Significance: Diffuse light is ubiquitous in biomedical optics and imaging. Understanding the process of migration of an initial photon population entering tissue to a completely randomized, diffusely scattered population provides valuable insight to the interpretation and design of optical measurements. Aim: The goal of this perspective is to present a brief, unifying analytical framework to describe how properties of light transition from an initial state to a distributed state as light diffusion occurs. Approach: First, measurement parameters of light are introduced, and Monte Carlo simulations along with a simple analytical expression are used to explore how these individual parameters might exhibit diffusive behavior. Second, techniques to perform optical measurements are considered, highlighting how various measurement parameters can be leveraged to subsample photon populations. Results: Simulation results reinforce the fact that light undergoes a transition from a non-diffuse population to one that is first subdiffuse and then fully diffuse. Myriad experimental methods exist to isolate subpopulations of photons, which can be broadly categorized as source- and/or detector-encoded techniques, as well as methods of tagging the tissue of interest. Conclusions: Characteristic properties of light progressing to diffusion can be described by some form of Gaussian distribution that grows in space, time, angle, wavelength, polarization, and coherence. In some cases, these features can be approximated by simpler exponential behavior. Experimental methods to subsample features of the photon distribution can be achieved or theoretical methods can be used to better interpret the data with this framework.

中文翻译：

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组织中漫射光的透视：子采样光子群

意义：漫射光在生物医学光学和成像中无处不在。了解进入组织的初始光子群体迁移到完全随机、漫散射的群体的过程为光学测量的解释和设计提供了宝贵的见解。目的：这个视角的目标是提出一个简短的、统一的分析框架来描述光的属性如何在发生光漫射时从初始状态转变为分布式状态。方法：首先，引入光的测量参数，并使用蒙特卡罗模拟和简单的分析表达式来探索这些单个参数如何表现出漫射行为。其次，考虑执行光学测量的技术，强调如何利用各种测量参数对光子种群进行子采样。结果：模拟结果强化了这样一个事实，即光经历了从非漫射种群到先是亚漫射然后完全漫射的过渡。存在无数的实验方法来隔离光子的亚群，这些方法可以广泛地归类为源和/或检测器编码技术，以及标记感兴趣组织的方法。结论： 光扩散的特性可以通过某种形式的高斯分布来描述，该分布在空间、时间、角度、波长、偏振和相干性上增长。在某些情况下，这些特征可以通过更简单的指数行为来近似。