To: atm{at}shore.net
From: Jim Burrows 
Reply-To: Jim Burrows 


At 08:37 2003-02-28 -0500, James Lerch wrote:

> > Wouldn't you divide the wavelength (~550nm) into the mm defocused to get
>wavelength defocussed?
>
>I finally wrote to Cor Berrevoets (Author of Aberrator) and got the
>following answer (which he got from Suiter's book)
>
>Focus (waves) = focus (mm) / (focalratio*focalratio*8*550e-6)

Being a surface RMS enthusiast (which we should keep < 20 nm), I get
from defocus dF the surface

         RMS = dF/(32 sqrt(3) (f/)ý)

which agrees with Born & Wolf, Eq. (27) on p. 491.

         -- Jim Burrows
         -- mailto://burrjaw{at}earthlink.net
         -- http://home.earthlink.net/~burrjaw
         -- Seattle N47.4723 W122.3662 (WGS84)

--- BBBS/NT v4.00 MP