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Bullshit. This applies to very cheap LED's bought from China (or similar). Leading manufacturers like Cree, Lumileds and the rest claim 75% of lumen maintenance after 50'000 hours.

>Besides, LEDs have narrow frequency ranges too, you know.

Actually, I beg to differ. If you look at a Luxeon datasheet (page 9) you will see the spectrum graph. The graph shown does have a peak in the blue, but it has a FWHM of ~30nm, as opposed to ~1-2nm for the peaks from CFLs. In addition to that from ~500nm and up it's very continuous, appearing much like a black body spectrum with a peak ~550nm (T = 5300K).

There's only one question every time. How much light/W does it produce (lm/W)? And what is the price for the 'OLED bulb'.

And... do not compare it to traditional light bulbs. Traditional light bulbs are dead.

Of course, LEDs have achieved a lot in producing more and more light, but currently it is some 10s or 100s fold differends between the price of the
fluorescent light sources and a LED based one, and the fluorescent light source (mostly) produces more light than the LED.

Yes, I hope that OLEDs will be the ones who can reach the barrier, but until that this article is very-very optimistic :)

check
(figure:)
http://europa.eu.int/comm/energy_transport/atlas/h tmlu/lightdintro2.html
articles:
http://europa.eu.int/comm/energy_transport/atlas/h tmlu/lightdintro.html
http://www.lumileds.com/pdfs/TP40_IESNA_July%20200 4_LED_Paper.pdf

The main reasons why White LEDs are still not ready for general purpose lighting are:

Low CRI (Color Rendering Index) that means bad illumination compared to incandescent
Low temperature of operation (120-150C max)

Most electronic design that include hi power LEDs (such as LUXEON http://lumileds.com/) need to take in account hheat transfer.

LEDs are NOT monochromatic... A laser is monochromatic.

http://www.lumileds.com/pdfs/DS45.PDF
See Figure 1a, Page 9.

You'll see that a "Typical" Green Luxeon 3 will output 50% of its peak wavelength's power from ~510 to ~550nm. 20% from 490-560nm. Hardly monochromatic.

If you happen to have a loose LED, power it up in a dark room, take any old CD, and using the diffraction grating on the CD itself look at the spectrum of the LED.

But you do have a point, some objects with colors that reflect mainly in these "holes" in the spectrum may look off.
But if you just want a good "Color Rendering Index (CRI)", use a normal white LED that uses a deep blue die with a phosphor painted on. See Figure 1b on the above link.

But if you want a color washer with a good CRI, you're going to end up using about 10 different wavelegth LEDs.

Like this one.
The three watt variant. Runs on two AA batteries.
It lights up the entire room with a somewhat cold white light. Can be fixed by adding some red and yellow I recon.

Also, looking directly into it is very nasty, but a clear bulb probably does that aswell.

can be viewed here, since the site linked to by the article appears to be /.'ed.

LumiLeds makes the LEDs: red, green, and blue. The bulb life of 20,000 hours is fantastic, but I agree that chances are poor this will throw a bright enough image to be useful in daylight or bright room situations. The Lumileds site suggests that the maximum brightness for a Lumileds Luxeon LED is 120 lumens.

-Joe G.

can be viewed here, since the site linked to by the article appears to be /.'ed.

LumiLeds makes the LEDs: red, green, and blue. The bulb life of 20,000 hours is fantastic, but I agree that chances are poor this will throw a bright enough image to be useful in daylight or bright room situations. The Lumileds site suggests that the maximum brightness for a Lumileds Luxeon LED is 120 lumens.

-Joe G.

lumileds press release

snippet:

When the LED's are driven at their maximum
operating
conditions as indicated in table 2, the total
power generated by the LED's is about 6.5 W. The thermal design turned
out to be insufficient to dissipate this power without
overheating the devices, and the LED's had to be driven at lower
currents to limit the temperature. This resulted in a light output
of the projector of about 15 lm, which was still very comparable to
the brightness of a laptop when illuminating an area of 15"
diagonal. 6. Conclusions
A small RGB LED illuminator for pocket imagers has
been demonstrated, with 40 lm output, resulting in 15
lm out of the projector. Volume of the light engine, including
optics, heat sinks and driver and light-feedback electronics was
around 100 cc.

Something else to keep in mind is that high brightness LEDs do not tolerate much heat and since the light-emitting area of an LED is very small compared to, say, a filament, heat must be pumped away either passively with a heat-sink (much like your CPU) or actively with a thermo-electric cooler (much like some people's CPUs). Here comes the expensive engineering problem.

• Fast turn on/turn off times. No more than 10ms.
• High total brightness, but particularly around the wavelengths 455nm and 615nm.
• Small source size, narrow emission cone since the light must be captured and imaged.

The big guy so far has been Lumileds , e.g. their Luxeon Star is one beast. I think it's now included in the headlight fixtures of some cars. No harm in having more competition, but those luxeon stars really would be tough to beat. Impressive engineering.

I think we're all in agreement here about the hilarious idiocy of aforementioned legislation. However as long as we're here I cannot allow this opportunity to discuss nerdly things go unexploited.

The cell phone LED market is really interesting. You basically have the problem of producing a lot of light very quickly with a very limited amount of power available and an even more limited volume of space to fit your electronics (no room for that big capacitor seen in conventional camera flash drive circuits) to drive the flash since cameras these days are tending ever more toward the positively lilliputian. Many cameras include a simple and cheap Cerium:YAG coated 5mm blue led which can be safely overdriven for a very short amount of time, producing a moderate burst of light. Luxeon, the maker of the current most powerful white LEDs recently entered the market with their much improved version of this method. Certain other companies are trying to miniaturize conventional xenon flash units for use in cell phones. Still other companies are eyeing different methods. The story is, interestingly, somewhat analogous to the development of cell phone electronics themselves, a maximization of efficiency in terms of converting power from the battery to the display, processor and transmitter. Except now it's a game of getting the most photons out of a flash using the fewest electrons to do it.

I thought about this too. Luxeon LEDS are the brightest I know of..

http://www.lumileds.com/products/family.cfm?family Id=9 but I believe overhead projectors require (prefer?) point source light.

even still, to get near the same level of lumens as a conventional bulb, one would need a large number of these stacked.

The cost of these may well offset a "real" projector.

You want "real" LED lights? Try Luxeon Stars....
I'm just waiting for them to come out with UL-approved, white-light fixtures for the home...

> The best white LEDs can produce over 120 lumen/watt; vastly more efficient.

That doesn't sound right. I believe that Lumiled's Luxeon III LEDs have the highest luminous output at 80 lumens at 1000mA maximum flux.

http://www.lumileds.com/ Check out the recent docs, and try one of there 5 watt leds. You can make tree tops light up, no prob.

Any links to places that sell these LED's?

I've been googling, but haven't found anything yet (other than case-mod LED's).

One place to start: The LED Light.com. Fair warning: swallow that mouthful of {beverage} before reading the prices for the 120/240 volt "bulbs", unless you want to review input.

It will be interesting to see how long it takes 'em to start building units using Luxeons.

Also, do you just take these LED's and stick em in your light socket? Is it that easy?

Er, no, unless you count that brief glow as it becomes a friode. Normally you want to supply just enough power to do the job, which means you have to modify that 120/240V feed down to something the diodes can handle without smoking.

Actually there is a company producing a flat screen with lets call them nearly real color pixels. Rather than using filters in the panel they use extremely bright Red, Blue, and Green color LED's in the backlight. The image is then represented in a field seqntial fashion. The beauty is that each individual pixel is representing the full color, so you dont need silly and stupid gimmicks like cleartype.

Here's the link if anyone is interested:
LumiLeds

I think you would need a minimum of 50 LEDs.

LumiLeds Lighting Produces 17 Lumen White LED

But projector bulbs seem to start at around 1000 lumens and some projectors go up to 5000