Research On Underwater 3-D Imaging And Detection By Laser Plane Scanning

It's significant for submarine and ROV to observe submerged objects and landform. blue-green laser which is absorbed little by water is in favor of gaining the high resolution images of close-by objects. So the underwater laser imaging detection is an important assistant of sonar detection.Laser range gating and Laser synchronous scanning are two important methods in use. But there are some disadvantages for these methods. These techniques can't fulfill the requirements of ROV excellently. This paper presents the laser plane scan based on optical triangulation, which is advanced not only in simple configuration, convenient operation, but in high precision and high resolution when the detection is operated in the vicinity of the targets. Especially it has high performance in real-time. Using plane laser to scan objects when ROV moves forwards, CCD camera captures the stripe falling on the object. The dynamic measurement model was constituted and the effect of refraction on the measurement was corrected. The 3-D coordinates of objects could be obtained after digital image processing and integrating the information of location and attitude. These 3-D points are fitted together to form the depth image, which is different with gray image and color image, because it can supply 3-D coordinate. It can be applied to detecting mine, ocean exploration and so on.This paper discusses the basic arithmetic of camera calibration, and finished the calibration with a four-step arithmetic. Furthermore, three methods for structure calibration were presented. The key factor of image processing is drawing out the center of laser stripe. This paper compared some stripe inspect algorithms and found that it possessed the advantages of less data throughput and fast implementation if a small window and an alterative direction template are opened on the stripe. It can eliminate white noise and repair the broken laser line by making use of the trend of stripe.