\section{Measurement principles}
\label{sec:measure}
-In order to develop simple, cost effective and user-friendly probe arrays,
-authors of ~\cite{AFMCSEM11} have developped a system based of interferometry.
+In order to develop simple, cost effective and user-friendly cantilever arrays,
+authors of ~\cite{AFMCSEM11} have developped a system based of
+interferometry. In opposition to other optical based systems, using a laser beam
+deflection scheme and sentitive to the angular displacement of the cantilever,
+interferometry is sensitive to the optical path difference induced by the
+vertical displacement of the cantilever.
+%%RAPH : est ce qu'on pique une image? génant ou non?
+The system build by authors of~\cite{AFMCSEM11} has been developped based on a
+Linnick interferomter~\cite{Sinclair:05}. A laser beam is first split (by the
+splitter) into a reference beam and a sample beam that reachs the cantilever
+array. In order to be able to move the cantilever array, it is mounted on a
+translation and rotational stage with five degrees of freedom. The optical
+system is also fixed to the stage. Thus, the cantilever array is centered in the
+optical system which can be adjusted accurately. The beam illuminates the array
+by a microscope objective and the light reflects on the cantilevers. Likewise
+the reference beam reflects on a movable mirror. A CMOS camera chip records the
+reference and sample beams which are recombined in the beam splitter and the
+interferogram. At the beginning of each experiment, the movable mirror is fitted
+manually in order to align the interferometric fringes approximately parallel to
+the cantilevers. When cantilevers move due to the surface, the bending of
+cantilevers produce movements in the fringes that can be detected with the CMOS
+camera. Finally the fringes need to be analyzed. In~\cite{AFMCSEM11}, the
+authors used a LabView program to compute the cantilevers' movements from the
+fringes.
+
+
+
+
+
\subsection{Architecture}
