The knowledge of the barcode

Source: HF in time: the 2012-7-2 click: 2355] [double-click the rolling window

A, barcode overview

Barcode is by American N.T.W oodland first proposed in 1949. In recent years, with the continuous popularization of computer application, the application of bar code got great development. Barcodes can mark the commodity producer, manufacturer, name of commodity, production date, books classification number, E-mail start-stop information such as location, category, date, and in the circulation of commodities, library management, postal management, the banking system and many other fields has been widely used. Bar code is made up of different width, different reflectivity of bar and empty, according to certain encoding rules (yards) into, used to express a set of Numbers or letters symbol information graphic identifier. The bar code is a set of different degree, according to certain rules of parallel lines arrangement spacing graphics. Common barcode is by the reflectivity vary widely in the (article) black and white (empty).

Second, the composition of bar code recognition system

In order to read the bar codes to represent information, need a bar code identification system, enlarge it by barcode scanner, shaping circuit, decoding interface circuit and computer system components.

The principle of three identification bar code, bar code reader

Due to the different colors of objects, the reflection of the wavelength of visible light, white objects reflect all kinds of wavelength of visible light, black objects absorb various wavelengths of visible light, so when the barcode scanner light source the light after aperture and lens 1, exposure to black and white on the bar code, the reflected light after convex lens 2 focus, exposure to the barcode scanner photoelectric converter, so the photoelectric converter receives and the strength of the white and black stripes corresponding different reflected light signal, translates into corresponding electrical signal output to the barcode scanner amplifier shaping circuit. White, black strip width is different, have different length of the corresponding signal duration. However, the article by photoelectric converter output with the bar code and the corresponding electrical signals are generally only about 10 mv, cannot be used directly, thus to converter output signals will be sent to the amplifier amplification. The large electrical signal is still an analog signal, in order to avoid the error caused by a defect and the stain of bar code signal, add a shaping circuit after amplifying circuit and converts analog signals into digital signals, so that the computer system can accurate interpretation. The pulse shaping circuit digital signal by the translator translated into digital, character information. It is by identifying the starting, termination characters to distinguish out the code system and the scanning direction of the bar code symbol; By measuring the pulse digital signal 0, 1, to identify the number of bar and the number of empty. By measuring the 0, 1, the duration of the signal to the width of the discriminant and empty. So had been read the article of bar code symbol and the number of empty, and the corresponding width and the code system according to the code system of the coding rules, bar code scanner can swap bar symbol for the corresponding digital, character information, through the interface circuit for a computer system for data processing and management, complete the whole process of the bar code legible.