Sub-Rayleigh Resolution Imaging By Spatial Low-pass Filtering

"Ghost" imaging(GI),which is an investigated imaging technology based on second-order intensity correlation,has advantages for practical applications compared with traditional imaging,such as high resolution;anti-atmospheric turbulence;lensless GI.However,there are also disadvantages with GI.The most important thing is that the low signal-to-noise ratio(SNR).In particular,GI contrast and signal-to-noise ratio are lower for complex grayscale target objects.At the same time,the GI is limited by the Rayleigh diffraction limit just like the traditional imaging.Even if the lensless GI is not an exception.In recent years,how to improve the resolution of the associated imaging system has been became an important research focus in the field of optical imaging.In this paper,the threshold filtering technology is introduced into the GI field,we propose a scheme with spatial low-pass filtering,in the international community.This new scheme mimics the detection of optical intensity distributions with a spatial low-pass filter,and we call it spatial low-pass filtered ghost imaging(FGI).It is found that the resolution is strongly dependent on the filter threshold,which can have a wide range of values while still surpassing the diffraction bound.It is surprising that,when a suitable filter threshold is chosen,the resolution of the reconstructed image can exceed the Rayleigh diffraction limit by a factor of about 2.6.By optimizing the system,the sub-Rayleigh resolution factor can be further improved.The low-pass FGI technique is simple to implement without adding complexity or sacrificing too much image quality.It offers a general and alternative approach applicable to all fields of imaging where higher resolution is needed,and can be applied to any existing lensless GI schemes of any wavelength,including x-ray,terahertz,or particle sources.