發(fā)布時間: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:
Bar code system of distinction
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