In article <37c60299@news.povray.org>, "Bill DeWitt" <the### [at] earthlink net> wrote:
>I think you may be confusing a Fresnel lens with a diffraction grating.
>Fresnel is simply a compression of the relevant portions of a standard lens.
>....or maybe I am wrong. But I have used the Fresnel measurements to make a
>solar reflector that worked just like the parabolic dish reflector I modeled
>it on.
Fresnel lenses have been used for years and years in lightouses to magnify the
light... not to long ago they showed how this is used on "How 2" a BBC
television show running on the "Wam" network (which I tape and watch on
Sundays on my local cable network). I tend to agree that I'm wasting my time
at this point, I think the best thing for me to do is go with a visual thing
and use a cylinder light source to represent the beam (this is the basic
principle of using a combination of a fresnel lens with a parabolic
reflector).
PHIL
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