Research On Underwater Optical Vision System Based On Four-view Vision

With the rapid improvement of China's comprehensive national strength,the research and application of nuclear energy are also increasing at the same time.However,a large amount of waste nuclear liquid can be produced in the reservoir of nuclear factories.Some regular shaped parts will be scattered at the bottom of the reservoir.The work of fishing the scattered parts will be completed by the underwater robot with the manipulator.As the carrier of underwater ecosystem,the visual processing technology of underwater robot directly affects the efficiency and safety of underwater tasks.Therefore,the research of underwater light vision system is of great significance.In terms of the above problems,this paper studies the underwater optical vision system and achieves two new functions: 1.To use the 3D reconstruction technology of underwater parts to measure the distance and part size;2.High precision and real-time target detection of underwater parts.The main contents of this paper are as follows:(1)The workload of traditional underwater camera calibration is immensely heavy,and the results of underwater image preprocessing are not as ideal as possible.Focusing on the problem,combining underwater refraction compensation model with image multi-scale fusion algorithm and proposed a new way of underwater image pre-processing algorithm.The underwater image is compensated by the parameters calibrated by the camera in the air and the refraction rate.And enhanced by multi-scale weight fusion,which improves the underwater image distortion of edge blurred and low image contrast.The algorithm has high reliability and practicability.(2)The development of traditional stereo matching algorithm in stereo vision technology has entered into a period of bottleneck,there has been little innovation in recent years.Focusing on the problem,aiming at the disparity refinement step of traditional stereo matching algorithm.Firstly,deeply study the principle and implementation method of SGBM algorithm.Secondly,a disparity thinning algorithm based on entropy rate super-pixel segmentation consistency test is carried out.The algorithm is validated in Middlebury standard dataset.Compared with the traditional algorithm,the disparity accuracy is improved by 5.88%.Using the stereo matching algorithm mentioned above,the underwater image is tested and obtain the disparity map.(3)The commonly used underwater binocular stereo vision has certain limitations as well,which could hardly see the side information of the target object.In practical applications,it is often necessary to move the position of the robot for secondary photography.Focusing on the problem,a new underwater optical vision system of double-binocular is proposed.By adding an extra group of cameras on the basis of binocular vision can obtain more information of target parts to facilitate the accuracy of measurement of target size.The experimental results show that the average ranging of errors of the target part is 1.7%,and the average size error of the eight kinds of parts is 1.5 mm.Compared with the domestic and foreign dataset in the same period,we have achieved some certain expected results.(4)The underwater optical vision system requires both high precision and high real-time functionality for underwater target identification and detection.Focusing on the problem,this paper proposes to apply YOLOv3 algorithm,which has advantages in the realm of real-time,to underwater target recognition and detection.The experimental results show that the sample identification rate of single underwater part is more than 93.3%,and the recognition and detection accuracy of multiple targets is 91.7%,which meets the expected requirements of underwater optical vision system for target recognition function.