Analysis of polarization speckle for imaging through random birefringent scatterer

Abstract

Propagation of a coherent light through an anisotropic random medium generates randomly polarized field, known as polarization speckle. In this paper, an experimental technique is proposed and demonstrated to recover the transmittance of a polarized object from polarization speckle. Recovery of the polarized object from polarization speckle is made possible by combining the far-field intensity correlation of the object speckle with off-axis holography to determine the complex coherence function of the speckle. The desired object speckle which is uniformly polarized is filtered from the polarization speckle using a polarizer. The results are compared with the case where the complex coherence function is determined in the absence of the polarizer.

Controlled modulation of depolarization in laser speckle

“…Apart from different interesting properties observed in speckle generated from a single scattering medium, the study of superposition of two different speckles also has gained attention because of its wide application in different studies. The speckle interferogram, obtained from the superposition of two speckles is useful in different kinds of object recovery through a random scattering medium, [21,22] and in other different physical property [23] and non-invasive bio-medical studies [24]. It is observed that the superposition of two speckles, depending on their mutual correlation, changes the statistics of the resultant speckle [25].…”

Spatial statistics of superposition of two uncorrelated speckle patterns with polarization diversity

“…The spatial CP property of a random field distribution is studied from the two-point intensity correlation function of the recorded intensity distribution, I(𝐫) following Ref. [15] or using the CP matrix, (𝐫 𝟏 , 𝐫 𝟐 ) of the random field following Ref. [6].…”

“…In order to calculate the DoC of the superposed random field using Eq. ( 4), we exploit the established fact that in case of superposition of two mutually uncorrelated fields, the CP matrix of the superposed random field can be written as the sum of the CP matrices of the constituent random fields under the assumptions that both the random fields follow Gaussian statistics [3,15]. Hence, the CP matrix of the superposed random field,  S (𝐫 𝟏 , 𝐫 𝟐 ) can be written as…”

“…The two-point intensity correlation based approach is one of the preferred technique for the imaging purpose. The spatial characteristics of a speckle pattern has been reported to play an important role in the object information retrieval process, and it is observed that the visibility of the correlation function of a speckle pattern determines the quality of the retrieved object [15]. The quality of the retrieved object increases with the increase of the visibility of the correlation function and hence, several techniques have been proposed to increase the visibility [28,29].…”

“…In the off-axis speckle holography, speckle patterns from two different sources are interfered, and as the speckle patterns are generated from two different sources, they are mutually uncorrelated. Apart from the amplitude imaging, the off-axis speckle holography based approach is also useful for polarization imaging through a random scattering medium [15]. As the speckle superposition has a wide range of applications, it is important to characterize the spatial statistics of the superposed speckle pattern in detail.…”