Phase Unwrapping ◾ 283
One specic type of residue pair is the so-called localized phase-noise-
generated dipole residue. ese pairs are caused by the random uc-
tuation of phase because of noise, which results in the wrapped phase
gradient exceeding π. In this type of dipole, the residues tend to lie very
close together, oen within a single pixel, this makes this type of residue
relatively easy to spot and isolate.
e second kind of residue is the dipole residue, which results from
undersampling of the phase distribution. ese residues are generated by
the violation of Shannon’s sampling theory, for which the phase is not
represented with sucient spatial resolution to correctly represent the
contiguous phase. is results in spatial undersa ...