Precision UV imprinting system for parallel fabrication of large-area micro-lens arrays on non-planar surfaces

• A new vacuum-assisted UV imprinting system for precision parallel fabrication of microlens arrays on nonplanar substrates—a new low-cost platform for forming 3-dimensional micro-structures on nonplanar surfaces.
• The imprinting system precisely controls an elastomeric mold (PDMS) through pressure, which enables direct formation of large-area high quality microlens arrays onto a convex dome.
• The surface profile and roughness of the microlenses were measured (∼λ/50) and proved to be comparable with the high cost conventional precision processes, e.g., laser lithographic fabrication.
• Imaging experiments were performed to assess the resolution and large view-angle imaging capability of the micro-lens array.

This paper reports a vacuum-assisted UV imprinting system for parallel fabrication of micro-lens arrays on a spherical dome for artificial compound eye applications. Artificial compound eyes are a kind of micro-optics structure inspired by insect eyes. They offer unique optical characteristics, e.g., wide field of view (FOV), high sensitivity and light weight, in a compact arrangement with miniaturized lens arrays on a curved surface. In practice, it has been a great challenge to precisely fabricate micro-lens arrays on curved substrates at reasonable cost. The UV imprinting system was developed to ensure conformal contact between a soft elastomeric stamp and a convex substrate, i.e., dome, coated with UV-curable resins. The pressure-driven stamp enables large-area direct formation of high fill factor hexagonal micro-lens arrays through soft UV imprint processes. The geometrical characteristics, surface quality and optical properties of the micro-lens array were characterized quantitatively, e.g., NA = 0.06; RMS ∼ λ/50. Lastly, the optical performance of the artificial compound eyes was demonstrated by an ultra-wide angle imaging experiment under uniform illumination. The vacuum imprinting system presents a new manufacturing platform for fabricating 3-dimensional structures on nonplanar substrates in a parallel and cost effective way. The fabricated compound eye structure will be particularly useful in the areas of multi-channel imaging, machine vision, and surveillance.