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Study of Key Technologies in Phase Unwrapping Based on Three Dimensional Optical Measurement

Author: FuShiQiang
Tutor: LiaoWenHe
School: Nanjing University of Aeronautics and Astronautics
Course: Aviation Aerospace Manufacturing Engineering
Keywords: 3D measurements structured light phase shifting phase unwrapping image processing
CLC: TG806
Type: Master's thesis
Year: 2010
Downloads: 152
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Abstract


Optical 3D profile measurements (O3DPM) plays a great role in production and living, and the Phase Unwrapping (PU) is one of the key technologies in phase shifting structured light O3DPM. Based on the study of relevant theories and key technologies of O3DPM in this dissertation, kind of methods for PU were researched, some classic algorithms were implemented, a new quality map used for PU was proposed, and PU module of the O3DPM was completed. The main contents and achievements are as follows:(1) Goldstein’s branch cut algorithm was studied, and a method that added branch cuts manually was used in application, which improved the flexibility of the operation.(2) A new quality map was proposed, which can be used in quality-map-guided PU algorithm. In the beginning, some disadvantages of traditional quality maps are analyzed. Then based on isotropic gradient amplitude, some methods about image sharpening and modulation are combined to construct a new quality map. The new map is named“Modulation-Roberts Gradient Amplitude Variance”quality map (MRGAV). In the applications, the computer simulated and the experimental data are offered. The comparison between the MRGAV quality map and the traditional quality maps shows that the MRGAV quality map not only is more reliable, but also can overcome some drawbacks of traditional quality maps successfully.(3) Path-dependent and path-independent algorithms of spatial PU were learned and compared. Fast Fourier Transform (FFT) that without weight and the Preconditioned Conjugate Gradient (PCG) that with weight were brought about. Then the binary image from MRGAV quality map is used as weight for PCG algorithm. Computer simulated and the experimental data of FFT and PCG are given at last.(4) Based on the study of spatial and temporal PU, classic methods of temporal PU were brought about, including linear, exponent, and reversed exponential fringe sequence.(5) Assessment methods of PU results were summarized; Influence factors about camera calibration were discussed; PU module of the O3DPM was completed based on the research.

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CLC: > Industrial Technology > Metallurgy and Metal Craft > Tolerance techniques to measure and mechanical measuring instruments > General issues > Technical methods of measurement
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