1. Overview of barcode technology

1. Cheap and practical basic information technology

◆An automatic code produced and developed in the application practice of computers Recognition technology

◆ is designed to realize automatic scanning of information. It is an effective means to collect data quickly, accurately and reliably

◆The application of barcode technology solves the problem of data entry and data collection and "bottleneck", and provides strong technical support for supply chain management< /p>

◆Fast input speed

◆Large amount of information

◆High accuracy

◆Low cost

◆ Strong reliability

Barcode technology provides us with a way to identify and describe items in logistics. With the help of modern technical means such as automatic identification technology, POS systems, and EDI, companies can learn about relevant products at any time position in the supply chain and respond instantly.

2. Development of barcodes

Barcode technology, as an automatic data collection unit technology in logistics information systems, is an important technology for realizing automatic collection and input of logistics information. Barcodes first appeared in the 1940s, but they have only been put into practical use and developed rapidly in the past 20 years. There were reports on the use of barcodes on railway vehicles in the United States in the 1950s. Currently, all railway carriages in the United States have ACI (Automatic Car Identification) barcode marks. As early as the late 1940s, two American engineers, Joe Wood Land and Beny Silver, began to study the use of codes to represent food items and corresponding automatic identification equipment, and in 1949 Obtained a U.S. patent in 2006. This code pattern resembles a miniature archery target and is called a "bull's eye" code. The target's concentric rings and blanks are drawn. In principle, the "bull's eye" code is very similar to the later bar code symbol. Unfortunately, the commodity economy at that time was not very developed, and the technology did not reach the level of printing such a code. Twenty years later, Joe Woodland, as an engineer at IBM, became the founder of the UPC code, the unified code in North America. Girad Hissel and others applied for a patent in 1959 to represent each number in the numbers 0-9 with seven parallel strips, but this code was difficult for machines to read and could not be read. convenient. However, this idea promoted the emergence and development of barcode coding system. Soon, E. F. Brinker obtained a patent for bar codes on streetcars. In the late 1960s, Sylvania invented a barcoding system that was adopted by North American railroad systems.

3. The role of barcodes in logistics information systems

As a timely, accurate, reliable and economical data input method, barcodes have been adopted by logistics information systems. It has been widely used in industrially developed countries and has become a world-wide "ID card" unique to commodities.

Bar code technology has been widely used in Europe, the United States, Japan and other countries, and it is rapidly popularized around the world, and its application fields are still expanding. Due to the use of barcodes, consumers have a psychological sense of security about the quality of goods. Barcodes can also play an important role in identifying fake and inferior products and preventing counterfeiting. Because barcode technology has the characteristics of advanced, applicable, easy to master and quick results, it plays its advantages in information (data) collection. Whether in the process of warehousing, leaving warehouse, putting on shelves or settling with customers, we have to face how to collect data. The problem of inputting information into computers for large quantities of goods (whether packaged in whole packages or sold individually after being unpacked). If a barcode symbol is printed on the packaging of a single product, and a barcode reader is used, the product's variety (item number), quantity, unit price, manufacturer, date of manufacture and other information can be grasped quickly, accurately and in a timely manner. This not only improves efficiency, but also attracts more customers and reduces or eliminates crowded queues during checkout and payment after purchase. Barcode technology will serve as the main automatic identification technology in China, and will be widely used in industrial automation control and various management information systems, and will penetrate into many technical fields and high-tech products.

Bar code technology is used in logistics information systems to complete computer information collection and input. This will greatly improve the usefulness of many computer management systems. The application and promotion of barcodes first originated from the modernization of commodity management, that is, the application of POS systems. For example, there are more than 220,000 types of products in supermarkets in the United States. Every year, about 10,000 new products enter the market, and 10,000 old products are removed. The proportion of introducing new products and removing old products reaches 50%. With such a heavy workload, there is no Barcode, without POS system application is difficult to cope with. Today, Japan is at the forefront of the world in the application of POS systems. At present, there are 48,000 manufacturers in Japan with about 100 million product items using EAN code identification. A considerable number of merchants use POS systems. POS systems are not limited to groceries. Some professional stores (such as medicine, cosmetics, cigarettes, etc.) Liquor, etc.) also established a POS system.

At present, not only POS systems are widely used, many countries have also established market data exchange centers to communicate information between production, supply and sales, and establish trade data exchange institutions to collect and summarize sales information of various stores and various commodities in a timely manner and provide timely feedback. To the manufacturer. In this way, manufacturers can timely and accurately understand product sales, purchasing conditions, prices, etc., analyze consumer psychology, predict the market, and organize supply of goods in a timely manner. Retailers can promptly adjust sales plans, purchase status, etc. according to the situation.

1) Transportation industry

The International Transport Association has stipulated that during the transportation of goods, barcode symbols must be affixed to the packaging of items to facilitate automated statistical management of transported items. In addition, the role of barcodes as a timely, accurate, reliable and economical data input method has been used in automated ticket sales and inspection systems for railways and highways, automation of highway ticket collection stations, and logistics information systems in freight warehouses and cargo shuttles. Used in logistics information systems. It has been widely used in industrialized countries and has become a world-wide "ID card" unique to commodities. Countries such as Europe, the United States, Japan, etc. have widely used bar code technology, and rapid automated management around the world requires the use of bar code technology to collect data in real time.

2) Postal and telecommunications industry

The sorting and ordering of mails are very arduous tasks, taking up most of the workload of postal and telecommunications employees. By affixing or printing barcode symbols on mail, you can use barcode reading equipment to input corresponding information and implement automated management of sorting and ordering. For example, if the 6-digit postal code is replaced with a barcode symbol, a computer can be used to affix the corresponding barcode label to each postal and telecommunications office (station) as their code, and a barcode reading device can be used to read the information. The computer can be used to Realize the automatic ordering of registered mail.

3) Logistics industry

The logistics industry is a very important application aspect of barcode technology. Barcode management can be fully realized in terms of material warehousing, classification, outgoing warehouse, inventory and transportation. In terms of general commodity circulation and sales, in addition to doing a good job in automated bar code management of export commodities, we should start to develop special cash registers and shopping mall comprehensive management systems suitable for China's conditions, and gradually promote them through trials in high-end shopping malls. The POS system consists of several subsystems. The cash register (also called a cash register) is a combination of a personal computer and a decoder. It can automatically recognize bar symbols, perform data processing, and print out shopping lists. , the content includes product name, price, quantity, total amount and date, etc. Customers can use it as a shopping receipt. The computer in the system is used for comprehensive processing of data, for which a database and application software should be established in advance. This is conducive to conducting a comprehensive analysis of product sales based on the daily report status of each terminal, providing timely market dynamics, and determining ordering plans based on this to ensure the normal conduct of business activities. Due to the use of barcode technology, it is not only convenient and fast, but also ensures accurate information.

4) Retail industry

Supermarket: barcode - scanner - POS - EIQ analysis (category, quantity, quality)
Wal - Mart: barcode - Scanner (fixed, mobile) - POS - EIO analysis (category, quantity, quality)

5) Other industries

Practice shows that stores adopt a barcode system management system The direct benefits can reach 6.12% of turnover. More importantly, it not only promotes commodity circulation management, but also for manufacturers, the use of barcode technology can not only effectively control the quantity of components, parts, and semi-finished products in each process on the production line, as well as the inventory status of finished products and raw materials. Moreover, it is also possible to quickly obtain sales information through computer networks, predict market trends in a timely and effective manner, and establish an efficient operating mechanism that integrates production, supply, and sales. Because modern industrial and commercial trade is extremely active and the types of goods are numerous and complex, item coding can be used to This enables exporters to avoid errors in trade and understand the distribution of goods in a timely manner. The adoption of POS systems in the retail industry not only improves the speed of settlement, but also avoids human errors, thus greatly increasing the number of customers. For customers, the waiting time for shopping can be greatly reduced, and having a shopping list facilitates family accounting. The application of barcode management systems also creates favorable conditions for shopping mall service staff to provide customer consultation services.

Barcode technology can also be used in the customs for commodity declaration management and customs commodity inspection; in the public security system, it can be used for entry and exit visa management and passport, ID card, management, etc.; it can be used in personnel files in enterprises and institutions Management, equipment management, conference management, attendance management, college entrance examination self-study examination management and various tickets and bill management, etc. Barcode technology provides an extremely simple and consistent language for commodity management, trade between countries, and automated management in various fields.

As a new information storage and transmission technology, the two-dimensional barcode DF417 has been widely used in national defense, public security, transportation, medical care, industry, commerce, finance, customs and Government management and other fields. Driver's licenses, U.S. military IDs, and military medical IDs in more than a dozen states, including Arizona, have adopted PDF417 technology a few years ago. Encoding the personal information and photos on the ID into the 2D barcode not only enables automatic reading of ID documents, but also effectively prevents counterfeit IDs.

Many countries such as the Philippines, Egypt, and Bahrain have also adopted 2D barcodes on ID cards or driver's licenses. According to incomplete statistics, more than 40 countries have adopted the 2D barcode PDF417 on ID cards or driver's licenses. China has After the Hong Kong region resumed the exercise of sovereignty, the two-dimensional barcode PDF417 technology was used in the newly issued SAR passports for Hong Kong residents. In addition to documents, 2D barcodes are also widely used in industrial production, national defense, finance, medicine and health, commerce, transportation and other fields. Because the two-dimensional barcode has the advantages of low cost, information can move with the carrier, does not rely on databases and computer networks, and has strong confidentiality and anti-counterfeiting properties, combined with China's large population, thin base, and difficulty in investing in computer network funds, the authenticity of documents is Machine readability and anti-counterfeiting issues, so it can be widely used in passports, ID cards, driver's licenses, temporary residence permits, driving licenses, military IDs, health certificates, insurance cards and other documents that need to uniquely identify a person's identity. For any form that requires repeated entry or prohibits forgery or deletion, such as customs declarations, tax reports, insurance registration forms, etc., the information filled in the form can be encoded in PDF417 barcodes to solve the problem of automatic entry of the form and prevent tampering with the contents of the form. The production and assembly lines of mechanical and electrical products, such as automobile assembly lines and electronic product assembly lines, can all use 2D barcodes and realize automatic exchange of data through 2D barcodes. In the transportation and mailing of luggage, goods, and postal services, 2D barcodes have broad application prospects in China.

2. Barcode classification

1. Classification by coding system

1) UPC code

In 1973, the United States took the lead in domestic After UPC codes were used in commercial systems, Canada also adopted UPC codes in commercial systems. The UPC code is a continuous digital code system with a fixed length, and its character set is the numbers 0~9. It takes four element widths, with each bar or space being 1, 2, 3 or 4 times the unit element width. There are two types of IPC codes, namely UPC-A code and UPC-E code.

2) EAN code

In 1977, the European Economic Community countries formulated the European Article Code EAN code in accordance with the UPC code standard, which is compatible with the UPC code, and both have Same symbology. The character numbering structure of the EAN code is the same as the UPC code. It is also a fixed-length, continuous digital coding system. Its character set is the numbers 0~9. It takes four element widths, with each bar or space being 1, 2, 3 or 4 times the unit element width. There are two types of EAN codes, namely EAN-13 codes and EAN-8 codes.

3) Interleaved 25 code

Interleaved 25 code is a continuous self-checking digital code system with variable length, and its character set is the numbers 0~9. Taking two element widths, each bar and space is a wide or narrow element. The number of encoding characters is an even number, all data at odd-numbered positions are encoded as stripes, and data at even-numbered positions are encoded as nulls. If encoding an odd number of data, add a 0 in front of the data to make the data an even number of digits.

4) Code 39

Code 39 is the first alphanumeric code system. Launched by Intermec in 1974. It is a discrete self-adjustable alphanumeric code system of comparable length. Its character set is numbers 0-9, 26 uppercase letters and 7 special characters (-, ., Space, /, %, ￥), maximum 43 characters. Each character consists of 9 elements, including 5 bars (2 wide bars, 3 narrow bars) and 4 spaces (1 wide space, 3 narrow spaces). It is a discrete code.

5) Code Bar

Code Bar appeared in 1972. It is a continuous self-checking digital code system with variable length. Its character set is numbers 0-9 and 6 special characters (-, :, /, ., +, ￥), up to 16 characters. Commonly used in warehouses, blood banks and air express packages.

6) 128 code

The 128 code appeared in 1981. It is a continuous self-checking digital code system with variable length. It uses four element widths, each character consists of 3 bars and 3 spaces, with a maximum of 11 unit element widths, also known as (11, 3) code. It consists of 106 different barcode characters. Each barcode character has three character sets with different meanings, namely A, B, and C. It uses these 3 alternating character sets to encode 128 ASCII codes.

7) Code 93

Code 93 is a continuous alphanumeric code system with variable length. Its characters are set as numbers. 0-9, 26 uppercase letters and 7 special characters (-, ., Space, /, +, %, ￥) and 4 control characters. Each character consists of 3 bars and 3 characters, with a maximum width of 9 elements.

8) Code 49

Code 49 is a multi-line, continuous, variable-length alphanumeric code system. Appeared in 1987, it is mainly used as a symbol on the labels of small items. Use multiple element widths. Its character set is numbers 0-9, 26 uppercase letters and 7 special characters (-, ., Space, %, /, +, %, ￥), 3 function keys (F1, Tuo, F3) and 3 Transform characters, maximum 49 characters.

9) Other code systems

In addition to the above codes, there are other code systems, such as code 25, which appeared in 1977 and is mainly used for electronic component labels; matrix code 25 It is a deformation of code 11; Nixdorf code has been replaced by EAN code. Plessey code appeared in May 1971 and is mainly used in libraries.

2. Classification by dimensionality

1) Ordinary one-dimensional barcodes

Since the advent of ordinary one-dimensional barcodes, they have quickly become popular and Widely used. However, since the information capacity of one-dimensional barcodes is very small, for example, the barcode on a product can only hold 13 Arabic numerals, more information describing the product can only rely on the support of the database. Without the pre-established database, this kind of barcode will It has become water without a source and a tree without roots, so the application scope of barcodes is subject to certain restrictions.

2) Two-dimensional barcode

In addition to the advantages of ordinary barcodes, two-dimensional barcodes also have large information capacity, high reliability, strong confidentiality and anti-counterfeiting, easy production, and low cost. and other advantages.
The American Symbol Company officially launched a two-dimensional barcode called PDF417 in 1991, referred to as PDF417 barcode, which means "portable data file". FDF417 barcode is a portable data file with high density and high information content. It is an ideal means to automatically store and carry large-capacity, high-reliability information such as documents and cards, and can be automatically read by machines.

3) Multi-dimensional barcode

Since the 1980s, people have conducted research on how to improve the information density of barcode symbols. Multidimensional barcodes and container barcodes have become directions for research, development and application.
Information density is an important parameter for describing barcode symbols, that is, the number of letters that can be written in unit length, usually recorded as: number of letters/cm. The main factors affecting information density are the width of strips, empty structures and narrow element systems.
Code 128 and code 93 are successful attempts to increase density. The 128-code code was recommended for use in 1981; the 93-code code was put into use in 1982. The symbol density of these two codes is nearly 30% higher than that of code 39.
With the development of barcode technology and the increasing types of barcode systems, the standardization of barcodes has become increasingly important. To this end, military standard 1189 has been formulated; cross 25 code, 39 code and Coda Bar code ANSI standard MH10.8M, etc. At the same time, some industries have also begun to establish industry standards to meet the needs of development. After that, David Allier developed another 49 yards. This is an unconventional barcode symbology that has a higher density than previous barcode symbologies. Ted Williams GFI988 launched the 16K code. The structure of this code is similar to the 49 code. It is a relatively new code system and is suitable for laser systems.

3. Barcode structure

1) Basic terms of barcode

Barcode is an information code that uses special graphics to represent numbers, letters and certain information. Symbol, Figure A is the bar code of the Miaofu European cake from Hangzhou Dingyuan Food Co., Ltd. A barcode consists of a group of bars and spaces with the same width and reflectivity combined according to certain encoding rules to represent a symbol of complete data. Typically, human-readable characters are placed below the barcode symbol.

Barcode element: The bar and space used to represent the barcode, referred to as elements.
Barcode characters: A set of barcode elements used to represent a number, letter and special symbol.
Bar: In a barcode symbol, a less reflective element.
Empty: In barcode symbols, elements with higher reflectivity.
Bit space: In the barcode symbol, it is located between two adjacent barcode characters and represents any information.
Bar height: The longer dimension among the two-dimensional dimensions of the bar.
Bar width: In the barcode symbol, the length of the quiet zone on both sides is excluded.
Unit element length: In barcode symbols, the nominal width of a narrow element is the unit element width, represented by X.
Two-element wide barcode: In barcode characters, if there are only two widths of elements, namely wide elements and narrow elements, then this coding system is called multiple-element wide barcodes.
Multiple element wide barcode: In a barcode symbol, if there are three or more element widths, it is called a two-element wide barcode.
Logical value of barcode: For two types of elements, wide and long barcodes, the logical value of the wide element is 1, and the logical value of the narrow element is 0. For wide barcodes with multiple elements, if the unit element width is a bar, the logical value The value is 1. If the unit element width is empty, the logical value is 0.
Continuous code type, discrete bar code: In the bar code symbol, if there is a bit gap between two adjacent bar code characters, then this type of code system is called a discrete bar code, as shown in Figure B, otherwise it is called a continuous bar code. type barcode.

Quiet zone start character data character check character end character quiet zone

Figure B structure of barcode symbol

Fixed length, variable length barcode: in barcode Among symbols, if the number of bar characters contained in the symbol is fixed, then this code system is called a fixed-length bar code; otherwise, it is called a variable-length bar code.
Self-verifying bar code: If a printing error does not cause one character to be translated into another character in this code system, then this code system is called a self-verifying bar code.
(n,k) code: A continuous barcode with multiple element widths, also called (n,k) code. N refers to the number of single element widths contained in the barcode symbol, and K refers to the number of bars or spaces in a character.
Barcode symbol density: refers to the number of barcode characters that can be represented in unit length.
Barcode character set: Barcode character set refers to the range of data characters given in the barcode system. The range of data characters given in various barcode systems. In various barcode coding systems, there are two main character sets. One is the numeric character set, which contains the numbers 0~9 and some special characters; the other is the alphabetic and numeric character set, which includes the numbers 0~ 9. Letters A~z and some special characters.
Blots: Points in the empty and quiet zones that have a reflectivity similar to the strip.
Defects|: The ratio of the difference between the reflectivity RL of the strip and the void RL and the reflectance RD of the strip to the reflectance RL of the void, represented by the symbol PCS, that is:
PCS= (RI-RD) RI

2. The structure of barcode symbols

A complete barcode symbol consists of quiet zones on both sides, start characters, data characters, check characters (optional) and termination characters composition. Figure B shows the complete structure of a barcode symbol, where:
Quiet zone: Without any printing characters or barcode information, it is usually white and located on both sides of the barcode symbol. The function of the quiet zone is to prompt the reader, that is, the scanner to prepare to scan the barcode symbol.
Start character: The first character of a barcode symbol is the start character, and its special bar and space structure is used to identify the beginning of a barcode symbol. The reader first acknowledges the presence of this character and then processes a series of pulses obtained by the scanner. Data characters: composed of barcode characters, used to represent certain original data information.
Terminator character: The last character of the barcode symbol is the terminator character. Its special bar and space structure is used to identify the end of a barcode symbol. The reader recognizes the terminating character and knows that the barcode symbol has been scanned. If the end of the barcode symbol. The reader transmits the data location to the computer and provides "effective reading" feedback to the operator. The use of terminating characters avoids the input of incomplete information. When a check character is used, the termination character also instructs the reader to perform check calculations on the data characters.
The starting character, the bar of the terminating character, and the empty structure are usually asymmetric binary sequences. This asymmetry allows the scanner to scan in both directions. When a barcode symbol is scanned in reverse, the reader rearranges the barcode characters into the correct order before performing verification calculations and transmitting the information.
Check characters: Check characters are defined in the barcode system. The check characters of some code systems are required, while the check characters of some code systems are optional. The check character is determined by performing an arithmetic operation on the data characters. When each character in the symbol is decoded, the same arithmetic operation is performed on it and the result is compared with the check character. If the duplicity is consistent, it means that the read information is valid.

IV. Barcode reader

1. Composition of automatic barcode identification system
Automatic barcode identification system generally consists of automatic barcode identification equipment, system software, application software, etc. Automatic bar code recognition equipment includes scanners, decoders, computers and printing equipment, and monitors. Barcode automatic recognition software generally includes the measurement of the scanner's output signal, the identification of the barcode system and scanning direction, the judgment of the logical value, and the data communication between the reader and the computer. According to needs, one computer can be configured with multiple reader terminals, and one decoder can also be networked with several scanners to form a data collection network. Barcode printing technology: The printing quality of barcode symbols will directly affect the recognition effect and the performance of the entire system. Therefore, the corresponding printing technology and equipment must be selected according to printing standards in order to print barcode symbols that meet the specifications. Barcode symbol printing carrier, printing coating, printing equipment, printing technology and software development of light printing system are all the contents to be studied in barcode printing technology.

2. Barcode reading equipment and classification

Barcode reading equipment can be divided into two major categories

1) Online readers

Online readers can be divided into multi-functional readers and various online special readers according to their functions and uses. This type of reader is generally powered directly by AC power, and is connected by a cable between the reader and the computer or communication device to transmit data.

In addition to the function of identifying a variety of commonly used code systems, the multi-function reader can also add programmable functions, display functions, and multi-machine network communication functions according to different needs.

2) Portable readers

Portable readers are equipped with data storage, usually powered by batteries, and are suitable for offline use. After the data is collected, the data is first stored and then dumped to the host. At present, portable readers that can store tens of thousands of barcodes have been launched in the international market, and are widely used in warehouse management, commodity inventory, and various field operations. As an input device for terminals, scanners are also developing rapidly. They can be divided into contact, non-contact, lead-type and fixed scanners. Currently, there are three types of scanners commonly used: pen type, CCD type and laser gun type. The scanner and decoder can be independent of each other or integrated. The scanner should select the corresponding scanning wavelength, resolution and scanning depth of field according to its different uses. With the development of science and technology, innovations in barcode printing technology and corresponding equipment are also rapidly developing, and people can choose according to their needs. Such as various film production and plate making technologies; letterpress and offset printing technologies; suitable for small batch situations and various dot matrix printers, laser printers, thermal printers, and on-site special coding machines, etc. At present, barcode technology products from the United States, Japan and other countries still occupy the international market. Barcode technology is the most widely used, but people are most familiar with the POS system in the field of general merchandise circulation and sales, which is commonly known as a sales terminal or scanning system. POS systems are commonly used in Japan, North America and European countries, and its penetration rate has reached more than 95%. Global adoption of EAN and encoding trends. Japan is the largest user of the EAN system. There are hundreds of thousands of stores using the POS system, and more than 10 million products are marked with barcodes.