Retro-reflective target with high accuracy for industrial photogrammetry

Abstract

Retro-reflective targets (RRTs) are important for obtaining the coordinates of the surface points of objects measured using industrial photogrammetry systems. Targeting the low measurement accuracy caused by the poor roundness of the conventional RRT, a novel RRT was designed in this study by covering a die-cut slice with round holes and high roundness on a glass bead reflective film. The roundness of this novel RRT was on average 0.03 mm higher than that of the conventional RRT. The accuracy of the novel RRT was evaluated in terms of both internal and external coincidence accuracies. The measurement repeatability accuracy of the novel RRT was improved by 25.0% compared with that of the conventional RRT. The thinner the die-cut slice thickness, the higher the repeatability in a certain range. Similarly, the plane fitting, flatness measurement, and standard length measurement accuracies were improved by 30.7%, 34.1%, and 28.1%, respectively.