Interlaced scan is one of two methods used for "painting" an image on a television screen (the other being progressive scan). Designed for the analog NTSC television system, interlaced scanning uses two fields to create a frame. One field contains all the odd lines in the image, the other contains all the even lines of the image. A television scans 60 fields every second (30 odd and 30 even). These two sets of 30 fields are combined to create a full frame every 1/30th of a second, resulting in a display of 30 frames per second. Drawbacks to interlaced scanning compared to progressive scanning include flicker, lower resolution and quality issues.
Compare with progressive scan.