Re: ATM Re: surface accuracy

["Bob May" <bobmay@nethere.com>]

<< yes' i accepts that, but how to measure the deviation of the test surface
from the reference surface.

suppose if the test surface is around (lambda/6) then how many fringes i
will see... and how can find it out..
Thanks
-arb
>>
It's not the number of the fringes but rather the shape of them that
determines the accuracy.  The fringes are produced by the interference of
the light between the light reflected from the lower surface and the upper
surface.  That tells you where the 1/2 wave distance is and that is your
comparison point.  You also know that the two surfaces aren't parallel to
each other as you have a bunch of fringes marching down the interface.
Thus, each fringe becomes a contour line in the distance between the two
surfaces.
P.S.  It is a lot better if you do the discussion on the list rather than
off as all of the present and future list viewers can see the questions and
answers.

Bob May
http://nav.to/bobmay
bobmay@nethere.com
NEW! http://bobmay.astronomy.net