Abstract: A process for correcting optical aberration of a lens by depositing a coating on at least one of the face of the lens. The process varies a composition of the coating depending on its thickness, using at least two optical materials having different refractive indices and dispersion indices, the mutual proportions of which are varied during the deposition. Further, the coating is shaped in order to give it the shape of a lens. Such a process may find particular application in the manufacture of objectives.

Abstract: In a system for tracking a target which is illuminated by a laser beam, for example, apparatus is required to determine how far the target is off-axis. The apparatus includes an objective lens (3) which concentrates light coming from the target onto a reception surface (8). A group (12) of bundles (13,14,15,16) of optical wave guides is disposed between the reception surface (8) and a single photoelectric receiver (21). Each bundle conveys light from a respective portion of the reception surface. The bundles (13,14,15,16) of wave guides are of different lengths. Thus, the optical signals transmitted by the various bundles are received successively by the single receiver. This avoids problems of matching the sensitivity of different receivers responsive to different portions of the reception surface.