Physical pupil manipulation for speckle reduction in digital holographic microscopy.

The reduction of speckle noise by physically changing the pupil of the imaging system, as first envisioned in optical holography, is experimentally applied to a digital holographic microscope (DHM). The imaging pupil of a DHM, operating in image plane telecentric-afocal architecture, is changed in a controlled way between successive recordings, allowing the shooting of multiple partially-decorrelated holograms. Averaging the numerically reconstructed holograms yields amplitude and/or phase images with reduced speckle noise. Experimental results of biological specimens and a phase-only resolution test show the feasibility to recover micron-sized features in images with reduced speckle noise.