Phase-unwrapping-free and iterative reconstruction methods for propagated refractive index tomography

Abstract

Phase-unwrapping-free and iterative reconstruction methods for propagated refractive index (RI) tomography, which introduces lightwave back-propagation to a filtered back-projection method, are proposed. The phase-unwrapping-free method utilizes phase retrieval using a transport-of-intensity equation that does not require phase unwrapping. This method overcomes phase unwrapping problems of high calculation cost and phase unwrapping error when measuring millimeter-thick and/or large-RI-changes specimens. In the iterative method, a simultaneous iterative reconstruction technique in X-ray computed tomography is applied to the propagated RI tomography. This method leads to the reduction of the radial artifacts and the elimination of the need for a high-pass filter regardless of the shape and size of specimens. Hence, the accuracy of a reconstructed RI map is improved. Numerical simulations and optical experiments are carried out to prove the feasibility of the proposed methods.