Optical diffraction tomography: a resolution study

In the past years, optical diffraction tomography (ODT) has been used both in cell imaging and to investigate the three-dimensional refractive index (RI) of large-scale (millimetre-sized) samples. In this technique, the projections at different illumination angles are acquired through digital holography (DH) and used to estimate the complex wave fields, which can be refocused with the aid of numerical diffraction algorithms. However, real extended specimens may not completely lie on a single plane. In this case, the (refocused) projections retain a certain amount of defocus which will affect the tomographic reconstruction. For this reason, this thesis aims to study the spatial resolution of an ODT system when a point-like object is allowed to go in and out of focus and is reconstructed without numerical refocusing. Two-dimensional rotation and computational Fourier optics will be used to track and model defocus and lenses during the simulation of the projections. Spatial resolution will be assessed both qualitatively and quantitatively by numerically computing the full width at half maximum (FWHM) in relation to the maximum defocus to which a simulated point was subjected during acquisition. Lastly, deconvolution is used to remove unwanted blur.