Incoupling and outcoupling of light from a luminescent rod using a compound parabolic concentrator

Secondary optics that allow for the integration of a light-emitting diode (LED)-based luminescent light source into various étendue-limited applications—such as projection systems—are investigated. Using both simulations and experiments, we have shown that the optical efficacy of the luminescent light source can be increased using a collimator. A thorough analysis of the influence of the collimator’s refractive index on the optical outcoupling and luminance is investigated and it is shown that it is most optimal to use a refractive index 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 with a factor of 1.8 up to 2.1 depending on the used optical configuration of the LED-based luminescent light source.