Asymmetric dual paraboloid reflector: improving system throughput by narrowing cone angles

Abstract

Wavien patented dual paraboloid reflector (DPR) system, while optimal in maximizing image brightness (equivalent to minimizing the image aberration) at the input of its light pipe, does not produce maximal lumen throughput at its output. The overall lumen throughput depends in large part on three factors: Fresnel losses and image aberration, both defined at the input face of the light pipe, and the light pipe's input dimensions. Fresnel losses can be reduced by narrowing the cone angles of the light cone incident on the light pipe, which in turn can be achieved by increasing the size and/or focal length of the second paraboloid reflector. Smaller cone angles also mean reduced tapering of the light pipe which translates into larger input sizes (as its output dimensions are fixed) and higher coupling efficiency. Unfortunately this gain in coupling efficiency comes at the expense of breaking the system symmetry, which destroys 1:1 imaging and leads to increased aberration and reduced brightness. Using a ray-tracing software an optimal point of operation can be reached and it is found that at least 10% increase in lumen throughput over the symmetric DPR system is achievable.