Barcode Scanner (or Barcode Reader) is an electronic device for reading printed barcodes.
Laser Scanners use a laser beam as the light source and typically employ either a reciprocating mirror or a rotating prism to scan the laser beam back and forth across the barcode.
CCD Scanners 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 photodiode 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 barcode is generated the reader by sequentially measuring the voltages across each sensor in the row.
Linear Image Scanners use a small video camera to capture an image of a barcode. The reader then uses sophisticated digital image processing techniques to decode the barcode.