An earlier large-screen TV set that has employed one of several technologies for generating the image. Rear-projection TVs (RPTVs) were developed to extend the size of a TV screen beyond the CRT TV, which for all practical purposes maxed out at 36". Introduced in the 1970s and very popular throughout the 1980s and 1990s, at the end of 2012, Mitsubishi, the only remaining vendor of RPTVs, ceased production of its DLP-based 82" and 92" sets (for a novel rear-projection device, see SPUD
Although RPTVs were still bulky, no CRT TV could have been built with as large a screen. Using mirrors and lenses, the projected image was flipped up and over rather than straight toward the screen.
The Largest Screen for the Money
Early rear-projection systems suffered from a narrow viewing angle. Because the screen itself was a lens, standing up or walking off to the side dramatically changed the brightness. Although newer sets had wider viewing angles and were the only large-screen TVs available for many years, they were nowhere near as visually dazzling as the flat TVs that followed. See viewing angle
Rear Vs. Front Projection
RPTVs were a fixed size, whereas front projectors can change their screen dimension by changing the external screen and repositioning the unit (see front-projection TV
). See microdisplay
and video/TV history
Rear Screen Vs. Front Screen
Rear-projection systems are self-contained, whereas front-projection systems use a separate screen several feet from the unit.
It All Started With CRT Guns
The first RPTVs used three 7" CRTs to generate red, green and blue light. This 64" set was two feet deep, but a CRT TV that size would have been too costly to build and too big to transport.
Liquid Crystal Microdisplays (MicroLCDs)
Digital Light Processing (DLP)
RPTVs were less bulky when microdisplays replaced the CRTs. Light was beamed through tiny red, green and blue LCD panels approximately 1.5" diagonal, and each one was modulated with the pixel pattern for that color. Lenses enlarged the image. The Liquid Crystal over Silicon (LCoS) method reflected light back to color filters. See LCoS
DLP reflects light from tiny pixel-sized mirrors. Also used in today's front-projection units, the technology uses either a single chip and color wheel (this example) or three chips with their own sets of mirrors and color filters. See DLP