Robust reconstruction of optical diffraction tomography for particle imaging in microfluidics

Optical diffraction tomography (ODT) plays a crucial role in achieving high-resolution imaging in microfluidic environments since it enables non-contact, label-free classification and morphological characterization of microscopic particles. However, due to the finite depth of microfluidic channels, particles often occupy different axial positions, resulting in positioning errors that degrade the reconstructed complex amplitudes. These errors, in turn, impair the quality of ODT reconstruction and may cause failure. Traditional iterative algorithms are often inadequate to correct such misalignments. To overcome this limitation, we propose a robust reconstruction approach tailored for three-dimensional (3D) particle field imaging in microfluidic systems. It combines four-step phase-shifting interferometry with an autofocusing algorithm to optimize the propagation distance and enhance the accuracy of complex amplitude recovery. The results demonstrate that the proposed method maintains reliable ODT reconstruction performance even under relatively high particle concentrations and axial misalignments. This approach provides a generalizable solution for robust 3D particle reconstruction, with strong potential for integration into complex microfluidic imaging systems.