Towards distortion based underwater domed viewport camera calibration
Eduardo Iscar · M. Johnson-Roberson
TL;DR
Calibrates an underwater camera inside a spherical dome by using the point spread function and measured distortion to recover its pose, even with blur.
BRIEF
Underwater cameras sit behind a glass housing, and refraction at that interface bends light rays so standard camera models produce systematic errors. The problem worsens when the camera is placed far from the center of a spherical dome, because the offset amplifies refraction and blurs the image, which breaks the feature detectors that existing calibration methods depend on. This work describes the optical system with its point spread function and recovers the camera's pose inside the dome from measured distortions. Tests on a collected dataset show the pose is recovered with high accuracy.
Abstract
Photogrammetry techniques used for 3D reconstructions and motion estimation from images are based on projective geometry that models the image formation process. However, in the underwater setting, refraction of light rays at the housing interface introduce non-linear effects in the image formation. These effects produce systematic errors if not accounted for, and severely degrade the quality of the acquired images. In this paper, we present a novel approach to the calibration of cameras inside spherical domes with large offsets between dome and camera centers. Such large offsets not only amplify the effect of refraction, but also introduce blur in the image that corrupts feature extractors used to establish image-world correspondences in existing refractive calibration methods. We propose using the point spread function (PSF) as a complete description of the optical system and introduce a procedure to recover the camera pose inside the dome based on the measurement of the distortions. Results on a collected dataset show the method is capable of recovering the camera pose with high accuracy.