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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.

The hybrid aspherical diffractive singlet achromat design can be used to reduce chromatic aberration in compact optical systems. In this paper, the development of a compression molded, low cost and high precision hybrid diffractive glass lens is described. Specifically, an aspherical diffractive lens designed to compensate for chromatic aberration was fabricated by precision glass molding. The diffractive features are integrated on the aspherical surface to avoid mold alignment during fabrication. As part of the effort to lower manufacturing cost, the diffractive profiles were directly fabricated by single-point diamond turning without polishing. A thin layer of platinum-iridium coating was applied to the mold surfaces to protect the mold inserts from degradation during the molding process. In order to reduce thermal shrinkage error, the hybrid lens was fabricated using a two-step precision molding process on a commercial glass molding machine. The geometry of the molded hybrid aspherical diffractive lens was measured using an optical profilometer and the results demonstrated a match to the design mold profile with a replication error of 0.16% in the radial direction and 6.3% in the axial direction. In addition, an optical metrology system to evaluate the diffraction efficiency and chromatic focal shift was constructed and the measured results showed that the hybrid lenses indeed function as designed.