Reflective Ghost Imaging Research Articles

Application of the Five-Step Phase-Shifting Method in Reflective Ghost Imaging for Efficient Phase Reconstruction.

The conventional approach to phase reconstruction in Reflective Ghost Imaging (RGI) typically involves the introduction of three reference screens into the reference path, deeming the Fourier transform step indispensable. However, this method introduces complexity to the system and raises concerns regarding potential errors in phase retrieval. In response to these challenges, we advocate for adopting the Five-Step Phase-Shifting (FSPS) method in the RGI system. This method presents two key advantages over traditional approaches: (1) It streamlines the phase reconstruction process by eliminating the requirement for a Fourier inverse transform. (2) It avoids the need to insert objects into the reference optical path, simplifying the computation of reference optical path intensity and enabling seamless application to Computational Ghost Imaging (CGI), overcoming the constraints of Dual-Arm Ghost Imaging (DAGI). We substantiate the theoretical proposition through numerical simulations involving two intricate objects. Furthermore, our discussion delves into exploring the influence of varying reflective angles on the phase reconstruction performance.

反射式鬼成像在海洋湍流中的成像分析

反射式鬼成像在海洋湍流中的成像分析

Positive influence of the scattering medium on reflective ghost imaging

The scattering medium is usually thought to have a negative effect on the imaging process. In this paper, it is shown that the imaging quality of reflective ghost imaging (GI) in the scattering medium can be improved effectively when the binary method is used. By the experimental and the numerical results, it is proved that the existence of the scattering medium is just the cause of this phenomenon, i.e., the scattering medium has a positive effect on the imaging quality of reflective GI. During this process, the effect from the scattering medium behaves as the random noise which makes the imaging quality of binary ghost imaging have an obvious improvement.

Effects of incident angles on reflective ghost imaging through atmospheric turbulence

The influence of the incident angle on the imaging quality of reflective ghost imaging is investigated through atmospheric turbulence. It is shown that under mediate turbulence, small angles have almost no effect on the imaging quality, while the result for direct imaging gets slightly worse. An increase of the incident angle leads to the degradation of the imaging quality of direct imaging and ghost imaging, while the imaging quality of the latter is better under the same angle and turbulent intensity. For large angles, the image from direct imaging cannot be distinguished under mediate turbulence, but ghost imaging can obtain a relatively good ghost image. Moreover, the relationship between the fidelity and the incident angle under different turbulent intensities is presented.

Robust reflective ghost imaging against different partially polarized thermal light

We theoretically study the influence of degree of polarization (DOP) of thermal light on the contrast-to-noise ratio (CNR) of the reflective ghost imaging (RGI), which is a novel and indirect imaging modality. An expression for the CNR of RGI with partially polarized thermal light is carefully derived, which suggests a weak dependence of CNR on the DOP, especially when the ratio of the object size to the speckle size of thermal light has a large value. Different from conventional imaging approaches, our work reveals that RGI is much more robust against the DOP of the light source, which thereby has advantages in practical applications, such as remote sensing.

Reflective ghost imaging free from vibrating detectors**Project supported by the National Natural Science Foundation of China (Grant Nos. 61372102 and 61571183).

The vibration is one of the important factors affecting imaging quality of conventional remote sensing imaging because the relative motion between the imaging system and the target can result in the degradation of imaging quality. The influence of the vibration of the detector in the test path on reflective ghost imaging (RGI) is investigated theoretically and experimentally. We analyze the effects of the vibrating amplitude and velocity. The results demonstrate that the microvibrations of the bucket detector have almost no impact on the imaging resolution and signal-to-noise ratio (SNR) of RGI, i.e., the degradation of imaging quality caused by the vibration of the detector can be overcome to some extent. Our results can be helpful for remote sensing imaging.

Ghost Imaging for a Reflected Object with Large Incident Angles

Incident angle of light source is a key factor that affects imaging resolution of direct optical imaging for a reflected target. For a large incident angle, it is easy to form the “blind area” in which the image of the object cannot be distinguished clearly. Using classical statistical optics, we study ghost imaging (GI) for a reflected object numerically and experimentally and show that by measuring the second-order correlation of light fields, a ghost-image with good quality can be retrieved in the “blind area.” Unlike transmitted ghost imaging, which is affected greatly by the transverse size of the test detector, the size has almost no effect on the resolution of reflective ghost imaging when the blind area appears.

Influence of detector response speed on the contrast-to-noise ratio of reflective ghost imaging

Abstract The influence of detector response speed on the contrast-to-noise ratio (CNR) of reflective ghost imaging (RGI) is studied. To mimic the situation of a slow response detector, the illuminating speckle patterns are replaced with the sum of uncorrelated speckle patterns for each measurement. An expression for the CNR of RGI with added speckle patterns is derived. By employing a light projector to provide spatially incoherent structured illumination in a computational ghost imaging system, we perform computational RGI based on added speckle patterns. The experimental results show that when up to 40 uncorrelated speckle patterns are added together in each measurement, the CNR of computational RGI obtained from 5000 effective measurements remains almost the same as the conventional computational ghost imaging. The reason for this is that the image quality of RGI depends on the kurtosis of intensity fluctuation of speckle field instead of the contrast ratio of speckle pattern. The experimental results agree with the theoretical prediction.

Effects of light intensity on reflective ghost imaging

In this letter, we analyze the effects of light intensity on reflective ghost imaging with thermal source. We find that the brightness of reflective ghost image can be changed by modulating the light intensity of the source and the splitting ratio of the beam splitter. The signal-to-noise ratio will be improved by increasing the light intensity of the source. More important, we can obtain the reflective ghost image with high image quality by adopting a low light intensity signal beam and a high light intensity reference beam, which is better than the classical optical imaging, because it can reduce the effects of light on the object.

Real-Time Data Acquisition for Long-Distance Reflective Ghost Imaging Experiment

We present a real-time data acquisition (DAQ) system for the long-distance reflective ghost imaging experiment which has broad application prospects in remote sensing. In the experimental setup, the light from a pseudo thermal light source is separated into signal beam and reference beam. The signal beam illuminates the target, and then the reflected light is collected by a bucket detector. In the mean time, the reference beam is directly captured by an area detector. In order to obtain the target image, the experiment requires high-speed and high-precision correlated data acquisition to collect the light intensity fluctuation in the signal beam and the reference beam. Furthermore, to reduce imaging time, real-time data acquisition is also required. The DAQ system consists of a photon-multiplier tube (PMT), a charge-coupled device (CCD) camera, a DAQ module and DAQ software. The CCD camera as the area detector connects to computer via Gigabit Ethernet. The PMT and a telescope compose the bucket detector which outputs signals to the DAQ module. The DAQ module sends acquired data to computer through universal serial bus (USB). The DAQ software collects the data and reconstructs the target image. The results of electronic tests and experiments show that the DAQ system satisfies the requirements of the experiment.

Reflective ghost diffraction for objects with rough surfaces

Reflective ghost diffraction (GD) for objects with rough surfaces is investigated theoretically and numerically. Using a speckle model to describe the reflectivity of the object with variable rough surfaces, the incident and reflective angle-dependent diffraction condition is obtained, and the analytical expression of the reflective GD is derived. Numerical simulations are given to show how the height variance and correlation length of the object and the reflective angle in the experimental scheme can affect the quality of the reflective GD. Specifically, we find that the changes of diffraction patterns of both the simple objects and the complicated objects are sensitive to parameters such as the reflective angle and the surface fluctuation. Additionally, comparative studies on both reflective GD and ghost imaging (GI) have also been performed. We find that reflective GI is more robust against system parameters than reflective GD. These results may be useful for future experimental works.

Reflective ghost imaging with classical Gaussian-state light

In this letter, we use quantum description and the Gaussian state to study reflective ghost imaging with two classical sources, and to provide their expressions. We find that the reflective ghost imaging of a rough-surfaced object, using Gaussian-state phase-insensitive or classically correlated phase-sensitive light, can be expressed in terms of the phase-insensitive or phase-sensitive cross-correlations between the two detected fields, including a background term. Moreover, reflective ghost imaging with two classical Gaussian-state lights is shown to have similar features as spatial resolution and field of view.

Reflective ghost imaging through turbulence

Recent work has indicated that ghost imaging may have applications in standoff sensing. However, most theoretical work has addressed transmission-based ghost imaging. To be a viable remote-sensing system, the ghost imager needs to image rough-surfaced targets in reflection through long, turbulent optical paths. We develop, within a Gaussian-state framework, expressions for the spatial resolution, image contrast, and signal-to-noise ratio of such a system. We consider rough-surfaced targets that create fully developed speckle in their returns, and Kolmogorov-spectrum turbulence that is uniformly distributed along all propagation paths. We address both classical and nonclassical optical sources, as well as a computational ghost imager.