Proceedings PaperEtendue efficient coupling of light using dual paraboloid reflectors for projection displays
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With the introduction of Digital Micromirror Device (DMD) and Liquid Crystal on Silicon (LCOS) technologies, imagers for projection displays become increasingly smaller, thus requiring more intense, focused light with lower etendue values. To illuminate these smaller imagers, a patented dual paraboloid reflector system has been developed to collect and focus light from an arc lamp onto the imager without loss of brightness. This powerful optical platform provides the control and etendue efficiency that has been missing in standard illumination sy stems. The dual paraboloid reflector system consists of two parabolic reflectors placed symmetrically facing each other. The first parabolic reflector collects and collimates it into a parallel beam. The second parabolic reflector intercepts the parallel beam and focuses the light with unity magnification, i.e. 1:1 imaging, into a tapered light pipe (TLP) with conserved brightness. The TLP transforms the focused light into an output with the needed area, shape, and numerical aperture (NA). It also acts as a homogenizer so that the intensity profile at the output surface is uniform and eventually provides a uniform intensity profile at the screen. The reflection of light twice in the dual paraboloid reflector system provides a high IR and UV rejection ratios, resulting in less degradation of the optical components. Polarization and color recycling systems are also designed taking advantage of this reflector configuration.