• Country/Region
  •   
 

 
Focal Length Calculator

View All Technical Tools

Relate optical and mechanical parameters of simple lenses in order to ease integration into application assemblies. Select index from list of EO's own optical substrates to help calculate focal lengths and principal points of any standard lens.

Note: This calculator follows the standard sign convention for the optical radius of curvature where if the vertex of a surface lies to the left of the center of curvature the radius of curvature is positive, and if the vertex lies to the right of the center of curvature the radius of curvature is negative. In the figure, R1 is positive and R2 is negative.

Enter your Information


OR Plano 

OR Plano 

  

Results


Effective Focal Length, EFL (mm): --       

Back Focal Length, BFL (mm): --       

Front Focal Length, FFL (mm): --       

Primary Principal Point, P (mm): --       

Secondary Principal Point, P'' (mm): --       

Shift in Nodal Point (mm): >--       

Focal Length Calculator

Equations and Corresponding Legend

$$ \Phi_{\text{OS}} = \frac{n_L - n_{\text{OS}}}{R_1} $$
$$ \Phi_{\text{IS}} = \frac{ n_{\text{IS}} - n_{L} }{R_2} $$
$$ \Phi = \Phi_{\text{OS}} + \Phi_{\text{IS}} - \Phi_{\text{OS}} \, \Phi_{\text{IS}} \, \left( \frac{\text{CT}}{n_L} \right) $$
$$ P'' = - \frac{\Phi_{\text{OS}}}{\Phi} \, \left( \frac{n_{\text{IS}}}{n_L} \right) \, \text{CT} $$
$$ \text{EFL} = \frac{1}{\Phi} $$
$$ f_F = - n_{\text{OS}} \cdot \text{EFL} $$
$$ f_R = n_{\text{IS}} \cdot \text{EFL} $$
$$ \text{BFL} = f_R + P'' $$
$$ \text{FFL} = f_F + P $$
$$ \text{NPS} = f_F + f_R $$
$$ P = \frac{\Phi_{\text{IS}}}{\Phi} \, \left( \frac{n_{\text{OS}}}{n_L} \right) \, \text{CT} $$
ΦOS Power of Surface 1
ΦIS 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

  Application Note

Understanding Focal Length and Field of View

Learn More

Related Product Category: Optical Lenses

View All Now

Was this content useful to you?

Need a Quote? Add a stock number to begin our two-step quote process.

Edmund Optics Facebook Edmund Optics Twitter Edmund Optics YouTube Edmund Optics LinkedIn Edmund Optics Instagram



PROUD MEMBERS OF:

Spectaris Optence Photonics21 Epic EMVA EOS Photonics France

×