Underwater target three-dimensional detection is crucial for effectively recognizing and acquiring target information in complex water rings. The underwater robotic operating system as a conventional underwater operating platform, generally equipped with a binocular or monocular camera, how to utilize the underwater monocular camera with high precision and high efficiency to complete the target three-dimensional information acquisition is the main research starting point of this paper. To this end, this paper proposes a laser-assisted three-dimensional depth monocular detection method for underwater targets, which utilizes three cross lasers to assist the monocular camera system in capturing the depth data at different positions of the target plane at one time. The image correction by the four-point laser calibration method in this paper solves the difficulties of image distortion caused by an unstable underwater environment and lens effect, as well as laser angle deviation caused by the tilting of the underwater robot. The instability of the underwater environment and the lens can cause image distortion, and the tilt of the underwater robot causes the laser angle to deviate. After correcting the image, the depth data between the target and the robot can be calculated based on the geometric relationship that exists between the imaginary rectangle formed by the laser dots and laser lines in the image and the imaginary rectangle formed between the lasers on the device. This method uses a single image to obtain target depth information and is capable of measuring not only horizontal planes but also multiplanes and inclined planes. Experiments show that the algorithm improves the performance accuracy in underwater environments and land environments compared to traditional methods, and obtains depth information for the entire plane at once. The method provides a theoretical and practical basis for underwater monocular 3D information acquisition.
