Re: [ATM] Crazy simple mirror cell idea

["Robert Houdart" <robert.houdart@cruxis.be>]

Nils Olof,

> A simple memorizable approximation: a 10 nm RMS surface deformation
> (or 100 square nanometers MS if you like ;-) corresponds to twice
> that on the wavefront, and assuming 550 nm green light, this
> deformation would lower the Strehl ratio by 0.2 (from 1.0 to 0.8
> for a perfect mirror, or from 0.9 to 0.7 for a less perfect one).
> 5 nm will lower by (5/10)^2*0.2 or by 0.05 which is not readily
> noticeable - 2.5 nm by 0.0125. It may make sense to aim for this
> when designing a cell for a quality mirror - if nothing else, it
> will give you some safety margin.

I could be wrong, but these numbers appear overrated by a factor of 2.

20 nm RMS surface error (1/27 wave) corresponds to a Strehl reduction of
0.2 which is equivalent to the classical "diffraction limited"
criterion.

10 nm RMS surface error gives a Strehl reduction of 0.05, and 5 nm RMS
surface error corresponds to 0.013 Strehl reduction.

Maybe you've done the conversion from surface to wavefront errors twice?

Robert Houdart
www.cruxis.com/scope/scope1100.htm

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