Design and optimization of tapered light pipes

In illumination systems for projection display, it is often necessary to tailor the aperture size and angle of light to suit the system requirements such as an imager panel. One way to do that is to use lenses, but depending on the angle and area this may not be achieved economically in terms of space and costs. Non-imaging optics is often used to perform such function. A compound parabolic concentrator (CPC), which is simple to use and small in size, is one example of such approach, but it has the disadvantage of non-uniform output intensity profile and not conserving brightness. A tapered light pipe (TLP) is often used instead to alleviate such shortcomings, but such light pipe would need to be infinitely long to conserve brightness, which makes it quite impractical. In this paper, a lensed tapered light pipe is described that change the area and angle of light with minimal loss of brightness and provide a very uniform output intensity profile at the output. Numerical modeling using ray tracing computer program is used to optimize the TLP for each applications.