X-ray Coded Aperture Imaging Theory And Experimental Research

Due to the fact that X ray is absorbed strongly when it travels in media, common methods are not suitable for X ray imaging, which makes the imaging technology by coded aperture become one of the main methods for X ray imaging.During X ray imaging by coded aperture, the image, which is produced on the receiving surface when the ray passing the small apertures arranged in some special way, is often regarded as the result of projection. In fact, while X ray passes the small apertures, diffraction happens. Due to its short wavelength, the influence of the diffraction is neglected. The images produced by different points of an object stagger and overlap one another, so a distributed two-dimensional signals results which can not be distinguished clearly with naked eyes on the receiving surface. In order to obtain the real space distribution of the objects, a series of decoding for the degenerated picture from the receiving surface should be done, i.e. it needs following treatments for the pictures' resuming and rebuilding.During the research on ICF, Inertial confinement Fusion, the space distribution of X ray carries a lot of physics information and we can obtain many space distribution data produced by various plasmas by way of measuring its space distribution. These data are necessary for the research on inner explosive physics reactions. High space-resolved X ray coded imaging is one of the most important means for research on ICF.We endeavor to do research on imaging technology by coded aperture and its applications in the ICF experimental research. Overall study has been put to the theoretical problems about imaging technology by coded aperture. Some research has been done on the rebuilding technology of the imaging by the coded aperture, and a rebuilding method is presented for the two-dimensional object imaging by the coded aperture. The best shape for apertures is picked out through coding and decoding apertures with different shapes.Considering diffraction effect based on scalar theory, we deduced a formula for point spread function of the coded aperture and discussed the ring coded aperture in detail. Our research group made a ring a ring microscope with the coded aperture. Combining with other imaging equipments, we had experiments in the key lab of laser and plasma in the Engineering and Physics Academy of China, and we rebuilt ICF image with the point spread function taking diffraction effects into consideration and got decoded pictures.On the basis of coded aperture imaging theory, rebuilding coded pictures with the processing technology for the digital picture on the one hand, rebuilding the pictures that overlap from the coded apertures with the technology of optic interference picture on the other hand, we made a plural filter and obtained a rebuilt picture. It is proved that the methods to create coded apertures and rebuilt picture are definitely right. Furthermore it laid a good foundation for the work in this field in the future.