Defocus digital light processing stereolithography for rapid manufacture of microlens arrays

This study applied defocusing to digital light processing (DLP) stereolithography for the fabrication of microlens arrays (MLAs) within 1 s. We studied the effects of exposure energy, defocus distance, and a diameter adjustment algorithm to ensure printed MLAs with designed dimensions. Experiment results demonstrate that our simple fabrication method is applicable to the manufacture of various MLA designs, while achieving nanoscale surface roughness and good image quality. We determined that the height of the MLAs is proportional to the exposure energy. The highest height-to-diameter ratio achieved in this study was 0.63 (diameter = 200 mu m; height = 126 mu m). Our use of defocusing significantly reduced the average surface roughness (Ra) of the printed MLAs to 129 nm with a corresponding improvement in image resolution 45.3 lp/mm. Our use of a diameter adjustment algorithm in designing the digital mask helped preserve the dimensionality of the printed MLAs. The proposed manufacturing process was used to create a variety of MLAs with numerical apertures as high as 0.980, multiple focal lengths on a single substrate (from 21 mu m to 199 mu m), and fill factors as high as 77.98 %.

Automated summary

This study applied defocusing to digital light processing (DLP) stereolithography to fabricate microlens arrays (MLAs) within 1 s. The effects of exposure energy, defocus distance, and a diameter adjustment algorithm were investigated to achieve MLAs with desired dimensions. The results showed that the proposed fabrication method is suitable for various MLA designs, with nanoscale surface roughness and good image quality.