08-16-2017, 09:17 PM
barcode technology pdf seminar download
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 spacings of parallel lines, and may be referred to as linear or one-dimensional (1D). Later they evolved into rectangles, dots, hexagons and other geometric patterns in two dimensions (2D). Although 2D systems use a variety of symbols, 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 smartphones.
An early use of one type of barcode in an industrial context was sponsored by the Association of American Railroads in the late 1960s. Developed by General Telephone and Electronics (GTE) and called KarTrak ACI (Automatic Car Identification), 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.[1] The plates were "read" by a trackside scanner located, for instance, at the entrance to a classification yard while the car was moving past.[2] The project was abandoned after about ten years because the system proved unreliable after long-term use in the field.[1]
Barcodes became commercially successful when they were used to automate supermarket checkout systems, a task for which they have become almost universal. Their use has spread to many other tasks that are generically referred to as automatic identification and data capture (AIDC). The very first scanning of the now ubiquitous Universal Product Code (UPC) barcode was on a pack of Wrigley Company chewing gum in June 1974.[3]
Other systems have made inroads in the AIDC market, but the simplicity, universality and low cost of barcodes has limited the role of these other systems until the 2000s (decade), over 40 years after the introduction of the commercial barcode, with the introduction of technologies such as radio frequency identification, or RFID.
A short description on how barcode technology works.
Barcode technology works of off a principle called symbology. Symbology at its basic form is what defines the barcode; it determines the mapping and interpretation of the encoded information or data. This encoding allows the scanning device to know when a digit or character starts and when it stops, similar to a binary representation. We recognize barcodes as an array of parallel lines alternating between white and black lines. Barcode technology provides a simple and inexpensive method of recording data or information in a number of applications.
The symbologies of the barcode technology can be arranged or mapped in a variety of ways. A continuous symbology is marked by the characters beginning with a black line and ending with a white line or space, while discreet symbologies have characters encoded as a black line a space and then another black line. This takes care of the characters and how each individual number or letter is read. The lines of a barcode also have variances in encoding the widths of the lines. Some barcode technology systems use two separate widths to determine the character while others use multiple width lines. The use of any of these encoding styles depends, of course, on the application for which the barcode technology is being used.
The line or linear barcode technology is sometimes referred to as 1D encoding. While we are most familiar with these barcodes, there are more complex codes that employ the use of dot matrixes to achieve a more complex encoding process that can store and identify far more information. These are referred to as 2D or, in some cases dataglyphs. They are comprised of miniature dots, like the old dot matrix printers, which create patterns that are read in the scanning process. They are not limited to this format and can be comprised of circular patterns or a collection of shapes and modules inserted into a specified image for a user.
In order to read the data of barcode technology it needs to be scanned by a laser and then interpreted. The scanners, or lasers, used to read the barcodes measures the light reflected form the linear barcode technology and can distinguish between the white and black lines. Calibration of the laser and system needs to be done to ensure the proper interpretation of the code itself. This has to do with whether it is a continuous or discreet symbology, 1D or 2D images, and whether it uses two width or multiple width lines. The most common lasers used are helium neon lasers due to their low energy consumption and efficiency.
The complex or 2D barcodes can not be read by a simple laser as the linear barcode technology can. The barcode needs an all encompassing reader as the full image needs to be read. Linear barcode technology only needs to be swept across to read it as the lines are the same regardless of the position of the laser. 2D codes must be read or scanned by an image based scanner, similar to the scanners used at home or in offices to scan documents and images. They are more costly but supply more information and data. These are used in encoding URLs for cellular phone use and higher end applications.