Investigation To Improve The Quality Of Ghost Imaging From The Theory And Experiment

A ghost-imaging (GI) technique is a novel imaging method that can non-locally retrieveinformation of an unknown object from the correlation of the intensity fluctuations on twooptical paths. An unknown object and a detector without resolution are concluded in one path,and the other path travel through free space and conclude a detector with high-resolution. Thehigh-resolution image or diffraction fringe of the object can be obtained by the correlationmeasurement of the intensity fluctuations, while the image can’t be retrieved from anyoneoptical path alone. The combine between the GI technique and other advanced techniques hasbeen explored continuously two decades, and it can break through the limitation of thetraditional imaging and realize the high image quality of the GI concluding thethree-dimensional GI and hologram GI. Thus the GI can be used to the practical applicationsfrom the lab research with the development of these techniques. In this paper, the theoreticaland experimental studies are given to improve the image quality of the GI system, and thesystem parameters are considered, such as the defocusing length, the size of the detector, thesurface roughness of the object, the angle of the reflection and the shaped sources. The paperis organized as follows.The research background and significance of the GI are elaborated in chapter1. Then theresearch status of the GI is summarized and some questions about the current GI techniqueare proposed. The main research content in this paper is given to improve the image quality ofGI by analyzing the effect of the system parameters on the GI system. The coherence of thelight field and some statistical properties of the pseudo-thermal source are introduced inchapter2, and then the principle of the thermal GI is proposed and illustrated from the theoryand experiment.Chapter3gives the experimental results about the influences of the parameters on the GIquality, and the effects of the detector’s size and defocusing length on the lensless ghostdiffraction are mainly considered. Three experiments are designed to synthetically study theeffects of the detector’s size and defocusing length on the quality of the lensless ghostdiffraction, and the corresponding theories are given to analyze the experimental results. In chapter4, the theory analysis of the GI and GD for a reflective object is demonstrated toconsider the effects of the object’s surface roughness and the reflective angle on the quality ofGI and GD. The expressions of the reflective GI and GD are derived by a simple scatteringmodel and the classical coherent optical theory. Then the numerical results are given toanalyze the influences of the object’s surface roughness and the reflective angle on the qualityof GI and GD. The theoretical and experimental results are demonstrated about the shapedsources to improve the image quality of GI in chapter5. The based model of the atmosphericturbulence, the point spread function for the optical imaging system and the operationprinciple of the spatial light modulator are introduced firstly. Then we derive the expression ofGI based the different shaped sources, including a cosine function and a hyperbolic cosinefunction to modulate the Gaussian sources. Besides, the Gaussian-Schell sources shaped bythe hyperbolic cosine function are used to improve the quality of GI through atmosphericturbulence. The corresponding numerical results are presented to see the visual interpretation.Using the spatial light modulator to shape the beam, the experimental results are obtained by ahyperbolic cos-Gaussian Schell-model source to improve the image quality of GI.The paper is concluded and the development tendency and apply perspective of the GItechnique are analyzed. Finally, we propose the next work plan.