Some embodiments provide luminance-preserving non-imaging backlights that comprise a luminous source emitting light, an input port that receives the light, an injector and a beam-expanding ejector. The injector includes the input port and a larger output port with a profile that expands away from the input port acting via total internal reflection to keep x-y angular width of the source image inversely proportional to its luminance. The injector is defined by a surface of revolution with an axis on the source and a swept profile that is a first portion of an upper half of a CPC tilted by its acceptance angle. The beam-expanding ejector comprising a planar waveguide optically coupled to the output port of the injector. The ejector includes a smooth upper surface, and a reflective lower surface comprising microstructured facets that refract upwardly reflected light into a collimated direction common to the facets.