2-D Barcodes Overview

2-D Barcodes Overview - Two-Dimensional Bar Code Overview...

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www. dataintro .com Page 1 of 4 Two-Dimensional Bar Code Overview What is a bar code? A bar code is simply a series of stripes (usually black) on a light background (usually white) that can be scanned and read directly into a computer. They are interpreted virtually instantaneously and without errors by a bar code reading system. The elements (bars and spaces) in a bar code symbol must be of a consistent, proportional thickness and thinness. The widest element could be as thick as a pencil or as thin as a business card, as long as the corresponding thin bars and spaces in the bar code remain proportionally thin. Bar codes are read the same way that people read text from a page; the reflectance and absorption of light. A light of a given wavelength is beamed and moved across a bar code at a consistent speed. The reflected light is measured with a photoreceptor, tuned to look for light of the given wavelength. The off-and-on (white and black) pattern of the bar code creates an electrical wave that is sent on to a computer chip called a “decoder.” The decoder then deciphers the signal into something the waiting computer understands. Imager and CCD (charge coupled device) bar code scanners read somewhat differently in that they “take a picture” of a bar code symbol, analyse it, and create a conditioned electronic signal that basically mimics that from the reader types described in the paragraphs above. The bar code “symbology” In other point of view, a bar code “symbology” is to bar codes in much what a particular alphabet is to language. Different symbologies of bar codes use different combinations of bars and spaces to represent different characters. Bar code symbologies, like languages, are given different names, like Code 39, UPC, Codabar, PDF417, DataMatrix… There are different symbologies developed in order to satisfy various application requirements. Each has a set of characteristics tuned to these various situations. Recently, there has been a trend toward standardization of symbology selection both within and between user groups and in specific industries. The factors that should be considered when choosing a symbology are mainly two. First, it has to be determined whether or not a particular symbology is required to comply with an existing industry or organization standard. If no standard exists, it is wise to consult with other businesses like your own, in order to determine whether any standard is forthcoming. The second factor is the type and amount of data that needs to be encoded. Some codes allow full alphanumeric encodation, but usually do so at the cost of the symbol taking up more space. Also, the size of the article or label being encoded must be taken into account, keeping in mind that the density of the characters varies greatly between symbologies and printing method. Finally, compatibility with available reading and printing equipment must be taken
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This note was uploaded on 04/11/2008 for the course EE 571 taught by Professor Jacob during the Spring '08 term at SUNY Stony Brook.

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2-D Barcodes Overview - Two-Dimensional Bar Code Overview...

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