Optical EngineeringPerformance of phosphor-coated light-emitting diode optics in ray-trace simulations
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In commercial high-brightness phosphor-coated white LED packages the phosphor is put down on the die at the center of the hemispherical encapsulation, representing a quasi point source that provides convenient optical control in luminaire design. However, specific applications may benefit from other package geometries and beam shapes regarding efficiency, color uniformity and thermal management. In order to examine optical arrangements, a solid model of an InGaN LED die and the optical system including the phosphor were simulated using a Monte Carlo forward ray tracing technique. Photoluminescence was implemented as two separate processes: short-wavelength LED emission and phosphor absorption was traced first, followed by reemission of the down converted radiation by the phosphor layer; optical properties of existing phosphors were used. Output parameters of the two ray traces were combined and evaluated for the geometries examined.