Process for determining the condition of a road surface and system for implementing the process
First Claim
1. A process for determining the condition of a road surface, comprising:
- beaming light onto the road surface;
dividing backscattered light from the road surface into spectral components;
analyzing the spectral components of the backscattered light to obtain a spectral analysis; and
determining a condition of the road surface with respect to a presence of at least one of water and ice, based on the analysis of the spectral components of the backscattered light;
wherein said analyzing step includesarranging a wavelength-dependent plot of a backscatter intensity for the spectral analysis of the backscattered light as a product of a function having free parameters which represents a wavelength-dependent backscatter light spectrum of a dry road surface, and an exponential absorption term which describes a light transmission of a water layer having a defined thickness; and
calculating the free parameters via actual measured values to obtain an optimum approximation value;
and wherein the condition of the road surface is determined based on the approximation value.
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Accused Products
Abstract
In a process and apparatus for determining the condition of a road surface, light backscattered from a road surface is divided into spectral components and the spectral intensity distribution of the backscattered light is analyzed. The wavelength-dependent backscattered light spectrum of a dry road surface is arranged with a mathematical function with free parameters. This function is multiplied by an exponential absorption term which describes the light transmission of a water layer of a defined thickness in order to obtain a mathematical function for the wavelength-dependent distribution of the backscatter intensity (as it impinges on the receiver). Using the actual measured values, the free parameters of the function can then be calculated to obtain a best possible approximation. This among other things, results in a determination of the thickness of the water layer. In order to implement the process, the system is a spectrometer which uses an absorbing element applied directly to a CCD sensor line in place of a dispersive element.
19 Citations
22 Claims
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1. A process for determining the condition of a road surface, comprising:
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beaming light onto the road surface; dividing backscattered light from the road surface into spectral components; analyzing the spectral components of the backscattered light to obtain a spectral analysis; and determining a condition of the road surface with respect to a presence of at least one of water and ice, based on the analysis of the spectral components of the backscattered light; wherein said analyzing step includes arranging a wavelength-dependent plot of a backscatter intensity for the spectral analysis of the backscattered light as a product of a function having free parameters which represents a wavelength-dependent backscatter light spectrum of a dry road surface, and an exponential absorption term which describes a light transmission of a water layer having a defined thickness; and calculating the free parameters via actual measured values to obtain an optimum approximation value; and wherein the condition of the road surface is determined based on the approximation value. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A process for determining the condition of a road surface, said process comprising:
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scattering light onto the road surface; detecting light backscattered from the road surface with photo detectors having respective different spectral sensitivities; determining a condition of the road surface with respect to a presence of at least one of water and ice, based on analysis of measuring signals representative of respective light intensity values Ii detected by said detectors with different spectral sensitivities; wherein said analysis of measuring signals includes converting each light intensity Ii ; representing each converted light intensity Ii, as an integral of a wavelength with a production function of the spectral sensitivity Ei (λ
) of an associated photodetector and the wavelength-dependent backscatter intensity S(λ
), for analysis by the detectors;arranging a wavelength-dependent backscatter intensity S(λ
) as a product of a function having free parameters which represents a wavelength-dependent backscatter light spectrum of a dry road surface, and an exponential absorption term which defines a light transmission of a water layer having a defined thickness; andcalculating the free parameters via actual measured values to obtain an optimum approximation value; and wherein the condition of the road surface is determined based on the approximation value. - View Dependent Claims (9, 10, 11, 12)
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13. An apparatus for analyzing light, comprising:
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a receiver unit having a plurality of detectors for measuring backscattered light; and a plurality of filters, the spectral sensitivity of the detectors differing based upon the plurality of filters;
whereinthe detectors are pixels of a sensor line; the filters are absorption filters having bodies which are made from a material selected from the group consisting of glass and plastic; an absorption characteristic of said absorption filters depends on a thickness of the absorption filters; the absorption filters are combined to form an absorption line filter which is disposed in a light passage direction in front of the sensor line and whose thickness varies such that one filter thickness and thus one spectral sensitivity is assigned to each pixel. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21)
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22. An apparatus for analyzing light, comprising:
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a receiver unit having a plurality of detectors, the detectors having differing spectral sensitivities; a sensor line having disposed therein the plurality of detectors; and an absorption filter, comprising at least one of glass bodies and plastic bodies, whose absorption characteristic depends on a thickness of the absorption filters; wherein the absorption filters are combined to form an absorption line filter disposed in a light passage direction in front of the sensor line and whose thickness varies such that one filter thickness and thus one spectral sensitivity is assigned to each detector.
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Specification