Bypassing the imaging thickness limit with a translationally-invariant nonlocal thin film.

Abstract

Conventional imaging relies on both lenses and free-space propagation. Despite recent advancements, a thickness limit was established for conventional translationally-variant imaging systems based on the nonlocality required for image formation. We bypass this limit with an imaging system composed of a single, 12.2-µm-thick dielectric film placed directly on an image sensor, eliminating both lenses and free space. By engineering nonlocal Fabry-Pérot resonances, which allows light to spread and interfere constructively across the film's surface, our multilayer film effectively assigns an individual aperture to each object point, bypassing the single-aperture assumption that dictates the thickness limit in conventional optics. We experimentally demonstrate deterministic, computation-free 2D imaging with sub-100-μm resolution. Furthermore, the system's functionality is dynamically reconfigurable; by simply tuning the illumination wavelength, we achieve depth-resolved 3D imaging and perform optical diffraction tomography to reconstruct 3D refractive index profiles. This lensless platform establishes a new paradigm for ultracompact, multifunctional optical systems with potential applications in endoscopy, machine vision, and wearable sensors.