Different simulation models for solar concentrators were developed to obtain the irradiance distribution on the absorber. Usually these optical simulations were valid only for a particular concentrator. Other simulations adequate for different concentrator shapes are based on ray tracing algorithms requiring high computing resources. An optimized reverse ray tracing model for flat mirror concentrators that allows to reduce the noise and the computing time necessary for such simulations is described. (c) 2006 Elsevier B.V. All rights reserved.