In a focused ion beam (FIB) microscope, source particles interact with a small volume of a sample to generate secondary electrons that are detected, pixel by pixel, to produce a micrograph. Randomness of the number of incident particles causes excess variation in the micrograph, beyond the variation in the underlying particle-sample interaction. We recently demonstrated that joint processing of multiple time-resolved measurements from a single pixel can mitigate this effect of source shot noise in helium ion microscopy. This paper is focused on establishing a rigorous framework for understanding the potential for this approach. It introduces idealized continuous- and discrete-time abstractions of FIB microscopy with direct electron detection and estimation-theoretic limits of imaging performance under these measurement models. Novel estimators for use with continuous-time measurements are introduced and analyzed, and estimators for use with discrete-time measurements are analyzed and shown to approach their continuous-time counterparts as time resolution is increased. Simulated FIB microscopy results are consistent with theoretical analyses and demonstrate that substantial improvements over conventional FIB microscopy image formation are made possible by time-resolved measurement.

中文翻译：

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时间分辨聚焦离子束显微镜：建模、估计方法和分析


在聚焦离子束 (FIB) 显微镜中，源粒子与少量样品相互作用，产生二次电子，逐个像素地检测二次电子，从而生成显微照片。入射粒子数量的随机性导致显微照片中的过度变化，超出了潜在粒子-样品相互作用的变化。我们最近证明，对单个像素的多个时间分辨测量进行联合处理可以减轻氦离子显微镜中源散粒噪声的影响。本文的重点是建立一个严格的框架来理解这种方法的潜力。它引入了 FIB 显微镜的理想化连续和离散时间抽象，以及这些测量模型下成像性能的直接电子检测和估计理论限制。介绍并分析了用于连续时间测量的新型估计器，分析了用于离散时间测量的估计器，并表明随着时间分辨率的提高，估计器可以接近连续时间的估计器。模拟 FIB 显微镜结果与理论分析一致，并表明通过时间分辨测量可以实现对传统 FIB 显微镜图像形成的实质性改进。