Dave Rowe’s FringeXP
Let me start off with a rather blunt statement. “If Dave Rowe had not written his Fringe Reduction software, I would NOT have built an interferometer!” Bottom line, with out reduction software, Interferometry fringe images are near worthless (especially if you trying to test Parabolic mirrors at RoC with out an optical null!) Previously, the Fringe reduction software was “OH MY” expensive, and put interferometry pretty much out of the realm of ATM’s.
However, Dave did author his software, and He’s going to make it available to the public! You can download his software from Peter Ceravolo’s website here:
In the mean time, let me review the general process of how to go from Images of interference Fringes to final results.
i. Zernikes are odd little creatures, each value describes an aspect of the optic
ii. For more information on Zernike Polynomials, see Dr. Wyant’s web page here:
i. We can turn these Zernikes directly into a surface profile
1. While this sounds like a good idea, its not really
2. The problem is a single fringe image has the following possible errors
1. Aperture definition
2. tracing the fringe centers
3. Local “seeing” effects from air turbulences
4. The number and orientation of the fringes may be insufficient
ii. Alternatively, we should take SEVERAL fringe images
1. Find their individual Zernike values
2. Average the Zernike values into a final set
3. use the averaged values to create our surface map
4. See the below MS Excel file showing the deviations between individual fringes
2. My current reason for such a wide distribution of results is my LACK of a proper test tunnel.
I guess that’s it for the moment, I imagine once Dave gets his Web-Site up and running, he will have a substantially more accurate and complete description of his methodology.
In any event, I don’t claim to
be an interferometry guru (yet J). And I have a