System til detektering af is eller sne på en overflade, der spejlende reflekterer lys

摘要

A method and apparatus for detecting a presence of a polarization altering substance on a specular surface includes transmitting light to the surface over a transmitting path and receiving the transmitted light from the surface and from the polarization altering substance. An intensity of the light is measured in an optical non-isolator state and in an isolator state before being compared to reference data established for the specific specular surface. The reference data are preferably established by measuring an intensity of the light in both an optical non-isolator state and in an isolator state for a known surface when the polarization altering substance is absent from the known surface.