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What is the bar code

Release time:2016-10-27 14:37:15

Barcode technology was first produced in the twilight of the twenties, was born in Westinghouse's laboratory. John Kermode, an eccentric inventor, wanted to automate the segregation of postal documents, and every conceivable application of electronic technology was a novelty. His idea is to do the barcode on the envelope, the information in the bar code is the address of the addressee, like today's zip code. For this reason Kermode invented the earliest bar code identification, the design is very simple (Note: This method is called the module comparison method), namely a "bar" that the number "1", two "bars" that the number "2" And so on. He then invented a bar code reading device consisting of a basic element: a scanner (capable of emitting light and receiving reflected light), a method of measuring the reflected signal strip and the null, that is, the edge locating coil, and using the measured results Method, i.e., a decoder.

Kermode's scanners used the newly invented photocells to collect reflected light. "Empty" reflection is a strong signal, "bar" is reflected back to the weak signal. Unlike today's high-speed electronics applications, Kermode uses magnetic coils to measure "stripes" and "voids". Just as a child connects the wire to the battery and wraps it around a nail. The Kermode uses a coil with an iron core to attract a switch when it receives an "empty" signal, releasing the switch and turning on the circuit when the "bar" signal is received. As a result, the earliest bar code readers are noisy. The switch is controlled by a series of relays, "on" and "off" depending on the number of "bars" printed on the envelope. In this way, barcodes are used to sort the letters directly.

Shortly thereafter, Kermode collaborator Douglas Young, in the Kermode code based on some improvements. Kermode code contains a very low amount of information, and difficult to compile more than ten different codes. The Young code uses fewer bars, but utilizes an empty size change between strips, as today's UPC bar code symbols use four different bar sizes. The new bar code symbol can be in the same size space for a hundred different regions to be encoded, and Kermode code can only be encoded for 10 different regions.

It was not until 1949 in the patent literature that for the first time there was an omni-directional bar code symbology invented by Norm Woodland and Bernard Silver, which had never been documented in the prior patent literature and had no precedent for practical use. The idea of ​​Norm Woodland and Bemard Silver is to use Kermode and YOung's vertical "stripes" and "voids" and bend them into rings, much like archery targets. So that the scanner can decode the bar code symbol by scanning the center of the figure regardless of the orientation of the bar code symbol direction.

In a process of continuous improvement using the patented technology, a science fiction writer, Isaac-Azimov, in his book, "The Sun of the Naked," describes a new approach to automatic recognition using information coding. At the time, people felt that the bar code symbol in this book looked like a checkerboard, but today's bar code professionals will immediately realize that this is a two-dimensional matrix bar code symbol. Although this bar code symbol has no orientation, positioning and timing, it is clear that it represents digital coding of high information density.

Until 1970 Iterface Mechanisms developed the "two-dimensional code", the price is suitable for sales of two-dimensional matrix bar code printing and reading equipment. When two-dimensional matrix bar code for the newspaper publishing process automation. Two-dimensional matrix bar code printed on the tape, scanned by today's one-dimensional CCD scanner read. CCD light emitted on the tape, each photocell aligned paper tape in different areas. Each photocell according to the bar code on the tape to print a different pattern, combined to produce a high density information pattern. In this way, a single character can be printed on the same size space as a single bar in the early Kermode code. Timing information is also included, so the whole process is reasonable. When the first system to enter the market, including printing and reading equipment, including a full set of equipment to about 5000 US dollars.

Shortly thereafter, with the continuous development of LEDs (light emitting diodes), microprocessors and laser diodes, a new explosion of symbol (symbolic) and its applications was called "bar code industry". Today, few companies or individuals who do not have direct contact with fast and accurate bar code technology are available. Because of the rapid technological progress and development in this field, and every day more and more applications are being developed, it will not be long before the bar code will be as popular as bulbs and semiconductor radios, will make us each person's life Have become more relaxed and convenient.

Bar code is a set of rules according to certain rules of the bar, empty symbols, used to represent a certain character, numbers and symbols of information. Bar code system is designed by bar code symbols, production and scanning to read the composition of the automatic identification system.


Bar code encoding (code system) Description:


There are many types of bar codes, and there are about 20 kinds of code systems, which include:

Code 25 (Code 25), Matrix 25 (Matrix 25), UPC-A Code, UPC-E Code (Code 39), Codabar Code (Codabar), Code 25 (Standard 25) , EAN-13 (EAN-13 international commodity bar code), EAN-8 code (EAN-8 international commodity bar code), China postal code (a variant of matrix 25 yards), Code-B code, MSI code Code11 Code, Code93 Code, ISBN Code, ISSN Code, Code128 Code (Code128 Code, including EAN128 Code), Code39EMS (EMS Special 39 Code) and other one-dimensional bar code and PDF417 two-dimensional bar code.

At present, the international widely used bar code types are EAN, UPC code (commodity bar code, used in the world to uniquely identify a commodity.We are the most common in the supermarket is the bar code), Code39 code (can represent numbers and letters , In the management of the most widely used), ITF25 code (in the logistics management applications more), Codebar code (for medical, books), Code93 code, Code128 code. EAN code is widely used in the world today bar code has become the basis of electronic data interchange (EDI); UPC code is mainly used in the United States and Canada; in various types of bar code applications, Code39 code for its use of digital And alphabet in the form of internal management in various industries are widely used; in blood banks, libraries and photo shop business, Codebar code is also widely used.

In addition to the above-mentioned one-dimensional bar code, the two-dimensional bar code has been in rapid development, and found in many areas of application.


Bar code system of distinction


UPC: (unified product code) can only represent the number of A, B, C, D, E four versions of the version A - 12-bit digital version E - 7 digits the last bit for the parity bit width is 1.5 "high 1 ", And the background to be clear and mainly used in the United States and Canadian W Canada area for industrial, pharmaceutical, warehouse and other departments

When the UPC is decoded as 12 bits, the definition is as follows: Bit 1 = Digital ID (established by the UCC (Uniform Code Council).) 2-6 bits = Manufacturer's identification number (including first digit) 7-11 = Unique manufacturer's product code Bit 12 = used for error detection

Code 3 of 9: can represent letters, numbers and other symbols a total of 43 characters: A-Z, 0-9, -. $ / +%, Pace barcode length is variable, usually with "*" Start, stop character Check code No code density between 3 - 9.4 characters per inch Blank area is 10 times narrower strip For industrial, book, and ticket automation management

Code 128: Indicates high-density data, string strings Variable-length symbols include checksums in three different versions: A, B, and C can be 128 characters in the A, B, or C three string collection For industrial, warehouse, retail and wholesale

Interleaved 2-of-5 (I2 of 5): can only represent the number 0 -9 variable-length continuity bar code, all the bars and empty code, the first number from the beginning of the second number from the empty blank Area is 10 times wider than narrow stripes for commodity wholesale, warehouses, airports, production / packaging identification, high bar code reading rates in industry, reliable scanners for reliable scans Highest density in all one-dimensional barcodes

Codabar: can represent numbers 0-9, characters $, +, -, and four characters a, b, c d that can only be used as a start / stop character

Variable length No parity bit Applied to material management, libraries, blood stations and current airport parcels Send blank area 10 times wider than narrow bars Noncontinuous barcodes, each character represented as 4 bars 3 Empty

PDF417 (two-dimensional code): multi-line bar code does not need to connect a database itself can store large amounts of data Application: Hospital, driver's license, material management, transport of goods When the bar code is damaged, error correction can make the bar code can be correct Decoding PDF417, is a Symbol technology company in 1990 development of products. It is a multi-line, continuous, variable length, contains a large number of data symbols. Each bar code has 3 - 90 lines, each line has a starting part, the data part, the termination part. Its character set includes all 128 characters, the maximum data content is 1850 characters.
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