Selective probing and imaging in random media based on the elimination of polarized scattering

Abstract

An ellipsometric technique based on angle-resolved light scattering is addressed to open applications in the field of imaging in random media. The first experimental demonstration is given to prove the selective extinction of different scattering sources such as surface roughness and bulk heterogeneity in optical components and liquids. The results are compared with theory.

Light scattering near and from interfaces using evanescent wave and ellipsometric light scattering

“…An important feature of FOVPT which is essential for many applications is a factorization in a polarization term and a term including the surface roughness, described by the mean squared amplitude |Z(q The extinction conditions for the polarization optics therefore do not depend on the roughness. This feature has been used to mask out either bulk or interface scattering, either in scattering measurements [92,94] or in an imaging application [95]. The theoretical description has been generalized to a multi-layer stack with rough interfaces between the layers [96].…”

An enhanced contrast to detect bulk objects under arbitrary rough surfaces

“…In the case of surfaces with very low roughness to wavelength ratio (R q λ ), the ellipsometric parameters, |A p |/|A s | and δ , vary slowly as a function of θ and are independent of the rapid variations of the intensity which form the speckle [9]. When the roughness increases and the slope remains moderated ( 20%), it was experimentally shown [7] that rapid variations (at the speckle scale) appear on the polarimetric phase shift.…”

“…The technique is elementary and uses a retardation device and an analyzer plate that are tuned at each direction of space according to the ellipsometric properties of the scattered field, to selectively eliminate the total field or one component of it. The procedure was shown successful at low scattering levels (the case of slightly rough surfaces or inhomogeneous bulks) since several experiments confirmed the strong reduction of surface scattering to the profit of bulk scattering, and inversely [9,10]. At these low-scattering levels, all scattered fields are proportional to the Fourier Transform of defects (roughness or inhomogeneities), with the result that the ellipsometric parameters do not depend on the microstructure of the samples, but only on the origin of scattering (surface or bulk).…”

Angle-resolved ellipsometric data for selective imaging in scattering media

“…Because the f transformation is linear, selective data can now be addressed with the previous cancellation procedure [4,7,8]. Consider that the scattered field A is emitted when two micro-objects or two defects distributions (surface and bulk for instance) are simultaneously illuminated.…”

“…In many other situations object 1 can still be recognized depending on the z 2 variations. Taking into account the interaction term induces more complexity, but the results often remain successful [6,8].…”