Abstract
Ghost imaging (GI) is an indirect imaging approach that can retrieve an object’s image even in a harsh environment through measuring the fourth-order correlation function (FOCF) between the signal and idle optical paths. In this paper, we study lensless GI with a partially coherent beam carrying twist phase, i.e., twisted Gaussian Schell-model (TGSM) beam, in the presence of oceanic turbulence. Explicit expression of the FOCF is derived based on the optical coherence theory and Rytov approximation, and the effects of the twist phase and the oceanic turbulence on the quality and visibility of image are investigated in detail through numerical examples. Our results show that the simulated oceanic turbulence strongly affects the GI. The quality of image decreases monotonously with an increase of the strength of turbulence whereas the visibility increases. When the illumination light carries a twist phase, the visibility of the image is improved while the quality of the image is reduced in contrast to those without a twist phase. By properly selecting the strength of the twist phase, the image can still be maintained at an acceptable level of quality with high visibility. Furthermore, it is found that the quality and visibility of the ghost image are less affected by the oceanic turbulence using a TGSM beam with larger twist factor. Our findings will be useful for the application of GI in an oceanic turbulent environment.
Highlights
Ghost imaging (GI), a kind of nonlocal imaging method, was firstly observed in an experiment by Pittman et al using entangled photon pairs through spontaneous parametric down-conversion (SODC) in 1995 [1,2]
GI with a Gaussian Schell-Model (GSM) beam based on the classical optical coherence theory [6,7], and the results revealed that the image quality and visibility closely depended on the coherence properties of the light and it is impossible to observe a ghost image with both high quality and high visibility
Our aim in this paper is to study the effects of twist phase on GI in the presence of simulated oceanic turbulence
Summary
Ghost imaging (GI), a kind of nonlocal imaging method, was firstly observed in an experiment by Pittman et al using entangled photon pairs through spontaneous parametric down-conversion (SODC) in 1995 [1,2]. The properties of GI in a turbulent atmosphere, such as quality and visibility, have been studied extensively by other researchers [26,27,28], and the results showed that the quality of the image cannot be immune to turbulence, but the GI can greatly reduce the turbulence-induced degeneration compared to conventional imaging system. The visibility and quality of the image in GI system in an underwater environment have been deeply investigated by some groups [32,33], and the results showed that the GI can reduce the effects of water turbulence compared to the conventional imaging system. Examples of the formed image of double slits, and analyze the effects of the twist phase and oceanic turbulence on visibility and quality of the image.
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