LED sources gaining power

[visualove]

The NYT reports some new LED illumination sources, a bit expensive, for now...


"As light-emitting diodes move toward the brightness of incandescent light bulbs, they are developing heat buildup, a problem that has long plagued their well-established rival.

But this week, Lamina Ceramics will introduce an L.E.D. array with heat-reduction technology that allows it to be as bright as a theatrical light without risking an electronic meltdown.

The light engine, as Lamina calls its disk-shaped product, is based around a new generation of high-powered light-emitting diodes developed by other companies. Lumina's array lacks the efficiency of the best traditional light sources and, with a price tag in the thousands of dollars, is also vastly more expensive.

By Lamina's measurements, the disk, which is about five inches in diameter and uses hundreds of L.E.D.'s, produces 13,300 lumens of light. The company says this is about 10 times the brightness of any solid-state light previously demonstrated. The large metal-halide fixtures commonly used to light grocery stores, by comparison, generally emit 10,000 to 20,000 lumens.

But that brightness means each of the high-output diodes, which typically measure 1 millimeter in diameter, also have a power requirement of 1 to 5 watts.

"One watt can get very hot if you don't put it on a heat sink," Mr. Adair said. Of course, in an array with hundreds of light-emitting diodes, the heat problem is all the greater.

The most common solution for preventing heat problems is to bundle one to three light-emitting diodes in a plastic, metal and silicon package, known as a heat sink, that dissipates their heat. But the size of those heat sinks means that any array made up of encapsulated L.E.D.'s quickly becomes excessively large for practical applications.

Rather than packaging a few diodes into separate heat sinks, Lumina can bond hundreds of them to a single large heat sink that uses fused layers of metal and ceramic to carry the unwanted energy safely away. That allows Lumina to squeeze more diodes, and thus more light, into every square inch of an array.

One drawback, which engineers say can be reduced with further improvements in L.E.D.'s, is the array's poor energy efficiency. It requires 860 watts of energy. By comparison, metal-halide lights in stores producing a comparable brightness use 150 to 200 watts of power, Dr. Narendran said. The conventional bulbs, however, are much larger and emit an unpleasant blue-tinged light.

Then there is the price, which Mr. Adair said is largely determined by the cost of high-output L.E.D.'s. Lamina plans to sell its arrays to other companies that manufacture lamps. A single Lumina disk will cost about $4,900, although there are substantial discounts for large orders.

For that reason, Lamina's first array is made up of red, green and blue L.E.D.'s, allowing it to change instantly among any of 16 million different color possibilities. The company hopes that ability and its compactness will generate a following in theatrical lighting where unusual light fixtures commonly sell for thousands of dollars.

Although Lamina's creation is unusually large and bright, it is not the only array that offers a high density of L.E.D.'s. This month, Lumileds Lighting, a maker of high-output L.E.D.'s based in San Jose, Calif., introduced a technology that reduces heat problems by combining diodes that have improved thermal efficiency with a metallic heat sink. It is being marketed as a tiny 40-lumen flash for cellphone cameras.