The advantage of spatial phase-shifting shearography is its ability to extract the phase from a single speckle pattern;however,it often faces spectrum overlapping,which seriously affects phase quality.In this paper,we...The advantage of spatial phase-shifting shearography is its ability to extract the phase from a single speckle pattern;however,it often faces spectrum overlapping,which seriously affects phase quality.In this paper,we propose a shearography phase-extraction method based on windowed Fourier ridges,which can effectively extract phase information even in the presence of severe spectrum overlapping.A simple and efficient method was applied to determine the parameters of the windowed Fourier ridges,and a linear variation window was used to match the phase-extraction requirements for different frequency coordinates.A numerical simulation was quantitatively conducted to compare the phase-extraction results of the proposed method with those of the conventional method for various cases,and a shearography system was built with two types of objects to demonstrate the feasibility of the proposed method.展开更多
Fourier ptychographic microscopy(FPM)is a newly developed imaging technique which stands out by virtue of its high-resolution and wide FOV.It improves a microscope's imaging perfor-mance beyond the diffraction lim...Fourier ptychographic microscopy(FPM)is a newly developed imaging technique which stands out by virtue of its high-resolution and wide FOV.It improves a microscope's imaging perfor-mance beyond the diffraction limit of the employed optical components by illuminating the sample with oblique waves of different incident angles,similar to the concept of synthetic aperture.We propose to use an objective lens with high-NA to generate oblique illuminating waves in FPM.We demonstrate utilizing an objective lens with higher NA to iluminate the sample leads to better resolution by simulations,in which a resolution of 0.28 pum is achieved by using a high-NA illuminating objective lens(NA=1.49)and a low-NA collecting objective lens(NA=0.2)in coherent imaging(λ=488 nm).We then deeply study FPM's exact relevance of convergence speed to spatial spectrum overlap in frequency domain.The simulation results show that an overlap of about 60%is the optimal choice to acquire a high-quality recovery(520*520 pixels)with about 2 min's computing time.In addition,we testify the robustness of the algorithm of FPM to additive noises and its suitability for phase objects,which further proves FPM's potential application in biomedical imaging.展开更多
基金supported by the National Key Research and Development Program of China(No.2016YFF0101803)Hefei Municipal Natural Science Foundation(No.2021017).
文摘The advantage of spatial phase-shifting shearography is its ability to extract the phase from a single speckle pattern;however,it often faces spectrum overlapping,which seriously affects phase quality.In this paper,we propose a shearography phase-extraction method based on windowed Fourier ridges,which can effectively extract phase information even in the presence of severe spectrum overlapping.A simple and efficient method was applied to determine the parameters of the windowed Fourier ridges,and a linear variation window was used to match the phase-extraction requirements for different frequency coordinates.A numerical simulation was quantitatively conducted to compare the phase-extraction results of the proposed method with those of the conventional method for various cases,and a shearography system was built with two types of objects to demonstrate the feasibility of the proposed method.
基金the National Basic Research Program of China(973 Program)(No.2015CB352003)the National Natural Science Foundation of China(No.61335003,61377013,61378051 and 61427818)+1 种基金NSFC of Zhejiang province LR16F050001,Innovation Joint Research Center for iCPS(2015XZZX005-01)Open Foundation of the State Key Laboratory of Modern Optical Instrumentation.
文摘Fourier ptychographic microscopy(FPM)is a newly developed imaging technique which stands out by virtue of its high-resolution and wide FOV.It improves a microscope's imaging perfor-mance beyond the diffraction limit of the employed optical components by illuminating the sample with oblique waves of different incident angles,similar to the concept of synthetic aperture.We propose to use an objective lens with high-NA to generate oblique illuminating waves in FPM.We demonstrate utilizing an objective lens with higher NA to iluminate the sample leads to better resolution by simulations,in which a resolution of 0.28 pum is achieved by using a high-NA illuminating objective lens(NA=1.49)and a low-NA collecting objective lens(NA=0.2)in coherent imaging(λ=488 nm).We then deeply study FPM's exact relevance of convergence speed to spatial spectrum overlap in frequency domain.The simulation results show that an overlap of about 60%is the optimal choice to acquire a high-quality recovery(520*520 pixels)with about 2 min's computing time.In addition,we testify the robustness of the algorithm of FPM to additive noises and its suitability for phase objects,which further proves FPM's potential application in biomedical imaging.
