Theoretical And Experimental Study Of Non-absorption Grating X-ray Differential Phase Contrast Imaging

X-ray phase contrast imaging is an interesting technology in the field of X-rayimaging in recent years. It can detect the substance composed of light elements thatcan’t be detected by traditional X-ray absorption imaging. Thus, it has significantscientific value and wide application potential in the field of medicine, biology,materials science, and non-destructive testing. The approach based on gratinginterferometry can carry out at the traditional low-brilliance X-ray source and provideabsorption, differential phase contrast and dark-field signals simultaneously. However,because of using two absorption gratings, it not only makes the fabrication difficultyand high cost but also make the efficiency limited.To overcome this limitation, our research team firstly propose a method by usingmulti-line X-ray source and structured scintillator to replace two absorption grating inthe grating interferometry, which is called non-absorption grating approach for X-raydifferential phase contrast imaging. The thesis is based on such method to launchrelated research and mainly achieve the following progress:Firstly, we realize the non-absorption grating approach for X-ray differential phasecontrast imaging and acquire the large size of55mm×55mm phase contrast imagesexperimentally for the first time. The setup overcomes the limited of field of view bythe multi-line X-ray source and the limited of high photon-energy X-rays by theabsorption grating. It is more benefit for the future practical application in the field ofmedicine and industry, etc.Secondly, based on the Fresnel diffraction theory, we give a detailed analysis of thequantitative relation between the axis extension length and the imaging field of view.Furthermore, the field of view of phase contrast imaging can be widened by using animproved multi-line X-ray source. Compared with the multi-line X-ray source, it canexpand the imaging field of view of more than4times at the same radiation intensity.Thirdly, we have developed two-step phase-shifting algorithm to retrieve the objectphase information. According to the theoretical analysis and experimental verificationfor the feasibility of this algorithm, the advantage of the algorithm is simple and easyto implement, and it has a strong inhibition to the instability of X-ray source, and thusit can retrieve the phase information more accurately.