Two-step filter-free phase-shifting interferometry and its application in quantitative phase imaging of a droplet evaporation with different evaporation modes

摘要

By combining a dual-channel phase-shifting interferometry (DCPSI) system and two-step filter-free phase-shifting phase retrieval (TFPS) algorithm, we achieve the quantitative phase imaging of a regular droplet evaporation on the hydrophilic glass substrate with low contact, moreover, the relevant physical parameters including the topographic information, contact radius, contact angle, height and volume are accurately calculated under two kinds different evaporation modes (constant contact radius (CCR) and constant contact angle (CCA)). Furthermore, it is found that the proposed TFPS based DCPSI method is also suitable for the quantitative phase imaging of irregular droplet evaporation. Importantly, for random phase shifts and without filtering in advance, this TFPS based DCPSI method reveals high accuracy in phase extraction of dynamic process, and this will supply a powerful tool for the kinetic analysis during a droplet evaporation or fluid flow with micro-scale variation.