Design And Implementation Of The Ptychographic Scanning System

Ptychography is one of the coherent diffractive imaging method without the use of lenses, which leads to resolution improvements and unconstraint of the object size. Furthermore, it has the merits of strong portability and does not need a stable reference wave. Now, the proof-of-principle experiments have been performed in the visible light and X-ray domains, etc.. Therefore, it has the promising application in many fields, such as microscopy, three-dimension surface measurement and information security, etc.. However, the study of ptychography is still in the primary stage, many key elements that influence the imaging performance need the further study.In this thesis, first of all, we introduce the background and significance of the research, the basic concept, development and application of ptychography. Then, the basic theories of ptychography algorithm are analyzed, including diffractive micro-optics theory (the Kirchhoff diffraction theory and angular spectrum theory are mainly described), and phase retrieval algorithm (GS algorithm and Y-G algorithm). Based on the current work of ptychography, our major researching work is shown as bellow:(1) Three ptychography systems have been designed to improve the imaging quality, the first one is a ptychography system based on a single random phase encoding, the second is a generalized ptychography system with diverse probes, and the third is multi-wavelength ptychography system. Due to the limitations of the laboratory conditions, The first two systems are performed only by numerical simulation, the latter one system is performed by Both optical experiments and numerical simulation. The study results shows:1. The first system not only has a much faster convergent speed obtainable, but also the robustness is considerably improved. The reason is that the information of the sample associated with probes is uniformly distributed to a set of diffraction patterns, due to the introduction of single random phase encoding.2. The second system uses the diverse probes, which breaks through probes?shapes, sizes and scanning modes, asymmetrical and irregular overlapped distribution actually brings about much more flexibility for ptychography.Unlike the traditional method, without the limitations of probes?forms, there is more freedom in performing the overlapping to pursue the better recovered quality.3. Multi-wavelength ptychography has the higher anti-noise ability, convergence rate, and imaging quality compared with the single-wavelength ptychography. However, the imaging quality will reach a certain limit with the increase of the wavelength number. In the practical ptychography system,, it should be based on the application requirements, the actual operating conditions and cost of the device to select the appropriate system solutions.(2) Ptychography has been applied to the field of information security, we combine the three-dimensional ptychography with three-dimensional object hiding, which can operate the three-dimensional object in a perfect way. The three-dimension object acquisition and ptychographic encoding process are performed completely optically, both optical experiments and numerical simulation demonstrate the feasibility and effectiveness of the proposed system. In addition, the proposed three-dimensional object hiding system has a high level of security, because all of the probes, wavelength and the distance between each slice can be served as keys. Moreover, it has high quality of hiding and extracting, and is robust to the distortion of noise and occlusion.