Ok,
I worked about my project and i maded my calculation using a triangulation of my stereo cameras.
For this i setted up my camera into matlab using 2 "cameraParameters" and a "stereoParameters"
Using that, i studied the function "triangulate" using 2 matched points matrix of the same frame, and my object stereoParameters". I have some results i can't verify for the moment, but it seems to be the right approch to get the distance between each frames.
I hope it can helps someone :)