Two-dimensional bar code (2-dimensional bar code) is a specific geometric figure according to certain laws in the plane (two-dimensional direction) distribution of black and white graphic record data symbols of information; in the preparation of the code clever use of the internal logic of the computer constitutes the basis of the "0", "1" bit stream concept, the use of a number of geometric shapes corresponding to the binary to indicate the text numerical information, through the image input device or photoelectric scanning equipment to realize the automatic processing of information: it has some of the bar code technology **** sex: each code system has its own specific set of characters; each character occupies a certain width; It has some checksum functions, etc. It also has the ability to check different lines of information. At the same time also has a different line of information on the automatic identification function, and to deal with the characteristics of the graphic rotation changes.
Origin of the barcode
Barcode technology since the early 1970s, the rapid development of only 20 years, it 2D barcode
has been widely used in the commercial circulation, warehousing, health care, library and intelligence, postal services, railroads, transportation, production automation management and other fields. The application of barcode technology greatly improves the speed of data collection and information processing, improves people's working and living environment, improves work efficiency, and makes an important contribution to the scientific and modernization of management. Two-dimensional barcode technology is produced under the premise that one-dimensional barcode cannot meet the demand of practical application. Due to the limitation of information capacity, one-dimensional barcode is usually the identification of the item rather than the description of the item. The so-called identification of the item is to assign a code to an item, the code is marked on the item in the form of a barcode, which is used to identify the item so that it can be read by the automatic scanning equipment, and the code or the 1D barcode itself does not represent the descriptive information of the product. Therefore, in the application system of universal commodity bar code, the description of commodity information, such as production date, price, etc. must rely on the support of the database. In places where there is no pre-established commodity database or inconvenient networking, it is almost impossible for 1D barcode to represent Chinese characters and image information, and even if it can be represented, it seems to be very inconvenient and inefficient. With the development of modern high-tech, there is an urgent need to use barcodes to represent more information in a limited geometric space to meet the needs of ever-changing information representation.
Edit this paragraph barcode classification
The two-dimensional barcode can be divided into stacked/row-row two-dimensional barcode and matrix two-dimensional barcode. Stacked/rowed 2D barcodes are formally stacked by multiple rows of truncated 1D barcodes; matrix 2D barcodes are composed in the form of a matrix, in which the corresponding element positions are represented by "dots" as binary "1" and "blanks" as binary "1", and "blanks" as "blanks". "Empty" means binary "0", by the "point" and "empty" arrangement of the code.
Stacked/rowed 2D barcode
Rowed 2D barcode
Two-dimensional barcode (also known as: stacked 2D barcode or layer-rowed 2D barcode), whose coding principle is based on one-dimensional barcode, is stacked into two rows or more rows according to the need. It inherits some features of 1D barcode in terms of coding design, checking principle, reading method, etc. The reading equipment and barcode printing are compatible with 1D barcode technology. However, due to the increase in the number of rows, it is necessary to determine the rows, and its decoding algorithm and software are not exactly the same as that of 1D barcode. Representative rows of two-dimensional bar code CODE49, CODE 16K, PDF417 and so on. CODE49, which was developed by Dr. David Allair in 1987, Intermec launched the first two-dimensional bar code. Code 49 bar code Code 49 is a multi-layer, continuous, variable-length bar code symbology, which can represent all 128 ASCII characters. Each Code 49 barcode symbol consists of 2 to 8 layers, with 18 bars and 17 blanks per layer. The layers are separated from each other by a layer separator bar. Each layer contains a layer identifier and the last layer contains information indicating the number of layers in the symbol. Code 16K Barcode In 1988 Ted Williams of Laserlight Systems, Inc. introduced the second 2D barcode, Code 16K. The Code 16K barcode is a multi-layer, continuous variable-length barcode symbology that can represent the full ASCII character set of 128 characters as well as extended ASCII characters. It uses UPC and Code128 characters. A 16-layer Code 16K symbology can represent 77 ASCII characters or 154 numeric characters. 16K identifies the layer with a unique start/stop character, and error checking is provided by character self-checking and two modulo 107 check characters.
Matrix 2D codes
Short-array 2D barcodes (also known as checkerboard 2D barcodes) are encoded in a rectangular space with different distributions of black and white pixels in a matrix. In the corresponding element position of the matrix, the appearance of the point (square point, round point or other shapes) indicates the binary "1", the point does not appear to indicate the binary "0", the point of the arrangement of the combination of the matrix to determine the meaning of the two-dimensional bar code represents. Matrix two-dimensional bar code is built on the basis of computer image processing technology, the principle of combinatorial coding, a new type of graphic symbols automatically read and process the code system. The representative matrix two-dimensional bar code has: Code One, Maxi Code, QR Code, Data Matrix and so on. In the dozens of two-dimensional code, commonly used code system: PDF417 two-dimensional bar code, Datamatrix two-dimensional bar code, Maxicode two-dimensional bar code, QR Code, Code 49, Code 16K, Code one, etc. In addition to these common two-dimensional bar code, there are also Vericode bar code, CP bar code, Codablock F barcode, Field Code, Ultracode barcode, Aztec barcode, in addition to these common 2D barcodes.
Editorial reading equipment
A. 2D barcode reading equipment can be divided into different reading principles: (1) Linear CCD and Linear Image Reader (Linear Imager) can read one-dimensional barcodes and linear stacked two-dimensional barcode (such as PDF417), the two-dimensional barcode reading needs to be swept vertically along the barcode over the entire barcode, we call the We call it "sweeping reading". These products are cheaper. (2) Laser reader with grating Can read 1D barcode and linear stacked 2D code. Read two-dimensional code when the light will be aimed at the bar code, the grating element to complete the vertical scanning, do not need to be manually swept. (3) Image Reader (Image Reader) The barcode image is taken by surface array CCD camera and then analyzed and decoded, which can read 1D barcode and all types of 2D barcode. B. 2D barcode reading equipment can be divided into: handheld, fixed according to the different ways of work. Handheld: that is, two-dimensional code scanner. Can scan PDF417, QR code, DM code two-dimensional bar code scanner, such as Symbol's DS6707.DS6708 and so on. Fixed: that is, QR code reader, desktop, non-handheld, on the table or fixed in the terminal equipment, such as SUMLUNG's SL-QC15S and so on. The QR code printed on the paper and the QR code on the cell phone screen can be recognized, so it is widely used in the field of e-ticketing, e-coupon, membership system, cell phone QR code boarding and so on.