Re: [ATM] How much cell induced deformation is too much?

["Stuart Hutchins" <stuart452@earthlink.net>]

----- Original Message ----- 
From: "Vladimir Galogaza" <vladimir.galogaza@zg.htnet.hr>
To: "Stuart Hutchins" <stuart452@earthlink.net>
Sent: Monday, July 12, 2004 3:41 PM
Subject: Re: [ATM] How much cell induced deformation is too much?


>
> Interesting thought.
>
> Apart from the agreement that "unambiguous unit" meter is now defined as
> certain number of waves of specified light,  one possible reason in
> using waves in surface quality description is (in my opinion) the fact
> that ultimate quality limit of mirror is given by diffraction on aperture
> which is wavelength dependent (Airy disc size) even if surface is perfect.
> Imperfections acceptable in IR are not necessarily acceptable in UV,
> not to speak about radio frequency dishes.
> It is true that "waves come in all sizes" but  corresponding diffraction
discs
> come also in all sizes measured in meters although all those sizes are
> mutually equivalent.
>
Exactly so.  Measure the geometric aperture and reflecting surface of the
optic in fixed units of length, then calculate the wavefront response for
the wavelengths of use, which now stretch from near UV to IR even for
amateurs.  The "ambiguity" was raised by the increasing use of HeNe
interferometers to test mirrors.  Besides, I hate adding fractions.

Stuart


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