实现用于扫描氦显微镜（SHeM）的光度立体视觉以重建原尺寸3D表面
Implementing photometric stereo for scanning helium microscopy (SHeM) to reconstruct true-to-size 3D surfaces
AI总结：
本论文提出一种名为“氦度立体视觉”的3D成像模式，通过改进光度立体视觉算法实现扫描氦显微镜（SHeM）的原尺寸3D表面重建，并开发了多探测器仪器B-SHeM与GPU加速蒙特卡洛光线追踪框架，显著提升了模拟性能。
摘要：
扫描氦显微镜（SHeM）通过针孔准直的热能中性氦-4原子束提供空间和角度分辨率的组合，用于无损成像。本论文引入了一种新颖的3D成像模式“氦度立体视觉”，利用改进的光度立体视觉算法实现原尺寸3D表面重建。由于传统机械加工的局限性，探索了用于SHeM针孔板的立体光固化（SLA）3D打印塑料。通过SLA打印的FormLabs“Clear Resin”被证明是真空组件快速成型的理想选择，所开发的烘烤方案确保了真空兼容性。研究表明，此类塑料的重新润湿是一个持续数周的表面过程。为单探测器和多探测器装置开发3D图像重建需要一种实空间点跟踪方法。该点跟踪方法促进了各种材料（包括技术晶体和生物晶体）的小面角度测量。它现已成为SHeM成像协议中样品机械手调试不可或缺的一部分。论文还详细介绍了一种多探测器SHeM仪器，称为B-SHeM。虽然主要为执行氦度立体视觉重建而设计，但该仪器也支持一系列新颖的SHeM实验，例如用于研究非弹性散射的混合物种束。本工作中实现的氦度立体视觉方法推动了内部基于蒙特卡洛的光线追踪框架GPU加速版本的开发，该框架是SHeM图像分析的事实标准。GPU并行化被探索作为一种减少模拟时间并实现以前无法实现的涉及复杂散射分布和高分辨率真实样品几何形状模拟的方法。在类似问题上的初步测试产生了高达380倍的潜在性能提升。
英文摘要：
Scanning Helium Microscopy (SHeM) offers a combination of spatial and angular resolution via a pinhole-collimated beam of thermal energy, neutral helium-4 atoms for non-destructive imaging. This thesis introduces a novel 3D imaging mode, "heliometric stereo", enabling true-to-size 3D surface reconstruction using an adapted photometric stereo algorithm. Stereolithography (SLA) 3D printed plastics are explored for SHeM pinhole plates due to limitations in traditional machining. FormLabs "Clear Resin" via SLA printing proves ideal for rapid prototyping of vacuum components, with a developed baking protocol ensuring vacuum compatibility. The study indicates re-wetting of such plastics is a surface process over weeks. Developing 3D image reconstruction for both single and multi-detector setups required a real-space point tracking method. The point tracking method facilitates facet angle measurement in various materials, including technological and biological crystals. It has since become integral to SHeM imaging protocols for sample manipulator debugging. The thesis also details a multi-detector SHeM instrument, referred to as B-SHeM. While primarily designed to perform heliometric stereo reconstructions, the instrument also enables the range of novel SHeM experiments such as mixed-species beams to investigate inelastic scattering. The heliometric stereo methods implemented in the work have motivated the development of a GPU accelerated version of the in-house Monte-Carlo based ray tracing framework, which is the de-facto standard for SHeM image analysis. GPU parallelisation was explored as a method for decreasing simulation time and enabling previously inaccessible simulations involving complex scattering distributions and high resolution, realistic sample geometries. Preliminary testing on an analogous problem yielded a potential performance increase of up to 380 times.
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