Optical
Enlarged nine times, OSRAM's IR prototype produces an output in direct current (dc) operation in excess of 400mW at 1A. In radial components the light can also be tightly focused through a lens, enabling extremely high radiant intensities. And for small angles of roughly 3degrees, values of up to 700mW/steradian (measuring the radiant intensity of sharply focusing infrared emitting diodes) can be achieved, even with a small chip.
Thin-film chips emit virtually all of the light generated internally through the top of the chip. They only have a thin light-generating layer that is so close to the surface, almost no light escapes at the side. This means that radiated output increases in direct proportion to the size of the chip.
The wavelength of OSRAM's new IRED is 850nm which is closer to visible light (400-780nm) than that of conventional IREDs that emit light with a wavelength of 880nm. CMOS and CCD cameras are usually sensitive in the borderline IR range, detecting a wider wavelength spectrum than the human eye. The 850nm IRED can therefore be used to illuminate scenes that cannot be seen by the human eye. Additional applications include automobile night vision systems, safety and security-related monitoring, video-aided monitoring of parking lots, and the measurement of traffic volume and speed. The IREDs are sampling now.
Cree announced two new, higher brightness additions to its XThin light emitting diode (LED) product family - the XT-24 and XT-27. The respective minimum radiant fluxes of these devices are 24mW and 27mW. Both the XT-24 and XT-27 chips are offered with a typical dominant wavelength of 460nm. This wavelength was selected to maximise the conversion efficiency of most commercially available LED phosphors, which convert blue to white light.
Target applications for the XT-24 and XT-27 LEDs are white light applications including LCD backlighting for mobile appliances and larger format LCD displays such as those used in car navigation systems. Both versions of the chip feature a low profile design with a typical height of 115microns and a low forward voltage of 3.2V. These features are desirable for the latest generation of ultra-miniature high brightness white surface mount LEDs favoured by designers of liquid crystal display (LCD) backlights.
Mike Dunn, Cree vice president and general manager for Optoelectronics, comments: "We believe this increase in brightness opens up new market opportunities for our customers and gives them a competitive alternative to today's cold cathode fluorescent lamp (CCFL) backlighting technology for large format LCDs." The XT-24 product is available in production volumes, while the XT-27 is sampling.
