What is a bar codeBar codes are arranged in groups according to certain rules, empty symbols coded symbol, used to indicate that a certain amount of characters, numbers, and symbols; the code points can be machine read.
bar code technology and other input techniques (such as keyboard input, the OCR input, magnetic card input, RF input), compared with fast speed, low error rate, cheap, low cost and the advantages of technology maturity, has been widely used in commercial, industrial, books, medical and other fields.
making use of barcode printing and printing, print bar-dedicated barcode printers or normal laser printers can be used. Read bar code device is handheld, card slot, platform, fixed type and many other commonly used laser or CCD. Bar code reading devices generally have built-in decoder output is represented by the bar code information. Bar code reading device with computer interface and RS232 interface using the keyboard in two, others are TTL interface and WAND emulation interface, USB interface, and so on.
two-dimensional bar code is developed in recent years a new type of barcode. One-dimensional bar codes because of the limited information content, limit its scope of application, two-dimensional bar code in addition to the one-dimensional bar code points, as well as informative, high reliability, confidentiality, strong security, and so on. The most commonly used two dimensional barcode PDF417 barcode.
bar code technology logistics tracking process as a key technology, are being more and more people understand and appreciate. Bar code technology is a low-cost automatic identification technology, an extremely broad field. The turn of the century, bar code scanners and speakers, steering wheel, traffic lights, mouse/graphic interface are experts as one of the 20th century's greatest 10 kinds of human-machine interface device! Principle
barcode recognition, barcode overview
bar code by United States N.T.Woodland proposed in 1949. In recent years, with the growing popularity of computer application, barcode application gets a great deal of development. Bar codes can be marked merchandise producer, manufacturer, product name, production date, classification number, the messages start and end locations, categories, dates and other information, thus in the circulation, library management, telecommunications management, banking systems, and have been widely applied in many fields.
bar code by width, different reflectivity and air, according to certain rules of coding (code) compiled, to express a set of numeric or alphanumeric symbols graphic identifier information. That bar code is a set of different thickness, according to certain rule spacing arrangement of parallel lines of graphics. Common bar code is a reflection of very different rates of black (abbreviation) and white (abbreviation) composition.
II, bar code recognition system for
in order to read bar codes represent information, need a bar code recognition system, which consists of bar code scanners, zoom shaping circuit, decoding circuit and system components (Figure 1).
three, and barcode of recognition principle
due to different color of objects, its reflection of visible of wavelength different, white objects can reflection various wavelength of visible, black objects is absorption various wavelength of visible, so dang barcode scan device light issued of light by light aperture and the convex lens 1 Hou, irradiation to black and white-and-of barcode Shang Shi, reflection light by convex lens 2 focused Hou, irradiation to photoelectric conversion device Shang, so photoelectric conversion device received to and white and black article corresponding of strength different of reflection light signal, And converted into electrical signals output to amplifier shaping circuit. Width of a white, black is different, the corresponding signal duration is also different. However, the opto-electrical Converter output with bar codes and corresponding signals in General only about 10mV, cannot be used directly, thus first opto-electrical Converter output signal to amplifier. Amplified signal is an analog electrical signal, in order to avoid defects and stains caused by the barcode error signal amplifier needs a plastic circuit, to convert analog signals into digital signals, so that the computer can accurately.
pulse shaping circuit digital signal decoder into numbers, character information. By identifying the starting and ending character to distinguish the barcode symbol codes and scanning direction through measuring pulse digital signal 0, 1 to determine the number of bars and the number of empty. By measuring the duration of 0, 1 signal to distinguish and empty width. This debate read barcode symbols were obtained and the number of empty and the corresponding width and use the code system, according to the coding system that rules would bar symbols with corresponding numbers, character information, through an interface circuit for computer systems for data processing and management, barcode reading process is completed.