Error model of misalignment error in a radial 3D scanner

A radial 3D, structured light scanner, was developed from a laser projector and a wide field of view machine vision camera to inspect two - four inch diameter pipers, primarily in the nuclear industry. For identifying the nature and the spatial extent of defective regions, the system constructs a surface point cloud. A dominant source of error in the system is caused by manufacturing tolerances which leads to misalignment between the laser projector and the camera. This causes a triangulation error, reducing the accuracy of the result. In this paper, the error model of the misalignment of the laser and image plane. For a given target distance, we derive an almost linear relationship between angular error in degrees and the error in reported radius (distance from the probe to the surface) in mm and found that for the target 0.1 mm accuracy on a 4 inch pipe, the misalignment needs to be controlled to less than 0.05 degrees. Future work will consider a post manufacturing calibration routine to compensate for this misalignment.