Design and Application of Dot-Matrix Structured Light for Close Range Industrial Photogrammetry

In close range industrial photogrammetry, a dot-matrix structured light technique is proposed to improve measurement efficiency and increase the density of three-dimensional point clouds. The dense bright spots in structured light pattern are used to replace manually pasted targets. Through image processing algorithms such as threshold segmentation, edge detection, and ellipse fitting, accurate extraction of the pixel coordinates of the bright spot centers has been achieved. This article also proposes a string bead matching algorithm that arranges the bright spot centers in all structured light images in the same order. The measurement experiments on large-sized plane have shown that using structured light technology can obtain accurate and dense three-dimensional point cloud of the plane, and also accurately measure its flatness error. The average distance from the point cloud to the fitting plane is 0.292mm, the distance variation interval is [−1.169mm, + 1.081mm], and the flatness error calculated based on the fitting plane is 2.253mm.