关于散射成像研究现状的一些思考（特邀）

透过散射介质的光学成像是人们长期追求但一直未能真正解决的问题。研究人员提出并发展了各种各样的方法和技术，从最早只利用弹道光的时间门和空间门技术，到后来利用了散射光的波前整形、散射矩阵测量和散斑自相关成像，再到近年热门的深度学习方法。尽管这些方法和技术都经过了毛玻璃、氧化锌薄膜、生物组织切片等薄散射介质的原理性验证，但随着介质厚度增加，所有方法和技术都迅速失效。厚度一直是难以克服的瓶颈。这篇评论归纳对比了散射成像的主要方法和技术，重新审视了经过散射介质波前被完全随机化等主流观点，分析了现有方法和技术无法透过厚散射介质成像的原因，并提出了未来有望真正解决问题的研究方向。

Some thoughts about the current research situation of imaging through scattering media (invited)

Optical imaging through scattering media is a long pursued yet unresolved problem. Researchers propose and develop kinds of methods and techniques, from the earliest time gating and spatial filtering techniques, which utilize only ballistic photons, to subsequent wavefront shaping, scattering matrix measurement and speckle autocorrelation imaging by taking advantage of scattered photons, to the popular deep learning methods latterly. Although all methods and techniques are verified by proof-of-concept experiments with thin scattering media, such as diffusers, zinc oxide layers and slices of biological tissue, they all fail rapidly as the thickness increases. The longstanding thickness challenge is still a bottleneck. In the commentary, I summarized and compared the methods and techniques in the field, reviewed the mainstream viewpoints, i.e., wavefront is completely scrambled after scattering media, analyzed the reason for the failure of existing methods and techniques through thick scattering media, and discussed the potential research directions to solve the problem ultimately in future.