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What is an image scanner? Explain the two types of image scanners. Give the limitations of image scanners?

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.