On the basis of the space-time Wigner distribution function, we use the lea
st-squares fitting method to derive the relationship between effective wave
front curvature matrices and second-order mixed moments of quasi-monochroma
tic and polychromatic pulsed paraxial beams. The expressions here are valid
for both completely coherent and partially coherent light in the three-dim
ensional space. Finally, the fitting method is extended to the higher-order
situation; from this, a novel technique for characterizing the beam phase
from the moments and their derivatives is presented.