Determination and Comparison of Process- and Quality-Characteristics of Injection-Compression Moulded Polymer Optics

Abstract

Due to technological advantages of plastics it is increasingly possible to substitute the material glass in case of optical applications. Injection-compression moulding features a high potential particularly with regard to a production of high quality lenses made of plastics. Because of the significant volumetric shrinkage the replication of thick-walled plastics lenses is a serious challenge for the production process. By the choice of process parameters it is possible to influence the optical performance of the moulded lenses directly. The optical quality of the moulded lenses is evaluated on the basis of a Strehl-value and the geometrical accuracy on the basis of a peak-to-valley-value. It is found that the isobaric compression pressure has a significant influence on both quality values. Furthermore the process performance can be described by the abstract function of the cavity pressure. The integral underneath the curve builds a basis for an online prediction of the parts optical performance. A closed-loop process control for the injection-compression process for optimal optical performance becomes possible.