Abstract: The mirror comprises a multilayer structure, at least one of the component layers of which is made from a piezoelectric material, and electrodes for applying voltage to the multilayer structure. A free face of the multilayer structure carries the reflecting surface of the mirror. At least one of the outer faces of the mirror comprises at least one zone of curvature which is non-zero in the non-excited state of the multilayer structure.

Abstract: The optical device comprises at least two optical elements (M.sub.1, M.sub.2 ; L.sub.1, L.sub.2, L.sub.3 ; L.sub.1, M.sub.2) which are of variable focal length and include multilayer structures, at least one source of voltage (47) for the multilayer structures and electronic control means for controlling the voltage applied to the respective multilayer structures of the optical elements of variable focal length as a function of the magnification desired for the optical device.

Abstract: The optical element comprises a first bimorph structure, at least one of the components of which is made from piezoelectric material and supply electrodes for the bimorph structure. The element further comprises at least one reinforcing piezoelectric bimorph structure provided with supply electrodes. The latter are respectively connected to the electrodes of the first bimorph structure. An element of the reinforcing bimorph structure is placed against a corresponding element of the first bimorph structure and fixed thereto by a layer of an elastic material. The latter has a tensile strength which is low relative to that of the elements constituting the bimorph structures of piezoelectric material.

Abstract: It comprises a container made at least partly from a transparent material and filled with an index adapting medium. At least one of the walls of the container through which the optical axis of the system extends comprises a piezoelectric multilayer structure for modifying the curvature of the wall in accordance with the voltage applied to the multilayer structure.