Stereo auto-calibration from structure-from-motion

1. A method for auto-calibration of stereo cameras including a first camera and second camera installable behind the windshield of a host vehicle and orientable to view the environment through the windshield, the method comprising:

during motion of the host vehicle, capturing by a processor multiple series of images respectively from the stereo cameras including a first time series of first images from the first camera and a second time series of second images from the second camera;

locating a plurality of first image points of at least one of the first images captured from the first camera at a first time;

matching at least a portion of the first image points with first image points of at least one other of the first images captured from the first camera at a second time to produce pairs of corresponding first image points respectively in the first images captured at the different times;

responsive to the motion of the host vehicle, computing world coordinates from the pairs of corresponding first image points of at least two of the first images captured at the different times from the first camera;

matching a plurality of second image points in at least one of the second images captured from the second camera so that the matching second image points correspond to at least a portion of the first image points,

using the world coordinates determined from the first camera solving for a plurality of camera parameters of the second camera.

2. The method of claim 1 , wherein the solution of the camera parameters of the second camera predicts a depth map based on stereo disparity consistent with the world coordinates computed from the first images responsive to the motion of the host vehicle.

3. The method of claim 2 , further comprising:

re-computing the camera parameters of the second camera with an initial estimate of the center of distortion of the second camera to compute further camera parameters including radial distortion parameters of the second camera.

4. The method of claim 2 , wherein said solving the camera parameters includes solving distortion parameters intrinsic to the second camera.

5. The method of claim 2 , further comprising:

performing the auto-calibration while correcting for further distortion caused by the first camera and the second camera having rolling shutters.

6. The method of claim 5 , further comprising:

using the world coordinates as the constraints which correspond to the times when the picture elements of the first and second image points are actually captured.

7. A system for auto-calibration of stereo cameras including a first camera and second camera installed behind the windshield of a host vehicle and oriented to view the environment through the windshield, and a processor connectible to the stereo cameras and operable to:

during motion of the host vehicle, capture multiple series of images respectively from the stereo cameras including a first time series of first images from the first camera and a second time series of second images from the second camera;

locate a plurality of first image points of at least one of the first images captured from the first camera at a first time;

match at least a portion of the first image points with first image points of at least one other of the first images captured from the first camera at a second time to produce pairs of corresponding first image points respectively in the first images captured at the different times;

responsive to the motion of the host vehicle, compute world coordinates from the pairs of corresponding first image points of at least two of the first images captured at the different times from the first camera;

match a plurality of second image points in at least one of the second images captured from the second camera so that the matching second image points correspond to at least a portion of the first image points using the world coordinates determined from the first camera, to solve for a plurality of camera parameters of the second camera.

8. The system of claim 7 , wherein the solution of the camera parameters of the second camera predicts a depth map based on stereo disparity consistent with the world coordinates computed from the first images responsive to the motion of the host vehicle.

9. The system of claim 8 , wherein the processor is further operable to re-compute the camera parameters of the second camera with an initial estimate of the center of distortion of the second camera to compute further camera parameters including radial distortion parameters of the second camera.

10. The system of claim 8 , wherein the camera parameters of the second camera include intrinsic distortion parameters.

11. The system of claim 8 , wherein the processor is further operable to perform the auto-calibration while correcting for further distortion caused by the first camera and the second camera having rolling shutters.

12. The system of claim 11 , wherein the world coordinates are used as constraints which correspond to the times when the picture elements of the first and second image points are actually captured.