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Abstract
Freeform optics open a new design space for optical systems. Production of freeform optics, with no axis of rotational symmetry, often requires the use of multi-axis (>2) sub aperture machining and finishing techniques. These are expensive and impede the widespread use of freeform optics. Thus, high-volume manufacturing techniques such as injection molding and precision glass molding are needed. This thesis investigates a hybrid replication technique in which a freeform corrective surface is replicated into a near-net-shape glass substrate. Because many freeform optical designs utilize optics that are nearly spherical, in this work we use an ultraviolet (UV) curable polymer to produce a freeform surface on inexpensive spherical UV transparent substrates. The process in this research proceeds as follows. A UV polymer is applied to the substrate. A freeform stamper is brought into contact with the substrate to shape the polymer. The polymer is cured by UV exposure and the stamper is removed. This work involved numerous diverse research challenges: (1) the choice of a suitable UV curable polymer and stamper combination using adhesion chemistry and empirical testing; (2) alignment of the stamper and the substrate in a UV curing chamber; (3) production and testing of a replication system including a freeform stamper; (4) testing of the replication process and associated metrology; (5) correction for shrinkage of the UV polymer during the curing process. Research indicates that the process is viable for producing near spherical freeforms with less than 1 micrometer of figure error. However, the only stamper material that repeatedly releases from the optical surface formed by the UV curable polymer has been bulk polytetrafluoroethylene (PTFE, i.e. Teflon). The cutting mechanics of this material lead to a poor surface finish on the stamper (70 nm – 100 nm Sq) and this limits the surface roughness of the replicated optical surface. Future work is required to solve this problem, possibly with diamond turnable nickel plating containing polytetrafluoroethylene.