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How does DLP TV work?
DLP technology is based on an optical semiconductor called a Digital Micromirror Device (DMD) which was invented in 1987 by Texas Instruments. The DMD is basically an extremely precise light switch that enables light to be modulated digitally via millions of microscopic mirrors arranged in a rectangular array. Each mirror corresponds to one pixel of the finished picture. The aluminum mirrors are sixteen microns square, are spaced less than 1 micron apart, and weigh only a few millionths of a gram. The entire DMD is so tiny, you could hold it in the palm of your hand.
Each of these mirrors is attached to a yoke and a hinge that can move it to an “on” or “off” position. These mirrors are literally capable of switching on and off thousands of times per second and are used to project light towards, or away from, a dedicated pixel space on a screen. The duration of the on/off timing determines the level of gray seen in the pixel. Current DMD chips can produce up to 1024 shades of gray.
By integrating this grayscale capability with a 6-panel color wheel (2x RGB), the DLP system is able to produce more than 16 million colors. A DMD system can be made up of a single chip or 3 chips, the latter resulting in even greater color reproduction. Some movie-theaters now use 3-chip DLP projectors. These systems can reproduce over 35 trillion colors.
Advances are being made in the single-DMD design. For example, Texas Instruments’ new HD2+ design incorporates an additional color (dark green) into the color wheel, allowing for contrast ratios greater than 3000:1 for much improved color reproduction and contrast. In late 2004, xHD3 technology was introduced, helping to eliminate stray light and unnatural image-brightness by adding a new rear coating to the mirrors. Also, a soon-to-be-introduced technology called Sequential Color Recapture (SCR) will replace the traditional DLP color wheel with what is essentially a “Spiral of Archimedes” RGB color pattern. This new technology has been mathematically projected to rival the current quality of 3-modulator DLP Cinema systems.
Currently, a DMD can support a maximum of 1,280 by 720 pixels. Because some high-definition images require 1,920 by 1,080 pixels, Hewlett-Packard has developed a technique called wobulation, which allows each mirror to create two of the image’s pixels, improving the resolution. This technology should be available to consumers in late 2006. Technological limitations and cost-issues have so far prevented manufacturers from increasing DLP’s pixel-count through other methods, such as increasing the number of mirrors on the DMD.
Right now, DLP is the front-runner in the technology war and is pretty much cleaning the clock of the likes of CRT and LCD rear-projection.
DLP Advantages:
* Incredible color reproduction
* Excellent contrast ratios (using HD2+)
* Lightweight
* Excellent lamp life
* Fully digital displays supporting DVI/HDMI without analogue conversion
DLP Disadvantages:
* Requires a minimum of 12-14” depth for lamp-based technology
* Older models (pre-HD2) may not perform as well as upper-scale CRT projection systems
* Potential for “Rainbow Effect” in older and single chip systems.
Glossary of Terms
- Anamorphic
- Process that condenses the image in the source material to be expanded by the display device. With DVD, the anamorphic recording preserves a vertical detail that would otherwise be lost on a widescreen film that is cropped, or letterboxed, to fit the 4:3 reading image space.
- Ohm
- A measure of how much something resists (impedes) the flow of electricity. Larger numbers mean more resistance.
- Preamplifier
- A control and switching component that may include equalization functions. The preamp comes in the signal chain before the amplifiers.
- Spider
- The part of the loudspeaker that holds the diaphragm in place, and allows it to move when activated. Also called suspension.
- Woofer
- A speaker driver designed to reproduce low frequencies.
