Abstract: Wide-angle, deep-field, close-focusing optical systems are disclosed. According to one aspect, the optical system comprises a negative lens unit and a relay lens. The negative lens unit accepts radiation from an object in space. The relay lens is coupled to the negative lens unit. The negative lens unit and the relay lens are aligned on an optical axis in that order. The negative lens units forms a first image on the relay lens to form a final image at a final image plane at a distance from the relay lens. The relay lens may comprise a zoom lens or zoom lens components, which may be movable.

Abstract: Lenses comprising first and second walls defining a cavity therebetween, which contains a fluid, are described. At least one of the walls is flexible, and the amount of fluid in the cavity can be changed to alter the shape of the at least one flexible wall, so as to alter the power of the lens. One or more flexible walls may have at least one groove formed in the wall(s) close to the periphery(ies) of the wall(s). In yet another configuration, the flexible wall and the second wall are bonded, welded, or fused together. In yet another configuration, a lens comprises a flexible wall and a second wall. The flexible wall is resilient and thinner in its central region, which is capable of being displaced relative to the second wall. Also described are methods of manufacturing a flexible wall for a lens.