Beam Expander Calculator

Calculate lens focal lengths, system length, output beam diameter, and divergence for Keplerian and Galilean beam expander configurations.

Expander Parameters
Input Beam
Optical Design
Input lens f₁
25.0mm
Output lens f\u2082
125.0mm
System length L
150.0mm
Output Beam
Output diameter d_out
5.00mm
Output divergence \u03b8_out
0.200mrad
Min. output lens aperture
6.0mm

Note: The Keplerian configuration has an internal focal point between the lenses, suitable for spatial filtering with a pinhole. Avoid with high-power pulsed lasers due to air breakdown risk at focus.

Abridged Optics — Beam Expander Calculator v1.0Keplerian: L = f\u2081+f\u2082. Galilean: L = f\u2082\u2212|f\u2081|. \u03b8_out = \u03b8_in/M.

All information, equations, and calculations have been compiled and verified to the best of our ability. For mission-critical applications, we recommend independent verification of all values. If you find an error, please let us know.