Re: Zone plates for a body cap

----- Original Message -----
From: "Beaker" <mbeacom@mac.com>

> Guillermo- how do you figure out the aperture of a zone plate? Mr.
> Pinhole mentions this formula: <radius = sqrt(wavelength *
> focallength * ring)>. I was guessing that this would give a good number
> to start with. Is this a good guess?

I gather that by "aperture of the zone plate" you mean the size of each of
the rings. Mr.Pinhole formula is what the scientific community uses for
their high-tech uses of zone plates and my non-scientific tests (focusing
aerial images produced by zoneplates) have confirmed that. Other use
slightly different formulas.

> One last thing- I've never worked with zone plates before, or even have
> litho negatives made, so we will learn together what works, and what
> doesn't!

Just one more suggestion, try making zone plates whose number of clear rings
give you f/stops that are equal or slightly smaller (numerically) than a
full stop, this will facilitate exposure calculations.

Guillermo
Received on Fri Oct 25 13:15:44 2002