DEVELOPMENT OF PHASE RETRIEVAL TECHNIQUES IN OPTICAL MEASUREMENT

Abstract

This thesis is focused on development of phase retrieval techniques in optical measurement using continuous wavelet transform and windowed Fourier transform techniques. The theories of wavelet transform and windowed Fourier transform techniques are presented. Two-dimensional Gabor continuous wavelet transform is proposed for speckle fringe demodulation to avoid the limitation of spectrum width of a fringe pattern. It is shown that the two-dimensional Gabor continuous wavelet transform is able to successfully retrieve phase from fringe patterns in electronic speckle pattern interferometry for deformation measurement. In addition, fast windowed Fourier transform is proposed for phase retrieval with reduction of computation time compared with the convolution algorithm. Fast windowed Fourier transform can be employed to retrieve phase from fringe patterns in digital speckle shearing interferometry efficiently. Furthermore, fast windowed Fourier transform is effective for denoising of phase fringe patterns in digital speckle shearing interferometry. The experimental results show that the proposed techniques have a potential application in optical static and dynamic measurement.