Digital Light Processing
By Mitchell Medford
In essence, DLP is a nanotechnology implementation of the old survival technique of using a mirror to signal for help -- its purpose is to shine a controlled series of light flashes on a target to send a message. The mirror in this case is part of an optical semiconductor called a digital micro mirror device, or DMD. The DMD chip contains not one but an entire array of up to 2.1 million microscopic mirrors, each just 16
micrometers square (less than one-fifth the size of a human hair) and 1 micrometer apart!
The DMD (Digital Micromirror Device) chip was invented in 1987 by TI scientist Larry Hornbeck, who had been exploring the manipulation of reflected light since 1977. In 1992, TI started a project to explore the DMD's commercial viability. A year later, it named the new technology DLP and formed a separate group, now called the DLP (Digital Light Processing) Products division, to develop commercial display applications.
The DMD chip is driven by a digital video or graphic signal in which each digital pixel corresponds to a single mirror on the DMD. Add a light source and a projection lens, and the mirrors can reflect a digital image onto a viewing screen or other surface. Each mirror is mounted on tiny hinges, so it can be tilted
12 degrees toward or away from the light source, creating a light or dark pixel on the projection surface.
DLP (Digital Light Processing) technology utilizes a small digital micro mirror
device (DMD) to tilt micro mirrors less
than the size of a human hair in width toward or away from a white lamp inside the DLP television. This process creates a light or dark pixel on the face of the projection screen, depending on how much light is reflected by the mirror.
Each mirror can turn on or off several thousands of times per second, so this technology can reproduce 1024 shades of gray. There are four main components in the system: the DMD chip, the color wheel, the light source, and the optics. Light from the lamp passes through a color wheel filter and into the DMD chip, which will switch its mirrors on or off in relation to the color reflecting off them, producing an image.
DLP-based projection displays are well-suited to high-brightness and high-resolution applications: (a) the digital light switch is reflective and has a high fill factor,resulting in high optical efficiency at the pixel level and low pixelation effects in the projected image; (b) as the resolution and size of
the DMD increase, the overall system optical efficiency grows because of higher lamp-coupling efficiency; (c) because the DMD operates with conventional CMOS voltage levels (~5volts), integrated row and column drivers are readily employed to minimize the complexity and cost impact of scaling to higher resolutions; (d) because the DMD is a reflective technology, the DMD chip can be effectively cooled through the chip substrate, thus facilitating the use of high-power projection lamps without thermal degradation of the DMD; and(e) finally, DLP-based systems are all-digital (digital video in, digital light out), so reproduction of the original video source material is accurate and the image
quality is stable with time.
A Note on Methodology: Size is the most relevant attribute to investigate when evaluating the picture quality of DLP
televisions. Today, DLP displays can be purchased in sizes ranging from 43" to 65" on the diagonal. When compared with LCD large LCD TV cannot reproduce black levels remotely close those of a smaller LCD TV. Therefore, when comparing units of similar size, the DLP set will display richer black levels.
Color saturation is the absence of gray in color. The less gray, the more saturated the color is said to be. The method with which color is rendered differs for each technology. The DLP television's color accuracy is heavily dependent on the color wheel filters for single chip designs. Since the color wheel has
fixed color filters (red, green, and blue), color adjustment is limited on these single chip designs.
Big Screen TVs are more popular than ever. The days of projection sets that took up half the living room with bulky cabinets, only viewable in total darkness, with everyone crowded around
the center of the screen, and high prices are
gone. Today's big screens TV's are brighter, slimmer, viewable from the same angles as their Tube counterparts, and with prices for entry-level sets around $1,500, they have become more
affordable than ever.
About the Author
Mitchell Medford is a popular reviewer of consumer electronics and has served as a product development consultant for several consumer electronics manufacturers. Visit his site or more information hi-tech television: http://www.newtechnologytv.com
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