Extrinsic calibration method for cameras of an on-board system for formation of stereo images

An extrinsic calibration method for a first (11) and a second (12) camera of a stereoscopic system for formation of stereo images, which system is on-board a motor vehicle (1), including the following steps:

• acquiring roll, pitch and yaw stereo extrinsic and mono intrinsic calibrations for the cameras (step 31);
• acquiring successive stereoscopic images of a scene in a field of vision by reconstruction of three-dimensional images calibrated using the previous calibration step, each stereoscopic image being reconstructed from left and right images of the first and second cameras (11, 12) produced simultaneously and digitally stored as pixels (step 30);
• filtering the stereoscopic images reconstructed in this manner (step 40);
• comparing, using spatio-temporal filtering with a predetermined number of points, a profile of the scene (130;
• 13a, 13b) as observed via each reconstructed image (10) and a linear profile of the scene (120) as expected (step 50);
• establishing a yaw calibration deviation (ΔL) from the previous comparison (step 60);
• correcting the yaw calibration of the cameras (11, 12) on the basis of the deviation in yaw calibration determined by the previous step (step 61);
• and
• iterating the correction of the previous step until obtaining a zero-calibration deviation by repeating the previous steps (steps 31-61).