Visibility Range Estimation Method and System

• US 20090161914A1
• Filed: 12/21/2007
• Published: 06/25/2009
• Est. Priority Date: 12/21/2007
• Status: Active Grant

• Current Assignee: Caterpillar Incorporated
• Original Assignee: Caterpillar Incorporated
• Inventors: Song, Guobiao
• Granted Patent: US 7,970,178 B2
• Time in Patent Office: Days
• US Class Current: 382/106
• CPC Class Codes: G01N 21/538 for determining atmospheric attenuation and visibility

Abstract

The present disclosure provides methods and systems for estimating a visibility range in a visibility-degraded environment, e.g., fog. The methods and systems involve digital image processing.

Claims

1. A method for determining a visibility range of an area, comprising:

obtaining at least one digital image of at least a portion of the area;

selecting a first region of interest from the at least one digital image and calculating a visibility attenuation factor based on a contrast map and a distance map of the first region of interest;

selecting a second region of interest from the at least one digital image and selecting pixels in the second region of interest based on the visibility attenuation factor; and

finding a pixel representing the longest distance and having a contrast around or above 5%,

wherein the visibility range is determined based on the distance of the pixel.

2. The method of claim 1, wherein the digital image is obtained using a digital imaging device.

3. The method of claim 2, wherein the digital imaging device is on board of a vehicle or machine.

4. The method of claim 1, wherein the area has a substantially uniform visibility degradation.

5. The method of claim 4, wherein the visibility degradation substantially follows an exponential decrease of contrast with respect to distance of pixels.

6. The method of claim 5, wherein calculating the visibility attenuation factor includes applying a Least Square method.

7. The method of claim 1, wherein selecting a first image region and calculating the visibility attenuation factor include:

obtaining a contrast map and a distance map for a plurality of pixels in the first region of interest;

obtaining a contrast histogram of a plurality of pixels at more than one distance from the digital camera,

and selecting a plurality of bins of pixels having similar contrast histogram profiles.

8. The method of claim 1 further including communicating the determined visibility range through a user interface.

9. The method of claim 8 further including indicating the determined visibility range with a visibility line on the user interface.

10. The method of claim 1, wherein the first and second regions of interest are manually or automatically selected from the digital image.

11. A system for determining a visibility range of an area, comprising:

a processor configured to

obtain a contrast map and a distance map for a first region of interest of a digital image of at least a portion of the area;

calculate a visibility attenuation factor based on the contrast map and the distance map of the first region of interest;

select pixels from a second region of interest of the digital image based on the visibility attenuation factor; and

find a pixel representing the longest distance and having a contrast around or above 5%.

12. The system of claim 11, wherein the processor is configured to communicate the distance of the pixel representing the longest distance and having a contrast at or above 5% to an operator.

13. The system of claim 12, wherein the processor is configured to convert the distance of the pixel representing the longest distance and having a contrast around or above 5% to an operator into a visibility line on a user interface.

14. The system of claim 11, wherein the processor is configured to:

obtain a contrast histogram of a plurality of pixels in the first region of interest at more than one distance; and

select a plurality of bins of pixels having similar contrast histogram profiles.

15. The system of claim 11, wherein the processor is configured to:

apply a Least Square method to calculate the visibility attenuation factor.

16. The system of claim 11 further including a digital imaging device.

17. The system of claim 11, wherein the digital imaging device is on board of a vehicle or machine.

18. The system of claim 11 further including a user interface configured to communicate to an operator of the determined visibility range.

19. The system of claim 18, wherein the user interface includes a visibility line to communicate to an operator of the determined visibility range.

20. The system of claim 11, wherein the processor is configured to select the first region of interest and the second region of interest.