中心挡板对扫描相干X射线衍射成像的影响

本文采用重叠关联迭代引擎算法, 系统地模拟研究了扫描相干衍射成像中中心挡板导致的低频信号丢失对重建图像质量的影响. 结果表明, 扫描相干衍射成像对中心挡板的承受能力远大于平面波单次相干衍射成像, 且选择小尺寸入射探针和较高重叠度(≥ 70%)可进一步降低中心丢失信号对扫描相干衍射成像的负面影响. 另外, 光斑扫描位置误差在重叠度较高时将超过中心挡板成为扫描相干衍射成像最主要的负面影响因素. 本文研究结果对扫描相干衍射成像实验中如何应用中心挡光板具有重要的指导意义, 将有助于进一步提高扫描相干衍射成像的分辨率. 关键词： 扫描相干衍射成像 位相恢复算法 低频丢失信号

Influence of central beamstop on ptychographic coherent diffractive imaging

A beamstop is commonly used in coherent diffractive imaging (CDI) experiments to collect more high-angle diffraction signals. But it causes the low-frequency signals missed, which can make CDI reconstruction unstable or even fail. In this work, a systematic simulation investigation of the effects of the missing low-frequency signals on the quality of reconstructed images of ptychographic CDI (PCDI) is performed using the ptychographic iterative engine algorithm. We found that the robustness of PCDI to the beamstop is much higher than that of the plane-wave CDI, and a smaller incident probe or a larger probe overlap ratio (≥ 70%) can further decrease the negative influence of missing low-freqency signals on the reconstruction image. The probe scanning position error will be the main degrading factor of PCDI instead of the beamstop in the higher overlap cases, and needs to be corrected in experiments by using high precision motors or adopting the position refinement algorithms. Our results provide quantitative guidelines for the usage of beamstops in ptychographic CDI experiments.
Keywords： ptychographic coherent diffractive imaging phase retrieval algorithm low-frequency signal missing