Precision glass molding technology for XY polynomial freeform optical elements with simulations and experiments

Precision glass molding (PGM) technology, as an effective method for mass-producing glass lenses, is relatively mature in the molding process of aspheric lenses, but the glass molding technology for freeform optical elements is still in its infancy. For freeform optical elements, processing by conventional ultra-precision methods requires multiple processes and the resulting costs are high, while processing by PGM is efficient and inexpensive. Therefore, this paper investigates the molding technology of freeform lenses, the pre-compensation model of the freeform mold core is established, and predicts the residual stresses of freeform lenses after molding by the finite element method. Three different process parameters, molding temperature, molding rate and molding force, are verified. Experimental and simulation results show that the trends of residual stresses for the three process parameters are consistent. The optimal process parameters of the molding process are determined, under which the PV value of the molding lens is around 1.5µm. The experimental results show that the PV value of the molded lens is reduced to less than 1µm after using the pre-compensated mold core, which proves the validity of the pre-compensated model.