The challenges associated with acquiring the clear images of objects in underwater environment are difficult to overcome due to the absorptive and scattering nature of seawater. Recently, the research community has focused on mitigating these effects. The recent developments in image enhancement algorithms and strategies of signal light enhancement have brought improvement in some application areas. In this work, we review the six most common methods based on signal light enhancement. We present the individual working mechanisms, latest representative advances, and suitable application conditions. Moreover, we also present a detailed comparison of these techniques. In each technique, we present their applicable environments and conditions according to the following indicators: operating distance (from 2 attenuation lengths (AL) to 13.5 AL), resolution (from centimeter to millimeter), and field of view (FOV). By summarizing and analyzing the existing problems that restrict the underwater optical imaging techniques, the future development trends are prospected.

中文翻译：

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水下光学成像：关键技术及应用综述


由于海水的吸收和散射性质，在水下环境中获取物体的清晰图像所面临的挑战很难克服。最近，研究界致力于减轻这些影响。图像增强算法和信号光增强策略的最新发展在一些应用领域带来了改进。在这项工作中，我们回顾了基于信号光增强的六种最常见的方法。我们介绍了各自的工作机制、最新的代表性进展以及合适的应用条件。此外，我们还对这些技术进行了详细比较。在每种技术中，我们根据以下指标来展示其适用的环境和条件：工作距离（从2个衰减长度（AL）到13.5 AL）、分辨率（从厘米到毫米）和视场（FOV）。通过总结分析目前制约水下光学成像技术存在的问题，展望了未来的发展趋势。