Department of Electrical and Computer Engineering, The University of Memphis, Memphis, Tennessee, United States of America.
School of Applied Sciences and Engineering, Universidad EAFIT, Medellin, Colombia.
PLoS One. 2023 Sep 8;18(9):e0291103. doi: 10.1371/journal.pone.0291103. eCollection 2023.
Quantitative phase imaging (QPI) via Digital Holographic microscopy (DHM) has been widely applied in material and biological applications. The performance of DHM technologies relies heavily on computational reconstruction methods to provide accurate phase measurements. Among the optical configuration of the imaging system in DHM, imaging systems operating in a non-telecentric regime are the most common ones. Nonetheless, the spherical wavefront introduced by the non-telecentric DHM system must be compensated to provide undistorted phase measurements. The proposed reconstruction approach is based on previous work from Kemper's group. Here, we have reformulated the problem, reducing the number of required parameters needed for reconstructing phase images to the sensor pixel size and source wavelength. The developed computational algorithm can be divided into six main steps. In the first step, the selection of the +1-diffraction order in the hologram spectrum. The interference angle is obtained from the selected +1 order. Secondly, the curvature of the spherical wavefront distorting the sample's phase map is estimated by analyzing the size of the selected +1 order in the hologram's spectrum. The third and fourth steps are the spatial filtering of the +1 order and the compensation of the interference angle. The next step involves the estimation of the center of the spherical wavefront. An optional final optimization step has been included to fine-tune the estimated parameters and provide fully compensated phase images. Because the proper implementation of a framework is critical to achieve successful results, we have explicitly described the steps, including functions and toolboxes, required for reconstructing phase images without distortions. As a result, we have provided open-access codes and a user interface tool with minimum user input to reconstruct holograms recorded in a non-telecentric DHM system.
基于数字全息显微镜（DHM）的定量相位成像（QPI）已广泛应用于材料和生物领域。DHM 技术的性能严重依赖于计算重建方法，以提供准确的相位测量。在 DHM 成像系统的光学配置中，非远心成像系统最为常见。然而，非远心 DHM 系统引入的球面波前必须得到补偿，以提供无失真的相位测量。所提出的重建方法基于 Kemper 小组的先前工作。在这里，我们重新制定了问题，将重建相位图像所需的参数数量减少到传感器像素尺寸和光源波长。所开发的计算算法可以分为六个主要步骤。第一步，在全息图光谱中选择+1 级衍射。从所选的+1 级衍射中获得干涉角。其次，通过分析全息图光谱中所选+1 级的大小，估计球面波前弯曲，从而扭曲样品的相位图。第三步和第四步是对+1 级进行空间滤波和干涉角补偿。下一步是估计球面波前的中心。可选的最后一步优化用于微调估计参数并提供完全补偿的相位图像。由于正确实施框架对于获得成功的结果至关重要，因此我们已经明确描述了重建无失真相位图像所需的步骤，包括函数和工具箱。因此，我们提供了公开访问的代码和一个具有最小用户输入的用户界面工具，用于重建在非远心 DHM 系统中记录的全息图。
