Rear-projection television

Mid 2000s RPTV with HDTV tuner and YPbPr input as well as DVI (digital) video inputs.

Rear-projection television (RPTV) is a type of large-screen television display technology. Until approximately 2006, most of the relatively affordable consumer large screen TVs up to 100 in (250 cm) used rear-projection technology. A variation is a video projector, using similar technology, which projects onto a screen.

Three types of projection systems are used in projection TVs. CRT rear-projection TVs were the earliest, and while they were the first to exceed 40", they were also bulky and the picture was unclear at close range. Newer technologies include: DLP (reflective micromirror chip), LCD projectors, Laser TV and LCoS. They are capable of 1080p resolution, and examples include Sony's SXRD (Silicon X-tal Reflective Display), JVC's D-ILA (Digital Direct Drive Image Light Amplifier), and MicroDisplay Corporation's Liquid Fidelity.


Modern rear-projection television has been commercially available since the 1970s, but at that time could not match the image sharpness of a direct-view CRT. Current models are vastly improved, and offer a cost-effective HDTV large-screen display. While still thicker than LCD and plasma flat panels, modern rear-projection TVs have a smaller footprint than their predecessors. The latest models are light enough to be wall-mounted.[1]

Early 2000s CRT projection TV with 1080i HD ready capabilities has an RCA line level input for use of internal speakers as a center channel in a surround sound system.

However, the projection technique is much older than this. Projection systems were used in the very early 1950s when it was still impossible to manufacture CRTs with a screen size much over 12 inches. Utilising a 2-inch monochrome CRT driven at a very high accelerating voltage for the size (typically 25 kV), the tube produced an extremely bright picture which was projected via a schmidt lens and mirror assembly onto a semi translucent screen of typically 17 to 19 inches in size. The resultant picture was darker than with a direct view CRT and had to be watched in subdued lighting. The degree to which the tube was driven meant that the tube had a relatively short life. Details of a specific TV set with its optical system can be found here.

Given their already large dimensions, projection TVs sometimes included larger speakers and more powerful built-in audio vs direct view CRTs and especially depth-limited flat panels, as well as basic surround sound processing or emulators such as Sound Retrieval System (SRS) by SRS Labs, similar to a sound bar.


All analog, "full screen" 45-inch Zenith CRT rear-projection TV from the 1990s.

In 1884, Paul Nipkow developed an image sending device that spun a metal disk which sent images through a collection of wires. This was later named the Nipkow Disk. This device had 18 lines of resolution.[2] In 1907, A.A. Campbell-Swinton, an Englishman, and Boris Rosing, a Russian scientist, developed a cathode ray tube to work in conjunction with a device similar to a Nipkow Disk and created one of the first working mechanical television systems.[3] They were not credited with the sole intention of the television being that a single inventor did not invent the television. While popular in the early 2000s as an alternative to more expensive LCD and plasma flat panels, the falling price and improvements to LCDs have led to Sony, Philips, Toshiba and Hitachi planning to drop rear-projection TVs from their lineup.[4][5] Currently, Samsung, Mitsubishi, ProScan, RCA, Panasonic and JVC remain in the market. The bulk of earlier rear-projection TVs meant that they cannot be wall-mounted, and while most consumers of flat-panels do not hang up their sets, the ability to do so is considered a key selling point.[6] On June 6, 2007, Sony did unveil a 70" rear-projection SXRD model KDS-Z70XBR5 that was 40% slimmer than its predecessor and weighed 200 lbs, which was somewhat wall-mountable. However, on December 27, 2007, Sony decided to exit the RPTV market.[7][8][9] Mitsubishi began offering their LaserVue line of wall mountable rear-projection TVs in 2009.[10]

Types of rear-projection technologies

A thinner and lighter LCD or DLP projection TV in a home cinema.

A projection television uses a projector to create a small image or video from a video signal and magnify this image onto a viewable screen. The projector uses a bright beam of light and a lens system to project the image to a much larger size. A front-projection television uses a projector that is separate from the screen and the projector is placed in front of the screen. The setup of a rear-projection television is in some ways similar to that of a traditional television. The projector is contained inside the television box and projects the image from behind the screen.

The following are different types of projection televisions, which differ based on the type of projector and how the image (before projection) is created:

See also


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