Fringe Analysis Technology Based On Wavelet Ridge And Research On Its Application

The amplitude, phase and frequency contained in the phase are the main characteristic of optical fringe signal. Their magnitude and variational rule are widely applied in the scientific research and engineering domain for accurate measurement such as displacement, deformation, density, as well as the detection and diagnosis of radar, medical, and biomedical signal. Take the fundament of extracting the instantaneous frequency and phase of optical fringe signal based on wavelet ridge as beginning, Multiscale Windowed Fourier Transform (MWFT) method based on instantaneous frequency gradient is put forward and theoretical analysis, computer simulation and experiment are presented to study its application in three-dimensional measurement, time-frequency analysis of non-stationary signal and other related phase measurement.Firstly, the theoretical analysis and computer simulation explain the availability of extracting the instantaneous frequency and phase of fringe signal. The analysis to the practical interference fringe pattern illustrates that detecting the variation of frequency and phase is able to detect the holes, non-stationary area and so on.Secondly, basing on explaining the theory of MWFT, the time-frequency window's variation rule is analyzed theoretically. The similarities and difference between MWFT and Wavelet Transform are explained. We then study the application in the three-dimensional measurement of MWFT based on instantaneous frequency. Furthermore, in order to improve the frequency resolution and improve the accuracy of extracted fundamental frequency, we bring forward the concept of local stationary length of signal and study the MWFT based on instantaneous frequency gradient in the application of three-dimensional measurement, which have improved the extracted accuracy of phase and gotten definite noise immune ability.Thirdly, we study time-frequency concentration ability of the non-stationary signal by using MWFT based on instantaneous frequency gradient and do a comparison with Winger-Ville transform and WT, giving the simulation and experiment result.Finally, we apply the MWFT based on instantaneous frequency gradient to analyze non-stationary white-light interference spectral signal, and demodulate the phase to realize the related physical measurement such as thin film.