The present invention relates to a method for measuring the angular position of a contrasting edge of an object having a luminance transition zone which is substantially rectilinear in a given direction and separates two regions of different luminances. This method comprises the functional steps of: - carrying out, in a transverse direction different from the given direction, an amplitude modulation of the signals delivered by a first and a second optical sensor; and - calculating an output signal (Y out (t)) starting from the signals delivered by the first and the second optical sensors (D 1 , D 2 ) as a function of the angular position of the luminance transition zone. Device and set of devices for measuring the angular position of a contrasting edge and steering aid system for fixation and tracking a target comprising at least one such contrasting edge.