similar to the form.

The decoding apparatus performs the skew correction of the symbol due to the inclination of the document with respect to the scanning direction of the scanner 2 when the T sequence is generated after the symbol of the two-dimensional bar code shown in FIG. 12 is read. As shown in FIG. 7, a line buffer 13 for read data, a start pattern matching means 14, a stop pattern matching means 15, T
Sequence generation buffer 16, all-T sequence memory 1
7 and rearranging (stitching) means 18.

The line buffer 13 stores the PDF-417 symbols read by the scanner. The start pattern matching means 14 matches the presence or absence of the start pattern S for each scanning line stored in the line buffer 13. The stop pattern collating means 15 collates the presence or absence of the stop pattern T for each scanning line stored in the line buffer 13.

The T-sequence generation buffer 16 generates, for each scanning line, a T-sequence of symbols to be read from one of the start pattern S and the stop pattern T, which is detected first by collation, and the T-sequence of the T-sequence is generated. When the other pattern is detected during generation, a T sequence of symbols read from the other pattern side is generated for each scanning line. In addition, the start pattern S and the stop pattern T
If and are detected simultaneously, the left T read from the left edge of the symbol
Generate only sequences.

The all-T sequence memory 17 stores the generated T
Store the sequence. The rearrangement unit 18 rearranges and combines the data of the scanning lines in which the left and right T sequences stored in the entire T sequence memory 17 are mixed, and correct read data is created.

Next, referring to the flowchart of FIG. 8, the reading operation of the PDF-417 symbol by the reading device will be described. In step # 105, the reading operation of the PDF-417 symbol is started. When the reading of this symbol is started, the read data line buffer 13 temporarily stores the data of the read symbol. Next, in step # 110, the T sequence at the left end of the symbol L line is calculated, and in step # 115 it is checked whether or not the result is start pattern data which is the specific data.

FIGS. 9 and 10 show an example of how the T-sequences are arranged (FIG. 9) and how they are read (FIG. 10) when the symbols are set obliquely with respect to the scanning line.
When the symbols B are obliquely arranged with respect to the scanning line as shown in FIG. 10, the start pattern S is started from the time of the first line (L = 1) when the scanning of the symbols B is started as shown in FIG. There is no T sequence data until just before (L = n-1) appears, and it is recognized as a blank part.

When the nth line in which the start pattern S appears appears, this is recognized in step # 115, and the left T sequence is generated in step # 120. in this case,
When the start pattern S does not appear, the stop pattern T always appears at first because of the diagonal arrangement of the symbols. In that case, the process proceeds to step # 135 to generate the right T sequence. That is, the data is read backward.

After that, while the start pattern S or the stop pattern T can be detected from the (n + 1) th line onward, the left or right T sequence data is generated after detecting those patterns and all of them are generated. It is stored in the T sequence memory 17.

When the left T sequence is generated at the m-th line in step # 120, the start pattern S and the stop pattern T serving as the reference of the right T sequence appear.
Therefore, when it is determined that the stop pattern T appears in step # 125, the generation of the T sequence is read back from the line to the right T sequence, that is, from the stop pattern T in step # 130. From this point, the T sequence data is in a form in which the left T sequence and the right T sequence are mixed.

In the m-th line, step # 13
When the right T sequence is generated in step 5, since the start pattern S that serves as the reference of the left T sequence appears together with the stop pattern T, it is determined in step # 140 that the start pattern S has appeared, and in step # 145, the left T sequence is generated. Will generate a sequence.

Then, in step # 150, it is determined whether or not the final line of the symbol is reached. If not, the process from step # 105 to step # 150 is repeated for the next scanning line, and thereafter. Similarly, the above process is repeated for each scan line until the generation of the T sequence for the entire symbol is completed in step # 155.

In this way, when the reading up to the last line is completed, the T sequences of the respective rows output from the entire T sequence memory 17 are rearranged, that is, stitching is performed. FIG. 11 shows an example of the stitching process in this case. The rearrangement unit 18 calculates a cluster or a codeword from each T sequence and performs diagonal correction from the attribute data.

In this diagonal correction, when a codeword matrix is created, the table is filled with row information such as [1] [2]. When [S] indicating the start pattern S is present first, the data is filled in from the left as it is,
When there is [T] indicating the stop pattern T, the data is sequentially filled from the right side, whereby the line information read obliquely can be used as a reference and correction can be performed without omission. The result is the same as that shown in FIG. 6 (B).

In the above-described embodiment of the present invention, the configuration of the reading device for reading by using the scanner of the digital copying machine has been described. However, in the present invention, the decoding device is installed independently of the copying machine. Of course, it is also possible to use a device such as a facsimile machine having a scanner other than the copying machine.

[0052]

As described above, according to claim 1 of the present invention, when a two-dimensional bar code of PDF-417 is decoded by using a scanner such as a digital copying machine, the entire symbol is scanned. When read diagonally with respect to a line, prepare a left T sequence for left-reading a symbol and a right T-sequence for right reading for each line in advance, and after reading a symbol, set a start pattern. During the period from the detection to the time when the start pattern is no longer detected, the left T sequence is generated, and the timing to switch and mix the T sequences is performed depending on the presence or absence of the start pattern. Since it is switched to, even if the record carrier on which the two-dimensional barcode is recorded is placed on the scanner at an angle, Without replacing the record carrier, it is possible to skew correction.

Further, since the left T sequence can be switched to the right T sequence in real time, high speed processing is possible. Further, since the correction is performed at the time of generating the T sequence, it is possible to determine the start pattern or the stop pattern in the process after the T sequence and to interpret the signal. Therefore, since it does not affect the basic algorithm of PDF-417, it is versatile.

According to the second aspect, when the entire symbol is read obliquely with respect to the scanning line, if there is only the start pattern first, the left reading T sequence is generated and the stop pattern appears. Reverse right reading T when
After the sequence is generated to the last line and the symbols are read, the first time the starting pattern is detected, the symbols are read from the left to generate the left T sequence,
The generation of the left T sequence for each scanning line proceeds by detecting the stop pattern at the timing of mixing the T sequences, and when the stop pattern is detected, the symbol is read from the right at that point to generate the right T sequence. Let
Alternatively, if there is only the stop pattern at the beginning, the left T-sequence and the right T-sequence are generated in the reverse order to the above. Therefore, in the same manner as in claim 1, when the original is placed on the scanner at an angle. , Can be corrected without replacing the original.

In the first aspect, separate right and left T sequence generation buffers are required, but in the second aspect, the same effect can be obtained with one line buffer. further,
The switching of processing is performed when a stop pattern appears, and the switching timing is earlier than that of the structure of claim 1, so that high-speed processing can be generally supported.

[Brief description of drawings]

FIG. 1 is a schematic block diagram showing a reading device according to a first embodiment of the present invention.

FIG. 2 is a schematic block diagram showing a configuration of a decoding apparatus.

FIG. 3 is a flowchart showing the operation.

FIG. 4 is a schematic diagram showing an example of how T sequences are arranged.

FIG. 5 is a schematic diagram showing an example of how to read a T sequence.

FIG. 6 is a schematic diagram showing an example of stitching processing.

FIG. 7 is a schematic block diagram showing a configuration of a reading device according to a second embodiment of the present invention.

FIG. 8 is a flowchart showing the operation.

FIG. 9 is a schematic diagram showing an example of how T sequences are arranged.

FIG. 10 is a schematic diagram showing an example of how to read a T sequence.

FIG. 11 is a schematic view showing an example of stitching processing.

FIG. 12 is a diagram showing patterns of a plurality of PDF-417 symbols having different sizes.

FIG. 13 is a diagram showing a pattern that is a basis of a symbol configuration of a PDF-417 two-dimensional barcode.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Signaling device 2 Line sensor 3 Line buffer for read data 4 Left T sequence generation buffer 5 Right T sequence generation buffer 6 Start pattern detection means 7 Left / right switching selection means 8 All T sequence memory 9 Sorting means 13 Line buffer for read data 14 Start Pattern Matching Means 15 Stop Pattern Matching Means 16 T Sequence Generation Buffer 17 All T Sequence Memory 18 Sorting Means

Claims (3)

[Claims] 1. A line sensor for optically reading a two-dimensional bar code on a record carrier, a line buffer for read data for storing a two-dimensional bar code symbol read by the line sensor, and the symbol on the left side. A T sequence generating buffer for generating a T sequence for each scan line and a T sequence for reading the symbol from the right side.
A right T sequence generation buffer that generates a sequence for each scanning line, a start pattern detection unit that detects a start pattern provided at the left end of the symbol, and a time point when the start pattern is detected by the start pattern detection unit. Of the left T-sequence, the left-right switching selection means for switching to the right T-sequence at the time when the symbol to be read is still present and the start pattern is no longer detected, and the scanning line in which the left and right T-sequences are mixed. A two-dimensional code reading device, comprising: a decoding processing unit that decodes data. 2. A line sensor for optically reading a two-dimensional bar code on a record carrier, a line buffer for read data for storing a two-dimensional bar code symbol read by the line sensor, and a line buffer for the line buffer. Start pattern matching means for matching the presence or absence of a start pattern provided at the left end of the symbol for each stored scan line, and a stop provided at the right end of the symbol for each scan line stored in the line buffer. A stop pattern matching means for checking the presence / absence of a pattern and a T sequence of symbols to be read from one of the start pattern and the stop pattern, which is detected first by the matching, is generated for each scanning line and the T sequence The symbol read from the other pattern side when the other pattern is detected during generation A two-dimensional code reader comprising a T sequence generation buffer for generating a T sequence for each scanning line, and a decoding processing means for decoding the data of the scanning lines in which the left and right T sequences are mixed. . 3. The reading of the two-dimensional code according to claim 2, wherein the T sequence generation buffer is configured to generate only a left T sequence read from the left end of the symbol when the start pattern and the stop pattern are detected at the same time. apparatus.