A Collaborative Research in Experimental Study and Numerical Simulation of Compression Molding of Precision Glass Optical Elements

Compression molding process can potentially be used to make high precision glass lenses. In a lens molding process, glass raw material is heated above its transition temperature and is subsequently pressed between the two mold halves into a lens shape. Controlled cooling (annealing) of the formed lens is then carried out with the molds in a closed position in order to enable uniform cooling of the molded lens and avoid residual stresses. Lens is eventually released at a temperature close to room temperature and finally allowed to cool to the ambient temperature. If designed correctly, this process can be easily adapted for high volume production of glass lenses especially aspherical lenses, microlenses, free-form lens and diffractive optics which are difficult to produce using conventional methods. In addition, glass molding is a net shape and an environment friendly process requiring no use of coolant and does not generate any glass debris. Compared to conventional lens making process, part to part variation can be controlled at a higher precision in glass molding and by having a multiple cavity design the process can be customized for high volume lens production. Some of the technical challenges that have prevented this process from being widely industry applicable include: 1) precise form and finish of the molds, 2) lens curve conformance and shrinkage upon cooling and 3) other process issues related to mold wear, mold life and sticking of glass to the molds at molding temperatures.