Nonperpendicular Incidence Induced Spatial Frequency Drift in Polarized Low-Coherence Interferometry and Its Compensation

We establish an optical path difference (OPD) distribution model in a spatial scanned polarized low-coherence interferometry (LCI) considering the nonperpendicular incidence of light to explore the spatial frequency drift. Simulation shows that the OPD is no longer linearly distributed on a charged coupled device (CCD) and that the spatial frequency drifts approximately linearly as low coherent interference fringe (LCIF) shifts. A compensation process for spatial frequency domain analysis (SFDA)-based algorithm is proposed to avoid interference-order misidentification and consequent jump error. We verified our analysis and effectiveness of the proposed algorithm with an optical fiber Fabry-Pérot pressure sensing experiment. The measured spatial frequency drift agreed well with simulation results, and the interference-order misidentification was eliminated.