Michel wrote:
> Sounds impressive! So what material are you using in your
> roll process? Do you have a web site showing these things?
The substrate I normally use is polyethylene pterphthalate (PET) film,
generally from 12 microns to 125 microns in thickness, depending on the
application. The fresnel structure itself is formed in a proprietary thermoset
layer which imparts a moisture and short-wave UV barrier, greatly extending the
outdoor survivablilty of the PET film.
I had originally intended that these lens arrays be held in place by their own
great tensile strength, but as a practical matter, lamination to glass is
preferred, with the glass side toward the sun and the elements. The glass and
the window film type adhesive give the film unmatched thermal stability and
20-year outdoor life.
My company website is so far out of date that I'm embarrassed to look at it
myself. There is little information about the fresnel lenses.
But if you must look at it:
www.spectratek.net
Until I begin to make something materially useful with my processes, I am
mildly distressed whenever I see the name of Augustin-Jean Fresnel up there on
the Eiffel Tower along with all those other great French scientists. Not only
did he invent the fresnel lens, but worked out all the theory of near-field
diffraction on which holography is based. I often wonder what he would think.
M.
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