Re: compensating zone plate

Perhaps a silly,
just-woke-up-and-checked-my-mail-while-still-sleepy
kind of thought, but.....

What would happen if you projected a zone plate
pattern of rings onto the surface of a largish half
sphere? Wouldn't that bring the outer rings closer to
the film plane? Would that help to compensate for fall
off? I imagine you'd need a lot of rings.

Also, I've long wondered why no one makes zone plates
by etching and staining glass. Every zone plate I've
seen has dirty, scratched, cloudy clear zones because
it's been made on film base. Wouldn't glass be better?
Could probably be done using photoetching. Maybe too
complicated, probably too expensive.

Colin

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Received on Tue Aug 21 11:57:35 2001