Barcode scanner principle
When it comes to bar code estimation, many people are not very familiar with it, but two-dimensional codes are well known. In fact, bar codes are also very common in life, but we usually pay less attention to them. Barcodes first appeared in the 1950s, and gradually developed into a complete item identification system. They are widely used in the fields of commerce, postal service, library management and warehousing.
A bar code is a pattern consisting of black and white stripes. The black part is called "bar" white and is called "empty". Bars and spaces are used to represent 0 or 1, respectively, so that the combination of different thickness stripes represents different encoding information. Because the barcode uses only the horizontal direction to store information, it can also be called a "one-dimensional code." The two-dimensional code with a larger storage capacity was also developed on this basis.
In the process of bar code application, special instruments are needed to identify it, the so-called scanner gun. Since the reflectance of the same light in the bar code and the space pair is very different, the respective reflected light intensity is also significantly different. Bar code scanners use this principle to identify the barcodes by detecting different reflected light from different emission areas using an optical sensor. The main principle process is as follows:
As shown in the figure, the light emitted by the light source in the bar code scanner is reflected by the lens 1 after being irradiated to the bar code. The reflected light is converged on the optical sensor through the lens 2 so as to convert the light of different intensities into electric signals, and the duration of different electric signals represents the width of the bar and the space. Then, the electrical signal will be amplified, processed, and sent to the decoding circuit to "translate" the original encoded information. Finally, by collating with the coded information in the computer system, the information about the bar code is obtained.
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) Barcode was first proposed by NTWoodland 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. A wide range of applications.
Second, 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.
Bar code is one of the most economical and practical automatic identification technologies so far. It not only has fast input speed, but also has high reliability. The bit error rate is lower than one millionth. In addition, its production is also very simple, there are no special requirements for equipment and materials, equipment and production costs are low. Especially in the retail sector, barcode identification is very popular.
The bar code is from the United States. T. Woodland first presented in 1949. In recent years, with the continuous popularization of computer applications, the application of barcode has been greatly developed. The bar code can indicate the country of manufacture, manufacturer, product name, date of manufacture, book classification number, mail start and end location, type, date, etc. of the product, and is therefore available in many areas such as commodity distribution, library management, postal and telecommunications management, and banking systems. A wide range of applications.
China established the China Article Numbering Association in 1988 and officially joined the EAN organization in April 1991. At present, the prefix code used by China's merchandise is 690,691,692,693 which EAN International Organization assigned to our country.
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