Component Channels LED Light

LEDs are more energy-efficient than light bulbs, but fall short when it comes to light output. But a new optical component could change that by concentrating LED light like a spotlight and directing it precisely where needed.

A 1-W LED delivers roughly the same optical output as a 100-W light bulb, making the LED more energy efficient. But the tiny light sources are not currently the preferred means of illumination when a high light output is required. Researchers at the Fraunhofer Institute for Production Technology (IPT) in Aachen have developed an optical component that can concentrate the light like a spotlight. When used in a a desk lamp, for example, the light can be channeled so that only a spot about the size of a sheet of paper (DIN-A4-sized) in the middle of the table is brightly and evenly lit, while everything else stays in the dark.

“A light-emitting diode is a single-point light source that emits light in a large, uncontrolled area,” said Christian Wenzel, PhD, head of department at the Fraunhofer Institute for Production Technology (IPT) in Aachen. “We use special lenses to direct all of the light to the place where it is needed, thus increasing the efficiency of the LEDs. The spot of light created by the light source does not therefore fade out at the edges, but has a sharply defined edge.”

This channeling of light is based on a free-form system of optics -- a plastic lens whose geometry can be shaped as needed, the researchers said, with the lens manufactured at the institute.

“The lenses are cast using an injection-molding technique. The two halves of the tool that serve as a mold have to be aligned with extreme precision just once -- they have an accuracy of a few microns, or less than a tenth of the diameter of a hair. Once the tools have been tared, the lens can be manufactured in large batches at low cost,” said Wenzel.

One challenge that had to be overcome was the fact that the plastic, which is inserted into the mold hot, shrinks as it cools, making the finished lenses slightly smaller than when molded. The researchers take this into account by repeated, gradual improvements, to an accuracy of a few microns. When the lenses are finished, the scientists check them by projecting a pattern of stripes onto the lens. The distortion of the stripes reveals the lens curvature, inclination and shape.

The Fraunhofer IPT researchers will demonstrate the entire process, along with optical systems for practical applications, at the Optatec trade fair in Frankfurt, Germany, June 17-20 (Hall 3, Stand D53).

For more information, visit: www.ipt.fraunhofer.de/EN/