Investigations on process parameters influencing the quality of optical lenses formed by non-isothermal embossing of inorganic glasses

In this paper an advanced replication method for the production of optical components in inorganic glasses is introduced. The replication process features a non-isothermal molding procedure with short cycle time and thus reduced costs. Due to the complex thermo-mechanical behavior of the glass under non-isothermal forming conditions a detailed understanding of the process is essential for the replication of highly accurate optical components with tight tolerances. Thus the pressing process was investigated considering a certain demonstrator component to identify different stages when the gross geometry and the optical surface were formed. Then the most relevant process parameters were studied and their effects on the quality of the molded glass were quantified. It was found out that the geometrical properties, e.g. the thickness of the component is adjusted during a very short time interval after the glass contacts the mold, whereas contour and warping can be influenced for a longer time in the process. The parameters with the most significant influence on the thickness were the temperature of the glass blank and the target position of the pressing unit, whereas the duration of the glass-to-mold contact is a parameter which affects the contour of the molded component.