| The emergence and development of X-ray imaging technology has had a profound impact on human society,especially its wide application in non-destructive testing and medical treatment has brought great convenience to people.When faced with the problem that traditional imaging techniques cannot detect weakly absorbing substances,X-ray phasecontrast imaging came into being.Among all its methods,the phase-contrast imaging based on the Talbot-Lau interferometer realizes imaging on conventional X-ray sources,which is a key step towards clinical application.About the grating phase-contrast imaging technology based on conventional X-ray sources,The reasons for its delay in moving to practical applications include the harsh requirements of the grating manufacturing process,the complexity of the three-grating imaging system and the high radiation dose received by the sample due to long data collection time.Therefore,researchers from all over the world actively carry out research and seek solutions.The method proposed by the American scholar Han Wen et al uses a single grating to restore image information through Fourier transform,which has aroused the eager attention of researchers from various countries.This method utilizes a common absorption grating,which reduces the requirements for the grating manufacturing process and the complexity of the system.At the same time,using the information recovery algorithm of Fourier transform,only a single sample image needs to be collected,which reduces the radiation dose received by the sample and is more suitable for clinical application.In this paper,based on the X-ray single grating phase-contrast imaging,the research on the acquisition technology of multi-contrast image using single grating is carried out in the laboratory environment,which involves system construction,information recovery,and artifact correction.The specific contents are as follows:1.According to the theory of single grating phase-contrast imaging,we sorted out the restoration process of multi-contrast image using single grating.An X-ray single grating imaging system was constructed and used to experimented under laboratory conditions,and the information extraction algorithm of Fourier transform was used to restore the three contrast images of the sample’s absorption,phase and scattering.2.Aiming at the phenomenon of spectrum aliasing in the process of multi-contrast image restoration using single grating,we analyzed the mechanism of spectral aliasing artifacts from the perspective of information recovery algorithm.According to the enlightenment of dealing with the aliasing effect in visible light,a new image acquisition method and artifact correction algorithm were proposed,and the proposed scheme was verified through specific experiments.3.Regarding the Moiré fringes that appear in the restoration of multi-contrast images,we analyzed and explained the mechanism of the Moiré artifacts,and derived the parameter formula of the Moiré artifacts through the principle of geometric shading.Combining the theoretical analysis of the change of Moiré fringe and the structural characteristics of the imaging system,two schemes of rotating grating and adjusting the projection frequency of the grating were proposed to eliminate Moiré artifacts,and specific experiments were used to prove its feasibility.Compared with the conventional technology of frequency domain filtering,the selected schemes could effectively improve the image quality and increase the signal-to-noise ratio without losing image information as much as possible. |
