Methodological And Theoretical Research On Differential Phase-contrast X-ray Microscopy

High-resolution X-ray phase contrast microscopy traces its history back to thelate1980s in the international context. Nowadays, this imaging technique which iscapable of achieving nanoscale spatial resolution has realized a wide variety ofapplications in the fields of biology, medicine, materials science and environmentalscience, etc. Generally speaking, however, it is somewhat monotonous for X-raynanoscale-resolution microscopy in terms of imaging mechanisms. Besides, it seemsunlikely to acquire the specimens’ quantitative phase distribution experimentally atthe present time.The thesis demonstrates a bold new kind of nanoscale-resolution X-raydifferential phase-contrast imaging system, which is based on an X-ray Fresnel zoneplate and a complex-transmittance X-ray differential plate, and have the potential formanaging simultaneously the regular differential phase-contrast imaging and thequantitative phase imaging or phase distribution. The contents of this thesis consistof several aspects listed as follows:First, a fresh X-ray imaging model is proposed, which is aimed athigh-resolution differential phase contrast; corresponding design for the key X-rayoptics is done, and a few manageable parameters are also examined in detail forpursuing a high image quality.Second, by theoretical formulations and numerical simulations, it is confirmedthat this model system could truly perform the expected nanoscale-resolution,image-quality-tunable, and characteristic differential phase-contrast imaging;quantitative analysis about the effects of the specimens’ absorption on thedifferential phase contrast is completed, which, as a result, shows the promise thatthis imaging technique can be used in most of the X-ray energy range.Thirdly, based on the imaging system, it is accomplished to develop and verifythe phase imaging or phase retrieval technique in addition to the ordinary and characteristic differential phase-contrast imaging; at the same time, the role of themanageable system parameters in regulating the error in the retrieved phasedistribution is also examined.Fourthly, at the end, this thesis gives an assessment of the impact of flaws in theX-ray differential plate on imaging, and suggests a couple of measures to alleviatethis situation.