Home Uncategorized Who knows what program is used to write the bar code on the back of the commodity package? Thanks

Who knows what program is used to write the bar code on the back of the commodity package? Thanks

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bar code is only a coding method, which has nothing to do with programming language. It can be realized by using any programming tool
recognition principle of bar code
due to different wavelengths of visible light reflected by objects of different colors, white objects can reflect visible light of various wavelengths, while black objects absorb visible light of various wavelengths. Therefore, when the light emitted by the light source of the bar code scanner passes through the diaphragm and convex lens 1 and shines on the black-and-white bar code, the reflected light is focused by the convex lens 2, Irradiate on the photoelectric converter, so the photoelectric converter receives the reflected light signal with different strength corresponding to the white bar and black bar, converts it into the corresponding electrical signal and outputs it to the amplification and shaping circuit. The width of the white bar and black bar is different, and the duration of the corresponding electrical signal is also different. However, The electrical signal corresponding to the bar and space of the bar code output by the photoelectric converter is generally only about 10mV and cannot be used directly. Therefore, first send the electrical signal output by the photoelectric converter 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 needs to be added after the amplification circuit, The analog signal is converted into digital electrical signal so that the computer system can accurately interpret. The pulse digital signal of the shaping circuit is translated into digital and character information by the decoder. It identifies the code system and scanning direction of the bar code symbol by identifying the start and end characters; The number of bars and spaces is determined by measuring the number of pulse digital electrical signals 0 and 1. The width of bars and spaces is determined by measuring the duration of 0 and 1 signals. In this way, the number of bars and spaces, the corresponding width and the code system used of the bar code symbols can be obtained. According to the coding rules corresponding to the code system, the bar symbols can be replaced with corresponding digital and character information, The whole process of bar code identification and reading is completed by sending it to the computer system for data processing and management through the interface circuit.
coding rules

uniqueness: the same product with the same specification corresponds to the same product code, and different specifications of the same product correspond to different product codes. Different commodity codes are assigned according to different properties of products, such as weight, packaging, specification, smell, color, shape, etc. Permanence: once the product code is assigned, it will not be changed, and it is lifelong. When this product is no longer produced, its corresponding product code can only be shelved and cannot be used repeatedly and then distributed to other commodities. Meaningless: in order to ensure that the code has enough capacity to meet the needs of frequent product upgrading, it is best to use meaningless sequence code

the code system difference of bar code

UPC: (unified product code) can only indicate that the number has four versions: A, B, C, D and E. version a – 12 digit version e – 7 digit version. The last digit is the check digit. The size is 1.5 “wide and 1” high “, and the background should be clear. It is mainly used in the United States and Canada for industry, medicine Warehouse and other departments

when UPC is decoded as 12 bits, it is defined as follows: the first bit = digital identification (which has been established by UCC) The 2nd-6th digit = manufacturer’s identification number (including the first digit), the 7th-11th digit = unique manufacturer’s product code, the 12th digit = used for error detection

code 3 of 9: it can represent letters, numbers and other symbols, with a total of 43 characters: a – Z, 0 – 9, -. $/+%, The length of pace bar code can be changed. Usually “*” is used as the start and end check code. The code density is between 3-9.4 characters /inch, and the blank area is 10 times that of the narrow bar. For industry, books and ticket automatic management

code 128: indicates high-density data. The variable length symbol of string contains three different versions of check code: A, B, And C can use 128 characters in three string sets of a, B, or C respectively for industry, warehouse, retail and wholesale

2-of-5 (I2 of 5): it can only represent the number 0-9 variable length continuous bar code, and all bars and spaces represent codes. The first number starts with a bar, and the second number consists of spaces. The blank area is 10 times wider than the narrow bar. It can be used for commodity wholesale, warehouse, airport Production /packaging identification and high reading rate of bar code in industry. It can be used for reliable scanning by fixed scanner. The highest density of all one-dimensional bar codes is

Codabar (CodeBar code): it can represent numbers 0-9, characters $, +, -, and four characters a, B, C and D that can only be used as start /stop characters

variable length without check digit. It is applied to material management In the sending of packages from libraries, blood stations and the current airport, the blank area is 10 times wider than the narrow bar. Each character is represented as four three empty

PDF417 (two-dimensional code): the bar code composed of multiple lines does not need to be connected to a database. It can store a large amount of data and be used in hospitals, driver’s licenses, material management and cargo transportation. When the bar code is damaged to a certain extent, Error correction can make the bar code decode PDF417 correctly. It is a product developed by symbol technology company in 1990. It is a symbol identification with multiple lines, continuity, variable length and large amount of data. Each bar code has 3 – 90 lines, and each line has a starting part, data part and ending part. Its character set includes all 128 characters, and the maximum data content is 1850 characters

one dimensional bar code only expresses information in one direction (generally horizontal direction), but does not express any information in the vertical direction. Its certain height is usually used to facilitate the alignment of the reader
the application of one-dimensional bar code can improve the speed of information entry and reduce the error rate, However, one-dimensional bar code also has some shortcomings:
* small data capacity: about 30 characters
* can only contain letters and numbers
* the bar code size is relatively large (low space utilization)
* after the bar code is damaged, it cannot read the bar code that stores information in two-dimensional space in horizontal and vertical directions, It is called 2-bar code

like one-dimensional bar code, two-dimensional bar code also has many different coding methods, or coding systems. In terms of the coding principle of these coding systems, they can generally be divided into the following three types
1 Linear stacked QR code is produced by stacking multiple one-dimensional codes vertically on the basis of one-dimensional bar code coding principle. Typical code systems, such as code 16K, code 49, PDF417, etc
2. Matrix QR code is encoded in a rectangular space through the different distribution of black and white pixels in the matrix. Typical code systems, such as Aztec, Maxi code, QR code, data matrix, etc
3. Postal codes are encoded by bars of different lengths, which are mainly used for mail coding, such as Postnet, BPO 4-state

in many kinds of two-dimensional bar codes, the commonly used code systems are: data matrix, Maxi code, Aztec, QR code, vericode, P
DF417, ultracode, code 49, code 16K, etc.:
* data matrix is mainly used for the identification of small parts in the electronic industry. For example, this code is printed on the back of Intel’s Pentium processor
* Maxi code is developed by United Parcel Service (UPS) for parcel sorting and tracking
* Aztec is launched by Welch Allyn, which can hold up to 3832 numbers or 3067 alphabetic characters or 1914 bytes of data

next, let’s take PDF417 code as an example to introduce the characteristics and characteristics of two-dimensional bar code

I) introduction to PDF417

the PDF417 code was invented by Dr. Wang Yinjing, a Chinese living in the United States. Pdf is an acronym for portable data file, which means “portable data file”. Because each symbol character constituting the bar code is composed of four bars and four spaces, if the narrowest bar or space constituting the bar code is called a module, the total number of modules of the above four bars and four spaces must be 17, so it is called 417 code or PDF417 code

II) features of PDF417

1 With large information capacity, PDF417 code can express not only letters, numbers and ASCII characters, but also binary numbers. In order to make the coding more compact and improve the information density, PDF417 has three formats during coding:
* the extended alphanumeric compression format can accommodate 1850 characters
* binary /ASCII format can accommodate 1108 bytes
* the digital compression format can hold 2710 numbers
2. Error correction capability one dimensional bar code usually has verification function to prevent wrong reading. Once the bar code is stained, it will be rejected. The two-dimensional bar code can not only prevent errors, but also correct them. Even if the bar code is partially damaged, it can restore the correct information
3. The printing requirements are not high. Ordinary printing equipment can print and fax copies can also be read
4. PDF417 code can be read by a variety of reading devices, laser reader with grating and image reader with linear and surface scanning
5. The size can be adjusted to adapt to different printing spaces
6 The disclosure of code system has formed an international standard, and China has formulated the national standard of 417 code

III) the error correction function of PDF417

the error correction function of two-dimensional bar code is realized by repeatedly representing (redundancy) some information. For example, in the PDF417 code, in addition to the information of the line, there are some information reflecting the characters in other positions (error correction code). In this way, even when a part of the bar code is damaged, its information can be restored through the error correction code existing in other positions

the error correction capability of PDF417 is divided into 9 levels from 0 to 8 according to the number of error correction code words, as shown in Figure 4. The higher the level, the more correction code words, the stronger the correction capability, and the larger the bar code. When the correction level is 8, even if the bar code is 50% dirty, it can be read out correctly, as shown in Figure 5

IV) several variants of PDF417

as shown in Figure 6, PDF417 also has several variant coding forms:
* PDF417 truncates the code. In a relatively “clean” environment, the possibility of bar code damage is very small, so the line indicator on the right can be omitted and the terminator can be reduced
* PDF417 microcode is a further reduced PDF code
* macro PDF417 code when the file content is too long to be represented by one PDF417 code, it can be represented by macro PDF417 code containing multiple (1 ~ 99999) bar code blocks

advantages of two-dimensional bar code

from the above introduction, it can be seen that two-dimensional bar code has obvious advantages compared with one-dimensional bar code. It can be summarized in the following aspects:
I) larger data capacity
PDF417 code in the figure contains all the words in the text box
2) beyond the limit of alphanumeric
3) the relative size of bar code is small
4) it has the ability to resist damage

not sure

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