This article seems to paint Fresnel lenses as some new kind of optics. They're not. The point of Fresnel lenses is to save weight and thickness. In an ordinary lens, its thickness is proportional to its diameter. In a Fresnel lens, thickness is (almost) constant, irrespective of diameter. So if you need a lens that's a meter in diameter (e.g. for a lighthouse) the weight is enormous if you use ordinary lens technology. Fresnels are lighter because Mr. Fresnel figured out that all the glass in the middle was unnecessary. The angles at which the rays meet the lens surface are what matter, and in his lens the angles are preserved without all that heavy glass in the middle.