Acquiring information such as the shape, height, and image of a target surrounded by scattering obscurants is a challenging problem involving several random processes. In this work, we approach and compare this problem using theoretical and experimental results from the speckle correlation method. This method involves subjecting the target to illumination by random fields generated by Gaussian and perfect optical vortex (POV) beams to evaluate the orientation of the target. We show that the orientation of the object can be obtained from vortex speckles, whereas the Gaussian speckles provide less information regarding the orientation. Additionally, we demonstrate that the POV speckles have better sensitivity to detect the edges of a target than the Gaussian speckles.
One of the methods for detecting an object behind obscurants primarily relies on the well-known principle that the autocorrelation of the object’s reflectance is effectively equivalent to autocorrelation of the reflected intensity captured after the obscurants in conventional incoherent illuminations. Here, we present a novel approach to acquiring information about an object embedded in obscurants by illuminating it with different modes of a Bessel-Gaussian beam in the far field also known as a perfect optical vortex beam (POV). Each POV with different topological charges scattered from a turbid medium induces the quasi-independent speckle fields. Through numerical analysis, we determine the optimal configurations of POVs for the number of shots and the size of speckles required for effectively imaging a hidden object. By employing the prevalent imaging method based on the ensemble-averaged intensity for each illumination, we effectively reconstruct the object's details. Unlike conventional spatially incoherent sources, our approach is expected to not only efficiently identify distant objects but also offer versatile applications through adjustment of the speckle aspect ratio.
We develop analytical expressions using the Fresnel diffraction theory of the spatial coherence function of speckle fields generated by scattering a Mathieu beam through a diffuser modelled as a delta correlated phase screen.
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