KEYWORDS: Light emitting diodes, Accelerated life testing, Humidity, Failure analysis, Reliability, Statistical modeling, LED lighting, Testing and analysis, Temperature metrology
As the traditional life testing method is extremely time consuming, this paper proposed an accelerated life test method for LED source. The possible failure forms of LED chips are analyzed, and the causes are also discussed. A complicated accelerated life model is constructed in this paper and how to get the parameter is discussed. LED source high accelerated life testing platform is built to test the sample chips life, and different application of constant temperature and humidity mixed environment tests are used to stress the sample. The accelerated life model estimate parameter is obtained, and the life of sample LED chips is estimated by the model.
A 1200m visible searchlight system is designed based on photometry and application of geometric optics. To generate intensity distribution of this relatively powerful light beam we propose to use a high power LED and several refractive optical elements, which are composed of two plane-convex lenses and a conventional Fresnel lens. Two plane-convex lenses enable refraction of the side rays from the LED to the front direction which incident on the Fresnel lens. Fresnel lens, in its turn, concentrate the light flux and provide a nearly collimated beam to meet the requirement of forming a well-illuminated area across the road in the far field. Simulation data shows that this searchlight allow generating an appropriate illumination distribution for the long range requirements. A proof-of-concept prototype producing acceptable illuminance is developed.
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