Real-Time Optical Polarization Measurement and Characterization of Submersible Windows’ Stress Under Full-Ocean-Depth Hydrostatic Pressure

Real-time monitoring the window’s stress is crucial for assessing the status and safety of submersibles working in deep sea, in which the effective measurement and characterization are desired. This work reports a measurement system to monitor submersible windows’ stress under full-ocean-depth hydrostatic pressure. A measurement setup is designed for online collecting the Mueller matrix images of 9 scaled windows on which are exerted the hydrostatic pressure maximal to 120 MPa. Subsequently, a series of characterization parameters are extracted through the analysis of polarization and texture features. The images of polarization parameters can clearly show the phenomena such as the accumulation, redistribution, and release of window’s internal stress. And some characterization parameters can steadily characterize the stress in windows during the pressurization, depressurization and creep. Further, it is found that some characterization parameters show a bit of differences among the windows, while some are sensitive to deformation but some are sensitive to stress. The scheme of this measurement system provides a way to effectively monitor the internal stress of the windows, which helps to ensure the safety of the submersibles.