Radiant energy – Invisible radiant energy responsive electric signalling – Infrared responsive
Reexamination Certificate
2002-08-19
2004-07-13
Hannaher, Constantine (Department: 2878)
Radiant energy
Invisible radiant energy responsive electric signalling
Infrared responsive
C250S341300
Reexamination Certificate
active
06762409
ABSTRACT:
The invention is directed to a method for determining the thickness and growth rate of a layer of ice on structural component parts of means of transport, particularly aircraft such as airplanes, helicopters and wind-driven power stations or the like, and to a device for carrying out the method, in which the surface of a structural component part which is to be monitored and which is covered by an ice layer and/or disturbing layer is illuminated in such a way that the radiation passing through the ice layer and/or disturbing layer is measured and evaluated in different wavelength regions.
Methods and devices for carrying out the method which are known from the prior art measure the surface state of traffic routes with respect to black ice, icing and any present deicing agents and also detect ice formation and frost formation on fixed surfaces such as road surfaces in order to inform travelers of road conditions in the event of unforeseen weather situations. Icing of roadways and sudden formation of glaze ice do not present dangers only in road traffic; in rail traffic and air travel, also, iced structural component parts due to freezing water also pose a threat. Iced structural component parts on aircraft, for instance, particularly on structural component parts in the wing area which move relative to one another, lead to hindrance of air traffic and are a considerable threat to air safety; on the other hand, even a small ice formation on vulnerable structural component parts of aircraft can lead to a drastic change in the profile characteristics of the utilized structural component parts. While more and more flights can be carried out under the most adverse weather conditions thanks to modern navigation systems, e.g., radar guidance or direction-finding systems, there is also a rise in the potential risk of icing of aircraft. Particularly smaller aircraft with only simple deicing systems, or none at all, fly more and more often under weather conditions favoring icing. For example, if ice forms on the aircraft on the ground, the pilot must decide whether icing is within permissible limits or whether the ice layer should be removed before starting. Therefore, determination of the thickness of the ice and the positive or negative growth rate of a layer of ice is crucial for general flight safety as an important criterion for assessing the potential danger posed by a developing and changing layer of ice. The thickness of the ice layer is also significant for optimal use of deicing agents.
WO 96/26430 discloses a method for determining the surface state of travel routes and a device for carrying out the method in which, by means of spectroanalytic determination of water and ice on a fixed road surface in four different wavelength ranges by reflection measurement through the ice layer, the formation of ice and frost can be detected as a function of the respective degree of crystallization and the thickness of the ice layer on the surface can be taken into account. However, the different spectral shape of the absorption of the dry roadway surface is not compensated in the predetermined four wavelength ranges, so that while conclusions may be drawn concerning the surface state, accurate determination of the thickness of the ice layer is not possible.
DE 195 06 550 discloses another method for spectrometric determination of water and ice on roads and an arrangement for implementing the method by which formation of ice or frost on fixed surfaces can be determined depending on the respective degree of crystallization; but there is no compensation of the spectral shape of the reflectivity of the road surface by interfering surfaces or coating and by external light sources (daylight), so that it is impossible to determine with exactitude the thickness of the ice layer and its growth rate.
Proceeding from the prior art mentioned above, the invention has the object of providing a method for dependably determining the thickness and growth rate of an ice layer in a very accurate manner over longer time periods and a device for implementing the method which is economical and reliable and which permits the exact thickness of an ice layer as well as its growth rate to be determined in a simple manner.
In order to meet this object, the invention proposes a method by which the radiation incident on a surface covered by an ice layer and/or disturbing layer is separated spectrally by an imaging holographic grating connected with a line receiver into enough wavelengths that a correction of the ice absorption is achieved by comparing the measured radiation with a stored reflection curve of an uncoated surface and by combining the comparison values and determining the peak area in the wavelength region of the ice absorption, and wherein the thickness of the ice layer and/or disturbing layer and—by means of the ice thickness values obtained in the measurement intervals—the growth rate of the ice layer are determined and displayed.
Accordingly, the method according to the invention not only makes possible an accurate determination of the thickness of an ice layer and its growth rate, preferably on structural component parts of aircraft, but also makes it possible to detect the thickness of disturbing coverings, e.g., water, dirt and deicing agents. Further, the positive and negative growth rate of an ice layer is determined by comparison calculations from a sufficient number of determined ice thickness values, so that the ice layer thickness and its growth rate on the surface of structural component parts of aircraft can also be determined in advance for briefly changing weather conditions and climatic influences.
Due to the fact that the thickness of the ice layer and/or disturbing layer is determined on a surface to be monitored, this method can also be used not only to determine ice thickness but to detect dry layers of dirt, so that additional risk states caused by contamination of structural component parts can be eliminated by means of the method.
It is advantageously provided that the determined absorption curves can be evaluated by a simple algorithm by means of a microprocessor of the controlling and evaluating unit and a fast, accurate determination of the ice layer thickness and its growth rate is accordingly ensured using the existing technical resources in an aircraft.
The spectroanalytic measurement is preferably provided in wavelength ranges from approximately 850 to 1150 nm, wherein the light is separated spectrally into so many wavelength regions that the spectral dependency of disturbing coatings such as water, dirt and deicing agents and of different light sources such as daylight, twilight and artificial lighting can be detected and used for correcting the ice absorption.
Further, it is preferably provided that the measured values of an uncoated surface are stored in a controlling and evaluating unit as comparison values.
In addition, in order to increase measurement accuracy it is advantageously provided that the measured values from the long-wave end of the spectral region are removed from all measured values of a surface coated with an ice layer and/or disturbing layer because the light sensitivity, e.g., of a silicon receiver line, is negligibly small at that location.
Another advantage consists in that the ice thickness is determined in millimeters from the peak area which is proportional to the thickness of the ice layer by means of a conversion factor.
In addition, it is advantageously provided that the growth rate of the ice layer is determined from a large number of determined ice thickness values.
A particularly preferred further development consists in that the controlling and evaluating unit additionally issues a warning to clean the window or change the light source when the measured signal falls below a threshold in spite of the light source being switched on. In this way, additional sources of error can be eliminated from the determination of the thickness and growth rate of an ice layer.
A device for carrying out the method is preferably constructed as a spectrometer,
Correns Nico
Fritsch Manfred
Kerstan Felix
Carl Zeiss Jena GmbH
Hannaher Constantine
Moran Timothy
Reed Smith LLP
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