Structured Light Sensor And Underwater 3D Inspecting System

This dissertation is mainly about some research works for the following projects, "Large-scale Digital Three-dimensional Measurement for Modern Shipbuilding", a cooperative project with Bohai Shipbuilding Heavy Industry Co., Ltd, and "Foundational Technology Research about Unmanned Mini-detector for Underwater Application", a project from Commission of Science Technology and Industry for National Defense in the tenth five-year plan. This paper investigates some basic issues about 3-D vision measurement, which can be summarized as follows:Discuss the principle of vision sensor with structured light, the structure and model of structured light vision system. Go deep into analysis about the influence to accuracy from the structure. Present the method how to draw out the center of laser stripe.Discuss the calibration method of vision system and present a new one of the vision system with laser stripe.The actual accuracy is due to the calibration accuracy. Calibration methods affect the convenience and dependability of an optical measurement system directly. Measurement system is required to be more and more real-time, on-line, intelligent and pliant. There are many calibration methods which are discussed in chapter 2 and 3, but most of them can only be used in laboratory. An important reason is that these calibration methods are so complicated that they can not meet the need of speediness and usualness.With the help of the direct calibration presented in this paper, we need not calibrate the intrinsic and extrinsic parameters and structural parameters. We can know the relationship between the points in images and coordinates in the space through the images of a plane target. We can get coordinates of an arbitrary pointfrom the interpolation of known points' coordinates. It is credible and insensitive to interim parameters.A new method is put forward, which is to use optical detector based structured light in underwater 3D measurement.The key is 3D reconstruction in underwater target recognition. The purpose of underwater target recognition is not to obtain 2-D gray-level images, and reconstruction is not effectual from the underwater gray-level images. This paper presents the laser plane scan, which is not only accurate, high resolving but also real-time. Using plane laser to scan objects when ROV moves forwards, CCD camera captures the light stripe falling on the object. The dynamic measurement model is constituted and the effect of refraction on the measurement is corrected. The 3-D coordinates of objects can be obtained after digital image processing and integrating the information of location and attitude. We can get clear images and angular field is ample.We also analyze the effect of refraction in underwater application of vision measurement system, and show the modified expressions.Analyze how to calibrate an underwater camera in the air. The modified method and conditions of conversions are put forward, which are about that the underwater images from the camera with sealed window convert to the ones in the air. Present the camera location rules, which offer the theoretical basis for the underwater application of a high-sensitive camera.Prove that the methods and the principle are correct and effectual by experiments.