It is a process by which we display images on raster scanned display device (RSDD). This is useful because it causes less flickering. In short we can say by this method we improve the picture quality in a video transmission without using any extra bandwidth. Randall. C. Ballard discovered it. Interlace can also improve the picture quality of still images, at times it also cause various kinds of distortion. The basic concept to develop this concept is the screen has to be highly illuminated to prevent visible flicker. Since we can improve the picture quality without increasing the bandwidth which helps us in reducing the cost because greater the bandwidth higher is the cost. Interlacing is highly supported by TV, DV, and DVB etc.