Precision moulding of optical plastic lens

Pao Yue-kong Library Electronic Theses Database

Precision moulding of optical plastic lens

 

Author: Chan, Kam-ming Erik
Title: Precision moulding of optical plastic lens
Degree: M.Sc.
Year: 1995
Subject: Plastic lenses
Injection molding of plastics
Hong Kong Polytechnic University -- Dissertations
Department: Multi-disciplinary Studies
Pages: vii, 101 leaves : ill. (some col.) ; 30 cm
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b1219795
URI: http://theses.lib.polyu.edu.hk/handle/200/1768
Abstract: Optical lenses moulded by straight injection must satisfy both optical and physical requirements. A plastic substrate of good optical property usually has poor physical characteristics such as heat resistance, impact strength and solvent resistance. Polycarbonate has high transparency and low birefringence suitable for an optical lens. However the replication of lens curvature and warpless as well as shrinkless moulded lens is very difficult to achieve through straight injection moulding process, especially when high molecular weight Polycarbonate is used to obtain a physically strong lens. Therefore, a moulding apparatus was designed to overcome the aforementioned issues which allowed the pre-enlarged lenses to be compressed to the designed final size following the completion of filling phase of the moulding cycle. Birefringence, warp and sink, replication of lens curvature, production tolerances for lens diameter, focal length were selected to evaluate the lens. Experimental results show that it is possible to make lens having low birefringence, exact replication of lens curvature and high accuracy and repeatability on lens focal length produced by using medium high molecular weight Polycarbonate and choosing the moulding conditions properly.

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