System for automated determination of retroreflectivity of road signs and other reflective objects

• US 20040156531A1
• Filed: 12/15/2003
• Published: 08/12/2004
• Est. Priority Date: 06/07/2001
• Status: Active Grant

• Current Assignee: AMAC NORTH AMERICA, LLC
• Original Assignee: Facet Technology Corp.
• Inventors: Laumeyer, Robert A., Retterath, James E.
• Granted Patent: US 7,043,057 B2
• Time in Patent Office: Days
• US Class Current: 382/104
• CPC Class Codes: G01N 2021/551 Retroreflectance
• CPC Class Codes: G01N 21/55 Specular reflectivity
• CPC Class Codes: G08G 1/0962 having an indicator mounted inside the vehicle, e.g. giving voice messages
• CPC Class Codes: G08G 1/096716 where the received information does not generate an automatic action on the vehicle control
• CPC Class Codes: G08G 1/096758 where no selection takes place on the transmitted or the received information
• CPC Class Codes: G08G 1/096775 where the origin of the information is a central station
• CPC Class Codes: G08G 1/096783 where the origin of the information is a roadside individual element
• CPC Class Codes: G08G 1/096791 where the origin of the information is another vehicle

Abstract

A system for the automated determination of retroreflectivity values for reflective surfaces disposed along a roadway repeatedly illuminates an area along the roadway that includes at least one reflective surface using a strobing light source. Multiple light intensity values are measured over a field of view which includes at least a portion of the area illuminated by the light source. A computer processing system is used to identifying a portion of the light intensity values associated with a reflective surface and analyze the portion of the light intensity values to determine at least one retroreflectivity value for that reflective surface.

Claims

1. A method of automated determination of retroreflectivity values for reflective surfaces comprising:

strobing a light source to illuminate an area that includes at least one reflective surface without targeting the light source on a particular reflective surface;

collecting a plurality of light intensity measurements with at least one intensity sensor directed to cover a field of view which includes at least a portion of the area illuminated by the light source; and

using a computer processing system to;

identify a portion of at least one light intensity measurement associated with one of the at least one reflective surfaces; and

analyze the portion of the at least one light intensity measurement to determine at least one retroreflectivity value for that reflective surface.

2. The method of claim 1, further comprising:

creating a characterization profile for the light source, the characterization profile including an array of known luminance values of reflections of the light source; and

utilizing the characterization profile for the light source as part of determining the at least one retroreflectivity value for that reflective surface.

3. The method of claim 2, wherein the array of known luminance values of reflection comprises reflected intensity values for the light source over a range of colors and reflected intensity values over a range of relative angles between the light source and the reflective surface.

4. The method of claim 2, further comprising:

collecting a plurality of color images with at least one color camera directed to cover a field of view which includes at least a portion of the area illuminated by the light source; and

,

utilizing the characterization profile for the light source and the plurality of color images as part of determining the at least one retroreflectivity value for that reflective surface.

5. The method of claim 1, further comprising:

creating a characterization profile for the intensity sensor, the characterization profile including an array of intensity values of reflections measured for a known light source; and

utilizing the characterization profile for the intensity sensor as part of determining the at least one retroreflectivity value for that reflective surface.

6. The method of claim 1, wherein each light intensity measurement comprises a frame of pixel intensity values and a plurality of reflective surfaces are present in at least one of the light intensity measurements.

7. The method of claim 1, wherein the step of strobing the light source is synchronized to the step of collecting the plurality of light intensity measurements.

8. A method of automated determination of retroreflectivity values for reflective surfaces comprising:

creating a characterization profile for a light source, the characterization profile including an array of known luminance values associated with reflections of the light source;

creating a characterization profile for an intensity sensor, the characterization profile including an array of intensity values measured for reflections of a known light source; and

using the light source to illuminate an area that includes at least one reflective surface;

collecting a plurality of light intensity measurements with at least one intensity sensor without targeting a particular reflective surface;

collecting a plurality of color images with at least one color camera directed to cover a field of view which includes at least a portion of the area illuminated by the light source;

using a computer processing system to determine at least one retroreflectivity value for one of the at least one reflective surfaces that reflective surface, including;

identifying a portion of at least one light intensity measurement associated with one of the at least one reflective surfaces;

utilizing at least one of the plurality of color images to identify at least one color associated with that reflective surface;

utilizing the characterization profile of the light source and the characterization profile for the intensity sensor to determine a luminance value associated with the portion of that light intensity measurement associated with that reflective surface based on the at least one color associated with that reflective surface; and

converting the luminance value to a retroreflectivity value.

9. The method of claim 8, wherein each light intensity measurement comprises a frame of pixel intensity values and wherein the step of identifying the portion of at least one light intensity measurement is accomplished by analyzing at least one of the color images to determine the presence of a reflective surface in a portion of the color image and correlating the portion of the color image to a corresponding light intensity measurement to identify the portion of the frame of pixel intensity values associated with that reflective surface.

10. A system for automated determination of retroreflectivity values for reflective surfaces comprising:

means for repeatedly illuminating an area that includes at least one reflective surface;

means for repeatedly measuring light intensity values over a field of view which includes at least a portion of the area illuminated by the light source; and

at least one computer processing system, including;

means for identifying a portion of the light intensity values associated with one of the at least one reflective surfaces;

means for analyzing the portion of the light intensity values to determine at least one retroreflectivity value for that reflective surface; and

wherein the means for analyzing utilizes the color images as part of determining the at least retroreflectivity value for that reflective surface.

11. The system of claim 10, wherein the means for repeatedly illuminating includes a source of illumination selected from the set consisting of:

an incandescent-based source of illumination, a halogen-based source of illumination, a fluorescent-based source of illumination, high intensity discharge type source of illumination, a xenon gas-based source of illumination, a single filament sealed-beam source of illumination, light emitting diodes or a dual filament source of sealed beam illumination.

12. The system of claim 10, wherein the light intensity values are pixel intensity values and the means for repeatedly measuring light intensity values comprises a black and white camera that generates a frame of pixel intensity values.

13. A method for displaying and manipulating retroreflectivity data for a reflective surface disposed along a roadway comprising:

determining a plurality of retroreflectivity values for the reflective surface;

generating a three-dimensional representation of retroreflectivity values of the reflective surface; and

displaying the three-dimensional representation of retroreflectivity values.

14. The method of claim 13, further comprising:

generating a simulated vehicle light source and a vehicle operator/observer pair; and

for different locations of the simulated vehicle light source and said vehicle operator/observer pair, generating a simulated vehicle operator/observer observation angle and a simulated view of the vehicle pathway which includes the reflective surface.

15. The method of claim 14, further comprising:

simulating a changing magnitude of ambient lighting from a first value to a second value.

16. The method of claim 14, further wherein the three-dimensional representation of retroreflectivity values is displayed as an overlay on a depiction of the roadway.

17. The method of claim 16, further comprising:

simulating a change of at least one characteristic of the depiction of the roadway; and

determining and simulating a corresponding change in the three-dimensional representation of retroreflectivity values.

18. The method of claim 17, wherein the characteristic is selected from one or more of the set consisting of:

a location of the reflective surface, a sheeting type of the reflective surface, a location of a non-reflective surface, a location of an illuminated sign, an illumination value of an illuminated sign, an observation angle between a vehicle operator and a source of vehicle illumination, a form of precipitation between the vehicle and the reflective surface, a form of debris disposed upon the reflective surface, an angle of the reflective surface and an angle of an illuminated sign.

19. The method of claim 13, wherein generating the simulated vehicle operator/observer observation angle and the simulated view of the vehicle pathway occurs with a source of illumination selected from the set consisting of:

a high beam vehicle lighting condition, a low beam vehicle lighting condition, light emitting diodes or an auxiliary beam vehicle lighting condition.

20. The method of claim 13, further comprising:

generating a new three-dimensional depiction of the reflective surface according to a predictive aging model which includes a gradual degradation of the reflective surface over time; and

,

representing the reflective surface as if the reflective surface exhibited such a gradual degradation in the three-dimensional depiction.

21. The method of claim 20, further comprising:

associating a sheeting type to the reflective surface; and

generating an additional three-dimensional depiction of the reflective surface based in part on a predicted degradation of the associated sheeting type.

22. The method of claim 13, wherein the reflective surfaces are road signs disposed along a roadway and the step of determining the retroreflectivity values for the reflective surfaces comprises measuring at least one light intensity value of a light source reflected off each road sign and determining a retroreflectivity value in response to the light intensity value.

23. The method of claim 13, wherein at least a portion of the reflective surfaces are road signs planned to be deployed along a roadway and the step of determining the retroreflectivity values for the reflective surfaces comprises inputting retroreflectivity values for each planned road sign based on a sheeting type of the planned road sign.

24. A method for simulating a virtual drive-through that includes at least one reflective surface disposed along a roadway comprising:

determining a plurality of retroreflectivity values for each reflective surface; and

simulating a virtual drive-through along the roadway using the plurality of retroreflectivity values to simulate reflections from each reflective surface disposed along the roadway during the virtual drive-through.

25. The method of claim 24, further comprising:

simulating a change of at least one characteristic of the depiction of the roadway; and

determining and simulating a corresponding change in the reflections from each reflective surface.

26. The method of claim 24, wherein a vehicle having a light source and observer pair is simulated in the virtual drive.

27. The method of claim 26, further comprising:

simulating a change of at least one characteristic of the vehicle or light source and observer pair; and

determining and simulating a corresponding change in the reflections from each reflective surface.

28. The method of claim 24, wherein the reflective surfaces are road signs disposed along the roadway and the step of determining the retroreflectivity values for the reflective surfaces comprises measuring at least one light intensity value of a light source reflected off each road sign and determining a retroreflectivity value in response to the light intensity value.

29. The method of claim 24, wherein at least a portion of the reflective surfaces are road signs planned to be deployed along the roadway and the step of determining the retroreflectivity values for the reflective surfaces comprises inputting retroreflectivity values for each planned road sign based on a sheeting type of the planned road sign.