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In addition to our comprehensive archive of Application Notes, Frequently Asked Questions, Glossary terms, and a variety of other resources, we now have technical calculators based on commonly used and referenced equations in the Optics, Imaging and Photonics industries. View EO Tech Tools Equations to see the equations used for each calculation. Should you have any questions, suggestions or need further information, please feel free to Contact Us.

Koehler Illumination Calculator

Koehler Illumination  Equation

Mathematically determine how to configure a source and two lenses into a Koehler Illumination setup. Calculator uses the paraxial lens approximation and enables an initial lens selection. Once lenses are selected, EO recommends modeling one’s Koehler Illumination setup in optical design software such as Zemax, CodeV, or FRED to analyze and revise as needed. Please note that performance will vary based on source and lens selections.

Source Diameter (mm)
Lens 1 Diameter (mm)
Lens 1 Focal Length (mm)
Lens 2 Diameter (mm)
Lens 2 Focal Length (mm)

Source to Lens 1 Distance (mm) --     
Lens 1 to Lens 2 Distance (mm) --     
Lens 2 to Spot Diameter Distance (mm) --     
System Length (mm) --     
Convergence Size (mm) --     
Input Numerical Aperture, NA --     
Output Numerical Aperture, NA --