Chromatic Meta‐Device for Extended‐Depth Three‐Dimensional Imaging

Achieving large axial range while maintaining high localization accuracy in three‐dimensional imaging remains challenging, especially for compact, integrated meta‐devices essential in modern sensing systems. Here, we overcome this limitation via a chromatic double‐helix (DH) metalens with a diameter of 400 µm and a numerical aperture (NA) of 0.5, which employs a dual‐encoding strategy: wavelength provides coarse axial localization, and DH point‐spread function (PSF) lobe rotation provides fine localization. Imaging a 5 µm pinhole demonstrates a continuous 650 µm axial detection range across the 480–680 nm spectrum, representing a 5.7‐fold extension over a monochromatic counterpart at 550 nm while retaining high precision. Resolving a USAF1951 target across this extended depth further validates its practical imaging capability beyond basic tracking. By integrating depth‐dependent functionalities into a single planar meta‐device, this work enables extended‐depth 3D imaging in a compact architecture and opens new possibilities for miniaturized optical systems.