Prior Knowledge Based Absolute Phase Acquisition Method In Dynamic 3D Measurement Using Fringe Projection

In recent years,dynamic 3-D shape measurement technology has been widely apply to industrial inspection,medical imaging,film&TV Industry.Dynamic 3-D surface imaging technology based on fringe projection gradually becomes hot topic in academic research.Among them,phase measurement profilometry because of its superior performance in accuracy,speed,robustness,etc.has been deeply studied.However,there exists an unavoidable problem in phase shifting methods,which is phase wrapped.The Conventional spatial phase unwrapping method needs the least number of images but is not reliable enough.The temporal phase unwrapping method has high reliability,but it requires more images and takes a long time to measure.There are some unconventional absolute phase retrieval methods such as absolute phase extraction technology by geometric constraints based multi-view system which designed by means of addition of multiple cameras or projectors.Nevertheless,adding perspectives not only reduces the measurement area,but also increases the complexity and expenses of the whole system.In dynamic 3D profiling,the initial or similar 3D shape of the measuring object is often known,which provides clues to determine fringe order in the actual measurement.In this paper,based on the phase-shifting method,a dynamic three-dimensional profiling method assisted by approximate or similar models is proposed.Without increasing the complexity of the system,the reliability of the method is close to temporal phase unwrapping method,while the measurement time that takes is close to spatial phase unwrapping method.The main contents of this paper are as follows:(1)introduced the fringe projection three-dimensional shape measurement technology and its research status;(2)introduced phase shifting profilometry and the principle of multi frequency heterodyne phase unwrapping method;(3)studied the method of obtaining absolute phase.According to whether the original model of measurement object can be obtained,the absolute phase acquisition method aided by approximate model or similar model is proposed;(4)built a measurement system,verified experiments and studied the range of application of the method.;The main innovations of this dissertation are as follows:(1)proposed an absolute phase acquisition method that uses an approximate model combined with target tracking and feature matching;(2)proposed a point laser assisted absolute phase acquisition method based on similar model(general model),which is even suitable for measuring objects with isolated parts.