Low-coherence digital holographic microscope with a Fizeau interferometer.

We present a digital holographic microscope (DHM) for speckle-free quantitative imaging and depth sectioning. The proposed DHM employs an incoherent light source in an in-line Fizeau interferometer configuration with a tunable longitudinal separation between the interfering beams. This configuration enables recording fringes within the source's longitudinal coherence length, facilitating depth-sectioning capability and quantitative imaging. A polarization-phase shifting approach retrieves a quantitative speckle-free phase image from experimentally recorded interferograms. Experimental validation using smooth and rough objects demonstrates the system's performance, further supported by the perception-based image quality evaluator. The proposed DHM shows promising applications in pathological, material science, and metrology.