Method And Experimental Research Of Computational Ghost Imaging Based On Optical Fiber Phased Array

Ghost imaging,also known as correlated imaging,is a noval optical imaging system developed in recent decades.Because of its non-local imaging characteristics,it has great advantages in anti-noise and anti-turbulence disturbance,and has become a research hotspot and frontier technology in the field of optics.Computational ghost imaging(CGI)can obtain reference light field by means of calculation,without the need of reference light path,which greatly simplifies the system and widens the application field of ghost imaging.Computational ghost imaging system based on fiber phased array uses the synthetic technology of high power fiber laser,uses optical fiber array as constraint heat source,and receives signals through multi-channel.It increases the projection speed of speckle field and also reduces the requirements of sampling frame number and computational complexity,and this has important research significance and application value to the long-range target detection imaging.Based on the fiber phased array computational ghost imaging system model and aiming at the differences between the actual optical fiber array model and the ideal mathematical model,this paper numerically analyzes the influence of the key parameters of optical fiber array,such as beam waist,amplitude distribution and phase distribution,on the optical field distribution and imaging performance.The results show that the difference of waist radius and amplitude has the least effect on the distribution of optical field.When the intensity distribution of the sub-beam is not Gaussian,the effect is greater.The phase distribution has the greatest effect on the light field distribution.The correlation coefficient is used as the evaluation parameter.The results show that when the correlation coefficient between the calculated reference optical field distribution and the actual target optical field distribution is greater than 0.9,and a better imaging effect can be obtained with fewer sampling frames.When the correlation coefficient is between 0.8 and 0.9,better imaging effect can be obtained by increasing the number of sampling frames.In addition,the CGI imaging performance of the ghost imaging algorithm is better when there is an error between the calculated light field and the actual light field distribution.Through the experiment measurement of optical fiber array amplitude distribution,the beam waist and the distance between array and the relative position of the light beam is used to modify the ideal model.The light intensity distribution at the end of the fiber array is reconstructed by using the actual model parameters,which is used as the initial surface light intensity distribution of the reference light field to make the calculated light field closer to the actual light field distribution.In order to improve the control precision of lithium niobate phase modulator,the extreme value measurement method of half wave voltage is improved based on least square method,and the measurement accuracy of half wave voltage is improved effectively.In this paper,we set up a computational ghost imaging experimental system with a square fiber array pseudo thermal light source as the transmitter and a near-infrared camera as the receiver,and the reference light field acquisition experiment is carried out.It is proved that the correlation coefficient between the reference light field distribution calculated by the modified model and the actual light field can reach more than 0.85.On this basis,a two-dimensional computational ghost imaging experiment based on fiber phased array system is realized.