Digital Light Processing
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.
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Mitchell Medford is a popular reviewer of consumer electronics
and technology. He has written for numerous publications and
served as a product development consultant for several consumer
electronics manufacturers. Visit his site or more information on
HDTVs, LCD, and Plasma TVs.