Designing optical devices based on non-uniform rational Béziers splines

Abstract

Optical system design has a significant impact on solar power plant efficiency. It can be advantageous to be able to very precisely adapt mirror shapes in order to improve energy yield. In this article it is investigated whether it is feasible to use non-uniform rational Béziers splines (NURBS) to describe mirrors. Algorithms and equations to evaluate optical performance by ray tracing are lined out. A parameterization scheme is given that reduces the degrees of freedom to a level suitable for automatic processing. To prove feasibility, a secondary reflector based on a NURBS surface and a compound parabolic concentrator (CPC) are designed for a specific test application and compared to each other. It is found that the suggested design method is feasible on contemporary personal computers and that the NURBS based surface performs well compared to the CPC.