Re: And you thought LF stereo was exotic enough hobby

[Brian Reynolds <reynolds@xxxxxxxxx>]

Tom Deering wrote:
> >Here's a guy doing lensless stereo using zone plates:
> >http://www.neenas.com/depthography/jones.html
> 
> 
> After viewing his page, I still don't understand what zone plates
> are.  His explanation wasn't very clear.  And when I freeview his
> stereo pairs, they look like blurry, poorly matched cha-chas.
> 

If you have an astronomy text look for a diagram of the Airy
diffraction disk.  This is what a perfect star image should look like
(assuming no atmospheric or optical aberrations).  It has a bright
disk in the center (the star) with a series of concentric rings around
it that get dimmer as you get further from the central disk.

A zone plate looks like the negative of an Airy disk (a dark central
disk and concentric rings with clear spaces in between).  It forms an
image by diffraction of the light that passes through the zone plate.
Zone plates tend to have a much lower focal ratio than the equivalent
pinholes.

> I can't say I cared for the images.  Maybe it's like building a
> model steam engine--a historical experiment.
> 

Like many things, zone plate images are a matter of taste.  Some
people like them and some don't.

-- 
Brian Reynolds                  | "Dee Dee!  Don't touch that button!"
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http://www.panix.com/~reynolds  |    -- Dexter and Dee Dee
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