Zone Plate Equations

Zone Plate Equations

Variables

f = focal length
$Lambda$ = wavelength
$Phi$ _r = phase variation
r_m = radius of m^th zone
m = zone #
1 $<=$ N $<=$ Infinity

Image of Zone Plate

Definitions

GZP = Geometric Zone Plate, paraxial, f# > 10
IZP = Interferometric Zone Plate, f# < 10
GHZP = Generalized Holographic Zone Plate

Equations

For GZP: r_m =
For IZP: r_m =
For GHZP: r_m =

Properties of Zone Plates

Minimum zone width $~$ 2 $Lambda$ f # $~$ minimum spot size
Depth of focus $~$ 2 $Lambda$ f # ²
Chromatic aberration (m = number of zones illuminated)
Hybrid condition (f zone)/(f lens) = (n-1)/ $Lambda$ (dispers const.))
Hybrid Achromats typically use GZP pattern and less than 300 zones

Last modified on 9/22/97
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