Fabrication Of Precise Optical Components Using Electroforming Process And Precision Molding

Applications of precise optical components with complex shapes are becoming more popular because of demands for more accurate, smaller size optical components. Although fabrication techniques of the components have advanced in recent years, only molding based methods are typically suitable for mass production. On the other hand, molding based methods are less capable of creating complex optical components. To deal with these limitations, a process based on nickel electroforming is introduced to replicate mold inserts directly from a plastic optical component, which itself can be fabricated by any fabrication methods with high flexibility. Then, using the plated mold insert in precision compression molding, the optical components are replicated. To investigate replication capabilities of the developed method in fabrication of plastic optical components, a polymethylmethacrylate (PMMA) microlens array was replicated to a nickel-plated mold first from another plastic microlens array then mass-produced using compression molding process. Properties of both microlens arrays, were investigated for geometrical accuracy, surface quality, and optical performance. The results demonstrated a promising technique to manufacture plastic optical component with high production rates. Fabrication capabilities of the method in production of infrared optics was also evaluated through producing an infrared microlens array from a plastic microlens array. Comparison between the fabricated infrared microlens array and the plastic microlens array in terms of geometry, surface quality, and optical performance has shown that it is a promising technique for replicating infrared microlens arrays. Using the developed method, a new fabrication method of non-planar optical component with large area was also proposed and demonstrated by producing micro feature on a cylindrical surface. The technique was capable to transfer micro-optical features from a planar surface, which is much easier to produce, to non-planar surfaces. To assess possibility of fabricating complex glass optical surfaces using the developed fabrication technique, a nickel mold of diffractive harmonic diffractive lens (HDL) from a plastic HDL was made. Then, the mold and precision compression molding were used to fabricate glass harmonic diffractive lens. Geometrical analysis and optical performance of the plastic and the fabricated HDL showed that the method is capable to be used in fabrication of precision glass optics as well. Precision compression molding is one of the most suitable mass production methods of optical components with micro/nanoscale surface features. This process suffers from long heating and cooling cycles. To deal with the challenge, a novel precision compression molding was proposed. In the proposed process, induction heating of a thin nickel mold insert is used. In the process, the nickel mold insert is replicated from a plastic optical component as described before. To evaluate cooling and heating cycles of the method, a numerical model of the heating system using finite element method (FEM) was created and run in this research. According to simulation results, heating and cooling rates were significantly improved. Geometrical analysis and optical performance evaluation of the replicated microlens array have shown that the proposed fabrication method has a potential to reduce the problems of conventional bulk heating system.