Application Of Edge Detection And Ghost Imaging On OAM

Edge detection is the method to obtain the edge information of the target object.Spiral phase contrast(SPC)imaging is a common edge detection method in optics domain,which uses a spiral phase plate(SPP)filter based on orbital angular momentum(OAM)to perform radial Hilbert transform on the object to realize the edge detection.Ghost imaging,also called correlated imaging.Compared with other imaging technologies,the strangeness of ghost imaging lies in the "non-localization" of imaging,that is,if an object is placed on one optical path,the image of the object can be presented on another associated optical path through coincidence measurement.In this thesis,we study the improvement method of SPC imaging and multi-target ghost imaging method based on OAM holography.The main work is as follows:(1)An edge detection scheme based on OAM-based superposed spiral phase plate(SSPP)filter is proposed.The traditional SPC imaging system with topological charge of 1 has the problem of poor edge detection performance.We discussed the influence of SPP filters with different topological charges on the edge detection performance.By using the orthogonal characteristics of OAM,we designed OAM-based SSPP filters to realize Sobel edge detection operator in frequency domain equivalently and greatly improving the edge detection performance of SPC imaging.The simulation results show that,the edge detection performance of OAM-based SSPP filters is better than the traditional SPP filter with single topological charge 1,and the Signal-to-Noise Ratio(SNR)and Root-Mean-Square Error(RMSE)performance are improved over 50%.In addition,we extend this superposition idea to anisotropic edge detection.By superposing the traditional directional edge detection filter,we propose a new filter which can realize multi-directional edge detection.The simulation and experimental results show that,compared with the traditional directional edge detection filter which can only filter the edges in a single direction,the proposed filter has the ability to filter several edges from different directions.(2)We propose a multi-target ghost imaging method based on OAM holography and apply it to multi-image encryption.Firstly,according to OAM holographic technology,we design the OAM-multiplexing hologram by using OAM spiral phase with different topological charge.Then,the OAM-multiplexing hologram is used as the object of ghost imaging.According to the strong selectivity of different OAM incident lights to OAM-multiplexing hologram,the target object information related to the input OAM topological charge is obtained.Finally,different random speckle light fields are irradiated to the target object,and the corresponding bucket detector values are obtained.The information of the target object is directly obtained by using the correlation between the bucket detector values and the corresponding speckle with the compressed sensing algorithm.The simulation and experimental results show that,this method can realize ghost imaging of multiple targets simultaneously.We further apply this method to multi-image encryption scheme and various risks that the key may encounter in the actual transmission process are analyzed by experiment.The results show that the encryption scheme has strong robustness and security.