In computing, a scanner is a device that optically scans images, printed text, handwriting, or an object, and converts it to a digital image. Common examples found in offices are variations of the desktop (or flatbed) scanner where the document is placed on a glass window for scanning. Hand-held scanners, where the device is moved by hand, were briefly popular but are now less common due to the difficulty of obtaining a high-quality image. Mechanically driven scanners that move the document are typically used for large-format documents, where a flatbed design would be impractical.

Modern scanners typically use a charge-coupled device (CCD) or a Contact Image Sensor (CIS) as the image sensor, whereas older drum scanners use a photomultiplier tube as the image sensor. A rotary scanner, used for high-speed document scanning, is another type of drum scanner, using 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.

Another category of scanner is 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 having disadvantages compared to traditional scanners, digital cameras offer advantages in speed and portability.

Main Entry: scan·ner
Pronunciation: \ˈska-nər\
Function: noun
Date: 1556
: one that scans: as a: a device for sensing recorded data (as in a bar code) <a supermarket scanner> b: a radio receiver that sequentially scans a range of frequencies for a signal c: a device that scans an image (as a photograph) or document (as a page of text) especially for use or storage on a computer d: a medical device for scanning a living body to collect diagnostic information — compare cat scanner