A bar code is a mark composed of a set of regularly arranged bars, spaces, and corresponding characters. "Bar" refers to the portion with low reflectivity to light, and "Void" refers to the portion with high reflectivity to light. These bars and space are composed of The data expresses certain information, and can be read with specific equipment and converted into binary and decimal information compatible with the computer. One-dimensional barcodes only express information in one direction (generally horizontal), but do not express any information in the vertical direction. The certain height is usually for the convenience of reader alignment. Barcodes that store information in two-dimensional spaces in the horizontal and vertical directions are called 2-dimensional barcodes. Two-dimensional bar codes can express information in both horizontal and vertical directions, so they can express a large amount of information in a small area.
The two-dimensional bar code uses a certain geometric figure to record the data symbol information in a black and white pattern distributed on a plane (in the two-dimensional direction) according to a certain rule; in the code compilation, the "0" which constitutes the internal logical basis of the computer is cleverly used 1. The concept of "1" bit stream, which uses several geometric shapes corresponding to binary to represent text and numerical information, and is automatically read by image input equipment or photoelectric scanning equipment to realize automatic information processing: it has some common characteristics of barcode technology : Each code system has its specific character set; each character occupies a certain width; has a certain check function, etc. At the same time, it also has the characteristics of automatic recognition of different lines of information, and processing graphics rotation changes.
One-dimensional bar codes are usually the identification of items, not the description of items. That is, the bar code is just the code of the item, which is used to facilitate the scanning of the item. The bar code does not contain the description information of the product, and the background database is needed to support the scan. The one-dimensional bar code is trapped in the limitation of its own information amount, such as the small amount of data? It can only contain letters and numbers; the bar code size is relatively large; after the bar code is damaged, it cannot be read. With the development of modern high-tech, there is an urgent need to use bar codes to represent more information in a limited geometric space to meet the needs of ever-changing information representation. In this way, two-dimensional bar code came into being.
Two-dimensional barcodes have unmatched advantages over one-dimensional barcodes. Compared with one-dimensional barcodes:
1. The two-dimensional barcode has large information capacity, high information density, and strong coding ability. It can encode small data files including photos, text, fingerprints, palm prints, sounds, and signatures, representing a large amount of information in a limited area;
2. The two-dimensional barcode can accurately describe the "item". The system gives the item a unique anti-counterfeiting code and marks it on the product or packaging. The product can be copied by the counterfeit but the code is unique, which is convenient to realize in places away from the database and inconvenient to connect data collection;
3. The two-dimensional barcode is easy to print, the cost is very low, the error correction ability is strong, the decoding reliability is high, and it has a strong anti-counterfeiting ability. It is precisely because the two-dimensional barcode can realize the two important functions of machine reading and anti-counterfeiting, so it is widely used in various ID card systems such as ID cards, driver's licenses, passports, and visas.
The new version of train ticket upgrade anti-counterfeiting can effectively suppress the use of fake tickets. It can be said that those who manufacture and sell fake tickets still have a long way to go to break through this technology. It takes time to prove.
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