Design fabrication and characterization of polycarbonate precision bi aspheric lens for indirect ophthalmoscopy

Abstract

Fabrication of plastic optical components by injection moulding has long been used for its lightweight, high volume and low-cost capabilities over traditional glass optics. Injection moulding is a freeform process, so that complicated geometry including aspherical, which is freeform design, may efficiently be manufactured in large volumes. However, the precision optical manufacturing industry has not readily accepted the process due to several issues related to injection moulded optics, which has slowed down the implementation of the injection moulding process in high precision application. These problems include deviation in geometry, inhomogeneous index distribution due to thermal shrinkage, birefringence, thermal instability etc. Due to the complicated rheological behaviour of polymers, the quality characteristics of injection moulded products are highly unpredictable. Conducting a comprehensive study on injection moulding, using the conventional practical approach, is very expensive and also time consuming. This research is an attempt to develop a Computer Integrated Optimization System (CIOS) for the injection moulding process, targeting high product quality as well as production efficiency. The CIOS integrates computer simulation with optimization methods and experimentation, to achieve an optimal global solution of the control parameter settings for Multiple Input and Multiple Output (MIMO) plastic injection moulding, to minimize volumetric shrinkage and warpage. This dissertation involved fundamental and systematic study for fabrication of polymer precision bi-aspheric lens by injection moulding newline