An optical feedback technique is utilized for accurately determining the angular orientation of a collimator relative to an electro-optical (EO) system, and for aligning the two. A mirror assembly mounted on the EO system comprises a plurality of mirror elements positioned to receive light from the exit aperture of the collimator and to reflect the light back into the collimator through the aperture, each of the mirror elements having a reflecting surface oriented at a predetermined, unique angle. A beam of light reflected from one of the plurality of mirror elements forms a light spot on a photosensitive surface at the focal plane of the collimator. The relative orientation of the collimator and the EO system is determined by comparing the position of the light spot on the photosensitive surface with a reference position. An error signal is generated based on the comparison of the position of the light spot with the reference position, and in response to the error signal, the orientation of the collimator is adjusted relative to the EO system to align the optical axes thereof.