Optimisation of Low-Coherence Speckle Interferometry (LCSI) for characterisation of multi-layered materials

Abstract

In this paper the optical parameters of Low Coherence Speckle Interferometry (LCSI) are analysed in order to optimise the technique and increase the probing depth. The contrast of the interference signal depends on the configuration of the optical setup and the optical properties of the material. Theoretical investigations and measurements for optimising the beam ratio, the coherence function and imaging parameters are presented. By optimising the interference signal the probing depth of the technique can be extended. This is demonstrated for a semi-transparent polymer material. Finally, measurements of the deformation of interfaces in a multi-layered material are presented.

<title>Low coherence speckle interferometry (LCSI): when speckle interferometry goes sub-surface</title>

“…refractive index changes in the material and restrictions regarding the probing depth. The same groups introduced also a new method for the detection of zero path length difference [10], described how to optimise the interference signal [11] and developed a model to interpret the phase measurement results of LCSI [12]. A comprehensive description of all parts of this work is given in Gastinger [13].…”