Method and apparatus for layer thickness measurement
To ensure safe aircraft and marine operations, or evaluate the integrity of structures, it is often necessary to provide accurate assessments of the presence and thickness of ice and water layers on surfaces.
Typically, this is done by non-remote, visual or tactile inspections or by using sensors. All are challenging due to the need for direct access to the surfaces. The remote measurement techniques developed to date are limited in their ability to detect rime or frosted glaze ice, or when air bubbles or grain boundaries are present. Moreover, sensors provide only a sampling of measurements in few locations, as opposed to readings of the conditions over an entire surface.
In general, all these methods require expensive equipment and processes to obtain the data needed.
There is a need for cost-effective, remote detection and measurement of a water or ice layer on a surface, regardless of the degree of transparency. Such a technology has now been developed. It facilitates the optical measurements by using readily-available equipment to measure diffuse reflections at opposite boundaries of a water or ice layer and to quantify the thickness of a layer of rime ice, glaze ice, frosted ice, or water.
This technology is available for licensing, or for further development through a collaborative research agreement with NRC. The business opportunity may be referred to by its NRC ID: 117539
This technology is of particular interest to aircraft and marine vehicle manufacturers, airport and marine ports operators and maintenance equipment manufacturers. Moreover, wind turbine manufacturers and related companies have shown interest in the technology for wind turbine icing detection.
How it works
There are a variety of techniques for transparent ice thickness measurement. Many known techniques use contact measurements by embedding emitters, sensors or other devices on surfaces. Electrical, acoustic, mechanical and optical devices have been proposed to date for contact measurements. All contact type devices have to be incorporated into or be placed in close contact with the surface with the water or ice layer to be measured. The same holds true for the electrical connections from these devices to the data logger. For this reason, contact measurement systems are expensive to install and operate. Furthermore there are critical locations like fuel tanks in wings, where sensors or emitters cannot be placed and it is challenging to obtain accurate measurements across an entire surface area if limited in the number of sensors that can be deployed.
A review of existing remote systems for ice detection and measurement reveals deficiencies in the ability to measure frosted glaze or rime ice correctly, the need to use expensive radiation, transmission and detection equipment or compromised measurements due to common inclusions like air bubbles.
The technology offered includes a method, apparatus and configuration kit for optical detection and thickness measurement of an ice or water layer on a surface. The technology uses diffuse reflections at opposite boundaries of the layer and can be used on transparent or translucent layers. The thickness of the layer is determined by computing a separation between the centres of the two diffuse reflections, and using the index of refraction of the layer and geometric properties of a beam and detector with respect to the surface. The technique can be used on solid or liquid layers to accurately quantify thickness of a layer of rime ice, glaze ice, frosted ice or water.
When used in remote configurations, the focused beam of light is projected by a laser at a distance from the surface with a conventional beam expander and focusing optics. A digital camera or diode array can be used as detection equipment with a telephoto lens for remote applications.
Remote ice and water layer measurements enabled by this technology may significantly increase accuracy and the scope of measurements that can be obtained, with the advantage of using standard equipment to significantly reduce the cost of installation and operation compared to other systems available today.
The patent has been issued in the United States
The technology provides more comprehensive and reliable remote measurements of layers of rime ice, glaze ice, frosted ice, or water on a surface. The presence and thickness of ice or water can be assessed in areas that are typically not accessible with currently used methods, e.g. near fuel tanks in wings. Using readily available equipment, the technology can significantly reduce the cost of obtaining such measurements.
- NRC file 11753: Patent issued in the US
To inquire about this technology, please contact:
Mark Murphy, Portfolio Business Advisor
NRC makes research & development licenses for this technology available under its Express Licensing program. To purchase such a license, please complete the Express Licensing order form.
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