Partially coherent optical diffraction tomography for label-free quantitative microscopy

Abstract

In this work we present a tomographic technique for label-free quantitative microscopy that exploits the benefits of the partially coherent illumination. In contrast to conventional holographic techniques based on the coherent optical diffraction tomography (C-ODT), our approach uses an inexpensive non-interferometric setup comprising an electrically tunable lens and low spatially coherent illumination. This setup provides the refocusing needed for axially scan the sample and eventually producing a 3D stack of intensity images. Moreover, the partially coherent illumination avoids speckle noise, which plagues the C-ODT imaging methods. This technique has been developed for optically weak and almost non-absorbing objects that meet the conditions of the first Born approximation. We experimentally demonstrate the capability of the proposed technique by recovering the 3D refractive index distribution of biological samples such as blood cells and diatoms. The results are similar to those obtained by the C-ODT but using a simplified reconstruction process and a refocusing module that can be easily included in commercial widefield microscopes.