Investigation on a novel in-mould microcompression system for the precision replication of microlens arrays

Abstract

As a combination of conventional injection moulding and compression moulding, injection compression moulding is expected to deliver a more uniform distribution of cavity pressure and more precise replication of surface structures. However, processing defects such as flash and design constraints such as thin edges of a product can cause non-uniform compression and imperfect geometric accuracy. The present work proposes a novel in-mould microcompression system, providing high precision compression that is in the magnitude of micrometres during the microinjection moulding process. From the perspectives of geometric accuracy, surface quality and stress birefringence, the influence of the in-mould microcompression system is examined based on conventional microinjection moulding and variotherm assisted microinjection moulding of practical microlens arrays that are designed for light-field applications. The results indicate that the in-mould microcompression can effectively enhance the replication and uniformity in terms of geometric accuracy and surface quality, and that it can marginally reduce residual stresses. As such, this constitutes an innovative solution for the precision replication of optical components.