Edmund fights the etendue battle

January 27, 2006, Barrington, NJ--In the interests of better capturing light from LEDs, Edmund Optics has introduced its EOS illumination-delivery system, which, according to the company's president, John Stack, can channel the captured LED light through an aperture at an efficiency that reaches the limits of what physics allow.

January 27, 2006, Barrington, NJ--In the interests of better capturing light from LEDs, Edmund Optics has introduced its EOS illumination-delivery system, which, according to the company's president, John Stack, can channel the captured LED light through an aperture at an efficiency that reaches the limits of what physics allow.

The EOS system was introduced at Photonics West (January 21-27, 2006; San Jose, CA) by Stack and others, who unveiled a working EOS illuminator at the Edmund booth. Because the company is pursuing patents on the technology, no one at Edmund was willing to discuss the technological details of the EOS system.

Etendue is a characteristic of a light source that describes its "concentratedness"; for example, if an emitter has a small etendue, its light can be funneled (by an optical system) through a smaller aperture at a smaller numerical aperture than can light from a source having a large etendue. In common-sense terms, light from a large object emitting in all directions cannot be concentrated by optics so that all the light passes through a tiny hole.

Etendue is a function of the area of an emitting source and the solid angle into which it emits, and in some simple cases can be determined by multiplying the area of the source by the solid angle of its light cone. The etendue of many real-life systems, however can only be accurately found by computer modeling.

According to Stack and others at Edmund, the EOS system can capture light from LEDs (which have nonuniform angular emission and sometimes nonuniform brightness across the emission area) and channel it through an aperture at the highest efficiency possible. The light from various sources, including LEDs and OLEDs, and at wavelengths from the UV to the IR, can be combined in this way.

The EOS technology will create new opportunities for the use of LEDs in automotive headlamps, scientific-instrument lighting, IR military illuminators, surgical headlamps, and portable projector systems, to name a few, say those at Edmund.

"150-W quartz-halogen bulbs typically last 1,000 hours," said Chris Cummings, an R&D engineer at Edmund Optics. "Initial testing results indicate that with the new optical design, the EOS-transformed LED will be at least 2-5x brighter than quartz-halogen, lasting 20-50x longer."

While LEDs deliver a longer illumination lifetime and are more energy-efficient than quartz-halogen, they have never delivered the brightness of quartz-halogen; as a result, quartz-halogen continues to dominate many applications in illumination and lighting, such as manufacturing, medical, military, and machine vision. To reach higher brightnesses, end users persist in driving the LED chips harder, increasing power to achieve a better result. Unfortunately, this method decreases the lifetime of the LEDs, reducing of its primary advantages over quartz-halogen.

The first product to use this technology is an Edmund Optics' designed LED fiberoptic illuminator for the industrial vision market available in the second quarter of 2006, noted Samuel Sadoulet, Edmund's director of product development. The company is also working on licensing agreements for use of EOS in a broad range of industries.

More in Lasers & Sources