Estimation of optical diffuse properties of Fresnel lenses

This paper proposes a method for determining the diffuse properties of sunlight concentrators such as Fresnel lens. The decrease in Fresnel lens concentrating ability is usually associated with imperfectness in optical refractive  surfaces, where some part of the direct light, which comes along the normal to the surface of the Fresnel lens and intended to be concentrated, is getting scattered and directing off a highly efficient concentrator solar cell. The diffuse light flux generated propagates inside the volume of the combined photovoltaic module. This flux undergoes multiple reflections from the structural elements, partially absorbed and ultimately reaches the photoconverters of  the planar circuit.