Design Of Phase Extraction Ip Cores And Platform In The Time-frequency Domain For Digital Interferograms

Phase extraction technology is a key content for the analysis of digital interferograms,and has been widely utilized in the fields such as residual stress measurement of the composite material and surface deformation measurement for an object.With the advancement of modern optical testing technology,the measured objects and application occasions are growing,and digital interferograms analysis technology is posing high requirements for analysis speed and accuracy in many specific applications.Most of the existing phase extraction technologies rely on computer operating systems,their real-time and portability are not enough,and are highly targeted,which cannot meet the current situation of high-speed processing in different applications.In order to achieve the purpose of real-time analysis of digital interferograms phases,a method for designing digital interferograms phase extraction IP cores is proposed based on FPGA platform and using the hardware core processing method.A PSM-IP core is designed based on the phase shifting method(PSM)for extracting phase.The PSM-IP core includes a digital interferogram input buffer module,an interferograms phase shifting operation module,an interferograms inverse tangent function operation module and a phase information output module.The coordinate rotation digital computer(CORDIC)algorithm is optimized in the digital interferograms inverse tangent function operation module,and the arctangent operation of the pipeline structure is realized.Thus,real-time phase extraction of the phase shifting digital interferograms can be completed.According to the time-frequency domain analysis technique of single-frame interferogram,the Fourier transform(FT)method,windowed Fourier transform(WFT)method and two-dimensional continuous wavelet transform(2D-CWT)method are studied respectively.A single-frame interferogram time-frequency domain phase extraction integrated module is designed,which involves three parts: 2D-FFTM IP core,2D-WFTM IP core and 2D-CWTM IP core.The 2D-FFTM IP core divides the 2D-FFT into row and column directions and performs 1D-FFT respectively.The windowing of the 2D-WFTM IP core is done on the basis of 2D-FFT,the window function module selects the Gaussian window.The 2D-CWTM IP core selects the Morlet wavelet as the mother wavelet.the scale factors and rotation factors are set,the spectrum of two-dimensional fringe patterns and the spectrum of the two-dimensional wavelet kernel function are multiplied,and then use the wavelet ridge extraction algorithm to achieve.The design of the entire module effectively solves the problem of real-time phase analysis of single-frame interferogram.Digital interferograms were obtained through computer simulation,moiré interference and grating projection test platform.The phase extraction test experiment was carried out on computer simulation interferograms,moiré interferograms and grating projection interferograms.The results show that the phase extraction IP cores is used to analyze the phase of the 256?256 pixels digital interferograms,the phase extraction time is effectively shortened while ensuring accuracy.The reliability and effectiveness of the phase extraction IP cores are verified.It has important application value in optical non-contact real-time measurement.