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Process influences and correction possibilities for high precision injection molded freeform optics

: Dick, L.; Risse, S.; Tünnermann, A.


Advanced Optical Technologies 5 (2016), Nr.4, S.277-287
ISSN: 2192-8584
ISSN: 2192-8576
Fraunhofer IOF ()

Modern injection molding processes offer a cost-efficient method for manufacturing high precision plastic optics for high volume applications. Besides form deviation of molded freeform optics, internal material stress is a relevant influencing factor for the functionality of a freeform optics in an optical system. This paper illustrates dominant influence parameters of an injection molding process relating to form deviation and internal material stress based on a freeform demonstrator geometry. Furthermore, a deterministic and efficient way for 3D mold correcting of systematic, asymmetrical shrinkage errors is shown to reach micrometer range shape accuracy at diameters up to 40 mm. In a second case, a stress-optimized parameter combination using unusual molding conditions was 3D corrected to reach high precision and low stress freeform polymer optics.