Phase Unwrapping In Dynamic 3-D Profilometry

Three-dimensional surface measurement has been widely used for CAD, numerical machine technique, product quality test, and medicine, even for art. Non-contact optical 3-D profilometry has many advantages: high accuracy, fast and automatic measurement, etc. Compared with other methods, Fourier transform profilometry (FTP) requires only one frame of deformed fringe pattern reflected by a diffuse object surface to gain the phase distribution of object. And it's used in dynamic measurement generally.Phase unwrapping is an unavoidable problem for any profilomety based on fringe analysis. It is a key step to reconstruct surface of the object being measured in profilometry using fringe projection. Phase unwrapping is independent to path in ideal condition. But practical situation is complex; many phase-unwrapping methods have been put forward. In dynamic 3-D profilometry, phase unwrapping is not only operated on x and y coordinates but also on t (time) coordinate. Cause the introduction of t coordinate, are more paths available. This article emphasizes on phase unwrapping in dynamic 3-D profilometry.1, present three kinds of phase unwrapping methods for dynamic 3-D profilometry: direct wrapping, phase difference unwrapping and phase unwrapping based on modulation sorting. We focus on discussing the method for unwrapping phase map with isolate areas. Theoretical analysis and computer simulation and compare of these methods are both presented.2, Introduce FTP based on bi-color fringe projection into dynamic 3-D profilometry. This method increases the accuracy of system. And we reconstruct thebi-color fringe, use red component to mark the start point of phase unwrapping. Software based on this theory is introduced in detail, structure and algorithm.3, Applying 3-D profilometry in flow field research, we can obtain the phase distribution caused by flow field. Distribution of refractive index of flow field can be calculated from phase distribution. 3-D profilometry can reconstruct the dynamic process of flow field and provide data for father research.