\section{Introduction}
-%% blabla +
+Cantilevers are used inside atomic force microscope which provides high
+resolution images of surfaces. Several technics have been used to measure the
+displacement of cantilevers in litterature. For example, it is possible to
+determine accurately the deflection with optic
+interferometer~\cite{CantiOptic89}, pizeoresistor~\cite{CantiPiezzo01} or
+capacitive sensing~\cite{CantiCapacitive03}. In this paper our attention is
+focused on a method based on interferometry to measure cantilevers'
+displacements. In this method cantilevers are illiminated by an optic
+source. The interferometry produces fringes on each cantilevers which enables to
+compute the cantilever displacement. In order to analyze the fringes a high
+speed camera is used. Images need to be processed quickly and then a estimation
+method is required to determine the displacement of each cantilever.
+In~\cite{AFMCSEM11} {\bf verifier ref}, the authors have used an algorithm based
+on spline to estimate the cantilevers' positions. The overall process gives
+accurate results but all the computation are performed on a standard computer
+using labview. Consequently, the main drawback of this implementation is that
+the computer is a bootleneck in the overall process. In this paper we propose to
+use a method based on least square and to implement all the computation on a
+FGPA.
+
+The remainder of the paper is organized as follows. Section~\ref{sec:measure}
+describes more precisely the measurement process. Our solution based on the
+least square method and the implementation on FPGA is presented in
+Section~\ref{sec:solus}. Experimentations are described in
+Section~\ref{sec:results}. Finally a conclusion and some perspectives are
+presented.
+
+
+
%% quelques ref commentées sur les calculs basés sur l'interférométrie
\section{Measurement principles}
\subsubsection{Comparison}
-\subsection{VDHL design paradigms}
+\subsection{VHDL design paradigms}
-\subsection{VDHL implementation}
+\subsection{VHDL implementation}
\section{Experimental results}
\label{sec:results}
