Research On Panoramic Imaging Of 360° Around View Monitoring System

At present,in the field of automotive electronics,the around view monitoring system is widely used in vehicles to assist drivers to drive safely.The around view monitoring system will generate a 360 degree around view image which taken by the multi-fisheye camera installed in the vehicle to eliminate the blind area.Most of the products on the market now have display problems such as stitching gap and misalignment.Furthermore most of the products are 2D around view products.The research of 3D around view products is not mature enough.The main reason is that,the research of image stitching is mostly based on the method of feature point matching for ordinary cameras at present.In the application of the vehicle around view monitoring system,the stitching method based on the feature points can't solve the problem of fisheye image stitching very well.In view of the above problems,this paper designs a new image stitching scheme,which is based on the calibration of the ground coordinate system.The splicing scheme can be roughly divided into two parts,one is the calibration and distortion correction of fisheye camera,the other is the stitching of four fisheye images based on calibration and correction.For fisheye camera calibration and distortion correction part,this paper studies the imaging principle of fisheye camera firstly,then select the appropriate mathematical model of the stitching scheme for fisheye camera which using a projection function to simulate the projection relation by the camera coordinates to image coordinates.The parameter of fisheye camera is included in the coefficient of the projection function,so it doesn't need to calculate the focal length of the camera and distortion parameters.In the calculation of camera parameters,a calibration checkerboard is used to extract the reference coordinates.The equation is extracted from the mathematical model of fisheye camera,and the SVD algorithm is used to solve the equation.The calculation process is fast and accurate.Then,a plane which is consis tent with the camera coordinate system is constructed,and the pixel information of the original image is re-projected to the constructed plane according to the projection function of the fisheye camera.Thus the distortion correction of fisheye camera ima ge is realized.For the stitching part,the 2D and 3D image stitching algorithm based on the ground coordinate system calibration is designed.The core of the stitching algorithm based on the ground coordinate system is the coordinate system transformation and the projection coordinates calculation.The four fish eye camera uses the reference points of the ground coordinate system to calculate the stitching extrinsic parameters,and then the fisheye images are re-projected to a new around view image respectively according to the projection function of the camera.The method of plane projection is used in two-dimensional around view imaging.Although the two-dimensional around view imaging algorithm based on the ground coordinate system solves the problem of stitching gap and dislocation,it has the characteristics of small field of view and image distortion of non-planar objects.On this basis,3D around view imaging algorithm based on surface projection is proposed.3D around view show the image around the car body without gap and it has a wide field of view and realistic display effect.It has a very high application value in improving safe driving.