Bar code was first proposed by N.T.Woodland of the United States in 1949. In recent years, with the popularization of computer application, the application of bar code has been greatly developed. Barcode can indicate the country of production, manufacturer, product name, date of production, book classification number, mailing place, category, date and other information. Therefore, it is widely used in many fields, such as commodity circulation, book management, post and telecommunications management, banking system and so on. Bar code is a graphic identifier composed of bars and spaces with different widths and reflectivity, which is compiled according to certain coding rules (coding system) to represent a group of numerical or alphabetic symbol information. That is, bar code is a group of parallel lines with different thicknesses and arranged at regular intervals. Common bar codes are composed of black bars (abbreviated as bars) with different reflectivity.
Second, the composition of the bar code identification system
In order to read the information represented by bar code, a bar code recognition system is needed, which consists of bar code scanner, amplification and shaping circuit, decoding interface circuit and computer system.
Third, the principle of bar code scanner to identify bar codes
Because different colors reflect different wavelengths of visible light, white objects can reflect various wavelengths of visible light, while black objects absorb various wavelengths of visible light. Therefore, when the light emitted by the light source of the barcode scanner is irradiated onto the black and white barcode through the diaphragm and the convex lens 1, the reflected light is focused by the convex lens 2 and then irradiated onto the photoelectric converter in the barcode scanner. Therefore, the photoelectric converter receives reflected light signals with different intensities corresponding to white bars and black bars, converts them into corresponding electrical signals and outputs them to the amplification and shaping circuit of the bar code scanner. The widths of white bars and black bars are different, and the duration of corresponding electrical signals is also different. However, the electrical signal output by photoelectric converter corresponding to the bar and space of bar code is generally only about 10mV, so it cannot be used directly. Therefore, the electrical signal output by the photoelectric converter should be sent to the amplifier for amplification. The amplified electrical signal is still analog. In order to avoid false signals caused by defects and stains in bar codes, a shaping circuit should be added after the amplification circuit to convert analog signals into digital electrical signals so that the computer system can accurately interpret it. The pulse digital signal of the shaping circuit is converted into digital and character information by the decoder. It can identify the coding system and scanning direction of bar code symbols by identifying the start and end characters. By measuring the number of pulse digital electric signal 0, 1, the number of bars and spaces can be determined, and by measuring the duration of signal 0, 1, the width of bars and spaces can be determined. In this way, the number of bars and spaces used for bar code symbols and the corresponding width and code system can be obtained. According to the coding rules corresponding to the coding system, barcode scanner converts the bar code symbols into corresponding digital and literal information, and sends them to the computer system for data processing through the interface circuit.
More details
The application of barcode has the following advantages:
1. Reliable and accurate. It can be concluded that keyboard input has an error every 300 characters on average, while barcode input has an error every 15000 characters on average. If you add check, the error rate is one in ten million.
2. Fast data entry. Keyboard input, a typist who types 90 words per minute can input 12 characters or strings in 1.6 seconds, while using bar code, the same work takes only 0.3 seconds, which is five times faster.
3. The economy is cheap. Compared with other automatic identification technologies, the popularization and application of bar code technology takes a long time and costs less.
4. Flexible and practical. As a means of identification, bar code symbols can be used alone, or can be combined with related equipment to form an identification system to realize automatic identification, and can also be linked with other control equipment to realize automatic management of the whole system. At the same time, when there is no automatic identification device, manual keyboard input can be realized.
5. Great freedom. The degree of freedom of the relative position between the identification device and the barcode label is much greater than OCR. Barcodes usually only express information in one dimension, but the information on the same bar code is exactly the same and continuous, so that even if the label part is defective, the correct information can still be input from the normal part.
6. The equipment is simple. Bar code symbol recognition equipment is simple in structure, easy to operate and does not need special training.
7. Easy to make. Printable, called "printable computer language". Bar code labels are simple to make and have no special requirements on printing technology, equipment and materials. Commodity barcode knowledge
Commodity barcode refers to a symbol composed of a group of regularly arranged bars, spaces and their corresponding characters, which is used to represent certain commodity information. Among them, the bar is dark and empty, which is a reading device used to scan and read bar codes. Its corresponding characters consist of a group of Arabic numerals for people to read directly or input data to the computer through the keyboard. This set of spaces and corresponding characters represent the same information.
Bar code technology was born with the development and application of computer and information technology. It is a new technology integrating coding, printing, identification, data acquisition and processing.
Using bar code scanning is the general trend of future market circulation. In order to make goods circulate freely and widely in the world, enterprises must abide by the relevant provisions of commodity bar codes whether designing, manufacturing, applying for registration or using commodity bar codes.
At present, ena barcode, upc barcode, 25 barcode, Cross barcode, Kudba barcode, Sanjiu barcode and 128 barcode are commonly used in the world, among which ean barcode is the most commonly used commodity.
Ean commodity bar code, also known as general commodity bar code, is formulated by ean international and is widely used in the world. It is the most widely used commodity bar code in the world. At present, this commodity bar code is being used in China. Ean commodity bar codes are divided into EAN- 13 (standard version) and EAN-8 (abbreviated version).
EAN- 13 general commodity bar code generally consists of prefix, manufacturer code, commodity code and check code. The prefix code in commodity bar code is used to identify the country or region, and the code is given in ean international. For example, 00-09 stands for the United States and Canada. 45-49 stands for Japan. 690-692 stands for Chinese mainland, 47 1 stands for Taiwan Province Province and 489 stands for Hong Kong Special Administrative Region. The empowerment of manufacturers' codes is organized by article codes in various countries or regions, while in China, the National Article Coding Center gives manufacturers' codes. Commodity codes are codes used to identify commodities, and the right to assign codes is exercised by the product manufacturers themselves. Manufacturers themselves decide which Arabic numerals to use for their products according to the prescribed conditions. At last, the 1 parity code is used to check the correctness of the L- 12 digital code from the left in the barcode.
The coding of commodity bar codes follows the principle of uniqueness, so as to ensure that commodity bar codes will not be repeated in the global scope, that is, a commodity item can only have one code, or a code can only identify one commodity item. Commodities with different specifications, different packages, different varieties, different prices and different colors can only use different commodity codes.
The standard size of commodity bar code is 37.29mmx26.26mm, and the magnification is 0.8-2.0. When the printing area allows, the barcode with magnification of 1.0 should be selected to meet the reading requirements. The smaller the magnification, the higher the printing accuracy. When the printing accuracy can not meet the requirements, it is easy to read the bar code.
Because the identification of bar code is realized by the color contrast between bar code and blank bar code, generally speaking, as long as the color can meet the requirements of contrast (pcs value), light color can be used as blank color, such as white, orange and yellow, and dark color as bar, such as black, dark green and dark brown. The best color scheme is black stripes and white spaces. According to the practical experience of bar code detection, red, gold and light yellow should not be used as bar code colors, and transparent and gold should not be used as blank colors.
EAN-8 commodity bar code refers to the 8-digit commodity bar code used for identification, which consists of 7-digit commodity item code and 1 digit check code.
The birth of commodity bar code greatly facilitates the circulation of commodities, and modern society cannot do without commodity bar code. According to statistics, at present, there are 500,000 kinds of products in China that use the international commodity bar code. After China's entry into the WTO, enterprises will surely win more space for activities on the international stage. To keep up with international practice and meet the needs of international trade, enterprises should not mistreat commodity bar codes.
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