| Abstract | A new technique for remotely measuring the thickness of ice on aircraft/helicopter structures (including rotors), equally suited to measurements on ground or in flight, has been used to measure glaze ice buildup on the leading edges of a NACA 0018 airfoil and rotating model helicopter rotor during icing chamber experiments. The technique incorporates a low-power focused laser beam and video camera, and can measure the directed at the ice coated surface, at any angle of incidence, and a distinctive pattern of illumination appears on the surface as a result of total internal reflection of the laser light within the ice layer. The thickness of the layer is determined from a simple expression involving only the size of the pattern, as measured from the video image, and the known refractive index of ice. Glaze ice as thin as 500µm can be measured with an accuracy of ± 0.1 mm. |
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