Secondary optics that allow for the integration of a light-emitting diode (LED)-based luminescent lightsource into various étendue-limited applications—such as projection systems—are investigated. Using bothsimulations and experiments, we have shown that the optical efficacy of the luminescent light source canbe increased using a collimator. A thorough analysis of the influence of the collimator’s refractive index onthe optical outcoupling and luminance is investigated and it is shown that it is most optimal to use a refractiveindex of 1.5. The optimal shape of the collimator is equal to that of a compound parabolic concentrator.Experimental results show that by using a collimator, we can improve the amount of outcoupled light witha factor of 1.8 up to 2.1 depending on the used optical configuration of the LED-based luminescent light source.
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