Lane tracking system employing redundant image sensing devices
A lane tracking system for a vehicle employing redundant imaging devices with different fields of view is disclosed. The imaging devices are oriented in generally opposite directions so glare or other harsh lighting hampering one imaging device will not affect the other device. The appropriate image is selected based on image quality and used to detect lane markers and vehicle position. A preferred application for lane departure warning is also disclosed.
1. A lane tracking system adapted for use with a vehicle, comprising:
a first imaging device configured on the vehicle with an orientation and field of view so as to image a portion of the roadway in front of the vehicle;
a second imaging device configured on the vehicle with an orientation and field of view so as to image a portion of the roadway to the rear of the vehicle;
a memory storing first and second image data from the first and second imaging devices; and
a processor coupled to receive the first and second image data from the memory, the processor performing image processing of the image data comprising determining if the image quality of the first image data is at a desired level, detecting roadway lane markers and determining vehicle position using the first image data if the first image data is at or above the desired level, determining if the image quality of the second image data is at the desired level, and detecting roadway lane markers and determining vehicle position using the second image data if the first image data is below the desired level and the second image data is at or above the desired level, wherein the processor determines if the image quality of the first and second image data is at the desired level by comparing the image contrast and signal strength to desired values.
2. A lane tracking system as set out in claim 1 , wherein the processor receives the image data and performs said determining and detecting on a frame by frame basis.
3. A lane tracking system as set out in claim 1 , wherein the processor comprises a DSP.
4. A lane tracking system as set out in claim 1 , wherein the first and second imaging devices comprise CMOS imagers.
5. A lane tracking system adapted for use with a vehicle, comprising:
a first imaging device configured on the vehicle with an orientation and field of view so as to image a portion of the roadway in front of the vehicle;
a second imaging device configured on the vehicle with an orientation and field of view so as to image a portion of the roadway to the rear of the vehicle;
a memory storing first and second image data from the first and second imaging devices; and
a processor coupled to receive the first and second image data from the memory, the processor performing image processing of the image data comprising determining if the image quality of the first image data is at a desired level, detecting roadway lane markers and determining vehicle position using the first image data if the first image data is at or above the desired level, determining if the image quality of the second image data is at the desired level, and detecting roadway lane markers and determining vehicle position using the second image data if the first image data is below the desired level and the second image data is at or above the desired level, and wherein the processor performs additional comparison processing of the first and second image data if the image quality of both the first and second image data is below the desired level, the additional comparison processing comprising comparing the vehicle position based on the first and second image data to determine if they are the same within an acceptable margin of error.
6. A lane tracking system as set out in claim 5 , wherein the additional comparison processing further comprises normalizing the vehicle positions prior to comparing the vehicle positions.
7. A lane tracking system as set out in claim 6 , wherein the processing to normalize the vehicle positions comprises adjusting the vehicle position due to different position and orientation of the first and second imaging devices.
8. A lane tracking system as set out in claim 6 , wherein the processing to normalize the vehicle positions comprises adjusting the vehicle position due to motion of the vehicle.
9. A lane tracking system adapted for use with a vehicle, comprising:
a first imaging device configured on the vehicle with an orientation and field of view so as to image a portion of the roadway in front of the vehicle;
a second imaging device configured on the vehicle with an orientation and field of view so as to image a portion of the roadway to the rear of the vehicle;
a memory storing first and second image data from the first and second imaging devices; and
a processor coupled to receive the first and second image data from the memory, the processor performing image processing of the image data comprising determining if the image quality of the first image data is at a desired level, detecting roadway lane markers and determining vehicle position using the first image data if the first image data is at or above the desired level, determining if the image quality of the second image data is at the desired level, and detecting roadway lane markers and determining vehicle position using the second image data if the first image data is below the desired level and the second image data is at or above the desired level, and wherein the processor performs additional comparison processing of the first and second image data if the image quality of both the first and second image data is below the desired level, the additional comparison processing comprising performing a weighting of the vehicle positions based on the first and second image data and signal quality of the first and second image data to determine if a vehicle position may be confirmed.
10. A lane tracking system as set out in claim 1 , wherein the first and second imaging device have a common optical axis and an opposite orientation.
11. A lane departure warning system adapted for use with a vehicle, comprising:
a first imaging device configured on the vehicle with an orientation and field of view so as to image a portion of the roadway in front of the vehicle;
a second imaging device configured on the vehicle with an orientation and field of view so as to image a portion of the roadway to the rear of the vehicle;
a memory storing first and second image data from the first and second imaging devices;
means for receiving the first and second image data from the memory, and determining vehicle distance from a lane boundary using either the first or second image data based on the signal quality of the first image data and the second image data;
means for comparing the vehicle distance from the lane boundary, determined using the first or second image data, to a minimum value and issuing a warning signal if the vehicle distance from the lane boundary falls below a minimum value, wherein the means for comparing employs vehicle velocity information derived from the position information from plural frames of image data to determine time to lane boundary crossing and employs said time to lane boundary crossing to determine if the vehicle distance from the lane boundary falls below a minimum value; and
a warning device providing a warning to the vehicle operator in response to the warning signal.
12. A lane departure warning system as set out in claim 11 , wherein the warning device comprises a display.
13. A lane departure warning system as set out in claim 11 , wherein the warning device comprises a sound generator.
14. A method for detecting vehicle position relative to roadway lane markers, comprising:
acquiring first image data from a first field of view including a first portion of the roadway;
acquiring second image data from a second field of view oriented generally opposite to the first field of view and including a second portion of the roadway;
determining image quality of the first and second image data by determining signal strength and contrast of the first and second image data; and
detecting lane markers and determining vehicle position relative to the lane markers using the first image data or the second image data based on the quality of the image data.
15. A method for detecting vehicle position relative to roadway lane markers, as set out in claim 14 , wherein the first field of view is oriented toward the front of the vehicle and the second field of view is oriented toward the rear of the vehicle.
16. A method for detecting vehicle position relative to roadway lane markers, as set out in claim 14 , further comprising detecting if the vehicle distance falls within a minimum distance from a lane boundary and issuing a lane departure warning in response to such detection.