Patent ID: 7889430

Claim:
An etendue folding illumination system for illuminating a target etendue comprising: a folded collimator/concentrator having an input aperture at a first end of the folded collimator/concentrator, and an output aperture at a second end of the folded collimator/concentrator opposite the first end, the folded collimator/concentrator being a compound reflector having a reflective inner surface; a substantially flat reflective aperture stop coupled to the output aperture of the folded collimator/concentrator, the reflective aperture stop having an output clear aperture whose collimation angle, area and aspect ratio match corresponding parameters of the target etendue; a Light Emitting Diode (LED) device coupled to the input aperture of the folded collimator/concentrator, the LED device including at least one LED die having a flat reflective surface with a surface reflectance of at least 0.7 facing the output aperture; light emitted by the LED device and reflected by the reflective aperture stop passing back into the compound reflector for further reflection by the reflective inner surface of the folded collimator/concentrator, the flat reflective surface of the LED die, or both the reflective inner surface of the folded collimator/concentrator and the flat reflective surface of the LED die.