Testing the surface quality of a reflective parabolic trough solar collector with two flat null-screens

In this work, we present a technique for quantitatively assessing the optical quality of a parabolic trough solar collector. The presented method is an adaptation of the null-screen technology, a collection of processes that retrieve information from the reflection of a known object from the surface and then use that information to reconstruct the surface's normal vectors. Via numerical simulations, it is shown that the precision attainable by this method is up to 0.068 mrad, depending on the source of systematical error. In this study we only consider displacements of the physical null-screen as sources of error.