[ATM] Interferometer Fringe Contrast From Coated Mirrors

[clement.focuser at verizon.net (Don Clement)]

> From: "Donald "Don" Ware" <mimas@charter.net>
>
> >
> > Roger at the Mirror Lab in Arizona suggested using a pellicle filter.
These
> > are actually sold as pellicle beam splitters, transmitting a percentage
of
> > the ray and reflecting the rest.  The one I was able to find transmits
67%,
> > which, because the ray passes through twice actually reduces the light
from
> > the mirror by about 60%.
> >
> > While a pellicle beam splitter that transmits 50% or even 40% would
probably
> > be better, I am getting quite good fringe contrast from coated mirrors.
> > The fringes are only slightly broadened due to the extra optical
elements in
> > the path.

Pellicle beam splitters are not hard to make. I just made some rather large
ones 3' x 5'. Actually the poor mans double pane windows :-{)  It was 11* F
here in Southern California only a couple of weeks ago! But seriously, to
make a small pellicle beam splitter glue 0.0003" thick Mylar film to a flat
frame and then heat the Mylar  film with a hair drier or industrial heat
gun.



Don Clement

Running Springs, California

http://www.clementfocuser.com