All-optical edge detection in near-infrared imaging using a destructive-interference metalens

Edge detection plays a crucial role in fields of industrial inspection and medical imaging, where extraction of object contours is essential. Conventional digital approaches often require significant computational resources, increasing system complexity and power consumption. In this work, we present a metalens-based near infrared imaging system that directly performs edge extraction during imaging. By leveraging subwavelength structures to spatially manipulate the light field, the metalens acts as a compact optical differentiator, enabling real-time edge detection without the need for subsequent digital processing. The metalens has a diameter of 200 μm and a high numerical aperture (NA) of 0.7. Its fabrication complexity is reduced through a single Pancharatnam-Berry (PB) phase design. The metalens is manufactured via two-photon lithography. Both simulations and experimental results demonstrate the effectiveness of the metalens in finding edge information. This approach significantly reduces the burden on image processing and paves the way toward compact, low-power, and high-speed imaging solutions suitable for applications in near-infrared vision and automated inspection.