Method for determining the condition of a roadway surface
AssigneeTZN Forschungz- und Entwicklungszentrum Unterluss GmbH
InventorsKlemens Schmitt, Walter Schaube
Life of this patent
Estimating the term…
Abstract
The condition of the roadway with respect to dryness, wetness, or icing is determined, contact-free by way of reflection measurements of light in the infrared range. The reflected light is measured selectively and simultaneously by a receiver in at least two wavelength regions with the wavelength ranges to be determined being in spectral dependence from the surface condition. Formation of a quotient of the detected signals makes possible an unequivocal statement regarding the respective condition of the roadway surface.
Claims14
Method for contact-free determination of a roadway surface condition with respect to dryness, wetness or icing, by means of measuring the reflection of light in the infrared range, comprising the steps of:
- illuminating the surface to be examined by a broadband light source;
- simultaneously measuring the reflected light in two selected wavelength ranges, with the reflected light in said selected wavelength ranges being spectrally dependent on the surface condition and providing respective signal voltages corresponding to the power received in the two wavelength ranges;
- forming a ratio of said signal voltages corresponding to the power received in the individual wavelength ranges;
- and wherein
- the two wavelength ranges are selected such that the ratio of said signal voltages for a dry surface is within a first value range, the ratio of said signal voltages for a wet surface is independent of layer thickness and lies within a second value range which is greater than said first value range, and the ratio of said signal voltages for an icy surface is at least twice said ratio of said signal voltages for a wet surface.
Apparatus for contact-free determination of roadway condition surface with respect to dryness, wetness or icing by measuring the reflection of light in the infrared range comprising broadband light source for illuminating the surface to be examined;
- receiver means for receiving and for simultaneously measuring light reflected from the roadway surface in two selected wavelength ranges in which said reflected light is spectrally dependent on the surface condition to provide respective output signal voltages corresponding to the received power in the respective wavelength ranges, with said two wavelength ranges being selected such that the ratio of said output signal voltages for a dry surface is within a first value range, the ratio of said signal voltages for a wet surface is independent of layer thickness and lies within a second value range which is greater than said first value range, and the ratio of said signal voltages for an icy surface is at least twice said ratio of said signal voltages for a wet surface;
- and
- means for forming the ratio of the signal voltages corresponding to the power received in the individual spectral ranges and for providing a corresponding output signal value as an indication of the surface condition.
Dependencies are inferred from the claim text.