A linear Fresnel lens for LED illumination is configured initially by
using a meridional flux-assignment method and is then corrected by
assessing the three-dimensional flux distribution of individual facets.
The facet angles are slightly altered as required to produce uniformity.
A variety of specialized lens shapes are generated, such as for
illuminating shelves in commercial refrigerator food-display cases. The
lens shapes are suitably thin for economical production by extrusion.