Three Dimensional Profile Reconstruction Based On Fringe Projection

Three dimensional profile reconstructions (3DPR) is widely applied in different fields,such as reverse engineering, computer vision, on-line product inspection, model design andmedical treatment. With the rapid development of computer and related devices, researcherspay more attention to the 3DPR based on optical methods, which bear with active andnon-contacting properties. At present, the reconstruction systems can be divided into fourcategories, active optical triangulation, laser interferometry, time in flight and fringeprojection. The fringe projection is becoming popular for its high precision, rapid response,low limitations from the environment.In this paper, 3DPR using fringe projection method is carried out. The majorcontributions are as follows:Firstly, the basic principle of the 3DPR based on fringe projection is described. Themethod employs a typical crossed-optical-axes system projects structured gratings which aregenerated by computer onto the surface of object, and obtains the distortion fringe patternswhich contain the object phase information of the on digital camera. Three methods, includingphase shift methods (PSM) which are used to demodulate the phase information from thedistortion fringe pattern, are discussed.Secondly, several improved fringe projection technologies are reviewed. Thedemodulated phase is wrapped in [-Ï€,Ï€] which needs to be unwrapped to retrieve the realphase information by employing suitable phase unwrapping algorithm. However, it is difficultto obtain the phase at a great accuracy because of the deviant jump of phase caused by systemnoises. To solve the problem, we improved fringe projection technologies throughcombination of a gray code method with a phase shift method. The effectiveness of the phaseunwrapping algorithm is verified by the computer simulation.Thirdly, 3DPR system is established. The period of the fringe projected on the referencechanges gradually. The tiny changes are usually ignored, but it will cause errors. Based on theanalysis of the changes, an accurate mathematical model is presented as well as a calibrationmethod. 3D profile is reconstructed from the unwrapped phase.Finally, the 3DPR experiments are designed based on the theoretical analysis andcomputer simulation. The captured images are pre-proceeded including filtering and binarytransformation with methods which are analysed and compared. The 3D reconstruction of theobject is implemented by the system designed at last. The basic study about 3D reconstruction using the fringe projection is discussed. Thetheoretical analysis, system setup, computer simulation and corresponding experimentalresults provide a promising research field in the future.