Extraction And Analysis For The Phase Of Laser Interference Detection In High Speed Flow Field

In the field of high speed flow field measurements,fringe pattern is usually obtained by interferometry,the phase information can be extracted by interference fringes and then get the information to be tested.So the study on phase extraction of interference fringes has a very important significance.This paper mainly studies the phase extraction of interference fringe pattern in high-speed flow field,the main contents of this paper are follows:(1)This paper introduces several commonly used methods to obtain the phase information of interference fringe pattern,which includes phase-shift method,Fourier transform method and time-frequency analysis method.Among them,the windowed Fourier transform and wavelet transform are introduced in the time-frequency analysis method.The advantages of each method is described and the limitation of phase-shift method,Fourier transform method and windowed Fourier transform method to extract the interference fringe phase is summarized at the same time.Finally,the two-dimensional continuous wavelet transform method presented in this paper is proposed.(2)Two-dimensional continuous wavelet transform has a flexible time-frequency analysis window,which can realize the multi-scale refinement analysis of the signal.In order to solve the time-consuming problem in the traditional two-dimensional continuous wavelet transform,The traditional two-dimensional continuous wavelet transform algorithm is improved,in this paper,the discrete scale factor and the rotation angle in the traditional two-dimensional continuous wavelet transform are proposed to replace by a small amount of discrete scale factor and rotation angle,which greatly reduces the processing time.In the process of calculating the wavelet coefficients,the calculation is still time consuming due to the existence of convolution calculations.So a fast Fourier transform schemes is employed,then the processing time can be further reduced.After calculating the wavelet coefficients,the wavelet ridge is extracted by the ridge detection algorithm and then the phase can be obtained.(3)The traditional two-dimensional continuous wavelet transform and the improved two-dimensional continuous wavelet transform are used to extract phase of simulation and experimental interference fringe pattern.Then two different algorithms are used to extract the phase of several different interference fringes in the high-speed flow field.Prior to the phase extraction,the pretreatment process of the median filtering and homomorphic filtering for interferogram is carried out and binarization processing is also adopted for the image.Then the traditional two-dimensional continuous wavelet transform and the improved two-dimensional continuous wavelet transform are used to extract phase of simulation and experimental interference fringe pattern.By comparing the PSNR and the RMSE of interference fringe pattern of before and after processing under the two algorithms,the accuracy of the two algorithms is not much difference,Which indicates that the improved two-dimensional continuous wavelet transform algorithm can accurately extract the interference fringe pattern phase.According to the concept of cover map proposed in this paper,the number of parameter pairs in traditional two-dimensional continuous wavelet transform algorithm is greatly reduced,and the processing time is accelerated.The results show that the improved two-dimensional continuous wavelet transform algorithm can extract the phase of the interference fringe pattern quickly and accurately,which is feasible for the extraction of the interference fringe pattern phase in the high-speed flow field.