A hybrid polymer-glass achromatic microlens array fabricated by compression molding

This paper presents the feasibility of creating a hybrid polymer-glass achromatic microlens array by compression molding. This affordable and high precision microlens array design has potential applications in the optical industry for its capability of correcting chromatic aberration. In this research a doublet design was investigated. Specifically, polycarbonate and P-SK57 glass were selected as the equivalents of flint and crown glass for their opposite dispersion properties. Ultraprecision diamond machining was utilized to manufacture the mold with an asymmetric pattern. The optical quality in the mold surface was obtained without post-machining-polishing. Both the glass and polymer microlens arrays were fabricated by thermal compression molding at different forming temperatures. After the glass microlens array was molded, it was used as the top mold half for polymer compression molding. Two chisel-shaped cavities were fabricated simultaneously when the glass lens array mold was machined. These two cavities were used as fiducial marks for assembling the P-SK57 glass part and the polycarbonate part during the second molding action. The single uninterrupted operation was developed in this study to create both optical surfaces and the fiducial marks such that high assembly tolerance could be achieved. Furthermore, numerical simulation for compression molding was conducted to study the geometry profile error of the microlens. Finally, the geometry and optical measurements were performed to demonstrate the effectiveness of the hybrid polymer-glass achromatic microlens array.