Underwater Ghost Imaging Of Amplitude And Phase Objects

Ghost imaging,also known as correlation imaging and coincidence imaging,is one of the hot and up-to-date technologies in the quantum optics field in recent decades.Compared with the traditional imaging technique,ghost imaging has non-locality,which can obtain the object image in the idle beam by the coincidence calculation.In this thesis,we study the ghost imaging schemes of amplitude and phase objects in underwater environment.The main research works are as follows:Firstly,we demonstrate an experimental study for the ghost imaging of amplitude objects in underwater environment to study the influence of absorption and scattering of underwater environment on the imaging quality.And the influence of temperature gradient,water vibration and turbid medium on the imaging quality are also presented.In the experiment,a31?0.4?0.4m water tank with tap water is used to simulate the underwater environment,where the temperature gradient is produced by a heater inside,the vibration is obtained by a gravity on the water surface,and the turbidity is produced by adding turbid medium CaCO₃ in the water.The experimental result shows that GI has turbulence-free ability under lower temperature gradient,water vibration,and turbid media,where ghost imaging of amplitude objects can still image well.Secondly,we propose a ghost imaging method for a phase object in underwater environment.In order to solve the problem of phase information loss in the correlation calculation of thermal ghost imaging,the coherent detection method is introduced to image the phase object in underwater environment.In the proposed method,the phase of 0 and 2/? pare modulated on speckle patterns that pass through a beam splitter with signal beam,and then two interference measurements are adopted to obtain the light intensity,resulting in the phase information by correlation calculation.At the same time,we use the phase screens model to simulate the underwater turbulent environment.The simulation result shows that only 410 speckle patterns are needed to obtain the image of the phase object by using compressed sensing and Hadamard speckle patterns.Moreover,different mean square temperature dissipation rate,kinetic energy dissipation rate,the ratio of ocean turbulence caused by temperature and salinity,and the internal scale of turbulence in underwater turbulence environment have little effect on image quality.