Contactless measurement of water layer thickness on road surface - directing beam of light with limited spatial angle towards road surface and detecting back-scattered light in two near infrared wavelengths

摘要

The method of contactless measurement of the thickness of a layer (2) of water on a road surface (3) involves directing a beam of light (1) with a limited spatial angle towards the road surface and detecting the light reflected via the water layer, if present, in two wavelengths in the near infrared region. The thickness of the water layer is derived from the amplitudes (PHI lambda 1, PHI lambda 2) of the selectively detected back-scattered light flows, pref. using the equation X = lnPHI lambda 2/PHI lambda 1 / 2beta lambda 1 - beta lambda 2. The derived thickness (X) is displayed. USE/ADVANTAGE - For road safety measure. Enables contactless, predictive detection of water layers on road. Can be built into motor vehicle. Short response times over relatively large measuring distances. High immunity to stray light.