scanner definition - computer

An optical device that reads a printed page or transparency and converts it into a graphics image for the computer. The scanner does not recognize or differentiate in any manner the content of the material it is scanning. Everything is converted into a bitmapped image, which is a pattern of dots. See bitmapped graphics.


Optical Character Recognition (OCR)
Optical character recognition systems use scanners to capture a document's contents, but go one step further. They use software to convert the dots into ASCII or EBCDIC text characters so they can be used in word processing, e-mail and other text applications. See OCR and document scanner


Scanners and Cameras
Scanners are similar to digital cameras, except cameras can focus into infinity. Desktop scanners have physical dimensions that determine the size and bulk of the material that can be scanned. Automatic feeders are used to scan batches of paper, typically for OCR jobs.

Scanners are rated in dots per inch (dpi), whereas cameras are rated in total pixels. Both scanners and cameras have an optical resolution (the real lens resolution) and an interpolated resolution computed by software. The higher the optical, the better.

Scanners are also rated by the maximum bit depth of each pixel (how many colors can be stored). At minimum, scanners support 24-bit color, and many go up to 48 bits. See optical resolution, interpolated resolution, 4K resolution, document scanner, flatbed scanner, sheet-fed scanner, handheld scanner, drum scanner, slide scanner, photo scanner and digital camera.




Desktop Scanners
The flatbed scanner is the most common desktop scanner. With the addition of a transparency adapter, which provides a light source from the top, it can scan 35mm slides and film negatives. The slide scanner is specialized for 35mm slides and film negatives and cannot scan photos. Transparencies are scanned one at a time or in groups, depending on the device (see slide scanner).




High-End Flatbed Scanner
Flatbed scanners are used for photos as well as slides, as in this iQsmart scanner from Kodak. This professional scanner has an optical resolution of 5,500 dpi. There is a difference between consumer-oriented scanners and ones that cost $10,000 and up. (Image courtesy of Eastman Kodak.)




High-End Drum Scanner
Drum scanners are widely used for commercial graphics production and applications that require the highest quality scanning (see drum scanner). This earlier Howtek scanner provided an optical resolution up to 4,000 dpi. (Image courtesy of Howtek, Inc.)

Source http://www.yourdictionary.com/computer/scanner