Calibration Of The Relative Orientation Between Multiple Depth Cameras Based On A Three-dimensional Target

Depth cameras play a vital role in three-dimensional(3D)shape reconstruction,facial expression tracking,virtual reality and other visual information-related fields.However,a single depth camera cannot obtain complete information about an object by itself due to the limitation of the camera's field of view.Multiple depth cameras can solve this problem by obtaining depth information from different perspectives simultaneously and fusing data from different perspectives.Accurate calibration is the precondition for accurate measurement of multi depth camera system.However,because it is difficult to unify the coordinates of different depth cameras into one coordinate system,and the multiple camera systems with a specific angle have a very small overlapping field of view,traditional chessboard-based planar targets are not well suited for calibrating the relative orientations between multiple depth cameras.In order to solve this problem,a new calibration method for internal and external parameters of multi depth camera is proposed.The main research contents include the following aspects:Firstly,a simple stereo target is used as a calibration object to unify multiple depth camera coordinates into the same world coordinate system,and the spatial position relationship between them is calculated.This method effectively solves the problem of relative space position calibration of multi depth camera in the condition of limited field of view or non-overlapping field of view.At the same time,it solves the problem that it is difficult to measure the relative position of the 3D target.Using this 3D target,multiple depth cameras can be calibrated simultaneously.Secondly,a method for the accurate measurement of the relative position between the target surfaces of a 3D target by using lidar is proposed.We use lidar to scan the 3D target and collect the data of the 3D point cloud on its surface and use the 3D point cloud data to accurately measure the relative positions between target surfaces.This method is not only applicable to the 3D target designed for the purposes of this paper,it can also be applied to all 3D calibration objects consisting of planar chessboards.This method can significantly reduce the calibration error compared with traditional camera calibration methods.At the same time,the internal and external parameters of the multi depth camera system are calibrated by using the 3D target precisely measured,which further improves the calibration accuracy.By unifying all the planes of the 3D target into a coordinate system,the feature points on the calibration plane are also in a unified coordinate system.Then,in order to reduce the influence of the infrared transmitter of depth the camera and improve its calibration accuracy,the calibration process of the depth camera is optimized.In addition,in view of the problem that the depth value collected by the depth camera has a large error,a simple and easy to operate algorithm is designed to compensate the depth camera from the practical application so as to reduce the depth error.Finally,a series of calibration experiments are carried out for the above research contents.Experimental results demonstrated the reliability and effectiveness of the proposed method.