Guesses and questions from a techno-dummy: Does the frez lens spread the light over the entire convex surface, thereby concentrating the energy? Could that magic hotspot be focused onto a mirror and therefore redirected as a "spot" of intense energy?
All the parallel rays of light hitting the fresnel lens get bent so they all get together (are concentrated, converge) on one spot at the focal distance.
This is the same as a regular lens, except they brought the curved surface of a regular lens down to a flat surface with concentric rings, each ring reproducing a "ring" of the original lens:
http://80.36.73.149/almacen/medicina/oftalmologia/enciclopedias/duane/graphics/figures/v1/0520/001f.gifAnother example of how the curvature
s of a regular lens are brought down to a flat surface:
http://off-camera-flash.com/wp-content/uploads/2014/08/Fresnel-lens-01.jpgThe simplest mechanics of a lens, that is, two prisms slapped together as a "lens":
http://www.niiler.com/phy140/doubleprism.pngIncidentally, there are Fresnel mirrors, too. The last versions of the Polaroid insta-cameras had a Fresnel mirror in them.
Terry
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