An integrated solution for mold shape modification in precision glass molding to compensate refractive index change and geometric deviation

• A scheme to compensation for both refractive index change and geometric deviation was developed.
• The approach was validated by fabricating a generic aspherical glass lens by precision glass molding.
• The molded glass lens has geometry variation less than 1.5 μm compared to uncompensated lens of 4 μm.
• PV value of wavefront of molded lens was measured about 1.0 wave, compared to the uncompensated lens of 5.4 wave.

In precision glass molding, refractive index change and geometric deviation (or curve change as often referred to in industry) occurred during molding process can result in substantial amount of aberrations. Previously, refractive index change and geometric deviation were investigated in separate studies by the authors. However, optical performance of a molded glass lens depends on both refractive index and geometry. In order to mold lenses with optimal performance, both refractive index change and geometric deviation have to be taken into consideration simultaneously and compensated. This paper presented an integrated compensation procedure for modifying molds to compensate both refractive index change and geometric deviation. Group refractive index change predicted by the finite element method simulation was used to provide a modified geometry design for a desired lens. Geometric deviations of molded glass lenses with the modified design were analyzed with a previously developed numerical simulation approach, which is used to modify the mold shape. This procedure was validated by molding a generic aspherical glass lens. Both geometry and optical measurement results confirmed that the molded lens performed as specified by the original design. It also demonstrated that finite element method assisted compensation procedure can be used to predict the final optical performance of compression molded glass components. This research provided an opportunity for optics manufacturers to achieve better performance lens while maintaining lower cost and a shorter cycle time.