4.7 Article

Refractive geometry for underwater domes

期刊

出版社

ELSEVIER
DOI: 10.1016/j.isprsjprs.2021.11.006

关键词

Underwater camera; Dome port; Refraction; Spherical refractive geometry; Calibration; Decentering

资金

  1. German Research Foundation (Deutsche For-schungsgemeinschaft, DFG) [396311425]
  2. Chinese Scholarship Council (CSC)

向作者/读者索取更多资源

Underwater cameras are often protected by spherical glass windows, which can withstand high water pressures and provide a large field of view without distortion. However, aligning the lens perfectly with the center of the dome is challenging and can result in refraction patterns that affect the accuracy of the camera. This study presents a non-iterative method to compute the center of refraction and a calibration procedure to estimate lens decentering.
Underwater cameras are typically placed behind glass windows to protect them from the water. Spherical glass, a dome port, is well suited for high water pressures at great depth, allows for a large field of view, and avoids refraction if a pinhole camera is positioned exactly at the sphere's center. Adjusting a real lens perfectly to the dome center is a challenging task, both in terms of how to actually guide the centering process (e.g. visual servoing) and how to measure the alignment quality, but also, how to mechanically perform the alignment. Consequently, such systems are prone to being decentered by some offset, leading to challenging refraction patterns at the sphere that invalidate the pinhole camera model. We show that the overall camera system becomes an axial camera, even for thick domes as used for deep sea exploration and provide a non-iterative way to compute the center of refraction without requiring knowledge of exact air, glass or water properties. We also analyze the refractive geometry at the sphere, looking at effects such as forward-vs. backward decentering, isorefraction curves and obtain a 6th-degree polynomial equation for forward projection of 3D points in thin domes. We then propose a pure underwater calibration procedure to estimate the decentering from multiple images. This estimate can either be used during adjustment to guide the mechanical position of the lens, or can be considered in photogrammetric underwater applications.

作者

我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。

评论

主要评分

4.7
评分不足

次要评分

新颖性
-
重要性
-
科学严谨性
-
评价这篇论文

推荐

暂无数据
暂无数据