  Laser-plasma interferograms are currently analyzed by extracting the
phase-shift map with FFT techniques (K.A.Nugent, Applied Optics {\bf 18}, 3101
(1985)). This methodology works well when interferograms are only marginally
affected by noise and reduction of fringe visibility, but it can fail in
producing accurate phase-shifts maps when dealing with low-quality images.
  In this paper we will present a novel procedure for the phase-shift map
computation which makes an extensive use of the Ridge Extraction in the
Continuous Wavelet Transform (CWT) framework. The CWT tool is {\it flexible}
because of the wide adaptability of the analyzing basis and it can be very {\it
accurate} because of the intrinsic noise reduction in the Ridge Extraction.
  A comparative analysis of the accuracy performances of the new tool and the
FFT-based one shows that the CWT-based tool phase maps are considerably less
noisy and it can better resolve local inhomogeneties.
