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Working of barcode reader

  1. Working of Barcode Reader
  2. What is Barcode??  Barcodes are simply a set of symbols used to represent alpha-numeric information instead of seeing a number “1”, or letter “A”, you would see a series of black and white bars in various combinations and in different widths.  These are used to encode data. The data encoded in such bars can be decoded again to represent it in human readable form.
  3. What is Barcode Reader??  A barcode reader (or barcode scanner) is an electronic device for reading printed barcodes.  Like a flatbed scanner, it consists of a light source, a lens and a light sensor translating optical impulses into electrical ones.  Additionally, nearly all barcode readers contain decoder circuitry analyzing the barcode's image data provided by the sensor and sending the barcode's content to the scanner's output port.
  4. Brief History  As far back as the 1960s, barcodes were used in industrial work environments. Some of the early implementations of barcodes included the ability identify rail road cars.  In the early 1970s, common barcodes started appearing on grocery shelves. To automate the process of identifying grocery items, UPC barcodes were placed on products.  Today, barcodes are just about everywhere and are used for identification in almost all types of business.
  5. Working:  A bar code consists of a series of parallel, adjacent bars and spaces. Symbologies are used to encode small strings of character data into a printed symbol.  A bar code reader decodes a bar code by scanning a light source across the bar code and measuring the intensity of light reflected back by the white spaces. The pattern of reflected light is detected with a photodiode which produces an electronic signal that exactly matches the printed bar code pattern. This signal is then decoded back to the original data by electronic circuit.
  6. Pen type readers and Laser Scanners  Pen type readers consist of a light source and a photo diode that are placed next to each other in the tip of a pen or wand.  To read a bar code, you drag the tip of the pen across all the bars in a steady even motion. The photo diode measures the intensity of the light reflected back from the light source and generates a waveform that is used to measure the widths of the bars and spaces in the bar code.  Dark bars in the bar code absorb light and white spaces reflect light so that the voltage waveform generated by the photo diode is an exact duplicate of the bar and space pattern in the bar code. This waveform is decoded by the scanner in a manner similar to the way Morse code dots and dashes are decoded.
  7. CCD Readers  CCD (Charge Coupled Device) readers use an array of hundreds of tiny light sensors lined up in a row in the head of the reader. Each sensor can be thought of as a single photo diode that measures the intensity of the light immediately in front of it.  Each individual light sensor in the CCD reader is extremely small and because there are hundreds of sensors lined up in a row, a voltage pattern identical to the pattern in a bar code is generated in the reader by sequentially measuring the voltages across each sensor in the row.
  8. Camera based Readers  The newest type of bar code reader currently available are camera-based readers that use a small video camera to capture an image of a bar code. The reader then uses sophisticated digital image processing techniques to decode the bar code.  Video cameras use the same CCD technology as in a CCD bar code reader except that instead of having a single row of sensors, a video camera has hundreds of rows of sensors arranged in a two dimensional array so that they can generate an image.
  9. Interfacing a Barcode reader to a PC
  10. Interfacing  Bar code readers are available with two types of output - either "keyboard wedge" output or RS232 output. The bar code readers with keyboard wedge output plug directly into the keyboard port on your PC . The other option is RS232.With this type of bar code reader we can connect available serial port on the back of PC.
  11. Why use Barcodes??  When barcodes are used in the business process, procedures are automated to increase productivity and reduce human error.  Whenever there is a need to accurately identify or track something, bar-coding should be used. For example, in a data entry work environment, workers may be required to enter an enormous amount of data into a customer database system.  Instead of manually typing a customer identification number into a database, if the information is contained in a barcode, a data entry operator may scan it in. This would increase automation and reduce human error.
  12. Barcode types and use: The type of barcode to use for a particular situation depends upon:  The use.  The data encoded in the barcode.  How the barcode will be printed. There are several different types of barcode standards for different purposes - these are called symbologies. Each type of symbology (or barcode type) is a standard that defines the printed symbol and how a device, such as a barcode scanner, reads and decodes the printed symbol.
  13. Contd..  When multiple parties or companies are involved in the ID process, industry standards are usually established. Note that the standard is not necessarily the same as the barcode symbology. If an industry standard has been established for the customer's use of bar-coding, then most likely there will not be a choice in selecting the barcode symbology.  Barcode standards define how to use the barcode symbology in a particular situation. For example, ISBN is a standard for labeling books and periodicals that uses the EAN-13 symbology.
  14. Two types of Barcodes(examples): Linear Barcodes 2D Barcodes Code 128 Data Matrix UPC Pdf 417
  15. Some Established Barcode Industry Standards: Established standard Common use Symbology AIAG Automotive item identification Data Matrix UPCA, EAN13 Items for sale worldwide UPC/EAN MIL-STD-130L US Department of defense Data Matrix SSCC-18 Shipping cartons Code 128
  17. Applications:  RETAIL APPLICATIONS  Super markets  Counter-mounted Bar Code scanners  Universal Product Code (UPC)  Price and description information  WARE HOUSING  HEALTH CARE APPLICATIONS  Drugs, devices, instruments  Identification of expiry date  Blood banking • Blood group • Expiry date • Donor traceability
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