Patent ID: 7557835

Claim:
A method of calibrating at least two video cameras ( 1 , 2 ) relative to each other when said two cameras constitute apparatus for stereoscopically filming ( 3 ) a portion of pathway ( 4 ) suitable for having any type of body traveling therealong, in order to detect the state of occupation of said portion of pathway, and in particular to detect incidents that might occur on said portion of pathway, the method being characterized in that it consists: in placing a plurality of marks on the surface ( 5 ) of the portion of pathway ( 4 ), said marks being distributed substantially: in ordered manner on a first group of first and second geometrical lines D 1 , D 2 meeting at a first point P 1 ; and in such a manner that given points belonging respectively to the marks having the same order relative to the first point P 1 on said first and second geometrical lines D 1 , D 2 are situated on a second group of fourth and fifth geometrical lines D 4 , D 5 meeting at a second point P 2 that does not coincide with the first point P 1 ; in forming a video image of said portion of pathway ( 4 ) including said marks, using each of the two video cameras; in defining a characteristic point P c for each image of a mark in each of the two video images; in determining first and second image lines D 1i , D 2i and fourth and fifth image lines D 4i , D 5i from said characteristic points P c ; in determining a first image meeting point for the first and second image lines D 1i , D 2i and a second image meeting point for the fourth and fifth image lines D 4i , D 5i in each of the video images; and in processing the video signals delivered by each video camera in such a manner that these signals are representative of two images suitable for being processed by stereovision.