Etendue efficient illumination system using dual paraboloid reflectors and lensed tapered lightpipes

Abstract

With the increased interests in mass production of LCD, LCOS and DLP microdisplay-based projectors and televisions, the image panel sizes become smaller and requires more efficient coupling of light from the source to the image panel. At the same time, the demand for high-energy efficient general illumination system also requires efficient coupling of light from a light source into fiber optics. To illuminate these smaller image panels and fibers efficiently, a patented dual paraboloid reflector system has been developed to collect and focus light from an arc lamp onto the targeted application without loss of brightness. Arc lamps with longer arc lengths can be used, which are usually easier to make and have longer life. The dual paraboloid reflector1,2 system consists of two parabolic reflectors placed symmetrically facing each other. The first parabolic reflector collects and collimates light into a parallel beam. The second parabolic reflector intercepts the parallel beam and focuses the light into a lensed rectangular tapered light pipe (TLP) resulting in a unity magnification, i.e. 1:1 imaging, with conserved brightness. Due to the unique nature of 1:1 imaging of the system, together with the retro-reflector, the folding of the arc to increase brightness will also be described. The TLP transforms the focused light into an output with the needed area, shape, and numerical aperture. 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 or at the input face of the fibers. The reflection of light twice in the dual paraboloid reflector system provides high IR and UV rejection ratios, resulting in less degradation of the optical components and fibers. ASAP models of the system and experimental results will be presented. The shape of the etendue curve also provides higher efficiency in using polarization recovery system. Several patent-pending light-pipe-based polarization recovery and recycling systems, will be discussed. Calculation and experimental results will also be presented.