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: Two movable groups of lenses forming a variator are controlled by means of a computer and these groups are accordingly subjected not only to the necessary displacements of each group for the progressive variations of focal length but also to a complementary longitudinal displacement for applying to the objective-lens system a focal-length multiplier coefficient having a value chosen by the operator. The device in accordance with the invention comprises a control system associated with a computer and capable of subjecting the two movable groups of lenses to a complementary longitudinal displacement in order to apply a focal length multiplier coefficient to the objective-lens system, another function of the computer being to produce the desired variation of the iris and the complementary displacements of the focusing groups in respect of each focal length. The longest possible focal length can thus be chosen as a function either of the selected numerical aperture or of the field to be covered.