Abstract:
As a label-free, non-destructive, high-resolution, and quantitative imaging technique, optical diffraction tomography (ODT) has been widely used to image biological samples and microstructures, such as cells, tissues, and optical fibers. The refractive-index (RI) distribution of an object is reconstructed from multi-view diffracted fields emerging from the object. Typical ODT setups use the object rotating configuration (ORC) and the illumination scanning configuration (ISC). One major limitation of ODT is that it is only applicable to weakly-scattering objects. In this dissertation, novel methods have been developed to overcome multiple scattering, so as to extend ODT applications.
First, an iterative ODT (iODT) algorithm has been developed by reducing the differences between the forward- and backward-propagated fields through reconstructed object. The perturbative corrections to the reconstructed object are computed from the field discrepancies by use of the Rytov-based inversion. iODT can be directly applied to ORC and can be extended to ISC through normalization using an appropriate coherent transfer function. Both simulation and experimental results demonstrate that iODT provides accurate and efficient reconstructions of multiply-scattering phase objects with high RI contrasts, large optical path-length differences (OPDs), and/or complicated structures. Furthermore, with the same prior knowledge, iODT also outperforms ODT in resolving the missing-angle problem, in terms of convergence and reconstruction quality.
For imaging multiply-scattering objects with complex RI distributions, iODT is prone to artifacts because of the crosstalk between the real and imaginary parts of the RI. An error subtraction (ES) method has been developed, serving as an add-on module to iODT, to simultaneously reconstruct the RI and the absorption/gain distributions of multiply-scattering objects.
Finally, we have explored the complementarity of iODT and optimization-based ODT in terms of their advantages and disadvantages, and proposed a combined strategy – iODT initialization for optimization-based ODT. Because the perturbative corrections in iODT replies on the Rytov-based inversion instead of a numerical gradient method, iODT has a physics-based component that avoids being trapped in local minima. Numerical results demonstrate that the reconstruction only under this combined strategy can accurately converge to the global minimum, especially for multiply-scattering objects with large OPDs.
Major: Optics and Photonics
Educational Career:
BS: 2014, Optical Science and Technology, Harbin Institute of Technology
MS: 2020, Optics & Photonics, College of Optics and Photonics, University of Central Florida
Committee in Charge:
Dr. Guifang Li (Chair)
Dr. Bahaa Saleh (Co-Chair)
Dr. Shuo Pang
Dr. Alexander Katsevich
Approved for distribution by Dr. Guifang Li, Committee Chair, on November 5, 2020.
The public is welcome to attend.
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Topic: FINAL DISSERTATION AND DEFENSE ANNOUNCEMENT: Shengli Fan
Time: Nov 18, 2020 02:00 PM Eastern Time (US and Canada)
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