Derivative method for fast phase imaging in simultaneous dual-wavelength off-axis phase-shifting interferometry

摘要

Dual-wavelength interferometry is one of the most effective technique in optical metrology and phase imaging by virtue of its unique advantages. In this paper, a fast derivative method for phase extraction is proposed to improve the imaging efficiency in simultaneous dual-wavelength interferometry. In this algorithm, only three off-axis wavelength-multiplexed phase-shifted interferograms are required. And only by calculating the difference between the first interferogram and other interferogram and calculating its first-order derivative, the wrapped phase of each single-wavelength can be obtained. Subsequently, the continuous phase at a synthetic wavelength can be determined freeing from the complex unwrapping procedure. Moreover, the thickness can also be obtained from the phase. Simulation results show that this method is effective and demonstrate its performance of faster computing speed and high accuracy.