<p><strong>Noun</strong></p><ul><li>A person or thing that scans.</li><li><em>(Also called optical reader)</em> Computers: a device that scans printed, handwritten, barcode, or other visual data and encodes it into digital format (optical scanning).</li><li>Photography: any device for exposing an image on film, a sensitized plate, etc., by tracing light along a series of many closely spaced parallel lines.</li><li><em>(In aerial photography)</em> a device for estimating the ratio of aircraft speed to aircraft altitude.</li><li>A photoelectric device for scanning a picture to determine automatically the density of the hue or value in each area for transmission by wire or radio or for preparation of color process printing plates.</li><li>A computer-aided electronic system using photoelectric cells to separate copy, as color illustrations, into its primary colors, correct color copy, and produce a set of color separations ready for proofing or printing.</li><li>Radio: a radio receiver, used especially by police, firefighters, and the press, that continuously tunes to preselected frequencies, broadcasting any signal that it detects.</li><li>Medicine/Medical, Biology: a device for examining a body, organ, tissue, or other biologically active material (e.g., CAT scanner, MR scanner, PET scanner, sonogram).</li></ul>