Design and fabrication of multi-focal bio-inspired compound eyes with dual imaging planes

Curved microlens arrays are pivotal components of bio-inspired compound eyes due to their wide field of view and capability to track fast-moving objects. Despite their potential, fabricating curved microlens arrays remains a significant challenge. A cost-effective method for producing bio-inspired compound eyes with dual imaging planes on a steeply curved surface is proposed by using ultra-precision machining and hot embossing techniques. Individual microlenses were designed and optimized using ray-tracing methods, which provided insights through spot diagrams, point spread functions, optical path differences, and modulation transfer functions. A spherical microlens mold was created using ultra-precision milling, with its manufacturing accuracy thoroughly evaluated. The spherical microlens mold was employed to produce multi-focal bio-inspired compound eyes through hot embossing, which exhibited high fidelity and superior optical surface quality. The optical performance of these multi-focal bio-inspired compound eyes was rigorously tested on a specially designed optical platform. The experimental results confirmed a field of view angle of 60°, with spatial resolutions of 55.7 lp/mm for first-order microlenses and 35.1 lp/mm for second-order microlenses. Additionally, these results demonstrated the unique secondary imaging and focusing capabilities of the microlenses in the visible light spectrum, as well as superior performance in terms of chromatic aberration.