Re: [ATM] Foucault and interferometry surface detail compared. Mirror two.

[Michael Peck <mlpeck@hughes.net>]

At 22:38 5/25/06, Dale Eason wrote:
>I have completed foucault and interferometry analysis
>on a second mirror.
>
>http://doeason.home.comcast.net/barry8/Barry_analysis.html
>
>Do any of you find this interesting?  If not I will
>stop posting it here.
>

Dale:

I think you should post this material and not worry about the 
feedback you're getting.

A couple questions about your Foucault simulations. 1) How do you 
treat an extended light source? 2) How do you treat an incoherent light source?

Getting to your writeup, the first three bullet pointed observations 
are consequences of the Fourier domain filter(s) you're using. I 
think the ringing happens because you're using a hard edged filter to 
isolate the sidelobe. Features get smeared out because you're low 
pass filtering them -- remember a Gaussian filter applied to the 
Fourier transform is equivalent to a Gaussian blur applied to the 
original image.

The fourth bullet point happens because anything that causes fringe 
contrast to vary will show up as an artifact in the wavefront map. In 
the interferograms you sent me for example there are some donut 
shaped shadows that are probably due to dust somewhere in your 
optical system. If you look hard enough I bet you'll see some donut 
shaped hills or valleys in your wavefront maps.

Mike


----------
Michael Peck
http://wildlife-pix.com

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