High Resolution 3D Information Acquisition Methods Based On Vision Integrated Rotationally Symmetric Triangulation Sensor

Information acquisition is an important branch of the information scienc. It's a result from the progress and intersection of traditional sensing technology and other information technologies, and is charactered by the high accuracy, high speed, integration and smartness in the process of information acquisition. 3-dimentional information acquisition is an active field in information acquisition, which studies methods of acquiring the geometrical structure and size of 3D objects. Normally it means getting the range data in addition to traditional 2D projective scale. With the development of then siecne and technology, the 3D imformation acqurisition is more and more important in research and industrial field.In this thesis, based on a rotationally symmetric triangulation sensor with integrated vision system, some subjects in 3D information acquisition are investigated, including the sensor fusion, the validity, the uncertainty limit and the speed. Main works in this thesis include:(1) The integration of rotationally symmetric triangulation (RST) sensor and the vision system is studied. The mockup of the sensor system is built and the fusion in sensors' physical layer is realized.(2) The system error factors are investigated. The geometric optical model and the error model of RST sensor are studied. More attention is paid to errors caused by asymmetry which is resulted from eccentric laser illumination and tilted image sensor. It is pointed out that if some part of the ring image was lost, the uncertainty in measurement result will ascend in case of some what asymmetry. A compensation method based on neural network is presented. Then the basic performance parameters of the mockup are given.(3) A detailed analysis of uncertainty limit in RST is presented. Speckle is also the fundamental uncertainty factor in this kind of sensors. The analytic expression of centroid uncertainty limit is derived from the statistic of laser speckle, and it is shown that the uncertainty limit in RST, and also in anamorphic triangulation, is dependent on the solid angle subtended by entrance pupil as seen from the illuminated laser spot, the triangulation angle, as well as the laser wavelength. The influence of aberration of optical system and surface roughness are also discussed.(4) A method of getting the 3D edge characters based on the integrated vision system is studied. When using RST to acquire 3D information, a 2- dimensional scan is always needed. A novel symmetric multi-baseline matching based on the scanning movement is used to reduce matching error, and a subpixel matching based on quadratic interpolating is used to get a more smooth 3D edge. The matching is only done on character edges in images, so it is much more fast and robust.(5) A method of fast measurement path planning of RST guided by the 3D edge characters is studied. Because the RST sensor always measures in the direction vertical to the scanning plane, the 3D edge characters acquired by vision system can be projected to the scan plane and make a path planning of the RST sensor. Two planning methods are presented, one is driven by the 2-dimesional edges, and the other is driven by 3-dimentional surface patches rounded by edges. Through path planning, measurement points are much less than before, and natural quadratic surface patches can be analytically expressed.