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Best fit radius

Best fit radius

Best fit radius

I am looking for an equation that will solve for the best fit weighted average radius for a conic surface.  This is to correlate with our interferometer measurements.  Currently we do this by a brute force method creating sag tables of the conic surface and a spherical surface and use solver to minimize the RMS error.  I assume there is a more eloquent way to do this however.  Thank you for your help.

Rob Stupplebeen

RE: Best fit radius

I'm not sure I understand why you think there's a "better" solution.  "best fit weighted average" implies doing a statistical fit, which appears to be what you are doing.


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RE: Best fit radius

I was hoping for a closed form solution instead of the brute force sag table method.

For a given Radius, Conic, and Aperture a best fit radius should be able to be derived.  Before figuring it out myself I was hoping someone had already done it.  If not I'll figure it out and post here.  Thanks.

Rob Stupplebeen

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