Design And Research Of Asymmetrical-arm Ghost Imaging Experiment

Ghost imaging is a new type of imaging technique.It obtains the image of the object by the correlation of the light field.This imaging technique is more novel or strange than the traditional lens imaging,so it is called ghost imaging.The pseudo-thermal light source is easy to prepare and the coherence time and coherence space of the pseudo-thermal light source can be adjusted flexibly,so it is more practicable.This paper puts emphasis on the pseudo-thermal light ghost imaging instead of entangled source ghosting imaging.In the experiment,a point detector receives total intensity from reflection or transmission of the object,so it greatly reduces requirement for the array detector and the imaging will succeed under very low light conditions.Atmospheric turbulence under real conditions can greatly reduce the imaging quality,but the pseudo-thermal light ghost imaging can resist the influence of atmospheric turbulence.These prominent advantages of ghost imaging provides a strong guarantee for the practical application.This paper focuses on the application of pseudo-thermal light ghost imaging in long distance and the designed experiment successfully detects the image of objects beyond one hundred meters.The author makes effort in detecting object size,improving the imaging quality and reducing the imaging time,which achieves good results.Firstly,the principle of pseudo-thermal light lensless ghost imaging is deduced again.The experiment of symmetrical-arm pseudo-thermal light ghost imaging is carried out and the wonderful experimental results are obtained.By adding a delay to the point detector during data acquisition,a new way to measure the size of an object is found.This method does not require prior knowledge of the resolution of the array detector,but it is more time-consuming.Secondly,the paper clarifies the experimental differences between asymmetric-arm ghost imaging and symmetrical-arm ghost imaging.By analyzing,we conclude that the pseudo-thermal light ghost imaging used in this paper is insensitive to the accuracy of synchronization time.The author separately added two lens to two arms to eliminate the space difference that asymmetry of the arms brings,successfully detecting the object in 100 meters distance.In addition,the author draws on the experience of predecessors and uses a method of compressing sensing and prebuilt reference speckle to reduce the experimental time.Finally,the author proposes a method of using a lighting field matching the size of the object to improve the imaging quality under the real environment and the designed experiment verify the method.Image quality evaluation criteria are numerous and complex.By analyzing the similarities and differences between different indicators,the author finds that contrast-to-noise ratio(CNR)and image mutual information(IMI)reflects the size effect preciously.