X-Git-Url: https://bilbo.iut-bm.univ-fcomte.fr/and/gitweb/dmems12.git/blobdiff_plain/3db7a41271107989c56e4341465ecd92d7c3169b..4d2d346e47215fbef2ad2e0e1b4c3b33bb2923fa:/dmems12.tex?ds=sidebyside

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@@ -74,15 +74,75 @@
 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}.
-%% blabla +
+determine  accurately  the  deflection  with different  mechanisms. 
+In~\cite{CantiPiezzo01},   authors  used   piezoresistor  integrated   into  the
+cantilever.   Nevertheless this  approach  suffers from  the  complexity of  the
+microfabrication  process needed  to  implement the  sensor  in the  cantilever.
+In~\cite{CantiCapacitive03},  authors  have  presented an  cantilever  mechanism
+based on  capacitive sensing. This kind  of technic also  involves to instrument
+the cantiliver which result in a complex fabrication process.
+
+In this  paper our attention is focused  on a method based  on interferometry to
+measure cantilevers' displacements.  In  this method cantilevers are illuminated
+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},  the authors have  used an algorithm  based on
+spline to estimate the cantilevers' positions.
+%%RAPH : ce qui est génant c'est qu'ils ne parlent pas de spline dans ce papier...
+   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}
 \label{sec:measure}
 
+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}
 \label{sec:archi}
 %% description de l'architecture générale de l'acquisition d'images
@@ -334,9 +394,9 @@ Finally, the whole summarizes in an algorithm (called LSQ in the following) in t
 
 \subsubsection{Comparison}
 
-\subsection{VDHL design paradigms}
+\subsection{VHDL design paradigms}
 
-\subsection{VDHL implementation}
+\subsection{VHDL implementation}
 
 \section{Experimental results}
 \label{sec:results}