Definitions for "Interlaced scan"
Keywords:  odd, onscreen, ntsc, scan, television
Process of creating a television picture by sequentially drawing odd and even lines on a screen. The process is used by NTSC and several digital television signals.
Historically, TV CRTs are interlaced, while computer CRTs are not. Interlaced means that the electron beam skips every other horizontal line, filling in the missing lines on the next pass. A frame is composed of 2 fields. One field is all of the odd numbered lines, and the other field is all of the even numbered lines.
In a television display, interlaced scan refers to the process of re-assembling a picture from a series of video signals. The "standard" NTSC system uses 525 scanning lines to create a picture (frame). The frame/picture is made up of two fields: The first field has 262.5 odd lines (1,3,5...) and the second field has 262.5 even lines (2,4,6...). The odd lines are scanned (drawn on the screen) in 1/60th of a second, and the even lines follow in the next 1/60th of a second. This presents an entire frame/picture of 525 lines in 1/30th of a second. Analog NTSC video uses interlaced scanning, as do several digital television formats. Formats that include an "i" (1080i, 480i) use interlaced scanning. See also progressive scan.