Microsphere-assisted common-path grating-based digital holographic microscopy

Common-path digital holographic microscopy (DHM) provides high temporal stability for high-contrast three-dimensional quantitative phase imaging. In particular, self-referencing common-path DHM, in which a portion of the object beam serves as the reference, is preferred because it enables compact setups with fewer optical elements. However, the effective field of view (FoV) is reduced, and the reference may retain residual object information. Spatial resolution is also limited by diffraction, and most proposed solutions compromise these advantages by increasing system complexity and cost. Here, we present a simplified, full-field, self-referencing DHM configuration based on a diffraction grating. A pinhole at the Fourier plane spatially filters the zero-order diffraction to generate a clean, sample-free reference beam, enabling use of the entire FoV, unlike conventional self-referencing geometries, where superposition of diffraction-order images restricts the usable area. To address spatial resolution, we demonstrate the feasibility of integrating the setup with microsphere-assisted microscopy (MAM), which has recently emerged as a simple yet effective approach for resolution enhancement. As a proof of concept, the system is validated on a standard diffraction grating, resolving features below the diffraction limit of the corresponding conventional configuration.