Many underwater robotic applications relying on vision sensors require proper camera calibration, i.e. knowing the incoming light ray for each pixel in the image. While for the ideal pinhole camera model all viewing rays intersect in a single 3D point, underwater cameras suffer from - possibly multiple - refractions of light rays at the interfaces of water, glass and air. These changes of direction depend on the position and orientation of the camera inside the water-proof housing, as well as on the shape and properties of the optical window, the port, itself. In recent years explicit models for underwater vision behind common ports such as flat or dome port have been proposed, but the underwater community is still lacking a calibration tool which can determine port parameters through refractive calibration. With this work we provide the first open source implementation of an underwater refractive camera calibration toolbox. It allows end-to-end calibration of underwater vision systems, including camera, stereo and housing calibration for systems with dome or flat ports. The implementation is verified using rendered datasets and real-world experiments.

翻译：许多依赖视觉传感器的水下机器人应用需要进行适当的相机标定，即获取图像中每个像素对应的入射光线方向。在理想针孔相机模型中，所有视线均相交于单一三维点，而水下相机则受到光线在水、玻璃和空气界面处可能发生的多次折射影响。这些方向变化取决于相机在防水壳内的位置与朝向，以及光学窗口（即观察窗）自身的形状与特性。近年来，针对平面观察窗或穹顶观察窗等常见结构的水下视觉显式模型已被提出，但水下研究领域仍缺乏能够通过折射标定确定观察窗参数的工具。本研究首次提供了开源的水下折射相机标定工具箱实现。该工具支持对穹顶或平面观察窗系统的相机、立体视觉及防水壳进行端到端标定。通过渲染数据集与真实场景实验验证了该实现的可靠性。