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Image scanner is an input device, which translates paper documents into an electronic format that can be stored in a computer. The input documents can be typed text, pictures, graphics, or even hand written material. They are also known as optical scanners because optical technology is used for converting an image into electronic form. The two types of image scanners are flat-bed scanners and hand-held scanners. Flat-Bed Scanner: A flat-bed scanner consists of a box having a glass plate on its top and a lid that covers the glass plate. The document to be scanned is placed upside down on the glass plate. When the scanner is activated the light source which is situated below the glass plate moves horizontally from left to right. After scanning one line the light beam moves up a little and scans the next line. The process is repeated until the document is scanned completely. Hand-Held Scanner: A hand-held scanner consists of a set of light emitting diodes encased in a small case that is convenient to hold in hand during operation. During scanning the scanner is dragged slowly from one end of the document to the other with its light on. Dragging should be very steady over the document, otherwise the conversion into its bit map will not be correct. They are mostly used where high accuracy is not important and the volume of the scanned document is low. They are cheaper than flatbed scanners. . The limitations of image scanners are:. • Word processing cannot be done on the input documents, as the documents are stored as images instead of text. • Storing the document as an image requires lot of storage space than compared to storing the document as a text.