Enhancing the speed of direct volumetric imaging through annular illumination and spatial coherence of light

We propose and demonstrate a direct volumetric imaging method based on spatial coherence of light and sequential illumination from pointlike sources distributed along a ring. We prove that when the source geometry restricts illumination to high-angle modes matching the system numerical aperture, linear annular illumination achieves the same lateral resolution and similar axial sectioning as planar full-disk illumination, while offering the advantage of a threefold faster acquisition and an even lighter computational demand. The proposed approach offers a simplified and efficient alternative to conventional light-field and computational imaging, opening new paths for fast, cost-effective, real-time volumetric imaging and three-dimensional microscopy.