Scanning Definition

Present participle of scan.

The process of refreshing a video screen. Interlaced scanning, which is used with most analog TV systems, involves two fields. Odd lines (field 1) are refreshed in one scan, and even lines (field 2) in the next. Each set of odd and even lines refreshed constitutes a frame refreshed. The scanning rate is a function of the power source of the receiver. For example, the American NTSC standard provides for 30 fps, involving 60 scans, which relates directly to the 60 Hz of the United States power source. The European PAL standard provides for 25 fps, involving 50 scans, which relates directly to the 50 Hz of the European power source. Progressive scanning involves displaying all horizontal scan lines in one frame at the same time, which avoids the problem of interline flicker. See also frame rate, NTSC, and PAL.