21st November, 2008
LED Projectors: When, Who, And Why?
Brent Butterworth
An off-site demo at September’s CEDIA Expo marked the debut of a technology that will change front projection more than anything since the DLP chip. The consensus among projection experts is that this technology—LED-driven projection—will eventually become a common fixture in home theaters and board rooms. The big question is: When?
First, a quick recap of LED’s advantages. In an LED projector, super-bright LEDs replace the high-pressure mercury lamp used in today’s conventional projectors. LEDs last far longer than bulbs; the PhlatLight LEDs used in some rear-projection TVs are rated to run 8 hours a day for more than 20 years. The lamps used in projectors today last 2,000 to 4,000 hours—and for the last quarter or so of their life, they become annoyingly dim. Replacement cost for these lamps is high, ranging from about $200 to more than $1,000. They also consume more energy than LEDs.
LED also offers the potential for picture quality improvements. LEDs can be dimmed quickly—on a frame-by-frame basis—so they can be adjusted to deliver the deepest blacks and optimum contrast for each shot in a video. Lamps respond too slowly to do this, although a similar if less profound effect can be achieved with an automatic iris. LEDs offer a wider color gamut than conventional lamps, and they come on almost instantly—there’s practically no warm-up time.
Chi Lin Technologies, the manufacturer that conducted the CEDIA Expo demo, gave us an update on the prospects for LED projection in 2009. Product manager Julian Chu said he expects the company to enter mass production in Q2 or Q3 of 2009, and confided that it already has at least one company signed up to distribute the projector in the U.S. (Chi Lin does not sell projectors under its own name in the U.S.—it makes them for other companies.)
Chu said that the company has completed a 2nd generation model which is more advanced than the one shown at the CEDIA Expo. He said the new unit is about 40% smaller and significantly brighter. Chi Lin’s specifications for the projector include a 100,000:1 contrast ratio and a color gamut 28% broader than the NTSC standard. The projector uses a liquid cooling system, which is necessary because the LEDs run at a very high current of 30 amps in order to achieve the necessary brightness. The prototype at the CEDIA Expo had a cooling fan that was vacuum-cleaner loud; no word on whether or not Chi Lin has improved that, but they’ll have to if they want into the home theater market.
Most companies that market projectors in the U.S. are keeping their plans for LED to themselves. However, Brian Carskadon, director of product management for Runco International, was willing to elaborate on LED’s future. He predicted we’ll see introductions of several LED-driven front projectors in 2009. He also predicted—not surprisingly—that the first ones will be expensive and noisy compared with their lamp-driven counterparts. He expects lower-priced, lower-performing models aimed at the casual market to appear toward the end of 2009.
And, most importantly, Carskadon expects LED to someday dominate the projection market. He said that once LED products reach performance parity with typical lamp-driven projectors (possibly as soon as two years from now), lamp-based products will be relegated to applications that require high brightness, such as extra-large home theaters.
For the integrator, LED has one big upside and one big downside. Of course, it will lead to more reliable installations and fewer service calls. But it’ll also give you fewer chances to interface with your clients.
Posted at 12:14 am |
On November 21, 2008 at 2:43 pm Cliff Plavin said:
November 21, 2008 at 2:43 pm
Brent,
There are a few major hurdles for LED lamp based displays to overcome before they will gain mainstream acceptance. LED’s are very succeptable to changes in both temperature and voltage which cause the color of the lamp to shift dramatically. Being able to get LED’s which are binned to tolerances that are close enough to use in a high quality projector application is also very difficult at this time. Lastly, control over the LED’s light output to achieve proper colorimetry is extremly difficult for manufacturers to achieve as this is completely foreign territory for them and new methodologies need to be developed for calibration.
Have you seen demonstrations of this technolgy where the manufacturer was able to provide an image which was calibrated to a very high standard? If so how long can the display maintain this calibration? As the LED degrades over a short period of time does the color change or is it able to maintain the same color temperature for the life of the lamp assembly? If a group of LED’s are used the ability to control each of them to maintain flat filed uniformity is also an issue.
Is the contrast ratio of 100,000:1 with a dynamic Black or Static meaning that the use of local area dimming of the LED’s to create a darker image (which is essentially the same as if using an iris in other projector technologies) does not really provide a true contrast value for measurement. It is considerably different from full on/full off or even inter field measurement of a “0″ Black and “100″ White in the same field.
Demonstrations of local area dimmed LCD flat panels were also shown at CES last year and the performance was hardly compelling enough for one to want to run out and purchase one at this time. What do the manufacturers expect the display to require for voltage consumption for such a high light output display given that it also employs an elaborate cooling system? They should probbably contact Richard Dyson on the cooling system!
On November 28, 2008 at 12:30 pm Brent Butterworth said:
November 28, 2008 at 12:30 pm
The Chi Lin demo is the only one I’ve seen of home LED projection. (I’ve seen LED-driven “pocket projectors,” but that doesn’t count.) I can’t say how well calibrated it was; they didn’t show test patterns and there wasn’t any test gear available. The picture looked just OK - but of course it was a prototype. It certainly looked a lot better than DLP pictures circa 1995.
That projector used global dimming, not local, so it is more analogous to an iris than to the LED backlit LCD flat-panels from Samsung, Sony, etc.
I’m glad you brought up all those technical points, because they do seem significant. Now we have the viewpoint of two companies (Runco and Projection Design) so the article is a lot stronger! However, never having had the pleasure (?) of designing a projector, I can’t address your points.
I’ll conclude by saying that the PhlatLight LEDs driving the RPTVs from NuVision and Samsung performed spectacularly. And LEDs used in bicycle lights have made incredible leaps in performance in the last two years. (See http://www.dinottelighting.com.) So I’m bullish on LED front projection.
I’ll confess I’m biased. I have always thought high-pressure mercury lamps are expensive and mediocre. I hate having to spend the money to replace my projector’s bulb, and I hate the way it looks after ~1500 hours. I know it’s all we got right now, but it seems obvious to me that the bell is tolling for the bulb.