Simulation And Experimental Study Of Computational Ghost Imaging In Turbulent Water Environment

With the development of ocean exploration and development,the requirements for laser imaging technology in water environment are constantly increasing.Ghost imaging is expected to play an important role in underwater imaging because of its high resolution and anti-turbulence.Both extinction and turbulence in the water affect the quality of Ghost Imaging.Water turbulence is stronger than atmospheric turbulence,and the influencing factors are more complicated.Research on ghost imaging in the turbulent environment of water is still in its infancy.The thesis bases on ocean turbulence spectrum model,power spectrum method,spatial light modulator and heating forced liquid turbulence simulator studies the computational ghost imaging in water turbulent environment.Based on the analytical expression of the spatial light modulator(SLM)modulated light field,the numerical simulation of the pseudo-thermal light source characteristics generated by loading different merged pixel phase maps in the SLM and the SLM fill ratios is analyzed.The quality of computational ghost imaging using pseudo-thermal light source produced by SLM is analyzed by numerical simulation.Through the power spectrum method,a phase screen that can simulate the influence of temperature-induced turbulence in the water is generated,and the computational ghost imaging in the turbulent environment is simulated.The signal-to-noise ratio and resolution of computational ghost imaging in water turbulent environment is simulated,the simulation shows that increase coherence length of the pseudothermal light source can improve the signal-to-noise ratio but reduce the resolution.These results pave the road towards further experiments preparation.The experimental system of computational ghost imaging is designed and built,using the SLM to generate pseudo-thermal light source with different coherence length and experimental studies computational ghost image without turbulence.The experimental results verify the influence of the coherence length of the pseudo-thermal light source on the signal-to-noise ratio and resolution in the simulation.According to the liquid turbulence simulator developed in the laboratory,the experimental system is designed to measure the simulated turbulence generated by the liquid turbulence simulator,Fried parameter is analyzed.Comparing the simulated turbulent logarithmic temperature spectrum with the turbulent energy spectrum of the natural water,the results show that the simulated turbulent flow has uniform isotropic characteristics and is similar to the natural turbulent flow in water.By calculating the equivalent optical path,the computational ghost imaging experiment in the no-turbulent environment of water is completed,and the imaging result can restore the target object.The heating forced liquid turbulence simulator is used to simulate the turbulent flow of the Fried parameter in the distribution of 0.4cm-1.9cm,the ghost imaging experiment in the water turbulent environment is carried out.The experimental results show that the increase of turbulence intensity will destroy the imaging quality of computational ghost imaging,but the computational ghost imaging has an inhibitory effect on the turbulence effect.The position of the target imaging result is slightly drifted,and the cause of the phenomenon is analyzed.