2D barcode technology and its application
The one-dimensional barcode only expresses information in one direction (generally the horizontal direction), but does not express any information in the vertical direction. Its certain height is usually for easy alignment of the reader.
The application of one-dimensional bar code can increase the speed of information entry and reduce the error rate, but one-dimensional bar code also has some shortcomings:
* Small data capacity: about 30 characters
* Can only contain letters and numbers
* Barcode size is relatively large (space utilization is low)
* The barcode cannot be read after being damaged
Bar codes that store information in two-dimensional spaces in the horizontal and vertical directions are called 2-dimensional bar codes.
Like one-dimensional bar codes, two-dimensional bar codes have many different encoding methods, or code systems. As far as the coding principles of these coding systems are concerned, they can generally be divided into the following three types
1. Linear stacked two-dimensional codes are generated by stacking multiple one-dimensional codes in the longitudinal direction based on the principle of one-dimensional bar code. Typical code systems are: Code 16K, Code 49, PDF417, etc.
2. The matrix two-dimensional code is encoded in a rectangular space through the different distribution of black and white pixels in the matrix. Typical code systems are: Aztec, Maxi Code, QR Code, Data Matrix, etc.
3. Postal codes are encoded by bars of different lengths, mainly used for mail encoding, such as: Postnet, BPO 4-State.
In many types of two-dimensional barcodes, commonly used code systems are: Data Matrix, Maxi Code, Aztec, QR Code, Vericode, PDF417, Ultracode, Code 49, Code 16K, etc., among which:
* Data Matrix is ​​mainly used for the identification of small parts in the electronics industry. For example, this code is printed on the back of Intel's Pentium processor.
* Maxi Code was developed by the United Parcel Service (UPS) company for sorting and tracking of parcels.
* Aztec is launched by the Welch Allyn company in the United States and can accommodate up to 3832 numbers or 3067 alphabetic characters or 1914 bytes of data.
Below, we take the PDF417 code as an example to introduce the characteristics and features of the two-dimensional barcode.
A) Introduction to PDF417
The PDF417 code was invented by Dr. Yinying Wang, a Chinese student in the United States. PDF is the abbreviation of the three words of English Portable Data File, which means "portable data file". Because each symbol character constituting the barcode is composed of 4 bars and 4 spaces, if the narrowest bar or space constituting the barcode is called a module, the total number of modules in the above 4 bars and 4 spaces Set to 17, so called 417 code or PDF417 code.
B) Features of PDF417
1. Large information capacity PDF417 code can express not only letters, numbers, ASCII characters, but also binary numbers. In order to make the encoding more compact and improve the information density, PDF417 has three formats when encoding:
* The expanded alphanumeric compression format can accommodate 1850 characters;
* Binary / ASCII format can hold 1108 bytes;
* Digital compression format can accommodate 2710 numbers.
2. Error correction capability One-dimensional bar codes usually have a check function to prevent misreading, and will be rejected once the bar code is defaced. The two-dimensional barcode not only prevents errors, but also corrects errors. Even if the barcode is partially damaged, the correct information can be restored.
3. Printing requirements are not high, ordinary printing equipment can print, fax can also read.
4. Can read PDF417 codes with various reading devices. It can be read with laser reader with raster, image reader with linear and surface scanning.
5. The size can be adjusted to suit different printing spaces
6. The open code system has formed an international standard, and China has also formulated a national standard of 417 yards.
Three) PDF417 error correction function
The error correction function of the two-dimensional barcode is realized by repeating (redundant) part of the information. For example, in the PDF417 code, in addition to the information of this line, there is some information reflecting the characters (error correction codes) in other positions. In this way, even when a part of the barcode is damaged, the information can be restored by the error correction code that exists in another location.
The error correction capability of PDF417 is divided into 9 levels from 0 to 8 according to the number of error correction codes. The higher the level, the more correction code words, the stronger the correction capability, and the larger the bar code. When the correction level is 8, even 50% of the bar code can be read correctly.
Four) Several variants of PDF417
PDF417 also has several variants of code systems:
* In the relatively "clean" environment of PDF417 truncated codes, the possibility of barcode damage is very small, you can omit the line indicator on the right and reduce the terminator.
* PDF417 microcode further reduced PDF code.
* Macro PDF417 code When the file content is too long to be represented by one PDF417 code, it can be represented by a macro PDF417 code containing multiple (1 to 99999) barcode blocks.
Advantages of 2D barcodes
As can be seen from the above introduction, compared with the one-dimensional bar code, the two-dimensional bar code has obvious advantages. In summary, there are the following aspects:
A) Larger data capacity
PDF417 code contains all the text in the text box.
B) Beyond the alphanumeric limit
C) The relative size of the barcode is small
D) Ability to resist damage
Application of 2D barcode
A) Application in the transportation industry
A typical transportation business process usually goes through: supplier-> freight forwarding, freight forwarding-> freight company, freight company-> customer, etc. Several processes are involved in the processing of shipping documents in each process. The shipping document contains a large amount of information, including: shipper information, consignee information, cargo list, shipping method, etc. The premise of document processing is data entry. The manual keyboard entry method has the problems of low efficiency and high error rate, which can no longer meet the requirements of modern transportation industry.
The two-dimensional bar code provides a good solution in this regard. The content of the document is compiled into a two-dimensional bar code, which is printed on the shipping document, and the bar code is scanned by the two-dimensional bar code reader in each link of the transportation business. Entry into the computer management system is fast and accurate.
In the United States, although the EDI application revolutionized the core part of the business process, it unfortunately ignored the key role of the process-the freight company. Many EDI messages are always late for freight forwarders, so that the shipment of goods and the generation of customer documents are affected by the inability to confirm accurate shipment order information in a timely manner.
The American Freight Association (ATA) therefore proposed the paper-based EDI system. The sender compiles the EDI information into a PDF417 barcode label and submits it to the freight forwarder. By scanning the barcode, the information is immediately transferred to the freight forwarder's computer system. All this happens at the right time and in the right place, which greatly improves the efficiency of the entire transportation process.
B) Application of ID card
The US Department of Defense has printed PDF417 codes on military identification cards. The cardholder's name, military rank, photo and other personal information are compiled into a PDF417 code and printed on the card. The card is used to manage access to important places and hospital management.
The advantages of this application are real-time data collection, low implementation cost, card damage (such as shooting) can also be read, and anti-counterfeiting.
The resident ID card of the Hong Kong Special Administrative Region of China also uses PDF417 code. Other applications, such as business licenses, driving licenses, passports, temporary residence permits for migrants in cities in China, and medical insurance cards, are also good applications.
C) Application of documents and forms
Every broker of Seimei Insurance Company in Japan carries a laptop when meeting customers. Each insurance policy and agreement are made and printed on the computer. When they return to the office, they need to manually enter the policy data into the company's mainframe.
In order to improve the accuracy and speed of data entry, they compile the policy content into a PDF417 barcode while printing the policy, and print it on the document, so that they can scan the barcode using a two-dimensional barcode reader to enter the data into the host.
Other similar applications include: customs declaration forms, tax declaration forms, various application forms from government departments, etc.
D) Asset tracking
American Steel Pipe Company has different types of pipelines in various locations that need to be maintained. In order to track each tube, they compiled the tube number, position number, manufacturer, length, grade, size, thickness, and other information into a PDF417 barcode, which was labeled and attached to the tube. When the pipe is removed or installed, the operator scans the barcode label and the database information is updated in a timely manner.
Factories can use 2D barcodes to track production equipment; hospitals and clinics can also use 2D barcode labels to track equipment, computers, and surgical instruments.Porcelain Dinnerware Set
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