Comment on "Dual-wavelength in-line phase-shifting interferometry based   on two dc-term-suppressed intensities with a special phase shift for   quantitative phase extraction"
  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. 
Minmin Wang, Guangliang Du, Canlin Zhou, Chaorui Zhang, Shuchun Si,   Hui Li, Zhenkun Lei, YanJie Li
physics.optics