For the past 40 years, light-emitting diodes have been successfully employed wherever small amounts of light are needed. Present-day applications include car indicators, reversing and brake lights. However, the efficiency and luminosity of LEDs have never yet been sufficient to achieve a major breakthrough.
Thanks to new technologies for chip manufacturing, structural design and beam shaping developed by scientists at OSRAM Opto Semiconductors the light output of LEDs has been vastly improved. In Berlin on December 6, President Horst Köhler presented the team of OSRAM and Fraunhofer researchers with the prestigious German President’s award for technology and innovation, worth 250,000 euros, in recognition of their achievement.
The new high-output LED modules are based on perfect synergy between solid-state physics and optics. The semiconductor components were built by OSRAM Semiconductors, while researchers in Jena took care of the optics. OSRAM started developing thin-film LEDs in 1999. The company took a major step forwards when it devised chip technology that permits the extraction of light in a single half sphere.
A novel platform for the thin-film LEDs ensures efficient temperature management and allows all colors of LEDs to be combined. To use the light emitted by the LED chip as fully as possible, a special optic for the respective application is required and was accordingly designed and implemented by the Fraunhofer researchers.
It consists of two parts: a primary and a secondary lens. The primary lens collects the light emitted by the LED close to the chip and combines it to form a beam. The secondary lens homogenizes the light beam.
LED modules of this kind are already in use in various products, such as battery-powered digital projectors. The number of applications is steadily growing. Besides miniature projectors there will soon be LED-based rear-projection TV, infrared LED light sources for purposes such as pedestrian monitoring systems in cars, and the “OSTAR Lighting” LED module for general illumination. OSTAR modules will be made standard equipment in car headlamps as of 2008.