Contoured Correlation Interferometry For Electronic Speckle Pattern Interferometry And Synthetic Aperture Radar Interferometry

Electronic Speckle Pattern Interferometry (ESPI), and Interferometric Synthetic Aperture Radar (InSAR), are two closely related techniques. The former is a whole-field non-destructive technique to measure the optical rough surface, and it is widely used in the measuring of vibration, displacement, strain and medical diagnosis; the latter finds its application in measuring the topography of a surface, its changes over time, and changes of the characteristics of a surface. Both of them take interferogram as their main object of research, and both obtain the last physical values for measurement through interferomgram processing. However, either ESPI or InSAR encounters great difficulties in their applications due to the serious speckle noise and the decorrelation noise existing in the interferograms.This dissertation is based on a thorough exploration into interferograms processing techniques and proposes a method named Contoured Correlation Interferometry (CCI) as a solution to the problem mentioned. Its originality is observed in the following 4 aspects:(1) CCI Method to Generate ESPI InterferogramsIn order to overcome the major shortcoming of the existing fringe patterns generation methods, i.e., the inevitable accompanying serious multiplication noise, this dissertation puts forward a CCI method to generate ESPI fringe patterns. Because this method takes the optimal fringe-contoured window, the fringe patterns generated are of high quality and almost void of any speckle noise.(2) ESPI Phase Retrieval Methods Based on CCI Fringe PatternsIt takes advantage of the two prominences of the CCI fringe patterns: a. Being free of multiplication speckle noise; b. Good normalization, to propose several phase retrieval methods based on CCI fringe patterns, i.e., fringe centerline method, single-fringe-pattern phase field extraction method, and single-phase-step phase field extraction method.(3) Co-registration Based on Three Parts of Two Complex Images for InSARIt only needs three arbitrary parts of the two complex images instead of four parts which are necessary for the existing co-registration methods. Furthermore, the co-registration precision is improved due to the fringe-contoured window used.(4) CCI Method to Generate InSAR Phase ImagesIt also takes only three parts of the two complex images instead of four for the conventional method to generate high-quality phase images. It proves an efficient tool that reduces speckle noise while preserving the phase derived, which solves one of most difficult problems in InSAR data processing.Among the above mentioned points, (3) and (4) together piece up a full picture of InSAR data processing method using only three arbitrary parts of the two complex images, which provides a totally novel approach to conduct InSAR data processing. It has two major advantages:â‘ It requires only three arbitrary parts among the four parts of the InSAR complex image pair. Suppose the SAR image formation is fulfilled on the satellite, it asks only 3/4 of the data to be transmitted to the earth for the consequent InSAR data processing and thus to save transmission time to a large extent.â‘¡Coherence of the co-registered complex image pair gets enhanced because the fringe-contoured window is adopted as computation window and the co-registration precision is increased compared with the previous practice. Consequently, the decorrelation noise of the phase images generated is suppressed effectively and it is made possible that the phase information stays intact. All these are favorable to the phase unwrapping and the highly precise Digital Elevation Model (DEM) retrieval which come next.Apart from the forgoing four aspects, there are other two important jobs done in this dissertation:(1) An intense analysis is made on the methods to obtain the fringe orientation map, and two of them (which are adopted in this research) are given a close introduction. Furthermore, a precision analysis using simulated fringes is carried out to make a comparison of the processing precision of the two methods, which could serve as an important reference for the InSAR and ESPI fringe orientation computation and window size determination.(2) In ESPI, the saw-tooth phase map obtained by the phase-shifting technique is inherently full of speckle noise. The high-level noise of the map must be suppressed before it is unwrapped. In accordance with the feature of the saw-tooth phase maps, an adaptive filter is developed by combining the classical sine/cosine filter and the fringe orientation information of the saw-tooth phase map. Compared with existing filters, it has a better performance on phase jump information preservation and produces no blurring effect on the phase distribution provided the filtering is implemented on the equal-phase window. Moreover, its capability of noise reduction is more powerful.