Definition: scanner

(1) A synonym for antivirus program.

(2) A smartphone application that reads barcodes. See mobile tagging.

(3) 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 printed text and convert it into computer-readable characters for editing. 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 stacks 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 color 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. A transparency adapter provides a light source from the top for scanning 35mm slides and film negatives. Slide scanners are specialized for only slides and film (see slide scanner).

High-End Drum Scanner

Drum scanners are 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.)