Barcodes consist of a set of regularly arranged bars, spaces and corresponding characters. This data code consisting of bars and spaces can be read by machine and easily translated into binary numbers and decimal numbers. These bars and spaces can be combined in different ways to form different graphic symbols, that is, various symbol systems, also known as code systems, which are suitable for different occasions.
At present, the most commonly used codes are EAN, UPC, Sanjiu code, interleaved 25 code and EAN 128 code. UPC codes are mainly used in North America. EAN code is an international symbol system, a fixed-length meaningless bar code, which is mainly used to identify goods. EAN 128 code is a specific bar code symbol jointly developed by EAN International and American Uniform Code Committee. It is a continuous, non-fixed length and meaningful high-density code, which is used to express more commodity information such as production date, batch number, quantity, specification, shelf life and receiving place. Other coding systems are suitable for some specific occasions, such as Kudba code used for tracking management of blood banks, libraries and parcels. Code 250 is used for packaging, transportation and international aviation systems to sequentially code air tickets. There is also code 93 similar to code 39, which has higher density and can replace code 39.
These barcodes are unique barcodes. Due to the continuous expansion of the application field of bar code, higher requirements are put forward for the density and information content of a certain area. One-dimensional bar code is only the identification of items. If you want to know more information, you must rely on the database. In places where there is no database and it is not convenient to network, the use of one-dimensional bar code is greatly restricted, and sometimes it even becomes meaningless. In addition, it is almost impossible to express Chinese characters or image information with one-dimensional barcode. In order to better meet the demand, a new form of bar code-two-dimensional bar code came into being. Structurally speaking, two-dimensional bar codes are divided into two categories, one is composed of matrix codes and dot codes, and its data is encoded in the form of two-dimensional space; The other is composed of multiple lines of bar code symbols, and its data is displayed as a series of data lines. Overlapping symbols are CODE49, CODE 16K and PDF4 17. PDF is the abbreviation of portable data file, and 4 17 is related to width code, which is used to encode characters. Matrix codes, such as Maxicode, Data Matrix, Code One and Dot Code A, can be made very small, and can even be used as labels for silicon wafers, so they can be used for small objects.
Two-dimensional bar code has high density, large amount of information, good confidentiality and anti-counterfeiting performance, and can encode digital information such as photos, fingerprints, palm prints, retinas, sounds, signatures and characters. Therefore, two-dimensional barcode is the most ideal method to realize the automatic storage, carrying and reading of large-capacity and high-reliability information such as certificates, cards, documents, photos and bills.
A brief history of bar code technology development
Bar code first appeared in the 1940s, but it was not until the 1920s that it was really applied and developed rapidly. Bar code technology has been widely used in Europe, America, Japan and other countries, and has been rapidly popularized around the world, and its application fields are still expanding.
As early as the late 1940s, two American engineers, Joe Woodland, Benny and Silver, began to study the use of codes to represent food items and the corresponding automatic identification equipment, and obtained an American patent at 1949. This code pattern is very similar to a miniature archery target and is called "bull's-eye" code. The concentric circles of the target are drawn by circles and blanks. In principle, it is very similar to the later bar code symbols, but the technology at that time has not reached the level of printing this code. However, 20 years later, Joe and Woodland, as engineers of IBM, became the founders of ——UPC code, a unified code in North America. Gillard, Faesser and others applied for a patent in 1959, in which every number from 0 to 9 is represented by seven parallel bars. But this encoder is difficult to read and inconvenient for people to read. Soon, E.F. No, Linker got a patent for marking bar codes on trams. In the late 1960s, Syl Vegna invented a bar code system, which was adopted by the North American railway system. These two inventions were the earliest applications of bar code technology.
1970, the ADHOC Committee of American supermarkets formulated the universal commodity code-UPC code, which was first tried out in the retail industry, laying the foundation for the unification of the coding system in the future. The following year, Blesi Company developed the "Blesi code" and the corresponding automatic identification system, which was applied to inventory management for the first time. 1972, Monaque, Ma Jin and others developed exit bar codes, and American bar code technology entered a new stage. 1973, the United States Uniform Coding Committee established UPC barcode system, which fully standardized the coding system. 1974, Dr. David and Dr. Ariel of Internet company introduced code 39, which was adopted by the US Department of Defense. Code 39 was later widely used in industrial fields.
1977, the European * * * code was formulated on the basis of UPC- 12 code, and the European Article Coding Association was established. By 198 1 year, EAN had developed into an international organization called "ean international" for short. Japan began to establish POS system from 1974, and made Japanese commodity code JAN code from 1978. 10 years later, Japan became the largest user of EAN organization.
In 1980s, people did a lot of research to improve the information density of bar codes. Information density is an important parameter to describe bar code symbols. Usually, the number of letters that can be written per unit length is called information density, which is recorded as letters /CM. Code 128 and code 93 are successful attempts to improve the density. Later, David and Ariel developed to 49 yards. Germany and Williams introduced 16K code in 1988, which is a relatively new code system and suitable for laser systems. At the same time, automatic identification equipment and printing equipment have also made great progress.
The rapid development of bar code technology and its application in many fields have attracted the attention of many countries. The European Article Coding Association (ean) was formally established on 1976. By 198 1, EAN has developed into an international organization, so it is also called ean international. However, due to historical reasons and habits, the organization is still called EAN. Today, EAN members have spread over more than 80 countries and regions on six continents. By the end of 1996, more than 4 1 1000 companies in the world have become members of EAN organizations. Together with 176000 companies in the United States Uniform Coding Committee (UCC) system, more than 587000 companies around the world use bar codes, and have benefited greatly from modern information technology in business and trade. There are thousands of manufacturers engaged in the research, development, production and operation of bar code technology and related products in various countries, with nearly 10,000 kinds of products, which has become a high-tech industry of considerable scale.
There are many kinds of bar code reading equipment, which can be roughly divided into online readers and portable readers. According to their functions and uses, online readers can be divided into multifunctional readers and special readers. This kind of reader is generally powered by power supply and transmits data to the computer through cable connection. The invention not only has the function of identifying multiple codes, but also can add programmable function, displayable function and multi-computer networking communication function according to different needs. Portable readers are equipped with data storage, usually powered by batteries, and are suitable for offline work. After collecting data, first store the data, and then dump the host.
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