Seat belt detection using polarimetric imaging

The implementation of automatic seat belt monitoring systems contributes to improving road safety by reducing the risks associated with road accidents. Achieving a good-performance detection system requires a solution that makes the seat belt stand out from its surrounding environment. The results of our study demonstrate that seat belts exhibit an optical polarimetric signature that differentiates them from other common textiles used in clothing. Most fabrics behave as mostly isotropic depolarizers, reducing the degree of polarization of light independently of its initial polarization state. In contrast, seat belts selectively depolarize polarized light—maintaining a higher degree of polarization when the light is linearly polarized either parallel or perpendicular to the belt axis. Our findings suggest that carefully selecting the polarization state of the illumination can enhance the separability between the seat belt and other types of fabrics, which could ultimately improve the effectiveness of automatic seat belt detection systems.