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Image Enhanced Foucault Test

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Posted by Robert May on April 9, 2001 21:38:03 UTC

There has been some work done on automating the Foucault test. One approach is to inspect the image with a program that traces the ring of equal intensity that is at a zone. Another is to flip the intensity of the image and so some summing on that which again produces the ring of equal intensity as a ring and then the last method is to slice the image at some point and flip one half of the image so that you can compare the intensity of the image for the equal intensity of the two halves of the image. A variation of that would be to alternate the columns of the pixels and look for ajacent ones that match in intensity.
In other words, yes, work is being done on this. Some of the results have been reported in the press (the Amateur Telescope Making Magazine) and other places inlcuding, but not limited to, the SAA newsgroup and the ATM mailing list.
As to the Zygo, there are a quite large number of various interfrometers that can be made and some of them don't take much in the way of optics to do and you might want to search the web for articles on them. You do need a fairly stable surface (basement concrete floor is good) in order to get stable fringes but they do work and show a lot of info. For parabolas though, you need to do some data reduction to get rid of the shape or do a double pass test (you need a good flat as big as the optics under test) to get to the spherical condition.

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