Binocular Underwater Measurement With Multicolor Structured Light

Abstract

This article designs an underwater binocular measurement system combining binocular vision and multicolor structured light, for the problem of autonomous grasping by underwater robots. In our solution, multiple colored stripes of structured light are projected on the surface of the object to be measured at once without the scanning process and, thus, have the advantages of high measurement accuracy, efficiency, stability, and reliability, which could realize the survey and positioning of underwater targets and guide the robotic arm to grasp the underwater targets autonomously. In this article, an underwater binocular measurement model with nonparallel and non-co-refractive surfaces is established by tracing the propagation path of light in water, and a multicolor structured light array is used to provide active visual features for the underwater object to be measured by projecting the multicolor structured light array, avoiding the limitation of the center point of monochromatic structured light, and the object could be at any position in the binocular field of view. Then, the laser strip images were separated from the background and segmented by the HSV double-threshold segmentation method; the color light stripes segmented from the left and right images were matched corresponding to their color information and position information. Finally, the feature points required for measurement are extracted from the laser stripe images taken by the left and right cameras to achieve a fast underwater survey, and through analyzing the experimental data and observing the object 3-D reconstruction effect, the effectiveness and accuracy of the underwater binocular measurement model and the underwater binocular matching algorithm established in this article are proved.