Influence of laser speckle average size on ghost imaging

The influence of speckle average size on the ghost imaging with pseudo-thermal light was investigated. A binary image and a grayscale image were used as images of an object to be reconstructed. The reconstruction quality was quantified by Peak Signal to Noise Ratio (PSNR) as the measure, while three sets of reconstructed pictures with different size speckles from small to large were compared intuitively. Four correlation imaging methods including Ghost Imaging (GI), Differential Ghost Imaging (DGI), Compressive-sensing Ghost Imaging (CGI) and Pseudo-inverse Ghost Imaging (PGI) were simulated. Then, several groups of speckle fields with a growing size were used to reconstruct respectively by these methods. The simulation result shows that the PSNRs of GI, DGI and PGI are improved to 7 dB remarkable as the speckle size increasing, while the PSNR of the CGI enhances little. Besides, when the object arm and reference arm are not quite symmetrical in the experiment, the speckle size of two arms are deviated slightly. The reconstruction PSNRs of four methods are decreased as the bias increasing and indistinguishable finally. For a distinguishable reconstruction, the allowable deviations of GI and DGI could be bigger than that of the CGI, in which the PGI is the smallest.