The modern World  #3  (Flatbed scanner)

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         SCANNERS CONVERT physical images into electronic form, allowing them to be sent over the Internet, displayed on a website stored on a computer, and manipulated using specialized software.  Scanners work by detecting and analyzing light reflected from an opaque image, such as a photographic print.  Some can also scan photographic transparencies by analyzing light that has passed through the image Flatbed scanners contain a unit, called the scan head, that contains a lamp, mirrors, a lens, and an array of CCDs (Charge - Coupled Devices).

             The carriage passes beneath the image;  the lamp shines light on to or through the original;  The mirrors reflect the light on the lens, which focuses it on the CCD array.  Each CCD detects the brightness of light from a particular pixel (picture element) along a horizontal strip and converts this data into an electric signal. 

            For color images, the light is usually passed through red, green, and blue filters and then directed to the CCD array so that it can be broken down into its component colors.  This information is then converted to digital form.  The quality of the image depends on its resolution, measured in dpi (Dots Per Inch)

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