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.