A zone plate created not by circles but by spirals. They grow radially like a square root function while their line width decreases accordingly. In homage to Augustin-Jean Fresnel, I have named them “Fresnel spirals”.
Please click/touch and move the top image.
Reference:
Migdał, Piotr: migdal.wikidot.com, 2008, 3 kB PostScript program!
Literature:
Huguenin, J. A. O. et al. “Topological defects in moiré fringes with spiral zone plates.” Journal of the Optical Society of America. A, Optics, image science, and vision 20 10 (2003): 1883-9 opg.optica.org.
Spiral in Spirals: (.svg)
