Generation mechanism and elimination method of gas trapping defect during precision glass molding for aspherical glass microlenses

Precision glass molding (PGM) technology is one of the best methods for processing optical glass lenses, but the incomplete filling in the PGM process has a negative impact on the accuracy of the fabricated aspherical glass microlenses (AGM). It is found that the main reason for this phenomenon is trapped gas between the mold and the glass preform during PGM process. This study observed the gas trapping morphology of the prepared AGM, theoretically analyzed and numerically simulated the formation of trapped gas, and developed the method of eliminating trapped gas induced filling defects. Specifically, in the molding process, the gas trapped in the molding chamber is difficult to be released. We proposed to lower the temperature of the glass and mold to make the softened glass return to the glass state, so that the gas can flow between the two surfaces to achieve the purpose of releasing the trapped gas. When the pressure gas is released, a second molding can effectively improve the filling effect. We call this process cooled down molding (CDM). Experimental results prove that CDM can effectively improve the filling rate in a short period of time and filling defects can be effectively eliminated by designing CDM molding process.