Visible and infrared interferometry is one of the most promising technics in the
coming years to achieve high resolution imaging in astrophysics. The equivalent
technique in radio wavelengths is providing the astrophysical community with sharp
images impossible to obtain with classical single antennas due to fundamental
diffraction limitations. At optical wavelengths, coherence of light measurements
are strongly degraded by atmospheric turbulence and may even become impossible.
A partial correction of turbulence modes can be achieved and is already producing
interesting results for imaging. Nevertheless, adaptive optics cannot compensate
for the 0-order mode of atmospheric distortion of wavefronts (the optical path
fluctuations or ``piston effect'') which causes the loss of
phase
information in
interferometry cancelling any attempt to reconstruct high resolution images.
White fringe position servoing systems (fringe trackers) make up for the optical
path fluctuations in real time and lock the system onto the white fringe to perform
low noise acquisition through long integration time, but they fail to record a
long sequence containing spectral information. The paper starts with a
presentation (Sect. 2) of interferometry and more especially Double Fourier
interferometry and explains why optical path fluctuations effects are undesirable
in interferometry. In Sect. 3 the properties of atmospheric optical
path fluctuations are listed and simulations are presented. The piston correction
method is explained in Sect. 4 and results on simulated interferograms are
presented. Section 5 is the analysis of the results.