Differential dynamic microscopy (DDM) is a technique that exploits optical microscopy to obtain local, multi-scale quantitative information about dynamic samples, in most cases without user intervention. It is proving extremely useful in understanding dynamics in liquid suspensions, soft materials, cells, and tissues. In DDM, image sequences are analyzed via a combination of image differences and spatial Fourier transforms to obtain information equivalent to that obtained by means of light scattering techniques. Compared to light scattering, DDM offers obvious advantages, principally (a) simplicity of the setup; (b) possibility of removing static contributions along the optical path; (c) power of simultaneous different microscopy contrast mechanisms; and (d) flexibility of choosing an analysis region, analogous to a scattering volume. For many questions, DDM has also advantages compared to segmentation/tracking approaches and to correlation techniques like particle image velocimetry. The very straightforward DDM approach, originally demonstrated with bright field microscopy of aqueous colloids, has lately been used to probe a variety of other complex fluids and biological systems with many different imaging methods, including dark-field, differential interference contrast, wide-field, light-sheet, and confocal microscopy. The number of adopting groups is rapidly increasing and so are the applications. Here, we briefly recall the working principles of DDM, we highlight its advantages and limitations, we outline recent experimental breakthroughs, and we provide a perspective on future challenges and directions. DDM can become a standard primary tool in every laboratory equipped with a microscope, at the very least as a first bias-free automated evaluation of the dynamics in a system.

中文翻译：

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透视图：差分动态显微镜提取复杂流体和生物系统中的多尺度活性

差分动态显微镜（DDM）是一种利用光学显微镜来获取有关动态样品的局部，多尺度定量信息的技术，在大多数情况下，无需用户干预。事实证明，它对于理解液体悬浮液，软质材料，细胞和组织中的动力学非常有用。在DDM中，通过图像差异和空间傅立叶变换的组合来分析图像序列，以获得与通过光散射技术获得的信息等效的信息。与光散射相比，DDM具有明显的优势，主要是（a）设置简单；（b）消除沿光路的静电影响的可能性；（c）同时使用不同的显微镜对比机制的力量；（d）选择分析区域的灵活性，类似于散射体积。对于许多问题，与分段/跟踪方法以及诸如粒子图像测速仪之类的相关技术相比，DDM还具有优势。最初由水性胶体的明场显微镜证明的一种非常简单的DDM方法，最近已用于通过许多不同的成像方法来探测各种其他复杂的流体和生物系统，包括暗场，差分干涉对比，宽场，光片和共聚焦显微镜。采用组的数量正在迅速增加，应用程序也在迅速增加。在这里，我们简要回顾一下DDM的工作原理，重点介绍DDM的优点和局限性，概述近期的实验性突破，并就未来的挑战和方向提供了一个观点。