EO Tech Tools Equations
Equations and corresponding legends for each of our EO Tech Tools.
Focal Length











FOS | Power of Surface 1 |
FIS | Power of Surface 2 |
F | Lens Power |
nOS | Object Space Index |
nL | Lens Index |
nIS | Image Space Index |
R1 | Radius of Surface 1 |
R2 | Radius of Surface 2 |
CT | Center Thickness |
P | Primary Principle Point |
P' | Secondary Principle Point |
EFL | Effective Focal Length |
BFL | Back Focal Length |
FFL | Front Focal Length |
NPS | Nodal Point Shift |
fF | Front Focal Point |
fR | Rear Focal Point |
Gaussian Beam






? | Wavelength |
zR | Rayleigh Range |
z | Axial Distance |
?(z) | Half Beam Diameter |
?0 | Beam Waist |
b | Confocal Parameter |
?R | Rayleigh Half Diameter |
R(z) | Radius of Curvature |
? | Half Angle Divergence |
Koehler Illumination







d1 | Source to Lens 1 Distance |
d2 | Lens 1 to Lens 2 Distance |
d3 | Lens 2 to Spot Diameter Distance |
DL1 | Diameter of Lens 1 |
DL2 | Diameter of Lens 2 |
FL1 | Focal Length of Lens 1 |
FL2 | Focal Length of Lens 2 |
Dsource | Source Diameter |
Dspot | Spot Diameter |
NAinput | Input Numerical Aperture |
NAoutput | Output Numerical Aperture |
Laser Spot Size

DI | Input Beam Diameter |
DO | Output Beam Diameter |
?I | Beam Divergence |
L | Working Distance |
1951 USAF

SAG

R | Radius of Curvature |
D | Diameter |
Simple Magnifier


MP | Magnifying Power |
FL | Focal Length |
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