Imaging polarimetry for the determination of stress constraint in transparent solids

Abstract

Abstract. Using a Mueller matrix polarimeter based on liquid crystal cells [1] and the forward polar decomposition [2], we study the evolution of the birefringence property induced by an increasing compression of a Plexiglas sample. We measure the 2D distribution of the relative retardation į, the azimuth angle Į and the ellipticity angle İ of the sample. A noticeable advantage of such method is the possibility to map the stressinduced birefringence even if the material used for the reflexion implies partial depolarization of the scattered field. More generally, this method will be particularly useful in experimental situations where the light beam undergoes depolarization and/or dichroïsm in addition to birefringence effects because classical birefringence measurement methods are not able to perform an efficient discrimination between these 3 effects. Our experiment shows that the Plexiglas sample under investigation exhibits some weak stress-induced elliptic birefringence. According to simple numerical simulations, this observation is explained by the use of a bi-static illumination/detection configuration.

Full Stokes polarization imaging camera

“…Additionally to the previous application presented, it is possible to integrate it as a fast PSA into a Mueller polarimeter in order to perform retardance mapping. This opens the door to stress measurement 26,27 and various bio-medical imaging applications.…”

“…No numerical estimation of the retardation can be performed here with only a single measurement since many polarization properties are competing. Estimation of Mueller matrix and using a decomposition algorithm 5,26 would provide a numerical estimation of the retardation properties, which can be linked to mechanical stress under certain conditions and assumptions 27 . …”