Study On Modeling And Calibration Technology Of Underwater Camera

According to the demand for underwater camera modeling and calibration technology of underwater vision measurement, a model of underwater camera is established and a method of underwater camera calibration is presented.First, normal line structured-light measurement method is thoroughly discussed. Second, underwater camera model is established by analyzing the principle of underwater camera. Third, the main paramters that influence the accuracy of underwater camera is analysed and the calibration method is presented.Finally, an underwater line structured-light self-scan 3D measurement method is designed.The feasibility of underwater camera model and underwater calibration method is verified by experimental measurement results.The main work in the dissertation can be summarized as follows:1.Based on ideal pinhole perspective transformation model, a mathematical model of underwater camera, in which the refraction has been compensated, is built. The transformation relationship between image-plane coordinate system and world coordinate system is established, and parameters that should be calibrated are determined.2.An underwater camera calibration method based on range angle arrangement constrain method is presented. By calculating the changes of propagation direction of light when it travels from water to air, the nonlinear corresponding relationship between points in water and points on CCD image is established. A planar grid target is adopted to generate calibration points.Then the calibration process of camera parameters is done.3.The underwater line structured-light self-scan 3D measurement method is presented. A galvanometer is adopted to reflect laser plane onto object's surface.The laser plane intersects the surface of object and a light stripe which is photographed by a camera is formed. According to the position of each point of light stripe on image, the offset caused by refraction is calculated and compensated by law of refraction and laser triangulation method. Then utilizing the equation of laser plane in water, accurate 3D coordinates of detected points are accurately calculated out.4.A software of calibration and measurement process is developed in Visual C++6.0 development environment on Windows XP platform.Calibration and measurement experiments are implemented utilizing this software.The innovations of this dissertation are establishing an underwater camera model which considered refraction, proposing an underwater camera calibration method, and designing an underwater self-scan meaurement system to verify the feasibility of underwater camera model and calibration method.