Study On The Influence Of The Relationship Between Light Source Bandwidth And Target Object On Correlation Imaging

Correlation imaging scheme provides a method to measure the target object in complex environment.It uses the first signal to measure the target object and channel.At the same time,the second signal is used to measure the channel.By comparing the differences between the two signals,the object can be reproduced from the channel noise.This scheme has good potential applications in resisting environmental interference and long-distance imaging.However,with the development of correlated imaging,the imaging effect is often not ideal in the case of limited signal sampling.To improve the imaging quality under the condition of limited signal samples,this paper studies the correlated imaging system from the spatial frequency domain.The main work is as follows:(1)A correlation imaging scheme is proposed to improve the performance by controlling the bandwidth of light source.Taking a simple object as an example,it is proved in the ideal channel that controlling the spatial bandwidth of the light source can reduce the source redundancy,eliminate the system noise caused by this redundant signal,and improve the imaging quality.It is proved in Gaussian channel that controlling the bandwidth of light source can also reduce the damage of channel noise to the correlation of two optical paths,and improve the reliability of the system in noise environment.Compared w ith two improved methods — difference algorithm and compressed sensing algorithm,which are mature in the field of correlation imaging,the results show that in the same Gaussian channel,the method of controlling the light source bandwidth can obtain higher quality imaging with lower number of samples.Finally,two important rules of the influence of light source bandwidth on imaging are summarized: first,the narrower the spatial bandwidth of light source,the more obvious the suppression of system noise and channel noise;second,the system needs sufficient light source frequency band to carry the information of the target object.(2)The selection of light source bandwidth in practical application is studied,and the relationship between light source bandwid th and target object is gradually extended to any binary object and gray object.In the process of reducing the bandwidth of light source,the energy distribution of imaging in spatial domain is gradually concentrated,on the one hand,the image details ar e gradually lost,on the other hand,the suppression of background noise is strengthened.When the influence of image detail loss is greater than that of noise suppression,the SNR of imaging will decrease.Therefore,this is a scheme to enhance image quality at the expense of image details.The limit of reducing the bandwidth of the light source is to ensure that the light source has sufficient bandwidth to carry rich object information.In order to analyze the needs of different objects for the bandwidth of the light source,this paper observes the imaging system from the perspectives of spatial domain and spatial frequency domain.After a large number of tests: for binary objects,it is necessary to ensure that the frequency band of the light source is su fficient to carry more than 50 % of the energy of the target object,and for gray objects,the light source must carry at least 90 % of the energy of the target object;on the other hand,whether binary objects or gray objects,to ensure adequate object i nformation,the requirements of light source can be summarized as: the limit of normalized cut-off frequency is generally distributed between 0.1 and 0.4.