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Thread: A whole load of questions

  1. #11

    A whole load of questions

    now, don't you worry 'bout that....

  2. #12

    A whole load of questions

    Quote Originally Posted by apn
    and now for something completely different, you can go look up "pinhole sieve" too
    What's pinhole sieve?

    Oh wait, I just looked at my avatar. <g>

    Cheers -

    george

  3. #13

    A whole load of questions

    Quote Originally Posted by GLSmyth
    What's pinhole sieve?
    Oh wait, I just looked at my avatar. <g>
    Cheers -
    george
    yeah, I had noticed that before... uber_cool dude

  4. #14

    A whole load of questions

    eureka, I found it !!! how about the whiz kid for zone plate/ sieve design?

    http://www.whizkidtech.redprince.net/zoneplate/

    there's a choice to design either zone plate or "megapinhole" [= sieve]

    thank you Adam Stanislav whoever and wherever you are

  5. #15

    A whole load of questions

    Quote Originally Posted by gneissgirl
    I share your pain! ;D ]
    Quote Originally Posted by Andrew
    NO GG... WE'RE HERE TO SHARE THE LOVE, DARLING !!!
    Andrew, you are a dirty old man, Mary is far to young for you ;D

  6. #16

    A whole load of questions

    Quote Originally Posted by taco
    Andrew, you are a dirty old man, ~~~ ;D
    and I'm only getting worse !!! :K)

  7. #17

    A whole load of questions

    ZP trivia

    Hopefully there is some how-it-works info on Zone Plates somewhere - I think they act like a Fresnel lens, which I think may be a diffractive lens rather than refractive. This probably touches on the reason why a zone plate is somewhat more focal length sensitive than a pinhole

    The concentric ring spacing and possible width are based on the Airy disc spacing that diffraction theory predicts for a round aperture's diffraction maxima and minima (one of the Bessel math functions).

    I haven't checked to see if a typical zoneplate in practice has non-linear spacing. The theoretical Bessel max/min spacing for a circular pinhole aperture and correspondingly a round zone plate predicts concentric rings at unequal spacing.

    For a square hole, the function is sin x/x which has linear spacing. If someone made a square zone plate (concentric square rings), they sould be equally spaced.

    I think the pinsieve substitutes the cluster of holes for the complete zone plate rings, but their position is based on the Zone plate.

    I don't know if the pin sieve is an artistic interpretation and combination of the theory or if it has a scientific origin also.

    So simple, but so complex...

  8. #18

    A whole load of questions

    The surface of each ring is equal to all the others. So it's a square root decrease in radius.
    It is made for a certain wavelength and focus. Read more here:

    http://en.wikipedia.org/wiki/Zone_plate

    http://ca.geocities.com/penate@rogers.com/zoneplate.html
    http://ca.geocities.com/penate@rogers.com/sieve/photonsieve.html

  9. #19

    A whole load of questions

    Quote Originally Posted by apn
    eureka, I found it !!! how about the whiz kid for zone plate/ sieve design?

    http://www.whizkidtech.redprince.net/zoneplate/

    there's a choice to design either zone plate or "megapinhole" [= sieve]

    thank you Adam Stanislav whoever and wherever you are
    Umm, andrew, where have you been???

  10. #20

    A whole load of questions

    Quote Originally Posted by gneissgirl
    Umm, andrew, where have you been???
    seriously... I've been punching tiny wee little baby holes into brass shim by hand !!! ;D

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