Bar+Code+Reader

A bar code reader is an input device that is used for reading bar codes. A bar code is a sequence of white and black bars that contain encoded information about the product, this is known as a product identifier. The product identifier is normally prinited in human-readable form beneath the bar code. Bar codes can be found on most products.

A bar code reader conists of a light scource, a lens, photoelectic detectors and decoder circuitry to analyse the bar code's image data and generate character codes. The scanner's light sourse illuminates the bar code's black and white bands. Due to more light being reflected off of white bands than the black bands, a pattern of reflection is formed which is then converted from an optical form to an electical form. This data is then analysed and decoded into character form. The scanner outputs the character codes as a sequence of binary digits for processing by a computer.




 * 1) Scanning head shines LED or laser light onto barcode.
 * 2) Light reflects back off barcode into a light-detecting electronic component called a photoelectic cell. White areas of the barcode reflect most light; black areas reflect least.
 * 3) As the scanner moves past the barcode, the cell generates a pattern of on-off pulses that correspond to the black and white stripes. So for the code shown here ("black black black white black white black black"), the cell would be "off off off on off on off off."
 * 4) An electronic circuit attached to the scanner converts these on-of pulses into binary digits (zeros and ones).
 * 5) The binary digits are sent to a computer attached to the scanner.