Despite continual improvements in LED brightness, color and efficacy, one problem remains that could hamper the LED's success in the lighting community: the absence of a consistent definition of life. At the moment there is no standard for defining or measuring LED lifetime. Much of the confusion within the lighting community is related to the fact that LEDs do not fail in the same manner as other types of light sources. Rather than experiencing a complete operational failure, LED light output slowly decreases with time. Long-life claims without concrete data also have led to skepticism among lighting professionals and would-be purchasers of LED systems. Manufacturers do not present measured life data primarily because no standard testing procedure exists and life tests are generally too time consuming and costly.
The Alliance for Solid-State Illumination Systems and Technologies (ASSIST) - a collaborative group of LED and fixture manufacturers, systems end-users, and government agencies organized by the Lighting Research Center (LRC) at Rensselaer Polytechnic Institute - recently set forth recommendations that define LED life and life measurement methods for general lighting. These recommendations were developed from studies of LED life and light level acceptance conducted at the LRC and by other researchers, as well as from input provided by major LED and traditional lighting manufacturers.
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