# Dark-field light scattering microscope with focus stabilization

## TL;DR

This paper details a versatile dark-field light scattering microscope with focus stabilization, enabling stable long-term nanoparticle measurements and adaptable to multiple imaging modes.

## Contribution

It introduces a dual-mode dark-field microscope with focus stabilization and easy mode switching, enhancing stability and versatility for nanoparticle and biological imaging.

## Key findings

- Successful long-term nanoparticle scattering measurements
- Effective focus stabilization with active feedback
- Flexible setup for multiple imaging modalities

## Abstract

We present detailed design and operation instructions for a single-objective inverted microscope. Our design is suitable for two dark-field modes of operation: 1- total internal reflection scattering, and 2- cross-polarization backscattering. The user can switch between the two modes by exchanging one mode-steering element, which is also adapted to the Thorlabs cage system. To establish a stable background speckle for differential microscopy the imaging plane is stabilized with active feedback. We validate the stabilization efficacy by performing long-term scattering measurement on single nanoparticles. This setup can be extended for simultaneous scattering, fluorescence, and confocal imaging modes.