Minimising Centering Errors of Injection-Compression Moulded Plastics Lenses

The optical performance of plastics lenses depends on several quality criteria. One of the influencing factors is the alignment of the optical surfaces in relation to each other. Centering errors in the alignment of these two surfaces lead to aberrations and a lower optical performance. In spite of very precise moulds and processes, it is still not possible to avoid the occurrence of a lateral offset between the two mould halves. Thus, the offset occurs also in the optical inserts and leads to centering errors in the replicated optical components. A mould design with two integrated piezo-actuators allows the adjustment of the die-sided optical insert and with it the minimisation of the centering error in the micron-range. Therefore, it is possible to influence and reduce the geometrical error, to raise the geometrical accuracy of the lenses and with it the optical performance of plastics lenses without a further machining of the mould.