Dora Johannes, Möddel Martin, Flenner Silja, Schroer Christian G, Knopp Tobias, Hagemann Johannes
Opt Express. 2024 Mar 25;32(7):10801-10828. doi: 10.1364/OE.514641.
The phase problem is a well known ill-posed reconstruction problem of coherent lens-less microscopic imaging, where only the squared magnitude of a complex wavefront is measured by a detector while the phase information of the wave field is lost. To retrieve the lost information, common algorithms rely either on multiple data acquisitions under varying measurement conditions or on the application of strong constraints such as a spatial support. In X-ray near-field holography, however, these methods are rendered impractical in the setting of time sensitive in situ and operando measurements. In this paper, we will forego the spatial support constraint and propose a projected gradient descent (PGD) based reconstruction scheme in combination with proper preprocessing and regularization that significantly reduces artifacts for refractive reconstructions from only a single acquired hologram without a spatial support constraint. We demonstrate the feasibility and robustness of our approach on different data sets obtained at the nano imaging endstation of P05 at PETRA III (DESY, Hamburg) operated by Helmholtz-Zentrum Hereon.
相位问题是相干无透镜显微成像中一个众所周知的不适定重建问题，在这种成像中，探测器仅测量复波前的平方模，而波场的相位信息丢失。为了恢复丢失的信息，常用算法要么依赖于在不同测量条件下的多次数据采集，要么依赖于诸如空间支撑等强约束的应用。然而，在X射线近场全息术中，这些方法在时间敏感的原位和操作测量环境中变得不切实际。在本文中，我们将放弃空间支撑约束，并提出一种基于投影梯度下降（PGD）的重建方案，结合适当的预处理和正则化，该方案可显著减少仅从单个无空间支撑约束的采集全息图进行折射重建时的伪影。我们在由亥姆霍兹-赫伦中心运营的位于PETRA III（德国汉堡DESY）的P05纳米成像终端站上获得的不同数据集上证明了我们方法的可行性和鲁棒性。
