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Explain the working of Scanner.

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•The document is placed on the glass plate and the cover is closed.
•The inside of the cover in most scanners is flat white, although a few are black. 
•A lamp is used to illuminate the document.
•The lamp in newer scanners is either a cold cathode fluorescent lamp (CCFL) or a xenon lamp, while older scanners may have a standard fluorescent lamp.
•The entire mechanism (mirrors, lens, filter and CCD array) make up the scan head. 
•The image sensor may be a CCD a single row of sensor elements mounted very close to the document.
•The scan head is moved slowly across the document.
•Pass means that the scan head has completed a single complete scan of the document.
•The image of the document is reflected by an angled mirror to another mirror.
•In some scanners, there are only two mirrors while others use a three mirror approach.
•The last mirror reflects the image onto a lens.
•The lens focuses the image through a filter on the CCD (charged Coupled Device) array.
•The brighter regions of the image reflect more light on the CCD and darker image portions produce weaker signals.
•The CCD digitizes the results via an analog-to-digital converter, or ADC, and sends the resulting information to the scanner’s own hardware and then to the host PC.
•The ADC software first decides on the number of bits to be represented in the binary presentation.

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