In this paper, we present a phase retrieval method where a sequence of diffraction speckle intensities, recorded by tuning
the illumination wavelength, is used. These recordings, combined with an iterative calculation method, allow the
reconstruction of the amplitude and the phase of the wavefront. The main advantages of this method are: simple optical
setup and high immunity to noise and environmental disturbance, since no reference beam or additional moving parts are
needed. Furthermore, this method allows for an extended wrap-free phase measurement range by using synthetic
wavelengths. The technique shows great potential in some fields of micro-metrology, such as lensless phase contrast
imaging and wavefront sensing.