Re: Zone Plate lens or aperture was Re: Pictorico for Zone Plate

Hello Yves,

I think we're wondering slightly off topic here, but I just had to...:

If the word "lens" is preserved for refraction optics, then pinholes are
not lenses. I believe this would be the most common understanding of the
word.

However, refraction optics are really nothing but a special case of
diffraction optics (at least at the theoretical level). As a result, one
may well choose to refer to diffraction optics as lenses. That would
include pinholes, Fresnel zone plates and the more recent photon sieves
(http://www.photonsieve.de/), as well as their derivatives, like the
mega-pinhole (http://www.whizkidtech.redprince.net/zoneplate/) and
pinhole sieve
(http://ca.geocities.com/penate%40rogers.com/sieve/photonsieve.html).

I doubt if many are willing to change the usual meaning of the word
"lens", though. Personally, I would prefer to limit the use of the word
to refraction optical components. Consequently, I would refer to
pinholes etc. simply as "diffraction optics", or perhaps stretching it
to "diffraction lenses".

Best regards,
Tom Einar Andersen

Ps. I have not tried to make zone plates on Pictorico. I don't think the
result will be good, even if the resolution of the printer is high
enough. The surface of the OHP is covered in microscopic particles (see
www.pictorico.com/ceramic.php). I think these will diffract the light
too much, and at the very least, the result will be significantly
different from a clear film (and probably much softer).

Yves Gauvreau wrote:
> Since you have to focus a zone plate I would have no problem calling
it a
> lens. The usual pinhole aperture could probably be called a lens in the
> theorical sense. Infinitely this, infinitely that, 0 this 0 that, etc. it's
> kind of a singularity. I'm not a formalist, expert or anything else in these
> matters but I wouldn't trash the "pinhole lens" expression just yet.
Received on Wed Feb 22 07:57:45 2006