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The barcode labels and its development |
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| Release time:2013-06-25 Source:admin Reads: | |
| A barcode is an optical machine-readable representation of data relating to the object to which it is attached. Originally barcodes systematically represented data by varying the widths and spacing of parallel lines, and may be referred to as linear or one-dimensional. Later they evolved into rectangles, dots, hexagons and other geometric patterns in two dimensions. Although 2D systems use a variety of barcode labels, they are generally referred to as barcodes as well. Barcodes originally were scanned by special optical scanners called barcode readers. Later, scanners and interpretive software became available on devices including desktop printers and smart phones. An early use of one type of barcode in an industrial context was sponsored by the Association of American Railroads. Developed by General Telephone and Electronics and called ACI, this scheme involved placing colored stripes in various combinations on steel plates which were affixed to the sides of railroad rolling stock. Two plates were used per car, one on each side, with the arrangement of the colored stripes representing things such as ownership, type of equipment, and identification number. The plates were "read" by a trackside scanner barcode labels, for instance, at the entrance to a classification yard while the car was moving past. The project was abandoned after about ten years because the system proved unreliable after long-term use in the field. A series of barcodes labels are used in some kinds of absolute linear encoder. The barcodes are packed close enough together that the reader always has one or two barcodes in its field of view. The relative position of the barcode in the field of view of the reader gives incremental precise positioning, in some cases with sub-pixel resolution. The data decoded from the barcode gives the absolute coarse position. An "address carpet", such as Howell's binary pattern and the Anton dot pattern, is a 2D barcode designed so that a reader, even though only a tiny portion of the complete carpet is in the field of view of the reader. |
