Freeform TIR collimators for the removal of angular color variation in white LED spotlights

Angular color variation in white, phosphor-converted LEDs causes undesirable yellow rings in the beams of spotlights. We developed an inverse method to design TIR collimators that remove the angular color variation for point light sources and significantly reduce color variation for extended light sources, without the need for facets, holographic foils or scattering surfaces. We performed several numerical simulations to evaluate the performance of this point source method for extended light sources.