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steve fairbairn
steve fairbairn
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How to construct a Fresnel zone plate

Mar 21, 2012 5:13 AM

Does anyone know of an easy way to draw a binary Fresnel zone plate such as the one shown here?

In this case the size of the innermost circle is immaterial but each successive ring (black or white) must be of equal area to the previous one.

I am searching for a quick way that does not involve too many complicated calculations.

zoneplate.gif

1680 Views   12 Replies   Latest reply: Mathias17, Mar 23, 2012 9:44 PM
 
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  • Jacob Bugge
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    1. Jacob Bugge,
    Mar 21, 2012 6:38 AM   in reply to steve fairbairn
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    Steve,

     

    Basically, the ratios of W values are just the square roots of the natural numbers, 1>2>3>4 etc.

     

    Square root of 1 = 1

    Square root of 2 = 1.41421

    Square root of 3 = 1.73205

    Square root of 4 = 2

     

    If you start somewhere in the row, you will have to use quotients by dividing the latest number by the first one (it is 1 when you start with the 1). So it is much easier to start with 1 and then just delete the innermost one(s) if desired.

     

    So almost any small calculator can do it for you. You may save the innermost width in the memory and multiply that by the square roots as you go, or you may use copies of the first circle and just multiply the W/H by the square roots as you go.

     
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  • steve fairbairn
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    2. steve fairbairn,
    Mar 21, 2012 8:34 AM   in reply to Jacob Bugge
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    Thanks Jacob, I didn't realize it was that simple.

    Steve.

     
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  • Jacob Bugge
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    3. Jacob Bugge,
    Mar 21, 2012 9:03 AM   in reply to steve fairbairn
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    You are welcome, Steve. Neither did I, before I grabbed a pencil and drew a few rings and looked at them.

     
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  • steve fairbairn
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    4. steve fairbairn,
    Mar 21, 2012 11:12 AM   in reply to Jacob Bugge
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    :-)

    Having neither brains nor a pencil I did it with Excel.

    Copy/paste from there does it very nicely.

     
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  • Luke Jennings
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    5. Luke Jennings,
    Mar 21, 2012 11:28 AM   in reply to steve fairbairn
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    Building a lighthouse, Steve?

     
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  • steve fairbairn
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    6. steve fairbairn,
    Mar 21, 2012 1:54 PM   in reply to Luke Jennings
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    Nope. Mucking about with moirés :-)

     
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  • Jacob Bugge
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    7. Jacob Bugge,
    Mar 22, 2012 4:18 AM   in reply to steve fairbairn
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    Shall we have the pleasure of seeing the pattern(s), Steve?

     
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  • steve fairbairn
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    8. steve fairbairn,
    Mar 22, 2012 5:23 AM   in reply to Jacob Bugge
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    One of the more obvious ones:

    Picture 2.png

    But there are others and you can do them in colour too :-)

     
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  • Jacob Bugge
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    9. Jacob Bugge,
    Mar 22, 2012 7:08 AM   in reply to steve fairbairn
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    Nice and strange. Thank you, Steve.

     
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  • Mathias17
    439 posts
    Feb 20, 2012
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    10. Mathias17,
    Mar 22, 2012 8:32 AM   in reply to steve fairbairn
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    Great! May I ask what it's application is/what you're using it for?

    You've given ideas. Recently became obsessed Shepard Fairey's work and this technique is a nifty way to create some interesting elements/pattern fills, kinda like he does.

     
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  • steve fairbairn
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    11. steve fairbairn,
    Mar 22, 2012 10:20 AM   in reply to Mathias17
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    May I ask what it's application is/what you're using it for?

     

    The werewolf complex. Designer by day, artist by night :-)

     
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  • Mathias17
    439 posts
    Feb 20, 2012
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    12. Mathias17,
    Mar 23, 2012 9:44 PM   in reply to steve fairbairn
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    Oh, is that what we're called? Sweet. Greetings, fellow werewolf. Crap of mine.

     

    Looking through Fairey's stuff, look how he uses layered patterns to create interesting "dither" textures with just one color print; very cool.

     

    http://i.imgur.com/BGt3H.jpg  http://i.imgur.com/qDxhT.jpg

     
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