Pinhole-free point-diffraction dynamic phase imaging using focused white-light Sagnac interferometry

In this research, we present a convergent-beam white-light Sagnac interferometer that produces point-diffraction-like interference without a pinhole, achieving single-shot quantitative phase imaging (QPI). A sample placed at the focal plane asymmetrically modifies the counter-propagating beams, intrinsically generating a quasi-spherical reference and a sample-modulated wave. This configuration recreates the behavior of point-diffraction interferometry while preserving common-path stability, broadband compatibility, and high throughput. A Michelson-type replicator produces single-shot capture of four spatially separated interferograms with controlled 2π/3 phase shifts, captured by a color CMOS sensor; statistical analysis confirmed the green channel as the most reliable. The system successfully retrieves static and dynamic phase distributions in thin films, alcohol evaporation, and candle flames, demonstrating a robust platform for single-shot, high-sensitivity QPI of transparent samples.