Re: [ATM] [atm_free] RE: data and musings on thin mirror

["Mel Bartels" <mbartels@bbastrodesigns.com>]

> Sorry if I miss the point of counting the lines - but if you actually
> measure the *positions* of the lines on the mirror (provided they are
> not messed up beyond recognition by diffraction in the Ronchi grid), in
> terms of zonal positions (you know the line spacing of the grid), then
> you can compute a useful estimate of the figure - in exactly the same
> way as with a Foucault, Gaviola-Platzeck or lateral wire test. This is
> what SIXTESTS does. Just *counting* the number of lines visible won't
> do...


A long time ago I considered using the Ronchi bands with a pinstripe
dimensional scale across the face of the mirror. The idea was to move the
stage back and forth and compute the RC for that zone.  The problem that I
never solved was finding the center of the Ronchi band and its associated
fringes.

Mel Bartels


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