Spatial-shifting cepstrum: holography without a known reference beam

We report on the spatial-shifting cepstrum (SSC), a novel digital holographic microscopy (DHM) approach that removes all constraints on both interferometric beams and eliminates the need for a predefined reference beam. This breakthrough enables conventional microscopes to perform DHM using only a minimal interferometric module, with unrestricted sample properties and field of view. Through simulations and experimental validations, we demonstrate SSC's robustness to variations in spatial shift magnitude, shift perturbations, and sample absorptiveness, while maintaining quantitative phase accuracy. In addition, we provide practical implementation guidelines, algorithmic details, and integration strategies, establishing SSC as a flexible and universal solution for DHM.