Electron ptychography is a 4-D STEM phase-contrast imaging technique with applications to light-element and beam-sensitive materials. Although the electron dose (electrons incident per unit area on the sample) is the primary figure of merit for imaging beam-sensitive materials, it is also necessary to consider the contrast transfer properties of the imaging technique. Here, we explore the contrast transfer properties of electron ptychography. The contrast transfer of focused-probe, non-iterative electron ptychography using the single-side-band (SSB) method is demonstrated experimentally. The band-pass nature of the phase-contrast transfer function (PCTF) for SSB ptychography places strict limitations on the probe convergence semi-angles required to resolve specific sample features with high contrast. The PCTF of the extended ptychographic iterative engine (ePIE) is broader than that for SSB ptychography, although when both high and low spatial frequencies are transferred, band-pass filtering is required to remove image artefacts. Normalisation of the transfer function with respect to the noise level shows that the transfer window is increased while avoiding noise amplification. Avoiding algorithms containing deconvolution steps may also increase the dose-efficiency of ptychographic phase reconstructions.

中文翻译：

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聚焦探针电子 ptychography 中的对比度转移和噪声考虑

电子 ptychography 是一种 4-D STEM 相衬成像技术，可应用于光元件和光束敏感材料。尽管电子剂量（样品上每单位面积入射的电子）是对光束敏感材料成像的主要品质因数，但也有必要考虑成像技术的对比度传递特性。在这里，我们探讨了电子 ptychography 的对比度转移特性。实验证明了使用单边带 (SSB) 方法的聚焦探针、非迭代电子 ptychography 的对比度转移。SSB ptychography 的相位对比传递函数 (PCTF) 的带通性质对解析具有高对比度的特定样本特征所需的探针会聚半角提出了严格的限制。扩展 ptychographic 迭代引擎 (ePIE) 的 PCTF 比 SSB ptychography 的 PCTF 更宽，尽管在传输高空间频率和低空间频率时，需要带通滤波以去除图像伪影。传递函数相对于噪声电平的归一化表明传递窗口增加同时避免噪声放大。避免包含解卷积步骤的算法也可以提高 ptychographic 相位重建的剂量效率。