1. A system for subject ( 10 ) eye tracking on a projection surface ( 6 ) that includes: an infrared light source ( 3 ) to create reflections on the subject's eyes, two or more cameras ( 4 ) for subject's ( 10 ) head position tracking, one or more cameras ( 4 ) to track movements of the subject's ( 10 ) first eye on the projection surface ( 6 ), one or more cameras ( 4 ) to track movements of the subject's ( 10 ) second eye on the projection surface ( 6 ), a processing unit ( 7 ) configured so that it tracks the subject's ( 10 ) gazes on the projection surface ( 6 ), determines if the subject ( 10 ) focuses on a predefined sub-region or sub-regions in the projection surface ( 6 ) from the tracking of said gazes and computes the duration of said gazes, and wherein the camera ( 4 ) used to detect and determine the gaze coordinates of the first eye and the camera ( 4 ) used to detect and determine the gaze coordinates of the second eye are on a movable arm with sensors ( 2 ) to monitor the position of the cameras ( 4 ) relative to the projection surface ( 6 ).