Line doubler
（重定向自Line doubling）
A line doubler is a device used to deinterlace video signals prior to display.
The main function of a line doubler is to take an interlaced video source which consists of a two-field frame and create a progressive scan (single non-interlaced frame) output. This can produce a smoother, higher-resolution picture. The additional lines provide greater light output and makes for an image that is smoother and more film like. CRT-based displays (both direct-view and projection) are capable of directly displaying both interlaced and progressive video, and therefore the line-doubling process is an optional step to enhance picture quality. Most other types of display, including LCD, plasma and DLP, generally cannot accept an interlaced signal directly, and therefore some kind of line doubler must be used. This is usually built in and transparent to the user. Progressive scan DVD players also feature a line doubler.