The Medium Intensity Approach Lighting System (MALSR) in use today at many airports throughout the United States employs many incandescent spot lamps. These lamps are relatively high wattage and, because of their relatively short life, require continual maintenance. Light emitting diodes (LEDs) have matured to the point that they can be considered to replace the inefficient incandescent lamps, especially when the latter are used with color filters. Under a Federal Aviation Administration (FAA) contract, Lighting Innovations Corporation (LIC) has developed LED based green runway threshold lamps for use in the MALSR. They already have been tested under flight conditions and are scheduled for full operational testing at several airports throughout the country. This paper addresses the advantages of LEDs over incandescents in this and other airfield lighting applications. Photometric, radiometric and spectral quantities are discussed, as are electrical, thermal and mechanical aspects of the project.
A MEMS-based, low-power, incandescent light source is being developed. This light source is fabricated using three bonded chips. The bottom chip consists of a reflector on Silicon, the middle chip contains a Tungsten filament bonded to Silicon and the top layer is a transparent window. A 25-micrometers -thick spiral filament is fabricated in Tungsten using lithography and wet- etching. A proof-of-concept device has been fabricated and tested in a vacuum chamber. Results indicate that the filament is electrically heated to approximately 2650 K. The power required to drive the proof-of-concept spiral filament to incandescence is 1.25 W. The emitted optical power is expected to be approximately 1.0 W with the spectral peak at 1.1 micrometers . The micromachining techniques used to fabricate this light source can be applied to other MEMS devices.
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