Systems are presented with special mechanical means to switch a set of lens elements to form a compound lens from a storage position to an imaging position. In the storage mode, these arrangements offer highly efficient space saving schemes suitable for use in application where space is a premium. In the imaging mode, a plurality of lens singlets are brought together on a common imagine axis whereby they operate to form very high quality images at a single image plane. Singlet lenses are held in a lens mount device of a disk element. A plurality of similar cooperating disk elements move against adjacent coupled disks to cause well-regulated desirable motion and positioning. Specifically, portions of the disk include a cam system which permits smooth movement as disk elements are counter rotated with respect to each other thus driving the preferred positioning.