Fabrication of refractive and diffractive plastic micro-optical components using micro-compression molding

As the demand of the micro-optics in the field of optical data storage, optical communication, and digital display has been increased, it has become important to establish fabrication technology for plastic micro-optics, which have advantage mainly in manufacturing cost. Micromolding methods such as micro-injection molding and micro-compression molding are most suitable for mass production of plastic micro-optics with low cost. In the present study, plastic micro-optical components, such as refractive microlenses and diffractive optical elements(DOEs) with various grating patterns, were fabricated using micro-compression molding process. The mold inserts were made by ultraprecision mechanical machining, and silicon etching. A micro compression molding system was designed and developed. Polymer films and powders were used as molded materials. Various defects found during molding were analyzed, and the process was optimized experimentally by controlling the governing process parameters such as histories of mold temperature and compression pressure. Micro lenses of hemispherical shape with 153 μm radius of curvature were fabricated. The blazed and 4 stepped diffractive optical elements with 24 μm pitch and 5 μm depth were also fabricated. Optical and geometrical properties of plastic molded parts were measured by interferometric technique.