Multi-sensor Joint Calibration And Application

Underwater sensor calibration technology is of great significance for high-precision 3D pose estimation,scene reconstruction,and underwater robot navigation.However,due to the special underwater environment,the sensor needs to be deployed in a sealed cabin,and the direction of the incident light changes with the refractive index of the medium.If the calibration method in the air is used directly,it will bring geometric errors to the calibration system,which in turn affects the accuracy of the calibration.To solve the refraction problem brought by multi-media and improve the accuracy of sensor calibration,the following work is done in this paper:(1)Given the complicated underwater environment that leads to the cumbersome process of joint camera-IMU calibration,this paper proposes a joint camera-IMU calibration model based on the refractive index of the medium and planar refraction.Firstly,the mathematical expressions of camera focal length before and after refraction are derived,and the method of calculating camera intrinsic parameters in multi-media by the refractive index of the medium is realized.Then the joint camera-IMU calibration is carried out,and the joint camera-IMU calibration can be completed in the air by converting the underwater model to air through mathematical transformation.(2)For the problem that the refraction between multi-media changes the imaging mode of the camera,this paper introduces refraction into the imaging principle of the camera and proposes a multi-media-based refraction camera model.Based on the intrinsic parameters of the camera,the effect brought by refraction is transferred to the change of the extrinsic parameters of the camera.In addition,the model involves the plane refraction constraint and coplanarity constraint of light,which can effectively obtain the normal vector of the refraction plane.Compared with the air-based camera calibration method,the multi-media refraction camera model can improve the accuracy of camera calibration and obtain the extrinsic parameters after refraction.(3)Regarding the problem that the refraction between multi-media changes the laser light path,this paper proposes a multi-media-based camera-line laser joint calibration method.Firstly,the calibration of the laser plane equation is realized for the imaging principle of the camera in the air.Then the refraction between multi-media is incorporated,and the refraction-based laser plane calibration method is proposed based on the work of(2).Finally,3D reconstruction of spatial objects is performed to improve the accuracy of object reconstruction.