Imaging through a scattering medium by speckle intensity correlations

Abstract

In this paper we analyze an imaging technique based on intensity speckle correlations over incident field position proposed in [J. A. Newmann and K. J. Webb, Phys. Rev. Lett. 113, 263903 (2014)]. Its purpose is to reconstruct a field incident on a strongly scattering random medium. The thickness of the complex medium is much larger than the scattering mean free path so that the wave emerging from the random section forms an incoherent speckle pattern. Our analysis clarifies the conditions under which the method can give a good reconstruction and characterizes its performance. The analysis is carried out in the white-noise paraxial regime, which is relevant for the applications in optics that motivated the original paper.Keywords: Waves in random media, speckle imaging, multiscale analysis. Imaging by speckle intensity correlationsReceived xxxx 20xx; revised xxxx 20xx.

Scintillation of Partially Coherent Light in Time Varying Complex Media

“…As above the term in the square brackets corresponds to scintillation contribution from the fluctuations in the source and this contribution is damped by fast temporal decorrelation of the medium fluctuations (small g τ ), moreover, by smoothing at the detector. Note that this term corresponds to the first term in the square brackets in (23). Indeed, the last two terms in the square brackets in (23) becomes small when s is reduced so that λoL m s…”

“…A more detailed model for the detector, in particular a discussion of the role of finite sized pixels of a (CCD) camera can be found in for instance [23,29].…”

“…The kernel (24) depends on the two-point statistics of the random medium fluctuations and reflects cumulative scattering effects over the propagation distance L. Note that g = 0 corresponds to the situation with intensities of wave fields having propagated through uncorrelated random media and that indeed Q 0 (L) = 0. The first term in the square brackets in (23) corresponds to the scintillation contribution from the fluctuations of the source and this contribution is damped by temporal decorrelation of the medium fluctuations as well as temporal averaging at the detector. The second term in the square brackets is the scintillation contribution produced by the random medium fluctuations and is again damped by temporal decorrelation of the random medium fluctuations.…”

Speckle Memory Effect in the Frequency Domain and Stability in Time-Reversal Experiments

“…At a single frequency this process corresponds to phase conjugation or reemission of the complex conjugate of the recorded wave field by the TRM; with some abuse of notation we refer to this process as time-harmonic time reversal. It has been shown that the speckle memory effect [7,11] allows to focus on a neighboring point close to the original target point [33,34,35], which opens the way for the transmission of spatial patterns [16,17,18,28]. Indeed, one the main manifestations of the spatial memory effect is the following one: By applying an appropriate and deterministic spatial phase modulation to the conjugated source field in the second step of the time-reversal experiment (Figure 1.2(b)) one can achieve that the focusing (red spot) in the bottom right plot is shifted.…”

Enhanced Backscattering of a partially coherent field from an anisotropic random lossy medium

“…We here consider a situation where we exploit the coherent part of the backscattered intensity, the enhanced backscattering cone, and seek configurations where the speckle noise can be mitigated. There are, however, other imaging modalities that seek to exploit the incoherent part in the speckle, the speckle correlations, for imaging [16,17].…”