In the context of computing,
the function of a
scanner is to convert various images to a digital images. Images that are
analyzed and converted are,
printed text, or
handwriting, or an object (such as an ornament). The majority of scanners today are
usually some kind of variation of the desktop (or flatbed) scanner.
The flatbed is the scanner most commonly used in offices. Hand-held scanners are
rarely used nowadays because of their poorer quality images. 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.
The rotary scanner is another type of scanner and is used for high-speed
document scanning. The rotary scanner is a drum scanner, but instead of a
photomultiplier, it uses a CCD array.
Planetary scanners are scanners that take photographs of books
and documents. 3D scanners are used for producing three-dimensional models of
objects and is considerably more expensive relative to
other types of scanners.
Yet another category of scanners that are gaining popularity are
camera scanners which are based on the concept of reprographic cameras. Due
to the increasing resolution and new features such as anti-shake,
cameras become an attractive alternative to regular scanners.
cameras still contain disadvantages compared to traditional scanners, but offer unmatched advantages in speed and portability.