Next Generation High-Speed Microplasma Three- Dimensional Imaging

这个项目的目标是首次探索用计算机显微镜研究电离气体，也就是等离子体。在过去的一个世纪里，科学家们对等离子体组成的宏观和微观系统进行了深入的研究。一段时间以来，实验室尺度等离子体的光学研究一直由几种知名技术主导，而新技术发展的停滞严重限制了使用光作为探针进行测量的信息获取。最近，新型的变革性显微镜在强大的计算机算法的帮助下制作图像，使得从物理系统中提取的信息量不断增加，即使收集的数据量相同。有了这些进步，现在可以用一个单一的短脉冲光在三维空间中成像物体的厚度或高度，以及它们的材料组成。该项目将使新的计算显微镜技术应用于微等离子体的研究。释放光的力量，将其作为一种非破坏性、非侵入性的探针，探测等离子体等恶劣环境，将对材料科学、粒子加速器和替代光源等多个领域产生直接影响，这些领域都是基于激光产生的等离子体。纹影成像、干涉成像、阴影成像和泽尼克相衬成像的基本限制是从解析计算中众所周知的。纹影成像是敏感的数量，这是有关的第一个，试样的折射率和阴影成像的方向导数可以产生的图像正比于折射率的二阶导数在某些近似。然而，这些信息本质上是定性的。干涉成像需要一个已知的参考，相对较小的相移，是相当敏感的振动；它还需要在参考波和询问波之间仔细定时，因此在实验上更复杂。暗影法是最简单的实验配置，但也是最复杂的分析方法；虽然泽尼克相位对比成像是一种优秀的技术，但它不能产生同时具有相位和振幅的无参考图像。只有相干计算成像能够产生定量的、单镜头的、无参考的图像，同时具有相位和幅度对比度——在一定的频率范围内，在三维空间中。这种能够探测等离子体的真正定量同时相位和振幅对比成像技术的发展有望对实验室等离子体的基础研究和应用研究产生革命性的影响。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The goal of this project is a first exploration of computational microscopy for the study of ionized gasses, called plasmas. Over the last century, scientists have intensely investigated macro- and microscopic systems composed of plasmas. Optical investigations of laboratory scale plasmas have been dominated by several well-known techniques for some time, and stagnation in development of new techniques has critically limited information accessible to measurements that use light as a probe. Recently, new and transformative microscopes that make images with assistance from powerful computer algorithms have led to an ever-increasing amount of information extracted from physical systems, even for the same amount of collected data. With these advances, it is now possible to image the thickness or height of objects, and their material composition all in three-dimensions using a single, short burst of light. This project will enable application of the new computational microscopy techniques to the study of microplasmas. Unlocking the power of light as a nondestructive, noninvasive probe of harsh environments like plasmas will have immediate impact on a variety of fields including material science, particle accelerators, and alternative light sources, all based on laser created plasmas.Fundamental limits of Schlieren imaging, imaging interferometry, shadowgraphy, and Zernike phase contrast imaging are well known from analytic calculations. Schlieren imaging is sensitive to a quantity that is related to the first, directional derivative of the specimen’s refractive index and shadowgraphy can produce images proportional to the second derivative of the refractive index under certain approximations. However, this information is qualitative in nature. Interferometric imaging requires a known reference, relatively small phase shifts, and is quite sensitive to vibrations; it also requires careful timing between the reference wave and the interrogating wave and is therefore more experimentally complicated. Shadowgraphy is the simplest experimental configuration but is the most complicated method to analyze; and while Zernike phase contrast imaging is an excellent technique, it is not capable of producing reference free images with simultaneous phase and amplitude. Only coherent computational imaging is capable of producing quantitative, single-shot, reference free images with simultaneous phase and amplitude contrast -- over a range of frequencies, in three-dimensions. The development of such truly quantitative simultaneous phase-and-amplitude contrast imaging technique capable of probing plasmas is expected to be transformative for both fundamental and applied studies of laboratory plasmas.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.