Quality improvement of collimating lens produced by precision glass molding according to performance evaluation

Precision glass molding technology is one of the most important approaches to produce optical glass lenses. However, the high fidelity and repeatability of optical performance be sometimes achieved even though the lenses meet the requirements of geometric assessments. The surface errorform errors transferred from mold surface with a complicated combination of components of different spatial-frequencies greatly influence the optical lenses performance. An optical model is built to investigate the impact of form errors with various frequencies on the optical performance of the lens. The mid-spatial frequency error is proved to be the factor that results in the most serious surrounding circle phenomenon. Based on the diffraction theory of the sinusoidal grating, numerical calculation is carried out to analyze their relationship. Experiments are conducted to validate the analysis and a mold polishing procedure is provided as a method to improve the quality of lenses according to performance evaluation.