Method for angle calibration of the position of a video camera on board an automotive vehicle
First Claim
1. A method of angle calibration of the position of a video camera on board an automotive vehicle, by estimation of a calibration matrix (Re) defining a rotation between a coordinate system linked to the camera (Xc, Yc, Zc) and a coordinate system linked to the vehicle (Xv, Yv, Zv), this rotation being defined as pitch (ax), yaw (ay) and roll (az) angles,the method comprising, during a phase of displacement of the vehicle on a road, the steps of:
- a) taking a sequence of video images of a scene of the road, each image of the sequence comprising a plurality of traces of interest representative of ground markings of parallels circulation lanes;
b) detecting edges (10) on the video images, to obtain a list of rectilinear edges (Dk) corresponding, in each image, to said traces of interest;
c) correcting (12) the list of edges by applying to each edge a rotation according to the estimate of the calibration matrix;
d) calculating (16) residual pitch and yaw angles by a method of detection of the vanishing point applied to the corrected list of edges obtained at step c);
e) updating (18) the estimate of the calibration matrix by applying a rotation according to the residual pitch and yaw angles calculated at step d);
the method being characterized in that it comprises the following successive steps;
f) calculating (20;
28, 32, 34, 36) a residual roll angle from the corrected list of edges obtained at step c) and the estimate of the calibration matrix obtained at step e), by;
estimating the respective widths of at least two circulation lanes based on the list of edges;
comparing the so-estimated respective widths and calculating at least one lane width difference; and
calculating the roll angle as a function the so-calculated width difference, the real widths of the lanes being supposed to be identical;
g) updating (40) the estimate of the calibration matrix by applying a rotation according to the residual roll angle calculated at step f); and
h) iterating, on at least one sequence of images, steps c) to g) until the residual pitch, yaw and roll angles are lower than a predetermined threshold.
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Abstract
The method consists in taking, when the vehicle is running, images of the road markings delimiting the circulation lanes of the road, and in fully estimating, through an iterative process, the orientation of the camera with respect to the vehicle, based on the position of two lanes located side-by-side on the image. The calibration essentially comprises: correcting the position of the lane edges in the image (10, 12); estimating the residual pitch and yaw (16); updating the rotation matrix (18); estimating the residual roll (20); updating the rotation matrix (24). These steps are iterated until the corrective angles estimated by each module are negligible (22).
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Citations
5 Claims
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1. A method of angle calibration of the position of a video camera on board an automotive vehicle, by estimation of a calibration matrix (Re) defining a rotation between a coordinate system linked to the camera (Xc, Yc, Zc) and a coordinate system linked to the vehicle (Xv, Yv, Zv), this rotation being defined as pitch (ax), yaw (ay) and roll (az) angles,
the method comprising, during a phase of displacement of the vehicle on a road, the steps of: -
a) taking a sequence of video images of a scene of the road, each image of the sequence comprising a plurality of traces of interest representative of ground markings of parallels circulation lanes; b) detecting edges (10) on the video images, to obtain a list of rectilinear edges (Dk) corresponding, in each image, to said traces of interest; c) correcting (12) the list of edges by applying to each edge a rotation according to the estimate of the calibration matrix; d) calculating (16) residual pitch and yaw angles by a method of detection of the vanishing point applied to the corrected list of edges obtained at step c); e) updating (18) the estimate of the calibration matrix by applying a rotation according to the residual pitch and yaw angles calculated at step d); the method being characterized in that it comprises the following successive steps; f) calculating (20;
28, 32, 34, 36) a residual roll angle from the corrected list of edges obtained at step c) and the estimate of the calibration matrix obtained at step e), by;estimating the respective widths of at least two circulation lanes based on the list of edges; comparing the so-estimated respective widths and calculating at least one lane width difference; and calculating the roll angle as a function the so-calculated width difference, the real widths of the lanes being supposed to be identical; g) updating (40) the estimate of the calibration matrix by applying a rotation according to the residual roll angle calculated at step f); and h) iterating, on at least one sequence of images, steps c) to g) until the residual pitch, yaw and roll angles are lower than a predetermined threshold. - View Dependent Claims (2, 3, 4, 5)
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Specification