In this paper, we propose an improved deterministic regularization algorithm to handle the sparse angle data problem in optical diffraction tomography. Based on optical diffraction tomography and the deterministic regularization algorithm, the regularization iteration is performed in the space domain and the frequency domain simultaneously, which greatly reduces the computational cost. By applying piecewise-smoothness and positivity constraints as the penalty function, the missing frequency spectrum is effectively recovered and the internal refractive index distribution of the specimen is accurately reconstructed. Using simulated and experimental results, we show that the proposed regularization algorithm allows accurate refractive index reconstruction from very sparse angle data in optical diffraction tomography.

In this paper, we report the experimental implementation of handling the reconstruction problem from few angle data-sets for digital holographic microtomography. First, the digital holographic microscopy with sample-rotating scheme is established and few holograms with regularly spaced angle steps are recorded. Then, an algebraic iterative reconstruction algorithm with non-positivity constraint and a smoothing operator is applied to reconstruct three-dimensional refractive index distribution of the measured sample from the few angle data-sets. The experimental results demonstrate that the algebraic iterative technique can accurately reconstruct refractive index distribution from few angle data-sets in digital holographic microtomography. The technique is easy to implement and reduces greatly the required recording times.

In optical diffraction tomography with specimen rotation,the set of captured frequencies exhibits a missing space called missing apple core,an algorithm,in which Fourier mapping algorithm was combined with iterative constraint algorithm,was proposed to acquire the missing frequencies and reconstruct a high-resolution refractive index map.First,based on the theory of digital holographic microtomography with sample rotation,the experiment system was set up and the digital holograms were acquired at regularly-spaced angular positions within 360°viewing angle.Then,the complex field images were calculated from the holograms.Last,the high-resolution three-dimensional refractive index map was reconstructed by the proposed algorithm.The experimental results demonstrate that the algorithm is feasible and effective for acquiring the missing apple core frequencies and achieving the high-resolution three-dimensional refractive index distribution.

提出了一种定量测量光纤内部折射率三维分布的新方法.基于数字全息显微断层成像技术,构建了一套测量光纤折射率的实验系统,实现了光纤内部折射率分布的三维测量.在预放大透射式数字全息显微系统中,加入样品转动装置,利用样品转动记录180°视角内各个角度的显微全息图,然后数值计算出每个角度光纤样品的折射率积分投影,并基于滤波反投影算法重建光纤内部折射率的三维分布.普通单模光纤和熊猫型保偏光纤两组样品的实验结果表明:建立的系统可应用于光纤内部折射率三维分布定量测量.