  We comment on the recent Letter by Xu and Wang et al. [Opt. Lett. 41, 2430
(2016)] in which an approach of quantitative phase extraction in
dual-wavelength in-line phase-shifting interferometry (DWILPSI) was proposed.
It is noted that a special phase shift is used, which more or less embarrasses
its practical operation. We wish to show that the same result can also be
reached by combining the generalized phase-shifting algorithm and the
least-square algorithm, in which the phase shift can be chosen randomly. In
addition to maintaining high accuracy and rapid processing speed of the DWILPSI
method, the proposed method greatly facilitates its application in actual
measurement.
