A Calibration Tool for Refractive Underwater Vision

2024-05-28

arXiv.org

AI Summary

To address calibration inaccuracies in underwater vision caused by refraction across water–glass–air interfaces, this paper introduces the first open-source underwater refractive camera calibration toolbox. The method employs explicit refractive geometric modeling and jointly optimizes intrinsic and extrinsic camera parameters along with physical parameters of the housing’s optical port—either a flat port or a spherical dome—enabling monocular, stereo, and end-to-end system-level calibration. Leveraging nonlinear optimization guided by synthetically rendered data, it achieves, for the first time, joint estimation of port parameters under strict physical model constraints. Extensive validation in both simulated and real underwater environments demonstrates significant improvements in calibration accuracy, leading to enhanced 3D reconstruction fidelity and visual navigation performance.

Technology Category

• Computer Vision: Low Level & Physics-based Vision
• Machine Learning: Calibration & Uncertainty Quantification
• Intelligent Robots: State Estimation

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Experiences and lessons learnt from Web-based algorithms and system deployments
• User Modeling, Personalization and Recommendation: On-Device user modeling, personalization, and recommendation
• Graph Algorithms and Modeling for the Web: Efficient manipulation of static and dynamic Web-related graphs

Abstract

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.

Problem

• Calibrating underwater cameras with refractive distortions
• Determining port parameters for underwater vision systems
• Providing open-source tool for end-to-end underwater calibration

Innovation

• Open source underwater refractive calibration toolbox
• End-to-end calibration for dome and flat ports
• Validated with rendered and real-world data