Accurate Calibration of a Large Field of View Camera with Coplanar Constraint for Large-Scale Specular Three-Dimensional Profile Measurement

Abstract

In the vision-based inspection of specular or shiny surfaces, we often compute the camera pose with respect to a reference plane by analyzing images of calibration grids, reflected in such a surface. To obtain high precision in camera calibration, the calibration target should be large enough to cover the whole field of view (FOV). For a camera with a large FOV, using a small target can only obtain a locally optimal solution. However, using a large target causes many difficulties in making, carrying, and employing the large target. To solve this problem, an improved calibration method based on coplanar constraint is proposed for a camera with a large FOV. Firstly, with an auxiliary plane mirror provided, the positions of the calibration grid and the tilt angles of the plane mirror are changed several times to capture several mirrored calibration images. Secondly, the initial parameters of the camera are calculated based on each group of mirrored calibration images. Finally, adding with the coplanar constraint between each group of calibration grid, the external parameters between the camera and the reference plane are optimized via the Levenberg-Marquardt algorithm (LM). The experimental results show that the proposed camera calibration method has good robustness and accuracy.

Multipath-Closure Calibration of Stereo Camera and 3D LiDAR Combined with Multiple Constraints

“…The chessboard calibration object [13][14][15][16][17][18] is the most widely used in this context. Unnikrishnan et al [19], Pandey et al [20], Mirazei et al [21], Liu et al [22], Khoscovian et al [23], Zhou et al [24], Lu et al [25], Liu et al [26], and Li et al [27] established coplanar constraint relationships through checkerboard calibration objects to accomplish the extrinsic calibration of cameras and 3D LiDAR. Zhou et al [28] added edge detection of the checkerboard on the basis of Unnikrishnan's method, establishing coplanar and collinear constraint relationships.…”