www.techmind.org logo
by W.A. Steer  PhD



Zoneplates consisting of alternate opaque and clear, or metallic and non-metallic concentric rings are commonly used to focus light or microwave radiation. Similar patterns also have uses in resolution-testing and quality-assessment of 2D imaging and filtering systems. This page introduces the geometry and uses of zoneplates and offers a downloadable program to construct them.


Zoneplates made of alternating rings of absorbing/transmitting or reflective/non-reflective materials are commonly used to focus electromagnetic radiation, typically microwaves or visible light. In the commonest case the concentric rings have radii proportional to the square root of the integer series, ie. 1, sqrt(2), sqrt(3), sqrt(4)=2, ...

Two-tone zoneplate image
Two-tone zoneplate, commonly used for focussing electromagnetic radiation

Such plates also have the property that the pitch (or frequency) of the rings increases linearly across the pattern, which gives rise to applications in the testing or evaluation of imaging and image-processing systems.

Greyscale zoneplate image
Greyscale zoneplate, commonly used for analysing imaging systems

zoneplate image
Rogue rings are a typical result of undersampling in a digital imaging or processing step

Software to download

Zoneplot is a simple application which runs under Windows 95 or later and enables you to generate basic symmetrical zoneplates of arbitrary size. It doesn't need any installation, won't touch your Windows Registry, and doesn't need or install any special .DLLs. Simply download the .exe file and run or "open" it.

Download: zoneplot.exe (may need Borland run-time library DLLs?)
By downloading this file, you consent to the standard disclaimer.


I hope to add more details of the mathematical equations linking ring size with focal length (and the short-focal-length 'corrections') and give more examples of applications, as and when time permits...
Created: April 2002
Last modified: 23 November 2003

Source: http://www.techmind.org/zoneplate/

©2003 William Andrew Steer