The generalized optical transfer function and the spectral correlation func
tion. are investigated for nonparaxial two-dimensional wave fields. The ang
le-impact marginal of the four-dimensional Wigner function is derived direc
tly. For focused wave fields of semiangle greater than 90 degrees, the spec
tral correlation function exhibits overlapping and interference. For focuse
d wave fields for which the semiangle is known to be less than 180 degrees,
the magnitude and phase can be recovered directly from knowledge of the in
tensity in the focal region. (C) 2001 Optical Society of America.