Authors: M. Caumont and W.S. Bacsa
Affilation: University Paul Sabatier, France
Pages: 281 - 283
Keywords: diffuse light scattering, optical scanning probe, surface inspection
Overlap of the incident and scattered field from local surface non-uniformities lead to lateral standing waves which can be mapped using a scanning optical probe in collection mode. The lateral standing waves form diffraction fringes in the image plane. The fact that the optical probe is scanned in the proximity of the surface and the visibility of the scattered wave field is amplified by constructive interference with the incident beam, increases considerably the detectability of nano-particles or nanopores on surfaces. We use the discrete dipole model to show how the optical properties of the surface and the scattering particle influence the shape of the diffraction fringes. Scaling of the lateral shift and size of the first diffraction fringe can be used to estimate the distance of the image plan from the surface and the position of the surface non-uniformity. The use of local diffuse light scattering extends the application range of non-contact inspection in that area averaging effects are reduced and the sensitivity is significantly increased.