Quantification of three-dimensional (3D) refractive index (RI) with sub-cellular resolution is achieved by digital holographic microtomography (DHμT) using quantitative phase images measured at multiple illumination angles. The DHμT system achieves sensitive and fast phase measurements based on iterative phase extraction algorithm and asynchronous phase shifting interferometry without any phase monitoring or active control mechanism. A reconstruction algorithm, optical diffraction tomography with projection on convex sets and total variation minimization, is implemented to substantially reduce the number of angular scattered fields needed for reconstruction without sacrificing the accuracy and quality of the reconstructed 3D RI distribution. Tomogram of a living CA9-22 cell is presented to demonstrate the performance of the method. Further, a statistical analysis of the average RI of the nucleoli, the nucleus excluding the nucleoli and the cytoplasm of twenty CA9-22 cells is performed.
Image reconstruction from limited-angle data is an important issue in diffraction tomography. The limitation of angular coverage usually occurs due to the physical constraints in measurement systems. Insufficient information will deteriorate the quality of reconstructed images. In our experimental setup, the angular range of the data scanning is limited. Here, we applied the iterative algorithm of total variation (TV) minimization to reconstruct the three-dimensional distribution of an object's refractive index from measured phase data. TV-minimization is an edge-preserving technique commonly used in image processing. It can smooth away the noisy textures while retaining sharp edges. Despite a full range of illumination is lacking, we have successfully reconstructed the refractive index distribution of objects numerically and experimentally by use of the TV-minimization algorithm.
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