Imaging system and method for fog detection
An imaging system and method for fog detection are disclosed herein. An imager is configured to image a scene external and forward of a controlled vehicle and to generate image data corresponding to the acquired images. A controller is configured to receive and analyze the image data. When exterior lights of the controlled vehicle are operated in a low beam state, the controller is able to detect light sources of interest in the image data, determine if each light source of interest is a foggy light or a clear light, and generate a first signal if a fog entry condition is satisfied.
1. An imaging system for fog detection, comprising:
an imager configured to image a scene external and forward of a controlled vehicle and to generate image data corresponding to the acquired images; and
a controller for analyzing the image data and configured to:
detect light sources of interest in the image data;
determine if each light source of interest is a foggy light or a clear light;
count a number of foggy lights and clear lights; and
generate a first signal if a fog entry condition is satisfied, wherein satisfaction of the fog entry condition is based on a relationship between the number of foggy lights and the number of clear lights.
2. The imaging system of claim 1 , wherein each light source of interest comprises one of a headlight, a taillight, and a streetlight, and wherein the controller is further configured to estimate a fog density based on one or more characteristics of at least one foggy light.
3. The imaging system of claim 1 , wherein the imager comprises an image sensor with a plurality of pixels coupled to a colored filter for filtering red light received from each light source of interest, and wherein the controller determines whether each light source of interest is a foggy light or a clear light based on at least one of a number of pixels detecting red light and a measured red light intensity at each pixel.
4. The imaging system of claim 1 , wherein the controller is further configured to generate a second signal if a fog exit condition is satisfied.
5. The imaging system of claim 4 , wherein satisfaction of the fog exit condition is based on an expiration of a fog exit timer.
6. The imaging system of claim 4 , wherein the first signal is used to at least one of place exterior lights of the controlled vehicle in a lower beam state and inhibit automatic high beam control of the exterior lights, and wherein the second signal is used to re-enable automatic high beam control of the exterior lights.
7. The imaging system of claim 1 , wherein based on exterior lights of the controlled vehicle operating in a high beam state, the controller is further configured to detect backscatter to determine whether the fog entry condition is satisfied.
8. The imaging system of claim 1 , wherein the fog entry condition is satisfied if at least one of a ratio and a difference between the number of foggy lights and the number of clear lights is greater than a threshold value.
9. A method of fog detection, comprising the steps of:
imaging a scene external and forward of the controlled vehicle and generating image data corresponding to the acquired images;
analyzing the image data to detect light sources of interest;
determining if each light source of interest is a foggy light or a clear light;
counting a number of foggy lights and clear lights; and
generating a first signal if a fog entry condition is satisfied, wherein satisfaction of the fog entry condition is based on a relationship between the number of foggy lights and the number of clear lights.
10. The method of claim 9 , wherein the step of determining comprises filtering red light received from each light source of interest and sensing at least one of a light spread and an intensity associated with the red light.
11. The method of claim 9 , further comprising the step of generating a second signal if a fog exit condition is satisfied, wherein the first signal is used to at least one of place exterior lights of the controlled vehicle in a lower beam state and inhibit automatic high beam control of the exterior lights, and wherein the second signal is used to re-enable automatic high beam control of the exterior lights.
12. The method of claim 9 , further comprising the step of operating the exterior lights of the controlled vehicle in a high beam state and detecting backscatter to determine whether the fog entry condition is satisfied.
13. The method of claim 9 , wherein each light source of interest comprises one of a headlight, a taillight, and a streetlight, and wherein the steps further comprise estimating a fog density based on one or more characteristics of at least one foggy light.
14. The method of claim 9 , wherein the fog entry condition is satisfied if at least one of a ratio and a difference between the number of foggy lights and the number of clear lights is greater than a threshold value.
15. A non-transitory computer-readable medium having stored thereon software instructions that, when executed by a processor, comprise the steps of:
imaging a scene external and forward of the controlled vehicle and generating image data corresponding to the acquired images;
analyzing the image data to detect light sources of interest;
determining if each light source of interest is a foggy light or a clear light;
counting a number of foggy lights and clear lights; and
generating a first signal if a fog entry condition is satisfied, wherein satisfaction of the fog entry condition is based on a relationship between the number of foggy light and the number of clear lights.
16. The non-transitory computer-readable medium of claim 15 , wherein the step of determining comprises filtering red light received from each light source of interest and sensing at least one of a light spread and an intensity associated with the red light.
17. The non-transitory computer-readable medium of claim 15 , wherein the steps further comprise generating a second signal if a fog exit condition is satisfied, wherein the first signal is used to at least one of place exterior lights of the controlled vehicle in a lower beam state and inhibit automatic high beam control of the exterior lights, and wherein the second signal is used to re-enable automatic high beam control of the exterior lights.
18. The non-transitory computer-readable medium of claim 15 , wherein the steps further comprise operating exterior lights of the controlled vehicle in a high beam state and detecting backscatter to determine whether the fog entry condition is satisfied.
19. The non-transitory computer-readable medium of claim 15 , wherein each light source of interest comprises one of a headlight, a taillight, and a streetlight, and wherein the steps further comprise estimating a fog density based on one or more characteristics of at least one foggy light.
20. The non-transitory computer-readable medium of claim 15 , wherein the fog entry condition is satisfied if at least one of a ratio and a difference between the number of foggy lights and the number of clear lights is greater than a threshold value.