  The primary goal of this thesis was the correction of
Non-Common-Path-Aberrations in the SPHERE instrument for helping it meeting its
contrast requirements. SPHERE's purpose is the search and characterization of
giant exo-planets around nearby stars. The author implemented a method called
Electric Field Conjugation that he tested in simulation as well as on the real
system. A full week was booked in SPHERE schedule a few days before the second
commissioning in June 2014. It gave the opportunity to the author to travel to
the VLT in Chile and experiment directly on the system. The contrast gain
objective of another order of magnitude in a medium-sized area has successfully
been reached bringing SPHERE raw speckle contrast from about $10^{-6}$ to
$10^{-7}$. The algorithm has therefore proven its value and will be further
investigated and hopefully automated by the SPHERE team based on the codes
developed by the author. However it is important to keep in mind that Electric
Field Conjugation is more effective for follow-up studies in order to improve
the quality of the observations. Indeed the area for a good correction is very
limited. It can't be used for exo-planets discovery unless the corrected area
is made big enough but the performance will be less.
