  Phase retrieval is one of the most challenging processes in many
interferometry techniques. To promote the phase retrieval, Xu et. al [X. Xu, Y.
Wang, Y. Xu, W. Jin. 2016] proposed a method based on dual-wavelength
interferometry. However, the phase-difference brings large noise due to its low
sensitivity and signal-to-noise ratio (SNR). Beside, special phase shifts are
required in Xu's method. In the light of these problems, an extended
depth-range dual-wavelength phase-shifting interferometry is proposed. Firstly,
the least squares algorithm is utilized to retrieve the single-wavelength phase
from a sequence of N-frame simultaneous phase-shifting dual-wavelength
interferograms (SPSDWI) with random phase shifts. Then the phase-difference and
phase-sum are calculated from the wrapped phases of single wavelength, and the
iterative two-step temporal phase-unwrapping is introduced to unwrap the
phase-sum, which can extend the depth-range and improve the sensitivity.
Finally, the height of objects is achieved. Simulated experiments are conducted
to demonstrate the superb precision and overall performance of the proposed
method.
