Quantitative evaluation of LED-based optical autofocus module
S Habte1, S Kumar1,2, J Lightley1,2
1Physics Department, Imperial College London, London, UK.
Journal of Microscopy
|July 29, 2026
Summary
An improved open-source optical autofocus (OAF) module uses an LED light source for better accessibility. This system achieves high axial stability below 10 nm, even with varying LED power.
Area of Science:
- Microscopy
- Optical Engineering
Background:
- Accurate autofocus is critical for high-resolution light microscopy.
- Existing optical autofocus (OAF) modules can be complex or rely on less accessible components.
Purpose of the Study:
- To develop and evaluate an improved, accessible OAF module (openAF) for light microscopy.
- To introduce a novel method for quantifying OAF system performance.
Main Methods:
- Replaced the superluminescent diode (SLD) with a fiber-coupled LED in the openAF module.
- Developed a 2D autocorrelation analysis of astigmatic fluorescent nanobead images to quantify AF performance.
- Evaluated both LED-based and SLD-based openAF modules on a high numerical aperture microscope.
Main Results:
- The new LED-based openAF module demonstrates high axial stability with a standard deviation below 10 nm for over 45 minutes.
- The performance quantification method is independent of AF light source power variations.
- The LED-based system achieves thermal equilibrium, maintaining stability.
Conclusions:
- The LED-based openAF module offers an accessible and high-performance solution for optical autofocus in light microscopy.
- The developed quantification method provides a reliable benchmark for evaluating AF system stability.
