| Video Noise June 2006
Video Display News
I’ve been critical of DLP and LCD video
displays in the past, and a little less critical of LCoS technology (aka SXRD and D-ILA),
but all of them have one thing in common: their light sources are very bright, very hot,
relatively short-lived lamps that typically sell for more than $200 USD, and often for
$400 to $500. Manufacturers claim lamp life expectancies of from 2000 to 8000 hours, but
that’s under ideal conditions. In the real world, the life of a typical lamp might be
only half as long as the manufacturer’s claim. If you watch three hours a day for a
year, that’s a bit over 1000 hours -- you could end up needing a new lamp every 1 to
2.5 years. It can be an expensive pain.
And if you live in an area where the power goes down with
any frequency, a power failure while viewing your projection device is inevitable. When
that happens, the cooling fan stops immediately, shortening the life of your expensive
lamp by hundreds of hours. At least one company, APC, has addressed this in a home-theater
power conditioner with a built-in, uninterruptible power supply. If the power goes off,
the conditioner’s internal battery can generate 120VAC long enough for your display
to complete its normal shutdown cycle and thus maximize the life of the lamp.
Then there’s the rotating color wheel. In an attempt
to make new video displays more affordable, some manufacturers have removed two DLP chips
or two LCD panels and added a fast-spinning color wheel so that now only one LCD,
LCoS, or DLP panel is needed. Different colors are produced by putting the white light
through a spinning color wheel. When red light hits the display device, red-pixel
information is displayed, then green, then blue, and then the cycle repeats. The only
problem is that when most people scan their eyes across such a display, they see rainbows.
To get rid of this "rainbow effect," manufacturers doubled the speed of the
color wheel, made six- instead of three-color panels, and every other trick they could
think of. Nothing worked.
Now there’s a new light-source technology that solves
the problems of expensive, hot lamps and rainbows, and in some cases might expand the
range of colors an LCD or LCoS panel can display (another serious criticism of those
technologies): super-bright, cool-running, very long-lived, pure-color LEDs. A trio of LED
panels -- red, green, and blue -- can be switched on and off at very high speeds to
produce great-looking images. If you want to expand the range of colors the display can
reproduce, you can add LED panels of slightly different colors. These use sophisticated
color-space mapping when using more than four, five, six or more panels to improve the
range of colors LEDs can display. These new LEDs, which are already appearing in some of
the newer video displays, are claimed to last for at least 20,000 hours -- a huge
improvement over projection lamps. This claim might actually be more than the usual hype;
they do seem to be lasting this long in other applications.
Besides the longer life and elimination of the color wheel,
the LED light sources also eliminate the cooling-fan noise common to every DLP, LCoS, or
LCD video display. If cooling is still needed, a whisper fan will provide enough
convection.
With this new light source, three-panel and three-chip
video displays may no longer be needed, nor the precision alignment they require to
produce perfect images. A single chip doesn’t need to be aligned.
A dream comes true
I’ve said more than once that the best video display
would probably use lasers. Lasers for video displays are relatively cool in operation, and
their useful lifetimes are getting reasonable. Blue, the newest laser color, has the
shortest lifespan, but there are strong signs of improvement. Recently, Mitsubishi has
been showing a working prototype of a laser-based video display. It has many advantages
and potentials: blacks even blacker than those of CRTs; potentially very bright whites;
incredible focus; extremely high scanning speeds; resolution that can be fully scaled to
any native resolution by changing the pixel size to match the source’s resolution
(vs. fixed-pixel displays); the potential to far exceed the high-definition resolution
standard of 1920x1080 pixels; the potential to be the new gold standard of theatrical
projection systems because its ultra-high resolution can eliminate the visible aliasing of
current digital projection systems; and self-contained 60" rear-projection sets that
can be as shallow as 10".
Just when you thought things were starting to settle down
in the video display arena . . .
...Doug Blackburn
db@hometheatersound.com |
