US Patent 7692861 Illumination systems

Described are illumination systems whereby light spectra from multiple LEDs of various colors can be combined and polarized with minimal components, while substantially reducing the losses for the combining and polarizing. The described systems and methods use polarizing beam splitters (PBSs) with retarder stack filters to combine color and split polarization for mixed light beams in one step, and to ultimately align the polarizations of the several colored light beams.