Compact eye camera with two-third wavelength phase-delay metalens.

Abstract

The essential role of mobile devices in modern life has driven increasing demand for compact, lightweight, and high-performance imaging systems. Recently, metalenses, which manipulate electromagnetic waves through sub-wavelength nanostructures on flat surfaces, have emerged as promising alternatives to traditional refractive lenses. However, their commercial adoption remains limited due to manufacturing challenges in defining high-aspect-ratio nanostructures, which drive up costs and reduce production yields. To address these issues, we propose an infrared metalens with a wide field of view, designed to reduce the aspect ratio of the nanostructures. Even with a limited phase modulation depth of 4π/3 which is two-thirds that of the conventional designs, we demonstrate that the height of the structures can be reduced without compromising performance. As proof of concept, we present a prototype of a compact eye imaging system based on this design method. The resulting metalens system achieves a 120-degree field of view and features an ultracompact form factor with a total track length of 1.758 mm. Such an imaging system, functioning as a compact eye camera module, enables precise extraction of eye features for gaze tracking and iris authentication, highlighting its potential for commercialization in extended reality devices.