Barcode scanner
A barcode scanner is a scanning device which can read, or sense, bar code information and which includes means for converting bar code information into digital information. A bar code normally includes several bar code characters. A bar code character is a group of lines (bars) and spacings that represent a single number or letter. A bar code symbol is a collection of several bar code characters which represent an identification of a particular object. Bar code symbols are formed from bars or elements that are typically rectangular in shape with a variety of possible widths. The specific arrangement of elements defines the character represented according to a set of rules and definitions specified by the symbology used. The relative width of the bars and spaces is determined by the type of symbology used, and the actual size of the bars and spaces is usually determined by the application. A bar code label may be read by a scanner that detects reflected or refracted light from the bars and spaces that comprise the bar code characters. Bar code scanners generally fall within one of two types, laser scanners and contact scanners. A barcode scanner with a laser scanning system uses a laser diode as a light source, scans its emission output on barcode information (pattern) by a scanning mirror, reads intensity of a reflected light from a barcode by a photodetector, so that a barcode signal corresponding to the barcode information is obtained. In a laser barcode scanner, a laser emits a beam which sweeps across a barcode and reflects a portion of the light back into the scanner. As the laser beam sweeps across the bars and spaces, light is absorbed by the dark bars and reflected off the white spaces at a data frequency or rate which varies as a function of the sweep speed and width of the bars and spaces. A mirrored polygon directs the beam against a plurality of stationary mirrors, and collects the beam after it is reflected by an item bearing a barcode label. A motor rotates the mirrored polygon, and a detector receives the returning beam. The pattern produced by such a scanner is characterized by lines oriented at various angles to one another. As the scan lines traverse the barcode, light is typically back scattered into a hemisphere or cone perpendicular to the barcode. In order to read the barcode, some of the scattered light must be collected by the scanner and converted into electrical energy which is suitably decoded. Contact scanners are sometimes also referred to as "pencil wands" due to their narrow, pencil-like shape. Contact scanners scan a barcode by emitting visible red or infrared light such as, for example, from an LED which strikes the bar code while the scanner is moved across the bar code in a linear direction with the tip of the scanner touching the bar code label. Wand readers is commonly used to input data contained in printed bar code labels affixed to selected goods to an attached computer system. Such a bar code provides a method of coding the data such that it will represent the necessary numerical characters needed to identify the product being scanned. Bar code scanners typically operate in one of at least two modes. A scanner may operate in an omnidirectional or multiline scan mode, producing a multiline scan pattern in which an array of scan lines is used to illuminate a bar code. Alternatively, a scanner may operate in a single line mode, producing a single scan line which is used to illuminate a bar code.
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