An enhanced contrast to detect bulk objects under arbitrary rough surfaces

Abstract

We study a selective light scattering elimination procedure in the case of highly scattering rough surfaces. Contrary to the case of low scattering levels, the elimination parameters are shown to depend on the sample microstructure and to present rapid variations with the scattering angle. On the other hand, when the slope of the surface is moderated, we show that this parameters present smoother variations and little dependence to the microstructure, even when the roughness is high. These results allow an important selective reduction of the scattered light, with a basic experimental mounting and an analytical determination of the elimination parameters. Such selective scattering reduction is demonstrated by simulations and experiments and applied to the imaging of an object situated under a highly rough surface.

Separation of surface and bulk reflectance by absorption of bulk scattered light

“…Angle-resolved ellipsometry has proved to be a successful technique, although the method becomes increasingly complex when analyzing highly scattering materials with significant surface roughness [23][24][25][26]. A completely different approach is to coat the surface of the sample with a thin opaque metallic layer, thereby blocking the bulk reflectance [27].…”

Angle-resolved ellipsometric data for selective imaging in scattering media

“…However we have seen that all objects whose diffracted fields can be predicted by perturbative theories can be considered as known, including the case of surface roughness or bulk inhomogeneities. Indeed for these objects the z 2 number was shown to be not dependent on microstructure [4], so that A 1 can be recovered from relation (6). This result remains valid for high scattering surfaces since their polarization behaviour is similar to slightly inhomogeneous surfaces [6].…”

“…Indeed for these objects the z 2 number was shown to be not dependent on microstructure [4], so that A 1 can be recovered from relation (6). This result remains valid for high scattering surfaces since their polarization behaviour is similar to slightly inhomogeneous surfaces [6]. In many other situations object 1 can still be recognized depending on the z 2 variations.…”

“…Indeed the case of arbitrary rough surfaces is most often similar to that of slightly rough surfaces; this is due to the fact that these rough surfaces most often exhibit moderate slopes (<30%) in the optical bandwidth, and rigorous electromagnetic theories predict variations of their cancellation number z = -A S /A P at moderate angles nearly identical to those given by perturbative theories, even when specular reflection has totally vanished [6]. Arbitrary bulk samples are more complex to investigate, due to the variety of their index statistical moments.…”

“…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].…”