Video Projector - Projection Technologies

Projection Technologies

• CRT projector using cathode ray tubes. This typically involves a blue, a green, and a red tube. This is the oldest system still in regular use, but falling out of favor largely because of the bulky cabinet. However, it does provide the largest screen size for a given cost. This also covers three tube home models, which, while bulky, can be moved (but then usually require complex picture adjustments to get the three images to line up correctly).
• LCD projector using LCD light gates. This is the simplest system, making it one of the most common and affordable for home theaters and business use. Its most common problem is a visible “screen door” or pixelation effect, although recent advances have reduced the severity of this effect.
• DLP projector using Texas Instruments’ DLP technology. This uses one, two, or three microfabricated light valves called digital micromirror devices (DMDs). The single- and double-DMD versions use rotating color wheels in time with the mirror refreshes to modulate color. The most common problem with the single- or two-DMD varieties is a visible “rainbow” which some people perceive when moving their eyes. More recent projectors with higher speed (2x or 4x) and otherwise optimised color wheels have lessened this effect. Systems with 3 DMDs never have this problem, as they display each primary color simultaneously.
• LCoS projector using Liquid crystal on silicon.
  • D-ILA JVC’s Direct-drive Image Light Amplifier based on LCoS technology.
  • SXRD Sony’s proprietary variant of LCoS technology.
• LED projectors use one of the above mentioned technologies for image creation, with a difference that they use an array of Light Emitting Diodes as the light source, negating the need for lamp replacement.
• Hybrid LED and Laser diode system developed by Casio. Uses a combination of Light Emitting Diodes and 445 nm laser diodes as the light source, while image is processed with DLP (DMD) chip.
• Laser diode projectors have been developed by Microvision and Aaxa Technologies. Microvision laser projectors use Microvision's patented laser beam-steering technology, whereas Aaxa Technologies uses laser diodes + LCoS.