The exploration of oceans using autonomous underwater vehicles (AUVs) is necessary for activities, such as the sustainable management of fishery resources, extraction of seafloor minerals and energy resources, and inspection of underwater infrastructure. As the next step in ocean exploration, AUVs are expected to employ end-effectors to make physical contact with seafloor creatures and materials. We propose a scenario for realizing a sampling mission using an AUV that is equipped to sample marine life. In this scenario, the sampling AUV observes the seafloor while concurrently transmitting the observed images to a surface vessel for inspection by the AUV operators. If the received images show an object of interest, the object is selected as a candidate of sampling target by the operators, who send a sampling command to the AUV. After receiving the command, the AUV returns to the target area and attempts to sample it. In this paper, we propose a system for transmitting images of the seafloor as part of the sampling-mission scenario. The proposed image transmission system includes a process for enhancing images of the deep seafloor, a process for selecting interesting images, and processes for compressing and reconstructing images. The image enhancement process resolves imaging problems resulting from light attenuation, such as color attenuation and uneven illumination. The process for selecting interesting images selects those that contain interesting objects, such as marine life. The selection process prevents the transmission of meaningless images that contain only flat sand on the seafloor. The proposed image compression method, which is based on color depth compression, reduces the amount of data. The combined process of selecting an interesting image and compressing it reduces various problems in acoustic communication, such as low information density and data loss. Instead of an overall image, part of an overall image is transmitted by a set of data packet, and each received data packet is reconstructed onboard the vessel. Because of image compression, the colors of a reconstructed image differ from those of an enhanced image. However, the reconstructed image contains similar colors, and the structural similarity index was found to be 91.4% by evaluating images that were subjected to a 4-b color compression. The proposed image transmission system was tested in the Sea of Okhotsk, and these tests were performed four times in different sea areas (minimum depth 380 m, maximum depth 590 m). The results show that the size of the data for a single image was reduced by a factor of 18 using the proposed image compression process, with each image taking 3.7 s to be transmitted via an acoustic modem (20 kb/s). Of the automatically selected images, 63% contained marine life, and the total transmission success rate was 22%.

中文翻译：

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一种用于使用自主水下航行器进行深海生物采样任务的光学图像传输系统

使用自主水下航行器 (AUV) 探索海洋对于渔业资源的可持续管理、海底矿物和能源资源的开采以及水下基础设施的检查等活动是必要的。作为海洋探索的下一步，AUV 有望使用末端执行器与海底生物和材料进行物理接触。我们提出了一种使用配备对海洋生物进行采样的 AUV 来实现采样任务的方案。在这种情况下，采样 AUV 观察海底，同时将观察到的图像传输到水面船只以供 AUV 操作员检查。如果接收到的图像显示感兴趣的对象，则操作员将该对象选为采样目标的候选对象，操作员向 AUV 发送采样命令。AUV收到命令后，返回目标区域并尝试对其进行采样。在本文中，我们提出了一种传输海底图像的系统，作为采样任务场景的一部分。所提出的图像传输系统包括用于增强深海底图像的过程、用于选择感兴趣图像的过程以及用于压缩和重建图像的过程。图像增强过程解决了由光衰减引起的成像问题，例如颜色衰减和光照不均匀。选择有趣图像的过程会选择那些包含有趣对象（例如海洋生物）的图像。选择过程可防止传输仅包含海底平坦沙子的无意义图像。提出的图像压缩方法，它基于颜色深度压缩，减少了数据量。选择有趣的图像并对其进行压缩的组合过程减少了声学通信中的各种问题，例如信息密度低和数据丢失。代替整体图像，整体图像的一部分由一组数据包传输，并且每个接收到的数据包在船上重建。由于图像压缩，重建图像的颜色与增强图像的颜色不同。然而，重建的图像包含相似的颜色，通过评估经过 4-b 颜色压缩的图像，发现结构相似指数为 91.4%。所提出的图像传输系统在鄂霍次克海进行了测试，这些测试在不同海域（最小深度 380 m，最大深度 590 m）。结果表明，使用所提出的图像压缩过程，单个图像的数据大小减少了 18 倍，每张图像需要 3.7 秒才能通过声学调制解调器 (20 kb/s) 传输。在自动选择的图像中，63% 包含海洋生物，总传输成功率为 22%。