There is demand for small-size lens units for endoscope and industrial applications. Polished glass lenses with a diameter of 1 - 2mm exist, however plastic lenses similar in size are not commonplace. For low-cost, light-weight, and mass production, plastic lens fabrication is extremely beneficial. Especially, in the medical field, there is strong demand for disposable lens unit for endoscopes which prevent contamination due to reuse of the lens. Therefore, high mass producible and low cost becomes increasingly important. This paper reports our findings on injection-molded ultra-small size plastic lens units with a diameter of 1.3mm and total thickness of 1.4mm. We performed optical design, injection molding, and lens unit assembly for injection moldable, high imaging performance ultra-small sized lens units. We prioritize a robust product design, considering injection molding properties and lens unit assembly, with feedback from molding simulations reflected into the optical design. A mold capable of high precision lens positioning is used to fabricate the lenses and decrease the variability of the assembly. The geometric dimensions of the resulting lenses, are measured and used in the optical simulation to validate the optical performance, and a high agreement is reported. The injection molding of the lens and the assembly of the lens unit is performed with high precision, and results in high optical performance.
This paper describes the fabrication of several diverse examples of molding tools designed for high volume production of plastic and glass optical components. The examples shown demonstrate a wide combination of surface shapes and structures all with nanometer level accuracy. The tungsten carbide molding tools were produced using grinding and magnetorheological finishing (MRF), new raster fabrication, and micro-milling. Mold tools were fabricated to produce a glass free-form surface, (profile accuracy of less than 200nm in PV, surface roughness of less than Ra5nm), a radial arrangement of 188-microlens, a microscopic pin (3um in diameter, 100um in height), and a molding tool for DOE with little optical loss. The molding of glass optics requires mold materials which can be used at high temperatures. In addition to tungsten carbide this paper describes molds fabricated from nano-structural sintered material or ceramic with partially stabilized molecular structure.