A zoomable LED spot light with high angular beam sharpness has been made. The prototype is measured luminaire efficiency of 33.2%, total flux output of 4320 lm and central illuminance of 8940 lux at a distance of three meter. A qualitative definition as F/B ratio (F: field angle; B: beam angle) to evaluate the angular beam sharpness is proposed. The prototype has an F/B ratio of 1.35 compared to F/B ratio of 2 for the conventional low-power LED spot lights. Finally, a novel design with in-rod reflectors and a single integrator rod that has F/B ratio of 1.1 is also presented.
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