An algorithm for unwrapping noisy phase maps by means of branch cuts h
as been proposed recently. These cuts join discontinuity sources that
mark the beginning or end of a 2 pi phase discontinuity. After the pla
cement of branch cuts, the unwrapped phase map is unique and independe
nt of the unwrapping route. We show how a minimum-cost-matching graph-
theory method can be used to find the set of cuts that has the global
minimum of total cut length, in time approximately proportional to the
square of the number of sources. The method enables one to unwrap unf
iltered speckle-interferometry phase maps at higher source densities (
0.1 sources pixel(-1)) than any previous branch-cut placement algorith
m.