  We have developed a 3 dimensional Coherent Diffraction Imaging (CDI)
algorithm to retrieve phases of diffraction patterns of samples in Grazing
Incidence Small Angle X-ray Scattering (GISAXS) experiments. The algorithm
interprets the diffraction patterns using the Distorted-Wave Born Approximation
(DWBA) instead of the Born Approximation (BA), as in this case the existence of
a reflected beam from the substrate causes the diffraction pattern to deviate
significantly from the simple Fourier transform of the object. Detailed
computer simulations show that the algorithm works. Verification with real
experiments is planned.
