扫描线圈延迟导致快速四维扫描透射电子显微镜（4D-STEM）出现各向异性信号损失
Scan-Coil Delay Causes Anisotropic Signal Loss in Fast 4D-STEM
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中文总结 AI 辅助
该研究针对快速4D-STEM中扫描线圈延迟导致的各向异性信号损失问题，提出基于相位相关的子帧对齐校正方法，可恢复宽空间频率信号，尤其适用于低剂量生物成像，无需修改显微镜即可实现信号恢复。
中文摘要 AI 辅助
快速像素探测器正推动4D-STEM的驻留时间达到微秒级，在此 regime 中，扫描偏转线圈的有限响应与驻留时间本身相当。我们利用直接探针成像和子帧衍射分析，记录到显著的驻留期内扫描线圈延迟，该延迟会沿快速扫描方向系统性地各向异性地模糊记录信号，其稳定时间尺度为数十微秒。我们提出一种基于相位相关的子帧对齐程序，用于测量和校正该模糊效应，并在一系列扫描步长上评估其对聚焦和散焦4D-STEM重构的影响。该校正可恢复宽空间频率范围内的信号，在低剂量生物成像所需的大步长下增益最大。由于该方法仅基于现有数据操作，无需修改显微镜，因此为恢复原本会因扫描线圈延迟而损失的信号提供了实用途径。
英文摘要
Fast pixelated detectors are driving 4D-STEM toward microsecond dwell times, a regime in which the finite response of the scan deflection coils becomes comparable to the dwell time itself. Using direct probe imaging and sub-frame diffraction analysis, we document a significant intra-dwell scan-coil delay that systematically smears the recorded signal anisotropically along the fast scan direction, with a settling timescale of several tens of microseconds. We present a phase-correlation-based sub-frame alignment procedure that measures and corrects this smearing, and we assess its impact on focused and defocused 4D-STEM reconstructions over a range of scan step sizes. The correction restores signal across a broad range of spatial frequencies, with the largest gains at the large step sizes required for low-dose biological imaging. Because it operates on existing data with no modification to the microscope, the method offers a practical route to recovering signal that would otherwise be lost to scan-coil delay.
