Reduction of intensity variations on the absorbers of ideal flux concentrators

Abstract

Although ideal concentrators such as the compound parabolic concentrator have the property that concentrated flux is uniformly distributed on the absorber when the angular acceptance is filled by the incident flux, the instantaneous flux distribution may be very nonuniform when illuminated by a point source.These nonuniformities may be reduced by texturing the surface with small distortions. The necessary reduction of concentrator throughput is small enough to allow such textured concentrators to accommodate a wide range of tolerances in concentrator efficiency and uniformity of the flux distribution. In particular, the suitability of such concentrators for some space applications is discussed. Results of measurements on a test model are presented that demonstrate the effective reduction of flux nonuniformities by reflectors that have been textured by a simple process. Two-stage concentrators for attaining high concentration ratios are shown to distribute the concentrated flux fairly uniformly across the absorber when illuminated by point sources within the field of view. Again the remaining nonuniformities may be removed by texturing the reflecting surfaces (entailing some reduction in concentrator efficiency).