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Barcode scanner Identification principle

Sourc:The SiteAddtime:2017/10/12 Click:0
Due to different color objects, the wavelength of visible light reflected is different, white objects can reflect visible light of various wavelengths, and black objects absorb visible light of various wavelengths, so when the light emitted by the light source of the barcode scanner passes through the diaphragm and the convex lens 1 When irradiating to a black and white bar code, the reflected light is focused by the convex lens 2 and then irradiated to the photoelectric converter. Thus, the photoelectric converter receives reflected light signals with different intensity corresponding to the white bars and the black bars, and converts them into corresponding light signals. The electrical signal is output to an amplification and shaping circuit, and the shaping circuit converts the analog signal into a digital electrical signal, which is then translated into digital character information via the decoding interface circuit.

The widths of the white and black stripes are different, and the duration of the corresponding electrical signal is different. However, the electrical signal output by the photoelectric converter and bar code and space corresponding to the general electrical signal is generally only about 10mV, can not be used directly, so the electrical signal output to the photoelectric converter should be amplified. The amplified electrical signal is still an analog electrical signal. To avoid false signals caused by defects and stains in the barcode, a shaping circuit needs to be added after the amplification circuit to convert the analog signal into a digital electrical signal so that the computer system can accurately interpret the signal. .
The pulsed digital signal of the shaping circuit is translated into digital and character information by the decoder. It identifies the starting and ending characters to determine the code system and the scanning direction of the bar code symbol; the number of bars and spaces is determined by measuring the number of pulse digital electrical signals 0 and 1. The widths of bars and spaces are determined by measuring the duration of the 0 and 1 signals. In this way, the bar code and the number of blanks and the corresponding width and code system used for the bar code symbol being deciphered are obtained. According to the encoding rules corresponding to the code system, the bar-shaped symbols can be replaced with corresponding numbers and character information. The interface circuit is sent to the computer system for data processing and management, and the entire process of barcode reading is completed.
The bar code is a graphic identifier of a set of numbers or alphabetic symbols, which is composed of bars and spaces with different widths, different reflectivity, and according to a certain coding rule (code system). That is, a bar code is a group of different thicknesses, and the parallel line patterns are arranged according to certain rules. The common bar code is composed of black bars (abbreviated bars) and white bars (abbreviated empty bars) whose reflectances differ greatly.
1. Barcode Overview - Barcode Recognition Principle (Barcode Recognition Principle) Barcodes were first proposed by N.T. Woodland of the United States in 1949. With the continuous popularization of computer applications, the application of barcode has been greatly developed. Barcodes can indicate the country of manufacture, manufacturer, name of goods, date of manufacture, classification number of books, start and end location of mail, category, date, etc., and thus are available in many areas such as commodity circulation, library management, postal and telecommunications management, and banking systems etc.
2, the composition of the bar code identification system - bar code identification principle (bar code identification principle) In order to read the bar code represented by the information, you need a bar code identification system, which consists of a bar code scanner, amplification and shaping circuit, decoding interface circuit and computer systems Partly composed.

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