Efficient dual paraboloid reflector illumination system for projection display

Abstract

With the increased interests in mass production of LCOS and DLP™ crodisplay-based projectors and televisions, the image panel sizes become smaller and the pixel counts become higher. While the image panels are being miniaturized, the screen sizes required by the users are increasing. The two factors together require an increasing amount of light passing through the small image panels, thus increase the brightness requirement of the light sources. Most lamp developers approach the issue by reducing the arc length of the lamp, thus increasing the brightness of the arc. But, traditional reflectors used to collimate or focus light from the arc degrade the brightness of the arc. In this paper, a novel approach is used to increase the brightness of an illumination system by preserving the brightness of the arc using a dual paraboloid reflector system, thus relaxes the requirement of have a shorter arc gap lamp. To illuminate these smaller image panels, a patented dual paraboloid reflector system has been developed to collect and focus light from an arc lamp onto the image panel without loss of brightness. This optical platform provides the control and etendue efficiency that has been missing in standard illumination systems. The dual paraboloid reflector 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 rectangular tapered light pipe (TLP) resulting in a unity magnification, i.e. 1:1 imaging, with conserved brightness. 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. 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. ASAP models of the system and experimental results will be presented. The advantages of this system when applied to polarization recovery systems, polarization recycling systems, and color recycling systems will be discussed.