B8 Light Emitting Diode LED or LD

No longer are these flat-area light sources limited to tiny windows of seven-segment lettering in wristwatches and hand calculators. In addition to being used as fiber optic transmitters, they are finding architectural uses as switches, security lights, decorative illumination, exit light facings, museum exhibit lighting, a 25 ft long nightclub marquee, and even an eight-story tall billboard in Times Square that uses more than 18,000,000 LEDs in its 10,000 sf area. One idea that shows particular promise is the flat fluorescent lamp: a serpentine tube of filamentous width, transparent on one

Fig. 6-20. The LED-inspired flat fluorescent lamp. '

LD + A Journal (IESNA, New York); Oct 1993, p. 29. • From p. 542: This figure was side and reflective on the other, arranged in maze-like loops to form a rectangular display of theoretically any size through which activated photons travel from a giver electrode at one end of the tube to a getter electrode at the other end; then the light radiated along the tube passes through microscopic red, green, and blue filters on its transparent side to create an articulate high-CRI sheet of light.

Recent research developments have also made LED lighting brighter, able to produce almost any color, and more economical to make. This, combined with the lighting's small size, lightweight, ruggedness, low power consumption, near-zero heat generation, high efficiency, and extremely long life, are pushing this illumination ever closer to becoming a major light source. Presently the biggest obstacle to this lighting's widespread use is its high initial cost. But it has been proven that their extreme efficiency and durability make them more cost-effective than almost any other light over long periods. Indeed, the Times Square billboard indicates that whole walls and ceilings of large rooms could be made of light-emitting diodes. Could acoustic-tile-like LED ceiling units be far away?

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