KR20040014336A - Methods and systems for encoding and decoding data in 2d symbology - Google Patents

Abstract

PURPOSE: A method and a system for encoding/decoding a 2-D(Dimensional) barcode are provided to convert the 2-D barcode into a signal characterized in having various signal widths and heights, various printing resolutions, various damage protection levels, a large information storage region, and a high redundancy freedom degree, read by a scanner of a line base, and recognized by a contact/non-contact scanner. CONSTITUTION: A rectangular 2-D barcode includes rectangular barcode elements comprising bars and spaces. The rectangular 2-D barcode has a vertical and a horizontal axis, and includes an upper border(510), a lower border(520), a left border(530), a right border(540), a bit-stream data region(550), and data segment partitions(560). The 2-D barcode data is stored in a format of the bit-stream of codeword data. The bit-stream of the codeword data includes a set of the arranged rows of a 9-bit codeword. The bit-stream data region is partitioned into the data segments separated by the data segment partitions.

Description

METHODS AND SYSTEMS FOR ENCODING AND DECODING DATA IN 2D SYMBOLOGY}

FIELD OF THE INVENTION The present invention generally relates to optically encoded codes, and more particularly to methods and systems for encoding and decoding data into two-dimensional codes.

In today's high tech world, more processes are performed automatically by a computer. This growing demand for automation has created a strong demand for new technologies. Bar-code is one of the techniques used to automate data entry.

A bar-code code is a pattern in which a series of bars of varying widths are spaced from each other by spaces of varying widths, where the bars and spaces represent each other, representing a string of binary ones and zeros. Has different light reflecting properties. Bar-code symbols are printed directly on the object or on labels attached to the object. Bar-code codes are typically read by an optical technique such as a laser beam, charge coupled device (CCD), or contact image sensor (CIS) camera. A typical laser-based bar-code reader uses a photo-sensor to convert bars and voids into an electrical signal while moving across the bar-code. The reader then measures the relative widths of the bars and spaces, converts the different patterns back to normal characteristics, and sends them to a computer or portable terminal for further processing. These bars and spaces have a minimum width, to be properly decrypted by the scanner. The minimum width is called a "unit" or "module". Spaces and bars are multiple "units" or "modules".

The bar code described above is one dimensional. Information encoded in one-dimensional (1D) bar-code is represented only by the widths of the bars and spaces extending into a single dimension. Since all bars and voids have a uniform height in their vertical direction, the information is stored only in the horizontal direction of the 1D bar-code. In general, 1D bar-code is widely used as an indication for associating physical objects with a database containing detailed information. As one-dimensional, the 1D bar-code can only store a very limited amount of information, such as, for example, a postal code, social security number, or serial number.

As the demand for information technology increases, there is a growing interest in removing associated databases and storing more information in the code itself. As a result of this demand, two-dimensional (2D) bar-code technology has emerged from the expansion of 1D bar-code. 2D bar-code codes are generally square or rectangular patterns that encode data in two dimensions. These fall into two general categories, one is "stacked bar-code", where the other 1D bar-code is installed like a cake layer on top of the 1D bar-code. Matrix bar-code "is designed to be a true two-dimensional matrix.

One of the most commonly used "stacked bar-codes" is PDF 417 as shown in FIG. 1A. A detailed description of PDF 417 can be found in US Pat. No. 5,304,786. PDF 417 includes multiple code segments. Each one is named PDF 417 because it consists of four bars and four spaces with a total width of 17 modules. This has a high tolerance for corrupted code when a high level of error correction is designed in the code. In theory, PDF 417 can store 2000 characters per sign, but the practical limit does not exceed 350 characters. It is required to print a PDF code using a high resolution printer such as a laser or a thermal transfer printer. PDF 417 can be read by a camera (CCD or CMOS), and by a modified portable laser or CIS scanner.

The QR code (Quick Response Code) is an example of a "matrix bar-code" developed by Nippondenso ID Systems. As shown in Figure 1B, the QR code code is square in shape, dark and bright at three corners of the code. The squares can easily be identified by their overlapping finder pattern Because of the finder pattern, the QR code code can be read very quickly by the CCD array camera The disadvantage is size, up to 177 squarely separated modules The corresponding maximum storage capacity is 2956 bytes encoded with a 750 byte lowest level error correction code.

Scanners based on CCD or CIS cameras are particularly suitable for reading 2D bar-codes. In general, scanners convert light (human visible) into 0s and 1s (computer processable). In other words, scanners convert data from analog format to digital format. All scanners operate on the same principle of reflection or transmission. The scanning object to be scanned is placed in front of a scanner comprising a light source and a sensor. The amount of light reflected or passed by the scanning object is picked up by the sensor and converted into a signal proportional to the light intensity.

One of the factors affecting scanner performance is scan resolution. Scan resolution is related to the detailed precision a scanner can achieve and is usually measured in dots per inch (dots per inch). The more dots per inch the scanner can resolve, the finer the resulting image will be. Scanners typically have optical elements for each pixel. Scanners claiming a horizontal optical resolution of 600 dpi are alternatively referred to as 600 pixels per inch (ppi), which is also referred to as the scanner's x-direction resolution. For a scanner with a maximum scanning width of 8.5 inches, the scan head has an array of 5100 optical elements. The scan head is mounted on a transport array that moves across the scanning object. Although the process may appear to be a continuous movement, the head moves by a portion of one inch at a time, making a reading between each movement. The number of physical elements in the sensor array determines the horizontal sampling rate, and the number of steps per inch determines the vertical sampling rate, referred to as the y-direction resolution of the scanner. The resolution of the scanner is based on its x- and y-direction resolutions.

Stores more information, buil-in redundancy, multiple levels of tamper-proof protection, flexible width and length codes, and features portable line-based contacts or non-contact scanning It would be desirable to have a novel bar-code.

Because of the proliferation of passive scanning devices, it is desirable to scan 2D bar-codes with a handheld scanner. However, some problems exist. A phenomenon known to lose vertical sync 200 due to limited height elements in scanning 2D bar-code codes is shown in FIG. The 2D bar-code 210 overlaps with a set of parallel scan lines 220. In general, the angle between the scan line 220 and the horizontal axis of the bar-code 210 is not zero in the case of a portable scanning device. Due to the limited height of the bar-code elements, some scan lines 230 traverse across two rows of bar-code elements. As a result, these scan lines 230 are not available. It is desirable to have a 2D bar-code decoding method that avoids the problem of losing synchronization. It is also desirable to decode 2D bar-codes efficiently and effectively.

<Overview of invention>

In this section, we summarize some features of the present invention and briefly introduce some preferred embodiments. Simplifications and omissions may be made to avoid obscuring the purpose of this section. Such simplifications and omissions do not limit the scope of the invention.

The present invention relates to a process, method, system, and software product for encoding and decoding 2D bar-codes. According to one aspect of the invention, at least 1) variable width and height signs, 2) variable print resolution, 3) multiple tamper resistant levels, 4) large information storage, 5) high redundancy, 6) line based scanning apparatus A novel 2D bar-code code is provided having features including readability by, 7) readability by a contact scanning or non-contact scanning device.

According to one embodiment, the 2D bar-code includes an upper border, a lower border, a left border, a right border, a bit-stream data area, and a plurality of data segment dividers. Unique patterns of the upper and lower edges are used to enable the scanning device to recognize the orientation of the 2D bar-codes, i.e. whether the bar-codes are upside down or upside down. Corresponding pairs of a plurality of positioning holes are used on the left and right edges so that the scanning device calculates the coordinates of the data element. The bit-stream data area contains bar-code information in the form of a 9-bit "codeword" of aligned rows, with a data structure of three rows and three columns of data elements as shown in FIG. The order of the bits is stored around the row, left to right, and top to bottom.

The width and length of the 2D bar-code is controlled by the amount of information carried in the bit-stream data area. Many measures to prevent physical damage are adopted in 2D bar-code. The first measure is to split the data bit-stream into a plurality of equally sized data segments. A set of data segment control information is added to each data segment. As a result, redundancy is provided by repeating in each data segment key control information related to the entire bar-code.

Another measure is to adopt an industry standard error correction method (eg, Reed-Solomon function) within each data segment. Thus, if any part of the bar-code is not recognizable, error correction can reproduce the lost information using an error correction codeword that is within the uncorrupted portion of the bar-code. There are many different levels of error correction. Depending on the applicable environment, an appropriate level of error correction may be selected. In order to ensure high reliability for decoding, an independent error correction scheme for data segment control information is adopted. Instead of storing the codewords in sequential order, the codewords are stored in an interleaved order so that consecutive data is spread out over a wide area. As a result, the possibility of corruption of continuous data is reduced, and the possibility of reproducing corrupted data through error correction increases.

When a wide concentration of bars (dark color) occurs in one particular part of the bar-code, the scanning device will not be able to capture the blanks in this focused part. To solve this problem, a masking or X-OR bit operation is performed between the bit-stream of the codeword data and the predetermined mask to hide some of the concentrated bars. The masking mechanism is different from the conventional one. This is based on the codewords of three rows and three columns. Each type of mask consists of a pair of masking codewords. Three pairs of masking codewords are shown in FIGS. 10A, 10B, 10C. They are arranged in a chessboard style, with black and white squares representing the pair of masking codewords. This arrangement is illustrated in FIG. 10D.

According to another feature of the invention, different decoding methods are disclosed. One method is used to decode 2D bar-codes after the entire 2D bar-code code has been scanned and stored. Another method is used to decode 2D bar-codes while the 2D bar-codes are scanned. According to one embodiment, these decoding methods are combined as a software product loaded on the scanning device to decode the 2D bar-code efficiently and effectively.

According to another feature of the invention, a set of parallel positioning lines with equal spacing is attached to the 2D bar-code. These positioning lines are used to guide the scanning device to properly decode the 2D bar-code.

According to another feature of the invention, the 2D bar-code may be divided into visible marks corresponding to different paragraphs of the article.

One of the objects, features, and effects of the present invention is to provide a code having flexible features and suitable for scanning.

Other objects, features, and effects of the present invention will become apparent from a review of the detailed description of the embodiments of the present invention with reference to the accompanying drawings.

These and other features, aspects, and effects of the present invention will be readily understood by reference to the following detailed description, claims, and accompanying drawings.

1A shows an example of a PDF417 2D bar-code.

1B shows an example of a QR code.

2 is a diagram showing the intersection of rows of 2D bar-code elements and scan lines.

3 shows two examples of 9 bit codewords.

4 shows an example of a 2D bar-code according to the present invention.

FIG. 5 is a detailed anatomy of the 2D bar-code of FIG. 4. FIG.

6A-6C show exemplary patterns of upper and lower borders.

7A and 7C show two examples of the start code of the upper edge in detail.

7B and 7D show two examples of the end code of the lower edge in detail.

8 shows a table showing a combination between an error correction codeword and a data codeword at different error correction levels.

9A lists the interleaved storage scheme for the bit-stream of codeword data.

9B and 9C show a data structure of data segment control information.

10A-10D illustrate various masks used in the present invention.

11 shows a flowchart of the bar-code encoding method.

12A shows a flowchart of a method for decoding a 2D bar-code.

12B and 12C show flowcharts of a method of decoding a 2D bar-code without first scanning the 2D bar-code.

13 shows a detailed view of locating the positioning holes.

14A shows an alternative positioning teeth used for 2D bar-code.

14B and 14C show two examples of positioning lines attached to a 2D bar-code.

15 shows a 2D bar-code with visible segmentation marks corresponding to different paragraphs of the encoded article.

16 shows a detailed geometry for explaining how the positioning lines guide the scanning device.

17A and 17B show the relationship between adjacent positioning lines and successive scanning lines.

18 shows a schematic chart of a scanner head corresponding to a 2D bar-code.

19 shows a typical block diagram of a scanner.

<Explanation of symbols for the main parts of the drawings>

400: 2D Bar-Code Code

510: upper border

520: lower border

530: left border

540: right border

550: bit-stream data area

560: a plurality of data segment dividers

In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to one skilled in the art that the present invention may be practiced without these specific details. The description and representations herein are the usual means used by those skilled in the art and by those skilled in the art in order to best convey the content to those skilled in the art. Moreover, in the case of known methods, procedures, components, and circuits, no description will be made to avoid unnecessarily obscuring the features of the present invention.

Reference herein to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the present invention. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment, nor need to be separate or alternative embodiments that are mutually exclusive of other embodiments. . Moreover, the order of blocks in the process flow charts or figures that represent one or more embodiments of the present invention does not inherently represent any particular order, and does not imply any limitations of the present invention.

Like parts are designated by like numerals in the drawings, and the present invention will now be described with reference to the drawings. 3 shows two examples of the data structure used for the 2D bar code code of the present invention. Each 9-bit codeword includes data elements arranged in three rows and three columns, each data element being one of dark and light colors. Each data element stores one bit of information. The order of the codewords is from left to right and top to bottom. To facilitate the description of the present invention, dark or light colored elements are referred to as bars or spaces. In one embodiment, the bar represents 1 and the blank represents 0. For example, the value of codeword 310 is binary 010101010, or 0x0aa in hexadecimal, and the value of another codeword 320 is binary 101111001, or 0x179 in hexadecimal.

In accordance with one embodiment of the present invention, FIG. 4 illustrates a rectangular 2D bar-code sign 400 comprising a plurality of rectangular bar-code elements of bars and spaces. Rectangular 2D bar-code symbol 400 has two major axes, ie horizontal axis 410 and vertical axis 420. An exploded view of the 2D bar code code 400 is shown in FIG. 5. The components of the 2D bar code code 400 include an upper edge 510, a lower edge 520, a left edge 530, a right edge 540, a bit-stream data area 550, and a plurality of data segments. Includes parts 560. The 2D bar code code data is stored in the form of a bit-stream of codeword data. The bit-stream of codeword data includes a set of aligned rows of 9 bit codewords. The bit-stream data area 550 is divided into a plurality of data segments separated by data segment dividers 560.

Two examples of the upper rim 510 are shown in FIGS. 6A and 6B. The upper border 510 includes two basic components: start code pattern 601 and end code pattern 605. An exemplary upper border includes two start code patterns 601 and one end code pattern 605, as shown in FIG. 6A. 6B shows a top border of another example that includes three start code patterns 601. The number of start code patterns 601 varies depending on the amount of data carried in the 2D bar-code code. The minimum number of start code patterns 601 is one. And there is no theoretical maximum number of start code patterns 601. However, practical limitations can be controlled by the width of the carrier (eg the width of the paper). In a similar design, the lower border 520 includes at least one end code pattern 691 and one termination code pattern 605. An exemplary lower block 520 is shown in FIG. 6C. Termination code pattern 605 includes one three-module wide bar.

The start code pattern 601 and the end code pattern 691 are both directional. The start code pattern 601 has a structure with alternating bars and six spaces with a combination of distinct widths. The end code pattern 691 has a similar structure having a combination of different widths. As shown in FIG. 7A, the widths of the six components for the start code pattern 601 are 3: 1: 1: 2: 2: 2 modules. FIG. 7B shows the end code pattern 691 with widths of 3: 2: 2: 1: 1: 2 modules for bars and spaces. Therefore, the overall width W of the bar-code is the sum of all widths of the start / end code patterns and the end code pattern.

W = 11 * N +3 modules

Where W is the width of the bar-code and N is the number of start / end code patterns in the bar-code.

Another embodiment of the start code pattern and the end code pattern is shown in FIGS. 7C and 7D. These consist of eight bars and blanks arranged alternately with a combination of different widths. The width of the eight components for the start code pattern shown in FIG. 7C is 3: 2: 1: 1: 1: 2: 2 modules. 7D shows an example where the widths of the end code pattern are 3: 1: 2: 3: 2: 2: 1: 1 modules for bars and spaces. In this embodiment, the total width W of the bar-codes is calculated as follows.

W = 15 * N +3 modules

Where W is the width of the bar-code and N is the number of start / end code patterns in the bar-code.

Referring again to FIG. 5, each of the left edge 530 and the right edge 540 has the same positioning block that is three modules wide and whose length covers the height of the bar-code. When the border 530 or 540 is viewed as three columns, both outer columns of the border are bars and the middle column contains bars and spaces alternately arranged according to a predetermined pattern. In one embodiment, the pattern is one bar and one blank. In another embodiment, the pattern may be constructed by placing multiple bars alternately with multiple blanks. In essence, alternating spaces within the left and right borders are provided to locate the data elements between the left and right borders.

In order to increase the reliability of the decoding of the bar-code, the bit-stream data area 550 is divided into a plurality of equally sized data segments by the data segment dividing unit 560, the data segment dividing unit 560 A row of bars spanning the full width of a bar-code. The Reed-Solomon error correction method is applied for physical tampering with bar code codes. In one embodiment of the invention, several optional options of the Reed-Solomon scheme can be employed to prevent tampering of the data elements. 8 shows an exemplary list of Reed-Solomon schemes of different levels for 127 codeword data. It is apparent that the higher the error correction level, the less data can be stored within a given bar-code. The selection of the appropriate option depends on the physical environment in which the bar code is placed. Error correction codewords are calculated based on the level of the selected error correction scheme.

Most bar code corruption occurs in concentrated areas. One way to reduce the probability of successive destruction of data is as follows. That is, a) the data segment is divided into groups of a plurality of fixed length data blocks (e.g., 127 codewords), and b) the plurality of groups are stored in an interleaved order so that successive codewords Do not save sequentially. An example scheme for storing three groups of 127 codeword data in a continuous manner is shown in FIG. 9A. The number of groups can be any positive number.

In addition to all codeword data stored in the bit-stream data area 550 of FIG. 5, a set of key control information is added to each data segment to improve decoding reliability. 9B illustrates one embodiment of a control information data structure. Because of the importance of this control data, a separate high level error correction code is used independent of the error correction scheme adopted for the codeword data. In Figure 9B, bits e0 through e9 represent error correction codes, bits a0, a1, a2, a3, and a4 represent the total number of data segments in the bar-code code, and bits b0, b1 are selected. Represents an error correction level, bits b2 represent interleaf toggles, bits b3 and b4 represent mask types, and bits c0 to c4 represent data segment numbers of the current data segment. 9C shows another embodiment of a control information data structure. Bits A3, A2, A1, A0 and B3 represent the data segment number of the current data segment, bits B2, B1, B0, C3 and C2 represent the total number of data segments in the bar-code sign, C1, C0 and C3 represents the selected error correction level, bits D2 and D1 represent the mask type, and D0 represents the insertion toggle. In this embodiment, the control information data is first arranged into seven three-row, three-column codewords, and then the three remaining spaces are filled with zeros. Control information is repeated in each data segment redundantly to ensure the availability of the information, even if the bar-code is physically handled.

When a huge number of bars only focus on a very small number of spaces (light colors) and certain parts of the 2D bar-code code, the scanning device may cause them to miss spaces, resulting in inaccurate information. To minimize this concentration of one color (all bars or all blanks), in one embodiment of the present invention, masking bars by applying masking or XOR bit operations with a predetermined mask on the bit-stream codeword data. Schemes are provided. 10A-10D show exemplary masks used in embodiments of the present invention.

Reference is made to a flowchart 1100 for encoding 2D bar-code according to one embodiment of the present invention, shown in FIG. First, the binary data file is converted into a binary bit-stream codeword at step 1110. Then, at step 1120, based on the error correction level selected by the user, error correction codewords are calculated and added to each bit-stream (e.g., 127 codewords) of the codeword data. This group of bit-stream codeword data may be stored in interleaved order at step 1130. Then, at step 1140, the entire bit-stream of codeword data is divided into multiple data segments based on the amount of information carried in the bar-code. In step 1150, filler codewords are appended to the last data segment, if necessary, to ensure that all data segments have the same size. Then, in step 1160, a masking or XOR bit operation is applied to the bit-stream codeword data with a preselected mask to generate a new bit-stream codeword of the data. Then, in step 1170, control information codewords are added to each of the data segments. In step 1180, an upper border, a lower border, a left border, and a right border are added. Finally, in step 1190 a 2D bar-code code is printed.

12A shows a flowchart or process 1200 for entirely decoding a 2D bar-code code. In step 1205, the entire 2D bar-code code is scanned and stored as an image and then optically augmented. In step 1210, upper and lower borders are detected and their corresponding coordinates are stored. In step 1215, the angle between the scan line and the horizontal axis of the bar-code is measured. Based on the beginning and ending code patterns, the orientation of the stored bar-code image (eg, upside down or upside down or flipped in and out) is determined, and the print resolution of the stored image is determined. In step 1220, the first data segment divider in the stored image is found. In step 1225, coordinates of all data elements in the bit-stream data region are calculated using the first data segment divider and the set of positioning holes on the left and right edges. In step 1230, an error correction process for control information is performed to extract key control information, such as error correction level, mask type, insertion toggle, total number of data segments, and current data segment number. Then, in step 1235, the bit values (bars / blanks) of the data elements in the bit-stream data area are read according to their coordinates calculated in step 1225 and restored to the bit-stream of codeword data. In step 1240, the bit-stream of the original codeword data is reestablished by applying re-sequencing, masking or XOR bit operations from the interleaved order, and error correction operations to the bit-stream generated in step 1235. Finally, the bit-stream of codeword data is converted into original binary data.

12B and 12C collectively illustrate a flowchart or process 1250 for decoding a 2D bar-code code, in accordance with another embodiment of the present invention. One unique feature of this process is that the bar-code is decoded as it is scanned. In step 1252, the scanning device scans a new line of 2D bar-codes and stores the scanned image in temporary storage. In step 1254, the scanned image is compared with the lower border pattern. If a match occurs, the scanned 2D bar-coded image is flipped up and down. Decoding is performed only for the entire 2D bar-coded image as described in FIG. 12A. Otherwise, if no match is found, in step 1256 this scanned image is compared with the upper border pattern. If they do not match, the process returns to step 1252 to obtain another scanned image. If the upper edge is found, then in step 1258 it is determined whether the 2D bar-code is a mirror image. If it is a mirror image, decoding may only be performed by the method of FIG. 12A. Then, in step 1260, the print resolution of the 2D bar code code is determined. In step 1262, the scanning device moves to obtain a scanned image of another line based on the printed resolution.

In step 1264, the scanned image is examined to determine whether it is a data segment divider, which is a solid bar across the width of the 2D bar-code code. If not, then the process returns to step 1262 to obtain a scanned image of the new line. Otherwise, if determined to be a data segment divider, the process begins to decode a bit-stream of codeword data carried in the 2D bar-code code. In step 1266, corresponding positioning holes of the left and right edges are detected. Then, in step 1268, the set of control information is read using the positioning holes and the data segment division as a guide. After an error correction process is performed on the control information portion of the bit-stream of codeword data, control information is extracted, such as the total number of data segments, the error correction level, the insertion toggle, the mask type, and the current data segment number.

In step 1270, a check is made to see if the correct data segment is being scanned and decoded. If not, the process branches to process 1200 to decode the 2D bar-code code as a whole. In step 1272, the interleaved data storage order is checked. Again, if the bit-stream codewords of data are stored in interleaved order, decoding should be performed according to the method for decoding the entire 2D bar-code. After passing both checks, in step 1274, one row of data elements are read. The process continues at step 1276 by checking whether the next line of the scanned image is a data segment segment. If not, then the process returns to step 1274. Otherwise, after performing the error correction selected in step 1278, the original bit-stream codeword of the data for the current data segment is finally recovered. In step 1280, a final check is performed. If the lower edge is not detected in the next line of the scanned image, steps 1266 to 1280 are repeated to decode the new data segment. Otherwise, if the lower edge is detected, decoding is performed.

Referring to FIG. 13, a detailed geometry for illustrating a procedure for determining coordinates of data elements of a 2D bar-code using corresponding pairs of positioning holes in the left and right edges of a stored 2D bar-code image is illustrated. . The data segment splitter 1310 is detected using four vertical traces V1, V2, V3, and V4 that are spaced at equal intervals in the vertical direction of the scanned image. The left edge 1320 is detected using four horizontal traces H1, H2, H3, and H4 that are spaced at equal intervals in the horizontal direction of the scanned image. Similarly, right border 1330 is detected using another set of four horizontal traces H5, H6, H7, and H8 spaced at equal intervals. Using the coordinates of these straight lines, the intersection 1340 of the left and upper edges and the intersection 1350 of the right and upper edges are determined. Based on the print resolution ppi of the rectangular bar-code elements and the coordinates of these two intersections, an approximate position of the first pair of positioning holes is evaluated. Then by simply averaging all the light color pixels in the evaluated area, the coordinates Xp, Yp of the first pair of positioning holes are calculated as follows.

Xp = (1 / N) * Sum (Xi)

Yp = (1 / N) * Sum (Yi)

Where N is the total number of white pixels in the evaluated area of the positioning hole, and xi, yi are the coordinates of the white pixels in the evaluated area of the positioning hole.

Using the coordinates of the pair of known positioning holes, all the coordinates of the 2D bar-code data elements are calculated. The data for the stored image can then be read very efficiently. After completing the calculation of the coordinates of the first row of data elements, the remaining rows are deduced inductively.

14A shows a 2D bar-code 1404 sandwiched between a pair of positioning teeth 1402. This positioning tooth 1402 is used to guide the scanning device to correct image stretching and compression. Under normal circumstances, the number of rows in the scanned image is evenly distributed between the positioning teeth. However, in special circumstances, the scanned image may be distorted due to the distance and angle between the scanning device and the 2D bar-code code. Meanwhile, the scanned image may be stretched. In other words, there are more rows scanned between specific positioning teeth than others. On the other hand, the image can be compressed. That is, the scanned rows may be lost between certain positioning teeth. Based on the fact that it has a uniform distribution for all positioning teeth, some rows may be added by stretching out the stretched region and extra rows by extrapolating adjacent scanned rows in the compressed (compressed) region.

Referring to FIG. 14B, a set of positioning lines 1410 is attached to the left side of the 2D bar-code 1420. These positioning lines include a plurality of equidistantly spaced parallel lines having a different slope from the horizontal axis of the 2D bar-code code 1420. Positioning lines may be located on one or both sides of the 2D bar-code sign 1420. 14C, according to another embodiment, illustrates positioning lines 1430 having a color different from that used for dark bars in a 2D bar code, on the 2D bar code code 1440. Decoding of the positioning lines and the 2D bar-code data elements is based on the reflection of the scanning light of different colors. For example, a 2D bar-code uses blue bars and white spaces. Overlapping positioning lines can be printed with a special black ink. When the scanning device scans the 2D bar-code sign using a blue light source, the black positioning lines will absorb blue light while the bars and voids will both reflect blue light. Therefore, the positioning lines are first read using a blue light source in the scanning device before attempting to read the bar-code data with the infrared light source. This is because infrared light passes through a special black ink, but is reflected differently in blue and white. Using two different light sources, the scanning device can read bar-code data elements and positioning lines in two different paths.

Referring to FIG. 15, a 2D bar code code 1510 having a plurality of visible physical segmentation marks 1520 for separating information stored in the 2D bar code 1510 is shown. According to one embodiment, each portion of the separated bar-code corresponds to a different paragraph of the article.

An exemplary use of the positioning lines of FIGS. 14B and 14C is shown in FIG. 16, which depicts the geometry of positioning lines 1600, scan line 1620, and horizontal axis 1610 of 2D bar-code. The set of parallel positioning lines 1600 is intersected by the horizontal axis 1610 and the scan line 1620. Vertical distance 1640 between positioning lines 1600 is indicated as D. FIG. The distance 1630 on the horizontal axis between two intersections of the horizontal axis 1610 and the positioning lines 1600 is L. The distance 1650 on the scan line between two intersections of scan line 1620 and positioning lines 1600 is n. The angle between scan line 1620 and bar-code horizontal line 1610 is F. The angle between horizontal axis 1610 and positioning lines 1600 is E. The angle between positioning lines 1600 and scan line 1620 is G, which is the sum of angles E and F. The following equations are used to calculate the angles F and G.

F = 90-E-arcos (D / n)

G = arsin (D / n)

17A and 17B show how the scanning lines guide the scanning devices. In general, the resolution in the horizontal direction or the x direction of the 2D bar-code is determined by the resolution xDPI of the scanning apparatus. In the horizontal direction or the y direction of the 2D bar-code, the resolution is referred to as the y resolution, which is determined by yDPI, which is the sampling rate of the scanning device. In order to properly decode 2D bar-codes, the distance H between the two scanning lines should be H = 1 / y. For example, to achieve 300 dpi, the scanning device needs to scan the 2D bar-code once every 1/300 inch in the y direction. When the first scan line is crossed by two adjacent positioning lines, the distance n between these two intersections is recorded and used to calculate the angle G with the above-described formula. The scanner then compares the two consecutive scan line images shown in FIGS. 17A and 17B. Two consecutive scan lines, line A and line A + n, are shown in FIG. 17B. Corresponding images are plotted overlapping each other in FIG. 17A. Two vertices pixel B and pixel B + m represent the intersections of one positioning line and two consecutive scan lines. Therefore, the distance between vertices is the distance m pixels between two scan lines, which is m * x, where x is the distance between two consecutive pixels. Then, based on the geometry shown in FIG. 16, the y-direction distance V between the two scan lines is calculated as follows.

V = (m * x) * tan (G)

When the y direction distance V is equal to the sampling distance H, a new row of the scanned image is recorded. This process continues until the entire image is scanned.

Referring to FIG. 18 in conjunction with FIGS. 4 and 5, an exemplary CIS based scanner has a 448 pixel wide scanning head. For a bar-code element with a module width of 4 pixels, the mapping of the sensor to 2D bar-code is as follows. That is, 8 pixels to cover the blanks on both sides of the bar-code, 12 pixels to cover the left border 530 and the right border 540, and 408 pixels for the bit-stream data region 550, respectively. Is mapped. 408 pixels represent 102 data elements, because each element is 4 pixels. This means that 102 bits of information can be stored in one row of bar-code 400. In one embodiment, 36 rows of data elements are required to store 127 codewords. Using 4 pixels to represent one module as the width of the data element is based on the rule of thumb for the reliability of decoding of 2D bar-codes. In general, the length / width of the minimum 2D bar-code data element can be determined by the following formula.

BL> = 4 * (Rp / Rs) pixels

Where BL is the minimum dimension of the 2D bar-code data element, Rp is the printer resolution, and Rs is the scanner resolution.

Referring to FIG. 19, a typical scanning device 1900 may include a signal processing chip 1910, an image sensor 1920, a document detection module 1930, a flash memory 1940, an ADC module 1950, a RAM 1960, Test port 1970, and data port 1980. At the heart of the scanning device is a signal processing chip 1910 whose main function is to control all attachment modules, decode binary bar-code data, store decoded information in RAM 1960, and store the required data Output to port 1980. Based on the clock and SP signals sent from the signal processing chip 1910, the image sensor 1920 catches the voltage Vout generated from the light reflected by the scanned image. The resulting digital data Vin is then sent to the signal processing chip 1910. The document detection module 1930 generates a "paper detection" signal when detecting that a document is inserted. The signal processing chip 1910 controls the start and end procedures of scanning based on this "paper detection" signal. The software used by the signal processing chip 1910 is loaded into the flash memory 1940. The ADC module 1950 converts analog data into digital data. The test port 1970 is used to upload software. Data port 1980 is used to output data from RAM 1960 to another computer.

According to the present invention, a process, method, system, and software product for encoding and decoding 2D bar-code are provided. According to the invention, at least 1) sign of variable width and height, 2) variable print resolution, 3) multiple tamper resistant levels, 4) large information storage, 5) high redundancy, 6) read by line based scanning device Possibility, 7) A novel 2D bar-code code is provided which has the possibility of recognition by a contact scanning or non-contact scanning device.

In addition, a set of positioning lines is attached to the 2D code to guide the scanning device to decode the 2D code at an appropriate resolution.

While exemplary embodiments of the invention have been disclosed, those skilled in the art will clearly appreciate that various modifications and changes can be made to achieve the effect of the invention. Those skilled in the art will recognize that some components may be replaced by other components that provide the same functionality. You can see that it can be. The following claims define the scope of the invention.

Claims (29)

In the method for encoding a 2D code, Converting the binary data into codeword data of the first bit-stream; Calculating a set of error correction codewords from the first bit-stream based on a predetermined error correction level; Combining the first bit-stream and the set of error correction codewords to generate codeword data of a second bit-stream; Dividing the second bit-stream into a set of data segments of equal size; Adding a set of control information codewords into each data segment; Adding a data segment divider between the data segments; And Providing a top edge, a bottom edge, a left edge, and a right edge that divide the data segments, thereby generating a 2D code. 2D code encoding method comprising a. The method of claim 1, Reordering at least two said second bit-streams in an interleaved order. The method of claim 1, The second bit-stream is represented by bars and spaces, The method further comprises performing a masking or XOR bit operation on the second bit-stream with a predetermined mask to avoid concentrations in a particular area. The method of claim 1, For easy detection of the orientation of the 2D code, the upper border includes at least one start code pattern and one end code pattern, and the lower border includes at least one end code pattern and one termination code pattern. 2D code encoding method. The method of claim 4, wherein The start code pattern of the upper border and the end code pattern of the lower border include six alternating bars and spaces, the start code pattern being 3: 1: 1: 2: 2: 2 modules And a width ratio where the end code pattern is 3: 2: 2: 1: 1: 2 modules. The method of claim 1, And the left edge and the right edge are pairs of identical positioning blocks including bars and spaces arranged alternately according to a predetermined pattern. The method of claim 6, The second bit-stream is represented by bars and spaces in a data element region, and each of the bars and spaces in the left or right edge corresponds to one or more bars and spaces in the data element region. . The method of claim 6, Each of the bars or spaces in the left edge or the right edge facilitates the determination of the vertical resolution of the scanner used to scan the 2D code. The method of claim 6, Each of the bars or spaces in the left or right edge represents a vertical print resolution of the 2D code to the scanner, and the bars and spaces in the upper or lower border represent the horizontal print resolution of the 2D code to the scanner, so that the scanner A 2D code encoding method that can scan 2D codes more efficiently. The method of claim 6, Each of the bars or spaces in the left edge or right edge indicates whether the scanned image of the 2D code is distorted, and if the scanned image is distorted, facilitates correction of the scanned image. The method of claim 1, The second bit-stream is represented by bars and spaces in the data element region, and the method further comprises: Adding a set of parallel positioning lines spaced at equal intervals to one or both sides of the 2D code, the positioning lines as well as bars and spaces in the data element region as well as the orientation of the 2D code 2D code encoding method having an inclination different from a horizontal axis of the 2D code in order to facilitate the determination of. The method of claim 1, Superimposing a set of parallel positioning lines spaced at equal intervals on the 2D code, wherein the positioning lines have a different slope than the horizontal axis of the 2D code. The method of claim 12, And the positioning lines are different from the 2D code so that they can be easily determined from the scanner image of the 2D code by the scanner. The method of claim 1, The set of control information, The total number of data segments, Insert toggle, Preselected error correction level, The selected mask type, and Data segment number 2D code encoding method comprising a. The method of claim 1, Wherein each of the data segments comprises codewords that are a matrix of three rows and three columns with at least some of the bars and spaces. A method of decoding a 2D code comprising a plurality of bars and spaces in a data area representing a bit-stream of codeword data from a binary data file, the method comprising: The data area is partitioned by an upper border, a lower border, a left border and a right border, and a plurality of data segment dividers divide the bit-stream data area into a plurality of data segments, The method, Scanning the 2D code as a whole to generate and store an image; Retrieving the upper edge having a start code pattern and the lower edge having an end code pattern from the stored image; Determining a horizontal axis and a vertical axis of the image of the sign based on the start code pattern and the end code pattern; Calculating a scan line angle between the scan line and the horizontal axis of the stored image; Determining a print resolution from the stored image; Finding the plurality of data segment dividers in the stored image; Retrieving a set of control information from the data segments; Recovering the bit-stream of the codeword data from the data segments; And Converting the bit-stream of the codeword data into an original binary data file 2D code decoding method comprising a. The method of claim 16, Restoring the bit-stream of the codeword data, applying an error correction operation to the bit-stream of the codeword data. The method of claim 17, Restoring the bit-stream of the codeword data, if necessary, further comprising performing a masking operation on the bit-stream of the codeword data using a predetermined mask based on the control information. Decoding method. The method of claim 18, Calculating all coordinates for a plurality of data elements between the left edge and the right edge starting from a first segment divider; And Determining a plurality of said codeword information using said coordinates of said data elements 2D code decoding method further comprising. The method of claim 18, The scanning of the 2D code is performed by a scanner comprising software modules configured to determine the orientation of the 2D code and a memory space for the stored image. The method of claim 20, And the stored image is first processed by the software module according to the left and right edges to determine the bit-stream of the codeword data. A method of decoding a 2D code comprising a plurality of bars and spaces in a data area representing a bit-stream of codeword data from a binary data file, the method comprising: The data area is partitioned by an upper border, a lower border, a left border and a right border, and a plurality of data segment dividers divide the bit-stream data area into a plurality of data segments, The method, Scanning the 2D code to generate a first scan line of the scanned image; Retrieving the upper edge having a start code pattern and the lower edge having an end code pattern from the scanned image; Switching to a method for scanning the 2D code as a whole before decoding when it is determined that the scanned image is upside down or is a mirror image; (a) scanning the 2D code to generate a scanned image until a first data segment is detected; (b) retrieving a set of control information codewords for the first data segment after error correction; (c) if the first data segment is not sequential, or if the bit-stream data regions in the first data segment are stored in an interleaved order, switching to a decoding method that decodes the graphic coded image entirely; (d) retrieving a plurality of codeword information in the bit-stream data region using the coordinates of the data elements in a current data segment; (e) restoring a first portion of the first bit-stream of the codeword data for the current data segment Repeating steps (a) to (e) each time the data segment divider is detected until the lower edge is detected; 2D code decoding method comprising a. The method of claim 22, And said element of codeword data comprises a matrix of three rows and three columns of bars or spaces. The method of claim 23, wherein And the 2D code is expandable according to the binary data file. The method of claim 22, The control information, The total number of data segments, Insert toggle, Preselected error correction level, The selected mask type, and Data segment number 2D code decoding method comprising a. A method for guiding a scanning device to decode a 2D code, the method comprising: Providing parallel positioning lines spaced at equal intervals to the 2D code, the positioning lines having a different slope than the horizontal axis of the 2D code; And Scanning the 2D code with the positioning lines to produce a scanned image Method for guiding the 2D code decode of the scanning device comprising a. The method of claim 26, And the positioning lines are provided on at least one side of the 2D code. The method of claim 26, The positioning lines are superimposed on the 2D code and guide the 2D code decode of the index scanning device different from the color of the bars in the 2D code. A scanning device for decoding a 2D code having a set of positioning lines spaced at equal intervals, the scanning device comprising: Signal processing chip; A document detection module connected to the signal processing chip and transmitting a paper detection signal when the 2D code is present and present; An image sensor for generating an analog signal by detecting the 2D code; An analog-to-digital conversion (ADC) module for receiving and digitizing the analog signal from the image sensor to generate a digital image thereof in memory space; And Flash memory for storing decoding software Including, The decoding software, Detecting the positioning lines in the digital image; Determining the inclination of the positioning lines with respect to the inclination of the 2D code; And Determining an orientation of the 2D code Scanning device configured to perform.