Omnidirectional Underwater Camera Design and Calibration

Abstract

This paper presents the development of an underwater omnidirectional multi-camera system (OMS) based on a commercially available six-camera system, originally designed for land applications. A full calibration method is presented for the estimation of both the intrinsic and extrinsic parameters, which is able to cope with wide-angle lenses and non-overlapping cameras simultaneously. This method is valid for any OMS in both land or water applications. For underwater use, a customized housing is required, which often leads to strong image distortion due to refraction among the different media. This phenomena makes the basic pinhole camera model invalid for underwater cameras, especially when using wide-angle lenses, and requires the explicit modeling of the individual optical rays. To address this problem, a ray tracing approach has been adopted to create a field-of-view (FOV) simulator for underwater cameras. The simulator allows for the testing of different housing geometries and optics for the cameras to ensure a complete hemisphere coverage in underwater operation. This paper describes the design and testing of a compact custom housing for a commercial off-the-shelf OMS camera (Ladybug 3) and presents the first results of its use. A proposed three-stage calibration process allows for the estimation of all of the relevant camera parameters. Experimental results are presented, which illustrate the performance of the calibration method and validate the approach.

Close-Range Tracking of Underwater Vehicles Using Light Beacons

“…For underwater cameras, the fact that the direction of the ray changes in every medium transition makes the process more laborious, as for each transition, the intersection point and the direction of the rays must be computed according to the laws of physics. For the sake of simplicity, the details are not described here, but can be found in [ 24 ].…”

Global Calibration of Multi-Cameras Based on Refractive Projection and Ray Tracing

“…Multi-cameras system (MCS) have many merits over single camera because they can cover a wider and overall field of view (FOV), which makes MCS increasingly prevalent in industrial vision measurement [1,2], visual navigation [3,4], security monitoring [5], etc. With the advantages of flexibility, cost performance and high precision, industrial vision measurement using MCS has been widely studied in many applications, such as car body-in-white inspections [6], deformation and displacement measurement [7,8].…”

A Global Calibration Method for Widely Distributed Cameras Based on Vanishing Features

“…Global calibration methods for DVS with overlapping FOV cannot be applied in the case of non-overlapping FOV. Most of the global calibration methods for DVS with non-overlapping FOV are based on mirror reflections [ 5 , 6 , 7 ], rigidity constraints of calibration targets [ 8 , 9 , 10 ], movements of the platform [ 11 ] and the auxiliary camera [ 12 ]. For general distributed vision sensors, it is hard to make sure that each camera has a clear sight of the targets through mirror reflections, especially in complex environments.…”

“…Liu et al [ 9 ] proposed a global calibration method by placing multiple targets in front of the vision sensors at least four times. Bosch et al [ 10 ] use a poster to determine the relative poses of multiple cameras in two steps. It requires that different parts of the poster are observed by at least two cameras at the same time, so that SIFT features can be utilized.…”