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Usage Since their invention in the 20th century, barcodes -- especially the UPC code -- have slowly become an essential part of modern civilization. Their use is widespread, and the technology behind barcodes is constantly improving. Some modern applications of barcodes include: Technology of barcodes A linear barcode is a binary code (1s and 0s). The lines and spaces are of varying thicknesses and printed in different combinations. To be scanned, there must be accurate printing and adequate contrast between the bars and spaces. Scanners employ various technologies to "read" codes. The two most common are lasers and cameras. Scanners may be fixed position, like most supermarket checkout scanners, or hand-held devices, often used for the taking of inventories. Notwithstanding its inauspicious beginning, the barcode has become a remarkable success, a workhorse in many and varied applications. One of the first successful barcodes, Code 39 developed by Dr. David Allais, is widely used in logistical and defense applications. Code 39 is still in use today, although it is less sophisticated than some of the newer barcodes. Code 128 and Interleaved 2 Million other codes that attained some success in niche markets. The Universal Product Code The best-known and most widespread use of barcodes has been on consumer products. The Universal Product Code, or U.P.C., is unique because it was developed by the user community. Most technological innovations are first invented and then a need is found for the invention. The U.P.C. is a response to a business need first identified by the US grocery industry in the early 1970s. Believing that automating the grocery checkout process could reduce labor costs, improve inventory control, speed up the process, and improve customer service, six industry associations, representing both product manufacturers and supermarkets, created an industry wide committee of industry leaders. Their two-year effort resulted in the announcement of the Universal Product Code and the U.P.C. barcode symbol on April 1, 1973. The U.P.C. made its first commercial appearance on a package of Wrigley's gum sold in Marsh's Supermarket in Troy, Ohio in June 1974. Economic studies conducted for the grocery industry committee projected over $40 million in savings to the industry from scanning by the mid-1970s. Those numbers were not achieved in that time frame and there were those who predicted the demise of barcode scanning. The usefulness of the barcode required the adoption of expensive scanners by a critical mass of retailers while manufacturers simultaneously adopted barcode labels. Neither wanted to move first and results looked unpromising for the first couple of years, with Business Week eulogizing The Supermarket Scanner That Failed. Symbologies The mapping between messages and barcodes is called a symbology. The specification of a symbology includes the encoding of the single digits/characters of the message as well as the start and stop markers into bars and space, the size of the quiet zone required to be before and after the barcode as well as the computation of a checksum. Linear symbologies can be classified mainly by two properties: Some symbologies use interleaving. The first character is encoded using black bars of varying width. The second character is then encoded, by varying the width of the white spaces between these bars. Thus characters are encoded in pairs over the same section of the barcode. Interleaved 2 of 5 is an example of this. Stacked symbologies consist of a given linear symbology repeated vertically in multiple. There are a large variety of 2-D symbologies. The most common are matrix codes, which feature square or dot-shaped modules arranged on a grid pattern. 2-D symbologies also come in a variety of other visual formats. Aside from circular patterns, there are several 2-D symbologies which employ steganography by hiding an array of different-sized or -shaped modules within a user-specified image (for example, DataGlyph). Scanner/symbology interaction Linear symbologies are optimized to be read by a laser scanner, which sweeps a beam of light across the barcode in a straight line, reading a slice of the barcode light-dark patterns. Stacked symbologies are also optimized for laser scanning, with the laser making multiple passes across the barcode. 2-D symbologies cannot be read by a laser as there is typically no sweep pattern that can encompass the entire symbol. They must be scanned by a camera capture device. Scanners (barcode readers) The earliest, and still the cheapest, barcode scanners are built from a fixed light and a single photosensor that is manually "scrubbed" across the barcode. A later design, the "laser scanner," uses a polygonal mirror or galvanometer-mounted mirror to scan a laser across the barcode -- initially only in a straight line, but eventually in complicated patterns so the reader could read barcodes at any angle. In the 1990s some barcode reader manufacturers began working with digital cameras to capture barcodes, both linear and 2D. That technology has since been perfected and now often surpasses laser scanners in performance and reliability. More recently, off-the-shelf digital cameras now have enough resolution to capture both 1D and 2D barcodes. Increasingly companies are looking to incorporate barcode scanning software into cameraphones. However, the camera phone optics are not well suited for standard codes that were designed for industrial dedicated scanners. As a result, new codes are being designed for mobile use such as color code and mCode. Verifier (barcode inspection) Bar code verifiers are primarily used by businesses that print bar codes, but all trading partners in the supply chain will test bar code quality. It is important to "grade" a bar code to ensure that any scanner in the supply chain can read the bar code. Retailers levy large fines and penalties for non-compliant bar codes. Bar code verifiers work in a similar way that a scanner works but instead of simple decoding a bar code, a verifier will perform a series of 8 tests. Each test is given a grade 0.0-4.0 (F-A) and the lowest of any of the tests is the scan grade. For most applications a 2.5 (C) grade is the minimum acceptable grade. Bar Code Verifier Standards Bar code verifier manufacturers: Benefits of using barcodes In point-of-sale management, the use of barcodes can provide very detailed up-to-date information on key aspects of the business, enabling decisions to be made much quicker and with more confidence. For example: Bar code scanners are also relatively low costing and extremely accurate – only about 1/100000 entries will be wrong. Linear barcodes Stacked barcodes | class="wikitable" ! Symbology !! Notes |- | Codablock || Stacked 1D barcodes. |- | Code 16K || Based on 1D Code 128. |- | Code 49 || Stacked 1D barcodes from Intermec Corp. |- | PDF417 || The most common 2D barcode. Public domain. |- | Micro PDF417 || |
2D barcodes
A matrix code, also known as a 2D barcode, is a two-dimensional way of representing information. It is similar to a linear (1-dimensional) barcode, but has more data representation capability.
See also
Further reading
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