Fabrication of Multi-Height Microlens Arrays Using Maskless Grayscale Photolithography

A microlens array (MLA) consists of micro-scale lenses arranged in a regular pattern. Traditionally, MLAs have been fabricated using methods such as thermal reflow, inkjet printing, and photolithography, finding applications in displays and cameras. Single-height MLAs, however, are limited by their narrow depth of field, necessitating for multi-height MLAs which offer multiple focal lengths.<br/>In this study, we addressed these challenges by employing a maskless grayscale photolithography system to efficiently implement multi-height MLAs. The process involved fabricating MLA molds using photoresist and then producing replica lenses with PDMS. To ensure reproducibility, multiple samples of multi-height MLAs were created. The fabrication results were validated by measuring the heights using a surface profiler and comparing the visibility of light patterns, confirming the satisfactory quality of the produced lenses.<br/>This study achieved a simplified and efficient production of multi-height MLAs using a single photolithographic step with the grayscale photolithography system, circumventing the complexities associated with traditional methods. Moreover, the use of a maskless approach maximized the fill-factor, enhancing area efficiency. The versatility of these multi-height MLAs promises significant expansions in applications such as 3D imaging, holography, and camera.