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Q1 : What is a DLP projector?
A self-contained projector alternative to LCD technology using Texas Instruments DLP™ technology. DLP (Digital Light Processing™) typcially uses a single self-contained digital display chip, actually called a Digital Micromirror Device (DMD). The device contains millions of microscopic tilting mirrors that are tilted to either reflect light, or not, depending on the video signal. This complex, but ingenious device, actually only produces images in black and white, but a high speed rotating color wheel is introduced into the light path to transform the image into color. In contrast to LCD, the light does not pass through the DMD device, it is reflected by all these tiny mirrors. DLP projectors offer the same advantages over CRT as does LCD projection, while allowing lower power lamps to provide brighter, higher contrast images, but also introduces a mechanical device, the color wheel motor.
Q2 : What is keystoning?
Keystoning is when the image you are projecting appears wider at the top or bottom as a result of the projector being positioned somewhere other than the center of the screen. Many projectors allow you to adjust keystoning and some offer fixed keystone factor (allows you to place the projector at about 8 degree angle lower or higher than the center of the screen).
Q3 : What are the weaknesses of DLP projectors?
Rainbow Effect
Q4 : Waht are the advantages of DLP projectors?
small package size
smooth, high contrast video
reduced pixelation
Q5 : What is the the DLP Rainbow effect?
This visual artifact is best described as brief flashes of perceived red, blue, and green 'shadows' observed most often when the projected content features bright/white objects on a mostly dark/black background (the scrolling end credits of many movies are a common example). Some people perceive these rainbow artifacts all of the time, while others say they only see them when they let their eyes pan across the image. Yet others do not notice the artifact at all. The effect is likely rooted in the concept of the flicker fusion threshold.
The "Rainbow Effect" is unique to single-chip DLP projectors. As described above, only one color is actually displayed at any given moment. As the eye moves across the projected image, these separate colors become visible, resulting in a perceived "rainbow". The manufacturers of single-chip DLP projection systems have used color wheels rotating at higher speeds, or with more color segments, in order to minimize the appearance of the artifacts. These are referred to as 2x, 3x or 4x wheels. For example, a six segment wheel(RGBRGB) rotating at two revolutions per frame would be a 4x wheel.
Another way to reduce the rainbow effect is to replace a segmented wheel with a wheel whose colors are in an Archimedean spiral. This forms bands of color that move down (or up) the screen. With segmented wheels, the DMD must "go black" while the wheel transitions from one color to another. Not only can this interfere with persistence of vision and thus accentuate the rainbow effect, it means that the more segments there are, the darker the display will be, all else being equal. With a spiral wheel, the mirrors can display more than one color at a time, each moving down (or up) as the wheel turns.
The LED light packs now being introduced in DLP projectors may eliminate rainbow effect for all but a few very sensitive viewers thanks to their high switching frequency and a complete lack of "black" segments as described above. Additionally, the LED pack can display any color of light at any intensity, a capability which, if exploited, provides the potential for increased color gamut and improved contrast compared to displays employing color wheels with fixed-color segments.
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