bar code was first put forward by N.T.Woodland in the United States in 1949. in recent years, with the continuous popularization of computer application, the application of bar code has been greatly developed. bar code can indicate the country of production, manufacturer, product name, production date, book classification number, starting and ending place of mail, category, date and other information. Therefore, it has been widely used in many fields, such as commodity circulation, book management, post and telecommunications management, banking system, etc.
Barcodes are graphic identifiers which are composed of bars and spaces with different widths and different reflectivity and are compiled according to certain coding rules (coding system) to express a group of numbers or letter symbols. Arranging parallel line patterns at intervals according to certain rules. Common bar codes are composed of black bars (abbreviated as bars) and white bars (abbreviated as spaces) with great differences in reflectivity.
II. Composition of bar code recognition system
In order to read the information represented by bar codes, a bar code recognition system is needed, which consists of bar code scanner, amplification and shaping circuit, decoding interface circuit and computer system.
III. Recognition principle of bar code
Because objects of different colors have different wavelengths of reflected visible light, white objects can reflect visible light of various wavelengths, while black objects absorb visible light of various wavelengths, when the light emitted by the light source of the bar code scanner passes through the diaphragm and the convex lens 1 and irradiates the black-and-white bar code, the reflected light is focused by the convex lens 2 and irradiated on the photoelectric converter. Therefore, the photoelectric converter receives reflected light signals with different intensities corresponding to the white bars and black bars, and converts them into corresponding electrical signals to be output to the amplification and shaping circuit. The widths of the white bars and black bars are different, and the duration of the corresponding electrical signals is also different. However, the electrical signals corresponding to the bars and spaces of the bar code output by the photoelectric converter are generally only about 1 mV, which cannot be directly used. Therefore, the electrical signal output by the photoelectric converter should be sent to the amplifier for amplification. The amplified electrical signal is still an analog electrical signal. In order to avoid the error signal caused by the defects and stains in the bar code, a shaping circuit should be added after the amplification circuit to convert the analog signal into a digital electrical signal so that the computer system can accurately interpret it.
The pulse digital signal of the shaping circuit is translated into digital and character information by the decoder. It can distinguish the coding system and scanning direction of bar code symbols by identifying the starting and ending characters. The number of bars and spaces can be determined by measuring the number of pulse digital electric signals and 1, and the width of bars and spaces can be determined by measuring the duration of signals and 1. In this way, the number of bars and spaces, the corresponding width and the used code system of bar code symbols can be obtained. According to the coding rules corresponding to the code system, bar symbols can be changed into corresponding digital and character information, which can be sent to the computer system through the interface circuit for data processing and management, thus completing the whole process of bar code identification and reading.
the code represented by the standard version of commodity bar code consists of 13 digits, and its structure is as follows:
Structure 1: x13x1x1 x9x8x7x5x3x2x1
where: x13 ... x7 manufacturer identification code; X6 ... x2 represents the commodity item code; X1 check code.
structure 2: x13x11x1 x9x87x6 x5x3x2x1
where: x13 ... X6 manufacturer identification code; X5 ... x2 represents the commodity item code; X1 check code.
when x13x12x11 is 69 and 691, its code structure is the same as Structure 1; When x13x12x11 is 692, its code structure is the same as structure 2.
check code calculation
refer to the method specified in the national standard of gb 1294 "General Commodity Barcode".
the shortened version of the barcode consists of 8 digits, and its structure is as follows:
x8x7x5x3x2x1
where: x8x7 X6: its meaning is the same as that of the standard version of the barcode; X5x4x3x2: indicates the commodity item code,
which is uniformly distributed by ean coding organization. In China, it is uniformly distributed by China Article Coding Center; X1: check code. When calculating,
you need to add five zeros before the shortened version of the barcode code, and then calculate according to the calculation method of the standard version of the barcode check code. Country (or region) of prefix code organization/application field Country (or region) of prefix code organization/application field
~ 19; 3 ~ 39; 6 ~ 139 USA
2 ~ 29; 4 ~ 49; 2 ~ 299 store code
5 ~ 59 coupon
3 ~ 379 France
38 Bulgaria
383 Slovenia
385 Croatia
387 Bosnia and Herzegovina
4 ~ 44 Germany
45 ~ 459; 49 ~ 499 Japan
46 ~ 469 Russia
47 Kyrgyzstan
471 China Taiwan Province
474 Estonia
475 Latvia
476 Azerbaijan
477 Lithuania
478 Uzbekistan
479 Sri Lanka
48. > 481 Belarus
482 Ukraine
484 Moldova
485 Armenia
486 Georgia
487 Kazakhstan
489 China Hong Kong Special Administrative Region
5 ~ 59 Britain
52 Greece
528 Lebanon
529 Cyprus < 53 Albania
531 Macedonia
535 Malta
539 Ireland
54 ~ 549 Belgium and Luxembourg
56 Portugal
569 Iceland
57 ~ 579 Denmark
59 Poland
594 Romania
594. p> 6、 61 South Africa
63 Ghana
68 Bahrain
69 Mauritius
611 Morocco
613 Algeria
616 Kenya
618 Ivory Coast
619 Tunisia
621 Syria
622 Egypt
624 Libya. 625 Jordan
626 Iran
627 Kuwait
628 Saudi Arabia
629 United Arab Emirates
64 ~ 649 Finland
69 ~ 695 Chinese people * * * And
7 ~ 79 Norway
729 Israel
73 ~ 739 Sweden
74 Guatemala
741 El Salvador
742 Honduras
743 Nicaragua
744 Costa Rica
745 Panama
746 Dominica < 75 Mexico
754 ~ 755 Canada
759 Venezuela
76 ~ 769 Switzerland
77 Colombia
773 Uruguay
775 Peru
777 Bolivia
779 Argentina
78 Chile
784 Paraguay. Er
789 ~ 79 Brazil
8 ~ 839 Italy
84 ~ 849 Spain
85 Cuba
858 Slovakia
859 Czech Republic
86 Yugoslavia
865 Mongolia
867 Korea
867. Netherlands
88 Korea
884 Cambodia
885 Thailand
888 Singapore
89 India
893 Vietnam
899 Indonesia
9 ~ 919 Austria
93 ~ 939 Australia
94 ~ 939. Laixi
958 China Macao Special Administrative Region
977 serial publications
978, 979 books
98 notes receivable
981, 982 general circulation coupons
99 ~ 999 coupons.