内容提要：
For centuries, lens-based microscopy, such as light, phase-contrast, fluorescence, confocal and electron microscopy, has played an important role in the evolution of modern science and technology. In 1999, a novel form of microscopy, i.e. coherent diffraction microscopy (also termed coherent diffraction imaging or lensless imaging) was developed and transformed our traditional view of microscopy, in which the diffraction pattern of a noncrystalline object or a nanocrystal is first measured and then directly phased to obtain an image. The well-known phase problem is solved by combining the oversampling method with iterative algorithms. In the first part of the talk, I will briefly describe the principle of coherent diffraction imaging. I will then present our recent experiments on coherent diffraction imaging with an X-ray free electron laser, which allows us to characterize materials at sub-10 nm resolution with a 10 femtosecond time scale.
In the second part of the talk, I will present a general method for determining 3D local structures at atomic resolution. By combining scanning transmission electron microscopy with a novel tomographic technique known as equally sloped tomography, we have imaged metallic nanoparticles at atomic resolution in three dimensions and revealed new atomic structure information that are hidden in conventional 2D projections. We expect this general method to find broad application in materials sciences, nanoscience, physics and chemistry.
 
报告人简历：
Jianwei Miao is an internationally renowned pioneer in the development of novel imaging methods with X-rays and electrons, and has made contributions to theory, computation, and experiment. Miao performed a seminal experiment on extending X-ray crystallography to allow structural determination of non-crystalline specimens in 1999. This method, known as coherent diffraction imaging (CDI) or lensless imaging, has been broadly implemented using synchrotron radiation, high harmonic generation, optical lasers, and electrons. It was also one of the major justifications for the construction of X-ray free electron lasers worldwide. In addition to his seminal contribution to CDI, Miao has also pioneered a general electron tomography method for 3D imaging of local structures at atomic resolution. In 2005, he developed a novel data acquisition and tomographic reconstruction method, known as equally sloped tomography (EST). By combining EST with electron microscopy, Miao demonstrated electron tomography at 2.4 Å resolution in 2012, the highest resolution ever achieved in any general tomography method. More recently, he applied this electron tomography method to observe nearly all the atoms in a platinum nanoparticle, and for the first time imaged the 3D core structure of edge and screw dislocations at atomic resolution.