Three-dimensional refractive index reconstruction of red blood cells with one-dimensional moving based on local plane wave approximation

Abstract

To simplify the reconstruction optical system, an improved method is developed to reconstruct the three-dimensional (3D) quantitative refractive index of live cells based on a local plane wave approximation. In this method, the cell is illuminated by a convergent beam whose cross section is much larger than the cell, so the beam passing through the cell can be treated as a local plane wave. With the one-dimensional moving of cells in the beam cross section, multi-directional phase projections can be obtained using a Mach–Zehnder interferometer and the Hilbert transform phase retrieval algorithm. An inverse Radon–Radon iterative algorithm is used to reconstruct the 3D refractive index distribution which is verified by a simulation reconstruction. The corresponding set-up is applied to obtain the multi-directional phase projections and reconstruct the 3D refractive index of red blood cells (RBCs). The results show that only with a simple device could the method measure the 3D refractive index of cells with high precision. The reconstruction method could also be applied in opto-fluidic microscopy to fabricate a compact on-chip opto-fluidic tomographic microscope.