The remaining heir to the rear-projection television option still manufactured and sold today is the DLP (Digital Light Processing) rear-projection television. Like LCD, the actual image is displayed on a chip, however, the chip used in a DLP projection television is different. The chip in a DLP projection television is referred to as a DMD (Digital Micromirror Device). In essence, every pixel on a DMD chip is a reflective mirror.
The video image is displayed on the DMD chip. The micromirrors on the chip (remember: each micromirror represents one pixel) then tilt very rapidly as the image changes. This process produces the grayscale foundation for the image. Then, color is added as light passes through a high-speed color wheel and is reflected off of the micromirrors on the DLP chip as they rapidly tilt towards or away from the light source. The degree of tilt of each micromirror coupled with the rapidly spinning color wheel determines the color structure of the projected image. As the amplified light bounces off the micromirrors, it is sent through the lens, reflected off a large single mirror, and onto the screen. For further technical explanations, click on the DLP resource link on the upper right sidebar of this page.
Advantages Of DLP Video Projection
1. DLP projection technology is suitable for not only for projection televisions, designed for home use, but DLP technology is also in use in some movie theaters for feature film projection. Essentially, the films are digitally converted and stored to either to a hard drive or optical disc (similar to DVD - only in High Definition), then fed into the DLP projector and projected onto the movie screen. The high resolution DLP chips made for this application render an image that is almost as good as 35 or 70mm film, without all those film scratches!
2. Other advantages of the DLP projection technology include excellent color accuracy, no "screen door" effect (as with LCD), due to its micro-mirror construction, compactness, low power consumption, and high contrast and brightness (although typically not as bright as LCD types but much "smoother" looking). Also, DLP technology enables a very thin depth cabinet profile, just like LCD rear-projection sets.
Limitations Of DLP Video Projection
1. Just as with LCD, each DLP chip has a finite number of pixels.
2. Although a DLP rear-projection television doesn't exhibit the "screen door" effect of many LCD-based units, a DLP rear-projection television can exhibit what is referred to as "the rainbow effect". Basically, the "rainbow effect" is exhibited by a brief flash of colors (like a small rainbow) when the viewer rapidly looks from side to side on the screen or looks rapidly from the screen to side of the room. Fortunately, this does not occur frequently and many people do not have sensitivity to this effect at all.
3. Another limitation of DLP is that the DLP chip is lit up by another light source, just as with a film or video projector. This means that a DLP projection television will need periodic replacement of its light source (a high wattage light bulb) after a specified period (usually 2,000 to 5,000 viewing hours, depending on the set). The cost for replacement bulbs can range from $200 or more. Recent advances in technology, such as LED and Laser light sources are eliminating this issue on some high-end sets. If you have the budget, you might consider DLP sets that feature LED or Laser light sources.
Although DLP isn't perfect, the DLP projection television has become an option for those that want the largest screen size possible for the lest amount of cost, when compared to both LCD and Plasma televisions, and, without going to the full front video projector route.
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