Experimental Research On Correlated Imaging With Pseudo-thermal Light

Since 1995,the research group of the University of Maryland for the first time realized correlated imaging experiment,it has attracted scholars from all over the world to explore its physical meaning.Because it is an unusual and novel imaging scheme,correlated imaging also called “ghost imaging”.It can obtain the image of an object by the correlation of two beams of light filed.One beam of light transmit through an object,and collected by a bucket detector without spatial resolution,while the other beam of light collected by a spatial resolution detector without the interaction with that object.By correlating two coincidence signals we can obtain the image of the object.In addition to entangled photons,pseudo-thermal light and true thermal light can achieve correlated imaging.Many scholars have tried to explain this experiment.There are two mainstream explanations of this experiment.One side argues that it should be explained by using quantum theory,while the other side argues that using classical intensity fluctuation correlations also can achieve same goals.In fact,obtain a pseudo-thermal light is more easy than entangled source,and only using thermal light the technology of correlated imaging can enter the practical stage.From the practical point of view,this paper focuses on the theory and experiment of lensless pseudo-thermal light correlated imaging.In this paper,the principle of correlated imaging is explained by classical intensity fluctuation correlations,and then from the point of detector and data processing further analyses were carried out.After that numerical simulation were given by using computer program.Generation of pseudo-thermal light source that satisfies Gauss distribution is the first step.Through using Huygens-Fresnel diffraction integral formula with paraxial approximation,the light field of two detectors can be obtained.()is defined as the transmittance function of that object.In transparent areas,()= 1,otherwise ()=0.At last,by correlating two simulated light field,the image of the object can be retrieved very well.This numerical simulation verified the feasibility of the experiment.In the laboratory,lensless pseudo-thermal light correlated imaging experimental system was set up.And the experiment results show that the image of the object(THU)can be retrieved.Besides that,the influence on imaging when the ground glass was placed in different location is analyzed.In order to improve the noise ratio of imaging,some factors which influence the value of the second-order correlation function were researched.There are three mainly points: the influence of optical path,the influence of detector and the influence of lens.