In computing, a scanner is a device that analyzes images, printed text, or
handwriting, or an object (such as an ornament) and converts it to a digital image.
Most scanners today are variations of the desktop (or flatbed) scanner.
The flatbed scanner is the most common in offices. Hand-held scanners, where
the device is moved by hand, were briefly popular but are now not used due to the
difficulty of obtaining a high-quality image. Both these types of scanners use
charge-coupled device (CCD) or Contact Image Sensor (CIS) as the image sensor,
whereas older drum scanners use a photomultiplier tube as the image sensor.
Another category of scanner is a rotary scanner, used for high-speed document
scanning. This is another kind of drum scanner, but it uses a CCD array instead of a
photomultiplier.
Other types of scanners are planetary scanners, which take photographs of books and
documents, and 3D scanners, for producing three-dimensional models of objects, but
these types of scanner are considerably more expensive than other types of scanners.
Another category of scanner are
digital camera scanners, which are based on the concept of reprographic cameras.
Due to increasing resolution and new features such as anti-shake, digital cameras have
become an attractive alternative to regular scanners. While still containing disadvantages
compared to traditional scanners, digital cameras offer unmatched advantages in speed and
portability.
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