SCIENTISTS AT THE National Research Council Canada (NRC) have developed an innovative laser-based technique for detecting and measuring the thickness of ice on the external surfaces of an aircraft.

Designed by the NRC's Institute for Marine Dynamics, the method involves focusing a laser beam on a contaminated surface and then measuring the resultant "bright zone" with a camera.

When the laser beam is pointed at a frozen wing, it is reflected to form a luminous disc or zone as it re-strikes the air-ice interface. The thickness of the ice can then be determined from the diameter of this zone and the refractive index of ice.

Optical/electrical designs exist for measuring ice thickness, but the new laser system provides a remote, non-contact detector, which can distinguish between ice, snow, de-icing fluid and water. A standard video camera, fitted with a 10x zoom lens, can take accurate measurements of ice thicknesses of 0-12mm at a range of around 2m.

Source: Flight International