Re: [ATM] TraceXP, Ronchi Simulation, etc.

[Aplanatic@aol.com]

Mike Peck wrote:

> I wrote up some notes a while back making an argument for how to treat an 
> extended light source in a Foucault test. The same argument works for 
> wires, spots, Ronchi gratings, etc. with appropriate modifications. The 
> article is at <http://home.netcom.com/~mpeck1/astro/foucault/ext_foucault.pdf>.
> 
> Years before this Jim Burrows did something essentially similar to simulate 
> an extended source in his program DIFFRACT. I think his rationale was 
> different from mine though.
> 
> I'm still offering bonus points to anyone who identifies the unstated 
> physical assumption I'm making.

Thanks for the URL to the article.  I remember reading this a while back but could no longer find my reference to it.  I'm not sure about the physical assumption that you mention, but there is one thing that worries me about this treatment.  An extended source would be comprised of uncorrelated point sources, would it not?  At least for the typical LED light source that ATMs use these days.  If so, then you should sum intensities in equation (4), not amplitudes.  The mathematics looks rather complicated to sort out this difference, yet I suspect that it has little practical effect.  In other words, I beleive that your method yields answers that are quite close to reality for most practical situations.

Dave


_______________________________________________
ATM mailing list http://www.atmlist.net/