Ice on surfaces can be detected and imaged using polarized light and polarization difference imaging. Commonly available light sources, optics, and detectors are sufficient to implement this technology
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Diffusely reflected light from an object illuminated with polarized light is partially polarized. One component (parallel) of the reflected light is more intense than the other (perpendicular). The degree that reflected light is depolarized depends on the optical properties of the surface. Reflection from a metallic object depolarizes light very little. Conversely, reflection from a highly scattering object, in which the light penetrates and undergoes multiple internal scattering before reflection (ice and snow), depolarizes light much more. As a result, subtraction or division of the two polarization components of the diffusely back-reflected light can be used to detect ice.
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