Optical diffraction tomography in the multiple scattering regime

This Thesis work has been conducted at Institut Fresnel in Marseille in the Erasmus Internship context. I have been part of the SEMO (Sondage Electromagnétique en Micro-onde et Optique) team with the aim of reconstructing 2D samples. In order to do that I had to both become familiar with the physics involved in the process, as well as getting to understand the inversion algorithm which has been developed at Institut Fresnel. In the second part of my six months internship I concentrated on the development of the experimental setup which I used to perform several acquisitions of 2D samples made of germanium rods deposited on a glass substrate. After performing several acquisitions, I had to perform a first data treatment in order to prepare the recorded diffraction patterns for the final inversion procedure. As the last step of my work I had to perform the inversion procedure by using a FORTRAN-based tool, developed at Institut Fresnel and which made it possible to obtain a good reconstruction for my 2D samples.

In questo elaborato di Tesi verrà descritto il modello di un microscopio ottico che utilizza una tecnica di imaging innovativa: la tomografia ottica a diffrazione (ODT, Optical Diffraction Tomography), che permette di ottenere risoluzioni che vanno ben oltre il criterio di Rayleigh. Al di là dell‟informazione qualitativa legata alla ricostruzione tridimensionale, questo metodo nasce anche con la finalità di ricavare informazioni quantitative, come ad esempio la mappa di permittività del campione. Alla base vi sono le tecniche legate alla microscopia di fase, all‟olografia digitale e alla sintesi d‟apertura.